Forensic Engineering 2022: Elevating Forensic Engineering

Hail impact can damage roof coverings, building exteriors, and exterior equipment and appurtenances. Following a hail event, evaluations to determine the extent of hail impact distress are common. However, many buildings experience multiple hail events over their service life and, in some cases, it is necessary to delineate the extent of damage from different hail events. Weather data resources are useful to determine the dates of reported hail occurrences and the reported or estimated hail sizes in the vicinity of a given site. However, data collected during a site investigation provides valuable, site-specific information, and such an investigation is necessary to evaluate a building for damage related to hail impact. Determination of damages caused by a specific hail event (or events) requires even more extensive site investigation. This paper discusses data collection and site investigation methodologies utilized to determine the date of occurrence for hail impact damage. Case studies are presented to illustrate useful investigative techniques and to provide examples of data collection used to determine the date of hail occurrence.

Hail impact evaluations of multi-ply bituminous roofing membranes such as built-up roofing (BUR) membranes, often include laboratory testing of field-procured membrane samples. Such testing is performed to further evaluate the samples for distress present within the membrane cross section. Popular tests performed by forensic laboratories in the United States include delamination, wherein a sample’s individual plies are separated for observation with interply bitumen still present, and desaturation, wherein all bitumen is dissolved from a sample so the bare felt reinforcement mat can be directly evaluated. This paper addresses the potential shortcomings of using desaturation testing alone when evaluating roof membrane samples for hail impact distress, as distress or other conditions can be found in the bitumen that is not identifiable after the bitumen has dissolved. As the bitumen is the waterproofing element of the membrane, identification of bitumen damages and conditions is an important part of any evaluation that is missed from desaturation alone. This paper presents the findings from multiple roof membrane samples that were subjected to discrete impact forces, similar to hailstone impacts, and then examined by both delamination and desaturation. It is shown that distress to the bitumen may exist at impacted locations, without distress being identifiable on the reinforcing mats after desaturation. This testing is also supplemented with discussion of actual conditions found in delaminated membrane samples from actual hail-damage investigations. The potential for the mistaken identification of “false positives” for impact distress when evaluating desaturated felts is also discussed.

Assessing hail damage to concrete tile shingles can be difficult as the difference between footfall, hail impact, and other phenomena is not always clear. Further, during insurance claims the lower right hand corner breaks are often the subject of dispute as to whether or not they were caused by hail impact, thermal movement, or ice build up. This paper presents a brief literature review on hail damage to concrete tile shingles including discussion on the possibility of thermal expansion/contraction causing damage to lower right hand corners. Inspection methods are discussed and an analytical method is presented along with a case study in which the analytical method is utilized.

There are numerous reasons why a single ply roof system may develop blisters over the service life of a roof: insufficient adhesive, damaged insulation, water infiltration, or other causes. But when does a blister become so large that it is in danger of advancing during periods of high wind? This paper explores how an investigator may evaluate a blister or localized area of damage in a single ply system to determine if it is at risk of progressing into a blow-off condition. Single ply membranes resist the advancement of blisters though a combination of tensile resistance and peel strength of the membrane from the substrate. As the blister gets larger, the angle of membrane peel increases, resulting in a non-linear decrease in the resistance to failure. When the peel strength of the blister perimeter length is exceeded by the applied wind load, the blister can advance to catastrophic failure.

Rehabilitation of commercial roofs is often accomplished by overlaying existing roof coverings with new single-ply membranes. In preparation for this type of recovering, evaluation of the subject building’s existing structural system, and analysis of the new roof system’s drainage characteristics by properly licensed design professionals, are usually necessary. Often, such evaluation and analysis are also required by municipal authorities having jurisdiction over construction activities to ensure the adequacy of the new systems, their compatibility with the existing structure, and their conformance to applicable building codes. In recent years, and in separate occurrences, operators of a galleria in Oklahoma and a joint retail and service facility in North Texas retained contractors to overlay the existing roofs at the respective buildings with single-ply roof membrane systems. In the months following each reroofing, a portion of each building’s roof collapsed during rainfall events. The objective of this paper is to explain the authors’ investigation of the causes of these two collapses, with the ultimate goal of providing a memorable reminder to those involved in future recovering projects. The entire investigative process is discussed, from initial site evaluation to determination of causation, including structural analysis and the associated calculation of estimated rainwater loading through iterative flow modeling. The two investigations revealed remarkably similar failures, each characterized by accumulated rainwater on the roofs that overloaded the structural framing; both accumulations having occurred due to inadequacy of the roof drainage systems.

The case study involves an industrial building that was constructed in the early 2000s with a low-sloped, mechanically fastened, single-ply membrane roofing system, with parapet walls that transitioned to mansard roofs with standing-seam metal panels. An expansion was performed adjacent to the building in 2014 that added a pitched roof along the interface that penetrated an existing parapet wall and mansard roof assembly. Additionally, changes to the operation of the building were made that required a regulated internal humidity level of 45% (relative humidity) with a frequent air exchange rate. Within 4 years post construction, the roofing membrane was noted to be billowing and sections of the membrane had become unbonded from the parapet wall. Further investigation revealed that the mechanical roof connectors were severely corroded and failing throughout with significant moisture present indicating a large-scale issue. Analysis of the building was performed which identified significant hygrothermal issues. The findings of this investigation initiated a complex design and repair to the existing building.

Roof collapses are often catastrophic events, with the potential to devastate property and to endanger the life and safety of building occupants. A common cause of catastrophic roof collapses is inadequate roof drainage and a resulting accumulation of rainwater that exceeds the capacity of the underlying framing. While numerous factors can contribute to inadequate roof drainage, the authors have observed that roof collapses can frequently be traced back to deficient drainage design or the lack of secondary drainage. Secondary drainage considerations are of particular interest because building codes have regressed and no longer directly require that secondary drainage be added to existing structures upon the replacement of the roof system. This paper discusses the authors’ experiences regarding roof collapses caused by inadequate roof drainage. Case studies are utilized to illustrate the implications of inadequate roof drainage and the shortcomings of current building code requirements. Case studies are also presented that indicate the chilling potential for future roof collapses.

Installation of PV arrays on existing roofs and/or façades imposes additional loading onto buildings with implications for the performance of the gravity and lateral structural systems. For solar projects that begin with a feasibility assessment, it is recommended to perform a field investigation followed by structural evaluation. The field investigation typically includes visual observations, non-destructive testing (NDT), such as ground penetrating radar (GPR), and/or destructive exploration. The structural evaluation includes performing calculations to determine the loading and capacity of the existing gravity and lateral structural systems to support the additional PV loading. Best practices for documenting existing structural information from limited field investigations are presented. Methods for performing feasibility-level structural evaluations are outlined. Case studies are presented to illustrate the feasibility assessment procedure considering two different existing buildings. The general procedure is shown to effectively allow for the determination of the feasibility of PV array installation using a combination of strategic field investigation and structural evaluation.

Diverse issues can manifest as undesirable deflections or slopes in buildings. Determining the cause of the deflection is important to understanding if it is merely an undesirable condition or a symptom of a more concerning issue. To assist in making that determination, an overview of floor and roof deflection investigations is presented to highlight limitations of code and construction practices in avoiding deflection-related problems and identify key elements of investigative approaches to determine distinct causes originating from similar reported symptoms. Causes such as indirect load paths, decay, design and construction defects, materials differences, and incompatible deflections between floors are discussed and related conditions that deserve additional attention will be identified.

Façade leaks had been ongoing for a number of years at an office building in Maryland despite previous replacement of all the perimeter sealants, installation of drip caps at the window heads, and sealing numerous cracks in the wall panels. The building façade consists of fixed windows, set flush with the exterior wall panels. The 5″ thick wall panels are comprised of precast concrete with a ¾″ thick travertine veneer. Cracks in the travertine were a concern for two reasons: water leakage through the travertine was bypassing the perimeter sealants and leaking into the building, and there was a potential for cracked travertine pieces to detach from the precast concrete backup. The Owner’s goals were to retain the existing wall panels, substantially reduce water infiltration, and improve the appearance of the crack repairs. This paper describes how digging deeper into the source of the water infiltration and understanding the Owner’s requirements resulted in a solution that addressed the problems and achieved the Owner’s goals. Investigation of the wall panels and window frames revealed that water entering cracks in the travertine travelled along the stone-concrete interface, down into the window frames, and building interior. Prototype repairs, watertesting, and adhesion tests led to a successful repair protocol that included recessing new metal flashings over the window heads, pinning the travertine, routing, and sealing cracks flush with the exterior surface, and applying a breathable coating to the wall panels.

Large stone veneer restoration projects for buildings designed and built in America’s “transitional” phase (≈1900–1950) require a clear understanding of as-built conditions even when documentation is available. Evaluation is essential in transitional construction that combines bypass veneer and load-bearing components. The cross-discipline nature of the building’s stone demands a collaborative effort to decipher, diagnose, and develop needed repairs. The design-build team used the initial investigation at the Oklahoma State Capitol to assess a variety of limestone anchorages from the original construction: stone-to-stone, stone-to-backup, and stability and erection aids. In some instances, anchors were not indicated on original documentation, while others differed significantly from the original drawings and specifications. The design-build team used explorations with non-destructive and semi-destructive evaluations in conjunction with original documentation and historical photos to develop repairs that met the project’s scope priority and budgeting guidelines.

Exposed concrete walls have become an increasingly popular architectural feature on buildings, functioning as the building structure, and weather protection as well as making an aesthetic statement. However, when concrete is left exposed to the elements, its performance, durability, and water tightness require careful consideration to prevent underperformance. Exposed concrete walls are susceptible to cracking and spalling, which result in leakage, aesthetic issues and, in some cases, structural failure. Coordination efforts between structural engineers, building owners, contractors, architects, and maintenance teams is required to achieve structural and weatherproofing performance while also achieving the desired appearance. Professionals need to consider both structural and weatherproofing design and installation practices when specifying exposed concrete walls including crack mitigation, thermal performance, and energy efficiency, structural design, detailing at openings and transitions, and long-term quality control. This paper discusses the depth of design, construction, and maintenance plans required for long-term success when specifying exposed concrete walls and other building elements. Case studies and relevant industry standards will be used to reinforce the importance of these considerations and used to develop basic guidelines for a more holistic approach to designing, constructing, and maintaining exposed concrete.

Deficiencies in masonry veneer attachment can result in sudden or premature failures. Such failures can result in safety hazards due to falling veneer, especially in areas where the veneer is overhead adjacent to common walkways or locations of ingress/egress. However, the veneer attachment is not typically visible and, therefore, attachment issues, whether they are from defects in the original veneer installation or related to deterioration over time, may not be readily apparent until a failure has occurred. This presents a challenge in the investigation of veneer attachment. Also, this paper addresses anchored masonry veneers, such as brick and natural stone, and discusses investigation methods varying from non-destructive evaluation to minimally destructive observation to localized veneer removal. Non-destructive determination of anchorage locations can be used to identify as-built deficiencies and to highlight areas for further (destructive) testing and detailed observation. Case studies which establish the validity of non-destructive wall tie location and give examples of the evaluation of deteriorated anchorages (i.e., wall tie corrosion) are presented.

The harsh environment of south Florida leaves little to no margin of error in the construction practice; in fact, the quality of execution significantly affects the performance of the building envelope. Walls, windows, doors, and roofs are the first line of protection against this environment. This article offers an overview of common factors that impact the performance of the building’s envelope in south Florida. The components that are outlined in the article include stucco covering, steel post-tensioning live ends, glass and glazing, and tiled decks. Examples of defects and failures as observed during forensic investigations in both new and existing buildings are presented. Best practices for design and construction will also be discussed.

Water intrusion from ice damming can damage the interiors of buildings. Unlike traditional roof leaks, ice damming leaks occur from a particular set of weather conditions and in specific building settings. Ice dams typically form at the bottom of roof slopes or at roof terminations when snow accumulations melt and drain to unheated roof edges where they refreeze. This can cause water to back up under the roof coverings damaging the structure beneath. This paper outlines key points in the assessment of roof leaks to determine whether they were attributable to ice damming. Hydrostatic and hydrokinetic roofing types and their susceptibility to ice damming are discussed. It indicates why hydrokinetic roofs are susceptible to water intrusion from ice damming. The constructions of the building envelope wall and roof insulation are also considered. Several case studies are reviewed to determine whether leaks were attributable to ice damming conditions or other deficiencies.

When buildings are affected by storm events, such as hail, or construction defects, it is common that finned windows need to be removed and reset. This leads to concerns about damaging the window fins and the water resistance capability of the re-installed window as well as how to properly flash the opening. This paper presents a flashing method and reports on results of mock-up tests on the removal and resetting of a finned window. Spray testing in accordance with AAMA standards was conducted. Results found that if proper care is taken, then finned windows can be removed and reset, and their water resistance is not affected.

Foundation movement has the potential to cause extensive damage to buildings and other structures. One of the most common causes of foundation movement, and specifically differential foundation movement, are expansive soils. Expansive soils can place significant stresses on foundation systems, resulting in damage to the foundation, superstructure, and additional building components. For new buildings, the challenges presented by expansive soils must be considered during project planning and pre-construction site investigation, and must be accounted for in design and during construction. This paper discusses the authors' experiences regarding foundation movement caused by expansive soils. Case studies are utilized to illustrate the destructive potential of expansive soils and the implications of failing to understand or account for this potential at a given site.

Foundation damage continues to cause millions of dollars in damage to structures across the United States. Foundation failures develop during the design, construction, and occupancy phases of a structure’s lifecycle. The direction and mechanism of foundation movement must first be determined prior to ascertaining the root cause of the failure. This determination can be difficult when both collapsible and expansive soils are present. The methods utilized to distinguish the direction of movement are presented. Once the cause of the damage is established, repair options can be evaluated. Foundation repair methodologies and constraints are discussed, including expansive soil treatment, foundation underpinning, and existing foundation modifications. A complete understanding of the cause of foundation damage and a knowledge of potential repair methods provides the best outcome for the owner.

Shallow-bearing concrete foundations on expansive soils are subject to various loading conditions, most invariably differential movement of the underlying soils. If a concrete foundation does not properly account for the effects of differential soil loading, excessive distortions can occur. Post-tensioning of concrete foundations is a popular engineering solution due to the reduction in quantity of structural members and materials required when compared to a conventionally reinforced foundation. Guidelines for the evaluation of post-tensioned concrete foundations are provided by the Texas Chapter of the American Society of Civil Engineers (ASCE) and the Post-Tensioning Institute (PTI). These guidelines include analyses techniques and limitations for foundation distortion that account for global performance of the foundation system but overlook localized conditions. The lack of localized analyses effectively ignores common performance failures observed in the field, particularly edge lift movement. Through a recent case study, this paper will discuss how industry evaluation methods neglect common localized failures. This paper will also present a proposed methodology on how to properly evaluate a post-tensioned concrete foundation, including global and localized distortion conditions.

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Reinforced concrete (RC) parking structures are typically subjected to harsher exposure conditions than other RC buildings, which causes them to deteriorate at a faster rate. The parking decks are the structural components that are the most susceptible to deterioration, because of their direct exposure to airborne salt sprays, rainwater, mixtures of water, and chemicals transported by the vehicles, groundwater, snow, deicing salts, etc. Concrete cover is traditionally the main (in some cases, the only) form of protection to corrosion for the steel reinforcement. High performance concrete mix designs and surface-applied concrete coatings are other effective means to slow down corrosion initiation and propagation. Parking structure owners and managers are often faced with the task to determine the residual useful life of their structures. Also, the paper will discuss two case studies: one dealing with a parking structure approaching the end of its service life, and the other with a new structure. In both cases, the structural condition was assessed through visual observations, nondestructive, and laboratory testing. The authors used the data gathered from the review of the original design documents, the results of the field survey, and laboratory testing to estimate the service life of the structures. The service life prediction was conducted following guidance from the American Concrete Institute (ACI) Committee 365 Report on Service Life Prediction (ACI 365.1R-17) and the fib Bulletin 34 Model for Service Life Design. In addition to the case studies, the authors discuss future trends for in-situ monitoring and analytical simulation of concrete durability.

Steel framing systems can offer an efficient structural system for use in parking structures, but there are unique considerations for garages constructed in harsh winter environments to consider during the design, construction, and maintenance of these structures to ensure successful long-term performance. Open web steel joists and composite metal deck are sometimes used in parking garages. These elements have limited cross-section thickness, and a small amount of section loss can result in a significant reduction in capacity. Typical cracking in slab surfaces in composite steel beam and concrete on metal deck slab construction will offer a pathway for water and road salts to penetrate the deck, resulting in through deck corrosion and deterioration of the supporting framing. In the assessment of in-service steel framed parking garages, care should be taken to evaluate components with limited redundancy and limited cross-section. The top surfaces of steel beams are also subject to corrosion and cannot be easily accessed for repair, necessitating wholesale removal and replacement of supported decks. Corrosion at connections can produce expansive forces which can increase the stresses in the connecting elements. At column bases and where fireproofing of steel framing is present or when embedded in asphalt, potentially corroding elements are concealed from view. This paper offers lessons learned through the investigation of failures of steel-framed parking structures located in the United States over the last 40 years that can provide insight for the design and assessment of steel-framed parking garages to ensure long-term performance and public safety.

A tailings dam is typically an earth-fill containing embankment/facility used to store the materials left over after the process of separating the valuable fraction from the uneconomic fraction of an ore. In designing a tailings dam, Cone Penetration Tests (CPTs) are being increasingly used to assess soil behaviour and the potential/susceptibility of the material to liquefaction. This paper presents CPT data interpreted by two Geologismiki software packages (CPeT-IT and CLiq) compared with interpreted laboratory test results from intact samples at specific depths and locations from a gold mining operation. Results from Consolidated Anisotropic Undrained (CAU) triaxial tests, Consolidated Isotropic Undrained (CIU) triaxial tests, and Cyclic Simple Shear (CSS) tests were compared with CPT interpreted results in terms of static and seismic liquefaction potential and soil behaviours. The results showed that the CPT interpreted results were around 10% higher than laboratory test results and were more conservative. However, the soil behaviour as defined by the compared methods was similar. This paper provides recommendations for suitable testing for designers to use in assessing liquefaction potential.

During the height of the rainy season in São Paulo, Brazil, a 97-meter-long section of an earth retaining wall of the Tamanduateí River channel failed. The failure affected an important avenue in a dense urban area, causing major traffic disturbances and decreasing the flow section of the river channel. This work details the post-failure investigation, challenged by extremely limited access to collect the necessary forensic evidence as the reconstruction of the ruptured section progressed rapidly. Based on analyses of design documentation, forensic evidence collected, and fluviometric historic data, it was concluded that the 30-year-old structure failed as a result of systematic overloading over the previous decade. Structural overload was a result of the intensification of rainfall and increased water levels in the channel during rainy seasons, and faulty storm-water drainage infrastructure adjacent to the wall, which ultimately led to complete saturation of the retained soil and wall failure. Furthermore, we contend that the evolving nature of traffic on the adjacent avenue, not considered during the design of the retaining wall, led to a gradual deterioration of the safety levels of the structure, further contributing to its failure. This case study showcases the consequences of insufficient maintenance and the need for continuous reassessment of operating conditions of infrastructure throughout its service life. It also serves as a reminder that extreme weather conditions due to climate change and lack of investment in retrofitting will contribute to higher failure rates of vital aging infrastructure.

In 2017, the City of Irving, Texas (City), developed plans to construct a new lift station along the banks of the Trinity River. A geotechnical investigation identified sandy clay soils interbedded with lenses of clean sand. Because of the depth of the lift station, the proposed design would extend below the depth of the groundwater encountered at the time of the investigation. A shoring system was required to retain both the soil and water table from the river. An internally braced sheet pile coffer dam was installed in May and June of 2018. In September of 2018, the Trinity River experienced a flood event that inundated the excavation and shoring wall system causing the failure of one side and significantly bowing the other three. Engineering Analytics, Inc. (EA) was contacted to investigate the cause of the failure. Our investigation found that the structural engineer hired to prepare the design of the shoring system had failed to use the design parameters provided by the geotechnical engineer. The structural engineer had instead interpreted field classification data from the geotechnical borings to develop his own design parameters. Ultimately, the shoring system provided was subjected to soil and water loads more than 5 times the design loads. The primary lesson learned from this case study is that all members of the design team need to use the same design parameters. Communication regarding design parameters is vital to prevent miscommunications.

A 360-ft (110-m) long steel sheet pile anchored bulkhead at a waterfront terminal in Charleston, South Carolina, underwent a sudden failure in 2012. The anchored bulkhead was originally constructed in the 1970s by the US Navy and featured, approximately, a total structure height of 72-ft (22-m) and 61-ft (19-m) long sheet piles. The failure zone extended inland from the waterfront upwards of 190-ft (58-m), and included the bulkhead and concrete relieving platform, landward stormwater drainage culverts and boxes, backfill, aggregate stockpiles, and heavy equipment. Fortunately, despite the large failure zone, there were no casualties as the terminal was in between shifts at the time of the collapse. Insurance claims and subrogation litigation ensued as a result of the failure. The author was retained by insurance interests for the terminal owner to conduct the failure analysis. The analysis included site reconnaissance soon after the failure, review of original design documents, and numerical analysis of several soil-structure profiles. The purpose of the analysis was to determine the most likely mode of failure and to identify pertinent factors of the failure. The mode of failure was determined to be a global structure-slope stability failure from excessive surcharge loads due to aggregate stockpiles behind the bulkhead. An alternative hypothesis was offered by an adverse party that sheet pile toe failure occurred due to dredging in excess of the design depth. This alternative hypothesis was excluded by numerical analysis in correlation with the known field conditions. This paper will review several challenges with investigating such a failure and will discuss several models and variables the investigators considered for the subject analysis.

Numerous in-service weathering steel overhead ancillary structures are listed in State Department of Transportation inventories, and their assessment is crucial to maintain public safety. Structural evaluation of weathering steel bridge-mount-truss overhead ancillary structures in the state of West Virginia was performed to judge their safety and longevity. Comprehensive inspection forms were developed to assess the condition of thirteen ancillary structures. While visual inspection was performed for several structural elements, ultrasonic testing was successfully employed for anchor bolts, base plates, columns, and column-to-horizontal chords connections. A rating protocol was established to evaluate both the element-level and overall-level condition. Extensive rating criteria were employed to determine the element-level condition. Normalized ratio between overall assessment scores and maximum possible overall scores were calculated. Most of the ancillary structures performed satisfactorily after more than 40 years of service and exposure to environmental conditions. Although most of these structures received a fair condition rating, some of their elements received either a poor or severe condition rating. The ancillary structures with poor-to-severe condition ratings were recommended for further assessment using failure analyses.

Too often we witness under-construction or recently built structures experience damage, collapse, and/or total loss as a result of varying causes, which require forensic investigation into the failure. Such failure investigations are warranted to identify causation, liability, and repair measures. The focus of this paper revolves around structures with drilled pier foundations that exhibited failures during or recently following construction. Our forensics investigations and analyses on these cases were similar and for purposes of discussion, have been combined. The investigations employed non-destructive and destructive testing to determine the causation of the foundation failure(s). The combination of these measures, in conjunction with review of the project documents, resulted in determination of the causes of the displacement to be a material failure of the pier on Exemplar No. 1, failure of the bearing strata on Exemplar No. 2, and inadequate foundation system design on Exemplar No. 3.

Restraining rails are commonly used on track at sharp radius curves for light rail transit (LRT) in North America. Recently, an American light rail operator found that bolts fastening restraining rail to the running rail were routinely failing after relatively short service lives. This work presents the results of analyses that were performed to determine the root cause of failure. A metallurgical investigation of the bolts was undertaken that consisted of a surface chemical analysis, visual inspection, and fractographic analysis of the fracture surface. The stress demands on the bolts were examined by performing three-dimensional nonlinear finite element analyses of the restraining rail assemblies. The results suggest that the bolts become vulnerable to high cycle fatigue after loosening. Recommendations are presented for improved performance.

Wingwalls are designed as retaining walls to avoid the sliding of the backfill soil behind the bridge abutments and roadways. Using turn-back wingwalls that are parallel to the bridge diaphragm can provide support for the parapets and minimize the total longitudinal pressure on the abutments. These walls are subjected to axial forces and bending moments due to the thermal movements, which could cause cracks in the wingwalls. The objective of this study was to examine the thermal movement behavior of a turn-back wingwall in a semi-integral abutment bridge. Vertically oriented vibrating wire strain gauges were embedded in the concrete of the wingwall. Initial data were collected from April 2017 to December 2017. After one year of service, a visual inspection was conducted, and cracks were noticed at the top of the wingwall. Additional data were collected to monitor the wingwall behavior, and additional gauges were mounted across the cracks on the front face of the wingwall to monitor the behavior of the walls and the observed vertical cracks. The cracks tended to close as the air temperature decreased and open as the air temperature increased. The maximum opening of the cracks was 351 µƐ when the air temperature was 43°C, and the maximum closing was about -133 µƐ when the air temperature was -15.5°C. These cracks may affect the long-term serviceability of this type of bridge.

The natural gas pipeline project involved construction of approximately 500 mi of pipeline through Michigan, Ohio, Pennsylvania, and West Virginia. The focus of Engineering Analytics (EA) analyses was related to the construction and installation of pipeline in southeastern Ohio. The topography in the area of the project consists of very steep, heavily vegetated slopes. During and after construction of the pipeline, numerous landslides occurred along the pipeline alignment. EA was retained to provide an opinion as to whether or not the slope failures along the pipeline construction area were a result of construction practices. EA’s scope of work involved the review of numerous failures. The landslides were broken down into two general types: construction and restoration. The construction slope failures were those that occurred during the construction process. The restoration slope failures were those that occurred after completion of construction. This paper addresses investigation and construction practices that contributed to a high number of slope failures.

Wiss, Janney, Elstner Associates (WJE) was engaged by the City of Bridgeport to perform a condition review of historic Perry Memorial Arch in preparation for a proposed restoration project. WJE performed an extensive field investigation to review the existing conditions at both the exterior and interior of the unreinforced masonry structure including a survey from an aerial lift and a small unmanned aerial system (sUAS/drone). Following the investigation of the structure, WJE used the findings to complete a structural analysis of the monument. The analysis included checks of overall stability when subjected to wind and seismic loading as well as shear and compression stress checks at the mortar joints of the masonry piers. WJE also utilized graphical methods to determine the stability of the unreinforced masonry arches. WJE’s analysis was simplified and conservative in nature with the goal of demonstrating to the client that the structure has adequate capacity to withstand the anticipated loads. Contrary to the findings of the previous engineer, WJE determined that the deterioration of the unreinforced masonry structure was caused by long-term water infiltration, saturated freeze-thaw cycling, and unaccommodated thermal movement of the masonry materials. WJE was engaged by the client to design repairs in accordance with the findings and recommendations of our analysis.

In this paper, the author presents the results of a forensic investigation at a tailings storage facility (TSF) located in San Luis Potosí, Mexico. The purpose of the study is to investigate potential seepage observed along a localized portion of the existing embankment dam. Field observations and predictive modeling of seepage and slope stability have been revisited and applied to obtain a better understanding of dam performance and to estimate the probability of failure of embankment slopes considering the existing dam configuration and a proposed dam raise. The investigation comprises visual observations, test pitting, field and laboratory tests, seepage analyses, slope stability analyses, and a review of the quality control construction data. The results suggest that the observed localized ‘damp’ portion of the embankment is non-hydrostatic. Therefore, a raise of the existing dam above the current dam configuration would be feasible provided best dam engineering practices are followed. Design considerations should focus on the location of the tailings pond. Instrumentation plans should consider monitoring of piezometric heads within the existing and new embankments, and future placement of fill materials should be in accordance with appropriate earthwork specifications.

The Pikeview Quarry is a limestone aggregate quarry located northwest of Colorado Springs, Colorado. The sedimentary units in the quarry, which contain low-strength clay-bearing seams, have been geologically uplifted by the underlying Pikes Peak Granite, resulting in steep dips toward the east (downslope). Large-scale landslides occurring in December 2008 and September 2009 led to the suspension of mining activity at the quarry. Prior to the slope failures, mining was occurring at the base of the highwall, which undercut the sedimentary beds and left the highwall unsupported. Engineering Analytics, Inc. and Telesto Solutions, Inc. were retained to determine the causes of the slope failure and the extent to which the mining practices contributed to the failures. The investigation consisted of data review, field investigations, laboratory testing, and slope stability modeling. Three-dimensional model simulations were performed to evaluate various mining scenarios including 0, 25, 50, and 100 percent excavation of the toe below the highwall. For the models with 0, 25, and 50 percent of the toe excavated, the computed displacement values were 1.6, 1.9, and 3.6 ft, respectively. In the final model with 100 percent of the toe excavated, as was the case prior to the failures, the computed displacement was 13.6 ft, which agreed well with the observed displacement into the excavation. It was concluded that the removal of too much material at the base of the highwall without removing the sedimentary rocks above it was also a cause of the landslides. A conceptual reclamation plan was developed that addressed slope stabilization, revegetation, additional mining, and long-term use.

Between July 14–16th, 2021, record rainfall and subsequent flooding resulted in the deaths of over 200 people and billions of dollars-worth of damage in Germany and Belgium. An NSF sponsored Geotechnical Extreme Events Reconnaissance (GEER) Association reconnaissance mission was undertaken by the authors to investigate the effects of flooding in Germany, Belgium, and the Netherlands. The two-week-long mission provided insight to the performance of various geostructures such as building foundations, roads, and bridges. This paper provides a summary of observations made by the US-based GEER team in collaboration with many local European colleagues. Key observations presented include a bridge case study, the impact of scour and erosion on different structures, and soil-structure interactions. A review of the data used to inform the reconnaissance mission as well as the data collection technologies used, including terrestrial LiDAR, UAV-Structure from Motion (SfM), and multispectral imagery, is also presented.

Hurricane Florence made landfall near Wrightsville Beach, North Carolina, at 7:15 am Friday, September 14, 2018, as a Category 1 hurricane. At the time of landfall, Florence had maximum sustained winds of about 90 mph. After landfall, Florence’s winds steadily weakened as it moved inland. However, over the next two days it produced record-breaking rainfall, which was over 30 in. in some North Carolina locations, including near a sprawling apartment complex outside Wilmington. The authors were tasked with determining the nature and extent of wind/water damage to the property as a result of this historic hurricane. The investigation included several site visits and in situ testing of windows to ultimately determine what water damage was due to “storm-created openings.” The window tests included spray testing, sill dam testing, and deflection testing—all of which are detailed herein. Furthermore, this paper discusses the methods used during this investigation to determine damage from wind-driven rain versus top-down water intrusion to provide advice to other design professionals.

Winds produced by tornadoes can impose extreme pressures capable of destroying or severely compromising the structural integrity of structures. Typical design wind loads can fall well below those produced by tornadoes, and as such, structural damage from tornado winds can be extensive. The intensity of the winds produces by a tornado can vary over a relatively short distance. Therefore, a significant disparity in the extent of damage affecting neighboring structures can also occur. This paper outlines key points to perform structural assessments to determine the extent of structural damage from tornadoes. It describes a systematic approach to the evaluation of structures considering the damage indicators and degrees of damage defined by the Enhanced Fujita Scale. This paper also describes basic factors to consider during the structural assessment to assist contractors and building consultants in preparing construction estimates to repair the structure, if repairability is an option. Several case studies involving tornado damage structural assessments will be discussed from tornadoes that occurred in Tennessee and Arkansas in the Spring of 2020.

Hurricane Michael was the most powerful storm to hit the Florida Panhandle when it made landfall in 2018. Teams from the Structural Extreme Event Reconnaissance (StEER) network collected over 380 damage reports of residential structures in Bay County Florida. This data were analyzed to characterize wind damage. The data indicated an increase in performance in homes built after the Florida Building Code (FBC) was introduced in 2002, with an over 50% reduction in the percentage of homes with extensive damage. Performance of individual structural components generally increased in newer homes, however, FBC revisions since 2002 do not appear to have consistently improved performance. Several factors were determined to affect performance including roof shape with failure more common in gable and complex roofs than hip roofs. The type of roof covering also affected performance where metal roofs experienced fewer overall failures, but a higher percentage of severe failure than asphalt shingles.

Hurricane Michael made landfall near Mexico Beach, FL, on October 10, 2020, as a Category 5 hurricane with peak gust wind speeds over 70 m/s. Following landfall, the authors conducted forensic investigations of twenty-three large-volume, low-rise buildings in Panama City, FL, that failed in below-design conditions. The buildings represented multiple structural systems, including pre-engineered metal buildings, precast tilt-up concrete systems, and metal rack buildings, and represented a range of years of construction. This paper describes the forensic assessments and observed failure mechanisms. It further details the load paths in three case study buildings and hypothesizes regarding the principal factors involved in the premature failures, informed by static and dynamic analysis of the structural systems through 3D, linear elastic finite element models. The analysis demonstrates the critical importance of the longitudinal load path through the end bay of the windward wall in the observed collapse mechanisms.

On August 10, 2020, a derecho windstorm occurred across several Midwestern states, including Nebraska, Iowa, Illinois, and Indiana, resulting in structural damage exceeding 750 miles in length. This event presented a unique opportunity to evaluate the performance of agricultural structures because of the unusually large area impacted in a predominantly agricultural region of the country. This study focuses on the response of steel grain bins, which are critical structures to support the agricultural industry and for which widespread damage was observed. While several factors impact the performance of steel grain bins under severe wind loads, the case study presented in this paper analyzes the performance of two common types of steel grain bins—namely, farm bins and commercial bins. The intended functions of these bins are the same, but they are marketed towards different scales of operation. In this paper, the performance of adjacent, geometrically similar farm and commercial bins is presented, which was documented through a combination of aerial imagery, structure-from-motion reconstructions, as well as manual measurements and photographs. While the farm and commercial bins were largely identical, the farm bins buckled and uplifted during the windstorm while the commercial bins were undamaged. Analysis of the bins concluded that the presence of exterior stiffeners, intended to permit larger storage sizes, provided additional resistance to wind loads.

The spate of extreme wind events in the recent past has negatively impacted building envelope components. The authors of this paper have performed numerous investigations to determine the effect of extreme winds interacting with these building envelope components, especially aluminum-framed sliding glass doors and windows. Closer examination of these doors and windows reveals conditions that are indicative of wind-induced stresses transmitting through the door and window components. During field investigations, we have frequently observed sliding glass door systems with their panel framing joints separated and/or rotated. To study the impact of extreme wind pressures on the sliding glass doors, a detailed three-dimensional finite element model of a typical aluminum-framed sliding glass door was developed. The computer model was created based on drawings available in the public domain and included both aluminum framing and glass panels. The computer analysis model incorporated nonlinear spring elements to model boundary conditions of the frame and glass and nonlinear stress-strain curves to represent the inelastic behavior of the aluminum framing subjected to wind loads. The computer model was subjected to monotonically increasing loading through nonlinear pseudo-static analysis. Results of the analysis were then compared and verified with field observations. The analysis confirmed that when the wind pressures on the sliding glass door exceed its rated design pressure capacities, panel framing joints bend out of plane and deform permanently. This was consistent with field observations of separations and flaring out of panel framing joints. Results from the finite element analysis complement field observations.

Fabric structures have found widespread use due to their light weight, ease of erection, modularity, and flexible footprint sizes. Unfortunately, these structures have been observed to fail prematurely in below-design wind events in several cases, with severe life safety and financial consequences. Despite these failures, there is little knowledge of the load paths in these structures to guide improved designs. This paper provides preliminary observations on the structural wind-induced response of fabric membrane structures obtained via structural health monitoring of an in-service fabric structure located in a coastal environment near Panama City, FL. The structure was instrumented in July 2020 with 66 individual sensors. Between August 2020 and November 2020, the instrumented structure was affected by ten windstorm events with peak 3-s gust wind speeds of at least 15 m/s. The captured data provide insights on the lateral and vertical load paths through the structure, the dynamic response of the building to high winds, and the role of wind-induced internal pressurization. This paper contextualizes these observations with respect to previously studied failures.

This paper will focus on structural failures caused by below-design wind events. The structure is flexible and behaves in ways not common to building designers. The failure mechanism in each case is atypical and not covered within the design guides or building codes. The mechanisms covered in this paper include torsional galloping, vortex-induced vibrations, and rain-wind-induced vibrations. Case studies for these mechanisms include lighting poles, bridge cables, and single-axis solar trackers. Each case study will explore the mechanism, failure modes, investigative methodology, and preventive or repair strategies. Lessons learned from these failures will enable a relatively better design of flexible structures sensitive to wind. Understanding these mechanisms will also enable the development of appropriate theories for forensic engineers.

On September 20, 2017, Puerto Rico was impacted by Hurricane Maria. The objectives of this investigation were to determine if the hurricane caused damages to pedestrian bridges and to offer suggestions on improving the resiliency of these structures. Twenty-one bridges in the San Juan metropolitan area were inspected, of which four were assessed to have wind-induced damages. The main cause of the damages was the presence of traffic signs attached to the bridges. Two steel truss pedestrian bridges experienced inelastic lateral deflections due to the wind pressure these signs transferred to the structure. On the other two, the transit signs were detached from their bottom supports, constituting a safety hazard. One of the bridges affected by inelastic lateral deflection was furthered analyzed. A detailed inspection was performed, lab tests were carried out to characterize the material, and finite element simulations were executed. It was concluded that the signs played a predominant role in the inelastic response, but there were other contributing factors. It is recommended that special considerations be taken when attaching signs to pedestrian bridges. In addition, after an extreme wind event, preliminary inspections should include any flexible elements attached to pedestrian bridges.

Non-synoptic wind phenomenon, such as tornadoes, waterspouts, thunderstorm downbursts, microbursts, and other local wind phenomenon routinely generate wind speeds and pressures strong enough to create severe damage. Due to the low probability of occurrence, current design codes still do not require all structures to be designed for tornadoes. Building envelope breach by wind-borne debris impact during storms often leads to devastating consequences for the building’s structure, envelope, and interior. Comparing the wind-borne debris regions in the ASCE 7 design wind maps with the highest tornadic gust wind speed isotach indicates that there is little overlap. Consequently, the vast majority of structures designed and built in tornado prone regions do not contain specific measures to prevent against debris strike.

In 2015, the author responded to the failure of a 3.4-million-gallon, insulated steel water tank in a remote village on Alaska’s North Slope. A significant windstorm had caused the outer layer of standing seam metal roofing to tear free of the tank, but wind speed estimates for the event were still well below expected design levels for the area, raising questions about the root cause of the failure. This paper will review the procedure and findings of the root cause investigation, including the meteorological study, failure analysis of welded connections and other components of the cladding system, structural analysis, review of the original design documents, and the challenges of conducting the field evaluation in winter conditions. Then, the authors will review past and current standards for the design of such tanks and cladding systems (both domestic and international), their role in the observed failure, and whether recent changes made to ASCE 7 starting in 2016 would have been sufficient to avoid this failure had they been in place when the tank was originally designed.

Puebla City has been affected by earthquakes, producing damage to the infrastructure. Despite this recurring experience, to date there is no reliable record of damage caused by each earthquake. A damage database is a necessary tool to determine the most seismically vulnerable areas in Puebla City. It will help to evaluate and identify the zones historically more affected. Based on the fact that seismic activity is recurrent, soil ground conditions are relatively constant in the long term, and infrastructure has low level of change in the city between events, the damage database can be developed. By creating a simple model of empirical damage prediction, the intent is to determine the most vulnerable areas in a future seismic event. This paper seeks to show the patterns of damage in buildings on Puebla City and its most vulnerable zones using damage data information and tools like GIS and statistics.

Induced earthquake activity has increased in recent years due to fracking processes in Oklahoma and neighboring states. The structural design and detailing of buildings were not governed by earthquake loads in these regions, considering only the naturally occurring seismicity. This paper presents an evaluation of earthquake damage to school buildings in Oklahoma. The investigated buildings relied on unreinforced masonry construction for lateral load resistance. Field investigation, measurements, and invasive testing revealed cracked and out-of-plumb brick and block masonry walls. Crack patterns and response modes were typical of masonry walls responding to lateral earthquake loads. Damage to interior finishes, partitions, and ceilings was also widespread. Nonlinear response history analyses of masonry walls, incorporating their ASCE 41 strength and stiffness degradation characteristics, complemented the investigation and evaluation of repairs to restore the buildings. Results of computer analyses were verified and consistent with in-plane and out-of-plane wall damage observations in the field.

The Mandaree rural water intake facility lies adjacent to a landslide on Lake Sakakawea in McKenzie County, North Dakota. In 2017, cracks appeared alongside and upslope from the facility’s booster station. Based on a geotechnical evaluation, the booster station was structurally isolated from the landslide with a buried soldier pile wall. The wall was tested in 2019 when a large portion of the landslide mass mobilized, shuttering the facility but leaving the bulk of the infrastructure unharmed. Short-term tasks included reestablishing facility access and relocating impacted discharge pipes further from the landslide perimeter. Long-term tasks include establishing more robust access and mitigating additional risks associated with physiographic changes produced by the 2019 event, remain in progress.

As civil/structural engineers in the field of forensic engineering, we are often asked to evaluate the condition of residential buildings after a vehicle impact. A vehicle impact to a residence can damage a structure in numerous ways, and the typical concerns are related to the severity and extent of damage to the structural building components as well as the resultant damage to the interior and exterior finishes. The purpose of this paper is to outline steps to characterize and describe the damage caused by a vehicle impact to a residential structure, and how to track load paths through the structure to evaluate related damage beyond the direct impact location. We will discuss the frequent situation, where the structural engineer must discern between damage caused by a vehicle impact and pre-existing damage. The paper will review inspection techniques and specific concerns related to the evaluation of key structural elements and provide some discussion on cosmetic damage related to a vehicle impact (such as cracking of veneers, cracking of interior finishes, and damage from secondary impacts). The paper will also discuss two case studies which discuss the types of damage often encountered during the assessment of buildings impacted by vehicles. The forensic civil/structural engineer should find this paper to be a good primer on the subject of building damage assessment from vehicle impacts.

This paper focuses on the technical and code aspects of fire impact on buildings and their occupants. The paper discusses different elements of protection of buildings and their occupants in fire such as fire protection of structural elements, compartmentation of fire, and egress, as per current code requirements. It aims to develop a framework that allows project stakeholders to understand current code requirements and ask the right questions regarding how these codes can impact a fire investigation. Then forensic investigation issues prior to a fire incident, such as construction issues or code interpretation for non-standard materials and constructions will be discussed. Finally, the paper includes a review of investigation issues after a fire incident. The use of different analytical approaches such as fire dynamics, computational fluid dynamics, thermal analysis, finite element analysis, and agent-based modeling of movement of people is discussed. Combining analytical tools with non-destructive and destructive testing allows for identifying different types of damage (visible and hidden, structural, architectural, MEP, smoke, and toxic residue), as well as the extent of damage and which building elements can be kept, repaired, or replaced after a fire event. These tools can also be helpful to investigate any injuries or casualties from a fire. The discussion also covers implications of repair for code upgrades. Throughout, examples from fire investigations will be used to further illustrate the points.

Wildfires cause billions of dollars’ worth of damage annually. Even when directly not consumed by fire, damage to structures have been reported and accredited to high temperature exposure and moisture content decreases resulting from a wildfire. It is difficult for insurance professionals to assess whether reported structural component or interior distress was the result of a surrounding wildfire event. A residence surrounded by a mountain wildfire in the western United States became the subject of an investigation into wildfire-related distress. The methodology utilized during this investigation is presented and detailed. Elevated exterior temperatures, and their durations, around the structure are inferred from heat damage to nearby flora, exterior building materials, etc. Heat flow analyses are conducted to determine the interior temperatures at which components were exposed. Thermal effects are modeled on a material-by-material basis to evaluate the effect of the determined temperature increase, and moisture content decrease, on distressed items reported to be wildfire-related. Although closely surrounded by a forest fire, much of the distress attributed to the wildfire was found to not be wildfire-related.

In the last several years, hot, dry winds gusting through passes and canyons have driven record-breaking wildfires through the mountainous California terrain, burning and smoke/heat damaging thousands of structures in their wake. The California “fire season” in late autumn follows a warm and dry summer only to be trailed by winter rains. Burnt hillsides offer little resistance to surface runoff, mud, and debris flows, which further strain the earth retaining systems of these hillside structures. Besides thermal damage to structural components, the effects of surface water runoff and even water used during firefighting efforts have a direct impact on the stability of hillside building pads which are frequently crafted on cut-fill lots. Earth retaining systems compromised by unexpected hydrostatic loads and surface runoff sometimes lead to differential settlement of foundations that are already supported on the variable strata of cut-fill lots. Due to governing code requirements for existing buildings, structures with substantial structural damage have to be brought in compliance with current codes and sometimes significantly higher design seismic forces than their original design. This affects the lateral load resisting structural systems including the foundation systems as well. In older structures, the foundation, earth retention systems, and even the fill soil frequently do not comply with current building code requirements. Consequently, reinstatement of fire damaged hillside structures may require extensive retrofit and reconstruction.

This paper describes both emerging and common sense approaches to managing risk for geotechnical engineering aspects of constructed facilities using preventive measures to minimize potential to become a forensic project. The process starts with the elemental, important, and collaborative “what could go wrong” question during design, identifying risks and a range of risk management strategies which could be implemented for typical geotechnical design and construction problems. Geotechnical risks include but are not limited to inaccurate settlement estimates, failures due to improper selection of soil strengths, risks associated with innovation, construction issues, and claims of differing site conditions. Risk management strategies will be presented from development of a simple risk register with contingency plans, to sophisticated methods of assessing risk and confidence in certain predictions of ground behavior. The paper will review the emerging trend of voluntary and regulatory-required geotechnical peer review and a few lessons learned from example projects where design phase risk management could have improved outcomes. Recommendations for common sense practice for any project will be presented.

Most engineering investigations follow a few basic steps: Gather background data, make field observations, figure out the problem, and make a report. This paper describes a very hurried investigation at the Guajataca Dam in Puerto Rico, a few days after Hurricane Maria. The dam was severely damaged, and was expected to fail at any time, flooding towns and cities downstream. Authorities needed to know: How long before the dam failed? An Urban Search & Rescue (US&R) team managed to get two engineers to the remote site. Conditions were less than ideal. They had almost no information about the dam, their time at the site was limited to a few hours, and they were not dam experts. But the same investigation steps prevailed—gather data, observe conditions, think it through, and make a report. In the end, a workable plan emerged.

A systematic and proper data collection for a forensic investigation requires a clear description of the debris field and an inventory of the material at the site. In many collapse cases fatalities may result. The efforts to extricate the victims or recover the bodies disturb the debris field. Stabilization of affected buildings needs to occur immediately. By the time the forensic engineer is called to investigate, data may be somewhat compromised by the immediate incident response. Especially when occurring in densely built areas, building collapses or large construction accidents require safety zones that include street closings and vacating of buildings that impact the life of the inhabitants in major ways. When these last, there is an extraordinary pressure from the community to accelerate the investigation. Forensic standards of care mention risks to investigators, but do not discuss possible involuntary spoliation due to the immediate response and time pressures. The paper presents several cases drawn from the author’s experience, where the need to attend to the needs of the inhabitants and expedite site work, created difficulties in data collection (WTC, building, and crane collapses). In some cases, there might have been failures to recover potentially significant elements. The paper is intended to start a discussion on improving the integration of the data collection function in the Incident Command System developed by the Federal Emergency Management Administration (FEMA).

In forensic assessment, new technologies are being developed and implemented at a rate which far outpaces typical updates to design standards. The speed of this technological development and implementation may prove challenging for the field of civil engineering, which relies heavily on considerations from standard of practice, because there must be a strong technical understanding of the precision, bias, and repeatability of a new assessment tool before it may be successfully used for forensic assessment. This paper presents a discussion on unmanned aerial systems (UAS), which are the leading platform for advances in technologies, such as near-infrared thermography, image processing, and machine learning. Advances in these areas are reviewed in this report. While UASs were found to be useful for certain nondestructive forensic assessments, several shortfalls, and common misunderstandings associated with these potential forensic tools were identified and discussed in this report.

Restoring a National Historic Landmark which is considered a unique and exemplary piece of Art Deco architecture and an iconic beacon for the City of Detroit may seem a daunting task. Utilizing a combination of state-of-the-art 3D Laser Scanning (LiDAR) combined with traditional hands-on examination techniques, the author developed a multi-pronged approach to understand the unique challenges facing the Fisher Building and develop a full restoration plan. This presentation will discuss the façade maintenance/restoration program of a 28-story building with a marble clad exterior. The paper is an overview of the hands-on inspection and make-safe repairs that were performed at the building elevations. In addition, the paper discusses how LiDAR technology has been employed to remotely monitor and detect the façade movement.

Unmanned Aerial Vehicles (UAVs) are tools that are utilized in inspections that can minimize human risk when working at high heights. UAVs provide access to critical locations and they are cost-effective compared to traditional methods. This study is aimed at analyzing the structural conditions of a steel bridge and a reinforced concrete viaduct, using an UAV. The steel bridge is in Paulo Afonso and the reinforced concrete viaduct is in Garanhuns, both cities located in northeastern Brazil. Drone models manufactured by DJI were used. Aerial records were made to identify possible pathological manifestations and to characterize the preservation of the structures. As results, oxidation spots were found on the bars and cracks and efflorescence were found on the foundation of the steel bridge. On the viaduct, more than the cracks and efflorescence, exposed reinforcements were found in a state of degradation. Thus, the efficiency of using the UAVs for the evaluation of the bridge and the viaduct was verified.

Computer models are useful for both structural design and forensic analysis. In the process of design, loads and materials must be assumed. In contrast, when investigating a failure, it is possible to know the materials and structural configuration as well as the loads applied at the time of failure. The necessary modelling is thus very different from the design process. Nonlinear models provide a powerful tool for forensic investigation, provided that they are used correctly. Many examples have been published in the American Society of Civil Engineers’ Journal of Performance of Constructed Facilities (ASCE JPCF) or presented at the eight ASCE Forensics Congresses, held approximately every three years since 1997. This overview paper will review case studies of modelling applied to forensic investigations, and also examine some of the issues associated with the use of such models.

On June 17th, 2018, a 1,000-year storm dropped nearly seven inches of rain in under nine hours across regions of the Upper Peninsula of Michigan resulting in a federal major disaster declaration. After the storm, site inspections were performed to evaluate the resulting culvert washouts and associated damage along 9.5 mi of recreation trail, just north of Lake Linden, Michigan. There are over 160 culverts along this section of trail, of which 44 were washed out and 40 were found to be either completely blocked by debris or collapsed. The use of cloud-based GIS mapping software allowed engineers to define specific parameters for condition assessment, record the conditions observed at each site, and geo-locate the data in real time. This allowed for rapid evaluation of the numerous culvert sites, improved communication with key stakeholders, and enabled faster data review used for immediate risk assessments and cost comparisons for remedial work. Since then, advancements have been made in GIS data collection and reduction technology, that allows for improved efficiency and accuracy during site investigations. This paper describes the advancements now available in this technology.

Computer vision, a field which falls under artificial intelligence, is increasingly establishing grounds in many disciplines, as the demand for automated means to solve real world problems gradually grows. Forensic engineering is a discipline that has been moving very closely towards the use of computers as investigation and problem-solving tools. This begins to kindle ideas of how forensic investigation and computer vision can work together to create new approaches and techniques within the field. This paper explores how to use computer vision as a tool to classify the building materials, evaluate the details, and potentially identify distresses of building envelopes using a collection of existing digital images and algorithms that help train the computer to produce efficient and reliable results. Discoveries about computer vision and the complexity of replicating and automating the human visual system encourage deep research on the programming of algorithms to improve and recognize the machine’s ability for the forensic investigation.

Digital, or virtual, reconnaissance methods are growing rapidly in post-disaster assessments; however, there is no standard approach to data collection and the associated limitations have not been widely explored. Digital reconnaissance involves the remote collection of structural performance information from several online sources including government databases, social media, and local news articles. This contrasts with traditional reconnaissance, which involves engineers on-site collecting pertinent information to analyze structural performance. While there are clear benefits to remote data collection such as safety and the number of structures that can be analyzed, the overarching goal of this study is to understand the limitations of this method as a function of the type of online data collected. Specifically, digital reconnaissance was conducted for hundreds of natural hazard events in the United States throughout 2020. The events covered were diverse in terms of hazard type, damage severity, and geography including both urban and rural areas. Semantic analysis of the collected reconnaissance data highlights key terminology to describe structures and corresponding damage that is unique by primary source. These results are significant for future digital reconnaissance efforts by enabling targeted and automated searches for post-hazard information.

With recent increases in deadly fires, earthquakes, and terror attacks, the need for implementing new technologies to achieve maximum disaster preparedness in public and densely populated buildings is paramount. Building Information Modeling (BIM) enables the development of data-rich models that can be used for simulation and emergency response management. In this study, to evaluate the applications of BIM-based analysis in emergency response practices, a comprehensive literature review is performed. This paper investigates the applications of BIM in different phases of in-building disasters and highlights major applications of BIM as (1) preventing failure by facilitating predictive maintenance, (2) evacuation planning and guidance, (3) improving decision-making for rescue team by real-time two-way information updating, and (4) finding the root causes of failure. Finally, the gaps and challenges for each aspect are addressed and discussed.

Ground Penetrating Radar (GPR) has recently gained momentum to nondestructively detect embedded objects and defects in concrete structures. Quality of the scans and reconstructed images are directly correlated to dimensions and depths of the concrete defects and embeded objects, as well as the frequencies of the GPR antennas. Laboratory reinforced concrete slab specimens, with embeded defects and objects, were constructed and nondestructively tested. Four GPR antennas of 400, 900, 1,600, and 2,600 MHz were used in the nondestructive testing. Objects in the concrete slabs include #3 to #8 rebars located at diferent depths and various artificial voids and delaminated areas. Synthetic aperture forcusing technique was applied to effectively intepret the GPR data, as well as to improve both the two-dimensional and three-dimensional reconstructed images. The study concluded that all the four antennas could detect the embedded objects near the concrete slab surface. It was observed that the higher the frequency of the antenna the better the quality and sharpness of the reconstructed images. GPR signal attenuation assisted concluding a varying detecability scale for embedded objects in concrete slabs.

Ultrasonic echo tomography (UET) is a non-destructive test method to obtain 3D images of concrete subsurface conditions that can be used to identify the extent and the locations of subsurface defects. In this preliminary study, UET scanning was performed on a limited number of post-tensioned (PT) beams of a concrete moment resisting frame structure. In some beams, concrete subsurface voids with a plan dimension up to about 4 m were detected underneath dense reinforcement. Destructive exploration by chipping away concrete was performed afterward to further investigate the UET test areas exhibiting signs of possible subsurface voids. It was observed during the destructive exploration that some of the detected voids could vertically extend into concrete beams by a depth of 100 mm (4 in.). The relationship between the extent of subsurface voids and the fundamental circular frequency of the frame structure was determined in this study. Based on this relationship, the maximum allowable extent of subsurface voids could be determined. Future research needs were proposed.

Forensic investigation after the failure of a bonded post-tension (PT) tendon has shown that in most cases, these failures occur because the strands were not properly protected by the grout. There is often a void or deficient grout which provides an environment that will lead to strand corrosion, and if left unmitigated, eventually failure. Identification of PT tendon grout defects is very difficult to perform with standard inspection techniques and these PT issues are commonly not identified until a serious failure occurs. This paper will review the innovative ways nondestructive testing can locate voided or defective grout and document corrosion in external and internal PT tendons. The paper will focus on the use of the acoustic method, impact echo/pulse velocity (IE/PV), which can determine voiding by analyzing the amplitude and frequency of the resonating compressional, and shear waves along the PT tendons. Through analysis of these stress waves, a trained practitioner can locate defects in the grouting of both internal and external tendons. The paper will provide case studies of two different bridges where a failed PT tendon on each structure prompted an investigation into the condition of the other tendons. It was discovered that grout voids were a prominent issue throughout the structures and that corrosion was at advanced stages.

This paper will describe a forensic investigation that was performed on a manufactured metal building that suffered a partial roof collapse following a rain storm. The building was a manufacturing plant and the collapse resulted in the plant being offline. Quickly returning the plant to operation was very important to the owners. The owner’s engineers quickly concluded that the roof drains had been obstructed, and the z-shaped roof purlins failed due to overload by ponded water. The owner’s engineers directed the contractor to rebuild the roof to match the existing. And, further investigation by WJE determined that the partial roof collapse was not a result of overload of the roof purlins but rather the result of an instability associated with a beam-over-column connection. This paper will review the failure analysis as well as review beam-over-column connections and their history in the ASIC Specification.

Several packages of failure case studies have been published by the Education Committee of the ASCE Forensic Engineering Division aiming to promote failure literacy of professionals and students in the architecture, engineering, and construction industries. This paper discusses the efforts of the committee to compile a collection of failure case studies of ethics, including design flaws of Citicorp Building (NY, US), Harbour Cay Condominium collapse (FL, US), Rana Plaza collapse (Savar Upazila, Bangladesh), Sampoong Superstore collapse (Seoul, South Korea), Versailles Wedding Hall (Israel), Hyatt Regency Walkway collapse (MO, US), Montreal Olympic project management failure (Montreal, Canada), and Flint water crisis (MI, US). The paper discusses the overview of three cases in ethics and provides guidance on using these cases to understand and interpret the code of ethics of professional engineers. Lessons learned from these cases are presented, reaffirming that all professional engineers should commit to ethical responsibilities in society, the natural and built environment, the profession with regards to their clients, employers, and peers. It concludes that the health, safety, and welfare of the public should take precedence over all other responsibilities of practicing professional engineers.

NOAA’s Office for Coastal Management estimates that climate disasters created $136 billion in damages over 2018 and 2019. Some years are worse; NOAA estimates that climate disasters cost over $300 billion in 2017. Many of these damages are created by wind forces acting on structures. Further, regional construction practices can make damage assessments challenging. Tile roofing is a favorite among architectural aesthetics utilized in Florida due to its visual appeal, durability, and wind resistance. With over one thousand miles of coastline, and the majority of the state consisting of a peninsula separating the Atlantic Ocean and the Gulf of Mexico, it is not uncommon for tile roofs in Florida to experience hurricane force winds. Thousands of tile roof sections have been assessed for wind-related distress by the authors of this paper. This paper will provide case studies representing the distress patterns observed by the authors. Common forms of distress observed in tile roofing will be discussed, and the case studies will provide insight into the diagnosis of wind-related distress to both clay and concrete roof tiles. Understanding distress patterns common to tile roofing allows owners, engineers, code officials, manufacturers, insurance industry professionals, the tile roofing industry, etc., to better assess the extent of damage related to wind forces and to improve the resistance of tile roofing against wind forces during natural disasters. Examples of wind-related distress and common conditions encountered during windstorm investigations provide insight into the portions of the Florida Building Code (FBC) which address remediation of damaged tile roofing.

The Education Committee of the ASCE Forensic Engineering Division aims to promote civil infrastructure failure literacy of professionals in architecture, engineering, construction, and related fields. Case studies of notable failures have been shown to provide an opportunity to educate students and professionals in technical, professional, and ethical areas. The Education Committee has published several compilations of failure case studies and is currently publishing of a collection of failure case studies of concrete structures. This publication includes the Kobe Viaduct, the Norway Sleipner, the Khobar Towers, the Tropicana Casino parking garage, the Concord Overpass Collapse, the Pipers Row Car Park, the Canterbury Television building collapse, and the Alto Rio Building collapse. Each case study presents an overview of the structure and relevant background information, describes the failure and contributing causes, presents lessons learned from the failure, and provides a list of references for additional and supporting information. This paper provides an overview of this package of concrete structure failure case studies, providing highlights from three cases included in the forthcoming publication. Guidance on the use of these case studies to recognize causes of failures is presented, with emphasis placed on the fact that multiple factors (such as design errors, material deficiencies, construction defects, quality assurance issues, or communication lapses) often contribute to such failures. Lessons learned from several of the case studies are presented, and contributions of these lessons learned to the forensic engineering education and professional practice are discussed.

This paper provides an overview of how failure prediction of critical members in an open web steel joist is used in multiple courses in a structural engineering curriculum. The forensic example is used in an introductory engineering mechanics course to demonstrate how the method of sections and joints can be used to analyze a truss system widely used in practice. Combining the concepts of steel yielding, column buckling, and factor of safety allows the students are tasked to predict the critical members in the joist. Immediately, following the analytical exercise, students experimentally verify their predictions. Later in the curriculum, students revisit their analysis in a steel design course. The students are posed with a retrofit competition where groups compete to increase the load carrying capacity of the joist and changing the failure mode of the joist. The group that completes this task for the least costs (material and labor) is crowned class champion. Students often conduct an analysis to determine forces in members; however, rarely do they predict critical member and failure mode in an assembly and then verify their results in real time. Even more rarely does this experience carry through multiple courses. The format of the lectures, laboratory exercises, laboratory execution, assignments, and competition are presented. Additionally, the paper includes discussion on how the experience was altered due to COVID considerations. Assessment data, student feedback, and recommendations for additional expanded assignments are presented.

This paper provides an overview of a multidisciplinary project focused on application of acoustic technologies in the discipline of forensic engineering. This freshman project was developed by faculty in civil, mechanical, and electrical engineering to highlight collaboration between disciplines and provide students a highly interactive hands-on experience. The course objectives were to: identify the broad range of applications of acoustics in electrical, mechanical, and civil engineering to solve complex technical problems, apply acoustic and ultrasonic technologies to collect and analyze data for material classification and flaw detection, nondestructively evaluate material characteristics of products and structures, construct and destructively evaluate reinforced concrete beams, and to clearly and succinctly present technical data in written, visual, and oral formats. The format of the lectures, hands-on laboratory exercises, and homework assignments are provided. Course and teacher survey data highlight the many aspects of the project that were successful and data comparisons between other courses are made. Recommendations for how this topic could be included in other discipline-specific courses and potential modifications due to Covid-19 are presented.

This presentation is about the experience of discovering procedural non-compliance as a root-cause of several critical equipment failures. These are often failures that many others had previously investigated but had not identified root-causes of the failures. By recognizing that there are 3 areas to consider when analyzing failure—physical, human, and latent—the mindset of the investigator broadens to consider more than the broken component. To illustrate the concepts, a basic summary of three major equipment failures will be used to show how the physical, human, and latent causes of failure can lead to procedural non-compliance. In basic terms, people do not always follow the outlined procedures, but they do not seem to realize it. Additionally, certain “red flags” will be presented in plain terms that can alert the investigator to the possible existence of procedural non-compliance as a root-cause. By recognizing the existence of these types of failure causes, the investigator can more easily determine root-causes of failure.

It is important to study construction failures in order to determine their root cause or causes so that future failures can be avoided. One such study was conducted by a subcommittee of the United States House of Representatives following a number of structural failures in the 1970s and 1980s. The subcommittee findings were released in 1984 in US Congressional House Report No. 98-621, titled Report on Structural Failures in Public Facilities. One of the factors identified as critical to preventing structural failures was inspection of construction by the structural engineer of record (SER). Given that finding, structural engineers need to be actively involved throughout the construction process, using inspections as a means to promote safety, improve the quality of the work, and reduce claims due to failures. Concerns regarding liability, construction schedule, and costs are major reasons why SERs do not perform inspections. SERs can manage those concerns, however, by understanding the relevant building code requirements regarding inspections, the benefits of inspections with respect to safety and quality of construction, the roles of the parties involved in construction projects, and the legal duties of the engineer.

A significant part of the damage due to construction failures could be prevented by inspection. However, monitoring is not yet widespread in construction. The critical parts of many structures are not even accessible to inspection. Tragic failures could have been prevented if a monitoring plan had been in place. Innovative and unconventional structures that have not yet been empirically validated are particularly prone to unexpected failure mechanisms. Therefore, in order to determine if these structures behave as predicted, during construction and operation, a monitoring strategy should be developed during the design stage, before construction begins. Monitoring can be used not only to assess structural performance and provide guidance on required maintenance or repair activities; but, in addition, to verify or reject design assumptions and the appropriateness of the construction process. The present paper discusses monitoring strategies based upon a conceptual framework and classifies monitoring strategies according to two criteria: monitoring technology and frequency of measurement. Case studies validate and illustrate the benefits and the implementation of the concepts discussed in this paper.

Structural monitoring can serve as a valuable tool to help manage risk of failure or damage during construction in close proximity to existing buildings and infrastructure. However, the success of monitoring solutions can depend heavily on the relationship between the client and the specialty engineer engaged for system design and implementation. This paper explores the challenges and successes experienced during two adjacent construction structural monitoring projects in the Chicagoland area that occurred concurrently. In one case, the client was the project owner who had a vested interest in avoiding potential loss and litigation. In the other case, the client was a contractor who was required to conduct monitoring to meet a specification. The cases will highlight differences between the engaged stakeholder with a performance requirement and the client meeting a prescriptive requirement. Therefore, the authors will discuss the importance of understanding the engagement level of the client in order to calibrate the value proposition. On one end of the spectrum, the specialty engineer becomes a partner and trusted advisor of the client in implementing a risk management solution. On the other end of the spectrum, the specialty engineer must focus on being a provider of the most economical, practical, and technically correct solution, without gold-plating. Tools and techniques applied in each case will be discussed and lessons learned will be explored.

An institution of higher education recently decided to relocate and repurpose several of their existing dormitories to allow for construction of new dormitories. The three-story dormitories generally consist of unreinforced hollow masonry foundation walls, with reinforced-concrete footings. The building relocations required excavation beneath each building to provide clearance for the main jacking beams and cross beams to be inserted below the buildings. The building mover successfully transported the first two dormitories. During the third building relocation, the general contractor (GC) found the east foundation wall at one of the dormitories was reinforced concrete, rather than hollow masonry. The GC engaged a saw-cutting contractor to core access holes to insert the cross beams to lift the structure and then saw cut a horizontal separation joint through the east foundation wall of this dormitory above the line of core holes. After saw cutting the reinforced-concrete east foundation wall and excavating immediately adjacent to the east foundation wall footing below the bottom of footing, the east foundation wall at the third dormitory experienced a bearing capacity failure, which required emergency stabilization and shoring of the building. The failure caused differential settlement of the footing along the east side of the third dormitory, and large cracks developed in both the reinforced-concrete foundation wall and the hollow-masonry exterior walls above. This paper provides an overview of the project and discusses the causes of the failure and the emergency building stabilization.

Foundation construction especially deep excavation and pile installation in densely built areas in urban cities such as New York City can be challenging due to the presence of numerous adjacent structures. Errors or omissions in the design, improper construction practices, and inadequate inspections may result in damage to the adjacent properties, which causes disturbance to the property owners and may lead to project delays, monetary loss, and litigation. This paper provides a background on adjacent construction issues, focusing mainly on foundation construction. It also provides introductory information about pile installation techniques, namely driven and drilled piles and possible effects of each technique to the nearby properties. Two case studies involving pile installation in New York City are presented to illustrate two different types of damage the adjacent buildings suffered. The first case study is about installation of a support of excavation system which utilized driven piles and caused settlement of the adjacent yards. The second case study is about installation of a foundation system supported by mini piles that caused water damage to the adjacent buildings. The consequences of the damage and the measures taken following the damage are also discussed in each case. The paper also provides recommendations for foundation contractors and engineers so that the risk of damage to the adjacent building from pile installation can be minimized.

Construction-induced vibrations can cause notable shaking in existing buildings near active construction sites. Some of the most common sources of construction-induced vibrations are demolition activities, foundation pile installation, soil compaction, and other dynamic actions generated by construction or deconstruction machinery. These vibrations can damage the adjacent building’s structural or architectural features or disturb its occupants. The adjacent sites are generally instrumented with seismographs to monitor the magnitude of vibrations while the construction or deconstruction activities are ongoing. Moreover, issues related to construction-induced vibrations are emerging as a concern in many cities across the United States due to the increasing density of buildings or transforming existing low-rise buildings into high-rise condominiums. Limited guidance is available in local building codes to assist engineers, building officials, developers, contractors, owners, and building occupants proactively evaluating the risk of damage caused by adjacent construction vibrations. Therefore, this article discusses published literature that correlates the construction-induced vibration levels to building’s damage and reviews the current state of the art in vibrations monitoring through two case studies. A case study is also discussed where soil-structure interaction analysis is used to anticipate the risk induced to the adjacent buildings by construction or deconstruction activities.

The paper will summarize the steps taken to successfully perform vibration monitoring on behalf of the owners of a modern, concrete-frame condominium complex in Charleston, South Carolina. The complex had recently undergone major renovations and the owners were concerned that pile driving for a neighboring construction project would damage their building. Prior to the start of the project, a preconstruction survey of the exterior was performed. A solar powered, triaxial geophone was installed to continuously monitor ground vibrations during the project, which provided automatic alerts when certain thresholds were exceeded. Additionally, accelerometers were installed at several locations on the structure to continuously measure building movement and to correlate any ground vibrations resulting from the construction to actual building movement. The monitoring determined that ground vibrations during construction were not high enough to cause damage to the building. Post-project data analysis revealed that ground vibrations caused by pile driving were lower than those caused by nearby vehicular traffic and the highest building accelerations were recorded during a hurricane. No potentially damaging building movement occurred from pile driving activity despite complaints from the residents. To successfully complete the project, coordination and communication between the engineer, client, contractor, and developer were required.

Underpinning has become a common practice in lot-line construction to support excavations deeper than historic adjacent structures without undermining them. However, if the underpinning design and construction are not performed with great care and with sufficient understanding of the existing conditions of the historic structure being underpinned, this can lead to differential settlement and potentially the subsequent partial collapse of the structure. The purpose of this paper will be to address the multitude of factors relating to underpinning design beneath historic structures, and will discuss the requirements and potential risk factors of the underpinning design of historic structures including soil investigations, dewatering, building investigation, etc. Additionally, this paper will discuss methods for building assessment and monitoring during underpinning construction to help avoid a potential catastrophic failure. Case studies demonstrating the consequences of inadequate or poorly constructed underpinning will be presented to highlight the potential risks of underpinning historic structures.

A four story building in Philadelphia, PA, collapsed in 2013, onto an adjacent occupied building, killing six persons and injuring over a dozen more. The building was in the process of being demolished. The author’s firm was retained by attorneys to investigate the causes of the collapse, to determine the roles and responsibilities of the various parties, and to determine whether the demolition process was performed in accordance with industry standards. Thus, as part of the investigation, we inspected the debris, we reviewed all available project documentation and standards of practice, and we collected photographs and videos of the demolition process from social media and other sources. This investigation enabled us to reconstruct the demolition sequence that was actually used, and the status of the demolition moments before the collapse. Therefore, the author testified in criminal court on behalf of the City of Philadelphia. The focus of the testimony was on contrasting the demolition sequence that was used to the sequence that should have been used. To clearly communicate this to the jury, a 3D digital model was developed, which was used to show the jury what the building looked like, from any angle, just before the collapse. An animation was also developed, to show the proper demolition sequence. Furthermore, this paper presents the findings of the investigation, discusses expert testimony, and provides recommendations for minimizing similar failures in the future.

A silo structure relies upon its capacity to resist hoop stresses within the silo’s corrugated steel wall. Designs are based upon the silo’s ability to remain circular in shape. An internal wedge hopper design is analyzed to determine the effect of soil consolidation under the soil wedge and resultant wall pressure distribution. An internal wedge hopper consists of compacted soils beneath a concrete slab within the constructed steel wall. Techniques used to analyze the soil/structure interaction upon the silo walls are discussed as a basis for determining the resultant shape, i.e., roundness, and state of stress of the silo wall structure. The analysis indicates the integrity of the silo is a function of construction practices including lift sequencing and degree of compaction of soil placed for the construction of the wedges. While the completed construction of a silo may comply with design specifications, placement of bulk storage materials within the silo may change the state of stress, out-of-roundness, affecting the performance of material handling systems, or worse, cause catastrophic failure of the silo.

The role of engineering judgement and contractor experience is illustrated through two case studies where renovation work led to failure of designated historic masonry buildings located in Ontario, Canada. In the first case study, neglecting the pre-existing deterioration and bulging of the masonry exterior wall, and lack of assistance from a structural engineer during sidewalk replacement adjacent to the building’s wall caused a portion of the exterior wall to collapse. The second case involved a project to lower the basement floor in a semi-detached house. Design drawings for the project lacked adequate information on temporary support during construction. The engineer allowed the contractor to remove the entire slab ahead of underpinning. With the floor slab removed and without adequate lateral bracing, part of the foundation wall failed upon the removal of the soil for underpinning.

Over the years, numerous construction collapses have occurred to large wood framed buildings as a result of inadequate temporary bracing of long-span press-plate wood trusses, which have resulted in numerous construction related injuries. In response, provisions were implemented in the building code starting with the 2009 IBC to require specific design for the bracing system as well as special inspection requirements during the erection process. Unfortunately, many designers, owners, and building officials are unfamiliar with these regulations and many engineers provide limiting language in their drawings specifically excluding temporary shoring and bracing from their scope as part of means and methods for the contractor. This paper will discuss the nuances of the code provisions and highlight the void of understanding and responsibility that has resulted in a continued hazard in the construction industry. While the code assigns responsibility for engaging a design professional to the owner, education and enforcement from the building official is critical in safeguarding the industry assuring proper design and construction of the temporary bracing is implemented. In addition, communication between the owner, contractor, Engineer-of-Record, and truss designer needs to include a well-established scope of responsibilities to assure these provisions are met and the building is constructed in a safe manner.

Evaluating whether a structural system has collapsed may not be as obvious as it sounds. Most people consider collapse to be a condition where the structure or a portion thereof has fallen down. However, in the context of insurance coverage, evaluating whether “collapse” has occurred may be far more nuanced—especially when collapse is not explicitly defined in the policy. State courts have generally adopted one or more of three interpretations for the term collapse, broadly described as: (1) actual collapse, (2) imminent collapse, or (3) substantial impairment of structural integrity (SISI). Even with these interpretations, there are widely varying opinions regarding the level of structural impairment that qualifies as collapse. This is especially true for SISI. Although some state courts have attempted to define collapse using commonly understood terms, there are no industry standards that define these conditions in customary engineering terms (demand, capacity, factor of safety, etc.). This ambiguity leaves individual engineers to form their own opinions, which predictably, vary widely between engineers. This paper draws from available literature and prior legal findings to propose a rational method for engineering professionals to evaluate collapse based on design loads, strength of materials, and system effects, with a particular focus on SISI.

A bulkhead failed during construction of a riverfront redevelopment project in a southeast port city. Errors and omissions in the design and detailing of the bulkhead were discovered and determined to be the root cause of the failure. A pragmatic repair approach was developed by the engineer-of-record for the project, which included bulkhead stabilization measures, load reduction, and replacement of failed bulkhead components. The loss was covered by builder’s risk insurance, which included a policy endorsement covering all damages except “costs incurred to improve the original materials, workmanship, design, plan, or specification.” A dispute arose related to whether the repairs constituted improvements that were excluded or whether the actions were appropriate and necessary steps to repair or facilitate the repair of the bulkhead system and covered by the builder’s risk policy. This paper will explore the role of the forensic engineer as not only an investigator of root cause, but also as a technical resource who, together with legal and insurance advisors, can assist a client with many complex aspects of recovering from a failure event. Features of the bulkhead design that resulted in the failure will be described and aspects of the emergency response and subsequent repair approach will be analyzed in the context of the builder’s risk policy exclusion.

By agreeing to be an expert witness in a forensic engineering project, the engineer inherently assumes particular responsibilities. These responsibilities can mostly be defined by consideration to the ASCE Code of Ethics. Primary among the canons of the Code of Ethics is to hold paramount the health, safety, and welfare of the public. This entails not becoming an advocate for one’s client, but to be an advocate for the well-being of the public. In some cases, the expert may feel conflicted by the need to criticize the work of other engineers. The manner in which the expert must handle that situation will be dictated by consideration of the canons of the code of ethics. This paper presents case histories to demonstrate examples of both good and bad conduct by experts not only in testimony but also in engineering practice. In presenting the issues raised by the case histories, the paper attempts to raise the issue of the definition of Standard of Care as opposed to the Standard of Practice. This has frequently been a contentious issue, and continues to be so. However, it is an issue that must be kept in the forefront of expert testimony. The paper discusses this issue in the context of the Canons of the Code of Ethics.

This paper and presentation are designed to educate professionals on the “fine line” that exists when making ethical decisions. The focus will weave the ethics-centric discussion through multiple practice areas (exemplars would include forensics, insurance, and litigation). A quick review of “ethics” in general begins the conversation; from right and wrong, to good and bad, and is followed by ten strategies for ethical decision making that are based on the general principles of engineering and business ethics, with a skewed view for forensics and claims professionals. Each of the ten steps opens with a dialogue of their respective ethical function, with a pattern of approach for each item for consistency. Discussions will include when the step was done right or wrong, and such lessons learned. Moreover, case law discussions (with relevant references and case studies) will be discussed including the consequences of the ethnical and unethical decisions that were made in each case. Such perspectives shed light on the underlying theme—the fine line between ethical and unethical.

Claims for Differing Site Conditions (DSC), also commonly known as Changed Conditions, mainly occur when subsurface or latent physical conditions encountered at the construction site differ materially from those that are represented in the contract documents. DSC claims increase the risks to the project cost and schedule and may lead to prolonged court litigation. This study primarily focuses on who is responsible for the risks of the additional costs and delays associated with the DSC claims. To evaluate these risks, the research methodology includes a review of the literature as well as the analysis of different types of DSC claims and court requirement to prove such claims. The study finds the risk responsibility is shared between both the owner and the contractor and depends on disclosure of factual, qualified, and interpretive geotechnical information. The study further suggests strategies to both parties on claim avoidance and claim management.

Structures often give warnings of impending collapse. It is important to listen to the warnings and act accordingly. Examples include the Quebec Bridge collapse of 1907, the Hartford Civic Center collapse of 1978, the Laval, Quebec, de la Concorde overpass bridge collapse of 2006, the Florida International University pedestrian bridge collapse of 2018, and others. In each case, there was a time lag between clear indications of failure and the failure itself. This suggests, unfortunately, that there is a key gap in engineering practice. The warnings that the structure gives us may not be recognized for what they are. It may not be clear how and to whom to report the warnings. Lastly, it may not be clear how to act, who is to make the decision, and how to warn the public and reduce risk. Therefore, there is a need to develop ways to report these warnings and turn them into action in order to protect the safety of the public and construction workers.

An engineer’s employment, business, and professional practice can be affected by an assessment by others of that engineer’s performance related to the “standard of care.” The concept of the standard of care is often misunderstood and misapplied, to the detriment of the engineer whose performance is being assessed. This paper addresses the concept of the standard of care, and shows how an understanding of the standard of care can aid an engineer in avoiding and defending against claims of professional negligence.

Engineers engaged in forensic investigations have unique roles and responsibilities that differ from those of design engineers, and must adhere to a distinct standard of care that is too seldom discussed, considered, or understood. This paper explores the forensic engineering standard of care question through the case study of a portable water storage tank failure. The incident precipitated the production of no fewer than ten engineering reports asserting various distributions of blame on the manufacturer, owner, installer, and designer, a number of which ultimately called into question the structural design of an entire line of production equipment. WJE reviewed these volumes of work, and finding them inconclusive, performed independent non-linear finite element analyses of the design, fabricated representative connection test specimens, and subjected them to high-cycle fatigue and strength testing to evaluate service life performance. Our results and the actual in-service performance demonstrated that the design met or exceeded relevant standards and performance requirements, despite voluminous, corroborating, and ostensibly sophisticated allegations to the contrary. We believe that such misrepresentations of reality are far too common to the forensic engineering field and draw a series of lessons from our experience on what the standard of care means to engineers who find themselves opining on another’s work.

Forensic engineers are called upon by third parties to provide technical evaluations, repair options, and expert opinions on causes of property damage or personal injury after an incident. As an expert, forensic engineers are expected to limit their testimony to their areas of expertise. Increasingly, however, forensic engineers are being asked to testify on whether certain conduct is “willful and wanton.” Is this testimony proper, allowed, and/or ethical? Absent training or expertise in evaluating “willful and wanton” conduct, the opining forensic engineer may violate ASCE ethics rules, licensure rules, and court rules for expert testimony.

Fact witness deposition testimony is one of many informational resources available to forensic liability experts in revealing the facts that will guide their investigation and be relied upon in expressing public statements, expert opinions, and expert testimony. However, mining fact witness deposition transcripts for relevant facts can be challenging, and may lead some experts to either dismiss, ignore, or overlook important facts. The consequence of working with incomplete facts may adversely impact an investigation and undermine an expert’s credibility. This paper surveyed approximately 20,000 pages of fact witness deposition transcripts from more than 200 depositions in more than 75 lawsuits in liability and personal injury matters. The results of this survey demystify the transcripts by offering familiarity with the deposition process and providing 10 tips on mining fact witness deposition transcripts. The 10 tips are: (1) request for the transcripts, exhibits, and errata; (2) navigating the transcripts; (3) breaking down the incident-related facts; (4) attentiveness to key words; (5) attentiveness to volunteered information; (6) attentiveness to false and misleading information; (7) attentiveness to corrections in testimony; (8) attentiveness to other relevant documents; (9) attentiveness to questions that can educate the expert; and (10) attentiveness to authenticated photographic exhibits. These tips benefit both seasoned experts, who may only have a limited working knowledge of deposition transcripts, and novice experts, while also providing retaining attorneys with insights into the forensic investigation process.

In this paper, Forensic Engineering experts Charles Hammond and Al Bustamante explore: Why is Forensic Engineering important to facility Owners, Property Managers, and Attorneys? They will provide a background that explains the value of an effective forensic investigation and will discuss the concept of Defect vs Deficiency: Structures can have many defects and not be deficient. They will share why the ability to differentiate between these two concepts is valuable for dispute resolution and to properly solve structural, materials, and architectural problems. Lastly, they will present several examples of forensic investigations, including up-close field observations, material sampling and testing, non-destructive evaluation, and structural analyses. Case studies will include ASR/DEF in precast columns, restrained cracking in a parking deck, and corbel cracking due to construction deficiencies.

While engineers are devastated when they first learn of a failure of a structure that they have designed, modified, or participated in its construction, this is just the beginning of an often years-long litigation journey if, eventually, there are legal claims as a consequence of that failure. Failures of silos in industrial facilities bring another level of complexity due to the number of parties involved (e.g., contractors, subcontractors, equipment suppliers, raw material suppliers, owners, plant operators, and maintenance personnel), the level of complexity in these industrial systems, and the cost of the equipment damaged as well as downtime, and potentially, serious injuries or loss of life. There are many causes of silo failures including design, construction, usage, and maintenance. During the long process of designing and constructing a silo, many omissions or oversights can occur. Many of these are due to the lack of training in this specialized field and the paucity of reliable, useful information in the literature, including relevant codes available for engineers in charge of the design of silo structures. Engineers in charge of the design and construction of silos as well as similar industrial facilities used to store and/or process bulk solids will benefit from this paper as they will be able to better understand the legal implications beyond silo failures. Engineers involved in forensic engineering and insurance claims will be able to gather information on the engineering as well as the legal side of failures in industrial storage facilities for bulk solids.

“All concrete cracks” is a favorite saying of engineers and contractors attempting to explain cracks in concrete work that they often cannot otherwise justify. However, it is often perceived as just an excuse for failing to provide a well-reasoned opinion regarding the likely cause(s) of the cracks and the negative ramifications, if any, associated with their presence. It is true that owners often expect unachievable results in their concrete structures when it comes to cracks. This paper will discuss the need to manage the expectations regarding concrete cracks on a project and how to properly address it when it inevitably occurs. Concrete structures almost always have cracks, and the project team needs to be made aware of this fact prior to construction. This can better help align the team’s perceptions of acceptable and unacceptable cracks with those shared by the Structural Engineer.

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Disputes are inevitable in construction projects and managing them is a considerable problem in project contract management, both for the time delay and for the cost involved. An increase in research to optimize Alternative Dispute Resolution (ADR) methods, able to guarantee a rapidly agreed settlement, can suggest lawyers new criteria to early assign in the precontract phase the most appropriate alternative dispute resolution criteria. For this purpose, this research investigates different methods to select the most effective dispute resolution criteria and try to translate in legal contract language the cumulative experience to being inserted as a clause into construction agreement. Other increases in research also occur in bringing the disputing parties together and in suggesting possible solutions to help achieve an agreed settlement during the conciliation steps. The authors analyze the common claims between the parties in construction contracts: delays, changes, unforeseen circumstances, insufficient information, and conflicts. Even though the claims must be properly constituted and documented, and the causes and effects must be clearly demonstrated, the quantification usually overestimates the loss due to inefficient productivity, which is extremely difficult to assess. The authors underline the role of the technical expert as specialized in identifying causes and effects by analyzing contemporaneous records and in verifying additional costs that must be backed up by full supporting documents.

Parking structures are essential infrastructure for the development of urban and suburban communities. Harsher exposure conditions due to structures openness, dynamic vehicular loads, de-icing salts, and construction and design deficiencies reduce garages’ life span. In addition, extreme weather, age of the structure, and inadequate maintenance contribute to further structural deterioration. In this paper, general distress conditions in cast-in-place, precast, and post-tensioned garages are discussed, along with probable repair solutions, asset management, and associated repair costs.

Details in construction drawings prepared by design professionals for multi-story, wood-frame egress stair construction are generally limited to stair opening size and code-prescribed tread, and riser dimensions. A flight of stairs constructed to meet code tread and riser dimensions can conflict with several wood engineering design principles and other building code sections. This disregard of wood design principles has caused performance issues, wood stringer failure, and in some cases personal injury from a partial or complete stair collapse. The primary reason is typical site-built or prefabricated wood-framed stair assemblies are constructed for a 40 pound per square foot (psf) live load application. This stair construction becomes problematic for egress stairs that are required by the building code to meet 100 psf live load. Forensic evaluation of several in-service stairs in these type buildings confirm insufficient stair stringer design capacity, fabrication deficiencies, and/or improper wood-framed stair construction. These shortcomings can be traced to three sources: the absence of code prescriptive guidelines for each stair component, the rarity of building design professionals to understand, analyze, and specify project specific stair stringers, and stringer support/connection details. This paper reviews available wood-framed stair stringer prescriptive information for 40 psf residential live loads to form a rational approach to egress stringer design and evaluation for use in higher live load applications.

Many façade systems are constructed with aluminum extrusions that are often fastened together with self-drilling and self-tapping screws. A failure of a cladding panel fabricated with this type of connection led us to evaluate the capacity of these connections for shear and tension loading, while also considering the effects of prying caused by eccentric loading. Thus, our evaluation consisted of performing laboratory testing of screw fasteners connecting two aluminum members in direct shear and tension, and comparing those values to capacities derived from equations found in the 2015 Aluminum Design Manual (ADM). Our laboratory testing also considered the installation method of the screws including drill speed (rpm), clutch settings, and effects of impact driving. We researched literature documenting prior testing on which the 2015 ADM equations were based and other industry literature to determine how screws should be installed into aluminum components to ensure proper connection performance. Our research found that there is limited guidance or recommendations for the method of screw installation. Thus, our limited laboratory testing consistently produced results lower than the ultimate capacities predicted by the equations provided in the 2015 ADM regardless of the installation method. However, we also found that the screw installation method has a significant effect on the capacity of the screw connection. Installation at higher rpm had the potential to strip the threads cut into the aluminum and screws installed using an impact driver typically resulted in fully stripped threads. Therefore, while further research on this topic is warranted, it does appear that the 2015 ADM equations may overestimate ultimate screw connection capacities and that screw installation methods have a significant effect on capacity.

When inspecting structures in an industrial facility on the Gulf Coast, deteriorated fireproofing was observed at a fin fan deck structure. The fireproofing had deteriorated to the point where it posed a major falling debris hazard in the plant. This paper is intended for structural design and inspection professionals, and will focus on the forensic study of corroded columns at a fin fan deck located at an industrial facility on the Gulf Coast. Furthermore, during the field investigation, plans were implemented to remove the fireproofing to mitigate the falling debris hazard risk. Upon removal of the fireproofing, it was discovered that the flanges of the steel columns had been significantly corroded and that more extensive repairs would be required. Through forensic investigation, the present damage was assessed, the root cause of damage was identified, and an effective repair plan has been implemented to maintain the integrity of the structure. The forensic investigation included a visual and tactile inspection at arm’s length distance from the affected members and ultrasonic thickness measurements of the corroded structural steel. Completing this thorough forensic study was a key to the success of the project.

Pressurized water pipes such as fire risers are often installed below commercial building foundations. Hydrostatic pressure imparted on foundation slabs during a fire riser rupture often results in damage to building foundations, requiring a detailed evaluation of the foundation and substrate prior to performing repairs. In isolated cases, the introduction of moisture from a fire riser rupture to underlying expansive soils can initiate volumetric changes that impart additional pressures on the building components. The objective of this paper is to explain the investigative process and methodology used to determine the extent of damage and appropriate repair strategy for these types of failures. A case study is presented to illustrate the investigative methodology, involving a ruptured fire riser beneath a concrete (floating) slab-on-grade foundation in Texas. The investigation revealed that a distinct region of the slab-on-grade foundation was damaged as a result of the fire riser rupture and required replacement.

In late 1982 or early 1983, a quarry in northeast Connecticut began extracting rock for aggregate that contains pyrrhotite, a reactive iron sulfide mineral known to oxidize in the presence of air and water. When the pyrrhotite oxidizes, the expansive reaction byproducts may crack the concrete, allowing moisture and air to more easily penetrate the concrete, leading to further damage. Depending upon rock geology and characteristics of the concrete mix, the problem manifests itself over varying periods of time—ranging from a few years to more than 20. As a result, an affected foundation may exhibit damage that ranges from barely discernible to very serious. Presently, there is no known solution to the problem save removal and replacement of the foundation. Thus, the visible attributes of the damage resemble those of alkali silica reaction (ASR), and it typically requires a petrographic analysis to definitively discern between ASR and damage from pyrrhotite.

From the early 1900s through the 1960s, wood bowstring trusses were a popular structural solution for roof framing, especially in buildings where long, open spans were desired. Many of these structures are still in service today, and due to increasing costs associated with the replacement of existing buildings, repair, and rehabilitation of these structures has become economically attractive. The reuse of bowstring trusses requires careful engineering assessment of their ability to continue to perform safely under applicable building code requirements. Successful assessment of in-place structural capacity requires a thorough investigation of existing conditions and a realistic structural analysis. This paper discusses the process of establishing design values for timber members in existing structures (visual stress grading) as well as considerations and methods to create finite element models that accurately represent the behavior of bowstring trusses. By using a realistic structural model, the engineer can better understand structural behavior, which will guide the process of selecting efficient rehabilitation options.

Section 2303.4.1.2 of the International Building Code requires the installation of permanent bracing on pre-engineered wood trusses to: maintain truss spacing, resist lateral loads, and prevent buckling of individual truss members. To meet this requirement, all three planes within the truss, the top chord, bottom chord, and web member, must be adequately braced as outlined in chapter three of the Building Component Safety Information (BCSI) Guide. In regions with heavy snow loads, bracing to prevent web member buckling becomes a critical, and easily neglected, component within a building’s structural system. This paper provides a review of permanent bracing requirements for wood trusses, illustrates a case study of the strength of an individual truss member where the strength is reduced by over 80% when bracing is either improperly installed or missing, and it discusses some of the indicators structural inspectors can look for to ensure their roof is properly braced while helping the building owner answer the question: “When should I shovel my roof?”

Structural assessment and evaluations were performed for the post tensioned (PT) concrete facility located in Williamsburg, Virginia. The facility is a six-level, concrete framed structure constructed in the 1970s and includes two levels of underground parking and four levels of occupied residential spaces. The project initiated from the exposed failed PT tendons observed at several locations in the garage level, and the scope expanded to other remaining floors concerning the failure of the PT tendons and structural stability of the structure. Furthermore, a condition assessment was performed to evaluate the damages of the PT tendons, to examine the as-built conditions of the structure, to find the cause of the damages, and to develop the repair design. The original construction drawings were not available, and the project required development of the base drawings including general concrete floor construction, locations of construction joints, and PT tendon layout in plan. Non-destructive testing was used to locate the PT tendons and their profile, exploratory openings were made to examine the conditions of the PT tendons, samples were taken to examine the material properties of the concrete and PT tendons, structural analyses were performed to evaluate the existing structure, and a repair design was developed to remediate the conditions. Various repair techniques were applied including concrete repair, PT tendon replacement, tendon splicing, and new anchorage placement.

Forensic investigations in concrete structures with fire damage is challenging, as concrete beneath the surface might have damage, even if the concrete surface might seem undamaged. When there is damage, determining the best repair approach is complex and depends on the type of damage and damaged elements. This paper discusses different elements of the post-fire investigation such as visual observations, surveys, and non-destructive and destructive testing. We also discuss different approaches to repair, illustrating these points using examples from real concrete buildings that have experienced fire damage. The review includes the typical types of laboratory testing recommended in the context of a post-fire forensic investigation and post-fire structural assessment and how the interpretation of their results can guide the engineer to identify the best repair design. The discussion also includes examples of how engineering and practical considerations drive the decision on the appropriate repair approach. These examples show the fundamental role that testing and interpretation of the results have in guiding the design of repairs. This paper is intended to illustrate the process of investigation, rather than being an exhaustive discussion of all the potential approaches and tests.

The historic inner dome and the interior supporting walls of the West Virginia State Capitol Building were found to have structural deficiencies. Several cracks were observed on the interior of the dome structure, and an in-depth investigation revealed that the Capitol dome structure was constructed with gypsum plaster reinforced with coconut fibers, also known as coir fibers. The application of using coconut fiber in the building construction is very rare, and no literature was available about the material behavior as a building construction material when used as reinforcement for plaster. Therefore, due to this scarcity of information, various mechanical material tests and rigorous analysis of their results were performed to understand the structural behavior of the dome structure, the cracking behavior, and to further examine the extent of retrofitting desired. Material samples of coconut fiber reinforced gypsum plaster were directly obtained from the dome structure and tested to evaluate various mechanical properties such as tensile strength, flexural strength, and compressive strength. The results obtained from these tests were directly used to define the material properties of the analytical dome model and became the design basis of the repair.

Fungal growth is a common biological condition that is encountered when moisture remains unabated in a structure. While fungi are commonly found in the indoor environment, their proliferation on building materials can impact the comfort and health of building occupants as well as degrade building materials overtime. Fungal spores are ubiquitous and routinely travel inside and outside of the structure through a variety of pathways. The amplification of fungi in the built environment are based upon the presence of a variety of biotic and abiotic factors that create a favorable environment for fungal growth to proliferate. The most important factors that influence fungal growth within a structure are moisture (water availability), nutrient availability, and temperature. Utilizing this knowledge, an evaluation of the fungal growth or fungal ecology, in the area of damage can provide additional insight into the circumstances that led to the water damage in question and help substantiate opinions pertaining to the origin, cause, and duration of a moisture source.

In the 1971 San Fernando Earthquake, partial roof collapses occurred in concrete tilt-up buildings when wood ledgers bolted to the tops of the tilt-up walls (supporting the edges of the plywood roof diaphragm and tying the roof to the wall) failed as they were subjected to perpendicular-to-grain (cross-grain) bending. Beginning with the 1973 Uniform Building Code, the use of cross-grain bending was prohibited for connecting roof diaphragms to walls. This loading condition is also disallowed through the absence of published design strengths for cross-grain bending and tension in the National Design Specification for Wood Construction. Despite these lessons learned, significantly less attention has been given to avoiding cross-grain tension in everyday loading conditions, such as hanging loads from wood beams. It is common in new and existing construction for the design team to specify HVAC equipment, insulated ceiling systems, fire suppression piping, and other equipment to be hung from wood beams in commercial and industrial buildings. In this paper, recommendations and guidelines for hanging loads from wood beams are summarized from the technical literature used in the US. Case examples of cross-grain tension failures are presented so that explicit building code and design standard provisions can be improved and similar failures can be avoided.

Metal plate connected (MPC) wood trusses are a popular structural framing system used in floors and roofs often for residential and light commercial construction. In the past several years, the authors have investigated multiple occurrences of failures of MPC parallel chord wood floor trusses related to large gatherings inside private dwelling units as a result of excessive occupancy conditions, and of MPC parallel chord wood roof trusses due to snow accumulations. The failures observed include MPC plate deformations; connector plate teeth partially or fully pulling out or separating away from the structural wood elements; or some combination of both conditions. Fortunately, these failures did not lead to catastrophic collapse. However, in several cases, they placed occupants in dangerous situations, and the repair and remediation resulted in a wide range of economic losses. In each case, the authors studied the conditions associated with the probable loads imposed on the truss framing that led to the structural and performance failures. This paper will present the reader with observations of typical patterns of MPC wood truss connection failures. In addition, discussion will include lessons learned from several case studies, a review of the event loading conditions associated with each case, a discussion of the observed MPC failure relative to the loads imposed, and recommendations for when investigating similar cases in practice.

Improper structural repairs can lead to future failures and building code requirements can impact the repair scope. It is important for a Forensic Engineer to be able to provide clear and practical recommendations for repairs, even if not responsible for the final design. One case study includes a failure analysis of an improperly repaired wood roof truss, which failed under moderate snow loading. A review of available weather data, on-site observations, and an analysis of the as-built repaired condition was performed. It was determined the design intent of the repairs was incorrect and repairs should not have been attempted due to the extent of previous damage. Furthermore, the repairs that were attempted imposed additional loads to the truss members which they were not designed to withstand. This paper will provide general guidance to determine the cause of a failure and an approach to provide repair recommendations, with supporting case studies. This includes an accurate determination as to the extent of damage and application of relevant building codes, including the International Existing Building Code (IEBC).

While hundreds of standards exist for testing the physical properties of many materials, there is no industry standard for testing shear strength in concrete. Ascertaining the actual shear strength across a bonded concrete interface, such as at repairs or construction joints, is particularly problematic. In investigating planar strength, the shear strength between concrete surfaces is of primary importance. Studies from the late 19th century to the present day have not resulted in a universally accepted standard test to determine the bonded concrete shear strength. Although there is no ASTM standard for a direct shear test at the bonded concrete interface, several methods used in various locations throughout the United States include the Brookhaven National Laboratory Guillotine Shear Test and the Iowa Shear test. Other shear test methods available include the Asymmetric Four-Point Bending, Bond Test (also called the Tensile Bond Test or Pull-Off Test), CTL Thompson Method, Iosipescu-65 Method, Jacking Shear Test (also called Push-Off Test), Slant Shear Test, Torsional Shear Test, and US Bureau of Reclamation Shear Tests. Also, this paper summarizes historical and recent research results at the University of Colorado Denver where different devices test direct shear in bonded concrete specimens. The research objective is to determine each shear test method’s pros and cons, and recommend one method as a universal standard regardless of the bonding agent or method.

Concrete corners are found in different structures, such as portal frame buildings, bridges, and retaining walls. In the literature, there is limited information regarding the effect of the reinforcing detail on the structural performance of concrete corners subjected to concentrated loading. This research aims to study the structural behavior of concrete corners reinforced with different steel reinforcement patterns. The experimental work includes the investigation of concrete corners reinforced with ten different steel bar patterns at the corner vicinity. Steel fiber was added to the concrete mix to investigate its impact on the corner performance. Results show that the ultimate strength of the concrete corners reinforced with additional steel area increased compared with the reference corners with no additional reinforcement. The results also show the significant effects of steel fiber reinforced concrete material on flexural strength compared with the same corner details tested without using steel fiber. The ultimate strength increased as high as 39%, while the cracking loads increased up to 26.6% for some corners. Also, efficiency (ultimate/calculated load) increased between 1.06 and 35.44%. Furthermore, it was observed that steel fibers improve the tensile response, limit the crack propagation, improve the retained strength, and alter the mode of failure. Two types of failure were observed at the concrete corners, bearing, and flexural failures. The bearing failure occurred due to the diagonal cracks propagated at the corner vicinity. In contrast, the other type of failure, called the flexural failure, occurred due to the cracks propagated in areas beyond the corner vicinity.

Minimizing concrete shrinkage can decrease the cracking potential of the deck. Therefore, the use of internally cured concrete (ICC), which is a promising method to mitigate concrete shrinkage at an early age, has been increased. Therefore, the main objective of this research was to evaluate the behavior of the ICC and conventional concrete (CC) under severe conditions. The behavior of the ICC and CC subjected to heating and cooling cycles was investigated. This test was conducted using Ohio CTE Device (OCD). This device was used to surpass the limitations of the ASTM C531, CRD 39, and AASHTO TP60-00 by using a temperature range from 60^oC to -60^oC (140^oF to -76^oF) and a dry condition. A plastic shrinkage panel test was also used to determine the cracking potential under severe conditions. The specimens were exposed to air-flow using high-velocity fans for a duration of 24 h to ensure that cracks due to plastic shrinkage stabilized. In addition, the testing program determined compressive strength, splitting tensile strength, coefficient of thermal expansion, and free and restrained shrinkage. From the results, an internal damage was noted for the ICC specimens after one cycle of heating and cooling. This damage was not observed in the CC specimens. This behavior indicates that the pore structure of the lightweight fine aggregate in the ICC has a significant effect on the mechanism of damage in the concrete due to the freezing of water.

Florida coastlines are highly corrosive environments conducive to the deleterious interaction between dissimilar building materials, which will result in significant damage and costly repairs. Often, cementitious materials, such as stucco (or plaster) and exterior tile-setting materials (thinset, mud bed, and grout) are in direct contact with the aluminum frames of sliding glass doors, windows, storefronts, balcony railing, and plates for sunshades and trellises. Due to the close proximity of the ocean and resulting saltwater spray, the corrosion process is accelerated. The proper use of special coatings, and/or separation of these dissimilar materials, becomes the difference between costly failures and an enduring building enclosure. Often, the coating applied to the aluminum frame meets the performance testing requirements of AAMA. However, handling and installation results in scratches to the coating, and thus, opening pathways for corrosion to occur. This paper discusses the phenomenon, current code requirements, industry standards, AAMA performance testing, and presents case studies.

An investigation was undertaken to determine the cause of on-going spalling concrete at the floor level construction joints of exposed exterior concrete columns in a recently constructed high-rise building on the east coast. A black substance was typically observed behind each spall location. Background research indicated that a hydrophilic waterstop strip was specified to be cast into the construction joints at the floor lines of the columns to prevent water infiltration into the building. A review of the waterstop manufacturer’s product literature did not provide information regarding water absorption characteristics, force generation of confined saturated waterstop material, or how the waterstop behaved when subjected to freezing temperatures while in a saturated condition. This investigation included a series of laboratory tests to determine physical properties and anticipated force generation of saturated water stop as well as a limited structural analysis to determine if the waterstop alone could be responsible for the observed distress. The investigation concluded that under certain conditions, expansion of embedded waterstop can exert enough pressure to cause spalling of surrounding concrete.

This study advances our understanding of metal corrosion rates among 21 common building, plumbing and electrical components by comparing their qualitative responses to four exposure scenarios: control conditions (24°C and 50% RH), elevated humidity (>95% RH), freshwater mist, and saltwater mist (seawater @ 35 ppt) over periods ranging from 11 to 18-months. The entire study was conducted over a nine-year period. Changes in surface appearance varied among the components due to their elemental composition. The final study documented changes to galvanized steel pieces (i.e., garbage disposal bracket, electrical outlet cover, electrical junction box, flexible electrical conduit, and electrical conduit strap), steel pieces (i.e., sink fastener and face-mounted hinge), and one brass piece (SharkBite angle stop valve). The elemental composition revealed that the most corrosion resistance over the entire study was among nickel, stainless steel, and galvanized steel components. The least resistance was exhibited among those with a predominance of iron. The study concluded that careful examination of these components could provide insight into the duration of a water loss.

Alkali-silica reaction (ASR) is a common distress mechanism associated with certain aggregates in portland cement concrete. Small amounts of potentially ASR-reactive particles are common in many aggregates. These particles may or may not be destructive to the concrete as a whole, but ASR can cause distress to sensitive finishes even when present in small quantities in the near surface. Several cases of blistering of flooring related to ASR were investigated in Colorado and nearby states where the reactive aggregate contents were less than industry limits. The investigations revealed that the blistering of the flooring was caused by a relatively small amount of reactive particles located in the near surface concrete. However, there have been investigations where reactive particles were present in small quantities, but not causing distress. In this article, practicing forensic engineering professionals will gain a better understanding for the potential for this form of distress; how to properly identify the potential for ASR to cause distress of sensitive finishing materials through appropriate detailed field and laboratory evaluations; and potential implications if found.

An airfield pavement presented with blowups in the middle of the runway across multiple paving lanes. Damage occurred multiple times over a series for several summers. A condition survey was performed to identify typical distresses present in the pavement and investigate the causes leading to the failure of the pavement. Petrographic analysis of cores removed from the pavement identified the presence of alkali-silica reactive (ASR) gel and related damage in the concrete. The construction history was reviewed to identify the cause of the patterns seen in the blowup locations and review why the aggregate was not identified as ASR-reactive during pre-construction. Drainage of the base layers and the jointing layout plan were found to have had an impact on the location of the blowups throughout the airfield. Repairs were proposed with differing funding timelines including the installation of expansion joints to absorb future expansion and complete replacement of the ASR affected concrete.