Forensic Engineering 2015: Performance of the Built Environment

Evaluation and/or repair of existing concrete buildings can be challenging to design professionals, owners, building officials, and contractors. Difficulties arise due to a myriad of questions pertaining to the necessary extent of repairs, responsibilities during the project, and uncertainties regarding the governing code requirements. The concept of a building code for repair of existing concrete structures has been discussed for nearly thirty years. However, a major obstacle to the development of a concrete repair code was how it would interact with existing codes, such as ACI 318, general building codes and the International Building Code (IBC) that were developed primarily for the use during new construction. The development of the International Existing Building Code (IEBC) has provided design professionals a pathway delineating code requirements for repair and alterations of existing structures. ACI 562 was developed to work both with the IEBC and as a stand-alone code to provide design professionals a code for the repair of existing concrete buildings.

This presentation provides a rationale to substantiate the premise that for existing concrete buildings or concrete portions of existing structures the ACI 562-13 document as either a code, or as a standard, can be used as the applicable standard to assess damages. Hence it follows that within limits, if this premise is adequately substantiated, then ACI 562-13 may be used by engineering experts to formulate opinions and establish the basis of claimed damages when assessing current in-place conditions and recommending applicable rehabilitation work for structural concrete members and systems of existing structures. In Colorado, J. R. Harris & Company has recently used ACI 562-13 as a standard in several litigation reports assessing damages in existing concrete structures and on a single complex of four buildings for design and construction documents to rehabilitate deficiencies. ACI 562-13 is the current structural engineering state-of-the-art for evaluation and repair of existing concrete structures. As the current public and American National Standards Institute (ANSI) approved consensus standard, ACI 562-13 has been accepted as the source standard to use for damage assessment and repair on a project basis by two different local jurisdictional authorities in Colorado; this acceptance prompted our assessment reports recommending the remediation of the concrete and determination of damages using ACI 562-13.

Prior to the publication of ACI 562-13—Code Requirements for Evaluation, Repair and Rehabilitation of Existing Concrete Buildings and Commentary (ACI 562), an industry standard specific to repair and rehabilitation of existing concrete structures did not exist in the United States. Thus, practitioners frequently refer to codes for new concrete construction that could be more stringent than the code in effect at the time the structure was originally constructed resulting in additional and possibly unnecessary repairs. ACI 562 was developed to provide uniform code provisions and criteria coupled with extensive commentary that engineers can use in this kind of projects.

Evaluating the condition of existing reinforced concrete structures is generally undertaken if the integrity of a structure is in question or if there is concern regarding the structure meeting the safety requirements. Strength evaluation may be undertaken, for example, after extreme events (such as earthquakes) or if the structure will be used for a new function. In situ load testing may play a role in the evaluation process. Currently, the American Concrete Institute (ACI) covers in situ load testing in two separate standards: (a) ACI 318 “Building Code Requirements for Structural Concrete”, and (b) ACI 437 “Code Requirements for Load Testing of Existing Concrete Structures”. The latter is referenced by ACI 562 “Code Requirements for Evaluation, Repair, and Rehabilitation of Concrete Buildings”. In situ load testing methods include the application of a pre-determined load in combination with response measurements of the structure. The main response measurement is deflection, but rotation, strain, crack width, acoustic emission, and other measurements may be included. In this paper, the two aforementioned load testing approaches are compared and evaluated in terms of load test procedure, load magnitude, loading criteria, and acceptance criteria.

Water vapor within a building can lead to condensation on or within building envelopes via airflow/air leakage, vapor diffusion, and on exposed surfaces. Water vapor inside a building naturally equalizes between adjacent environments via diffusion, and because air naturally flows towards regions of lower air pressure. Each transport mechanism requires different design approaches, since vapor diffusion calculations are relatively straightforward but predicting air leakage is much more difficult and often depends upon construction and workmanship issues rather than simple material properties. Condensation on interior surfaces is a more visible issue than the often-concealed issues of vapor diffusion and air leakage, but can still be difficult to diagnose and resolve. This session presents multiple case studies and practical examples to demonstrate the nature of these issues and illustrates how design and construction issues can cause both short- and long-term problems. Specific issues such as exterior icing, condensation on fenestration, concealed condensation within interior and exterior walls, and deterioration/failure of roofing systems are discussed.

Many wood-framed buildings include exterior balconies in their designs. At these balconies, structural framing is often located in an interstitial space below the walking surface of the balcony, which typically places the wood framing in a poorly protected exterior portion of the building. This configuration requires that particular attention should be paid to the management of runoff from rain and incidental moisture at these structures. To be effective, the water resistive plane of the building envelope must be extended out to encompass this interstitial space and must be continuous around all elements that require protection. This paper will review case studies of buildings that have experienced water intrusion at these interstitial spaces and water intrusion’s impact on the wood structure that supports the balcony. It will also discuss the composition of the balcony assembly and the path water can take to cause damage to the structure below. The case studies will illustrate the hazards of improper design and installation of the building envelope, highlight the importance of directing water toward the exterior of the building, and discuss proper structural member selection. Current design practices will be considered and attention will be drawn to the damaging effects of improper waterproofing design and poor structural member selection/detailing.

Adhered masonry veneer (AMV), which is often used to create faux classical stone walls, has become popular over the past 20 or 30 years for exterior wall construction at commercial, retail, and residential building projects throughout the United States. The AMV is often a “manufactured” stone made from concrete that is formed and tinted to resemble natural stone. However, unlike classical mass masonry walls, contemporary AMV-clad exterior walls are prone to water infiltration and may be susceptible to other performance problems, such as loss of bond, cracking, displacement, or other failures that necessitates premature replacement. Preventing rainwater from penetrating and damaging the building interior or water-sensitive areas of the wall is the greatest challenge of AMV walls. While standards and building codes have evolved to mandate improved water penetration resistance properties and to address common known problems, AMV wall failures with major financial consequences still persist. This paper, which is based on the author’s more than 40 years of experience investigating wall failures, discusses common vulnerabilities and mistakes in design and construction of exterior AMV walls that increase the likelihood for failure.

The explosion of an oxygen tank within a patient room of a recently constructed hospital caused damage to the building’s facade, which consists of a stick-built aluminum-framed curtain wall with insulating glass unit (IGU) infill. Damage included permanent deformation and fracture of the curtain wall mullions. To minimize the scope of repair work that would disrupt the operations of a working hospital, a two-stage field investigation was performed by architectural and structural engineers working in collaboration with the original construction contractor’s personnel. First, to identify the minimum extent of framing replacement required to address structural damage, visual surveys and measurements of the interior and exterior surfaces of the curtain wall system were performed. Second, to test the hypothesis that the extent of glazing damage might exceed the extent of structural damage, in-situ frost point testing of IGUs was performed in accordance with ASTM E576, Standard Test Method for Frost/Dew Point of Sealed Insulating Glass Units in the Vertical Position, to determine whether the perimeter edge seals of IGUs were damaged in surrounding areas where curtain wall framing repairs were not required. The repair program included temporary shoring to maintain the structural stability of the partially disassembled curtain wall during replacement of damaged structural and glazing components, followed by water penetration testing on the repaired portion and surrounding areas, to verify the repaired system’s ability to resist water penetration. This paper will demonstrate how multiple engineering disciplines, with contractor support, can develop cost-effective and quickly implemented curtain wall repairs that avoid unnecessary replacement of undamaged components.

There are approximately 932,929 (almost 1 million) buildings within New York City’s 5 Boroughs. The NYC Department of Buildings (DOB) is a governmental city agency that regulates all buildings and has filing systems for each Borough. The DOB contains records on all the buildings from the time they were built, including any job applications or permits and/or violations that were issued for the block and lot of the building address.

In a recent construction litigation case, there was a disagreement between two qualified engineering experts regarding the technical requirements of a masonry veneer cladding system that was installed on the exterior walls of a residential structure. The disagreement among the experts was related to the classification and function of the veneer cladding system. Specifically, the classification of the cladding system as cast stone or adhered masonry veneer directly impacted the functional requirements set forth by applicable codes and standards. Depending on this classification, the veneer system may or may not be subjected to various aspects of the building code, industry standards, and code evaluation reports. The primary areas of concern included the attachment of the panels (i.e., anchored vs. adhered) to the masonry substrate, the extent of water intrusion and the need for water management details (i.e., flashing and weepholes). Both expert witnesses relied on applicable building codes, industry standards, and manufacturer literature to form their opinions to a “reasonable degree of engineering certainty”, yet these technical differences remained. This paper will present the technical highlights of this case study and identify the issues where the building codes and applicable standards require further clarification.

A recurring problem with detailing of stucco cladding occurs with the omission of an important flashing transition at vertical wall to horizontal junctures at soffits, beams, and recessed heads of openings. The problem is the absence of a drip flashing which results in a high potential for water infiltration – leading to building leaks and structural deterioration. The problem condition at stucco covered beams is referred to as a “stucco bucket” and occurs in both wood-framed and light-gage metal framed buildings of low to mid-rise height – the typical residential and light commercial structures found throughout the United States. The stucco configurations of beams, soffits, and recessed openings reviewed are common to this type of building design from the early 1960s and continuing to the present. Examples of detail failures are analyzed and the current stucco application techniques are described; together they cause the repetition of stucco problems. Stucco industry standards with incomplete guidance are discussed. What we believe designers and builders should know is illustrated herein with new details and solutions for effective flashings using available stucco accessories and improved installation techniques.

Damage to buildings adjacent to construction sites in congested or urban environments often results from improper construction planning, methodology, and sequencing. The resulting costs associated with damage mitigation and repairs, schedule delays, altered construction approaches, insurance claims, and potential litigation often affect all involved parties. Properly interpreting the distress that occurs during adjacent construction is a critical step in understanding what activities contributed to or caused the damage. Specifically, being able to understand the expected building behavior, as well as to correlate the observed distress and mechanisms to the type and extent of the construction activities are keys to identifying the underlying cause of the damage. This paper focuses on forensic engineering aimed at understanding, diagnosing, and opining on damage caused by construction types often associated with the most severe adjacent-property damage: earthwork and foundation activities. Typical distress to adjacent structures is discussed, as well as the mechanisms that cause damages. Risks associated with general excavation, earth-support systems, drilling and pile driving operations, dewatering, and underpinning are also discussed. The authors draw on their experience of investigating numerous claims of reported damage due to adjacent construction in New York City.

It is anticipated that structures sitting atop shallow foundations will experience some degree of initial displacement from near surface soil consolidation and/or initial settlement. This paper however focuses on diagnosing one of the causes of displacement that result well after these initial displacements have occurred. In particular this paper focuses on damage contributions from the loss or instability of soil from within a foundation’s influence zone. This paper begins by first identifying a foundation’s influence zone; identified as those soils directly affecting the structure by acting to support and resist its loads. This paper demonstrates how the Boussinesq method, a pre-construction design tool used to calculate the zone of influence (the zone of soil effected by the structure), has been reconfigured for use as a post-construction analysis tool to determine the extent of the foundation’s influence zone, (the zone of soil directly affecting the structure). The reconfiguration consists of breaking down the basic equation and plugging in known values to solve for and ultimately determine the influence zone. This paper concludes by outlining those damages most likely to result from a loss or instability of the soils within a foundation’s influence zone.

Ground vibrations generated by construction activity, including pile driving, have the potential to cause damage to nearby structures. Determining the expected vibration levels at a project site can become an important aspect in planning construction projects. There are several parameters that affect the expected vibration levels, including the distance from the source, the site specific soil conditions, and the pile installation method. Due to the variability in soil conditions, site specific investigations are often required to determine ground vibration characteristics. An investigation into ground vibrations due to pile driving was initiated by the Alabama Department of Transportation (ALDOT) at a project site near the Mobile River, just south of downtown Mobile, Alabama. The investigation included the installation of one concrete pile and two steel H-piles that are commonly used by ALDOT. The soil conditions at the project site predominantly consisted of dense, gravelly sand. The vibration monitoring program that was developed consisted of measuring ground vibrations at a horizontal distance of approximately 50, 100, and 150 feet from each pile. The largest vibrations observed throughout the project were at 50 feet from the concrete pile. As anticipated, the vibration magnitude was significantly reduced at 150 feet from the pile. The vibration data obtained from the project was used in conjunction with existing vibration prediction equations to potentially use in future construction projects at this site.

Deep seated slope movements can manifest as small, slow movements and be defined as slope creep. Over a period of time, enough movement can occur that results in damage to property and structures. Site reconnaissance alone cannot identify slope movement along a deep seated shear plane and can occur at depths greater than explored by test borings, especially for lightly loaded structures. This case history discusses a site in upstate South Carolina that experienced two episodes of slope movement between December 2009 and January 2014. Subsequent to a $3.5 million legal claim that a “slope failure” caused damage to a house, the defendant’s expert witness team developed an exploration and laboratory testing program to help determine the cause of the slope movement. Observations made during site reconnaissance are presented and the subsurface conditions revealed by the field exploration programs are described. Evaluation of inclinometer data is shown to disclose a deep seated slope movement that was not contemplated during initial site characterization. The data indicated that the slope moved intermittently and was very slow. Lastly, triggering mechanisms that potentially initiated the slope movement are presented. Inclinometers typically thought of as an instrument for monitoring slope performance, not as an exploration tool, were proved essential for use in site characterization in detecting the deep shear plane. Failing to reach an eleventh hour settlement, the case went to trial. The jury found in favor of the defendant, ruling that they were not negligent during their initial site characterization.

Given that concrete masonry walls are subject to shrinkage and thermal expansion and contraction throughout their life, cracking is to be expected. However, after concrete masonry walls have been placed into service, originally anticipated cracking is often perceived as damage. By its nature, this type of cracking does not constitute damage in that it does not typically compromise structural integrity. However, in some cases originally anticipated cracking is perceived as a structural concern resulting in unnecessary structural remediation. Therefore, properly diagnosing cracking in concrete masonry walls and not confusing originally anticipated cracking with structural damage can serve to prevent unwarranted concern and unnecessary remedial efforts. This paper begins by introducing the most common causes of cracking within concrete masonry walls; shrinkage and thermal expansion and contraction along with means of calculating the amounts of cracking to be anticipated. It then focuses on the types, locations, and configurations of cracking to be anticipated. This paper concludes with a discussion on the process of evaluating cracking through the use of crack mapping so as to establish relationships to originally anticipated cracking and avoid the misdiagnosis of cracking.

The article presents the investigations, carried out by the technical consultants of the Criminal Investigate Magistrate, relevant to partial collapse of the so-called ‘Palazzo Edilizia’ occurred in Salerno (Italy) on the night of June 15, 2007.

There are many reasons that engineers and architects find it necessary to complete masonry repairs to facades while having minimal impact. For reasons such as preservation of the intact original historic fabric of the facade, lack of acceptable replacement materials, project schedule, or other cost prohibitive conditions, an alternative but reliable repair may be desirable. Non-destructive helical bar reinforcing can often be considered as a dependable and efficient means of rectifying and reinforcing many potentially serious deficiencies in masonry walls that may otherwise result in large-scale replacement of areas of the façade. This paper presents the advantages and disadvantages of helical bar reinforcing and describes how utilizing such alternative repair methods may offer a means of repairing existing masonry walls without removing a single brick. A comparison of helical bar reinforcing to brick replacement and rebuilding is discussed. What is the process of non-destructive helical bar reinforcing? What are typical difficulties confronted when performing this type of repair? What results may be expected from helical bar reinforcing? These questions will be discussed and three case studies of historic and landmarked buildings will be presented - one low-rise residential building and two high-rise commercial buildings, all in New York City. This paper discusses how incorporating non-destructive helical bar reinforcing into the repair of historic masonry facades can aid in the repair of masonry buildings while having a minimal impact on the façade.

A four story building in South Orange, New Jersey, originally constructed in the 1950s underwent an expansion in 2006. The expansion involved a 4 story addition to the east side of the building. The addition’s façade included limestone panels over concrete or CMU back- up walls, and a glass curtain wall. The limestone panels were 1 ¼ inches thick, and supported on anchors that were inserted into kerfs on the panel edges. In the spring of 2009, the following conditions were noted at some limestone panels: spalls in the vicinity of the stone anchors and cracks in some of the façade mortar joints. In July 2010, the writers’ firm was retained to perform an engineering evaluation into the cause of the observed conditions and to evaluate the roles and responsibilities of the various parties. As part of our work, we reviewed design drawings, specifications and shop submittals, and performed site inspections before and during panel removal. We found that the primary cause of the spalling of the stone at the kerf anchors was the lack of soft joints between the stone panels, which prevented the stone from being able to accommodate normal building movements, such as concrete creep. This paper will set forth the results of the investigation, the engineering cause(s) of the failure, the contributing factors, and recommendations for future thin stone façade construction.

When a water loss damages a home and insurance coverage is anticipated, the investigator is often asked a critical question, “When did the loss occur?” Water losses frequently damage cabinetry because composite wood products (i.e., particle board) are vulnerable to thickness swell (TS). TS occurs when composite wood products absorb free water and distort in response to absorption and the release of compressive forces. The study examined five factors that influence TS: product thickness, binding adhesive, presence and type of a coating, surfactants, and particle board density. Multiple panels (unfaced, vinyl-faced, and melamine faced) were measured for the vertical moisture absorption under conditions of constant moisture exposure, elevated relative humidity (>94% RH), and slight elevated room temperatures (77–81°F) over periods from two to four months. The test results revealed that some circumstances offer a reliable technique to estimate the duration of a one time, continuous water loss when combined with other facts and observations.

Thickness swell (TS) occurs when wood materials absorb moisture and as a consequence create pressure. This study examines the pressure generated following moisture absorption among eight common wood materials using modified methods from ASTM Standard E831 & D1037 to measure the normal swelling pressures as moisture content changed (psi [MPa]). Most test samples expressed maximum pressure after 48 hours. The results showed average maximum pressures were achieved by the medium density fiber board (MDF) (144 psi [0.992 MPa]) while the lowest was gypsum board (5 psi [0.034 MPa]). Comparison of the average maximum values revealed the highest pressures were derived from composite wood products (78 -144 psi [0.538-0.992 MPa], MDF, particle board and oriented strand board) when compared to laminate and solid wood products (57-65 psi [0.393-0.448 MPa], interior and exterior plywood and pressure treated pine). The results can support forensic investigations and the interpretation of building component failures.

Failure analysis of heat-treated glass (tempered or heat-strengthened) is often complicated due to the location of the glass in service, manner in which the glass fails, and number of potential causes of failure. Indirect methods of analysis involving intact panels or systems may provide insight into the cause of failure; however, direct analysis is possible if the failure origin can be located. Due to internal stresses in heat-treated glass, failure results in fracturing of the entire panel creating hundreds or thousands of individual pieces. While the identification of the failure origin pieces from the glass debris can be a challenge; it is feasible to identify the failure origin pieces from failed glass if the evidence is properly collected and maintained. Methodology and case studies discussed herein outline possible methods for preserving, collecting, and/or testing glass debris and other evidence after a failure has occurred, recovering fracture origin pieces from debris, and identifying potential causes of failure from the fracture origin if recovered. The purpose of this paper is to educate the engineering and scientific community regarding the preservation of glass evidence and the methodology for locating fracture origin pieces when evaluating heat-treated glass failures.

Alkali-silica-reaction (ASR) cracking in concrete is one of the primary concerns in the structural integrity assessment of concrete infrastructures. Therefore, characterizing the susceptibility of concrete to ASR and ways to address this issue is crucial in the design of concrete structures. In this paper, electrical resistivity measurement was used to study ASR in mortar containing reactive aggregate and correlated with the mortars’ expansion. Mechanical strength tests and microscopic examination were carried out to obtain an understanding of the effect of ASR on the mortar strength and microstructure. Control mortar and mortar with glass powder as a supplementary cementitious material were prepared and used for comparison. The results indicated that ASR cracking in the microstructure of the control mortar significantly affected electrical resistivity and resulted in a degradation of the mechanical strength of mortars. It was shown that glass powder modified mortar was resistant to ASR expansion and alkali binding was a primary mechanism mitigating ASR in the glass modified mortar.

Masonite shingles, aka Woodruff shingles, are wood composite simulated shake shingles that were popular in the mid-1980s to mid-1990s. Woodruff shingles reportedly had good impact resistance when they were new, but due to product defects their actual hail-resistance performance has been questioned. This paper reports on Woodruff shingle field observations after hail events, and hail impact testing performed on aged Woodruff shingles in a laboratory setting. The main body, shiplap edges, and grooved areas of shingles were impacted. Hail stones of varying diameters were launched at Woodruff shingles, and then the impacted shingles were returned to the natural environment and monitored for four years to study the effect, if any, of the hail impacts. The testing conducted showed that hail stones of 1-3/16 inch diameter, or smaller, did not damage the shingle when they struck the main body and groove areas. However, laboratory tests determined that hail stones of 3/4 inch diameter could damage the shiplap edges of the shingles, and field observations confirmed that hail as small as 1/2 inch diameter could potentially damage the same. Also, many in the roofing industry have theorized that hail impact locations that showed no immediate damage to the main body of the shingle could result in accelerated weathering over time. To-date, the hail impacted shingles have been monitored for four years and there have been no signs of accelerated weathering.

Forensic evaluation of roofing membranes for hail damage is a large and growing industry throughout the United States, especially in the Midwest and across the South where hailstorms are prevalent throughout the year. For these evaluations, accurate assessment of the roof membrane and the causation of damage is an imperative. An accurate assessment requires knowledge of the potential causes of damage for the roof system, including determination of damage related to hail impact. Laboratory testing of membrane samples is often an important component of such an evaluation. Damage resulting from interply mopping voids, which are as-built conditions, is often misidentified as hail damage in multi-ply bituminous roof membranes. This misidentification frequently occurs because the characteristics of distress to the membrane surface caused by interply mopping voids can be similar to the characteristics of membrane surface distress caused by hailstone impacts. The purpose of this paper is to educate readers about interply mopping voids and the type of distress that they can cause. Examples involving roofing membrane samples cut from various structures and analyzed in a laboratory will be used to illustrate interply mopping voids and the damage that results from their presence. Finally, this paper will outline ways to better distinguish hail impact distress from interply mopping void distress when performing a forensic roof evaluation in the field.

Masonite shingles, aka Woodruff shingles, are wood composite simulated shake shingles that were popular in the mid-1980s to mid-1990s. Given these shingles are no longer manufactured, finding shingles to perform repairs to wind damaged roofs are difficult and in many cases a single missing shingle can trigger an entire roof replacement. The field shingles are less likely to be removed by wind; however, ridge cap shingles are fairly susceptible. This paper reports on destructive testing performed on 17 year old masonite ridge-cap shingles. The testing utilized a force meter to remove both well secured, and not-so-well secured, masonite shingles in order to gain an understanding of the forces required to remove the ridge cap shingles. Further, the withdrawal capacity of each roofing staple was determined from the test data and compared to values calculated from the National Design Specification for Wood Construction. The uplift force results were also translated to an equivalent uplift pressure and compared to the uplift pressures generated by winds on traditional residential roof configurations as calculated with ASCE-7 – Minimum Design Loads for Buildings and Other Structures in an effort to correlate required wind speeds to remove masonite ridge cap shingles.

Sagging roof surfaces and broken sub-purlins can be the result of construction defects to wood panelized roof systems; however, roofs with no signs of failure or distress may still be degraded to the point of detachment and failure. Although a detachment of an individual purlin may not result in the collapse of the roof or even a portion of the roof, it may represent a potential life safety hazard to the occupants of the building. This paper will discuss the design, construction, and failure of a sub-purlin hanger at a large warehouse that resulted in the investigation and remediation of over (370,000 square meters) 4 million square feet of warehouse roofs. This paper will present the viewpoint of an investigator working for the building owner/developer (WJE) and the viewpoint of an investigator working for the roof framing subcontractor’s insurance company (DC). The factors involved during the original design and construction will be discussed as well as the methods used to determine the adequacy of the remaining sub-purlin hangers. Although the paper does not offer a formula for identifying hidden failures, it demonstrates that a process can be implemented to reduce future sub-purlin hanger failures to an acceptable level.

On the evening of November 10, 2012, a natural gas explosion occurred in the Richmond Hill subdivision on the south side of Indianapolis, Indiana, causing two deaths and extensive property damage. The source of the explosion was from one house at a central location in the neighborhood. The explosion destroyed this house as well as a neighboring home, where the two fatalities were found. The event was widely publicized and garnered national attention. At the time that this paper was written, five individuals remained in custody on various legal charges related to the incident. The Richmond Hill subdivision comprised 125 wood-framed, single family houses, 16 of which were inspected by the authors of this paper. The houses in the neighborhood were of similar construction built by a national home builder. The purpose of this paper is to share the authors’ experience in this investigative effort, with a focus on the type and extent of damage found in the homes that surrounded the explosion source.

The West Fertilizer Company (WFC) explosion, which occurred on April 17, 2013, resulted in varying degrees of damage to many residential and commercial structures. The author’s firm performed evaluations of 35 structures reportedly damaged by the explosion, with locations ranging from approximately .1 miles to over 5.5 miles from ground zero. The evaluations were collectively reviewed for identification of consistent distress mechanisms at the structures and global patterns of distress propagation in relation to distance from the explosion origin. This paper studies the respective performance of the evaluated structures subjected to the WFC explosion, particularly in relation to distance from the explosion site. In addition, the distress patterns from the WFC explosion evaluations are compared to published data referencing expected distress to building components relative to superimposed pressure. The comparison is used as a basis to establish a methodology of explosion investigations considering “damage indicators” in relation to relative distance from an explosion source.

A natural gas explosion in East Harlem, NY destroyed two buildings and caused breakage of windows on a building across the street from the explosion. The equivalent TNT charge of the explosion is estimated and used to develop an explosion-fragment model (EFM) of the explosion event. The EFM is employed to investigate the potentiality of the window breakage as being caused by fragment impact or by the blast shock wave itself. Sections of the building facade predicted to be vulnerable to a combination of fragment impact and the shock wave are found to correlate with slightly higher rates of window breakage than sections predicted to be vulnerable only to the shock wave.

Erection and bracing of column reinforcing cages are often left to the contractor’s means and methods. As such, the stability of these cages is often based on empirical methods and past practice, and thus, rarely determined based on engineering analysis. Cage stiffness is a result of composite action of the complicated combination of longitudinal bars, transverse reinforcing, and wired joints, thus making an accurate calculation of the buckling strength quite difficult. To further complicate matters, typical construction practice may require ironworkers to climb these potentially unstable cages. Current literature does not provide engineers with practical methods to assess the stability of these cages. For example, how one chooses to simplify the complex bar layouts into an assemblage, which can be easily modeled can lead to very different (and potentially unconservative) results. Using collapse case studies as an impetus, this paper expounds on a previous paper by the authors to explore the accuracy of different simplified models and analysis methods to assess cage stability for cages with ironworkers present. Finally, a brief discussion concerning required cage bracing forces is provided.

This paper presents a partial collapse of a building that occurred during construction. The subject building was a five-story residential building measuring approximately 48 feet by 80 feet in plan. The structure of the building consisted of concrete floors on metal deck supported by exterior light gage steel stud walls and interior steel beams and columns. The collapse occurred when the concrete placement for the fourth floor was being performed. Approximately half of each of third, fourth, and fifth floor collapsed, causing a fatality. The authors were retained immediately after the collapse on behalf of the owner and the general contractor to investigate the cause of the collapse. This paper presents the extent of the collapse and the deficiencies in the design and the construction of the light gage steel stud wall system. This paper also provides recommendations to the owners, engineers, and contractors to prevent the occurrence of similar building collapses.

The drainage of low-sloped roof systems involves multiple design professionals, and often each has a different opinion as to their design responsibility. Roofing issues have been identified as being a number one source of litigation, and rain-induced roof collapses continue to occur with alarming frequency. With the backdrop of several rain-induced roof collapses, this paper illustrates the complexity of assigning design responsibility for drainage systems; and investigates a variety of outcomes associated with the current building code provisions transporting rainwater from large low-sloped roof structures.

Even though each construction failure is to be regretted, each failure provides information that may be used to prevent similar failures. The systematic investigation of construction failures helps advance the science of construction and building regulations. The results of such investigations identify errors to be avoided and contribute to increase the safety of future designs. Each construction failure points to a gap either in theory or practice and thereby fosters innovations. The present paper discusses several effective, mutually reinforcing methods to prevent construction failures. Among them are: macroscopic (i.e., statistical) analysis of large samples of construction failures, microscopic (i.e., case study) analysis of individual construction failures, collaborative design, design-construction reviews, peer reviews, monitoring, and the transfer of safety management methods, such as incident reporting systems, from risk-conscious industrial sectors, e.g., aviation, to construction.

Gravel ballast from the built-up roof of a 9-story tall building became windborne during the passage of Hurricane Wilma in Miami and impacted a 26-story tall building immediately downwind of it. Flight of roof gravel from the upwind 9-story building was further aided by the lack of a rooftop parapet. The 9-story upwind building was located along the shoreline of Biscayne Bay providing Exposure D conditions for the approaching hurricane force winds at the peak of the storm. The horizontal separation between the two buildings was less than 60% of the across-wind dimension of the shorter upwind building. Impact by the wind borne gravel caused extensive damage to the glazed fenestrations of the 26-story building. The relative position of these two buildings and their orientation to the oncoming direction of the peak winds during Hurricane Wilma played a significant role in the resulting damage to the high rise building’s glazing. A detailed investigation of the hurricane damage sustained by the 26-story building was performed by the author. This investigation revealed that the high-rise building lost more than 200 pieces of exterior glazing as a result of direct wind-borne debris impact from the upwind building during Hurricane Wilma. Broken exterior glazing caused pressurization of the building’s interior and pressures on light-framed partition walls far in excess to what they were designed for resulting in severe damage. Interior pressurization caused a direct increase in internal pressures which resulted in fenestration components on building facades not directly exposed to the wind-borne debris strikes to be subjected to higher pressures when compared to an enclosed building and caused additional failures. Details of this assessment are presented in this paper.

At the first forensic engineering congress, shortly after investigating damage to residential structures from Hurricane Andrew, I presented a paper on the shortcomings of the prescriptive building code. Specifically, I argued that a prescriptive code is typically based upon past experience, that this experience is out of date as soon as it is acquired, and that prescriptions will always break down at the margins of design innovation. I concluded by proposing that all residential structures in areas of severe hazard be engineered to withstand the expected loads. As noted, Hurricane Andrew damaged houses throughout southern Dade County, Florida. Despite a strict building code, after a 31 year hiatus from major hurricane damage, the region’s housing stock proved much more vulnerable than expected. However, setting aside the prevalence of lost roof covering, broken windows, and the complete destruction of mobile homes, relatively few wood-frame houses suffered severe structural damage. Consequently, those that did suffer damage became objects of intense investigation and engineering scrutiny. The results of that scrutiny included changes to the Building Code. While these changes are welcome and necessary, they repeat the historical pattern of codifying elements necessary to fix problems observed in the housing stock that suffered damage. Among these, damage to gable- end walls stands out among issues that led to Code revisions. Presently, with an additional 23 years of experience since Hurricane Andrew, and with more recent experiences from other storms, Florida retains a largely prescriptive Residential Building Code. However, for High Velocity Hurricane Zones, the Code directs the building designer to use the performance standards of the Florida Building Code for Buildings, based upon the International Building Code. Therefore, at least for those areas considered to be High Velocity Hurricane Zones, Florida does not allow for the use of the prescriptions contained within the Code. This paper reviews the Code evolution briefly, and revisits the question of whether and how well a prescriptive code can adequately insure the integrity of residential structures in Florida.

For over 20 years, the Federal Emergency Management Agency (FEMA) Mitigation Assessment Team (MAT) has studied the performance of buildings affected by disasters of national significance. Following Hurricane Sandy, the MAT supported community resilience through changes to the building codes that evolved directly from lessons learned from that disaster. FEMA P-942, the Hurricane Sandy MAT report, contains 47 observation-based recommended actions related to building codes and standards. To date, 28 have been partially or fully enacted and others are under consideration. Successful examples include: modifying New Jersey’s building code to refer to ASCE 24, Flood Resistant Design and Construction, for all buildings on pile foundations, adding a requirement for flood zone special inspections in New York City, and consideration of adding a requirement of 2 feet of freeboard (additional height above design flood elevation) for the elevation of non-residential buildings in New York State. This paper includes information on how the Hurricane Sandy MAT observations and recommendations have supported building code changes, leading to stronger building codes and more resilient communities.

In the early morning hours of December 25, 2012, an EF-2 tornado passed through midtown Mobile, Alabama, causing damage to numerous buildings, including the Trinity Episcopal Church. The church, which was originally constructed in 1853 and moved from downtown Mobile to its present site in 1946, suffered severe structural damage. A large section of the roofing and supporting solid sawn lumber rafters along the east side of the church were detached from the building. The tornado also displaced several heavy timber roof trusses and purlins, partially fractured several heavy timber columns supporting the roof trusses, and partially fractured several of the remaining rafters. The authors completed an investigation to evaluate the damage and determine whether the existing wood structure could be repaired. The examination revealed partial fractures of the wood columns, particularly those along the east side of the building and relative displacement of the roof trusses with respect to the tops of the columns on the west side. As part of the authors’ investigation, the wood elements were visually graded and wood samples were removed for species identification. Structural analyses were performed of the as-built wood structure using 3D computer models, in conjunction with hand calculations to determine whether repairs were feasible. This study, determined that repairs were feasible, and due to the complexity of the repairs, in-depth construction administration services were provided. Repair installation commenced in late summer of 2013 and was completed in the spring of 2014. These structural repairs helped to preserve the history and original aesthetics of this historic church.

In performing a forensic investigation of a building, it is essential for the structural engineer to use personal experience and education, technical publications and reports describing the research performed, and experience of others. This valuable material is referred to in Bayesian structural reliability theory as the basis for a priori estimation of a value for a parameter used for structural analysis computer modeling, or a limit state capacity, or the demand on a limit state. Bayesian theory recognizes that the expected value (mean) and the standard deviation of a random variable are themselves random variables with their own expected values and standard deviations. This paper will describe how the language of structural reliability and a priori, and then using field and structural component laboratory testing plus structural mechanics based structural analysis models to greatly benefit a forensic investigation by developing a posterior estimate. The motivation for the work presented in this paper was from the members of the Evaluation and Strengthening Committee of the Los Angeles Tall Buildings Structural Design Council.

Finite element analysis can be a useful tool for structural failure investigation. It enables engineers to compare and quantify potential failure modes and it allows interested parties to visualize failure sequences. Finite element analysis is used less frequently for support of structural failure investigation than it is for design and there are several important differences. In design, it is typically sufficient to make conservative assumptions; in failure investigation, conservative assumptions may preclude potential failure modes. Therefore, it is important to characterize every aspect of the model as accurately as possible, thoroughly check assumptions, and understand the limitations of the model. This is especially true for nonlinear analyses, where models may be sensitive to small changes. For situations where the structure cannot be adequately characterized, finite element analysis may still prove useful by identifying trends resulting from variation in certain parameters that may have contributed to failure. Two case studies are presented to illustrate the advantages and pitfalls of finite element modeling in structural failure investigation: collapse of a mast-climbing scaffolding machine and deterioration of concrete railroad ties.

With recent advancements in computers, instruments and computer programming technology, the implementation of three-dimensional (3D) documentation now is becoming a standard for forensic analyses of high cost incidents and incidents involving fatalities and severe injuries. The combination of precise measuring systems and high-performance imaging scanners allows efficient and cost-effective coverage of incident areas. Rather than just collecting data describing areas of immediate interest, 3D imaging acquires data defining the entire scene, information which may be important several years later, particularly during a trial. Whether it is a motor vehicle accident, building collapse, crane accident or another large scale catastrophe, recent advancements in 3D technologies are providing quickly unprecedented quantities of valuable information to the forensic engineering industry. This paper explains 3D imaging functions, its accuracies, its limitations, required office processes, and ultimate products (deliverables). It also includes provider qualification information, professional credentials requirements, and comments regarding acceptance in legal settings.

Reliable crack dating methods are needed to determine potential causes of cracks in construction materials. Two methods are evaluated for their viability in the US courts: carbonation crack dating and biomass crack dating. Both methods show promise in providing a defined timeline of exposure for cracks, which can lead to links in potential causation. Such methods provide promise in better understanding what causes cracks, and potentially, who may be liable for them.

This paper presents a practical approach to estimate the contribution of individual earthquakes in a seismic sequence to the overall damage sustained by a structure. In this approach, a single degree of freedom (SDOF) model of the structure with a nonlinear capacity curve is subjected to a sequence of ground acceleration time histories. Structural response of this model is then used to develop a measure of contribution of each earthquake to the overall structural damage. The capacity curve is developed using the procedure outlined in FEMA’s methodology for estimating potential losses from earthquakes (HAZUS-MH) and ASCE 41-13. The SDOF model accounts for both stiffness and strength cyclic degradation as well as second order effects in the structure’s response during strong ground motions. New Zealand’s Canterbury earthquake sequence of 2010–2011 is used as the base excitation for a case study. Ground motions from the recording stations closest to the subject building are combined to produce a single sequential event in the same order as they occurred. A comparison of dissipated energies at the end of each earthquake event yields the relative contribution of each of the earthquakes to the total energy dissipated by the structure during the entire earthquake sequence. The amount of dissipated energy in the structure directly correlates to the damage sustained by various building components as earthquake energy is dissipated through the cyclic inelastic actions of the structure. This analysis can assist forensic investigation by providing information on the damage state of the building after prior events for which an inspection was not performed or there is little or no documentation of damage. In addition, it can serve owners as well as the insurance industry to resolve disputes over insurance claims.

High wind events occur every year throughout the county including tornado alley, the coastal regions and the high elevation valleys of the Rocky Mountains. Less substantial but still damaging winds are even more prevalent throughout the county. Millions of dollars of damages result and subsequent insurance claims are filed by property owners. Damages range from catastrophic collapses to minor roofing damage and disputes regarding the extent of damage regularly ensue. This research focuses on uplift forces generated on common residential roof configurations and testing and analysis was performed in a wind tunnel and via computational fluid dynamic (CFD) software. 3D printing has simplified and reduced the cost of conducting wind tunnel testing using models of residential structures as allowed in ASCE 7. The experimental testing performed was completed in a wind tunnel with 1:120 scale model houses. Each roof was fitted with 48 pressure taps which allowed researchers to note the pressures at specific locations and to calculate the overall lift coefficients for each roof type. Analytical and experimental testing was conducted on various roof structures including residences with gable, gambrel, mansard, hipped, and shed-style roofs. During the tests, the exposure orientation of the residential models to the wind direction was altered in order to find the wind direction which yielded the highest lift coefficient. A comparison of the test results to the wind pressures calculated in ASCE-7-10 was conducted and schematics provided as to the relative uplift pressures at each region of the roofs.

Finite element analysis was used to investigate the effects of the misalignment of the brace flange-to-beam connection point with the link-end stiffener on the ductility of the EBF frames. The misalignment was speculated to be a possible reason for the unexpected EBF failures observed in the aftermath of the Christchurch earthquake series of 2010 and 2011. EBF models with different detailing at the offset area were analyzed under monotonic and cyclic displacements. Results showed severe stress and strain concentration in the offset area, preventing the EBF from developing its expected ductility, and suggested possible initiation of a failure from the part of link flange located in the offset area. Results from analyses on different detail configurations showed that removal of the offset by modifying the brace section to build an ideal case, or by a simple change in the location of the link stiffener, can mitigate the problem of possible premature failure, with the latter solution being slightly less effective but much easier to be used in practice.

Fire following an earthquake has been a major cause of damage in a number of historic seismic events. Considering the amount of damage and statistics showing a high probability for the occurrence of post-earthquake ignitions, there is a need to study the effects of seismic damage on the fire resistance of structures. This research studies the resistance and failure behavior of Concrete Filled Double-Skin Tube (CFDST) columns with both experimental and numerical methods. CFDSTs are categorized as a special composite structure which has been shown to have satisfactory performance under separate seismic loading and fire conditions. Comparison between the fire resistance of different CFDST columns with various degrees of simulated seismic damage provided evidence for the overall resilient performance of these columns under post-earthquake fire scenarios.

On 19 December 2008, a large portion of the S-shaped, steel-framed walkway under construction at the Atlanta Botanical Gardens suddenly collapsed during concrete placement operations. The approximately 575 ft long cable-stayed canopy bridge was designed to be supported by four masts along the curved spline segments and two opposing inclined columns at the transitional straight spline segments. At the time of collapse, the walkway structure was supported on temporary shoring tower frames and helical piles. A detailed study of movement and structural behavior was used to investigate the cause of collapse. Construction photos made it possible to compare erected locations of shoring tower frames and grillage members with their post-collapse locations and stacked configurations. Spline impact marks on the ground and shoring members below showed varying degrees of post-impact translation at points along the length of the collapsed walkway structure. Type and directionality of bolt failures at spline beam splices and abutments, and angles of inclination of shoring tower support piles above the ground surface were also considered. The movement displayed in these various elements pointed toward likely locations of collapse initiation among the numerous shoring towers. This study of movement allowed for a focused investigation to establish probable cause of the collapse.

The U.S. Department of Defense (DoD) mandates progressive collapse protection for all new military buildings that are three or more stories in height. Detailed information regarding acceptable design approaches are provided in relevant Unified Facility Criteria (UFC) documents. These documents are periodically updated as needed. Initially, when UFC progressive collapse criteria were released post-9/11, the extent of protection was typically limited to the building exterior. In 2009, the extent of protection became more dependent on internal security measures. Specifically, internal areas designated as ‘unsecured’ required progressive collapse protection. Because the term ‘unsecured’ is not well defined, this requirement can cause cost increases to a project if not resolved at the earliest opportunity. In this paper, a legal dispute concerning the extent of the progressive collapse protection required for a military facility is used as a case study to illustrate the issues that can arise. UFC requirements and documents pertaining to the acceptable methods of progressive collapse and the locations of this protection are outlined.

The possibility of a local structural failure to propagate into a global collapse of the structural system has fueled the continued development of improved computational methods to model building behavior, as well as “best practices” engineering standards. In spite of these efforts, recent events are bringing the issue of collapse mitigation to the forefront and highlighting the shortcomings of existing design practices. The catastrophic nature of structural collapse dictates the need for more reliable methodologies to quantify the likelihood of structural failures and strategies to minimize potential consequences. This paper presents the results of a stochastic nonlinear dynamic analysis study of a simple structural model to predict catastrophic failure. The performed analysis indicates that, at the point of incipient failure, uncertainties associated with the analysis become increasingly large. Consequently, it may not be possible to accurately predict when (and if) failure may occur. Recognizing the need to understand uncertainties associated with risk and probabilities of unlikely events (low probability and high consequence events), this paper sets the stage to better understand the limitations of current numerical analysis methods and discuss innovative alternatives.

Computer solutions to model disproportionate collapse require consideration of dynamics, large deformation, and yield. This presentation provides fundamental first principles approaches to solving these problems using some mechanics and spreadsheets.

This paper presents the review of an evaluation and strengthening study of a tall reinforced concrete building that was performed approximately 11 years ago. This review focuses on how in a transparent way structural reliability incorporates site specific experience from: estimation of earthquake ground motion time histories, non-destructive and destructive field testing, a nonlinear time history structural dynamic analysis that was peer reviewed, and required structural observation during the strengthening. The building is an ordinary concrete frame building, designed and constructed in the 1970s. A set of structural building plans did exist but no structural calculations and construction testing/field notes exist.

The subject of this paper is a case study that involved construction defects of reinforced concrete walls placed using insulated concrete forms (ICFs). The building is a 58,000 square foot two story facility. Shortly after construction of the perimeter walls, it was discovered that the reinforcing bars had not been placed per the design drawings and that there was extensive honeycombing of the concrete. This led to the stripping of all the insulation on both sides of the wall, repairs to the concrete, and the widespread installation of carbon fiber reinforced polymer strips. This resulted in substantial additional cost to the project, and delayed the completion of the project. We were retained on behalf of the surety for the design-builder to investigate these deficiencies, to determine if these deficiencies warranted widespread repairs, and to evaluate if the type of repair specified was appropriate. The matter went to mediation, arbitration, and it eventually settled. This paper presents these defects, the effects of the defects, as well as the studies conducted to identify the defects and the actions taken to repair the defects. It also discusses the adequacy of the design drawings, of the shop drawings, and of the quality control. This paper also provides recommendations to the engineers and contractors to minimize the occurrence of concrete and reinforcement construction defects.

Wheeled traffic has the potential for inducing large compressive and shear stresses in concrete for industrial floors. The authors look at the performance of industrial concrete floors taking into account the principles of contact mechanics and the influence of the hardness and abrasion resistance of the concrete. Concrete floor specimens were tested for abrasion resistance. The effect of the inclusion of metallic surface hardeners, liquid hardeners, and macro-fibers is reviewed. This paper evaluates the various issues related to floor capacity and performance under moving wheel loads and intends to provide good engineering recommendations for safe working designs of industrial concrete floors subjected to moving loads on casters and wheels.

A parking garage constructed using precast double tees supported by structural steel experienced an overload condition from snow removal operations that resulted in severe cracking and localized failures. Structural analyses of the affected members revealed insufficient shear reinforcement in the precast concrete shallow dapped end regions. Subsequent surveys revealed a significant number of additional cracked double tees. An inspection and testing program was developed to assess the ability of the as-built double tees to resist code-prescribed loads. The program included ground penetrating radar (GPR) to locate reinforcement on a statistically relevant sample and full-scale load testing on selected double tees that represented approximately 90 percent of the population. The load tests demonstrated double tees with similar conditions were capable of resisting code-prescribed loads, limiting repairs to only those locations, where existing conditions were not comparable to those present in the load-tested members. Guidelines based on crack width and location were developed for assessing the need to repair individual double tees.

The United States lacks a comprehensive system for investigation of structural failures. However, there are a number of systems that may be brought into play following a collapse. Transportation facilities such as bridges are investigated by the National Transportation Safety Board (NTSB). Investigations of other structural collapses are often left to independent forensic engineers hired by the parties to actual or potential litigation following the incident. The findings of these investigators may remain confidential and may never be published. It is also possible that multiple conflicting possible causes are published, such as the L’Ambiance Plaza lift slab collapse. In some cases, construction collapses are investigated by the Occupational Safety and Health Administration (OSHA), but those investigations are often limited to whether or not any OSHA safety rules were violated. In contrast, the United Kingdom has a confidential reporting system on structural safety (CROSS). This system allows for anonymous report submission.

Forensic investigations of slip, trip, and fall incidents along the means of egress, and in particular on stairs, often prompt a review of the applicable codes and standards that were in effect at the time of construction, at the time of subsequent renovation, and/or at the time of the incident. Similarly, rehabilitation following a fire, flood, or collapse, as well as the change in building use, change in occupancy or some combination, often prompts a similar investigation of the applicable codes and standards. Often these may involve codes and standards from various editions. Navigating the various editions of the codes, construction parameters, and the changes in industry practices over time can be challenging. This paper aids designers, building officials, forensic engineers/architects, attorneys, and other professionals in that effort for construction within the City of New York. This paper surveys the Building Codes of the City of New York and its adopted reference standards. It is a guide for navigating the historical editions and for identifying the applicable provisions pertaining to construction parameters of the means of egress, and in particular stair treads and risers, handrails, and slip resistance.

Whether accidents happen on a small scale, such as a low-speed collision or on a larger scale, such as an explosion, the amount of liability can be astronomical. Following a catastrophic event, often the focus is on the origin of the cause and the determination of liability. The collateral damage associated with an explosion can far exceed the losses at the origin of the event. It often takes months or years to determine the full extent of liability. After collateral damages have been torn down, repaired or repainted, the opportunity for documenting the actual damage has long passed.

When a structure fails to perform as expected or, in extreme cases, collapses, the various affected interests tend to ask the same two questions: Why? And who is responsible? These interests, which often include insurance carriers and attorneys, turn to consultants to help answer these questions by investigating a failure’s technical and procedural causes. Investigations involving multiple consultants working on behalf of multiple parties require the development of investigation protocols to coordinate forensic efforts and align expectations for the investigation. Investigations can include protocols for safety, security, and evidence preservation, identification, dismantlement, storage, sampling, and testing. Protocols are usually developed based on initial hypotheses that can vary among consultants. Protocols establish rules for documenting, handling, and preserving evidence that might later be important in litigation or other dispute resolution proceedings, as well as identify inspections and testing that can be performed. Investigations are often somewhat constrained by time and/or funds. Consequently, developing a timely and cost-effective investigation protocol involves the experience and judgment of multiple engineers who discuss and agree upon a protocol intended to provide the best likelihood for success considering the limitations. The process of developing appropriate investigation protocols for structural failures with large financial stakes and many stakeholders is often shepherded by attorneys representing the relevant parties, and can be tedious. Presented from the collaborative perspectives of a forensic investigator and a construction attorney, this paper discusses key features of investigation protocols and primary influences on their development in multiple investigation scenarios.

Catastrophic water intrusion events, such as storm-related flooding, require the removal of building materials (i.e., base trim, gypsum board, wood flooring) to prevent or inhibit fungal growth. One material that often prompts inquiry is relatively impervious flooring, specifically, ceramic or porcelain tile and the question, “Are conditions favorable to support fungal growth beneath the tile surface following a moisture exposure event?” A variety of tile installation substrates, such as wood subfloor, gypsum board, and concrete were examined. Our investigation also examined tiles installed in areas of food handling and frequent cleaning that increased likelihood of organic material exposure from sources other than flood conditions. This paper explores the potential for fungal growth underneath tile under a variety of conditions following a flood event. The results suggest that the presence of mold spores beneath a tiled floor may be more closely related to the previous use of the tiled area (food handling, frequent cleaning) and the underlying substrate (plywood or concrete) rather than whether it was flooded.

One of the most effective mechanisms for preventing failure is to learn from previous experiences. Based on this premise, the CROSS system has been operating in the UK for ten years to collect information on the concerns of civil and structural engineers. Reports are submitted by firms and individuals about their experiences during design, or on site, or during in-service operation, which have led to near hits, or failures including collapses. These descriptions are stripped of identifying features and reviewed by a panel of experts who give comments and advice as to how similar situations may be avoided in future. Reports and comments are published in quarterly on-line newsletters and are added to a web site data base. This free resource is used by practitioners, educators, regulators, and others. Trends have included problems with; structural fixings, tension systems, anomalous documentation and imported products, building control, equipment failure, competency, items falling from buildings, contractors changing designs on site, and others. Most of these events would not otherwise have been published and the information would not have been made available for the benefit of industry and the public. The paper will describe the processes used and give case studies together with plans for further development.

During the winter of 2011/2012, historic snowfalls occurred throughout several parts of Alaska. This paper deals with a building complex where a part of the roof structure catastrophically collapsed due to snow. The collapse caused not only considerable damage to the structure below, but created a series of questions regarding the causation of the collapse, the original design of the roof and the appropriate approach to rebuild the structure. As a result of the roof collapse, there were some significant challenges regarding the appropriate path for rebuilding. What requirements and obligations were there regarding the adjacent roof and would that roof need to be brought up to current code? What other structural requirements would be needed regarding the rest of the building complex? How would the insurance company and the building owner come to an agreement as to the proper course of action? The solution included close interaction and meetings among the structural experts and the local building official to provide direction where the local building code was vague and ambiguous.

A complex scenario of professional figures, clients, agreements, contract obligations, services, works, and execution technologies lies behind the collapse of three masonry structures during the consolidation of their foundations. The case histories involve different type of buildings (a tower, a residential building and an old factory) located in Northern Italy. Although the buildings were different, they collapsed substantially for the same causes. In front of similar structural mechanisms, from each case history completely different lawsuits were derived both in criminal prosecutions and in civil litigation. This is because the liability identification of each figure, not only technical, is difficult, in current legislation, where the responsibility ambits are not always clear and are often subjected to different interpretations. The reason of this uncertainty in legislation is due to the rapid evolution of standards/legislations/regulations in order to transpose the rapid evolution of technology, economy, and safety characterizing the last two decades. The legislation has also created several new technical figures, whose liability ambits are not always clear as far as their contract obligations. There is obviously a need for a better legislation system, both in Italy and in Europe, in order to guarantee a more clear definition of the activities and of the obligations of each figures involved in construction works.

The analysis of construction claims is rarely a singular issue between two parties. Construction claims inherently possess multiple issues of fact involving multiple parties. The initial claim analysis will review the engineering/construction components to identify potential deficiencies. However, in order to determine the responsibility of the parties, the analysis must include the application of engineering principles to assess the standard of care responsibilities of the parties. The standard of care responsibilities will differ with each deficiency and it is chronology within the project schedule. This article reviews the engineering methodologies used to assess standard of care responsibilities in a construction claim and demonstrate these methodologies with an actual case study.

The “standard of care” of an engineer is the metric against which the practitioner’s performance is measured by a trier of fact (a judge or jury). The fact-finder’s determination of the practitioner’s conformance with the standard of care is accomplished with the aid of forensic engineering expert witnesses testifying regarding that practitioner’s acts or omissions, and concerning the comparison of those acts or omissions against those of others. This paper examines the ethics of forensic engineering expert witnesses providing such testimony, including an examination of the concepts of advocacy, bias, and objectivity in the adversarial setting of professional negligence litigation. The intended audience of this paper includes engineering expert witnesses performing investigations and providing opinion testimony concerning the standard of care, and practitioners who themselves may be the subject of such investigations and testimony.

In addition to traditional engineering and construction technical work products, forensic engineering projects involve issues of confidentiality, expertise, and possible testimony. At the commencement of a project, a signed retention agreement should be executed. This agreement typically covers scope of work, copyright, intellectual property, professional liability, client and consultant responsibilities, insurance, termination of agreement, and other provisions, and is standard for all projects. However, unlike such documents in non-forensic engineering projects, the agreement—and hence, the work product—is generally linked to a single, named individual who has overall responsibility for the investigation, reports, and ultimately, testimony.

Forensic engineering projects, as for many engineering projects, typically result in a written or verbal report of the findings of the investigation, study, analysis, or other effort. Forensic engineering reports are prepared to assist the client to accurately assess assignment of liability and, where testimony in arbitration or court may occur, per Rule 702 of the Federal Rules of Evidence, to assist “the trier of fact to accurately understand the evidence or to determine a fact in issue.” Specifically, per the Federal Rules of Evidence, such a report or testimony should be based on “sufficient facts or data in the case that the expert has been made aware of or personally observed” and be the “product of reliable principles and methods” which have been “reliably applied to the facts of the case.” The opinions expressed by the expert in a report may be based “on facts or data in the case that the expert has been made aware of or personally observed.” During the preparation of a report, it is normal that a draft first be prepared for review. The reviewer may include the client, others within the authors’ firm, or selected independent individuals. During the review process, the report content may be altered to reflect basic corrections to grammar, spelling, and formatting; receipt of new information; need for clarification of statements; or to correct errors in judgment. As a result, it is possible that several drafts may be prepared. Although the peer review process is an established part of engineering and forensic engineering practice, there are generally few guidelines addressing the process itself. This paper briefly discusses the peer review process—specifically, what the peer review is, the roles and responsibilities of the reviewer and reviewee, and limitations on peer reviews.

Too frequently, forensic engineers are tasked with developing investigation and testing protocols for projects that exhibit damage and restraints that are onerous at best, and almost impossible to conduct at worst. Therefore, it is critical to keep the client’s expectations in mind, especially when they may be in conflict with the techniques required. As professionals, how do we find a balance between the two, without sacrificing quality? This case involved the forensic investigation of a steel framed commercial building, which had long-term exposure to water penetration from the roof and facades, and also vapors from within the facility. The building was occupied by an active commercial gym, presenting significant logistical challenges in our evaluation. Closing the active during our investigation was not feasible, so we had to coordinate our investigation around the tenant’s needs. This required solutions that managed manpower efficiently, minimized costs, and kept the investigation on schedule. Additionally, limited access and obstructions required practical methodologies that wouldn’t sacrifice accuracy. The project required us to develop inspection methods that incorporated ultrasound instruments and other devices in order to obtain the most accurate data of steel section losses and determine structural adequacies of the damaged steel members.

The use of metal corrosion as a determining factor in forensic analysis has been an ongoing practice for many years. A more focused interpretation of subsequent damaged from water intrusion can be an indispensable factor in a water loss investigation. Although the use of corroded materials in a building can be used for structural interpretation, corrosion as a “duration of loss” tool can add a new perspective previously overlooked. This paper offers qualitative insight into the duration of exposure associated with different types of materials such as copper pipe and galvanized metals. It also includes the materials and methods, litigation support for the Daubert standard, photographs for visual representation, inherent error, and similar research.

Historic steel buildings comprise a significant percentage of the existing building stock in the United States, especially in the northeast. As the uses for these buildings continue to change, structural engineers are more frequently tasked with designing additions and alterations. Often, adaptive reuse requires strengthening of the existing structure or reframing for new features within the building. In many cases, engineers must design new connections to the existing framing. To determine the capacity of the existing structure and the design constraints, conservative assumptions can be made, or steel coupons can be tested. Typically, this includes tensile testing to determine the yield strength of the steel and metallurgical-chemistry testing to determine the feasibility of welding. When testing shows that the existing steel has higher-than-expected strength or when chemical testing confirms that the steel is readily weldable, the extents of strengthening and the effort required to modify the framing can be minimized. Therefore, coupon testing is essential in the design of renovations to historic steel buildings, as it can result in significant savings to the project.

This paper presents a risk-based seismic restoration cost curve generation framework for curved steel bridges. The framework uses response surface metamodels (RSMs) in conjunction with Monte Carlo Simulation (MCS) for the generation of seismic restoration cost curves on such bridges. The framework is applied to a sample of curved steel bridges located in low seismic areas of the United States. The combined RSM-MCS models are employed to create seismic fragility curves for the selected bridges and calculate their damage ratios. Risked-based damage factor models coupled with secondary MCS enabling the treatment of variability in damage ratios and bridge features are simulated through the RSM-based fragility curves. Resulting restoration cost curves are generated using average restoration cost data in the United States. The proposed framework is capable of efficiently estimating restoration cost for such bridges under seismic hazards and to potentially aiding in making rational decisions concerning their appropriate retrofit and rehabilitation.

Single column pier bridge is designed with one column to support entire superstructure of the bridge. Because of aesthetics and increased clearance height, this type of structure may create, it has been widely employed in urban overpasses and viaducts in China and many countries. Apparently, the single column pier bridges have weak capability to resist overturning moment especially when heavy trucks run along the edge lane. Several collapses of single column pier bridges were reported by public media in China from January 2007 to September 2012. This paper investigates one of the bridge failures – collapse of Yangmingtan ramp structure in the City of Harbin, China. Provisions of bridge design loads specified in JTG D60-2004, general code for design of highway bridges and culverts in China, and AASHTO LRFD bridge design specifications, are briefly compared in the paper. The safety factor of the bridge against overturning moment is evaluated using the bridge design codes in China and U.S. The design loads specified in the JTG D60-2004 are conservative, and should not be blamed for the failure of the structure.

The failure of one structural element may lead to the failure of the other structural components where ultimately result in the collapse of the large sections or the entire structure. The progressive collapse of the structures have been mainly investigated for buildings. However, cable failure in cable-stayed bridges may cause catastrophic consequences due to the progressive collapse. This is also crucial in part given the importance of bridge infrastructure in transporting people and the goods across the country and the key role that they play in contributing towards the nation’s economy. In design process of the cable-stayed bridges, the possibility that the loss of one cable might be leading to the collapse of the entire structure is often overlooked. This is particularly due to the structural redundancy considerations and the high safety factors in design of the structural components for these bridges. In this paper, the effects of a hypothetical fire and the thermal gradient propagation along a pre-stressed cable is studied using non-linear finite element modeling and analyses. For this purpose, the possible fire intensities and durations are studied in order to determine their effects on the strength losses in pre-stressed cables using finite element method. Results of this research could be used as basis for investigation of structural failure of cable-stayed/suspended systems.

A strain hardening cementitous composite (SHCC) with extreme tensile ductility exceeding 2% was used to construct a link slab for a jointless bridge deck on Grove Street bridge over I-94 in Michigan, USA. The superior ductility of SHCC was expected to accommodate bridge deck deformations imposed by girder deflection, concrete shrinkage, and temperature variations, providing a cost-effective solution to a number of deterioration problems associated with bridge deck joints. Three days after placement on the bridge in fall 2005, early age cracking was found in the link slab. Although these cracks are small, about half the size allowable by ASSHTO, and they are bridged by fibers with load carrying capability, it is desirable to eliminate such early age cracking as much as possible. Systematic investigations (both numerical and experimental) have been conducted on identifying factors which cause early age cracking. It was concluded that the formation of early age cracking in Grove Street bridge SHCC link slab was a combination of several factors including low water-to-cement ratio of SHCC mix, use of gravity mixer, wind effect, high curing temperature, low curing humidity, presence of steel reinforcing bars, excessive restraint, high skew angle, and inadequate soaking water for curing.

The design and analysis of circular and rectangular grain bins are governed by several standards and recommended practices. In the United States, ANSI/ASAE EP433: Loads Exerted by Free-Flowing Grain on Bins, and ACI-313: Design and Construction of Concrete Silos and Stacking Tubes for Storing Granular Materials are predominantly referenced. In Europe, EN 1991-4 Eurocode 1: Actions on structures—Part 4: Silos and Tanks is a mandated code to be used by the European Union Nations. While it appears the general philosophy of the design of grain bins is similar, i.e., determine the resulting loads from grain storage and grain flow within a bin; the design loads calculated by the various codes can be meaningfully different. This presentation will compare and contrast the analytical procedures used to calculate the resultant hoop stress live loads upon steel storage bins; specifically, the differences in the generally recognized equations to determine the horizontal and vertical pressure profiles resulting from the storage and flow of grain, and the effects of temperature changes. The use and limitations of pressure calculations using Janssen’s and the Eurocode formulas will be discussed. Other factors in the design of storage bins are the properties of the stored products. The presentation will discuss the variability in grain properties used in design due to seasonal/weather conditions and long-term effects of genetic modifications. It should be noted that these two stress calculations are not sufficient to adequately design a steel bin. All code and standard specifications must be met.

Engineers are sometimes tasked with designs involving loading conditions atypical to those encountered in their common practice. In some cases, the materials imparting loads on the constructed facility behave incongruously with design assumptions. It is incumbent upon the designer to thoroughly evaluate the characteristics of materials imparting loads upon the designed structure so the constructed facility can adequately sustain service conditions. For example, a bulk fertilizer operation in North Carolina contracted a local engineer to design a covered containment structure to stockpile fertilizer products. A general contractor erected the 2,360 m² (25,400 ft²) structure, including concrete perimeter and partition walls, wood-framed perimeter walls, partition walls, interior columns, and roof structure; and steel tie rods, with intermediate wood and LVL support beams. Days after first loading bulk material by overhead conveyor into the largest of the six interior bins, the owner observed numerous broken tie rods and, upon emptying the bin, found many wood and LVL tie rod supports fractured and unseated. This paper presents the findings of a limited engineering investigation into the cause of the observed failures, including various analysis methods and evaluation of failure modes posed by the owner’s representative. Despite construction defects identified during the investigation, analyses revealed errant framing design and/or loading assumptions as the proximate cause(s) of failure.

On the evening of May 6, 2014, a 150-ton capacity magnetite storage bin fell from the third floor and landed on the first floor of a coal processing plant located near Waverly, Kentucky. The collapse caused extensive damage to the first three floors of the building and idled the nearby Highland No. 9 underground coal mine. Six employees were in the building at the time and fortunately nobody was injured. The Mine Safety and Health Administration (MSHA), an agency within the United States Department of Labor, investigated the failure. The steel bin’s eight columns were supported by a horizontally-oriented, octagon-shaped steel frame. The shear plates used to connect the beams in the octagon frame were corroded thin and failed just hours after the bin had been filled to the top with magnetite. The plant was 36 years old at the time and the condition of the structure was being routinely monitored by an engineering firm. This paper will discuss: the background on the collapse; a description of the bin and its supports; the loading; a summary of pertinent plant inspection and monitoring findings; a design drawing discrepancy found and construction changes; post collapse observations; structural analyses; and the failure sequence based on computation and visual deformation.

A fire marshal’s discovery of a cracked corbel in a newly built concrete parking structure led to closure of the garage, an extensive structural assessment, a large scale load test following the provisions of ACI 318-02, Chapter 20, and structural strengthening and retrofit. Over the course of several months, the garage was subject to an extensive engineering assessment, including nondestructive evaluation, laboratory testing, and targeted repairs. This paper focuses primarily on the design, execution, and findings of the load test. Load testing included simultaneous, progressive application of approximately one million pounds of load using a network of calibrated water bladders. The structure was monitored using a network of more than 100 instruments and a central data acquisition system. The investigation provided a sound engineering basis for evaluation of safety, serviceability, and code compliance of those aspects of the structure that could not be readily evaluated by testing and analysis.

Large-span space structural systems have huge space volume and cover large open areas, thus in the event of unexpected loading, the spatial structures may develop catastrophic progressive collapse, causing a large number of casualties and substantial losses. However up until now, most of the published papers concerned about progressive collapse were focused on frame structures. This paper presents an experimental and numerical analysis on the progressive collapse of single layer dome roof structures. Two well-designed K6-4 Kiewitt domes with 4.2 m diameter were tested, with the help of the member-breaking trigger device, dynamic strain collecting network and non-contact dynamic displacement acquisition network. Numerical simulations were then carried out. Effects of various factors such as instantaneous stress release and internal force redistribution were analyzed, the progressive damage and collapse mechanism of space single-layer dome structures due to sudden structural member loss is uncovered. Both the test and numerical analysis results show that (1) most significant impact that initially broken member had on a dome structure happens due to local internal force redistribution, and point buckling of joint leads to overall instability of the whole structure; (2) the redundancy of single-layer dome and the loading level are very important for the anti-collapse of dome structure. The results will benefit the failure analysis of dome roof structures.

Scaffolds and other temporary structures are subjected to environmental forces throughout the duration of construction and demolition that must be safely transferred to or diverted away from the existing structure. Recently, New York City implemented stricter wind code provisions that have significant implications for the design of temporary structures. This paper looks at changes in the 2014 New York City Building Code as well as two projects that would have been implemented differently as a result of the new prescription. The first case is the major restoration of a cathedral in New York City that required a complex scaffold system at the interior and exterior of the cathedral. The second case is a 9-story building where the lateral force resisting system was removed prior to the full building demolition. Designs based on the 2008 New York City Building Code and the 2014 New York City Building Code are compared.

The collapse of Hartford Civic Center Coliseum in 1978 and Minneapolis Metrodome arena roof are two incidents that demonstrate the importance of stability considerations in design and construction of arched structural systems. These type of structures usually host various social events and sports games where frequently thousands of spectators attend. design flaws, construction errors, and/or overloading may bring about structural failure of these structures with catastrophic consequences. Developing a reliable structural model to capture salient characteristics of arched structures is a challenging task facing forensic engineers investigating collapse of such structures. In this paper, buckling behavior of shallow and deep arches are studied and the associated failure modes are predicted using non-linear Finite Element Analysis (FEA). FEA results are compared to those obtained from theoretical methods of analysis for shallow arches using energy methods and for high arches through solution of classical differential equations conditions. This paper indicates that the forensic engineer should be competent in understanding and assessing possible buckling behavior of arched structures. In design projects with possible catastrophic buckling collapse, professional engineers should be aware of various buckling analyses that may need to be further examined to ensure the design adequacy of new or non-traditional designs against possible buckling failure.

Concrete silos with concrete cone spreaders are unique and complex reinforced concrete shell structures with relatively limited available design and case study literature. In 2013, the authors were retained by an insurance company to investigate the failure of a concrete cone spreader inside of a 66-m tall by 24-m diameter concrete silo located in Colombia, South America. The silo, which was used for raw meal mixing in the production of cement, remained intact while the cone and supporting perimeter ring beam inside the silo collapsed during normal operation of the plant. This paper discusses the unique aspects of this type of structure and describes the sequence of failures of the cone components. A literature review in relation to silos is provided for context, and conclusions of the forensic investigation by the authors are provided. The main purpose of this paper is to disseminate the factors of the failure of this unique structure and to present the findings of the collected field evidence, as opposed to providing a complex computational analysis. The case study presented in this paper will be of benefit to both designers and forensic engineers involved with concrete cone spreaders and silos.

Structural drying is essential to water mitigation. When a water release or intrusion occurs, a prompt effort is expected to remove wet contents and unsalvageable building materials followed by an accelerated drying to reduce moisture content to an appropriate level. However, agreement between responsible parties is often lacking as to what is appropriate, and drying efforts beyond this goal are unnecessary and wasteful. Prolonged drying efforts by contractors often clash with those bearing the financial responsibility despite the implied assurance that the extended desiccation promotes a higher probability of restoration success. This paper explores a rational and justifiable basis to develop a cost effective and efficient drying protocol. The scholarly works published by the USDA Forestry Products Laboratory and other peer-reviewed publications were reviewed to develop a rationale for establishing appropriate in-place structural drying standards, applying the concepts of equilibrium moisture content (EMC) and other critical moisture thresholds in the built environment. Guidelines from industry technical standards were also presented to calculate appropriate equipment requirements and methods to maximize dry-out efficiency. Critical moisture levels and their reasoning were discussed, as were some of the consequences associated with certain drying practices. The principles and practices of moisture measurement in building materials were described, and potential for inaccuracies was presented.

Noise is commonly understood in a regulatory context to be unwanted sound and is regulated by municipalities to ensure public health and wellbeing. Likewise, unwanted vibrations can and are regulated by similar codes and standards. This study will present a review of existing codes and standards related to vibrations encountered by human occupants in buildings. Review of typical noise codes will provide a comparison to existing vibration codes and standards. The regulatory goals will be discussed including minimizing human occupant discomfort and limiting structural damage. This study will conclude with discussion and recommendations for continued code and standard development to regulate unwanted vibrations in buildings.

This paper presents a study to determine the cause of failure of a bowstring truss roof. This work is the result of a structural engineering investigation that was conducted to determine the cause of failure of a commercial building’s roof structure in Chicago, IL during an unusually snowy and wet winter season in 2011. The subject building was built in the 1930s with prefabricated long-span bowstring roof trusses. The study comprised an engineering analysis to evaluate the roof structure’s capacity to withstand gravity loads in combination with loads imposed by the weather conditions during the days leading up to the failure. Multiple load cases were considered and analyzed to determine the cause of the failure, including the effect of wet service condition. The effect of wet service condition (as defined in National Design Specification for Wood Construction, NDS) on failure of mechanically fastened components in wood bowstring trusses is discussed in detail. Engineering analysis showed that under wet service condition, tensile forces in the truss web members exceeded the ultimate withdrawal capacity of nails holding the top chord laminate assemblage together. The pattern of observed damage which indicated a distinct localized unzipping of top chord laminates at the location of failure was consistent with results of the engineering analysis. This study re-emphasizes the adverse impact of wet service condition on mechanical fasteners in wood construction and re-iterates the importance of proper connection detailing as well as maintenance of water barrier components to prevent moisture from reaching mechanical fasteners in wood structures.

Bridges play a vital link role in surface transportation network, and their failures not only cause disruption of service but also jeopardize people’s life. Seismic base isolation is an important technique that is used for mitigating seismic vulnerability by decreasing the seismic demand instead of increasing the seismic capacity. Seismic isolation is essentially based on the idea of separating the support from the super-structure for the horizontal motions of the ground by placing flexible interfaces between the structure and its support. It decreases the lateral forces that act on the superstructure by shifting the fundamental period of the structure away from the predominant period of the ground motion and providing additional damping. In the base isolation strategy, at the same time it is possible to obtain a considerable reduction of large displacements attained at the base level as a consequence of the energy dissipation due to damping and hysteretic properties of isolation device. In this paper, various types of isolation devices, such as elastomeric bearings (lead rubber bearing), sliding systems (friction pendulum system) are evaluated for their performance in a continuous concrete box girder bridge. The response of the bridge system under earthquake has been compared with the corresponding bridge without the isolation system. The period and base shear of several base isolation systems are changed, it indicates that the period of a structure increases when base isolators are utilized in the structure.

At some point during a civil/structural forensic engineer’s career, he/she is likely to receive an assignment asking to determine why a ceiling suddenly collapsed inside a building. The cause of a failed ceiling system can range from the obvious – such as water damage, overloading with stored materials within an attic, and air overpressure from an explosion or wind event; to the “not-so-obvious” – such as long-term “wear and tear” (sometimes referred to as ‘fatigue action’ and ‘embrittlement’) of drywall attachment resulting from cyclical dimensional changes within wood framing combined with aging materials, termite damage to the hidden paper facing of drywall, and delayed separation resulting from installation defects that took years to reach a point of collapse. The purpose of this paper is to discuss various types of ceiling failures, with an emphasis on drywall (gypsum board) and plaster systems commonly found in residential construction. Ceiling construction materials and installation standards will be reviewed, including a discussion on common installation defects and reparability concerns. The authors will present several case studies from their collective experience, and present recommendations for civil/structural engineers evaluating ceiling failures.

This paper reviews several case studies of spray fire-resistive materials (SFRMs) and provides lessons learned over the course of the forensic investigations. ASTM E736-00 Standard Test Method for Cohesion/Adhesion of Sprayed Fire-Resistive Materials Applied to Structural Members (ASTM 2006) is used to determine the bond strength of newly cured SFRM. The International Building Code (IBC) 2015 (ICC 2014) specifies minimum acceptable bond strengths. The validity of those bond strengths as applied to in-service SFRM is considered. Discussions and suggestions are made to improve the testing method and reduce the allowable minimum bond strengths of SFRM. Recommendations to improve testing methods included measuring the angle of the applied tension force with respect to the tested surface, and minimizing the effect of surface forces by cutting the SFRM directly around the bonded disk.

When dealing with existing structures, whether occupied buildings or buildings in construction, occasionally there are conditions that require stabilizing and jacking of existing loaded columns. For example, foundation settlement or loss of section in a column could necessitate such a fix. Various factors such as the column material and geometry, structural system, access, geometry and capacity of existing footings, or a need to recover elevation in the structure will have an effect on the selected solution regarding stabilizing or jacking the column. In this presentation, we will discuss several case studies and how the specifics of each project shaped the proposed jacking solution.

The utilization of soft marine clay deposits in the construction of earth platforms has recently come under concern because of potential for cracking in the compacted layer after construction. Because soft marine clay is weak in tension, a testing program was undertaken to determine the effects of using coir fibers and cement as reinforcements on the potential failure of the soft marine clay layer. The investigated admixture of cement and coir fiber was fixed at 10% of cement, with the amount of coir fiber contents varying at 1.0%, 1.5%, 2.0%, and 2.5%. A three-point bending test was conducted to investigate the flexural behavior of the soil treated with coir fibers and cement at 7, 14, and 28 days curing age. The results show that the addition of coir fibers and cement increase both flexural strength and Young’s modulus. The numerical analysis using ABAQUS software was also conducted to observe failure patterns of the soil beam composite.