Congress on Technical Advancement 2017: Construction and Forensic Engineering

This paper describes how a 3D building information models (BIM) assisted in expediting the construction process for LNG storage tanks being constructed on the Gulf Coast. The American Concrete Institute has provided a road map (Information Delivery Manual, IDM) for BIM application in concrete construction, which was used as a guide for delivering this project. Four phases of project delivery employed the BIM; pre-planning, rebar fabrication and delivery, developing pre-tied rebar cages, and collection of as-built information. Pre-planning engaged the full project team, including engineering, construction, rebar fabricators, and formwork suppliers. Extensive use of 4D modeling assisted in the planning effort. Computer numerical control (CNC) information for shop equipment and automated bundling and tagging information was extracted from the BIM by the rebar fabricator. Special details to facilitate the use of pre-tied rebar cages were included in the 3D model and drawings. Laser scans of the as-built structure were compared with the BIM for quality control.

Several studies have shown the use of synthetic fibers made of polypropylene (PP) and/or polyvinyl alcohol (PVA) in concrete mixes significantly enhances the mechanical properties of concrete such as tensile strength, flexural strength, and modulus of elasticity, which reduces the need for steel reinforcement. However, there are uncertainties regarding the coefficient of thermal expansion (CTE) of synthetic fiber reinforced concrete since the CTE of PVA and PP fiber is about ten times the CTE of plain concrete. The objective of this study is to measure the CTE of concrete specimens reinforced with different dosages of PVA and PP fiber under air-dry and saturated conditions. Concrete disks reinforced with three dosages, 6, 7, and 9 kg/m³ of PVA and PP fiber were tested using the Ohio CTE device in air-dry and saturated conditions within temperature range of 10 to 60°C. The presence of synthetic fiber significantly increased the CTE of concrete by an amount proportional to the fiber dosage. Specimens reinforced with PVA fibers exhibited more increase in CTE than specimens reinforced with PP fiber under air-dry conditions. On the other hand, under saturated condition, specimens reinforced with PP fiber showed higher CTEs than specimens reinforced with PVA. Moreover, the CTE of fiber-reinforced specimens under air-dry conditions was higher than under saturated conditions. The measured CTE values could be used in the design of synthetic fiber-reinforced concrete structures.

This paper presents information about the current feasibility of utilizing construction site 3D computer models for mobile crane operators. The author is employed by a crane manufacturer and is responsible for advanced control system technologies, so this information will have an industrial viewpoint. The 3D models may or may not be considered BIM information. The 3D models might be customized or simplified to suit the small space of a crane cab. The 3D models and their presentation must also take into consideration the crane operator’s need for information without compromising his awareness of the jobsite. The author considers the real-world attributes of the computer displays available to manufacturers. Crane operations are often a critical component of the overall construction project. In some cases, particular crane operations or “lifts” are pre-planned in detail. Commercial software is available to handle this lift-planning with 3D models, and this might be another source of “non-BIM” 3D models. Another key consideration of this feasibility is how to handle spatial orientation. Lattice boom crawler cranes perform “pick-and-carry” work, so that it moves the load, and thus the jobsite awareness view of the 3D model from the perspective of the crane operator might require tracking technologies. Standardization of the coordinate system for this viewing, and how to provide the appropriate data is considered vital for future commercial developments.

Precast pre-stressed adjacent box girders have become a preferred choice for constructing bridges of short to intermediate spans in several states. However, their shear keys often experience longitudinal cracks under a large number of load and thermal cycles. Ultra-high performance concrete (UHPC) has been recently proposed as an alternate grout material to fabricate shear keys that will not develop longitudinal cracks and enhance transverse load transfer between high strength concrete (HSC) girders. Due to the difference in the thermal expansion coefficients of HSC and UHPC, thermal cycles may induce longitudinal shear stresses at the interface between HSC and UHPC materials. The objective of the present research was to evaluate the performance of UHPC in shear keys using a longitudinal shear test to determine the cracking threshold and ultimate shear strength in the longitudinal direction. The test results showed that the average maximum shear capacity for the UHPC shear key exceeds that determined from past research for any other grout material and any shear key configuration. The enhanced shear strength of the UHPC shear key may have an impact on the analysis and design of UHPC connections in bridges to better withstand the thermal stresses between UHPC and HSC composite structures.

This experimental study is based on self-dynamic concrete (SDC) with low fines that has greater flowability, passing ability and segregation resistance compared to self compacting concrete (SCC). Cement was replaced with Class F fly ash with 20, 40, and 60% by weight with fixed water binder ratio. Fresh properties such as slump flow, V-funnel, and J-ring test were performed. The hardened properties such as compressive strength, splitting tensile strength and flexural strength were also tested. In addition to fresh and hardened properties, cost analysis was also performed to check the cost effectiveness of SDC with control mix. The results of fresh properties showed that incorporation of fly ash exhibited excellent workability and flowability in fresh state. The mechanical properties such as compressive strength, flexural strength and splitting tensile strength were lesser at 28 days but attained comparable strengths as the curing age increased to 90 days for the mixture containing 20% fly ash. The cost analysis of SDC shows that it can reduce 14 to 33% of the total cost compared control concrete for the compressive strength of 25 to 30 MPa.

When designing and constructing highways or more generally any super structures on dune sands subgrade, it is essential to make sure that the subgrade layer is stable and provides good support to the applied loads. Sand dunes are spread in huge areas throughout of Iraq replacing such kind of weak soil to construction roads are not an economically feasible alternative since it is very costly; besides, the replacement soil is not always available in nearby sites. So became necessary to study the possibility of making sand dunes suitable to use as a subgrade layer for roads. This study investigate the behavior of sand dunes when using it as a subgrade layer in paved roads and investigate the effect of change relative density, modulus of elasticity of sand dunes under moving load, in permanent deformation (rutting) of flexible pavement structure, through using steel model with dimensions 600 mm length, 500 mm width, 400 mm depth, Through using three layers to represent paved roads; sand dunes as a subgrade layer, subbase and flexible pavement also FE approach applied by use ABAQUS program to Find out displacement distribution in pavement structure through build pavement structure model in ABAQUS. The results indicate an increase of relative density of sand dunes by about 15.3% and 41.3, leads to increases the number of passes by 18.75 and 28.125% respectively.

Judicious utilization of industrial waste is an essential ingredient of today’s definition of sustainable and inclusive development. Cement manufacturing is a major contributor of carbon emissions worldwide and impacts the ecological vibrancy of nature. Partial replacement of cement with industrial wastes like slag, silica, fly ash etc. has provided researchers with an important area to work and produce efficiencies in industrial waste management. Marble slurry produced from marble processing units’ accounts for major geological degradation impacting nearby areas. Its utility as a partial replacement material for cement and the long-term sustainability implication remains a matter of holistic research investigation. The present work is based on a study aiming at analyzing the long term impact of partial replacement of cement with waste marble slurry. The concrete mixes were evaluated in terms of compressive strength, tensile strength, flexural strength, permeability, abrasion resistance and water sorptivity.

Adjacent box beams are widely used in bridge construction because they offer advantages of economy, ease of construction, durability, and appearance. Recently, a skewed deeper box beam section with a large number of strands has been developed. The geometry and amount of pre-stressed tension appear to lead to cracking at the end of box beam in a consistent pattern. The cracking may affect the durability of the bridge, particularly if corrosive materials can seep into the members and affect the pre-stressed strands and transverse tie rods. Some cracked beams were removed from a structure to a manufacturer’s storage yard where these cracks were examined in detail. This study investigates possible causes of these cracks, such as load effects created by pre-stressed tension. A 3-D finite element analysis was performed which incorporated nonlinear concrete material properties. The FEA modeled a box beam from Dry Creek Road Bridge with dimensions 1.22 m (48 in.) width, 0.84 m (33 in.) depth, and 28° skew angle, which had experiences cracks at the end. The tensile strains were modeled and the computed locations of the cracks matched well with those observed in the field. The results obtained from FE analysis were also compared with closed-form solutions. The analytical results showed the skewed geometry is the main cause of the cracking. The strain resulting from the transfer of pre-stressed force in concrete along the transfer length had a favorable effect on concrete crack.

The asphalt content and aggregate gradation are critical factors related to the performance of asphalt mixtures. The solvent extraction is a traditional method which use chemical solvent to extract asphalt binder from the asphalt mixtures. However, there are some concerns on solvent extraction, for examples, fine aggregates are hard to completely separate from solvent during the filtration procedure, and therefore it is very challenging to fully evaporate solvent from asphalt binder. There is no commonly accepted method to qualitatively evaluate the residue contents of solvent in recovered asphalt binders. The remaining solvent in asphalt binders have great influence on the performance of recovered asphalt binders. The objectives of this research study are to investigate the influence of solvent in asphalt binder and further propose a method to determine the presence of solvent. The FTIR test was used to analyze the functional group of both trichloroethylene (TCE) and asphalt binder with TCE to quantitatively determine the existence of solvent. DSR tests were employed to evaluate the complex shear modulus and phase angle of recovered asphalt binders and estimated the actual performance of binders without TCE. From the testing results, it is concluded functional groups of TCE can be used as indicators to check for the existence of TCE in extracted asphalt. For PG 58-28, the peak area around wavenumber of 837 cm^-1 and 928 cm^-1 have a relationship to the TCE percentage in asphalt binder. The peak area around wavenumber of 837 cm^-1 and 928 cm^-1 are the same for PG 58-34 with different TCE content. More tests with different PG grades may needed. For both PG 58-28 and PG 58-34, |G*| decreased gradually with the increase of TCE content. And the value of phase angle increased with the addition of TCE. A mathematical function could be built to establish a relationship between TCE content and |G*|. We can estimate the TCE amount by calculating the FTIR spectrum area, and back calculate the actual complex shear modulus of asphalt with TCE.

8th Avenue Viaduct is located in Denver, CO, and is 2372 feet long. It has multiple vertical and horizontal curves. Combined with the temperature effects, this has resulted in cracking both vertically and horizontally on all 18 of the concrete hammerhead piers supporting the bridge. Inspections revealed that the cracks have expanded over the years. A 3D Finite Element Model of the bridge using ANSYS Mechanical APDL was built and calibrated using strain gages and thermo sensors installed on the bridge in order to understand its behavior under dead, live and temperature loads. Using the same software, a separate model of one of the piers was also constructed, which included the pier reinforcement, as well as the non-linear properties of concrete, allowing for accurate cracking simulation. The forces obtained from the general bridge model were applied onto the pier model and the resulting cracks were compared and found to match favorably with the cracking that had physically occurred on the pier. A rehabilitation system of post-tensioned CFRP rods was proposed and tested on the model, and was found to be very effective. After analyzing several different methods of applying the CFRP rods to the piers and comparing them in terms of cost, constructability and maintenance, the best and most effective method of application was determined to be grouting the rods into the concrete surface of the piers, using epoxy to transfer the post-tension force. The author recommends this repair be used for all the piers of the Viaduct.

Air void content is a crucial parameter affecting long term pavement performance. Ground penetrating radar (GPR) offers a nondestructive method of determining relative asphalt air void content cheaply, quickly, and over an entire project. Previous implementations of GPR for the determination of air void content, including demonstrations as part of a recent SHRP2 study, were mostly positive, but suggested the need for a testing protocol. To explore various survey methodologies, a large-scale case study was conducted on U.S. HWY 52 in Minnesota using the rolling density meter (RDM), a commercially available device developed specifically for air void analysis in asphalt pavements. The lessons learned from the SHRP2 studies and initial Minnesota pilot projects were used on a full coverage trial implementation. The full coverage trial allowed for determination of the potential of the technology for improved QA/QC and resulted in development of best practice recommendations. This paper illustrates information provided by the full coverage data and outlines recommendations related to survey coverage, data file standardization and organization, verification of location and GPR measurements, and a rigid core collection procedure. The application of these recommendations allow an RDM crew to collect valuable relative compaction data for real time feedback without interfering with paving operations or traffic closures. Additionally, core calibration can be performed after surveying to convert data to air void content and project data analysis can be used to determine the construction practices most crucial to achieving sufficient compaction.

The purpose of this paper is to describe development of a design guide focusing on stabilization of locally-maintained slopes. Motivation for this project came from engineers experiencing recurring slope failures, especially following heavy rain events or spring thawing. There is currently no guide for public works engineers to stabilize slopes of the scale typically seen along locally maintained roadways in Minnesota. Therefore, slope failures can damage roads, pose safety hazards, and introduce preventable maintenance and repair costs. While there is no single stabilization method appropriate for all situations, several methods have proven effective. Local government engineers requested guidance on stabilization methods available without paying for specialty equipment or hiring a geotechnical consultant. This study addresses the need to provide a consistent, logical approach to slope stabilization founded in geotechnical research and applicable to common slope failures. First, the authors identified slopes for further analysis via a survey sent to each county engineering department in Minnesota and conducted site investigations to characterize sites experiencing recurring failures. Laboratory and in situ testing quantified slope geometry and soil strength properties for each of the slopes requiring maintenance. Additionally, limit equilibrium method models were developed for each slope to investigate different stabilization methods in a parametric study. Finally, modeling and analysis results were summarized in a design guide for distribution to local government engineers. The deliverable will assist with efficient stabilization method selection for common slope failures along roadways.

This paper is a snapshot into incident site documentation relating to forensic engineering. Aspects focus on the investigation of vehicular crashes sites and damaged vehicles, but also touch upon fire and explosion sites as well. The goal is to portray considerations that must be taken by the forensic engineer before, during and after an inspection, while keeping safety, ethical, and legal compliance in mind. For example: before attending a multi-party inspection, the engineer must have a reasonably clear idea of what the scope of work is and what open product recalls exist potentially contributive to the incident; when applicable, a protocol can serve as a useful guide; during the inspection, the engineer must exhibit utmost professionalism, ensuring to be thorough but efficient in his or her investigation; and after the inspection, the engineer should further maintain such efficiency by sifting through and making sense of the acquired data. Notably, because ideally both plaintiff and defendant should be in pursuit of discovering how the incident truly occurred, the ruling mechanism behind every inspection should be the scientific method. In addition to the investigation process itself, the role of technology like 3D scanning, Unmanned Aircraft Systems, Event Data extraction kits and audio-visual devices utilized for data collection is also discussed. Ultimately, A Synopsis of Incident Site Documentation will serve to encapsulate the “data collection” aspect of forensic engineering for civil engineers outside of the investigative realm.

On June 17, 1958, 79 workers constructing the new Second Narrows Bridge in Vancouver, BC, Canada, were plunged into Burrard Inlet when a portion of the bridge collapsed during construction, resulting in the loss of 19 lives, including 15 ironworkers, 2 engineers, a painter and a commercial diver who drowned a few days later while trying to recover a body. Twenty others were seriously injured. Following the collapse, the British Columbia Government established a Royal Commission to examine the cause(s) of the collapse and the lessons learned as a result. After an extensive investigation, it was discovered that a temporary bent, designed by an inexperienced engineer and inadequately checked by a senior engineer failed, which lead to the collapse of two spans. Unfortunately, those gentlemen were on the bridge when it failed and both were killed. There are many valuable lessons from the Commission Reports related to the roles and responsibilities of contractor’s engineers in their design of the falsework that was intended to support a portion of span number 5 until the structural steel erection had reached Pier 15 and for the responsibilities and duties of engineers in post-disaster inspections and investigations. This presentation will provide an overview of the collapse and summarize the effects of the disaster and the findings as to what caused the collapse. Some of these lessons will be highlighted in this paper. It was a combination of engineering mistakes, flawed material and procedures, and inappropriate safety standards that resulted in failure. There are numerous incidents of bridge failures after construction. This paper focuses on failure during construction. In 1994, the bridge was officially renamed the “Ironworkers Memorial Second Narrows Crossing” in honour of the workers who died on that day.

This paper presents results and findings from a forensic investigation to identify the mechanism responsible for premature failure of an unbonded concrete overlay (UBCO). Project 2005-0518 overlaid an existing 10 in (254 mm) jointed, reinforced, dowelled concrete pavement on I-90 in Lake County east of Cleveland, Ohio, with a 9.5 in (241 mm) jointed, plain, dowelled concrete on a 1 in (25 mm) asphalt bondbreaker in 2005. After 6 or 7 years of service, the overlay on I-90 had shown premature cracks and corner breaks. Two likely causes are the cold climate in northern Ohio during construction and the presence of slag aggregate in the concrete mix. Field investigation included visual assessment, distress survey, falling weight deflectometer, MIT scan of dowel bars; and collection of core specimens. Laboratory testing included core dimensions, material mechanical properties, and petrographic analysis. A HIPERPAV simulation was conducted to evaluate early behavior of the Portland cement concrete overlay using actual daily temperature data. Recommendations were made to ODOT to improve performance and prevent similar failures in the future.

In its simplest form, sampling is the study of a part in order to gain information about the whole. Many different quantitative and qualitative techniques are available for sampling, and one single method is not all-inclusive for every type of forensic investigation, given the almost infinite combinations of different design, construction, environmental, and economic factors that can influence the performance of a constructed facility. For building envelope investigations, examples of valid and useful sampling methods have not been well documented by traditional engineering literature. This paper will focus on qualitative sampling techniques and its validity for building envelope investigations, given the diagnostic and purposeful nature of the practice. Building envelopes are complex systems with many components that interact with each other. Therefore, investigations often start at the system overview level by first studying the effects, followed by increasingly detailed study of key components as data accumulates. This qualitative process is considered information-rich, and utilizes the investigator’s judgement, experience, and contextual awareness to direct meaningful data collection at increasingly detailed levels. This paper will be of benefit to practicing forensic engineers, and will provide the investigator with additional tools for the selection of a valid sampling methodology for building envelope investigations.

A large diameter reinforced concrete underground shaft suffered from significant cracking during construction. The plans called for the shaft to be partially constructed using sinking caisson technique. The sinking would occur in a uniform silty clay in the upper 45-ft, then it would sink in a “mixed face” condition of silty clay and silt/sand with 75-ft artesian head in the granular layers. Once the caisson reached the mixed face sinking rate slowed down, ground losses evolved, and structural cracks were observed. The most probable causes of failure were identified as unbalanced loads from either different k_o in the mixed face zone or due to ground losses leading to partial loss of confinement. Both probable causes were evaluated against construction chronology from field observations, and results from simplified elastic solutions. The results indicate that the lost confinement had a more adverse effect on the stability of the shaft wall.