It is important to study construction failures in order to determine their root cause or causes so that future failures can be avoided. One such study was conducted by a subcommittee of the United States House of Representatives following a number of structural failures in the 1970s and 1980s. The subcommittee findings were released in 1984 in US Congressional House Report No. 98-621, titled Report on Structural Failures in Public Facilities. One of the factors identified as critical to preventing structural failures was inspection of construction by the structural engineer of record (SER). Given that finding, structural engineers need to be actively involved throughout the construction process, using inspections as a means to promote safety, improve the quality of the work, and reduce claims due to failures. Concerns regarding liability, construction schedule, and costs are major reasons why SERs do not perform inspections. SERs can manage those concerns, however, by understanding the relevant building code requirements regarding inspections, the benefits of inspections with respect to safety and quality of construction, the roles of the parties involved in construction projects, and the legal duties of the engineer.
Engineers engaged in forensic investigations have unique roles and responsibilities that differ from those of design engineers, and must adhere to a distinct standard of care that is too seldom discussed, considered, or understood. This paper explores the forensic engineering standard of care question through the case study of a portable water storage tank failure. The incident precipitated the production of no fewer than ten engineering reports asserting various distributions of blame on the manufacturer, owner, installer, and designer, a number of which ultimately called into question the structural design of an entire line of production equipment. WJE reviewed these volumes of work, and finding them inconclusive, performed independent non-linear finite element analyses of the design, fabricated representative connection test specimens, and subjected them to high-cycle fatigue and strength testing to evaluate service life performance. Our results and the actual in-service performance demonstrated that the design met or exceeded relevant standards and performance requirements, despite voluminous, corroborating, and ostensibly sophisticated allegations to the contrary. We believe that such misrepresentations of reality are far too common to the forensic engineering field and draw a series of lessons from our experience on what the standard of care means to engineers who find themselves opining on another's work.
The harsh environment of south Florida leaves little to no margin of error in the construction practice; in fact, the quality of execution significantly affects the performance of the building envelope. Walls, windows, doors, and roofs are the first line of protection against this environment. This article offers an overview of common factors that impact the performance of the building’s envelope in south Florida. The components that are outlined in the article include stucco covering, steel post-tensioning live ends, glass and glazing, and tiled decks. Examples of defects and failures as observed during forensic investigations in both new and existing buildings are presented. Best practices for design and construction will also be discussed.
An engineer's employment, business, and professional practice can be affected by an assessment by others of that engineer's performance related to the "standard of care." The concept of the standard of care is often misunderstood and misapplied, to the detriment of the engineer whose performance is being assessed. This paper addresses the concept of the standard of care, and shows how an understanding of the standard of care can aid an engineer in avoiding and defending against claims of professional negligence.
While engineers are devastated when they first learn of a failure of a structure that they have designed, modified, or participated in its construction, this is just the beginning of an often years-long litigation journey if, eventually, there are legal claims as a consequence of that failure. Failures of silos in industrial facilities bring another level of complexity due to the number of parties involved (e.g., contractors, subcontractors, equipment suppliers, raw material suppliers, owners, plant operators, and maintenance personnel), the level of complexity in these industrial systems, and the cost of the equipment damaged as well as downtime, and potentially, serious injuries or loss of life. There are many causes of silo failures including design, construction, usage, and maintenance. During the long process of designing and constructing a silo, many omissions or oversights can occur. Many of these are due to the lack of training in this specialized field and the paucity of reliable, useful information in the literature, including relevant codes available for engineers in charge of the design of silo structures. Engineers in charge of the design and construction of silos as well as similar industrial facilities used to store and/or process bulk solids will benefit from this paper as they will be able to better understand the legal implications beyond silo failures. Engineers involved in forensic engineering and insurance claims will be able to gather information on the engineering as well as the legal side of failures in industrial storage facilities for bulk solids.
Computer vision, a field which falls under artificial intelligence, is increasingly establishing grounds in many disciplines, as the demand for automated means to solve real world problems gradually grows. Forensic engineering is a discipline that has been moving very closely towards the use of computers as investigation and problem-solving tools. This begins to kindle ideas of how forensic investigation and computer vision can work together to create new approaches and techniques within the field. This paper explores how to use computer vision as a tool to classify the building materials, evaluate the details, and potentially identify distresses of building envelopes using a collection of existing digital images and algorithms that help train the computer to produce efficient and reliable results. Discoveries about computer vision and the complexity of replicating and automating the human visual system encourage deep research on the programming of algorithms to improve and recognize the machine’s ability for the forensic investigation.
This study advances our understanding of metal corrosion rates among 21 common building, plumbing and electrical components by comparing their qualitative responses to four exposure scenarios: control conditions (24 degrees C and 50% RH), elevated humidity (> 95% RH), freshwater mist, and saltwater mist (seawater @ 35 ppt) over periods ranging from 11 to 18-months. The entire study was conducted over a nine-year period. Changes in surface appearance varied among the components due to their elemental composition. The final study documented changes to galvanized steel pieces ( i.e., garbage disposal bracket, electrical outlet cover, electrical junction box, flexible electrical conduit, and electrical conduit strap), steel pieces (i.e., sink fastener and face-mounted hinge), and one brass piece (SharkBite angle stop valve). The elemental composition revealed that the most corrosion resistance over the entire study was among nickel, stainless steel, and galvanized steel components. The least resistance was exhibited among those with a predominance of iron. The study concluded that careful examination of these components could provide insight into the duration of a water loss.
Underpinning has become a common practice in lot-line construction to support excavations deeper than historic adjacent structures without undermining them. However, if the underpinning design and construction are not performed with great care and with sufficient understanding of the existing conditions of the historic structure being underpinned, this can lead to differential settlement and potentially the subsequent partial collapse of the structure. The purpose of this paper will be to address the multitude of factors relating to underpinning design beneath historic structures, and will discuss the requirements and potential risk factors of the underpinning design of historic structures including soil investigations, dewatering, building investigation, etc. Additionally, this paper will discuss methods for building assessment and monitoring during underpinning construction to help avoid a potential catastrophic failure. Case studies demonstrating the consequences of inadequate or poorly constructed underpinning will be presented to highlight the potential risks of underpinning historic structures.
In forensic assessment, new technologies are being developed and implemented at a rate which far outpaces typical updates to design standards. The speed of this technological development and implementation may prove challenging for the field of civil engineering, which relies heavily on considerations from standard of practice, because there must be a strong technical understanding of the precision, bias, and repeatability of a new assessment tool before it may be successfully used for forensic assessment. This paper presents a discussion on unmanned aerial systems (UAS), which are the leading platform for advances in technologies, such as near-infrared thermography, image processing, and machine learning. Advances in these areas are reviewed in this report. While UASs were found to be useful for certain nondestructive forensic assessments, several shortfalls, and common misunderstandings associated with these potential forensic tools were identified and discussed in this report.
Between July 14-16th, 2021, record rainfall and subsequent flooding resulted in the deaths of over 200 people and billions of dollars-worth of damage in Germany and Belgium. An NSF sponsored Geotechnical Extreme Events Reconnaissance (GEER) Association reconnaissance mission was undertaken by the authors to investigate the effects of flooding in Germany, Belgium, and the Netherlands. The two-week-long mission provided insight to the performance of various geostructures such as building foundations, roads, and bridges. This paper provides a summary of observations made by the US-based GEER team in collaboration with many local European colleagues. Key observations presented include a bridge case study, the impact of scour and erosion on different structures, and soil-structure interactions. A review of the data used to inform the reconnaissance mission as well as the data collection technologies used, including terrestrial LiDAR, UAV-Structure from Motion (SfM), and multispectral imagery, is also presented.
Diverse issues can manifest as undesirable deflections or slopes in buildings. Determining the cause of the deflection is important to understanding if it is merely an undesirable condition or a symptom of a more concerning issue. To assist in making that determination, an overview of floor and roof deflection investigations is presented to highlight limitations of code and construction practices in avoiding deflection-related problems and identify key elements of investigative approaches to determine distinct causes originating from similar reported symptoms. Causes such as indirect load paths, decay, design and construction defects, materials differences, and incompatible deflections between floors are discussed and related conditions that deserve additional attention will be identified.
In this paper, the author presents the results of a forensic investigation at a tailings storage facility (TSF) located in San Luis Potosi, Mexico. The purpose of the study is to investigate potential seepage observed along a localized portion of the existing embankment dam. Field observations and predictive modeling of seepage and slope stability have been revisited and applied to obtain a better understanding of dam performance and to estimate the probability of failure of embankment slopes considering the existing dam configuration and a proposed dam raise. The investigation comprises visual observations, test pitting, field and laboratory tests, seepage analyses, slope stability analyses, and a review of the quality control construction data. The results suggest that the observed localized `damp' portion of the embankment is non-hydrostatic. Therefore, a raise of the existing dam above the current dam configuration would be feasible provided best dam engineering practices are followed. Design considerations should focus on the location of the tailings pond. Instrumentation plans should consider monitoring of piezometric heads within the existing and new embankments, and future placement of fill materials should be in accordance with appropriate earthwork specifications.
Evaluating whether a structural system has collapsed may not be as obvious as it sounds. Most people consider collapse to be a condition where the structure or a portion thereof has fallen down. However, in the context of insurance coverage, evaluating whether “collapse” has occurred may be far more nuanced—especially when collapse is not explicitly defined in the policy. State courts have generally adopted one or more of three interpretations for the term collapse, broadly described as: (1) actual collapse, (2) imminent collapse, or (3) substantial impairment of structural integrity (SISI). Even with these interpretations, there are widely varying opinions regarding the level of structural impairment that qualifies as collapse. This is especially true for SISI. Although some state courts have attempted to define collapse using commonly understood terms, there are no industry standards that define these conditions in customary engineering terms (demand, capacity, factor of safety, etc.). This ambiguity leaves individual engineers to form their own opinions, which predictably, vary widely between engineers. This paper draws from available literature and prior legal findings to propose a rational method for engineering professionals to evaluate collapse based on design loads, strength of materials, and system effects, with a particular focus on SISI.
Restraining rails are commonly used on track at sharp radius curves for light rail transit (LRT) in North America. Recently, an American light rail operator found that bolts fastening restraining rail to the running rail were routinely failing after relatively short service lives. This work presents the results of analyses that were performed to determine the root cause of failure. A metallurgical investigation of the bolts was undertaken that consisted of a surface chemical analysis, visual inspection, and fractographic analysis of the fracture surface. The stress demands on the bolts were examined by performing three-dimensional nonlinear finite element analyses of the restraining rail assemblies. The results suggest that the bolts become vulnerable to high cycle fatigue after loosening. Recommendations are presented for improved performance.
“All concrete cracks” is a favorite saying of engineers and contractors attempting to explain cracks in concrete work that they often cannot otherwise justify. However, it is often perceived as just an excuse for failing to provide a well-reasoned opinion regarding the likely cause(s) of the cracks and the negative ramifications, if any, associated with their presence. It is true that owners often expect unachievable results in their concrete structures when it comes to cracks. This paper will discuss the need to manage the expectations regarding concrete cracks on a project and how to properly address it when it inevitably occurs. Concrete structures almost always have cracks, and the project team needs to be made aware of this fact prior to construction. This can better help align the team’s perceptions of acceptable and unacceptable cracks with those shared by the Structural Engineer.
The case study involves an industrial building that was constructed in the early 2000s with a low-sloped, mechanically fastened, single-ply membrane roofing system, with parapet walls that transitioned to mansard roofs with standing-seam metal panels. An expansion was performed adjacent to the building in 2014 that added a pitched roof along the interface that penetrated an existing parapet wall and mansard roof assembly. Additionally, changes to the operation of the building were made that required a regulated internal humidity level of 45% (relative humidity) with a frequent air exchange rate. Within 4 years post construction, the roofing membrane was noted to be billowing and sections of the membrane had become unbonded from the parapet wall. Further investigation revealed that the mechanical roof connectors were severely corroded and failing throughout with significant moisture present indicating a large-scale issue. Analysis of the building was performed which identified significant hygrothermal issues. The findings of this investigation initiated a complex design and repair to the existing building.
This paper will focus on structural failures caused by below-design wind events. The structure is flexible and behaves in ways not common to building designers. The failure mechanism in each case is atypical and not covered within the design guides or building codes. The mechanisms covered in this paper include torsional galloping, vortex-induced vibrations, and rain-wind-induced vibrations. Case studies for these mechanisms include lighting poles, bridge cables, and single-axis solar trackers. Each case study will explore the mechanism, failure modes, investigative methodology, and preventive or repair strategies. Lessons learned from these failures will enable a relatively better design of flexible structures sensitive to wind. Understanding these mechanisms will also enable the development of appropriate theories for forensic engineers.
This presentation is about the experience of discovering procedural non-compliance as a root-cause of several critical equipment failures. These are often failures that many others had previously investigated but had not identified root-causes of the failures. By recognizing that there are 3 areas to consider when analyzing failure-physical, human, and latent-the mindset of the investigator broadens to consider more than the broken component. To illustrate the concepts, a basic summary of three major equipment failures will be used to show how the physical, human, and latent causes of failure can lead to procedural non-compliance. In basic terms, people do not always follow the outlined procedures, but they do not seem to realize it. Additionally, certain "red flags" will be presented in plain terms that can alert the investigator to the possible existence of procedural non-compliance as a root-cause. By recognizing the existence of these types of failure causes, the investigator can more easily determine root-causes of failure.
An institution of higher education recently decided to relocate and repurpose several of their existing dormitories to allow for construction of new dormitories. The three-story dormitories generally consist of unreinforced hollow masonry foundation walls, with reinforced-concrete footings. The building relocations required excavation beneath each building to provide clearance for the main jacking beams and cross beams to be inserted below the buildings. The building mover successfully transported the first two dormitories. During the third building relocation, the general contractor (GC) found the east foundation wall at one of the dormitories was reinforced concrete, rather than hollow masonry. The GC engaged a saw-cutting contractor to core access holes to insert the cross beams to lift the structure and then saw cut a horizontal separation joint through the east foundation wall of this dormitory above the line of core holes. After saw cutting the reinforced-concrete east foundation wall and excavating immediately adjacent to the east foundation wall footing below the bottom of footing, the east foundation wall at the third dormitory experienced a bearing capacity failure, which required emergency stabilization and shoring of the building. The failure caused differential settlement of the footing along the east side of the third dormitory, and large cracks developed in both the reinforced-concrete foundation wall and the hollow-masonry exterior walls above. This paper provides an overview of the project and discusses the causes of the failure and the emergency building stabilization.
While hundreds of standards exist for testing the physical properties of many materials, there is no industry standard for testing shear strength in concrete. Ascertaining the actual shear strength across a bonded concrete interface, such as at repairs or construction joints, is particularly problematic. In investigating planar strength, the shear strength between concrete surfaces is of primary importance. Studies from the late 19th century to the present day have not resulted in a universally accepted standard test to determine the bonded concrete shear strength. Although there is no ASTM standard for a direct shear test at the bonded concrete interface, several methods used in various locations throughout the United States include the Brookhaven National Laboratory Guillotine Shear Test and the Iowa Shear test. Other shear test methods available include the Asymmetric Four-Point Bending, Bond Test (also called the Tensile Bond Test or Pull-Off Test), CTL Thompson Method, Iosipescu-65 Method, Jacking Shear Test (also called Push-Off Test), Slant Shear Test, Torsional Shear Test, and US Bureau of Reclamation Shear Tests. Also, this paper summarizes historical and recent research results at the University of Colorado Denver where different devices test direct shear in bonded concrete specimens. The research objective is to determine each shear test method’s pros and cons, and recommend one method as a universal standard regardless of the bonding agent or method.
