Abstract: Heavy snowfall in the winters of 1993–94 and 1995–96 triggered numerous collapses in the northeastern part of the United States. This paper presents three case studies that were investigated by the writer's firm. Topics covered for each case study include specific climatological. circumstances, comparison to code provisions, results of structural analyses, and lessons learned. In each case, it appears that the snow load on the roof exceeded the design value given in the governing building code, by a greater margin than might be expected from the amount of precipitation alone. Issues needing additional research are also identified, such as accumulation on cold roofs, effects of freezing and thawing cycles, snow drifting on large roofs, and the effectiveness of bracing provided by standing seam roofs.

Abstract: Temporary bracing is often viewed as an unnecessary step in the process of constructing a structural facility. Unfortunately, many times this often-neglected step becomes the subject of avoidable litigation and lawsuits. This paper presents two case studies that were investigated by the authors of this paper. Included are failures due to wind and gravity resulting from inadequate temporary bracing. Topics covered in each case study include: investigative approach, analysis results, probable failure cause, and associated meteorological conditions.

Abstract: On July 21, 1998, an exterior scaffold/personnel hoist system being used to construct a 49 story building in the Times Square area of New York City partially collapsed. This paper summarizes the investigation procedures used to determine the cause of the partial collapse and the findings of the investigation.

Abstract: In this paper the acceptability criteria, in terms of human comfort, for vertical flexibility of residential building floor systems are reviewed. Examples of post-earthquake forensic investigations of home-owners' claims relating to earthquake damage resulting in excessive flexibility are described and conclusions are drawn with respect to the probable validity of the allegations.

Abstract: In June 1993, a massive sinkhole developed in a surface parking lot of a hotel facility located in the Piedmont Geologic Province of Georgia. The hole was the result of the soil erosion associated with a failed, 4-meter diameter combined sewer tunnel. Two fatalities occurred with the collapse. The subsequent forensic study uncovered a series of contributing factors, including a disregard for site history during the planning stage of the development, mis-application of the use of geogrids in the design of a safety net, mis-interpretation of the signs of impending failure in both the preventative maintenance inspections conducted by the city and forensic studies conducted by consultants immediately prior to the collapse. The paper discusses the planning and design process, the technical inadequacies of the design, and the involvement of consultants and engineers leading up to the time of the collapse.

Abstract: This paper discusses the problem of rotted wood piles and the forensic study undertaken to determine their cause. The piles had been supporting the rowhouses for more than 100 years, so why did their tops suddenly rot away? The investigation at first led to the obvious, but the development of the convincing evidence for legal actions was an arduous task that delved into construction records for a new dam and historical information on the drainage conduits prior to dam construction. The conclusion is that the impacts of remote construction may not be readily apparent and can be far-reaching.

Abstract: Metal-plate-connected wood-roof-trusses (trusses) are used extensively, both within the housing industry and in commercial buildings. With engineering that is fine-tuned and precise, trusses are part of most contemporary wood-frame buildings, and often support the roof over masonry buildings as well. With truss use so widespread, a practice in forensic engineering that includes wood structures wilt inevitably lead to calls about buildings with wood-roof-trusses. In reviewing the nature of building problems where trusses are present, and in working on the design of new buildings that incorporate trusses, I have begun to consider what it is about the trusses themselves; in their specification, design and engineering, and in their deployment that makes them different, possibly more prone to problems, but in any case special. This paper identifies some of the consequential changes that result from the use of manufactured trusses. In addition to the obvious structural substitutions, there are systemic changes that may go unnoticed. Further, the paper explores the nature of some of the most prevalent problems that its author has encountered in working with trusses and studying the buildings that employ them. Considering their widespread use overall, trusses and the buildings that exploit them seem to find their way into trouble only rarely, but when they do, the reasons may reflect shortcomings in their design and fabrication, in the flow of communication between and collaboration among participants in the design and construction industry, or misunderstanding about their use. This paper explores some of the reasons why and how using trusses differs from other practices, it reviews the truss design process, and identifies conflicts inherent in the current design-fabrication-erection process, and it proposes some steps to reduce the risks associated with using trusses. Throughout, the paper notes that there are ongoing efforts within the truss industry trade organizations that address many of these problems.

Abstract: Recent applications of nondestructive evaluation (NDE) techniques developed for timber have made possible condition assessment of structures that have previously been difficult to evaluate. Condition assessment using stress wave velocity and resistance drilling has been subjected to limited field trials. Stress wave velocity is used as a means of rapidly screening the timber to identify areas which require more detailed inspection. Resistance drilling is then used to quantify the extent of degradation. The combined use of these techniques allows for efficient condition assessment of critical timbers. This paper presents a case study of how these techniques were integrated to assess the condition of foundation piles.

Abstract: A mid-size building is defined as single or multi-family residential, commercial, office, or industrial space not over 3 stories in height and of any lateral extent. This paper will address a definition of foundation failure in terms of the effect on the supported structure based on deformation criteria as opposed to physical damage to the foundation. A foundation is often deemed failed based on the opinion of the occupants, experts or laymen on a jury, often with statements such as The slab has cracked, therefore the foundation must have failed. This paper attempts to answer the question, When has a foundation failed and when is it still performing its function? A concise review of published deformation criteria for different types of structures, ways of measuring and calculating the deformation ratios, and theoretical analysis of material tensile cracking will be presented. New methods are proposed for analysis of curvature of foundation surfaces and for quantifying distress levels to the super-structure. This information will be useful for forensic engineering studies to establish in a practical and in a legal sense when a foundation has failed, utilizing objective criteria.