Journal of Performance of Constructed Facilities

The Technical Council on Forensic Engineering created a Research Committee to identify research needs for constructed facilities that do not perform in accordance with established standards, to define research problems and assign priorities to them, and to develop effective means for implementing the results of research. In 1991, the Research Committee completed a national survey. The intent of the questionnaire used in this survey was to identify the research needs related to forensic engineering. This paper summarizes the results of that poll. It is evident that civil engineers vary considerably in their opinions about research needs within their respective fields. However, significant needs were identified for information related to historical data, corrosion, new materials, leakage, in situ monitoring, and construction flaws.

The air infiltration rate for 154 windows installed in 25 buildings was obtained by a field test. Visual inspection identified the causes and sources of air leakage and operation difficulty in the sample. The frequency and impact of visible defects that cause air infiltration in the windows were determined. Windows with no visible defects produced air leakage 46% lower than the mean value. Double‐sliding windows leaked mostly from corners and gaps above the sash, whereas vertical‐hinge windows leaked from the joint between the sash and the frame. Operation difficulty seemed to increase air infiltration rates for double‐sliding and vertical‐hinge windows. The visual assessment of weather strips was useful for predicting window performance. Although sliding windows in Kuwait suffer from design defects, fabrication defects were the principal contributors to performance degradation. In vertical‐hinge windows, design and fabrication defects were the most common, with the former being more detrimental. In general, installation and maintenance defects in windows were less influential than fabrication defects, with design defects being the least detrimental. To assess the impact of minor repairs on windows performance, the air infiltration test was repeated on 11 windows after installing missing weather strips and hardware. The air infiltration rate was improved by 10‐30%.

The levels of vibration induced by pedestrian traffic on a pedestrian overpass with a 43.3‐m (142‐ft) main span are found to be perceptible to its users. The maximum root‐mean‐square (RMS) acceleration measured in the field exceeds the acceptable level of vibration recommended by the American National Standards Institute (ANSI). Three structural modification schemes, proposed to alleviate the vibration serviceability problem, are analyzed and compared. The comparison is based on the acceleration response to pedestrian loading represented by a pulsating load traveling across the bridge span. It is found that adding viscoelastic structural dampers is the more efficient and preferable scheme of modification for reducing the pedestrian‐induced vibrations.

Moisture migration through concrete floor slabs can cause damage to floor coverings such as carpet, vinyl, and hardwood. In most cases, the moisture traveling through the concrete floor slab contains dissolved salts. As the water evaporates at the slab surface the salts form a crystalline deposit, which can also attack the floor covering. One common form of moisture migration through floor slabs is by capillary action. The results of this study show that the type and gradation of the material placed below the concrete floor slab is much more important than the thickness of the layer in preventing capillary rise through concrete. Although sand is sometimes used as a capillary break, the results indicate superior performance for open‐graded 3/4 in. (1.9 cm) gravel. Slab cracks in concrete floors can act as major pathways for rising dampness. Tests on the cracked concrete core had higher vapor flow rates than tests on an intact concrete core.

Expansive soils are characterized by their moisture sensitiveness. They will expand when given access to water and shrink when they dry out. This can cause cycles of movement, causing flatwork to separate away from the structure. This progressive movement of flatwork away from the structure is known as “walking.” In many cases, there will be appurtenant structures (such as a patio shade cover) that are attached to the house and also derive support from the flatwork. As the flatwork walks away from the house, these appurtenant structures are pulled laterally and frequently damaged. The results of a field experiment indicated that most lateral movement of flatwork on expansive soils occurs during the wet periods. With each additional wet period, the flatwork continues to experience vertical and horizontal movement, but the magnitude of movement decreases. One important factor in the amount of lateral movement of flatwork on expansive soils is the moisture condition of the clay prior to construction of the flatwork. If the clay is dry, then more lateral movement can be expected than if the clay is initally wet and soaked.

Collapse of a balcony deck precipitated a full‐scale investigation and review of a condominium project near Charleston, South Carolina. Major defects in architectural and structural design as well as in the constructed product were identified. The most significant structural defect was vertical web buckling of premanufactured I‐shaped wood joists with solid plywood webs. These I‐shaped sections were used throughout the second phase of the project as a cost‐saving measure. Defects in the support of double‐I‐shaped sections utilized as girders were also identified. These defects lead to serious distortions of the main building elements, causing a decrease in utility value and giving rise to potential future collapse. Unusual contractural arrangements allowed the project to be built without a structural engineer of record. No structural engineer ever inspected the framing systems during construction. The owners retained legal counsel and litigation ensued. Recommendations for procedures preventing this type of failure are given.