Journal of Performance of Constructed Facilities

An investigation of concrete exposed to sulfate soils is used to illustrate a methodology for the systematic study of the condition of concrete in service. Condition surveys of the site and tests of engineering properties of the concrete were supplemented by examination of concrete cores using the stereomicroscope, the optical microscope, the electron microscope, analysis by wet chemistry, thermal analysis, and X-ray diffraction. Step-by-step progression from large scale (tens of meters) to submicroscopic scales (tens of nanometers) gave continuity to detailed test methods. It also allowed for the selection of specimens appropriately representing the concrete as a whole, and ensured reliable interpretation of the results. In many cases, more than one test method provided the same or similar information. The writers believe the methodology employed will be of value to other investigators.

The failure of several 15-m wood trusses at the lower chord splice joint is described. These trusses were built in the early 1940s with 100-mm split-ring connectors at the splice. The general failure pattern was initially horizontal splitting at the end of the chord member in two places through the depth of the member. As the split progressed, the center plug would move out from the end of the member, with lateral movement as great as 15 mm. Ultimately, a tension failure occurred across the grain. The exact origin of the truss failures is unknown. The trusses were appropriately designed and had enough reserve capacity in the original design to compensate for the decrease in allowable stresses that has occurred since construction, including the use of No. 2 lumber instead of the specified select structural lumber. The best conjecture of the cause of failure would be that it was initiated by secondary stresses. The continuity of the bottom chord over several panels induced secondary tensile stresses perpendicular to the grain at the splice. Additional tensile stresses perpendicular to the grain from drying shrinkage restrained by the split rings contributed to the initial horizontal splitting. Contributing to the development of the failure were probably the load-duration effects and perhaps higher temperatures. Despite the distress observed, there is no immediate danger of collapse. Lateral in-plane restraint at the truss ends from columns and adjacent portions of the building enable an arching mechanism to form that gives stability to the trusses even in a distressed state.

Integral abutment bridges have been gaining popularity among bridge owners as cost-effective alternatives to bridges with conventional joints. They reduce initial construction costs and long-term maintenance expenses, improve seismic resistance, and extend long-term serviceability. New York has been building them since the late 1970s, with a wide variety of details, and they have been performing well. For further improvement of New York's design practice, a comparative survey was undertaken across North America, focusing on design and construction of both substructures and superstructures. In all, 39 states and Canadian provinces responded, including 8 who said they had no experience with these bridges. Responses are analyzed and summarized in this paper. Overall, integral abutment bridges are performing as well as, if not better than, conventional bridges, but no uniform national standards exist for their design. Design practices and assumptions concerning limits of thermal movement, soil pressure, and pile design vary considerably among responding agencies. These decisions are based largely on past experience. Validity of these assumptions needs investigation by testing and analysis to ensure efficient and reliable design.

Many buildings have capabilities to admit only minimal quantities of fresh air to the air-conditioning supply ducts. There are climates that have temperature and humidity ranges for months of the year during which up to 100% fresh air could be admitted for ventilation and provide thermal comfort. This would result in a number of benefits that, when carefully considered, may lead to replacement of existing air-conditioning systems and/or the introduction of new systems or subsystems to complement existing systems. Examples illustrating the use of up to 100% fresh air for all or a portion of the year, in cold, temperate, and hot climates, are reviewed. The focus of this paper is on the development of design guidelines for potential replacement of the air-conditioning systems in buildings. The guidelines were developed with the assistance of 92 design professionals in nine countries, namely the United States, Japan, Canada, Australia, the United Kingdom, Singapore, Spain, Saudi Arabia, and Kuwait.

Automobile accident reports and full-scale crash tests of existing breakaway cable terminals (BCTs) indicated their poor performance during end-on impacts. This paper presents results of a feasibility study, which was conducted to identify problems with existing BCTs. The nonlinear, explicit, dynamic finite-element code LS-DYNA was used in the investigation of BCT design problems. Several problems were identified in the past during the full-scale crash tests. These problems became clearly visible when computational mechanics analyses were used. In addition to severe vehicle damage, vehicular impact induced dangerous, large deceleration peaks and uncontrolled vehicle trajectories. Analysis of actual crash tests and LS-DYNA data led to the conclusion that the terminal is too stiff along its longitudinal direction and fails to smoothly control dissipation of the vehicle kinetic energy. Therefore, the major objective of the research was to soften the existing system by weakening the rail in strategically located areas. The paper describes the design retrofit process, which was continuously guided by computational mechanics analyses. Specific retrofit recommendations emerged at the end of this process and they are described in the paper. Full-scale crash tests are recommended to confirm expected benefits of the proposed retrofit.

Since 1989, the American Society of Civil Engineers Technical Council on Forensic Engineering has conducted two surveys to gauge the need for teaching failure analysis topics in the civil engineering curriculum. Although the surveys addressed different topics, the limited availability of instructional materials in failure analysis was a recurring theme. The purpose of this paper is to respond to each of the questionnaires by reporting on the ongoing development of a preliminary Internet web site whereby consultants can contribute failure case studies. These case studies will then be readily available for professors and instructors to use in stand-alone failure analysis courses. The case studies can also be used as supplemental material and can be integrated into existing general civil engineering curriculum courses as well.