Practice Periodical on Structural Design and Construction

If modern engineers devote careful attention to the environment of a project and study historical building techniques they can create more sustainable structures. Rammed-earth construction creates a thermal mass structure that cools the interior space during hot, dry summers and absorbs heat during cold winters. It is a historic building method dating back over 2,000 years, and the techniques of native practitioners offer suggestions as to how modern engineers can successfully apply the method.

This paper presents an overview and a recap of basic equations of structural reliability as applied to structural condition assessment. Common sources of uncertainties in structural design parameters are explained, and methods to quantify uncertainties are reviewed and presented. Through two illustrative examples, it is demonstrated that in certain cases, even though an acceptable factor of safety may be obtained, in the presence of uncertainty, there may be a rather undesirable probability of failure associated with the factor of safety. The paper is intended to offer a practical and simple, yet logical, approach in treating uncertainties in structural condition assessment.

This research investigated flexural behavior of repaired RC beams that experienced simulated lateral damage to replicate vehicle impact/collision. The experimental program included the testing of 34 RC beams, which were laterally damaged and then repaired using carbon-fiber-reinforced polymer (CFRP) fabrics. The damaged beams were repaired using various levels of strengthening (number of CFRP soffit layers) and multiple configurations of anchoring CFRP U-wrapping. Specific attention was paid to understanding the effects of intermediate U-wrapping on strains developed in the longitudinal soffit laminates and the beams’ ultimate capacity. Other details for the flexural repair system, such as end-peeling previsions, were also addressed. The test results indicated that CFRP repairs have the ability to restore and enhance the capacity of damaged RC beams by up to 353%. The results also suggest an optimum range for spacing intermediate U-wrappings to suppress strains felt by longitudinal soffit laminates, thereby mitigating premature debonding failures. Design considerations and recommendations for optimum CFRP configuration, level of strengthening, and application details for repairing laterally damaged RC beams are proposed.

Supercavitating baffle blocks, with their unique geometry, have been shown to be highly effective in reducing cavitation damage to stilling basins’ floors and to the baffle blocks themselves. However, this unique geometry, which consists of thin concrete edges and steep slopes, is very susceptible to abrasion erosion by debris impacts. This paper presents a methodology for sizing debris, calculating impact forces, and an armored plate design that can withstand high-velocity impacts while conforming to the baffle blocks challenging shape.

Because of the unpredictable nature of mechanical and environmental loads, steel bridges do not necessarily behave as anticipated in design. Moreover, such loads cause the deterioration of the bridge with respect to time. In the United States, there are many highway bridges classified as structurally deficient because of aging and/or insufficient design. Also, considering the catastrophe of the I-35W Mississippi River Bridge, it is critical to implement a system to monitor the health of bridges and report when and where maintenance operations are needed. Through successful health monitoring, the life of a deteriorating bridge can be extended, and catastrophic failure events can be prevented. Therefore, it is important to have a systematic approach to monitor the health of a bridge. Despite its promising benefits, structural health monitoring (SHM) is infrequently used in bridge applications. This paper will present the basic concepts of SHM and the conventional and new sensors applied for monitoring various structural parameters in steel bridges, which is beneficial to practitioners on bridge inspection and retrofitting.