Practice Periodical on Structural Design and Construction

Composite floor systems, constructed with cold-rolled corrugated steel decking covered with concrete, are a common design scenario in current construction practice. The limit state that most frequently controls the design strength of such composite floor systems in the finished structure centers on a breakdown in the interfacial bond strength between steel and concrete due to horizontal shear stresses developed during flexure. It is assumed in current practice that this same interfacial bond strength limit state governs during construction of the floor system as well. Existing design guides base recommendations regarding the timing of shoring removal, during the construction phase, on concrete compression strength alone. Such an approach is philosophically consistent with development length equations from reinforced concrete design, wherein it is assumed that the interfacial bond strength between rebar and the surrounding concrete is related to $f_c^{\prime }$ of the concrete. A series of experimental tests are carried out to study the influence that curing time and concrete strength, $f_c^{\prime }\text{,}$ have on the interfacial bond strength of composite floors. Results from full-scale flexural tests of floor slabs under uniformly distributed loading, as well as from deck pullout testing, are reported herein.

The accurate prediction of the future condition of bridge components is an important part of any bridge management system. Past bridge inspection data along with information on any repair and/or retrofit can provide a baseline for predicting future conditions of bridge components. As expected, such data are subject to a rather large uncertainty, primarily due to the variation in the inspection process. This uncertainty is also caused sometimes by unrecorded repairs and/or replacements conducted on various parts of the bridge. If not properly considered in the bridge data analysis, the uncertainty may result in an erroneous prediction for future bridge conditions. To develop a reasonable estimate for future bridge conditions, this paper discusses two possible methods. In these methods, discrepancies inherent in bridge condition ratings, that may have been due to unrecorded improvement works, are removed to arrive at more consistent estimates for future bridge conditions. In one method, the adjustment in condition ratings is done based on the notion that unless there is evidence of improvement work, the condition rating cannot be larger than previous ratings. In the other method, the duration between consecutive inspections is used as a means to construct deterioration curves. These methods are applied to rating data collected from 2,601 Illinois bridges in the period of 1976–1998. The results obtained by applying the two methods are presented in the form of bridge deterioration models, compared with one another and discussed in the paper.

The bridges built in Oporto (Porto) during the 19th century were presented in a companion paper. The individuality and elegance of these works, together with the expressiveness of the materials used in their construction (iron and steel), contributed to a large extent to the unique identity and physical appearance of the city. The tendency to erect audacious and elegant bridges was maintained in the 20th century with the construction of new reinforced and prestressed concrete bridges, two of them holding world records. In contrast with the 19th century bridges, where both designers and constructors were foreign, all these bridges were designed and constructed by Portuguese engineers.

A summary of wood shear wall testing, wood shear wall modeling, and wood shear wall reliability analysis studies over the last two decades is presented in chronological order. However, since the objective was to present the evolution of shear wall testing and modeling, and not to identify every study that has ever taken place, this paper is limited to manuscripts widely available, such as journal and conference papers. It is divided into three sections—shear wall testing, shear wall modeling, and shear wall reliability analysis studies. The review of each study appears in the section of this paper that the present writer felt the majority of the effort and contributions of the researchers was made, although many of the studies may belong in two or even three of the aforementioned categories. These important and closely related topics are presented in an effort to provide practicing structural engineers with a chronological diary of how engineers’ understanding of wood shear wall behavior has evolved.

This study analyzed an actual metal-plate-connected wood truss assembly using a system design procedure (SDP) to investigate some of the behavioral issues that may be present in an actual, complex roof-truss assembly. The assembly is in use in the United States, and the designs of all of its trusses were obtained from a truss-plate manufacturer (TPM). The TPM had designed the assembly by designing individual trusses using a conventional design procedure (CDP). The combined stress indices (CSI) of individual trusses from the CDP were compared with the CSI obtained from the SDP. Using SDP, the CSI for one member of a truss increased over 1.0 (indicating failure) in the assembly, demonstrating that redesigning the member by using SDP may increase safety. The CSI values for most other trusses decreased (by as much as 43%), indicating potential truss fabrication cost reductions using SDP. The predictions of maximum CSI and its location using SDP differed from those based on CDP. The study has demonstrated that various “system” related issues (e.g., interaction of subassemblies, boundary conditions, etc.) strongly influence the behavior of an assembly, which may not be considered in CDP.