International Concrete Abstracts Portal

This book is dedicated to Walter P. Moore, Jr., a leader in composite building design and engineering education. Topics include beam connection detail, advanced composites for waterfront infrastructure, evaluation of high-strength square CFT columns, push-out behavior of rectangular concrete-filled steel tubes, damping factors of composite RCS frames, structural safety of reinforced concrete flexural and compression members, behavior of new steel-concrete hybrid frame system, and hybrid RC frame-steel wall systems. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP196

A series of push-out tests of rectangular concrete-filled tubular columns (CFT) was recently conducted. The objective of this research program was to identify the shear transfer mechanisms between the infilled concrete and the steel tube and to determine a method for evaluating the capacity of the steel-concrete interface in a CFT column. The experimental variables investigated were the wall slenderness ratio (b/t) of the steel tube and the use of shear tab connections to apply axial load to the steel tube. The results of this study indicated that three mechanisms are responsible for shear transfer along the steel-concrete interface in a push-out specimen: adhesion of the concrete to the steel surface, friction, and wedging of the concrete core. The role of each mechanism in transferring shear between the concrete and steel in the CFT push-out specimen at various stages of load and slip is discussed. Design guidelines for shear transfer in rectangular CFT columns are presented, including a proposed bond strength equation and a recommended strength reduction factor for bond.

The building standard law of Japan was largely revised in June 1998. With the revision, the adoption of the capacity spectrum method (CSM) for the seismic design procedure is being considered toward the enforcement in June 2000. In the CSM, the estimation of the demand spectrum is one of important issues, because the damping properties of a building should be appropriately considered. The equivalent damping factor of composite RCS buildings consisting of steel beams and reinforced concrete columns is investigated in this paper. The relations between the equivalent damping factor and story drift of RCS joints and frames, which have different joint detail and failure mode, are examined using the existing test results including those obtained in the US-Japan cooperative research program on composite and hybrid structures. It is indicated that the influence of the hysteretic damping of beam-column joints can not be ignored for estimating the equivalent damping factor of composite RCS buildings particularly when the strength and stiffness of joints are relatively small.

Steel-concrete composite columns may be designed either by requirements of the American Concrete Institute Building Code AC1 3 18-99 or by the American Institute of Steel Construction Specifications for Load and Resistance Factor Design, 2d Edition (1995). Each design standard is described for application to a concrete filled steel tube and to a concrete encased structural shape as each is designed for the same dimensional and service load conditions. These standard type column sections are used for the comparison, as the LRFD specification can be used directly only for such standard sections. The design exercise demonstrates that a) the LRFD specification requires fewer computational steps and is therefore easier to apply, b) the ACI rules tend to exaggerate the influence of slenderness, and c) different but very similar results were obtained for the two methods applied to the same design problem.

This paper summarizes the assumptions and analyses used for developing the reliability-based design of reinforced concrete flexural and compression members. Based on data on the variability of concrete and reinforcing steel physical and dimensional properties, estimates were made of the variability of strength of reinforced concrete beams and columns. These data, plus statistical descriptions of loadings, were used in a first-order, second-moment probabilistic analysis to compute resistance factors. Two sets of resistance factors for reinforced concrete members subjected to flexure or combined axial load and flexure are discussed: (a) resistance factors compatible with the current American Concrete Institute (ACI) load factors specified in ACI 3 18-95 Section 9.2; and (b) resistance factors compatible with the American Society of Civil Engineers (ASCE) Standard 7-95 (ANSI A58-1) load factors included in ACI 3 18-95 Appendix C. This paper provides a direct comparison between the two sets of load and resistance factors that are now part of the ACI 3 18 safety criteria.