International Concrete Abstracts Portal

The behavior of concrete filled steel tube (CFT) columns made from high strength materials was investigated experimentally. The effects of the width-to-thickness (b/t) ratio, steel tube stress-strain characteristics, and axial load on the stiffness, strength, and ductility of CFT beam-columns and stub columns were studied. Twelve experiments, which included four stub tests (monotonic axial load) and eight beam-column tests (constant axial and monotonic flexural load) were conducted. The CFT specimens were 305 mm square tubes, made from either conventional (A500 Grade-B) or high strength (A500 Grade-80) steel with nominal b/t ratios of 32 and 48. The CFT specimens were filled with high strength ( 104 MPa) concrete. Experimental results indicate that the concrete infill delays the local buckling of the steel tube, and that for lower levels of axial load and smaller b/t ratios the steel tube confines the infill concrete, thus increasing its ductility. Comparison of the experimental results with predictions based on current code provisions indicates that the axial load capacity of the high strength CFT stub column specimens can be predicted with reasonable accuracy by superposition of the yield strength of the steel tube and 85% of the compressive strength of the concrete infill. The moment capacity of the high strength CFT beam-column specimens can be conservatively estimated using American Concrete Institute provisions for conventional strength CFT beam-columns. The initial and serviceability-level section flexural stiffness of these specimens was predicted with reasonable accuracy using the uncracked transformed and cracked transformed section properties, respectively. The experimental results indicate that the curvature ductility of a high strength CFT beam-column decreases significantly with an increase in the axial load or the b/t ratio of the steel tube.

Reinforced concrete buildings with shearwalls are very efficient to resist earthquake disturbances. In general, reinforced concrete frames are governed by flexure and shearwalIs are governed by shear. If a structure includes both frames and shearwalIs, it is generalIy governed by shearwalIs. However, the ductility of ordinary reinforced concrete framed shear walls is very limited. To improve the ductility, this paper describes experiments on framed shearwal I s made of corrugated stee I, and the experimental results are compared with ordinary reinforced concrete frames and shearwalls. It is found that the ductility of framed shearwalls can be greatly improved if the thickness of the corrugated steel wall is appropriate to the surrounding reinforced concrete frame. If the thickness of the corrugated steel wall is too large when compared to the surrounding frame, the ductility will be reduced. It is also shown in this paper that the fiber-reinforced plastic composites can be used to strength the critical sections of the reinforced concrete frames, so that the seismic behavior (including ductility and dissipated energy) is improved.

the reinforcing bars and the surrounding concrete within the beam column joint. This paper introduces a new innovative steel-concrete composite frame system with controlled plastic mechanism. This frame system consists of steel tubed reinforced concrete (STRC) columns, and ordinary reinforced concrete beams with relocated plastic hinges. Beam plastic hinges are relocated by the use of straight headed bars. The STRC column is an ordinary reinforced concrete column but, transversely reinforced with light ordinary ties and a thin steel tube. Compared to concrete filled tube column (CFT), the steel tube of STRC column transfers no axial load, provides better confinement, and consequently, increases column ductility. In this paper, experimental investigation of two full scale STRC columns and two beams with and without headed bars are presented. Test results suggest that STRC columns and beams with relocated plastic hinge regions could offer a more ductile structural frame system for medium and high rise buildings in zones of high seismicity.

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

The Through beam connection detail has been identified as an ideal rigid connection for attaching steel beams to concrete filled tube (CFT) columns. A combination of analytical and experimental studies is being conducted to comprehend the behavior of this detail. The test specimen consisted of a CFT column and a steel beam passed through the column to represent an interior joint in a building. This paper presents a summary of the finite element analysis that was conducted to comprehend the force transfer mechanism and identify locations of potential stress concentration. The analytical results were verified by comparison with the experimental results. Both the experimental and analytical results showed the capability of the connection to develop the full plastic bending strength of the connected beam. The elements that contribute to the connection strength were identified as: the beam web, the steel tube, and the concrete core.