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International Concrete Abstracts Portal

Showing 1-5 of 11 Abstracts search results

Document: 

SP196-09

Date: 

October 1, 2000

Author(s):

R. S. Aboutaha

Publication:

Symposium Papers

Volume:

196

Abstract:

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.

DOI:

10.14359/10010


Document: 

SP196-03

Date: 

October 1, 2000

Author(s):

B. M. Shahrooz and W. Zhang

Publication:

Symposium Papers

Volume:

196

Abstract:

Using experimental data from previous tests and detailed analytical studies, the applicability of ACI and AISC standard techniques for concrete-filled tubular columns (CFTs) is evaluated. The test specimens include short and slender CFTs made with normal and high strength steel tubes filled with normal and high strength concrete. The focus of this paper is on rectangular and square tubes. To gauge the success of the code-based methods, the capacities are also computed by the fiber analysis techniques, along with a member level iteration algorithm for analyzing members with significant length. The results indicate that the ACI and AISC methods can yield substantially different capacities. In general, the capacities from the ACI method are reasonably close to those obtained from detailed analytical methods so long as normal strength tubes are used. Both the ACI moment magnifier method and AISC method are appropriate for slender CFTs although the ACI method tends to match the analytically calculated capacities more closely. Neither the ACI nor AISC method is applicable for CFTs made with high strength steel tubes as both techniques substantially underestimate the capacity of such columns. For CFTs with high strength steel tubes, it is more appropriate to assume that the steel tube fully yields when the capacity is developed. A revised version of the ACI standard method was developed by incorporating this assumption. The revised ACI method provides a fairly close estimate of the experimentally obtained capacities and those from detailed analysis.

DOI:

10.14359/9997


Document: 

SP196-04

Date: 

October 1, 2000

Author(s):

A. H. Varma, J. M. Ricles, R. Sause, B. K. Hull, and L. W. Lu

Publication:

Symposium Papers

Volume:

196

Abstract:

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.

DOI:

10.14359/10005


Document: 

SP196-06

Date: 

October 1, 2000

Author(s):

H. Kuramoto and I. Nishiyama

Publication:

Symposium Papers

Volume:

196

Abstract:

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.

DOI:

10.14359/9999


Document: 

SP196-10

Date: 

October 1, 2000

Author(s):

Y. L. MO and S. F. Perng

Publication:

Symposium Papers

Volume:

196

Abstract:

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.

DOI:

10.14359/10009


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