Comparison of ACI, AISC, and Basic Methods for CFTs


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Title: Comparison of ACI, AISC, and Basic Methods for CFTs

Author(s): B. M. Shahrooz and W. Zhang

Publication: Special Publication

Volume: 196


Appears on pages(s): 29-50

Keywords: columns; high-strength concrete; tests

Date: 10/1/2000

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.