Analysis of thin-walled steel RHS columns filled with concrete under long-term sustained loads

The present study is an attempt to predict the time-dependent behavior of concrete-filled thin walled steel RHS (rectangular hollow section) columns by means of a model that is proposed by the ACI Specifications (ACI Committee 209,1992) [1]. A theoretical model of analysis to account for shrinkage and creep effects on concrete-filled steel RHS columns under sustained loading is presented, and is a development of the analysis used for short-term loading (Han et al, 2001a) [2]. A comparison of results calculated using this model shows good agreement with test results. The main objectives of this paper were threefold: firstly, to report a series of tests on the behavior of concrete-filled steel RHS columns under long-term sustained loading, in addition to providing further tests on the static ultimate strength of the composite columns. Secondly, to analyze influence of several parameters, such as changing steel ratio, long-term sustained load level, slenderness ratio, strength of the materials and depth-to-width ratio on the capacities of the concrete-filled steel RHS columns. And finally, to develop formulas for the calculations of the ultimate strength of the concrete-filled steel RHS columns with long-term sustained loading effects are considered, such formulas should be suitable for incorporation into building codes. (C) 2003 Elsevier Science Ltd. All rights reserved.