Abstract
Results from mechanical tests on thirteen reactive powder concrete- (RPC-) filled circular steel tube (RFCT) columns under monotonic and cyclic axial loading are presented in this paper. The test variables include monotonic and cyclic loadings, confinement coefficient, and diameter of the steel tube. The test results show that the envelope curves of specimens under cyclic loading were similar to the load-deformation curves of the specimens under monotonic loading. Confinement coefficient had a significant influence on the failure modes of RFCT columns. With an increase in confinement coefficient of 0.53 to 0.98, the failure mode transformed from shear failure to compressive failure for specimens under monotonic and cyclic loading. In the elastic stage, no confining effect was provided by the steel tube to the RPC since Poisson’s ratio of steel was larger than the transverse deformation coefficient of RPC. Beyond the elastic stage, the axial compressive strength and ultimate strain of RPC increased significantly due to the confining effect when compared to unconfined RPC. Stress of the steel tube and RPC was investigated by using an elastic-plastic analytical model. Before yielding of the steel tube, stress development in the tube was faster in the longitudinal direction than in the hoop direction. The results of the experiment indicate that the compressive strength of RPC could be predicted by Mander’s model for confined concrete. Based on Mander’s model, an equation is extended to calculate the axial compressive strength of RFCT columns, and the predicted results are in good agreement with the test results. Based on comparative analysis of 180 RFCT columns axial compressive tests, the equation given by EC4 considering the confinement effect can be applied to predict the compressive strength of RFCT columns.
Highlights
Research interests on reactive powder concrete (RPC) has been growing in civil engineering due to its ultrahigh strength, excellent durability, and high toughness [1]
To overcome the abovementioned limitations and to extend the understanding on the behavior of RPC-filled circular steel tube (RFCT) under cyclic loading, this paper experimentally investigates short RFCT columns under monotonic and cyclic axial load with a relatively lager cross section, with the diameter of specimens ranging between 219 mm and 273 mm
While this ratio is relatively small when compared to the ratio in actual structural columns, a smaller ratio was chosen to eliminate any likely effect of column buckling in the experiments [24,25,26]. e yield strength of tube steel was determined by testing standard tensile strength specimens which were cut from each tube. e RPC infill in all tubes had the same mixture proportion and was subjected to identical steam curing regime. e RFCT column specimens were stored at room temperature for 48 hours after pouring
Summary
Research interests on reactive powder concrete (RPC) has been growing in civil engineering due to its ultrahigh strength, excellent durability, and high toughness [1]. Liu et al [15] investigated the axial compressive behavior of eighteen circular tube columns filled with HSC for which the compressive strength of concrete varied from 60 to 94 MPa. e external diameter of the columns ranged from 133 mm to 140 mm. Qi et al [16] investigated the behavior of circular tube columns filled with HSC having compressive strength of 76.9 MPa when subjected to axial loading. Test results showed that HSC-filled specimens exhibited greater axial load capacity when compared to normal concrete filled tube columns having same volumetric steel ratio. A total of 56 circular and square RFCT short columns under axial load with high steel strength up to 780 MPa and RPC with compressive strength up to 190 MPa were conducted by Xiong et al [19]. A comparative analysis of 180 RFCT columns axial compressive tests is conducted to propose a calculation formula of axial compressive strength of RFCT columns
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