Design and testing of concrete encased steel composite beam-columns with C90 concrete and S690 steel section

Abstract

This paper investigated the structural performance of Concrete Encased Steel (CES) beam-columns made of C90 concrete and S690 welded steel section. Seven large-scale beam-column specimens including four steel reinforced concrete encased specimens and three fiber-reinforced concrete encased specimens were tested under axial compression and end moments. The end moment was applied by a compression load acting at an eccentricity. The test results in terms of failure mode, load-carrying capacity, deformation capability and second-order moment were presented. In addition, the effects of load eccentricity, steel fiber content, steel contribution ratio, and stirrup configuration on the column strength and ductility were analyzed. The existing design methods suggested in EN 1994-1-1 and AISC 360-16 were examined in constructing the axial force-moment interaction diagram and in predicting the effective flexural stiffness for second order analysis. A fiber element analysis method was developed and the predicted results were verified against the load displacement response and the failure loads from the tests. The analysis method was then used to generate additional data for beam-columns of various design parameters. Finally, an analytical method was proposed based on regression analysis to estimate the short-term effective flexural stiffness for the design of high strength CES beam-columns.