Behaviours of square UHPFRC-filled steel tubular stub columns under eccentric compression

Abstract

Applications of ultra-high performance fiber-reinforced concrete (UHPFRC) in composite columns for high-rise buildings or bridges keep increasing to achieve improved structural performances. A testing program with 16 specimens was carried out to study the behaviour of UHPFRC-filled square steel tubular stub columns (UFST-SCs) under eccentric compression. Besides, influences of eccentric ratio (e/r) and thickness of steel tube (ts) on the behaviours of UFST-SCs were studied. The UFST-SCs under eccentric compression exhibited three working stages categorized as linear, nonlinear, and recession. Compression-flange yielding of steel tube and crushing of UHPFRC occurred at the elastic limit and peak load point of load-displacement curves, respectively. Despite the increasing e/r ratio decreased the stiffness and ultimate resistance of the UFST-SCs, its ductility was improved. Moreover, increasing thickness of steel tube enhanced the structural resistance of UFST-SCs under eccentric compression. The validations showed that EC4, AISC and GB50936 were conservative on estimating the Nu-Mu interaction relationships of UFST-SCs under eccentric compression. Considering the accuracy and reliability, EC4 was recommended to predict the Nu-Mu interaction curves of UFST-SCs.