Experimental and numerical investigations of bolted assembled joints to concrete encased CFST columns with different connection details

Abstract

Concrete encased CFST (CECFST) composite components have prominent advantages over traditional CFST components such as better durability, high stiffness and strength, etc. However, the encased concrete outside caused certain difficulty in connecting to the steel beam. In this paper, two types of bolted assembled joints between CECFST column and steel beam were proposed and tested under cyclic loads, in which the end plate and cover plate joints were included. Typical failure modes of the joints were analyzed and characterized. In comparison, the CECFST column in end plate joints exhibited more severe failure and higher strength than that in cover plate joints. Seismic performance including hysteretic curves and energy dissipation were also discussed. In addition, numerical modelling of the joint was established considering the complicated material models and interactions in the joint core, of which the accuracy was validated against the test results. Further, parametric analyses were performed on the cover plate joints with CECFST columns through the numerical approach. It demonstrated that the axial ratio, thickness and strength of cover plate, diameter of bolt, strength and thickness of steel tube significantly affected the stiffness and strength of the joint. The experimental and numerical results revealed that the proposed two types of joints with CECFST column performed relatively favorable seismic behavior and could be employed in engineering practice.