Seismic performance of T-shaped CFST column to U-shaped steel-concrete composite beam joint

Both novel composite structures, special-shaped concrete-filled steel tube (CFST) column and cold-formed U-shaped steel-concrete composite beam with stiffened rebar truss (CUCB), have advantages of good mechanical behavior, appealing architecture, and convenient construction. In this study, a series of five half-scaled specimens of CUCB to T-shaped CFST column frame joints with vertical ribs were tested under cyclic loading. Different connection detail types were designed considering both mechanical and constructional aspects. The bearing capacity, stress distribution, stiffness degradation, energy dissipation capacity, ductility, and joint stiffness were evaluated to understand the seismic performance of these new joints. Experimental results show that joints with vertical ribs have favorable seismic performance and could be considered as rigid joint in a braced frame according to Eurocode 3. Based on the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method, a multi-criteria analysis model for evaluating the joint performance was performed to determine the most effective connection detail considering the mechanical behavior and construction cost. As a result, the proposed novel joints are seismically feasible.