Flexural stiffness of CFST Warren trusses with consideration of joint deformation

This study presents experimental investigations on concrete-filled steel tubular (CFST) Warren trusses, focusing on the stiffness of both the overall truss and its joints. Results indicate that axial force distributions closely match those predicted by an ideal pin-jointed truss model, with joint deformation contributing up to 20 % to the total truss deflection. Analytical models for the axial stiffness of CFST K-joints were developed, explicitly accounting for the effect of infilled concrete under both tensile and compressive brace loading. Joint stiffness equations were derived through finite element analysis and nonlinear regression. These were integrated into a predictive model for the flexural stiffness of CFST Warren trusses. Validation against experimental data showed that the proposed method accurately captures joint effects, with prediction errors within 12 %. • Stiffness behaviors CFST Warren truss and its joints were investigated, experimentally. • The axial stiffness of CFST K joints were analyzed and calculating equations were derived. • A method for flexural stiffness prediction of CFST Warren trusses was proposed which can accurately capture joint effects.