Numerical and theoretical studies on the tensile strength and stiffness of plate-to-CFST column connections reinforced with internal T-shaped diaphragms

Abstract

The internal T-shaped diaphragm for steel beam to square concrete-filled steel tubular (CFST) column connections is an improvement over conventional internal diaphragms in terms of construction, cost, and mechanical property. The performance of steel beam to square CFST column connections reinforced with internal T-shaped diaphragms is evaluated by conducting static tensile load in this study. Finite element models (FEM) were established and verified, including 24 plate-to-square CFST column connections with internal T-shaped diaphragms in the weak direction (PTC-WD connections), 20 plate-to-square CFST column connections with internal T-shaped diaphragms in the strong direction (PTC-SD connections), and 16 plate-to-square CFST column connections with conventional internal diaphragms (PTC-CID connections) for comparative study. The effects of tube thickness, diaphragm thickness, anchor plate size, beam flange width, concrete filling, and tube width on the tensile behavior of the connections were studied numerically. Additionally, the stress distribution of the tube, the beam flange, the divided diaphragm, the anchor plate, and the infilled concrete are analyzed. The results showed that the tensile strength and stiffness of PTC-WD connections were improved tremendously due to the anchoring effect, and its strength and stiffness were superior to those of PTC-SD connections and PTC-CID connections under the same conditions. Based on the assumed failure mechanism of each component, the theoretical models and formulas for the tensile strength and stiffness of the connections were provided. It was found that the theoretical strength and stiffness coincide well with those of FEM results and test results.