LOCAL ELASTO-PLASTIC BEHAVIOR OF STEEL BEAM TO CONCRETE-FILLED SQUARE STEEL TUBE COLUMN MOMENT CONNECTIONS : Simple model of load-deformation relations for connection details using internal diaphragms or internal diaphragms with extended flanges

Abstract

This paper proposes a new simple model for a load-displacement relation for predicting the local tensile elasto-plastic behavior of concrete filled square steel tube (CFT) column to steel beam moment connections using internal diaphragms or internal diaphragms with extended flanges. This model is developed by superposing the load-deformation relations of a tube flange web. The tube flange is modeled as a grid beam with a tetra-linear load-deformation relation, while the tube web is modeled as a tensile member with a tetra-linear load-deformation relation. The strength of the internal diaphragm is superposed to the strength of these tube load-deformation models. The analytical results agree approximately with the experimental results up to large deformations.