Abstract
It is important to formulate the stress-strain relationship of the encased concrete of concrete-filled steel members with rectangular cross section subjected to bending and torsion simultaneously by considering confined effect due to the outer steel plates in order to simulate the elasto-plastic and finite displacement behavior up to and in the vicinity of the ultimate state of these members. Then, formulated in this paper is the stress-strain relationship of the encased concrete of these members by extending the existing theory of concrete-filled steel members subjected to pure torsion. Also carried out is a loading test on the ultimate strength of concrete-filled steel box members subjected to bending and/or torsion to verify the proposed formulation of the stress-strain relationship of the encased concrete.
