Strength analysis of semi-rigid steel-concrete composite frames

This paper proposes an efficient, robust and accurate method for geometric and material non-linear analysis of concrete-steel composite frames allowing for semi-rigid connections. The new element stiffness matrix of a composite beam-column element with connections at ends is formulated by an efficient numerical integration scheme allowing for shift of the neutral axis, variation of the axial strain, concrete cracking and steel yielding along the element. The use of many elements per member, which involves complication in simulation of the shift of neutral axis and computational deficiency, is avoided. Previous methods based on an approximate finite element formulation cannot cater for all these important parameters. A semi-analytical model for determination of the stiffness of composite joint under sagging and hogging moments is proposed. The accuracy of the proposed analytical scheme is illustrated by numerical examples.