Effective stiffness of composite shear wall with double plates and filled concrete

Shear walls are the primary lateral load-carrying elements in tall buildings. The composite shear walls with double steel plates and filled concrete are composed of two steel plates with studs inside, side columns made of steel tubing, and an infill of concrete. They were developed to enlarge the building space, and to delay the appearance of cracks by using the steel plates as formwork. This paper focuses on the effective stiffness of the composite shear walls. Despite many design practices addressing the shear stiffness by employing a stiffness reduction factor, a model named as plane combination truss model (PCTM) for the effective shear stiffness of the composite wall is proposed based on the theory of the fixed angle truss model in this paper. The formula for calculating the effective shear stiffness of the composite shear wall is derived based on this model. The total effective stiffness is obtained by combining the effective shear stiffness and the effective flexural stiffness, in which the flexural stiffness can be obtained by the fibre model. The predictions for the effective stiffness correlate well with the results of a series of tests on composite shear walls.