Plasticity-based evaluation method for in-plane shear strength of steel-plate composite element

•A model for evaluating in-plane shear strength of SC wall is proposed.•The upper bound theorem is used to develop the model.•The derived equation has a simple form.•The model has good computational accuracy. The steel-plate composite (SC) wall is considered an attractive structural type for the next generation nuclear power plants because of its efficient construction schedule, radiation shielding function, and excellent mechanical properties. During seismic action, the SC walls sustain large in-plane and out-of-plane loadings. So, it is essential for the evaluation of the in-plane and out-of-plane load carrying capacity of SC walls in design. Up to date, several equations that are developed based on elastic theory are proposed and adopted by relevant design codes. In the previous study by the authors, a lower bound equation was present for evaluation of the in-plane shear strength of SC elements based on the lower limit theorem of plastic limit theory. As a counterpart to that paper, an upper bound equation for evaluation of in-plane shear strength of SC elements based on the upper limit theorem of plastic limit theory was developed, and its minimum value solution which is the closest one to the exact solution was derived. Meanwhile, considering that concrete is not a perfectly plastic material, another equation is present to prevent the concrete between the steel faceplates from crushing prior to the steel yielding. A comparison between the results predicted by the proposed equation in this study and the test results of the SC panel specimens suggested the adequacy and accuracy of the proposed equation. In addition, comparisons of results evaluated by the proposed equations and the equations in codes JEAG 4618 and AISC N690 were also performed.