In this paper, the results of a comparative study on diagonal strut models are presented to simulate the in-plane behavior of concrete sandwich panels enclosed in a steel frame. After a brief overview of experimental tests on the cyclic in-plane behavior of Concrete Sandwich Panel-Infilled Steel Frames (CSP-ISF), a 2D finite-element model is developed through DIANA software. Then, CSP-ISF structures are modeled using macro-modeling approaches available in the literature and known as the diagonal strut model, to compare the results of the numerical analysis with experimental data. The results show good consistency of Liauw and Kwan model with the experimental response of CSP-ISFs. Finally, modified formulas including reduction factors of the lateral stiffness and ultimate strength are proposed to estimate the in-plane lateral behavior of CSP-ISFs with a central opening, i.e., perforated infilled frames.
