Sandwich panels are commonly used in facades and the roofs of industrial buildings due to their well-known advantages. However, there is limited data about the in-plane behavior of the panels. Hence, this paper aimed to propose a pseudoelastic truss model to represent the effective in-plane stiffness and strength properties of the corrugated sandwich panels with a polyurethane foam core. Two separate sets of experiments (mock-up and system test) were conducted in the laboratory. The variables were the number of fasteners, sheet thickness, loading direction, and number of ribs. The number of fasteners, sheet thickness, and loading direction are the most effective parameters for the in-plane behavior. A formula was proposed to compute axial stiffness of the truss members by considering the effective parameters. Experimental results showed that the proposed robust truss model could give a good estimate of the pseudoelastic stiffness and maximum load bearing capacity of the sandwich panels.