Theoretical models for axially restrained steel-concrete-steel sandwich panels under blast loading

•Theoretical model of SCS sandwich panel under blast loads was established.•DIF in terms of strain rate was included in SDOF and Lagrange Equation model.•FE method was adopted to verify the theoretical model.

Two approaches for predicting the responses of axially restrained Steel-Concrete-Steel (SCS) sandwich panels subjected to blast loads are reported in this paper. The tensile membrane action of steel faceplates in the SCS sandwich panel is considered in these models. In the first approach, the SCS sandwich panel is idealized as a Single-Degree-of-Freedom (SDOF) system. The resistance-deflection function of the SCS sandwich panel is derived in which the resistance by concrete core is evaluated by utilizing the energy principle. Subsequently, the Lagrange Equation approach is proposed since it is allowed to define more than one deflected shape functions and therefore can capture the varying deflected shape of SCS sandwich panel during motion. The strain rate effects of steel and concrete have been accurately captured by calculating the Dynamic Increase Factor (DIF) of steel and concrete based on the varying strain rate during motion. The Finite Element (FE) analysis is carried out to verify the two proposed approaches and good agreement is observed.