Out-of-plane shear strength of steel-concrete sandwich panels

Steel-concrete-steel (SCS) sandwich panels consist of two steel plates connected with tie bars filled with concrete; composite action is achieved using headed studs in the plates. This form of composite construction has recently regained interest in the construction industry as it allows modular construction and decongestion of reinforcement which is particularly useful in large infrastructure such as tunnels, wind turbines and nuclear energy facilities. This paper investigates the out-of-plane shear resistance of SCS panels without shear reinforcement. In practice, the spacing between tie bars acting as shear reinforcement can be significant and the shear resistance is governed in some cases by that of a member without shear reinforcement. A qualitative comparison of the shear transfer actions is presented between SCS and conventional reinforced concrete (RC) members without shear reinforcement. Existing design formulae for shear in RC are applied to existing experimental data of SCS panels. This study shows that the shear resistance models for RC give conservative predictions of strength of SCS slender panels with low or medium levels of shear connection at the interface between the concrete and the steel. This inbuilt conservatism is due to the bond-slip of the interface resulting into a concentration of the flexural cracks towards mid-span which allows the development of full arching action (shift of Kani’s valley). A strut-and-tie model is presented for SCS which provides more accurate predictions of strength in such cases and also in other cases such as short-span members (discontinuity region).