Impact response of SCS sandwich slabs with ultra-high performance concrete: Failure mechanism and influence of shear connector configuration

In the typical steel-concrete-steel (SCS) sandwich structure, the normal-strength concrete core fills the external steel skeleton. This paper describes a program of drop-weight tests and finite element investigations on reduced-scale SCS sandwich slabs with ultra-high performance concrete (UHPC) core material as a novel protective layer construction. Test results demonstrated that the steel-ultra-high performance concrete-steel (SUHPCS) sandwich slabs were adequate for forming enhanced dynamic resistance through the high strength of UHPC and tensile stiffening membrane of the steel skins. Also, this construction was found to perform a highly ductile behavior and sustain obvious bulges without penetration through the whole slab. Precise finite element models for sandwich slabs under impact loading conditions were established and the simulated time histories were verified against the test data. Furthermore, a parametric study of sandwich slabs designed with different configurations of shear connectors was subjected to a spherical hammer weighing 540 kg dropping from the height of 5 m. The simulation results showed that the failure mode of SUHPCS sandwich slab changed with various degrees of composite interaction. Moreover, a theoretical methodology was proposed to classify the failure mode involving stiffness, flexural and punching resistances. SUHPCS sandwich slabs with a reasonable layout of shear connectors were found to provide a means for effective energy absorption against severe impact attacks.