Behavior of steel-concrete-steel sandwich slabs subject to impact load

This paper investigates the impact behavior of sandwich slabs which consist of a lightweight concrete core sandwiched in between two steel plates inter-connected by J-hook connectors. Special lightweight concretes of density 1450 kg/m³ and interlocking J-hook mechanical connectors have been developed for this purpose. Impact tests were carried out using an instrumented drop weight machine. Test data such as deflection- and impact force-time history and permanent deformation after impact were reported. Test observation showed that J-hook connectors provide an effective means to interlock the top and bottom steel face plates preventing them from separation upon impact. Steel fibers were added into the concrete core of selected test specimens to evaluate their effectiveness in reducing the brittleness of concrete due to dynamic loads. Using elastic-plastic analysis, analytical expression has been derived to predict the load-indentation relationship on the sandwich slab caused by the drop weight. It is then used in an energy balance model to predict the global response of sandwich slab subjected to impact load. The predicted results were compared with the test results so that the model can be validated for use to assess the impact performance of composite sandwich slabs.