Behavior Of Steel–Concrete–Steel Sandwich Beams And Panels Under Off-Center Impact Load

Due to increasing concern about the performance of the structures under extreme dynamic loadings(i.e.,impact and blast),Steel-Concrete-Steel(SCS)structures have become popular among researchers and structural engineers.SCS sandwich structures also possess enormous advantages over the conventional Reinforced Concrete(RC)structures,such as high strength and ductility,economical,ease of construction due to pre-fabrication.Though several types of research have been conducted on the SCS sandwich structures,limited research exists on the impact behavior of the SCS sandwich beams.Moreover,previous works considered impact at the center of the specimens.In real events,the accidental or targeted impact loads on the structure may occur at any location during its life.Hence,in this study,the structural performance of the SCS sandwich beams and panels with bolt connectors subjected to off-center impact load was investigated.Firstly,nine SCS sandwich beams were tested under hemi-spherical drop hammer impact.The influences of the thickness of concrete core,thickness of steel plates,top to bottom steel plate thickness ratio,and location of impact were studied.Three types of failure,namely,flexure,flexure-shear,and fracture of the bottom steel plate,were observed from the tests.It was found that the presence of bolt connectors prevented the tensile separation of steel plates,and the structural integrity of the SCS sandwich beams was maintained despite the impact near the support.Secondly,an analytical model was developed to predict the displacement–time histories of the SCS sandwich beams with bolt connectors subjected to impact load and validated with the test results.The predicted displacement responses showed a good match with the experimental displacement–time histories.Thirdly,a three-dimensional Finite Element(FE)model was developed using the non-linear explicit code in LS-DYNA to predict the impact behavior of SCS sandwich beams with bolt connectors.The accuracy of the developed FE model was established by comparing the FE predicted failure modes,peak impact forces,maximum and residual displacements,and impact force and displacement – time histories with those from the experiments.The FE parametric studies were carried out to investigate the influences of different parameters i.e.,spacing of connectors,strength of concrete,presence of endplates,location of impact,mass of drop weight,and height of drop.Finally,a numerical model of the SCS sandwich panel was developed using LSDYNA software,and the off-center impact behavior of the SCS sandwich panels with bolt connectors was explored.Also,an analytical model to predict displacement response of SCS sandwich panel with bolt connectors was developed.