Structural behavior of the steel fiber reinforced concrete beam under multiple impact loadings: An experimental investigation

Steel fiber reinforced concrete (SFRC) has been proved to be an appropriate material to resist extreme dynamic loadings. To explore the structural behavior of the SFRC component under multiple impact loadings, eight beams with continuous rebars were tested with a drop hammer system. Crack patterns were observed while strains of rebar and concrete, deformation of beams, the impact and reaction forces as well as acceleration were recorded during the experiment. The structural performances were analyzed, and influences of steel fiber amount, stirrup ratio, concrete strength and the times of impact loading were discussed. The test observations indicated that compared with ordinary RC beams after the first impact, crack patterns of SFRC beams were changed from punching-shear to bending and the peak mid-span deflection is considerably reduced. Under multiple impact loadings, the crack patterns of SFRC beams are mainly determined by the first blow, and few new cracks will be generated by the subsequent loadings. The increment of maximum mid-span deflection, however, increases as the number of blow increases. The shapes of deflection curves and distribution of internal force (dynamic shear force) for SFRC beams under multiple impact loadings are significantly different from those under static loadings. Moreover, the magnitude of the shear force slightly increases while the peak impact force decreases with the increasing of impact times. With the increasing steel fiber amount, impact force and energy absorption capacity of SFRC beams were increased while the residual deflection was reduced.