Experimental investigation of dynamic response of full-scale RC beams under high-energy impact

Abstract

Most impact tests of reinforced concrete (RC) structures are small-energy and reduced-scale tests. Due to the size effects under strain rate, there are large differences in the dynamic responses between reduced-scale and full-scale tests, which makes it inappropriate to design full-scale structures under impact loading based on reduced-scale test results. This paper presents the first results to compare the effects of drop weight impact tests on reduced and full-scale reinforced concrete (RC) beams. The experimental results are used to identify limits of applicability of the similarity laws that have been developed based on low-energy impact tests on reduced-scale structures. Due to low stiffness of the reduced-scale specimens, their failure mode is typical of bending. In contrast, the full-scale specimens have much higher bending stiffness and therefore are more prone to shear failure. Since the ratio of impact force to reaction force decreases as the geometric dimensions of RC beams increase, it is likely that the reaction forces of full-scale RC beams inferred from theories based on the reduced-scale impact test will be lower than in real situation, which could lead to unsafe design. The existing effective length analysis method only considers the stage before the impact force reaches the peak value and cannot deal with the change in effective length of full-scale RC beams with nonlinear deformation. The current theory of energy for impact test that considers the total mass of the structure cannot accurately reflect the effect of full-scale tests in which the loss of energy of the structure is much higher than the absorbed energy. The energy analysis method for full-scale structures is more reasonable when considering the effective mass. The guidance of reduced-scale test is not applicable in full-scale test, and the large deviation of forces between the reduced-scale and full-scale structures by using the DLV systems. To rectify these problems, this paper proposes a similarity law for GVH systems.