In general, transition in the mode of failure from flexure failure at the static loading to shear failure at low velocity impact in reinforced concrete (RC) beams has been reported in the literature. To quantify the above-mentioned statement, a drop-weight impact test program was carried out on RC beams. The test results showed that no shear failure has been occurred under impact loading in statically flexure-critical beams (i.e., shear to bending resistance ration greater than one) however with increasing drop-heights more localized failure with extensive concrete crushing at the impact region was observed. Impact interface (i.e., direct impact or with some interface such as steel or plywood plate in between impactor and beam) could be one reason that the change in failure mode has not been observed in the current test program. To simulate the structural impact response in details, a three-dimensional nonlinear finite element (FE) model was also developed. Numerical results agreed well with the test results obtained from current test program and also from the literature. Finally, the numerical model was used to conduct parametric studies to evaluate the effects of design parameters (e.g., ratio of beam- mass to impactor-mass, longitudinal reinforcement ratio, compressive strength of concrete and boundary conditions etc.) on impact responses and failure modes.

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The behaviour of reinforced concrete (RC) beams under single or repetitive drop-weight impact loading has come under increasing attention within the engineering community in the past decades. However, until now, little effort has been sought towards examining the residual resistance of RC beams after impact damage. To contribute towards a better understanding in this area, both experimental and numerical investigations were carried out. The beams were first tested under drop-weight impact loading. Subsequently, quasi-static bending tests were conducted on the same specimens to obtain the residual behaviour. Thereafter, one beam from each series without any prior damage was tested under monotonic static loading to compare its behaviour with impact-damaged specimens. Furthermore, to investigate the structural response in detail, a numerical procedure was developed in an explicit finite-element program. Upon successful validation of the numerical results with the experimental outcomes, numerical case studies were carried out to quantify the variation of residual resistance index in terms of various parameters.

Based on a comprehensive literature review, a state-of-the-art report on the strain rate dependent mechanical properties of materials involved in reinforced concrete (RC) structures and the structural response of RC beams under low-velocity impact is presented. Due to the prevalence of plentiful equations to calculate the dynamic increase factor of concrete strength in compression and tension, future research is needed to reach a general consensus. Two empirical equations were derived based on previous test data, and the applicability of the proposed equations is demonstrated. With the interpretation of previous data in the light of authors' test results, the issue related to a change in failure mode from flexural failure under static loading to shear failure under impact loading is discussed. Finally, several issues related to the impact response of beams are raised, and the need for future research is identified.