Investigation of support type effect on plastic hinges in RC beam under impact load

摘要

This study investigates the effect of support types on plastic hinges in reinforced concrete (RC) beam under the influence of impact loading. In previous studies, the assumption of the linear distribution of inertia force under impact loading was examined and verified according to experimental, analytical, and numerical results. Furthermore, it was emphasized that the most important parameters affecting the behavior of RC beams under impact loading were plastic hinges. A three-stage study was planned to investigate this subject. The first stage was an experimental study. In this part, four RC beams with simple and fixed supports were tested under the low-velocity impact load with two different impact energy levels by using a free-weight test setup with advanced measurement techniques. The time histories of the accelerations, the displacements, and the impact loads acting on RC beams were recorded, and the cracks from impact loading were observed. The dynamic responses obtained from experiments have been interpreted in detail. The most important issue about plastic hinges was that the hinges do not reach the supports and remain on the beam. This is valid for both hinge support and fixed support. In the second stage of the study, an explicit numerical analysis model, which was verified with experimental results, was developed. The clear agreement between the experimental and numerical results was demonstrated. It has been concluded that proposed finite element procedures can be used for evaluation of the dynamic responses and failure modes of RC beams under low-velocity impact loading. The last part was an analytical study. In this part, the proposed analytical procedure in the previous studies considering the plastic joint formed in a simple support beam under impact loading was confirmed, and a new coefficient for fixed support was proposed. A good agreement has been achieved between analytical and experimental work.