Influence of loading rate on bond behaviour of reinforcing steel and prestressing strands

Pull-out tests with short embedment length were carried out within a wide range of loading rates. The highest loading rate which could be achieved on a Split-Hopkinson-bar equipment was about 500,000 times the loading rate in a static test. The test variables were the steel type, the concrete quality and the loading rates. It turned out that plain reinforcing bars and prestressing strands were insensitive to variations in the loading rate, whereas deformed bars showed a significantly higher bond resistance with increasing loading rate. This influence is more pronounced according as the concrete quality is lower and the bar displacements are smaller. An explanation of the phenomena is suggested.