DYNAMIC TESTS OF CONCRETE REINFORCING STEELS.

Dynamic tests were conducted on four grades of concrete reinforcing steel a A15 intermediate grade, b A15 hard grade, c A432 60,000-psi minimum yield strength, and d A431 75,000-psi minimum yield strength. The effects of strain rate up to 1.7 in.in.sec and machine testing speed up to 30 in.sec on the upper stress and tensile strength of each steel were obtained. Results are compared with other dynamic tests conducted on concrete reinforcing steels. The mechanical properties of all four grades of reinforcing steel either remained unchanged or exhibited an increase in value as the rate of testing increased. At the maximum strain rate, the percentage increase in upper yield stress was 53, 42, and 18 and the percentage increase in lower yield stress was 29, 27, and 11 for the A15 intermediate, A15 hard, and A432 grades of steel respectively. The increase in yield stress was 9 percent at the maximum strain rate for the A431 steel. The hard-grade steel showed the greatest increase in tensile strength 12,000 to 13,000 psi. The remaining steels had approximately the same increase in tensile strength about 9,000 psi. Small increases in ductility were observed for the A432 and A431 steels. Design recommendations are given for yield stress values in terms of strain rate for the grades of reinforcing steels tested. Author