The Mechanical Properties of Reinforced Concrete Plate-Girders when Placed Under Repeated Simulated Vehicle Loads

The effect of vehicle loads on reinforced concrete plate-girders was evaluated using the current Chinese specifications. Repeated loading performance tests with loading amplitudes of 77 kN, 97 kN, and 121 kN, which correspond to the standard vehicle load, 1.25 times overload, and 1.6 times overload proportions effect were carried out on three full-scale simply-supported reinforced concrete plate-girders. Our research results indicate that the development of cracks in reinforced concrete beams can be divided into three stages: rapid development, stability, and failure. During the entire process, the strain of steel and concrete did not reach their yield strain. The most severe damage done to the concrete beams was the brittle fractures caused by the fatigue fracturing of the rebar. When in a stable condition, the extent to which the vehicle was overloaded had a significant effect on the fatigue performance of the beam, and the corresponding residual deflection and residual strain increased with the rise in the overload proportion. In addition, as the overload proportion increased, the stiffness degradation and the cumulative damage that occurred under the same loading cycle was more significant. The test beam reached failure after being subjected to 350,000 and 670,000 repeated loading cycles, when the load was 1.6 times and 1.25 times of the standard load effect. With a standard vehicle load effect, the test beam was able to endure 2,000,000 repeated load cycles with no significant degradation in stiffness and bearing capacity.