Experimental study on stiffness deterioration of cracked RC hollow-core slab beams

To accurately assess the performance degradation of RC hollow-slab beam after service, in-situ static load tests were carried out on a RC hollow-slab beam bridge with a span diameter of 11.25 m, which is part of the Chongqing–Chengdu Highway Viaduct. Indoor single-girder static load tests were also carried out to study the deflection concrete strain and reinforcement strain at key locations on the hollow-slab beam. Crack development was recorded to investigate the stiffness degradation law of hollow-core slabs. Inverse secant stiffness–residual deflection and inverse secant stiffness–maximum crack width relationship models were established. Results show that the calibration coefficients obtained in the in-situ static load tests were greater than one, indicating potential for stiffness deterioration and insufficient structural safety reserves during service. The initial crack width was increased and extended upwards before the test beam yielded, with many new vertical cracks in the pure bending zone which extended continuously. The slope of deflection curve was larger before yielding and smaller after yielding, the secant stiffness of RC hollow-slab beam was exponentially decreased with load before yielding and changed linearly with load after yielding. The inverse secant stiffness–residual deflection and inverse secant stiffness–maximum crack width curves of the test beam were approximately bilinear, with a larger slope at the beginning of the test and a smaller slope in the plastic phase.