Experimental study on the dynamic response characteristics of reinforced concrete hollow slab beams after 27 years of service

To clarify the dynamic response characteristics of RC hollow slab beam that are currently in service, the degree of damage they undergo, using dynamic response parameters, is evaluated, as well as the damage itself. This study took the ninth span of the Cheng-Yu Highway Viaduct at the Shangqiao Interchange—which has been in service for 27 years—as the research background. By analyzing the results of bridge damage monitoring over the past 10 years, and in situ dynamic load tests and indoor single girder tests were conducted to study the dynamic response characteristics of the full bridge, including its fundamental frequency, impact coefficient, single-girder vertical bending vibration pattern, and vertical bending frequency. The research shows that RC hollow slab beam that are in service for as many as 27 years tend to suffer from water seepage in their hinge joints and concrete cracking in their bottom slabs. In-situ dynamic load test results showed that the fundamental frequency and impact coefficient of the bridge were slightly larger than the theoretical values. With the accumulation of beam damage, the vertical bending vibration frequency significantly reduces. The vertical bending frequency reduction rates of three test beams were similar, and the influence of structural damage on the structural vibration pattern was significant. Structural vibration pattern deformation became more serious as structural damage worsened. Finally, a model of RC hollow slab beam stiffness versus frequency was created via fitting.