The Earthquake Resistant Control Analysis On Twin Towers Cable-stayed Bridge-TMD System

Safety of human life and property is often threatened by earthquake. The high-frequency occurrence of bridge failure caused by earthquake results in delay in relief work and further deepens effects of serious secondary disasters. Earthquake resistance of bridge structure plays an important role in the lifeline earthquake engineering. And cable-stayed bridges, as a typical bridge type developed fast in recent years, are extensively applied. Therefore, the anti-earthquake study of cable stayed bridges is important and should be paid more attention to.Tuned mass damper (TMD), as a vibration-control method of clear principle, simple form and convenient installment, has been largely applied in civil construction and got a good effect of application. Yet the application of TMD to the cable stayed bridge system still exists many problems solved and is worth studying deeply.On the engineering background of a certain twin-tower cable stayed bridge in Dongying city of Shandong province, by using the small-scale model test and finite element numerical calculation, based on the TMD test of vibration-mitigation characteristics, the damping effect of the bridge-TMD system is studied in this paper under the conditions of different ground motion excitations, mass ratios of TMD, geometrical distributions of TMD, damping ratios of TMD, and so on. The main content of the paper is as follows:For giving a theoretical support for methods of experimental and numerical analysis adopted in this study, the major recent development of vibration control of bridges at home and abroad and the related results were carefully examined. And the principle of TMD and the relevant optimization design were summed up.Considering the different research focuses of the small-scale model test and the finite element analysis, the finite element model for test (FEMT) and that for the actual background bridge (FEMB) were built respectively. For FEMT, the preliminary study before testing and the extensive analysis after testing could both be performed. For FEMB, the simulated damping effects could be analyzed under different excitation hypotheses, distribution setups and characteristic parameters of TMD and so on.The damping characteristics study of TMD was addressed in the small-scale model test. Specifically, the effect of the tuned TMD on the response of the bridge model was studied during the free attenuation period of the model; And combining the numerical results from the finite element analysis under harmonic excitations, the damping characteristics of the TMD installed on the bridge model was much better understood and grasped. Based on the analysis in the model test, on the platform of FEMB, a contrast analysis was made under different vibration excitations and setups of TMD. The analytical results not only prove the effect of TMD on mitigating the response of the bridge, but also initially reveal and analyze some new features that appear in the process of the TMD-based vibration control of this bridge.