Study On Placement And Parametric Optimization Of Distributed TMDs For Seismic Control Of Cable-stayed Bridge

A cable-stayed bridge has low structural damping and large flexibility. Significant vibrations of superstructure will be caused easily and produce large internal forces at key positions under seismic loads, which may lead to structural damage and failure. Control measurements such as installing TMDs (tuned mass dampers) will be necessary for the mitigation of seismic responses. As a large flexible space structure, cable-stayed bridge has complicated static and dynamic characteristics, and has low order and closely spaced frequencies. Distributed TMDs are utilized for the multi-mode control of the structure. To resolve the two problems of placement and parameter optimization of the TMDs, this paper investigates a placement optimization method based on H2norm expressed with modal coordinates and a parameter optimization method based on H2performance criterion with gradient-based optimization. The main contents are as follows:1. Placement index of TMDs based on H2norm expressed with modal coordinates is proposed considering influence weight of exterior excitation. System model combined the structure with the distributed TMDs is established, which represents a closed loop system with a decentralized static output feedback control action. And a method based on H2performance criterion with gradient-based optimization is developed to optimize the parameters of the distributed TMDs.2. An ideal structure model with three degree of freedoms and closely spaced frequencies is taken as an example to study the design of the distributed TMDs. A nondimentional performance index is defined to optimize modal control weight that formes the control output, through which a relatively universal weight could be optimized. The parameter optimization and control effect of the distributed TMDs are simulated. Comparing with the classic method, results shows that more efficiency of the distributed TMDs for the seismic control can be achieved for the developed method.3. Focusing on a cable-stayed bridge under construction and its completed state respectively, the control design models are established, and analysis on dynamic characteristics and seismic responses of the cable-stayed bridge are achieved. Optimal number and location of TMDs to be installed are analyzed quantitatively by using configuration index based on H2norm; parameters of the configured TMDs are optimized by H2optimization method and classic optimization method. The seismic responses of the cable-stayed bridge under construction and its completed state subjected to different excitations are simulated and analyzed, and results show that TMDs optimized by the H2method can achieve more efficiency for seismic control of cable-stayed bridge with closely spaced frequencies.