Study On Theory Of Using Magnetorheological Damper To Control Seismic Response For Long-span Bridge

With the development of social economy and traffic transportation, many long-span bridges on rivers, lakes, and straits have been constructed. To ensure bridges safety under earthquake and prolong their life, study on theory of controlling seismic response for long-span bridge is essential and significant.It exists some problems for existing devices to reduce seismic response such as rubber aging and metal rustiness. These problems can be solved through magnetorheological (MR) damper. In addition, MR damper has lots of advantage such as more simple structure, less dissipation energy, larger damper force and quicker response rate over existing devices. Based on geometrical non-linear finite element method and time history analysis method, the theory of using MR damper to control seismic response for long-span bridge is established and simulation analysis of bridge structure with MR damper is completed. This is a new study. The main contents and achievements are as following:1. Based on the virtual work increment equation of updated Lagrangian formulation, tangent stiffness matrices of spatial beam/truss element and the spatial two-node catenary cable element are developed, a fine method of calculating end force of beam element is improved, and an exact formulation of end force of cable element is put forward. Therefore an entire geometrical non-linear finite element theory for the structure made of beam, truss and cable elements is established.2. Based on 1, the time history analysis method about spatial non-linear seismic response analysis for long-span bridge is proposed, and the program SRALB is compiled with Fortran.PowerStation 4.0 software. The program SRALB can be used in aseismic analysis for long-span bridge, and provides a base for study on seismic response reduction.3. By comparison and analysis, a mechanical model of MR damper, i.e., proposed phenomenological model, which predicts the non-linear behavior of the damper very well, is selected from several mechanical models, and is used to control seismic response for long-span bridge. A module to analysis seismic response reduction for long-span bridge is designed. Therefore the simulationanalysis for bridge structure with MR damper is completed. The results of simulation examples show that MR damper is effective on controlling seismic response of the structures.4. Applying the program SRALB, the seismic response for the Maocaojie Bridge, a concrete filled steel tube arch bridge in Yiyang Hunan province, is carried out. Thereby the function and reliability of the program are validated. The results show that existing design blue print of the Maocaojie Bridge can adequately take on earthquake load. Vertical excitations and traveling seismic excitations have much effect on seismic response of concrete filled steel tube arch bridge like the Maocaojie Bridge so that they can not be ignored, but geometrical non-linear has little effect.5. Utilizing aseismic module mentioned in 3, the study on seismic response reduction for the Pingsheng Bridge, self-anchored suspension bridge with single-tower in Foshan Guangdong province, is completed, and the influence on seismic response for different electric current, number, fixed place of MR damper is discussed. The results show that displacement responses decrease gradually, and inner force responses are effectively controlled when the current or the number of MR damper increases. The effect of seismic response reduction is optimum when all MR dampers are fixed between tower and girder. Aseismic analysis shows that different juncture situations between tower and girder have much effect on seismic response of the structure.