Study On Design Method Of BRB-based Shock-absorbing And Anti-collision System On Railway Simply-supported Girder Bridges With Unequal Span

In recent years,with the rapid development of railway construction and bridges in China,the seismic performance of railway bridges has increasingly been concerned.In this paper,aiming at the limitations of traditional shock absorbers,a new type of "BRB+cable limiter" system with shock-absorbing and anti-collision,based on the "performance design principle" and "function separation idea",was proposed for simply-supported girders with unequal span of railway.The main contents of this dissertation are described as follows:(1)Based on the comprehensive reading and understanding of related literatures on the research of seismic isolation bearings and shock absorbers,the status of pounding effects,anti-collision and falling-off prevention measures of bridges,the design principles of functional separation and the specific application of combined shork-absorption systems in the field of bridges were reviewed and summarized.(2)The structure of the shock-absorbing and anti-collision system and the working mechanism of the BRB were introduced.The numerical simulation methods of the shock-absorbing and anti-collision system were reviewed and evaluated.The reliability of the numerical model was verified based on the existed BRB component experiments.The Steel MPF model can accurately simulate the five basic characteristics of BRB hysteretic behavior.(3)The influence parameters of the ductility and energy dissipation performance of the shock-absorbing and anti-collision system were analyzed.The orthogonality test method was used to determine the major and minor effects of the parameters.And the reasonable structure of the system was selected.(4)Based on the two DOF calculation model of the simply supported beams with unequal span of railway,the Open Sees finite element software was used to analyze the pounding at the bridge expansion joints.The nonlinear time-history seismic response analysis method was used to analyze the pounding effects between adjacent beams and beam-pier under longitudinal earthquake of the simply supported beams with unequal span.The effects of the shock-absorbing and anti-collision system on the simply supported beams with unequal span of the bridge structure were discussed,especially the seismic characteristics of the transition pier.The influences of parameters,such as the mechanical parameters of the BRB,the height of the transition pier and the gap size of the expansion joints on the shock absorption performance of the shock-absorbing and anti-collision system were discussed,and suggestions for reducing the pounding and the relative displacement of the pier-beam were proposed.(5)Taking the simply supported beams with unequal span of railway as an example,a simplified design method of the shock-absorbing and anti-collision system was proposed based on the performance design principles of BRB and cable limiter,and the effectiveness of the procedure was evaluated by nonlinear time history analysis.