Comparative Study On Analysis Method Of Seismically Isolated Girder Bridge

At present,nonlinear time history analysis method and multimodal response spectrum analysis method are used in seismic calculation of seismically isolated bridges.The nonlinear time history analysis method can consider the influence of a variety of factors and is a more detailed analysis method at present.For a determined seismic wave,the nonlinear time history analysis method can accurately calculate the seismic response of the structure,but for different seismic waves,the result is more discrete.So this method needs a lot of calculation and statistical analysis of the result,in addition,the selection of structural damping form has great influence on the calculation result.Thereby,for more regular seismically isolated bridges,researchers at home and abroad are exploring more convenient calculation methods.Single modal response spectrum analysis method has been written into the specifications of China and America.On the basis of the existing research work,this paper studies the equivalent linearization method in connection with our country's bridge seismic specifications.The main research work is as follows:1?The single modal response spectrum analysis method based on a single degree-of-freedom model of the bridge and the double modal response spectrum analysis method based on a 2 degree-of-freedom model of the bridge are studied.The origin of the equivalent mass formula is summarized.The equivalent coefficient of mass and its correction are derived and analyzed.The formulas for the calculation of the second modal period and the amplitude of the beam are given.The different seismic response calculation methods are compared and analyzed.2?A number of double column pier bridge cases are calculated.Based on the multimodal response spectrum analysis method,the accuracy and scope of application of the equivalent linearization method are discussed,and compared with Calculation results of nonlinear time history analysis method3?For different pier height of seismically Isolated Bridge,the first modal and second modal vibration characteristics were studied.The applicability of the double modal response spectrum analysis method based on a 2 degree-of-freedom model of the bridge is analyzed.4?In the general seismically isolated bridge,the double modal response spectrum analysis method based on a 2 degree of freedom model of the bridge is used to calculate.The calculation accuracy of the basic period,the second modal period,the displacement of the beam,the displacement of the pier top,the displacement of the isolator and the shear of the bottom of the pier is higher.The calculat ion result of the bending moment of the bottom of the longitudinal pier is large.When the cross beam is set between the piers of two columns,the accuracy of the calculation results of the internal force of the lateral structure is reduced.