Study On Traveling Wave Effect Of Shape Memory Alloy-Friction Isolation Multi-span Bridge

In response to the current demand for socio-economic development,the number of large-span bridges under construction and to be built has gradually increased.With the increase of structure length and span,the traveling wave effect of seismic response becomes more and more significant.Therefore,it is necessary to consider the effect of seismic traveling wave effect in long-span structure earthquake-resistance design.In this paper,the use of shape memory alloy(SMA)-friction bearings for isolation of long-span bridges was designed,and the effect of traveling wave effect on the seismic effect of isolated bridge structures was studied.(1)Validated the multi-segment linear constitutive model of SMA with the test and used FORTRAN and UMAT subroutines to embed the constitutive model in ABAQUS software.The effects of friction coefficient,yield displacement,and SMA stiffness on the damping and self-recovery of the bearing were studied by finite element method.The results show that: With the increase of the friction coefficient,the damping performance of the bearing is enhanced and the self-recovery performance is weakened;With the increase of SMA stiffness,the damping capacity of the bearing decreases,and the self recovery performance increases.With the increase of SMA yield displacement,the damping capacity of the support has no significant change,and the self recovery performance has decreased.The result can provide guidance for the optimization of parameters of SMA-friction bearings.(2)Aiming at six-span SMA-frictioned continuous girder bridges,a numerical model was established and its modal and seismic responses were analyzed.The modal analysis show that: The first two modes of the bridge after isolation are mainly represented by the lateral drift and longitudinal drift of the bridge,while the first two modes of the bridge without isolation are mainly represented by the lateral bending and longitudinal bending of the bridge.The results of seismic response analysis show that: The effect of earthquake on the superstructure of isolated bridge decreases obviously.Compared with the response of the bridge under the unified excitation,when considering the traveling wave effect,the acceleration of the bridge,the shear force at the bottom of the pier and the peak value of the relative displacement response of the isolated bridge are all significantly increased.When the site type changes from a Class I site to a Class IV site,the peak value of peak shear response and relative displacement response of the seismic isolation bridge considering the traveling wave effect increase,and the peak acceleration response of the bridge decreases.(3)The influence of the variation of the pier height,the span of the bridge and the input direction of the seismic wave on the seismic response of the SMA-friction isolating bridge was studied.The results show that: the increase of pier height increases the peak shear response at the bottom of the pier and the acceleration response at the top of the pier,and the peak acceleration response of the bridge decreases.The increase of the bridge span increases the peak value of peak shear force and relative displacement at the bottom of the pier,and the peak acceleration of bridge deck decreases.Changing the input direction of the seismic wave will affect the seismic response,and the seismic response of the transverse bridge is more significant than that of the longitudinal bridge.