| Continuous beam-arch composite bridge is a combination of force and beauty,it has the characteristics of both beam bridge and arch bridge,such as good mechanical performance and strong spanning ability,so it has been widely used in railway engineering in China.For this type of bridge,longitudinal fixed support is usually set in one of the main piers of the bridge,and longitudinal movable support is set in the rest piers to meet the deformation and mechanical performance requirements of the bridge.For long-span railway bridges with large temperature span,more rail expansion joints need to be set at the beam ends,which would affect the ride comfort and comfort of train running.Moreover,under the earthquake,the longitudinal load is borne by the fixed pier,which is a weak part,and the piers are in a state of uneven stress.Based on this,a new constraint system,collaborative constraint system,was proposed in this paper.The system replaced the conventional bearings at the top of the main piers with the elastic constraint multi-function bearing with adjustable limit gap,so as to achieve the "cooperative force and cooperative deformation of each pier;Combined anti-push,coordinated anti-seismic " design purpose.The research work of this paper is as follows:(1)Based on a long-span railway prestressed concrete continuous beam-arch composite bridge with the span of(31.55+168+31.55)m,full-bridge analysis models are established for the bridge structure under two constraint systems by using bridge finite element analysis software,and the static analysis of the bridge structure under two constraint systems is carried out.The results show that the vertical displacement,internal force and stress distribution of the bridge superstructure are basically consistent with those of the original constraint system,and the longitudinal deformation of the structure is more symmetrical and uniform.The peak value of the longitudinal deformation is reduced by 13.48%～15.46%,and the peak value of the bearing is reduced by 29.36%.(2)The dynamic characteristics of the structure under the two constraint systems are compared and analyzed.The results show that the cooperative constraint system does not change the fundamental frequency of the bridge.In the second order modal,longitudinal drift occurred in the main beam,collaborative constraint system under two main piers with produce along the bridge to the bending moment,and the natural vibration period of the structure increases,which shows that when the vertical load is dominant,two pier and girder in collaborative to resist the load together,and the natural vibration period increases,in order to minimize the earthquake effect of the influence of the structure.(3)The nonlinear time history analysis method is used to compare and analyze the seismic responses of bridges under the two constraint systems.The results show that the damping performance of Bridges in the longitudinal direction is remarkable after adopting the cooperative constraint system,and the damping effect of the longitudinal deformation of the superstructure reaches 18.4%～19.31%.The damping effect of longitudinal deformation and internal force response of the substructure is 29.48%～31.12%,and the damping effect of the substructure is better than that of the superstructure.(4)The impact reaction between bearings at the top of main piers and limit block of bridge under cooperative constraint system has been calculated and analyzed.The result shows that the setting of the longitudinal limit block effectively limits the deformation of the bearings,which in turn ensure that earthquake under the action of bridge pier beam relative displacement reaches a controllable state.It can protect bearing shear damage does not occur under the action of earthquake,also avoid the risk falling beam.The interference of the block makes the structure turn into a cyclic elastic collision under the earthquake,and the collision reaction between the support and the longitudinal block is more obvious on the high piers. |
PDF Full Text Request