Influence Of Tie Beam On Transverse Seismic Responses Of Simply Supported Girder Bridge In Urban Rail Transit

The tie beam can provide lateral constraint for the bridge of double column pier.If the tie beam is set as the ductile energy dissipation component,it can use the yield under the earthquake to form the energy dissipation mechanism to protect the main structure of the bridge from earthquake damage.The bridge in urban rail transit,which has its own characteristics in seismic damage forms and seismic requirement,is different from those of the general bridges in the form of structure and the mechanical characteristics.To explore the influence of the tie beam on transversal earthquake responses of simply supported girder bridge in urban rail transit,the railbridge model with and without the tie beam were established by OpenSees software.The main research work is as follows:(1)By consulting abundant documents,the seismic research statuses on tie beam in home and abroad were reviewed,and some new ideas and methods on reducing the transverse seismic damage to the pier were introduced.The simulation methods of tie beam,pier,support,track structure and its subsequent mechanism were elaborated.(2)The influences of the tie beam on the dynamic characteristics of the structure were revealed by the modal analysis of the position,stiffness,the connection between the tie beam and the pier,and the non-beam model.The results show that the tie beam is only affected by the transverse dynamic characteristics of the structure.Compared with the non-beam structure,the increasing range of the natural frequency will be the most.when the tie beam is located in the middle of the bridge.In a certain range,it was proved that the greater the stiffness of the tie beam,the greater of the increasing range of the natural frequency.The natural frequency of pier-beam hinged is not much different from that of the non-beam structure.(3)On the basis of the modal analysis,the influences of tie beam on transversal earthquake responses of simply supported girder bridge in urban rail transit were studied under frequently occurred earthquake,design earthquake and rare earthquake.The results show that the reduction of the horizontal turning angle,the lateral displacement of support,the lateral displacement and bending moment of the pier top,the lateral bending moment of the pier bottom,and the increase of the demand for the shear force of support and the shear force of the pier bottom are the largest,when the tie beam is located in the middle of the pier,the width and height of the tie beam are 0.8D and 1.0D respectively,and the tie beam and the pier are fixed.(4)In the case of rare earthquakes,the structure is in the non-elastic working condition with damage development under some seismic action.Park-Ang damage index DI is used to research the influence of tie beam on structural damage.The results show that the damage index is the greatest degree of reduction when the tie beam is located in the middle of the pier,the width and height are 0.8D and 1.0D respectively,as well as the tie beam and the pier are fixed compared with the nonbeam model.