Seismic Performance Analysis Of Ring-shaped Low-pylon Cable-stayed Bridge In High Intensity Zone

Since the new century,bridge construction has developed rapidly in China.The strength of design and construction of long-span bridges has been constantly improved.There are various types of bridge structures.The use of various special-shaped bridge towers has enriched the appearance of bridge system,and the mechanical performance is different from that of conventional bridges.Liudong Bridge adopts the first domestic reinforced concrete ring pylon,which is quite different from other common pylons.At the same time,large tonnage friction pendulum bearings are installed in the pylon-beam consolidation system for seismic isolation design.The seismic response of the bridge structure in high intensity areas deserves further exploration.This paper makes the following research on the seismic analysis of the ring low-pylon cable-stayed bridge:1.Using Midas Civil software,the calculation models of the East-West main bridge and the central main bridge of Liudong Bridge are established.The main structure,non-linear connection and pile-soil effect of the bridge are reasonably simulated.The adjacent approach bridge span is considered as the boundary condition of the main bridge structure,and the static and dynamic characteristics of the main bridge are analyzed.2.The response spectrum method and time history analysis method are used to analyze the two-dimensional seismic response of the main bridge structure under E1 frequent earthquakes.Considering the longitudinal + vertical and horizontal + vertical input,the response characteristics of the bridge system under different seismic directions are obtained.The trend of the response spectrum method and the time history analysis method is the same,and the numerical value is close.3.The seismic performance analysis of the main bridge structure under E2 rare earthquake is carried out.Considering the seismic input combination direction of transverse + vertical,longitudinal + vertical and three-dimensional earthquakes,the working condition of the isolation bearing is determined by checking the bolts of the bearing.The bending and shear resistance of the ring bridge tower,the two sides of the main pier,the bottom of the pier at the junction,the pile foundation and the deformation capacity of the isolation bearing are emphasized..The results show that the ring tower,main pier and pile foundation are not yielded under the rare earthquake of E2.The main bridge structure is in the elastic stage,and the support meets the needs of deformationand shear force.At the same time,the rationality of seismic isolation design for ring-shaped low-pylon cable-stayed bridges in high intensity region is obtained by studying the stress of main pier and main tower of different pier-beam restraint systems,which shows that the friction pendulum ball bearings have high seismic isolation performance.4.To study the seismic characteristics of ring pylon structure,the influence of different types of pylons on the seismic performance of low-pylon cable-stayed bridges is compared.This paper establishes a comparative model of portal pylon,double-column pylon,elliptical arch pylon and ring pylon,and carries out the static and dynamic characteristics analysis and transverse seismic performance analysis of four types of pylon working conditions.The results show that the self-vibration characteristics of the four groups of models are similar.The pylon structure has little influence on the overall dynamic characteristics of low-tower cable-stayed bridge,the seismic response of ring pylon and elliptical arch pylon is similar,and the internal force at the bottom of the pylon is constant load Obvious.5.In order to study the influence of the pre-stressed steel bundles on the normal working performance and seismic performance of the ring tower,the layout schemes of different pre-stressed ring towers are calculated and analyzed.It is concluded that the setting of prestressing force can improve the overall performance of the ring tower,significantly offset the dead load tension stress at the bottom of the tower,and at the same time,the increase of prestressing force will increase the axial force of the ring tower,enhance the flexural capacity of the section at the bottom of the tower under earthquake,and avoid the generation of tension stress cracks at the bottom of the tower.Generally speaking,the prestressed concrete ring bridge tower shows better overall stiffness and seismic performance.