Study On Seismic Response Of Simply Supported To Continuous High Pier Beam Bridge In Mountain Area

In this paper,a simple supported variable continuous beam bridge in the Lincang Mountain Expressway in Yunnan is used as a supporting project.The bridge is a 7*40m simply supported continuous beam bridge,which is divided into two sections.The pier height is very different,with typical mountain bridge characteristics,and the highest pier is nearly 80m.In this paper,Midas software is used to establish the finite element model of supporting engineering,and numerical simulation method is used to study the seismic response of simply supported to continuous high pier bridge in mountainous area.The main research contents and conclusions are as follows:(1)Combined with the characteristics of the supporting project,two piers of one joint(one is the junction pier between two units,with longitudinal movable support at the top of the pier,and the other is the intermediate pier of the first unit,with pier beam consolidated)are selected.By changing the height of the pier body and the cross-section form of the pier,the influence of the relevant design parameters on the dynamic characteristics of the simple supported to continuous bridge is studied and analyzed.It is found that the influence of the shape of pier body section and the height of pier on the change of natural vibration period is also different.The growth of thin-walled hollow pier is more stable,and its previous periodic growth curves all show a relatively smooth upward curve,while the solid pier is more sensitive to the change of pier height,and its natural vibration period is unstable and faster with the increase of pier height.(2)Through dynamic time history analysis,three seismic waves are selected to study the seismic response characteristics of simply supported to continuous girder bridges in mountainous areas,and the influence of changes in pier body parameters and pier beam connection mode on the seismic response of high pier continuous girder bridges is analyzed.It is found that the pier height of bridges in mountainous areas is very different,and the distribution of seismic force of main beams among piers is also very different.The span of simply supported continuous girder bridge is generally small,and the seismic force of the pier not only includes the seismic force of the upper structure,but also the seismic force of the high pier itself can not be ignored.It is necessary to select the appropriate pier height and section form with more practical conditions in seismic design.The change of the connection form of pier and beam has limited influence on the internal force response of the structure under the action of earthquake,but has a great influence on the distribution of the earthquake force along the bridge.Compared with that,the pier and beam consolidation system is more suitable for the bridge in the mountainous area,which can play a better role in controlling the displacement of the structure and increasing the seismic performance and safety performance of the structure.(3)In view of the possible P-△ effect of high piers,the influence of P-△effect on seismic response is analyzed with equivalent geometric stiffness method and member reduction stiffness method.It is found that the second-order dynamic effect does not necessarily bring bad results,and there is a huge number of influence factors..Taking all the factors into consideration as possible,such as the additional bending moment,equivalent horizontal force,structural stiffness and earthquake input energy,the result is a relatively discrete law.