Seismic Response Characteristics Of Precast Segmental Box-girder Pre-stressed By External Tendons

Externally prestressed segmental box girder bridge can fully demonstrate the factory way of bridge construction,with simplified procedures,shorten the construction time,save material and reliable performance,so it has been more and more widely used in the field of bridge construction.However,there is no complete supporting theory and method in the relevant domestic norms for the kind of bridges,and the relevant research on seismic resistance is very lacking.In order to reveal the seismic response characteristics and seismic performance of these bridges under different intensities and conditions of usage,As well as provide technical reference for the promotion and application in the high intensity area.First of all,this paper chooses externally prestressed segmental box girder bridge as research object,then put forward a high-precision detailed model which can take into account both the computational cost and the design efficiency by comparing and analyzing the traditional modeling method.And the dynamic characteristics and the sensitivity of the bridge are studied based on the research.Secondly,By Seismic Nonlinear Finite Element Analysis Method and considered the multiple nonlinear factors,the variation law and seismic performance of the typical parameters of the bridge structure were studied,and reviewed the analysis results.Thirdly,through the research of the influence of the pulsed effect in the near-field earthquake on the structure,and the IDA curve of the seismic response of the components such as the segmented box girder and the bearings.Which further reveals the seismic response characteristics and failure modes for segmented box girders.Finally,in order to study the stability of retaining walls against lateral overturning for the bridge under earthquake action,this paper has analyzed the problem of lateral overturning stability and its checking method.Then combined the engineering characteristics and the anti-overturning stability problem,carried out the numerical simulation of four kinds of most unfavorable load conditions,and the axial compression and transverse shear deformation of the bearings are discussed in depth.The results showed:(1)By comparing the high-precision detailed model proposed in this paper and the traditional model of the frame system,the two models show a high degree of consistency in the low-order modal of the bridge structure,and the fundamental frequency of the structure is almost the same.The high-precision detailed model is more accurate than the rod model.(2)The effect of effective stress on the seismic response of segmental girders is obvious.When the earthquake is along the horizontal and vertical excitation,the steering block arrangement has little effect on the mid-span deflection.The shear stiffness of different joints has little effect on the joint box girder.(3)The effect of seismic action on the working state of the shear bond at the seams of the joint is very significant.In the longitudinal and vertical earthquake,the joint of the main girder of the segment is closer to the span,and the shear capacity of the shear bond is higher.Under the action of horizontal and vertical earthquake,The tangential shear capacity of the seam is significantly reduced compared to the dead load,so the design should be fully considered.(4)The performance of the shear bond engagement at the joints of the main girder in the longitudinal and vertical directions of the earthquake is generally worse than that of the earthquake in the transverse direction and vertical excitation.The results show that the seismic performance of the segmental box girder meets the requirement under two leveling earthquakes with the requirement of normative formula checking and entity finite element analysis.(5)The characteristics of ground motion have great influence on the working state of the shear bond at joint joints.There is no opening phenomenon in the joints of the box girder joints,but the opening phenomenon may occur in the near-field ground motions,which will further cause the internal force to be redistributed in the section,leading to the crushing of the joints.(6)The near-field ground motions has a significant effect on the shear response of the joints.Under some pulsating effects of near-field earthquakes,the shear response at the seams is significantly higher than that of the designed earthquakes,which may cause the shear bonds at the joints to fail to withstand the shear forces much higher than those of the designed earthquakes and cause the failure at seam.In addition,under the excitation of the near-field ground motions,the local top of the box near the fulcrum will produce significant local tensile stress,and the value of the concrete beyond the tensile strength limit,causing the box roof roof cracking.(7)For the working condition of the box girder joints and bearings,compared with longitudinal and vertical seismic action,under the action of transverse direction and vertical earthquake,when the seismic intensity reaches 0.3 g,the critical state of the tensile stress appears on the bottom of the box girder.In addition,the bearings in the transverse direction and vertical seismic input is more prone to tensile failure situation.