| A large number of studies have shown that the pile-soil interaction has a great influence on the dynamic characteristics of the bridge and the seismic response,so its effect cannot be ignored,but how different the calculation results obtained by different pile-soil interaction calculation models are,and some simplified piles are used The calculation error caused by the soil interaction model has not been solved well.Some issues that are important to engineering design are not well resolved.It should also be noted that the pile-soil interaction model not only has an important impact on the seismic response of the full bridge,but also The seismic response of the pile itself has a great influence.Therefore,this paper will focus on these issues,by comparing the calculation results of different pile-soil interaction models,and studying the main differences in the bridge seismic response results caused by the different pile-soil interaction calculation models,and how big it is to provide a reference for engineering seismic design calculations.In addition,the calculation method of damping will also affect the seismic response of the bridge.By comparing the calculation results of different damping calculation methods,the main differences in the seismic response results of the bridge caused by different damping calculation methods are studied.It is designed for the earthquake resistance of the bridge.And safety check.This paper takes the Baisha Town Yangtze River Bridge(200m+520m+200m mixed beam cable-stayed bridge)as the engineering background,establishes its finite element model,and draws the following research conclusions:(1)Due to the structural characteristics of the structure itself,the basic vibration mode of the long-span tower-pier consolidation system is very different from that of the general long-span cable-stayed bridge.Considering the elastic constraints of the foundation,the first-order natural vibration period of the supporting project is obtained.It is 5.67 s,and the basic vibration mode is symmetrical vibration of the main tower transverse bridge.After the tower girder pier is consolidated,the stiffness of the bridge along the bridge is significantly improved,and the natural vibration period along the bridge is also greatly reduced.The first-order natural vibration period along the bridge in this paper is reduced to 2.5s.(2)By changing the constrained stiffness of the foundation to the foundation(completely rigid constraints,elastic constraints of different sizes),the effect of the constrained rigidity of the foundation on the natural vibration period of the long-span tower-pier consolidation cable-stayed bridge was studied.The study found that when the stiffness of the foundation changes within a certain range,the strength of the foundation constraint has little effect on the first-order natural vibration period of the full bridge.For example,the first-order natural vibration period calculated by the rigidity and elastic constraints of the foundation of this bridge is the largest The difference is only 2.4%.(3)For the cable-stayed bridge with tower and beam pier consolidation,the seismic response has the following characteristics: First,due to the consolidation of the main beam and the pier,the seismic force of the main beam along the bridge direction is mainly borne by the two main towers,and the internal force of the main tower There is a large abrupt change at the tower-beam consolidation.Second,due to structural characteristics,the seismic force of the transverse bridge to the main beam is shared by the piers.Third,after the tower girder is consolidated,the displacement of the main beam and the top of the tower under the earthquake is greatly reduced,but due to the weaker rigidity of the upper tower column,the transverse displacement of the top of the tower is larger,which is the point of the seismic design of the bridge.Need special attention.(4)By comparing the seismic response of the full-layer bridge between the layered soil spring model and the concentrated soil spring model,it is found that there are some differences in the impact of the two pile-soil interaction models on the seismic response of the bridge,including: dynamic characteristics,internal force of the main tower,and displacement of the top The two results are in good agreement,and there are certain errors in the internal force of some auxiliary piers and the internal force of the main beam of the side span.Generally speaking,the calculation results of the two models are relatively close,and they can be used in the seismic analysis of actual projects.(5)Using the time-history analysis method,the stress of the pile body is studied.It is found that compared with the two-way seismic input,the three-dimensional seismic input mainly affects the axial force of the pile,so the pile foundation bending moment shear is calculated.Only two-way seismic input can be considered for the force response value;the bridge pile foundation is subjected to the largest part of the pile top under earthquake action,and the internal force is gradually decreasing as the depth of the soil layer increases,and finally returns to 0.(6)The X-TRACT software is used to calculate the bending moment curvature curve of the pile top section.By comparing the yield bending moments of the piles at different positions,it is found that the yield bending moment of the peripheral pile foundation in the group pile foundation is less than that of the inner pile foundation Moment,the difference between the yielding moments of the two can reach 30%,it can be seen that the outer piles in the pile group foundation are easier to yield first under the action of earthquake.(7)By changing the selection range of the soil on the side of the pile,the influence of the quality of the parasitic soil on the seismic response of the bridge was studied.The study found that the quality of the parasitic soil will have an effect on the stress of the bridge pile foundation.As the range of the parasitic soil increases,the stress on the pile body will also increase,but the parasitic soil after the range of more than double the pile diameter(2.8m)The influence of mass on the pile top is gradually weakened.For the bridge superstructure,the influence error of different ranges of seismic soil on the internal force of the bridge superstructure is about 10%.It can be seen that when the seismic analysis of the bridge superstructure is performed,its influence can be ignored for simple considerations.(8)By calculating the seismic response of the project,the difference in seismic response when different damping calculation modes(mode damping,Rayleigh damping,mode damping based on strain energy theory)are compared,the results show that: The seismic response results of bridge components have a relatively large impact.For the internal force and displacement of the main tower pier and the internal force of the main beam span,the three results are relatively consistent,with an error of 10%,but for the internal force of the auxiliary pier and the internal force of the main beam side span,there is a difference between the three,some The result error can reach more than 30%. |
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