Research On Mechanical Behaviors Of Integral Abutment Curved Bridge

Curved beam Bridges are widely used in bridge construction because of their graceful lines,smooth lines and easy to arrange.However,the load-bearing characteristics of curved beam Bridges are complex,and they are subjected to large torque in addition to bending moment and shear force.Therefore,traditional curved girder Bridges are prone to girder falling,side turning,warping deformation,girder climbing,support shear failure and other diseases.The appearance of integral bridge provides a new idea for the construction of curved beam bridge.The integral bridge eliminates the support and expansion joints at the end of the main beam and consolidates with the abutment,thus improving the overall stability of the bridge.However,the construction of integral bridge is mainly based on straight bridge,and the research on integral bridge is mainly carried out around the straight bridge,and the research on curved integral bridge is less.The curved beam bridge itself has complex mechanical characteristics.The interaction between soil and structure should be considered for the whole bridge,which makes the mechanical characteristics of the curved beam bridge more complex.There are few design methods and theories that can be used for reference,which are unfavorable to the construction and design of the curved integral bridge.Therefore,it is necessary to make a detailed stress analysis of the curved integral bridge,so as to provide reference for engineering construction and design.In order to study the mechanical characteristics of a curved girder bridge with an integral abutment,the finite element model of the original bridge and the designed integral bridge is established based on an actual curved girder bridge project.Contrast and analyze the difference of stress between the two under the action of four kinds of temperature,the action of the second type of automobile load and the action of automobile centrifugal force,and compare the difference of internal force and deformation of the main girder of the traditional curved girder bridge and the integral curved girder bridge under various load conditions.Then,the time-varying effect analysis is carried out for the integral abutment curved girder bridge alone,and the influence analysis of the deck slab on the time-varying behavior of the main girder of the integral bridge is discussed.The modal analysis,response spectrum analysis and time history analysis of the integrated abutment curved girder bridge are carried out in order to obtain the performance of the integrated abutment curved girder bridge in earthquake resistance.Finally,parameters such as radius of curvature,length of pile foundation,diameter of pile foundation,abutment height and soil type around pile are selected to discuss the influence degree of stiffness and flexibility of the lower part of the whole bridge on the internal force and deformation of the main girder of the superstructure.The main research results of this paper are as follows:(1)As the main girder of the curved bridge is consolidated with the abutment,under the action of dead load and temperature,a larger negative bending moment is generated at the end of the beam,which makes the bending moment distribution of the whole bridge more uniform.Among them,the system temperature rise of 25℃ is an important factor affecting the force of the whole bridge.Under the condition of rising temperature,the whole bridge end shows the upper tension,and the bending moment variation amplitude is large,the bending moment of the side span decreases sharply,and the bending resistance decreases.In the actual design process,the weak design of the mid-span part should be strengthened.At the same time,the torsional resistance of the whole curved bridge has been greatly improved when it intersects the original bridge.(2)Under the action of temperature load,after the integration of the original bridge,the reaction force of the inner support increases,and is all greater than that of the original bridge;At the same time,the reaction difference between the inner and outer supports is smaller,the structure is more stable,and it is not easy to roll over.The automobile centrifugal force is an important factor affecting the stress of the curved girder bridge.After the integration of the original bridge,the reaction force difference between the inner and outer bearings decreases by 65.7%,and the structural stability is significantly improved.At the same time,the curved integral bridge can effectively reduce the radial creep of the main girder,and the maximum reduction value can reach 60%.(3)In addition to the temperature effect,the shrinkage and creep effect is also an important factor affecting the stress of the main girder of the whole bridge.Considering that the decks constructed at different time nodes have a great influence on the shrinkage and creep of the main girder.The earlier the construction time,the greater the stress of the main girder at the pier.The later the construction time,the smaller the stress of the main girder at the pier and the smaller the stress concentration area.The shrinkage and creep effect of bridge decks has a positive effect on the shrinkage and creep effect of main girder of seamless bridge.The reasonable selection of bridge decks can improve the shrinkage and creep effect of main girder.(4)After the integration of the traditional curved girder bridge,the seismic response of the bridge is reduced as a whole,the longitudinal and transverse offsets of the beam end are reduced by more than 80%,and the longitudinal and transverse offsets of the pier top are reduced by nearly 50%.In the time-history analysis,under the action of near-field waves and far field waves,the acceleration response time of the integral bridge end or pier top is all later than that of the original bridge,which indicates that the integral bridge has more advantages in the area of high seismic incidence and can more effectively prevent the occurrence of main girder deviation and girder fall.(5)Radius of curvature and soil type around piles are important parameters that affect the overall stress of the bridge.The radius of curvature has a great influence on the radial displacement of the main girder and the stress of the pile foundation.The larger the radius of curvature is,the smaller the overall torsion effect of the main girder will be.In the process of the radius of curvature from R=90m to R=180m,the stress in the pile foundation concentration area decreases by 26.32%.The denser the soil around the pile,the smaller the radial displacement of the girder.