Study On Dynamic Performance And Seismic Performance Of Through Arch Bridge With Single Skew Arch Rib

The research object of this paper is the monolithic arch rib.In order to enhance the integrity and the out-of-plane stability of the arch bridge,the steel box arch rib is not only consolidated with the bearing platform at the arch foot but also connected with the main beam by slings in the middle to form an asymmetric special-shaped arch bridge structure system.Different from the conventional skew special-shaped arch bridge,the main beam intersects the arch axis plane obliquely,and the arch axis of the arch bridge is in the form of straight curve coupling.The unique structural form makes the structural stress situation complicated,and the transmission path is not clear under the earthquakes,so it is of great significance to analyze the dynamic response of such unconventional arch bridge systems.Through computational analysis,the dynamic characteristics of such unconventional arch bridge systems and the dynamic response of the structure under seismic excitation can be obtained,and the weak parts of the structure can be identified,which can provide a certain reference for the design and construction process of bridges of such systems.The main research contents are as follows:(1)Based on Midas/Civil software,the natural vibration characteristics of the bridge are calculated,and the effects of different factors such as pile-soil interaction and inclination Angle of a straight segment on the natural vibration characteristics of the structure are analyzed.The fundamental frequency of the structure is 0.859 Hz,and the first mode is characterized by transverse bending of the main arch,indicating that the out-of-plane stiffness of the structure is small,which should be paid attention to in the design.With the increase of mode order,the structure vibration shape gradually becomes complicated.When pile-soil interaction is considered,the fundamental frequency of the structure decreases slightly,and the flexibility of the structure increases.When the Angle of one side is fixed and the Angle of the other side increases,the fundamental frequency decreases monotonically.The second natural frequency increases first and then decreases;The change becomes complicated from the third-order natural frequency.(2)Conduct response spectrum seismic analysis on the bridge structure.The seismic responses of bridge structures under one-dimensional seismic excitation(transverse,longitudinal,vertical)and combined modes are analyzed.The results show that there are different degrees of internal force and displacement response in all directions of the structure under one-dimensional seismic excitation.The structural displacement response under transverse seismic excitation is significant.The internal force response of the structure under vertical seismic excitation is large,which cannot be ignored in seismic design.The dynamic response of the structure under three-dimensional seismic excitation is greater than that under single one-dimensional seismic excitation.Due to the randomness of seismic action,structural response under three-dimensional seismic excitation has important reference significance.The maximum internal force response of the structure is located in the arch foot section and the maximum displacement response is located in the 1/4 section of the main arch under onedimensional or three-dimensional earthquake excitation.These sections are the weak parts of the structure and should be paid attention to in the design.(3)By using time history analysis method,the internal force and displacement dynamic response of each control section under the action of different seismic waves alone and combined are compared and analyzed.The dynamic response trend obtained by the time history analysis method agree with that obtained by the reaction spectrum method.The bridge has good seismic performance under the action of the E2 earthquake.(4)The welding quality of steel box arch segments can not be guaranteed at the construction site,and the residual stress may affect the dynamic performance of the structure under the earthquake action.Therefore,welding simulation is carried out to obtain welding residual stress field and plastic deformation of the structure.Based on this as the initial condition,the corresponding hysteresis curve is obtained by repeated loads on the steel box arch segment,and the influence of residual stress and deformation on the energy consumption capacity of the steel box arch is studied.The analysis shows that stiffening ribs limit the local deformation of the steel box arch,which in turn affects the distribution of residual stress near the stiffeners.The maximum equivalent residual stress of the overall model reaches 394 MPa,which is slightly greater than the elastic limit of the steel and will produce residual deformation.After entering the plastic section,the residual stress and deformation have a significant impact on the stiffness and energy consumption capacity of the plastic section of the steel box arch.In summary,after the dynamic analysis and study of the structure,we have a clearer understanding of the dynamic performance of the weak parts of such unconventional arch bridge systems and compare the advantages and disadvantages of different dynamic response analysis methods in practical engineering,which can provide a certain reference for the design and construction of the special-shaped arch bridge in the future.