Study On Static And Dynamic Performance Of Asymmetric Hybrid Girder Cable-Stayed Bridge

The side span of hybrid girder cable-stayed bridge is partially or totally concrete girders,while the middle span of hybrid girder cable-stayed bridge is partially or totally steel girders.The stiffness and dead load ratio of the side span are quite different from those of the middle span.The side span plays a very good role in anchoring and weighting the middle span.The hybrid beam cable-stayed bridge has the advantages of both steel and concrete materials,and has a good balance between structural performance and economy,and has superior advantages in special terrain conditions.Due to the use of two different materials in different sections of the main beam(tower),the structural characteristics of the main girder(tower)are quite different from those of steel tower cable-stayed bridges and concrete tower cable-stayed bridges.In this thesis,a singletower asymmetric hybrid beam hybrid tower cable-stayed bridge is used as the engineering background.The finite element software MIDAS/CIVIL is used to establish a full-bridge spatial finite element model consisting of beams and truss elements to calculate and analyze the static performance of the bridge during construction and the static and dynamic performance of the operation stage.The multi-Ritz vector method is used to calculate the natural vibration characteristics of the bridge considering the pile-soil effect,and the seismic response of the bridge is calculated and analyzed by the response spectrum method.Finally,the finite element software MIDAS/FEA is used to establish the spatial finite element model of the main tower steel-concrete composite section to calculate and analyze the stress distribution of the combined section under the combination of positive bending moment maximum and negative axial force maximum load.In this thesis,the static and dynamic performance of the asymmetric hybrid beam cablestayed bridge is studied.The deformation and stress of the cable-stayed bridge belonging to the background engineering in the construction and operation phases meet the requirements,which proves that the construction method of the bridge is safe and feasible.The upper part of the main tower adopts the form of steel tower to effectively control the unfavorable problem of the section in the middle of the tower and the problem of excessive self-weight caused by using concrete tower alone.A concrete tower is used at the bottom of the main tower to avoid the problem of large structural deformation caused by using steel towers alone.The first frequency of the cable-stayed bridge is 0.68 Hz,and the first mode of vibration is the main tower’s transverse bending,and the cable-stayed bridge has the characteristics of frequency density and vibration mode coupling.The longitudinal displacement of the cable-stayed bridge under earthquake action is small,which is not conducive to the energy consumption of the bridge structure under the action of earthquake.Under the combination of earthquake action and permanent action,the internal force at the bottom of main pier and tower foot isvery large,which should be paid attention to in design.Under the state of ultimate bearing capacity and normal use limit,steel-concrete composite section stress of the main tower meets the strength requirement and the stress level is low.The stress concentration phenomenon exists in the connection parts of each plate to varying degrees.The stress concentration of the bearing plate is prominent near the manhole in the connection position between the web plate and the steel tower,but the stress concentration range is very small.The welding quality between the components should be strictly guaranteed and structural measures should be taken.The research results of this paper have certain reference significance of the design and construction of this kind of bridge.