| The mechanical characteristics of the special-style beam-arch composite bridge are very special through the special-style structural members such as arch beam and suspender.The mechanical characteristics of the whole structure and structural members are not easy to grasp,and the mechanical laws of different types of structures cannot be directly used for reference.The static characteristics of the structure,the natural vibration characteristics of the structure as an important parameter and index of the bridge design and structural dynamics,and the stability performance of the arch structure are the main concerns of the design and construction of the special-style beam-arch composite system bridge.The main bridge of Shahe Bridge,Mudanjiang Road,Luohe new area is a composite system of special-shaped steel arch rib PC beam and arch.The arch axis is spliced by multiple elliptic curves to form a special-style structure of steel box arch rib space intersection and intersection,with novel shape and bright appearance.However,the special shape of the arch rib makes the structure have obvious characteristics of spatial stress system,and the mechanical behavior of the structure is quite different from that of the conventional beam-arch composite system bridge.In view of this,taking Shahe Bridge as the engineering background,this paper uses the finite element software Midas/Civil to establish the finite element model of the main bridge structure.The static,dynamic characteristics and stability of the bridge structure are analyzed.Based on the original design,the influence of structural parameters on the static,dynamic characteristics and stability of the bridge are studied.The main research contents and conclusions are as follows.(1)The structural characteristics of the beam-arch composite bridge and the specialstyle beam-arch composite bridge are summarized.Then research status of the mechanical characteristics of the beam arch composite bridge at home and abroad are summarized.On this basis,the research content and methods of this paper is defined.(2)Based on the main bridge project of Shahe Bridge,according to characteristics of the structural design,the finite element analysis model of spatial beam element of main bridge is established by the finite element software Midas/Civil.Considering the support construction of the main bridgeccording to the characteristics of the stress and deformation of the main bridge,structure is analyzed in the stage of one-step falling frame.According to the specifications,the structural state of the bridge is checked On the basis of the beam arch stiffness ratio and bending moment sharing ratio,the structural system is defined and analyzed..The result shows that the structure belongs to the rigid beam rigid arch system,and the beam arch bending moment distribution is related to the stiffness matching of the beam and arch,the deformation and stress of the main components of the structure meet the requirements of the code.(3)Combining with the deformation characteristics and of the stress under the onestep finished state of the bridge,the main static characteristics of the structure is analyzed according to the static mechanical characteristics of the bridge,such as thickness of the long arch steel plate,rigidity of the long arch steel arch rib,rigidity of vertical arch steel arch rib,tension of the suspenderand the self weight of the main beam.The results show that the static mechanical properties of the bridge are sensitive in addition to the rigidity of the steel arch rib.To take advantage of arch rib compression and reduce the deflection of the beam arch,the arch rib axial force can have increased through increasing properly the thickness of the long arch steel plate.(4)In order to further understand the mechanical characteristics of the structure,based on the analysis of the static characteristics of the structure,the dynamic characteristics of the special-style steel arch rib beam-arch composite bridge is analyzed.Taking the natural vibration characteristics as the structural dynamic characteristics analysis index,the parameter sensitivity of the natural vibration characteristics of the structure is studied through the structural parameters such as the thickness of the long arch steel plate,the rigidity of the beam arch,the setting of transverse brace.The results show that the main vibration mode of the structure is longitudinal drift of the main beam and anti symmetric vertical bending of the beam arch.The plane stiffness is greater than the in-plane stiffness,and the lateral stiffness of the PC main beam is larger.So the overall vibration mode of the composite structure and ordinary beam structural vibrations are similar.The in-plane vibration frequency is mainly related to the stiffness of the main beam.The thickness of the long arch steel plate and its stiffness change have a greater impact on the out-of-plane vibration for the main arch and the transverse brace.(5)According to the linear elastic buckling theory of the structure,the stability of the beam-arch composite structure is analyzed by the Midas/Civil spatial beam element model of the bridge.Considering the dead weight of the structure,the tension of the suspender,the prestress and the second stage dead load,the stability safety factor and the instability mode of the original structure are calculated.On the basis,the influence of these parameters on the structural stability are discussed through the structural parameters,such as the thickness of long arch steel plate,the rigidity of long arch steel arch rib and the setting of transverse brace.The results show that the overall stability performance of the structure meets the requirements of the code.The first-order instability mode is anti-symmetric lateral instability outside the arch ribt.The stiffness of the long arch steel arch rib is the most sensitive of the structural stability parameters.The safety factor of the structural stability is significantly improved with the stiffness of the long arch steel arch rib increasing. |
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