Research On Arch Rib Erection Of Long-Span Continuous Rigid Frame Arch Composite Bridge In Mountainous Area And Static Analysis Of The Whole Bridge

Railway is an important national infrastructure,the artery of the national economy and a popular means of transportation.It is the backbone of the comprehensive transportation system and plays an important role in promoting China’s economic and social prosperity.As a new and competitive bridge type,continuous rigid frame beam arch composite system bridge gives full play to the advantages of the two bridges,greatly improves the mid span stiffness of long-span rigid frame bridge,and meets the dynamic requirements of high-speed railway transportation.However,its structure is complex and the construction is cumbersome.Therefore,the stress characteristics of the main components of this kind of bridge in the whole life cycle should be deeply studied.Therefore,taking Shennongxi double track bridge as the engineering background,this paper comprehensively analyzes the change law of mechanical properties of the bridge during construction and operation.Mainly completed the following work and achievements:(1)According to the structural characteristics of the bridge and the geological and environmental conditions of the bridge site,three arch rib erection schemes are proposed,and the economy,technical feasibility,safety and construction period of the three schemes are quantified based on the fuzzy optimization method,and the in-situ assembly scheme of the support suitable for the erection of long-span arch ribs in mountainous areas is optimized;Then,the finite element model under the most unfavorable construction conditions is established,and the safety and stability of the scheme in mountain construction is analyzed and verified,which provides a certain reference value for similar engineering problems.(2)The structure calculation finite element model of the whole bridge is established,the detailed static calculation of the whole bridge is carried out,the deformation,stress and internal force of the main beam,concrete-filled steel tubular arch rib and suspender under different working conditions are analyzed,and the change law of the mechanical characteristics of this type of bridge in the construction and operation stages is clarified,which provides a certain reference value for the study of the mechanical characteristics of this type of bridge.(3)The influence factors of the midspan deflection of the main beam of the through rigid frame arch composite bridge under the long-term performance are analyzed,and the influence law of the arch rib stiffness on the midspan deflection of the main beam of the rigid frame arch composite bridge is obtained,and the functional relationship between the midspan deflection of the main beam and the arch stiffness ratio of the Shennongxi bridge under the ten-year shrinkage and creep is fitted;Then,the preventive and control measures such as setting reasonable camber are proposed to deal with this kind of engineering problems.(4)The safety and stability of the bridge under the main working conditions in the construction stage and the most unfavorable load conditions in the bridge operation stage are analyzed.The instability mode diagram is output and the critical load coefficient is calculated.The influence of the concrete strength of the main beam,pier and arch on the stability coefficient of the bridge in the arch forming and bridge forming stages is clarified.