Mechanical Property Analysis For Long-span Segmental Assembling Bridge In City

The precast segmental beam bridge is more competitive than the traditional monolithic cast-in-place beam bridge in terms of construction quality control,construction period,and economic benefits.Recent years in China,the Yiling Yangtze River Bridge,the Zhuhai Qi'ao Bridge and the newly completed main bridge of Zhengzhou West Fourth Ring Road Viaduct across Zhengshang Road are all in such structural forms.Due to the complexity in construction techniques and high requirements for construction equipment,the precast segmental construction technique started late and developed slowly in China.This paper studies and analyzes the mechanical properties of the precast segmental beam bridge.The discussion is based on the research achievements at home and abroad and takes the main bridge of Zhengzhou West Fourth Ring Road Viaduct as the engineering background.This paper used the finite element software MIDAS/Civil to establish a finite element model of the whole precast segmental beam bridge in colloidal-size and calculated the static and dynamic performance of the bridge.The sub-space iteration method and the response spectrum method are used to calculate and analyze the natural vibration characteristics and seismic responses of the bridge.According to practical engineering,different prestress loss conditions are considered,and the corresponding impacts on the bridge are calculated and analyzed.Then following the joint failure features,and taking the principle tensile stress reaching the ultimate tensile strength as the failure condition,a recommended calculation formula of joint shear capacity is derived considering the joint strength reduction and other factors.Through ABAQUS,the joint crack propagation process is simulated.The stress condition of the joint between epoxy resin adhesives and concrete surfaces is analyzed under different bonding conditions.After the stress analysis of the segmental beam bridge,it is concluded that under the engineering background in this paper,the bridge is of reasonable load under different load combinations and meets the specifications.Measured values of fundamental frequencies of the dynamic loading test are in good agreement with theoretical values.The overall flexural rigidity of the main bridge is in line with theoretical expectations,and the impact coefficient test value of each working condition is less than the theoretical value,indicating that the driving dynamic performance of the bridge is good.Prestress losses caused by duct deviations at the top,web,and bottom plates are all relatively large,among which influence weights of the top and web plates are larger than the bottom plate.Under the engineering background in this paper,the prestress loss caused by the joint compression accounts for 4.27% of the tensile control stress.Therefore,more attention should be paid to joint compression impacts in practical engineering.In the construction stage,the segmental beam deflection under the maximum cantilever state,its sensitivity to the web prestressed steel stress loss is less than the top prestressed steel stress loss.In the operation stage,the vertical prestress loss of top slab tendons has a greater impact on the mid-span deflection.When the bridge completion time is the same,the change rate of mid-span deflection caused by the prestress loss of the top plate is faster than that caused by the prestress loss of the bottom plate.The proposed formula and the AASHTO formula are compared with measured values,and results show that the proposed formula and measured values have a good agreement.Under different bonding conditions,stress concentration occurs around the colloid failure position.The concrete beside the joint also undergoes different degrees of plastic strain,which adversely affects the stress of the joint.