| With the continuous development of China in the traffic and civil engineering industry,as well as the continuous progress of bridge scientific research,design and construction technology,the span of reinforced concrete arch bridge shows a trend of fast rising,the maximum span of the reinforced concrete arch bridge under construction has reached 600 m.However,in the construction process of long-span reinforced concrete arch bridge,there is a process of forming CFST stiff skeleton first,and pouring the concrete in separate rings and sections.The existence of this construction process may produce the non-planar sectional stress distribution of the main arch rib.Under the premise of large dead weight of long-span arch bridge and high axial compression ratio at the spring,the non-planar sectional stress distribution of main arch rib section may lead to the increase of the stress of CFST and concrete of lower flange,which is very unfavorable to the seismic performance of the structure.At present,none of the studies on the seismic performance of CFST stiff skeleton arch Bridges involves the consideration of the main arch rib concrete casting in ring-casting construction.Based on this research background,the research contents of this paper are as follows:(1)Determination of seismic analysis method for long-span concrete arch bridge.According to the existing finite element simulation methods for long-span concrete arch bridge cannot adapt to seismic dynamic nonlinear time history analysis,a new arch forming simulation method for main arch rib-common joint superposed beam element method is proposed.The finite element simulation method is used to simulate the formation of the main arch rib outer concrete,and the rationality of the method is verified by an actual project.(2)Study on earthquake damage mechanism of long-span concrete arch bridge considering non-planar stress distribution.In this paper,according to the non-planar stress of the main arch rib section of stiffened skeleton arch bridge in the construction stage,the earthquake intensity is divided into three types,and the earthquake damage of the substructure under the earthquake action is mainly investigated.The results show that the damage caused by the longitudinal earthquake mainly lead to the plastic hinge of the column and the yield of steel pipe or steel bar at the spring,while the damage caused by the transverse earthquake mainly lead to the yield of the column and the main arch rib transverse beam,and the collapse of the structure under the transverse earthquake is controlled by the transverse connection.Moreover,the reinforced skeleton concrete arch bridge neglecting the simulation of segmental process will have the risk of ignoring the crack of the lower flange and the yield of the steel pipe and the bottom steel bar in the vary rare earthquake.(3)Study on seismic performance evaluation method of main arch rib of long-span concrete arch bridge considering non-planar stress distribution.In this paper,the ultimate failure state of the main arch rib of long-span concrete arch bridge considering non-planar stress distribution is determined,that is,the ultimate failure state of concrete in the compression area is taken as the ultimate compressive strain,and a new axial force-bending moment envelope curve(N-M curve)is obtained based on this state.It is characterized by the decrease of ultimate bearing capacity,asymmetric distribution of N-M curve and improvement of ductility.The reason lies in the abrupt change of strain between upper flange and web,web and lower flange during the process of concrete pouring,which makes the yield strain of farside steel pipe or steel bar come in advance.If the original axial force-moment envelope curve is used to evaluate the seismic safety of the main arch rib,misjudgment may occur.In view of the decrease of ultimate bearing capacity of the main arch rib,a reinforcement scheme is proposed,that is,the ultimate bearing capacity can be greatly increased by increasing the strength of concrete and steel tube simultaneously. |
