Seismic Vulnerability Analysis Of The Long-span Deck Type Reinforced Concrete Arch Bridge

The long-span deck type RC arch bridge is one of the widely used bridge types for the development of bridge with a larger span and softer structure.Compared with small-span bridges such as beam bridges,the arch bridge owns more complicated earthquake damage modes.This paper focuses on the analysis of the seismic vulnerability of the long-span deck type RC arch bridge and analyzes the following aspects.(1)Firstly,the paper proposes the seismic damage index and evaluation method of the arch ring and the upper column.Under the action of the transverse bridge to the earthquake,the force-displacement curve of the plastic hinge of the arch ring section is used as the basis for the evaluation of the damage state of the arch ring,and the"reference displacement" at the center of the dome is used as the damage index corresponding to the deformation of the plastic hinge.Based on the evaluation method of the displacement index of the pier and column of the beam bridge,the evaluation method of the displacement ductility ratio of the upper column of the arch is used to evaluate the damage state of the upper column of the arch.(2)Based on the theoretical vulnerability analysis method,according to the seismic failure mode of the long-span deck-type arch bridge,the vulnerability analysis process of the long-span up-supported reinforced concrete arch bridge is proposed.The arch bridge model is established by finite element software SAP2000 to analyze the earthquake time-history response.The seismic response is linearly fitted to obtain the regression function,and the failure probability formula is substituted to calculate the vulnerability curve of the load-bearing members(the main arch ring and the arch upper column).Furthermore,by adjusting the rise-span ratio of the arch and the arrangement of the upper columns,the effects of geometrical parameters and structural forms of arch bridges on the vulnerability are analyzed.The results show that there are significant differences between the different rise-span ratio of the main arch ring.The upper column of the mid-arch is the most vulnerable,and the columns at both ends are the strongest.Considering the correlation between different components,the first-order boundary method and the second-order boundary method are used to calculate the failure probability of the whole bridge system to form the vulnerability curve.The results show that the system vulnerability is stronger than the vulnerability of each component,and the effect of the rise-span ratio is obvious.(3)Considering the influence of traveling wave effect on the long-span structure,the structural failure mode analysis and failure probability calculation of the longitudinal bridge to the earthquake for the long-span up-supported arch bridge are carried out.1)When calculating the influence of the relative horizontal displacement of the arch foot on the internal force and deformation of the main arch ring,the results show that relatively far off arch foot is unfavorable to both the force and deformation.Taking the bending moment-axial force bearing capacity curve of the arch circle section as the limit state of the performance of the arch ring,the relative displacement of the maximum allowable arch is calculated.Calculating the relative maximum allowable displacement of the arch foot of different rise-span ratio,the results show that the displacement decreases with the smaller the span ratio.2)The maximum allowable relative horizontal displacement of the arch is used to quantify the limit state of the bearing capacity of the arch ring.Choosing the seismic wave shear velocity to simulate the site conditions,and using the relative displacement of the arch under non-uniform excitation as the seismic response index to calculate the seismic failure probability of arch ring longitudinal bridge,then getting the failure probability curve of the main arch ring of the longitudinal bridge.The parameters of the main arch rise-span ratio are adjusted,and the influence of the geometrical characteristics of the arch axis on the failure probability of the longitudinal bridge to the main arch ring is analyzed.The results show that the sagittal span ratio becomes smaller and the vulnerability is enhanced.The parameters of the main arch ring span ratio are adjusted,and the influence of the geometrical characteristics of the arch axis on the failure probability of the longitudinal bridge to the main arch ring is analyzed.The results show that the vulnerability is enhanced when the rise-span ratio becomes smaller.