Research On Seismic Vulnerability Of Upper Arch Column Of Reinforced Concrete Box Arch Bridge

In earthquake disasters,bridges are easily damaged structures in the transportation system,and at the same time,they are also an important part of the transportation system.The degree of damage to the bridge structure is directly related to the assessment of the remaining functional status of the transportation system and the prediction of the loss of the entire transportation system,and the destruction of a certain part of the transportation system directly affects the rescue work of earthquake disasters.Therefore,study the vulnerability of bridges to earthquakes and understand As for the destruction characteristics of bridge structures,it is very necessary to specifically consider the seismic design of the structure from the perspective of structural vulnerability.At present,the theoretical vulnerability curve is the most commonly used to express the seismic vulnerability of the structure,because it can not only express the probability that the structural response of the bridge structure under different seismic conditions exceeds its bearing capacity,but also the result of the seismic vulnerability analysis It’s more intuitive.Large-span deck-type reinforced concrete arch bridges have been widely used in mountainous areas due to their structural advantages.This thesis conducts an in-depth study on the seismic vulnerability of the arch pillars of the vulnerable components of this bridge,so as to carry out seismic fortification,maintenance and reinforcement for possible earthquake damage.Based on engineering examples,a reinforced concrete box arch bridge with a span of 180 m is taken as the research object.Considering that there is little research work on the seismic vulnerability of the arch column,this article mainly studies the seismic vulnerability of the arch column.The main tasks to be completed are as follows:(1)Summarizes the background and significance of the topic selection of the seismic vulnerability of bridge structures,as well as the research process and development status of the field at home and abroad,and summarizes the theories and methods of the seismic vulnerability analysis of bridges.(2)The process of establishing seismic vulnerability curve of bridge structure is introduced;the selection of seismic wave and damage index is discussed.Finally,according to the design response spectrum of the bridge structure,some seismic records that meet the requirements of the specification are selected from the actual seismic records,and the displacement ductility ratio is determined as the damage index.(3)Taking a reinforced concrete box arch bridge on a highway as the research object,the moment-curvature analysis of the section of arch columns directly reflects the ductility capacity of the key section of arch columns.The displacement damage index is calculated based on the curvature ductility data of the control section of the upper arch column.(4)Establish the MIDAS/Civil finite element model of the deck-type reinforced concrete box arch bridge,and analyze the dynamic characteristics;select the ground peak acceleration(PGA)as the ground motion intensity index,input the appropriate seismic wave,and perform the transverse,longitudinal,and Vertical three-dimensional nonlinear dynamic time history analysis,and linear regression of the logarithm of displacement ductility ratio(μ)and ground peak acceleration(PGA).(5)Based on the linear fitting method and numerical simulation method of the direct regression probability demand model,the theoretical vulnerability curve of the column on the arch is established,and the seismic vulnerability of the vertical and horizontal bridges is analyzed and compared.In addition,the shear and bending moment changes of the columns on different arches under the action of earthquakes,as well as the failure characteristics of the arch columns are analyzed.It also discusses the difference of the theoretical fragility curves of different arch-up columns,and analyzes the reasons for the differences.