Pier Damage Assessment And Traffic Capacity Analysis Of Medium And Small Span Bridges After Earthquake

During the 13th Five-Year Plan period,China’s transportation industry has made great progress.The 2030 planning goal of"eight vertical and eight horizontal"proposes that the future highway mileage will reach 45000km.With the continuous extension of the line to mountainous areas and coastal areas,more and more bridges are needed and the span is larger,and the environment will be worse.Some data show that more than half of the areas where the bridges are located are in the seismic zone,and the safety problem of bridges under the seismic action is more and more prominent.Therefore,ensuring the safety of bridge system under the seismic action and ensuring the bridge capacity after the earthquake is a major demand for the sustainable development of China’s transportation.Due to the large amount and wide range of small and medium span bridges,artificial detection method is still mainly used to evaluate the safety of bridges after earthquake disaster.However,the practice has proved that only relying on artificial detection will lead to the lag of bridge information acquisition due to long detection cycle,and the detection situation is difficult to quantify.As a result,the relevant personnel can not quickly and accurately understand the operation of the bridge.At the same time,after the earthquake disaster,some bridges will be completely damaged and lose their capacity,but most bridges will only be damaged to varying degrees,leading to the decline of their service performance.When a major natural disaster occurs,the rapid judgment and early warning of the service performance of the bridge can provide basic data for the selection and optimization of the transportation path of rescue materials and rescue equipment,and provide guarantee for the construction of disaster rescue lifeline.Vibration monitoring is convenient and fast,which is conducive to the rapid evaluation of bridge state and health detection after earthquake.Therefore,it is of great significance to study the evolution mechanism of bridge damage and service performance after earthquake and form the rapid evaluation technology of bridge after earthquake damage for the large medium and small span reinforced concrete bridges,which can provide technical support for the implementation of rapid rescue after disaster.Based on the science and technology development program of Jilin Province"Research on early warning technology of bridge service performance against severe natural disasters(earthquake and flood)in seasonal frozen area",this paper analyzes the failure mode and service performance disaster evolution mechanism of bridges under earthquake natural disasters,and determines the characterization parameters of bridge service performance under earthquake natural disasters,and the rapid damage assessment technology of bridge structure after earthquake is formed based on the numerical simulation method.(1)The typical bridge form is determined according to the classification of span,pier height,substructure form,support type and foundation geometry size.The damage mechanism of typical bridge piers under earthquake disaster is analyzed,and the damage phenomenon and damage process of bridge piers are sorted out;In order to carry out modal analysis of the damaged bridge pier after earthquake,the conventional axial force acting on the top of the bridge pier is replaced by the loading mass.The numerical simulation research is carried out,and the correctness of the theoretical analysis model of anti earthquake disaster is verified by the experimental data based on the understanding of the seismic damage mechanism of the bridge pier(2)By means of finite element numerical analysis and based on the analysis results of hysteretic curve,the influence degree of bridge structure design parameters such as axial compression ratio,shear span ratio,reinforcement ratio and stirrup ratio on bridge pier damage in earthquake disaster is explored,and the corresponding formula is obtained by regression fitting,and then the damage index and characterization parameters of typical bridge pier structure in earthquake disaster are analyzed and summarized.In the numerical simulation,adjusting the maximum horizontal control displacement in hysteretic analysis is used to simulate the seismic damage of bridge piers in different intensity.Combined with Latin hypercube sampling(LHS)to sample the distribution of model parameters,the empirical formulas of residual displacement angle RDA_p and frequency reduction factor RCF are established,Then a frequency based method for calculating the residual displacement of bridge piers after earthquake is formed,which can determine the residual displacement and deformation of bridge piers safely and conveniently.(3)Each damage component is quantified,and the corresponding damage state evaluation criteria are defined;The appropriate seismic damage model is established and the corresponding damage index is obtained.The relationship between the damage index and the residual displacement is analyzed;On this basis,the approximate relationship between normalized residual displacement and damage index is established by nonlinear fitting.Combined with the damage evaluation standard,a simple method to evaluate the damage degree of bridge piers under earthquake disaster is formed.The relationship between the frequency of bridge piers and the maximum weight of bridge after earthquake is established,and the evaluation strategy of bridge capacity after earthquake is formed,After the natural frequency of piers is measured after the earthquake,the maximum capacity of small and medium span bridges can be calculated,which lays a foundation for the early warning of service performance of bridges after the earthquake through the monitoring data of characterization parameters.