Study On Cumulative Impact Damage Of Reinforced Concrete Piers Based On Modal

With the development of infrastructure,such as various kinds of large-scale bridges across the river and across the sea,at the same time,the ship also tends to be large-scale,so that the ship collision bridge accident occurs frequently.Different ship impact results in different degree of damage and even fracture of Reinforced concrete pier.Therefore,ship collision force and damage of bridge pier should be considered in the design of bridge pier,so as to ensure the bridge pier body has sufficient anti-impact capability and ensure the safety and reliability of the bridge.There is a widespread phenomenon of bridge pier damage service in practical engineering.How to evaluate the damage of bridge pier and how to accumulate the collision force of ship during impact become a very important problem.At present,a widely accepted and promising method for structural damage identification is an experimental modal analysis method combined with a variety of disciplines.This method has been widely used in the field of fault diagnosis,load identification and dynamic modification in aeronautics,aerospace,precision machine tools and so on.However,the application of this method in pier impact damage is rarely reported.In this paper,the method is applied to identify the impact damage of bridge pier for the first time,and analysis of damage of bridge piers under cumulative impact.The main contents of the study are as follows:1.According to the problems existing in the present research,this paper puts forward the content of further research,designs and manufactures the corresponding test pieces,and designs the test scheme to carry out the horizontal impact test and the modal test.2.This paper introduces the principle of experimental modal analysis,validates the feasibility of modal frequency identification of bridge pier impact damage by traditional ultrasonic nondestructive testing,and through theoretical analysis and experimental contrast analysis,the reliability and accuracy of modal frequencyidentification of pier damage are verified.3.According to the principle of energy conservation,the theoretical calculation formula of ship-bridge collision force during the first collision is deduced.The modified kinetic energy reduction coefficient is obtained by comparing the experimental results with the empirical formulas.Combined with the design code of railway bridges and culverts in China,the calculation formula of collision force without damage is obtained.4.Based on the calculation formula of collision force without damage,the influence of pier damage on the impact force is further considered,and the damage of bridge pier is evaluated by modal frequency representation,then,the formula for calculating the collision force under cumulative impact of ship bridge based on modal damage is proposed.The collision force under the condition of pier damage is analyzed and the applicability and accuracy of the formula are verified by test method and numerical simulation method.5.In order to investigate the influence of different cumulative impact modes on the impact performance of bridge piers,the impact force,strain,displacement,crack and modal damage of reinforced concrete under different working conditions were analyzed.The results show that the cumulative mode of impact energy has great influence on the impact effect of specimens,the mechanical properties of steel bars,concrete and lateral displacement,and the experimental values can reach 17.90%,11.986%,12.594%,12.982%,respectively,the damage of the specimen is also related to the cumulative impact mode,and the width ratio of the main crack can reach 5.2%.6.The damage degree of bridge pier after cumulative impact is analyzed,including crack of specimen,stress-strain of longitudinal reinforcement and modal damage.and the criterion of modal representation of pier damage is given to guide practical application.