Numerical Simulation Of Deterioration Of Corroded RC Columns Considering Buckling Effect

As the most important part of the durability of reinforced concrete structures,reinforcement corrosion has been widely concerned by scholars at home and abroad.As an important load-bearing component in the RC column,after the reinforcements are corroded,the cross-sectional area decreases and the equivalent strength decreases,which directly affects the mechanical properties of the RC column.However,the corrosion of reinforcements in actual engineering is often complicated and uneven,and the strength degradation process of corroded RC columns contains various complex nonlinear mechanisms.It is difficult to accurately reflect the true performance of the structure just to reduce the strength of the reinforcements based on the corrosion rate.Other factors related to corrosion may also have an indirect but not negligible impact on the mechanical properties of the RC column,for example,decreasing in strength of confined concrete caused by stirrup corrosion,the uneven corrosion of reinforcements,and the premature buckling of longitudinal bars due to the reduction of the cross-section.However,in the existing numerical model studies of corroded RC columns,the uneven corrosion and buckling of longitudinal bars are rarely considered.In order to accurately evaluation the performance degradation of corroded RC frame columns,this paper separately studied the influence of the uneven corrosion of steel bars and the buckling effect of corroded longitudinal bars on the performance of RC columns,and established a set of numerical simulation methods for corroded RC frame columns.Including the calculation model of reinforcements corrosion rate based on the width of corrosion cracks,the constitutive model of corroded longitudinal bars that considers uneven corrosion and buckling effects,and the constitutive model of confined concrete that can consider the corrosion of stirrups and the buckling effects of longitudinal bars.The proposed material model and the overall model of the RC column were compared and verified respectively.The main research work and results are as follows:(1): The laws of corrosion crack propagation and the distribution of corrosion products are studied.And the evaluation model of the corrosion rate of the longitudinal reinforcement based on the corrosion crack width was established.(2): By introducing the corrosion influence coefficient,an equivalent strength model of the corroded longitudinal reinforcement considering the non-uniform corrosion is proposed.Based on the existing test results,the relationship of corrosion rate between longitudinal reinforcement and stirrup was analyzed,and the correlation model of the corrosion rate of stirrup and longitudinal reinforcement was established.Considering the influence of the corroded stirrups on the buckling of the longitudinal reinforcement and the restraining effect of the concrete cover on the buckling of the longitudinal reinforcement,a constitutive model of the corroded longitudinal reinforcement considering the buckling effect is further proposed.(3): The interaction law between buckling longitudinal reinforcement and confined concrete was studied.Based on Mander confined concrete model,a concrete model confined by corroded stirrups was established.The calculation results of the model show that the strength of the stirrups is reduced after corrosion,and the decrease of the lateral restraint capacity of the stirrups on the concrete is the main reason for the decrease of the peak strength of the confined concrete.As the longitudinal bars undergo obvious lateral displacement after buckling and separate from the concrete,the confined state of the concrete has changed significantly.The Mander model cannot accurately predict the strength of the confined concrete after the longitudinal bars are buckled.(4): Based on OpenSees and the proposed material model,a numerical model of the corroded RC frame column is established.Based on the existing test data,the sub-models proposed in this study and the numerical model of the corroded RC column are verified.The results show that the model has good accuracy,the evaluation model of corrosion rate can reflect the influence of involving factors,and the research results can be used to evaluate the performance of existing concrete structures.