Study On Time-dependent Seismic Fragility Analysis Of RC Frame Structures Corroded By Chloride Attack

Research on the mechanical performance degradation of RC structures corroded bychlorideis is one of the most important parts in the durability studies. Corrosion ofreinforcement bars in concrete is directly responsible for serious damage to concretestructures, which may result in premature failure of the structures as a function of time.Therefore, it is necessary to evaluate its damage on the structural performance level.This study contributes to an understanding of the relationship between these two topicsas a function of time to predict the performance level of corroded RC buildings and themain achievements of this dissertation are as follows:(1) In this thesis, the state of the art of the macro beam-column element on RCframes is comprehensively introduced. The emphasis is put on the bar system finiteelement model (FEM). The macro beam-column element in the existing FEM softwareis expatiated. Finally，the plastic phinge element based on the fibre section is choosed tobe used for the following numerical model.(2) In this thesis, the state of the art of the RC material deterioration modelcorroded by chloride is expatiated. The emphasis is put on the theory and methodologyof cracking and spalling in the compressed concrete of compression zone based onmodified compression-field (MCF). The loss of the cross sectional area ofreinforcement bars, reduction of the cover and core concrete strength are modified bythe single-factor corrosion rate. The modified methodology of the compressed concretestrength is progressively improved. The regression formula between the weight loss ofthe stirrup and longitudinal reinforcement corroded by the accelerated electrolchemicalcorrosion methord is given based on the collected experimental dates.(3) Based on the FEM software SeismoStruct, the plastic phinge model based on the fiber section is used to build the numerical model. Three combined parameters (lossof the cross sectional area of reinforcement bars, reduction of the cover and coreconcrete strength) as a consequence of corrosion effects were calculated as a function ofthe corrosion rate for four different time periods (i.e., non-corroded (t=0),5,10and15years). The push-over curves of three-floor, four-floor and eight-floor RC frames aredepicted by the static push-over analysis based on the SeismoStruct. Three-floor andsix-floor RC frames are analysed by the IDA method based on the SeismoStruct. Thetime-dependent fragility curves of four ages corresponding to different performancelevels are depicted by the IDA method.