عنوان مقاله [English]
This paper considers the time-dependent environmental parameters that may change during the lifetime of serving structures and which can play an effective role in primary design criteria or in evaluation of seismic performance in structural members. There is less attention paid to these parameters and their effective factors in current codes. The corrosion of steel due to chloride ions (at propagation state) in RC structures is a dominant factor in changing some structural characteristics and reducing the service life of structures.The purpose of this paper is to develop a modified model to determine bond degradation between steel and concrete and to evaluate the residual flexural capacity of RC beams after the beginning of corrosion caused by chloride ions. Therefore, by analyzing critical parameters in equations proposed by other researchers, a model that considers the effect of rebars confinement is enhanced. Finally, comparison between the results of the modified model and the primary model with the results achieved from a corrosion experiment proved the better precision of the modified model. The importance of progressive variations during the life cycle of members is illustrated with an example about the effects of gradual bond degradation between steel and concrete in various time sections of the life cycle of a RC beam, in order to calculate its residual flexural capacity (in accordance with the Persian Gulf condition).