Research On Reliability And Residual Life Of Reinforced Concrete Beam Strengthened By Steel Plate

Under the long time effect of natural environment and service environment,the structure resistance decreased and reliability can't meet the standard requirements.At this time,the maintenance and reinforcement are needed.Synthesizing the existing research results,the reliability of the strengthened member was analyzed as a whole.The strengthened reinforced concrete member is compostle member made up existing member and new part.In order to avoid the failure of the strengthened member which is caused by the low reliability of any part,it is particularly important to ensure the reliability coordination of the new and old parts.In this paper,the reliability of old part and new part was calculated respectively about reinforced concrete beam strengthened by steel plate.And reliability of strengthened member was given by adjusting some factors to make the reliability coordination of two parts,which provides guidance for the residual life prediction.The main research works are as follows.(1)The basic theory of engineering structure reliability is narrated detailedly,which contains application of structure reliability,basic conception of structure reliability and common reliability index calculation methods.The design point method and three methods of transforming non-normal variables into normal variables including equivalent normalization method,reflection transformation method and practical analysis method,are introduced emphatically.(2)Based on material properties time-varying model of reinforced concrete and the resistance decrease model of the existing structure,the resistance model of strengthened reinforced concrete member was determined.Load probability model and statistical parameters were analyzed in detail.(3)According to the stress state of the existing member at the time of reinforcement,the reliability of strengthened member was analyzed when steel bar has yielded and not yielded.When the steel bar hasn't yielded at reinforcement moment,according to adjust to degree of unloading and steel plate section,reliability index of old part and new part are coordinated to make them have the same reliability.The influence of steel bar intensity and steel plate intensity on reliability coordination was analyzed.And the stress range of steel plate were given when using different steel bar intensity.The influence of steel plate section in different degree of unloading and failure mode on reliability index was analyzed.Unlike the analysis methord of the unyielded steel bar,when the steel bar has yielded at reinforcement moment,the effect of steel bar was not considered and steel plate was pasted directly.The influence of degree of unloading and steel plate section on reliability index was analyzed emphatically.(4)Residual service life of reinforced concrete beam strengthened by steel plate based on time-dependent reliability index was predicted.The influence of degree of unloading,steel plate section and service environment on residual service life was analyzed in detail.The measures of prolonging residual service life were provided combined practical examples in chloride environment.Finally,the basic thinking about residual service life of structure system was introduced briefly.