Safety Analysis Of Existing Concrete Structural Members And Study On Construction Safety Of Reinforcement Project

China is in the process of transformation from the second development period to the third development period of the construction industry.The task of identification and reinforcement of existing buildings is very heavy in this process.The detection and evaluation of existing building is the foundation of reinforcement construction,and they are an important part of the existing building safety management system.This study focuses on the safety evaluation of existing structure and the construction safety of reinforcement project.At present,the safety evaluation of existing concrete members(ECM)is mainly carried out by Standard for appraisal of reliability of civil buildings.However,there are some problems in engineering practice,which are reflected in the lack of rationality in the value of partial coefficients,and the influence of durability on the safety of existing members is not considered comprehensively.Moreover,there are few studies on the safety aspects of reinforcement construction alone,so it is difficult to carry out targeted safety management and safety early warning.In view of these problems,this paper determined a set of partial coefficients suitable for the evaluation of the bearing capacity of ECM,and put forward a practical analysis method for the safety evaluation of ECM.In addition,the association rules between the hazard factors were mined out to improve the effiency of construction site management.The main contents are devided into three parts:(1)The partial coefficients suitable for the bearing capacity evaluation of ECM were determined.According to the characteristics of existing structure,the probability models of resistance and load were established.Then,combined with the relevant current standards,the revision of the statistical parameters of resistance was systematically studied,and the statistical parameters of live load corresponding to different target service periods were determined.On this basis,the calculation program was compiled by Visual Basic language,and the optimal partial coefficients in different target service life were determined by JC method.The details were as follows:based on the principle of minimum cumulative relative error,the partial coefficients of loads in different target service life were optimized,and then according to the selected load partial coefficients,the resistance partial coefficients of ECM with the optimal target reliability index were determined.Finally,combined with the bearing capacity checking formula,the checking calculation and evaluation of the bearing capacity of ECM were realized.(2)A practical analysis method for the safety evaluation of ECM was proposed.In this paper,the safety evaluation of ECM was studied through five indicators(bearing capacity,concrete carbonation,corrosion of reinforcement,deformation and cracks).Firstly,the specific quantitative methods of the five indicators were given,and the data of the bearing capacity index was quantified by the probability method.According to the inspection data of the five indicators and the classification standards,the corresponding matter-element models were established.In order to overcome the one sidedness of single weighting method,the IAHP and entropy-weighting method were used to calculate the subjective and objective weights of indicators respectively.And the subjective weights were determined by the current state of ECM and expert experience.In view of the fact that subjective weight vectors are composed of interval number,an improved comprehensive weighting method based on game theory was proposed to solve the problem that the comprehensive weights can not integrate the interval number weights.Then,the comprehensive correlation degrees were obtained by correlation function,and the safety evaluation of ECM was carry out based on extension model.Finally,according to the actual engineering case,the rationality of the evaluation results was tested.(3)A safety early warning analysis method based on association rules mining technology was proposed.Firstly,the hazard factors of the construction site of reinforcement project were classified into four categories,i.e.,"project factors","equipment,facilities and environmental factors","management factors" and "human factors".Secondly,based on these classification details and codes,an Android program was developed to collect daily hidden danger records of construction site by using smart phones,and a hidden danger database was established for the construction site of reinforcement project.Thirdly,the Apriori algorithm was used to mine the frequent itemsets in the hidden danger database,and the Kulc and imbalance ratio(IR)were added to the traditional support-confidence framework to extract association rules.Finally,the extracted association rules were analysed to explore the internal relationship between the hazard factors,and a new analysis method for the safety early warning of reinforcement project construction site was provided based on the concept of safety barrier.Moreover,on the basis of the hidden information contained in the association rules,some practical management suggestions were put forward to promote the realization of the construction safety of reinforcement project.