Inferred Method For Flexural Bearing Capacity Of Existing Concrete Members Based On Non-destructive Test

The inference of component resistance is an important part of the existing structural reliability assessment.However,the commonly used indirect inference methods tend to be conservative due to the need to take into account the effects of many uncertainties,which may lead to unnecessary reinforcement measures.Compared with the indirect inference method,the internationally proposed test-based inference method is more accurate,and the inference results can truly reflect the actual resistance of the components.However,the method is based on destructive tests,and can not meet the requirements of continuous use of the components with limited scope of application.Therefore,it is important and necessary to study the method of inferring the resistance of existing structural members based on non-destructive tests to promote the development of reliability assessment methods for existing structures.Firstly,in view of the shortcomings of the existing indirect inference methods,such as insufficient inference accuracy,a resistance standard value inference method based on probability model is proposed.Then,This dissertation focuses on the development of reliability assessment methods for existing structures.With the existing reinforced concrete(reinforced concrete or prestressed reinforced concrete)bending members as objects,the paper studied the probability prediction method of resistance of existing structural member based on non-destructive test and the small sample inference method based on non-destructive test.The main contents are as follows:(1)The inference method of resistance standard value based on probabilistic model.According to the probability model of resistance and the method of statistical inference,the inference method of resistance standard value based on probability model is proposed.The method has a rigorous theoretical basis,not only accords with the general law of statistics,the inferred resistance standard value has a clear probability significance,the inference result is more reasonable,and can be used as a supplement to the existing indirect inference method of component resistance.(2)Stochastic process probabilistic model for bending behavior of existing concrete members.Taking the compressive strain of concrete and the height of section relative to the compressive zone as the basic parameters,the random process probability model of flexural bearing capacity of existing concrete members is established to reveal the probability relationship between the resistance of existing concrete members and the actual stress state of components in non-destructive tests.The results show that the stochastic process probability model of the flexural bearing capacity of existing concrete members proposed in this paper can reasonably reflect the variation of the probability characteristics of the bearing capacity of existing co ncrete members with the basic parameters.(3)The probabilistic prediction method for the flexural capacity of existing concrete member based on non-destructive test.For the case of a single specimen,the probability prediction method of flexural bearing capacity of existing concrete members based on the compressive strain of concrete edge fibers and the relative height of compressive zone of section in non-destructive tests is established.The main parameters affecting the prediction accuracy of probability prediction method are analyzed by experiments,and two prediction methods are discussed.Applicable objects.The results show that the two probabilistic forecasting methods based on non-destructive tests are reasonable and reliable.O n the basis of fully utilizing the loading information of existing concrete members,the forecasting results are closer to the actual value of resistance and have less variability than those based on material properties.Indirect inference method for geometric size test results.(4)The small sample inference methods for bending capacity of existing concrete members based on non-destructive tests.According to the probability prediction method,the prediction results of each specimen are obtained.Based on this,a small sample inference method of member resistance is established for multiple specimens.Taking concrete flexural members as carriers,a small sample inference method of bearing capacity of existing concrete flexural members based on non-destructive tests is proposed.The reasonableness of the inference method is verified by the test loading.Comparied with the inference method under no test.e method without test shows that the inference value of the method in this paper is closer to the inference result under destructive test and is an ideal inference method.The resistance inference method based on non-destructive test established in this paper is a supplement to the existing resistance inference method.This method makes full use of the loading information of components on the basis of non-destructive test,makes up for the shortcomings of direct inference method and indirect inference method,and fills up the resistance under the condition of insufficient test in the world.The inference method,together with the indirect inference method and the inference method based on destructive test,forms the inference method of existing structural member resistance.At the same time,the proposed method expands the application field of structural testing,and provides a more empirical test-assisted method for reliability evaluation of existing structures,so as to ensure the reliability of structures,especially major engineering structures and new structures more effectively.