Wiener Process Identification And Life Prediction For Dynamic Elastic Modulus Degradation Process Of Concrete Under Freeze-Thaw Action

For complex systems,Wiener process modeling based on performance degradation data can predict the life of system considering uncertain factors.However,the lack of discussion on the applicability of the Wiener process led to some unreasonable Wiener process reliability modeling and applications in life prediction.For this reason,this study develops a MATLAB program to analyze the applicability of Wiener modeling by analyzing the properties of increment of the Wiener process and combining the knowledge of probability statistics and hypothesis testing.Taking the concrete dynamic elastic modulus data of laboratory freeze-thaw tests as an example,after analyzing and testing the degradation data,it is concluded that the damage process of the relative dynamic elastic modulus of concrete accords with the properties of the Wiener process with drift coefficient.Then,the parameters of the Wiener process model are estimated to obtain its life probability function curve and reliability curve.The relationship between the rapid freeze-thaw cycle in test and the freeze-thaw cycles in practical structure is established to apply the results of test data to practical structures for life prediction and reliability evaluation.This method provided in this study can avoid the unreasonable application of the Weiner process to the system modeling,and provide a scientific guidance for the maintenance plan and the study of frost resistance durability of concrete structures.The main contents of this study are as follows:(1)Several existing Wiener process model identification methods are introduced in the study.A new method of Wiener process identification is proposed from the respect of the definition and properties of the Wiener process.Based on the statistical analysis of degradation data in different samples,and starting from the properties of Wiener process and the probability statistics,the normality,independence and stability of the increment data are tested one by one to reach a conclusion on whether the data satisfies the properties of the Wiener process.(2)The mechanism and influencing factors of concrete freeze-thaw failure are discussed,and degradation data of the concrete dynamic elastic modulus obtained by the freeze-thaw test was collected for testing the data increment one by one to find out whether accord with the properties of the Wiener process.The results show that the degradation of the relative dynamic elastic modulus of concrete in rapid freeze-thaw tests conforms to the properties of the Wiener process.(3)The Wiener process model is developed by using the maximum likelihood estimation method to estimate the parameters of the Wiener model of the degradation of the relative dynamic elastic modulus of concrete under freeze-thaw cycles.The probability density function and distribution function of the concrete life are obtained,and the structural reliability curves with different failure thresholds are given.(4)The relationship between the freeze-thaw cycle in laboratory and the freeze-thaw cycle in environments is established,then the number of freeze-thaw cycles of a structure can be converted into the equivalent number of freeze-thaw cycle in laboratory,which provides a method to predict the anti-freeze life of concrete structures.