Research On Detection Method Of Steel Bar Corrosion In Reinforced Concrete Beam Based On Fiber Bragg Grating Sensing Principle

Corrosion of steel bars inside reinforced concrete structures is an important cause of structural durability.As internal corrosion occurs,the overall structural load capacity will be reduced and the reliability will be greatly reduced.It is often unclear due to the degree of corrosion of steel bars.Demolition or accumulation of large amounts of material creates unnecessary cost increases and waste of resources.In the life cycle of reinforced concrete structures,if there is a real-time detection of the degree of corrosion of reinforced concrete structures,it has considerable practical significance.In this paper,the RC beam detection method is studied for FBG sensors,and the mechanical bearing capacity of RC beams with no rust and different degrees of corrosion is simulated and predicted.This article mainly does the following work:(1)In the first chapter,the introduction part integrates the previous researches at home and abroad,expounds the huge loss of reinforced concrete structure due to rust and the necessity of researching it at present,and then explains the cause of rust from the aspects of chloride ion erosion and concrete carbonization.The current analytical results of the mechanical properties of corroded steel bars are given.The progress and some characteristics of reinforced concrete structure simulation are expounded,and the research progress of FBG structure is introduced.Finally,the research process and main aspects of this paper are expounded.(2)In the second chapter,by studying a large number of scientific research results,the structure of the FBG sensor is first decomposed,and the detection principle of the fiber grating is analyzed from the calculation formula and the principle of optical refraction.According to the well-known mechanical loading test,the pre-embedded steel bars and The concrete structure of the FBG strain sensor was loaded,and the corresponding changes of time and load,displacement and load under the mechanical loading test of the RC beam were collected,and the efficiency and accuracy of the FBG strain sensor were verified.(3)The third chapter first describes the numerical analysis of the classic methods,the finite element method,finite difference method,finite volume method of advantages and disadvantages for the methods of three kinds of point of cognition,and then,according to the theory of nonlinear yield,the characteristics of flow and strengthen the phenomenon and the geometric nonlinearity,material nonlinearity of two difference makes a deep study of nonlinear theory,this paper and applied in the numerical simulation to the unit,meshing,the respect such as convergence set problem has made the detailed analysis.(4)Chapter 4 firstly introduced the process of building RC beam in ANSYS,including material properties,grid division and boundary conditions,etc.,and conducted simulation for RC beam in the test part of chapter 2,simulated the experimental loading process,and obtained the curve of fiber strain changing with displacement load and force load in the whole loading process.By comparing the simulation results with the test results,the accuracy and applicability of simulation methods are verified,and it is also proved that it is feasible to monitor the damage and corrosion of RC beams by FBG strain sensor,laying a foundation for the simulation in chapter 5.(5)In chapter 5,based on the mechanical loading test and simulation simulation of FBG strain sensor monitoring rust-free RC beams,simulation and prediction of 8 groups of FBG strain sensor monitoring RC beams with different degrees of corrosion are carried out.Firstly,the bearing capacity of RC beams with different degrees of corrosion is analyzed,and then the classification and data analysis are carried out from the aspects of numerical calculation and mean square error.Finally,eight different sets of data for the error analysis of grating measuring strain,and in the range of acceptable error,to build the relationship between optical fiber strain and degree of steel-bar corrosion expression,and carries on the data validation,the validation results show that the optical fiber monitoring of reinforcement corrosion degree of accuracy can reach 92.1%,high precision,formula fitting effect is good.