Research On Concrete Stress Measurement With Coda Wave Interferometry

Concrete bridge’s section stress under permanent action is the key factor to evaluate the bearing capacity of concrete bridges in-service. The problem of concrete stress measurement which has not been solved successfully results in certain limitation in bridge evaluation. In order to solve the problem of concrete stress measurement, this paper explores the non-destructive concrete stress measurement way and try to exploit the coda wave interferometry which has gotten good results.This paper conducts two experiments. Concrete block coda wave interferometry experiment under uniaxial loading condition aims at studying the correlation between dv/v and stress state and further establish the mathematically judging model. Concrete T-beam coda wave interferometry experiment under four-point bend loading condition is to verify the accuracy of the model and explore the application of actual concrete stress measurement with coda wave interferometry.First of all, three groups of concrete blocks are made, whose size is 150mm×150mm×300mm. The maximum load is approximately 80% of the ultimate load. The purpose is to study the correlation between dv/v and stress state. Stretching method is used to analyze the data and then show the result by the drawing of dv/v-F and ε—F. This experiment verify that dv/v accords with rule of concrete damage development and is highly connected with the stress state. Furthermore, a model of concrete compressive areas about the correlation between dv/v and stress state is put forward.According to the conclusion of concrete block test, Concrete T-beam coda wave interferometry experiment under four-point bend loading condition is further conducted. It proves that dv/v and its slope can distinguish compressive areas(dv/v>0 and k>0) from tensile areas(dv/v<0 and k<0). What’s more, the model of concrete compressive areas is validated by the result of the compressive areas.To sum up, the application of the coda wave interferometry technique in the concrete stress measurement has been preliminary validated. With intensive study, the coda wave interferometry technique can develop to be one of the nondestructive testing ways in concrete stress measurement.