UPV testing and tomographic approach for fire-damaged concrete members and indirect problem

Non-destructive tests are extremely popular in the evaluation of reinforced concrete structural elements exposed to fire. Among the non-destructive tests, we show that ultrasonic testing is very common. In general, studies in this area to be done in the geophysical field. And these studies in the field of geophysics are in large-scale, they need to be adapted to small-scale studies for use in civil engineering applications. In the evaluation of a reinforced-concrete structural element, we can use the method that allows us to know the behavior of ultrasonic waves in the material, which is expressed as a direct problem and the depth-dependent velocity variation in the deformed material. It is important to understand the source of problems such as the triplication that may occur in the distance-time graph obtained by the indirect method on the surface of the structural element. Understanding the reasons for this situation and determining the suggestions about the solution of the indirect problem is critical for solution. In the indirect problem, the aim is to obtain the graph of the depth-dependent velocity by calculating the distance-time graph obtained from the reinforced concrete structural element by the indirect method. and, consequently, the loss of strength after fire. The most basic problem with this technique is the detection of the d matrix, which are the distances ultrasonic wave traveled on each layer. In this thesis, it is mainly proposed to determine the situation causing triplication in the direct problem and suggestions about what can be taken in order to avoid this situation in the indirect problem. The results of the experiments with a reinforced concrete sample were calculated by using the simultaneous iterative reconstruction technique (SIRT).