Study On Dectection Of Internal Defects Of Concrete Structure With ITECS

With the rapid development of civil engineering in recent years, the structural type become more and more complex, and the security performance of civil engineering also become more and more high. But there are always some different forms of defects in the concrete structure due to construction control or environmental factors. These defects of concrete structural have different degree of influence on structural integrity, mechanics and durability. So it is necessary to take an effective nondestructive testing method without the destruction of structures for the concrete internal defects detection.Firstly, the principles of the impact-echo method were described in details in the paper.Meanwhile the paper introduced the advanced and mature concrete nondestructive detection instrument iTECS which is widely used in Japan, as well as the impact-echo method which is the principles of iTECS testing. This paper introduced two frequency spectrum analysis methods which are MEM and FFT. The results showed that MEM analysis method is higher than FFT analysis method in precision and resolution.It was found that iTECS that based on impact-echo method can accurately detect the thickness of concrete structure and the error within5%through testing the concrete thickness and internal defects of many different Concrete bridges which are in the LangFang and ChengDe city.Judging the different methods of concrete internal segregation, not dense and voids according to the measured thickness. It was showed that there were voids in the concrete if the thickness of the test was significantly less than the actual thickness of the concrete structures, there was segregation and not dense in the concrete if the thickness of the test is much larger than the actual thickness of the concrete structures.Imitate the process of using iTECS that based on impact-echo method to measure concrete thickness with the help of ABAQUS platform. It was found that the thickness of the simulation test was generally consistent with the actual situation through analysing the measured signal with MEM and FFT. Set the same plain concrete and reinforced concrete geometric model on size, material, striking the points with the help of ABAQUS platform according to the measuring results. Then simulated the process of thickness test on them. The steel had a little effect on the results of thickness which was test on the model. Meanwhile stirrup spacing made little effect on the reinforced concrete thickness which was test with iTECS.Test the old bridge (San Xiaoying Bridge) and new birdge (Zhong Guan Bridge) which are used different strength grade of concrete with iTECS. Imitate the process of using iTECS that based on impact-echo method to measure different strength grade of concrete thickness with ABAQUS. The results showed that the concrete strength grade had no effect on the measurement accuracy.Set the model of T beam with holes according to the results of thickness which was tested on the surface voids of T beam of San Xiaoying South Bridge with iTECS. The simulation results showed that the test thickness of concrete with holes was significantly smaller than the actual thickness of concrete and the holes position consistent with the actual position. Set the model of bridge deck according to the actual size of Xi Zhuangzi bridge. The thickness of the simulation was consistent with the results of measuring with iTECS. It showed that iTECS can accurately measure the position of holes and determination of the depth of holes.Simulation the process of testing the thickness of sheet, it was significantly different between the results and actual conditions. The impact elastic wave lead to bending vibration of sheet, the reception signal of sensor become complex The measuring error was large when test the thickness of sheet with the method of impact elastic wave.