An Impact-Echo Experimental Approach for Detecting Concrete Structural Faults

For the current problem of detection of grouting defects in posttensioned prestressed concrete members, the paper takes a single-layer arrangement of prestressed pipes as the object of study. The influence law of the main factors such as pipe material, defect size, defect critical surface location, and prestressing reinforcement location on the results of the impact-echo method for detecting concrete grouting defects was studied. Firstly, the ABAQUS finite element software was used to simulate these factors to obtain the influence law on the detection results, and a modal test was conducted to verify them. The results show that the impact-echo method can effectively test the location of defects and the degree of burial depth, and the pipe material influences the test results, and the impact of corrugated metal pipe is smaller and more accurate than the PVC pipe. In addition, the greater the plate thickness frequency drift rate, the larger the transverse size of the defect, so the plate thickness frequency drift rate and the measured defect depth are combined to quantitatively determine the depth of the defect.

Research of the bridge structure by impact-echo method

This article reflects the results of studies of the operated bridge on the river Mozdernyak in the municipality of Kneginek (Croatia), which was subject to expert analysis of the needs of reconstruction. In the process of field research of the structures of the considered bridge, the Impact-Echo method was used and at the same time the peculiarities of the method of this method were investigated. In particular, on the basis of the Impact-Echo method, the construction of the old part of the studied bridge was checked, as well as the connection of this old part with the new part of the bridge was checked. Also, studies on the example of the construction of this bridge found that the acoustic properties of the wall components (brick, block and mortar) are quite similar, that in most cases masonry building elements respond to Echo-Impact as a solid block and this should be taken into account. This method allows you to detect cavities in several walls and assess their scale and impact on the strength of structures. The use of research equipment provided by the Impact-Echo method allowed to investigate the deposition of concrete in the lower and upper reinforcing zones of the bridge, as well as to determine the existing boundary between the layer of concrete and asphalt. Thus, the results of the research presented in the article allow to improve the methodology of research of bridge structures by the Impact-Echo method. In addition, expert opinions were made on the condition and prospects of operation of the bridge considered in this article - the bridge structure is in a satisfactory condition, which allows its operation. However, after some time it is recommended to repeat the research of the bridge using the method of the Beat-Echo method, with the continuation of the research areas to a new section of the bridge.

Diagnostics of Reinforcement Conditions in Concrete Structures by GPR, Impact-Echo Method and Metal Magnetic Memory Method

It is important to use adequately reliable non-destructive methods that would be capable of determining the reinforcement conditions in concrete structures. Three different methods: ground penetrating radar, impact-echo method, and metal magnetic memory method were used for testing laboratory-prepared reinforced concrete beams (with a reinforcing bar of the same diameter along its whole length, reinforcing bar locally impaired, and reinforcing bar interrupted). The ground-penetrating radar proved the correlation of signal parameters with the reinforcing bar condition. An impairment/interruption reinforcing bar appeared in the record from measurements in the transversal and longitudinal direction by changes of the observed depth of the reinforcing bar from the concrete surface and direct wave attenuation. The impact-echo method proved that the shifts of the dominant frequencies from the response signal correspond with the impairment/interruption of the reinforcing bar. Results of diagnostics by the metal magnetic memory method were presented by a magnetogram of the magnetic field strength and field gradient on the measured distance. The changes in the magnetic field strength proved different stress concentration zones due to the reinforcing bar condition. The used non-destructive methods showed that they are capable of indicating the different reinforcement conditions in reinforced concrete beams. This paper indicates in which cases and for what reason it is appropriate to use these three methods and in what way they differ from each other.