Çelik fiberli betonarme kirişte akustik emisyon aktivitelerinin Ib değeri analizi ile değerlendirilmesi

Abstract

Ib value analysis was applied to investigate effect of the steel fiber on Ib value.  Damage in steel fiber reinforced concrete beam was evaluated by AE parameter analysis.  Ib value distribution is affected after post-peak because of higher amplitude values due to steel fiber activities. There are numerous nondestructive testing methods that are used to determine damages within structures. Acoustic Emission (AE), being one of these methods makes it possible to obtain significant pieces of information such as origin time, location and type of damage formed in a material during loading by analyzing AE data using various algorithms. Ib value analysis is one of these algorithms which is based on AE signal and this analysis enables to have information on formation of new cracks or propagation of existing cracks by scaling the magnitude of AE activities. In this study, in order to investigate effect of the steel fiber in concrete matrix on Ib value, two reinforced concrete beams were tested under simple bending while one of them was the reference. Afterwards, AE parameters obtained were analyzed, Ib value analyses were applied to amplitude values and these parameters were associated to each other. Furthermore, effect of steel fiber existence on behavior of the beam and distribution of Ib value were examined. Figure A. Ib value vs time distributions of the test specimens Purpose: In this study, it was aimed to evaluate AE activities of plain and steel fiber reinforced concrete beams by Ib value analysis and to reveal effects of steel fiber presence on Ib value distribution. Theory and Methods: Ib value analysis is a technique to evaluate Acoustic Emission (AE) data for scaling failure mechanisms. While higher Ib values indicate more activities having lower amplitude (micro activities), lower Ib values show less activities having higher amplitude (macro activities). Results: Figure A indicates the lowest Ib values in Test Specimen-1 at 41 st and 114 th sec when the beam reached up to 56% and 82% of its ultimate capacity. Likewise, the lowest Ib values in Test Specimen-2 were observed at 69 th and 112 nd sec when the beam reached up to 59% and 75% of its ultimate capacity. These states point out that Ib value gives a warning before macro failures. Decrease of Ib values reveals cracking of concrete matrix in pre-peak region. However, presence of steel fiber affects the Ib value distribution at post-peak region due to higher ductility. Conclusion: Increase in AE energy and amplitude causes lower Ib values because of macro damages. Thus, Ib value can be used as a damage parameter for AE analysis. While higher Ib values indicate micro activities, lower Ib values show macro activities. Presence of steel fiber increases ductility of reinforced concrete beam; thus Ib value distribution is affected after post-peak because of higher amplitude values due to steel fiber activities in this region.