Stress Drop and Stress Redistribution in Concrete Quantified Over Time by the b-value Analysis

Abstract

Stress redistribution and stress drop often coincide with fracture processes. The two experiments that were chosen for our b-value analysis generate failure processes with the corresponding stress drops and stress redistributions. Using acoustic emission analysis, the acoustic waves emitted from the different fracture areas are recorded. The cumulative frequency-magnitude distribution, which leads to the b-value, was originally used in seismology to characterize earthquake populations. Concerning acoustic emissions, the b-value decreases with increasing stress levels. Therefore, it was possible to determine the start of the arise of macro-cracks over time using the b-value analysis. Furthermore, a possible application in a monitoring procedure is suggested.

Acoustic emission characterization of the fracture process in fibre reinforced concrete

“…Therefore, it is reasonable to affect also the relative distribution of small and large events. The ''Ib-value'' represents the ratio of weak to strong events [19]. As mentioned above, micro-cracks generate a large number of weak acoustic emissions.…”

“…Apart from the early drop of Ib-value, the minimum value of each Ib curve was exhibited at the moment of fracture, (values of approximately 0.03). In literature the value of 0.05 is generally considered the threshold below which severe damage is indicated [18][19][20][21]. Although in laboratory conditions identification of the fracture moment is not an issue due to the load drop, as well as, the appearance of visible cracks, this is not always the case for a real structure where a similar crack will not produce visible deflection.…”

Application of a moment tensor inversion code developed for mining-induced seismicity to fracture monitoring of civil engineering materials

“…Grosse and Ohtsu (2008). Qualitative techniques such as b-value analysis based on Gutenberg and Richter's original work (Gutenberg and Richter, 1949) have been paid particular attention to because they are relatively straightforward to implement (Carpinteri et al, 2009;Colombo et al, 2003;Kurz et al, 2006;Schumacher et al, 2011;Shiotani et al, 2000). Quantitative seismology techniques such as moment tensor inversion (MTI) are still being evaluated in the laboratory (Finck et al, 2003;Katsaga et al, 2007;Köppel, 2002;Ohtsu, 1991;Yuyama et al, 1999).…”

Damage Assessment in Fibrous Composites Using Acoustic Emission

“…As a result, the AE technique can be used in laboratory conditions in order to monitor the fracture process of engineering materials and build an understanding on the damage behavior of materials under stress or other degradation factors (Carpinteri et al 2010, Scholey et al 2010, Philippidis et al 1998, Ohtsu and Watanabe 2001, Kawasaki et al 2010. It is also employed in real structures to monitor the cracking activity under service load (Shiotani et al 1999, Aggelis et al 2010a, Kurz et al 2006, in order to estimate the structural integrity of rock mass related to landslide incidences (Shiotani 2006), of tanks and pressure vessels (Anastasopoulos et al 2009, Anastasopoulos andTsimogiannis 2004), while application in composite laminates is extensive (Anastasopoulos and Philippidis 1995, Prosser et al 1995, Hamstad 1986, Katerelos et al 2009). Monitoring of AE behavior supplies information on several levels.…”