## 4 Upscaling to RC Beams  
### Experimental Setup of the RC Beams  
The clustering algorithm was scaled up towards RC beams. Two test series were performed. For each test series, two beams were considered, further denoted as Beam-1 and Beam-2 for test series 1, and Beam-3 and Beam-4 for test series 2. The corrosion process was accelerated using the same principle as for the RC prisms. However, it was chosen to place a bottomless tank on top of the beams. The tank was sealed with silicone and the 5% sodium chloride solution was added in this tank. A current density of 50 \(\upmu\)A/cm\({}^{2}\) was applied. For test series 1, the dimensions of the beams were 150 \(\times\) 200 \(\times\) 1800 mm\({}^{3}\). They were reinforced with a ribbed rebar having a nominal diameter of 14 mm. The concrete cover was 30 mm. Nearly the full length of the rebar (1500 mm) was exposed to corrosion. The same AMSY-6 Vallen acquisition system (ASIP-2, standard version) with six channels and piezoelectric sensors were used as for the RC prisms. The beams were monitored with four AE sensors which were placed in a 2D AE sensor setup. Two sensors were placed at each side of the beam covering the central part of the beam. The distance between the AE sensors along the length of the beam varied for Beam-1 (750 mm) and Beam-2 (500 mm). The amplitude threshold, pre-trigger time, duration discrimination time, and rearm time were set to 40 dB, 200 \(\upmu\)s, 450 \(\upmu\)s, and 5 ms, respectively. The sampling rate was set to 5 MHz. With 4096 samples being stored, the total length of the signal was 819.2 \(\upmu\)s. The digital frequency filter was set between 95 and 850 kHz. Crack measurements were performed once a week with a crack meter having an accuracy of 0.05 mm, using 17 measurement points with a spacing of 100 mm. A schematic representation of the setup and position of the AE sensors is shown in Figure 7.  
For the second test series, two RC beams with dimensions 150 \(\times\) 220 \(\times\) 3000 mm\({}^{3}\) were cast. Two longitudinal rebars with a diameter of 14 mm were used in the tension zone, whereas two longitudinal rebars with a diameter of 12 mm were used in the compression zone. Additionally, stirrups having a diameter of 6 mm were spaced 120 mm at the center and 100 mm beyond. The concrete cover of the longitudinal rebars was 30 mm. Corrosion was induced in a small zone meaning that only 400 mm of the two longitudinal rebars and part of the stirrups could corrode. The position of this zone varied for Beam-3 (symmetrically, at the center) and Beam-4 (asymmetrically, towards the side). To prevent  
Figure 7: Schematic representation of the accelerated corrosion setup and 2D AE sensor configuration (S1–S4) of the first test series of RC beams (Beam-1 and Beam-2). the other parts to corrode, anti-corrosive paint was used to coat the rebars. An AMSY-6 Vallen system (ASIP-2, advanced version) with eight channels was used. The same sensors (flat response 100-400 kHz) were applied. The AE sensor arrangement was kept the same for both beams. Six sensors were used, three on each side of the beam. The distance between the sensors was 1000 mm. The amplitude threshold, pre-trigger time, duration discrimination time, and rearm time were set to 40 dB, 200 us, 500 us, and 5 ms, respectively. The sampling rate was set to 5 MHz. With 4096 samples being stored, the total length of the signal was 819.2 us. As this Vallen system allowed choosing between more digital frequency filters, the digital frequency filter was set between 50 and 500 kHz during acquisition to eliminate electromagnetic noise during the test. However, the lower limit was adapted to 95 kHz during post-processing in order that the results are comparable with the other samples. Crack measurements were performed once a week with a crack meter having an accuracy of 0.05 mm at different locations with a spacing of 50 mm.