Then, the load was unloaded from maximum of each loading cycle to 0.5kN and was held for 2 minutes. The test was monitored by AE throughout the test. The measurements of load, midspan deflection, and AE data were recorded continuously during the three-point bending test.Figure that 1Sensor arrangements for the three-point bending test.4. Results Analysis and DiscussionThe RC frames described early were tested under loading cycle. Figure 2 shows typical cracks development in the RC frames specimen. The behaviour of all RC frames under loading cycle can be divided into seven stages of failure namely, (I) micro-cracking at the midspan of RC frame, (II) first flexural cracks at midspan of RC frame, (III) distributed flexural cracks at the midspan of RC frame, (IV) first cracks at the beam-column connection zones, (V) distributed cracks at beam-column connection zones, (VI) damage localization at the beam-column connection zone, (VII) failure at beam-column connection zone.
Figure 2A typical cracks development in the RC frames specimen.In order to explain AE source location analysis and the behaviour of RC frame specimens under loading cycle, the RC frame specimens were divided into 7 zones which are shown in Figure 3. Zone 1 is associated with the loading zone. Zones 2 and 3 are beam-column connection zone. Zones 6 and 7 are beam-supported region. The AE source location analysis in terms of absolute energy was performed that a sample will be explained.Figure 3Detail and dimension of specimen zones.SPRCF1 was tested under loading cycle. The load was applied under twenty load cycles in 10kN step.
This specimen failed at 120kN, and location of failure was beam-column connection zone. Figure 4(a) shows a photograph of crack development in SPRCF1. Also, two photographs of crack development in midspan and beam-column connection of this sample are shown in Figures 4(b) and 4(c).Figure 4Progression of growth cracking in an RC frame sample��SPRCF1.The photographs show that the first cracks are visible in loading cycle 4 (40kN), and location is at midspan of beam; also, the first cracks which are visible in beam-column are in loading cycle 7 (70kN). In addition, the photographs show the location of failure in loading cycle 12 (120kN). A summary of observation and absolute energy versus X position during loading cycle is presented in Table 1.
The AE source location analysis in terms of absolute energy according to seven stages of failure of the RC frame Drug_discovery specimen will be explained and discussed.Table 1A summary of AE source location analysis.In the first stage of failure, any crack was not visible by the naked eye. During loading cycles 1 to 2, AE activity was in low level throughout the RC frame specimen. Also, during cycle 3, two peaks of absolute energy were observed at zones 4 and 5. These peaks were 2.8 �� 106aJ and 2.1 �� 106aJ at zone 1 and 5, respectively.