r - The Hong Kong Polytechnic University

Figure 12 Force vs. displacement curves for RC column and FRP-wrapped RC column
EXPERIMENTAL RESULTS
Experimental Results of RC Column
The reversed cyclic loading protocol shown in Figure 6 was implemented to gradually test the RC
column until failure. During the loading procedure, smart aggregate-based health monitoring
system 1 (active-sensing approach) was implemented at the positive loading peaks, the zero
loading points and the negative loading peaks of the cyclic loading protocol. Figure 13 shows the
damage index matrix for the column, defined in Equation (3). Figure 14 shows the weighted
damage index, defined in Equation (4).
During the health monitoring test using an active-sensing based approach, PZT2 was used as an
actuator to excite a sweep sine wave and the other smart aggregates were used as sensors to detect
the wave responses. From the damage index matrix results shown in Figure 13, the damage index
increases significantly at Test Number 6, one cycle before the first major cracks were seen in the
RC column. This likely indicates internal damage in the column before it could be seen externally.
The weighted damage index matrix reveals the overall damage status of the column. From the
weighted damage index matrix results shown in Figure 14, it can be seen that the index
dramatically increases after test number 6 which means the overall damage status became severe
after test 6.
Damage index
1
0.5
0
1 2 3 4 5 6
Sensor No.
5
Test No.
Figure 13 Sensor History Damage Index
Matrix plot for RC column (active-sensing
approach)
10
15
Weighted damage index
1
0.8
0.6
0.4
0.2
0
0 5 10 15 20
Test No.
Figure 14 Weighted damage index for RC column
(active-sensing approach)
Experimental Results of FRP-Wrapped RC Column
The reversed cyclic loading protocol shown in Figure 9 was implemented to retest the
FRP-wrapped RC column. During the loading procedure, smart aggregate-based health monitoring
(impact response-based approach) was implemented at the positive loading peaks, the zero loading
points as well as the negative loading peaks of the cyclic loading protocol.
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