## 6 Discussion of the Control Effects of the Collapse Control System
### Lock-Up Clutch Control
#### 6.3.2 Analysis of Isolation and Collapse Control Effect of the LUC  
(1) Isolation effect  
The maximum locking force \(F_{\text{max}}\) is 10 kN, the maximum stroke \(D_{\text{max}}\) is \(\pm\)190 mm, and the control speed \(V_{0}\) is 0.02 m/s, considering results to be comparable to those of other control systems. In order to prove the rationality of the parameter setting, the El Centro wave case with a longitudinal PGA of 0.4 g was selected for inspection. The peak relative displacement between the side pier and the girder, in this case, was reduced from 12.3 mm of the BC system to 5.1 mm, which showed an isolation rate of 58.5%, illustrated in Figure 23a. The displacement control of the lock-up clutch scheme was better than that of the HDR isolation scheme or the FVD scheme, which was due to the fact that the locking force output was basically switched between \"output\" or \"non-output\" (see Figure 23b), which was very different from that of the FVD. Under the same ground motion, the output of the lock-up clutch of the CLUC system was larger than that of the damper of the CFVD system and directly reached the maximum locking force (see Figure 24). Therefore, the displacement response could be controlled more effectively, but the energy dissipation capacity of the lock-up components was poor, and its output effect was similar to that of rigid members. Thus, the contribution of the lock-up clutch to energy consumption is usually not taken into account. Figure 23: Time history curve: (**a**) relative displacement of side pier and girder; (**b**) output force of lock-up clutch. Figure 24: Comparison of the hysteretic curve between the lock-up clutch and the damper. Collapse Control effect  
Two typical seismic wave input conditions as mentioned earlier were used to illustrate the collapse characteristics of the CLUC system. Under the action of longitudinal El Centro seismic wave, the bridge model of the CLUC system finally collapsed when the PGA was 1.4 g, as shown in Figure 25. The specific process is as follows: when \(t\) was 0.83 s, the middle bearings failed, and the bottom of the middle pier began to be damaged; when \(t\) was 0.85 s, tendons were seen at the bottom of the middle pier; when \(t\) was 0.93 s, the damage of the bottom of the middle pier was serious and the uncovered tendons were enlarged; when \(t\) was 1.06 s, the longitudinal displacement of the top of the middle pier is 3 cm (see Figure 26a), so the bottom of the pier was completely destroyed, and the damage of the bottom of the main beam was aggravated by the loss of the support of the middle pier; when \(t\) was 1.26 s, the middle pier collapsed, and the vertical displacement of the pier top reached 31 cm (see Figure 26b). The main girder was seriously damaged, so it could be considered that the bridge model collapsed. Under the action of the longitudinal Chi-chi seismic wave, the bridge specimen of the CLUC system eventually collapsed with a PGA of 1.8 g, as exposed in Figure 27. The specific process was: when \(t\) was 16.6 s, the middle pier at the bottom was slightly damaged; when \(t\) was 16.86 s, the bottom of middle pier started to leak reinforcement; when \(t\) was 17 s, the damage at the bottom of the middle pier was aggravated, and the front and back of the pier column were all leaking bars, thus the damaged part was almost connected into a circle; when \(t\) was 17.02 s, the displacement of the top of middle pier was increased to 3.2 cm, and the middle pier failed completely; when \(t\) was 18.16 s, bearings on the side pier were sliding; when \(t\) was 18.34 s, the locking device failed for it exceeded the maximum stroke of 190 mm; when \(t\) was 18.58 s, the main beam moves longitudinally away from the left side pier; when \(t\) was 18.78 s, the middle pier was continuously swinging, with peak longitudinal displacement of 43 cm and peak vertical displacement of 18 cm (see Figure 28).