Issue 53

J. Akbari et alii, Frattura ed Integrità Strutturale, 53 (2020) 92-105; DOI: 10.3221/IGF-ESIS.53.08 99 Figure 9: The overturning moment under the 1994 Northridge earthquake As can be seen, the second part of the graphs resulted from high-period movements. The fluid pressure loads on the wall were calculated, and their reflection caused the fluid to move within the tank. The observed behavior of lateral loads revealed that the behavior of the fluid was initially induced by impulsive values and then by convective values. Tab. 3 provides the numerical results at the maximum load and the corresponding accelerogram record. Earthquake Tank Maximum Load Units (MN, MN.m) Time (s) Acceleration (g) 1940 El Centro T1 Lateral Load Overturning Moment 11.46 28.29 4.51 0.21 1940 El Centro T2 Lateral Load Overturning Moment 16.62 69.09 9.73 0.04 1940 El Centro T3 Lateral Load Overturning Moment 74.81 388.40 3.52 0.11 1994 Northridge T4 Lateral Load Overturning Moment 14.11 36.51 5.44 0.53 1994 Northridge T5 Lateral Load Overturning Moment 29.28 130.50 5.36 0.47 1994 Northridge T6 Lateral Load Overturning Moment 54.49 278.10 4.11 0.51 Table 3: The obtained results from applied earthquake records. As can be seen, the maximum loads did not occur at the time of the maximum acceleration. A comparison of the earthquake time histories and input accelerogram records with the load time histories reveals three different behaviors in the response time histories: 1. The maximum load occurs when the ground movement is large. For example, T6 overturned at 4.11 s with a ground acceleration of above 0.5g. 2. The maximum load happens when the total of the impulsive and vibrating movements of the fluid is maximum. For example, the maximum load of T2 happened at 9.73 s. 3. The maximum load takes place when the ground movement is medium but the reaction between the fluid movement and tank dynamic response is large. For example, T3 stayed stable at the maximum acceleration but overturned at 3.53 s at a ground acceleration of above 0.11 g. In this respect, higher impulsive modes have a strong effect on the general response of the tank-fluid system. Bottom sheet uplift Figs. 10 and 11 illustrate the vertical uplift time histories of the bottom sheet under the 1940 El Centro and 1994 Northridge earthquakes, respectively. For the tank-fluid system with a fluid height of 6 m, the bottom sheet exhibited no uplift when