## 4 Seismic Response CFST Structure with BRBs under Earthquake Sequences
### Nonlinear Response Analysis under Sequence-Type Ground Motion
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Input** \\ **Motions** \\ \end{tabular} } & \multirow{2}{*}{**PGA (g)**} & \multirow{2}{*}{\begin{tabular}{c} **Mainshock** \\ **Only** \\ \end{tabular} } & \multicolumn{4}{c}{**Earthquake**} & \multirow{2}{*}{\begin{tabular}{c} **Difference** \\ **(\%)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Earthquake** \\ **Sequence** \\ **(\%)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Difference** \\ **(\%)** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Earthquake** \\ **Sequence** \\ **(\%)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Difference** \\ **(\%)** \\ \end{tabular} } \\ \hline M-AGW & 0.032 & 10.12 & 11.93 & 17.82 & 12.94 & 27.84 & 14.11 & 39.41 \\ A-CAT & 0.042 & 21.14 & 22.54 & 6.62 & 23.61 & 11.68 & 24.82 & 17.41 \\ A-STP & 0.049 & 23.18 & 26.65 & 14.95 & 26.66 & 15.00 & 31.47 & 35.75 \\ HIO6 & 0.060 & 13.42 & 14.61 & 8.88 & 15.75 & 17.42 & 18.79 & 40.08 \\ A-CTS & 0.062 & 19.74 & 20.84 & 5.55 & 22.82 & 15.60 & 26.22 & 32.80 \\ A-HAR & 0.070 & 47.32 & 48.08 & 1.62 & 51.35 & 8.53 & 57.41 & 21.35 \\ H-CO8 & 0.100 & 70.99 & 74.70 & 5.24 & 90.07 & 26.88 & 94.47 & 33.07 \\ H-CCA & 0.115 & 36.09 & 43.62 & 20.88 & 52.29 & 44.88 & 53.64 & 48.62 \\ H-CAL & 0.128 & 19.19 & 24.74 & 28.93 & 28.43 & 48.13 & 31.99 & 66.70 \\ H-CMP & 0.144 & 69.19 & 73.94 & 6.87 & 86.52 & 25.04 & 92.26 & 33.34 \\ BRA & 0.160 & 28.61 & 30.70 & 7.31 & 33.11 & 15.73 & 36.55 & 27.75 \\ M-GMR & 0.184 & 12.15 & 15.98 & 31.56 & 20.19 & 66.18 & 20.40 & 67.90 \\ M-G03 & 0.194 & 24.76 & 27.44 & 10.81 & 27.34 & 10.41 & 27.47 & 10.93 \\ M-GQ2 & 0.200 & 42.15 & 53.57 & 27.09 & 49.71 & 17.94 & 56.94 & 35.09 \\ A-DWN & 0.215 & 98.21 & 107.62 & 9.58 & 124.44 & 26.71 & 124.92 & 27.20 \\ FLE & 0.237 & 56.93 & 68.62 & 20.54 & 79.27 & 39.24 & 89.22 & 56.71 \\ C08 & 0.259 & 88.21 & 90.75 & 2.87 & 95.97 & 8.80 & 106.57 & 20.82 \\ H-CHI & 0.269 & 153.27 & 180.49 & 17.76 & 194.00 & 26.58 & 235.07 & 53.37 \\ A-BIR & 0.299 & 85.14 & 106.52 & 25.11 & 123.55 & 45.11 & 134.30 & 57.73 \\ I-ELC & 0.309 & 205.51 & 208.51 & 1.46 & 229.05 & 11.45 & 255.67 & 24.41 \\ A-CAS & 0.322 & 103.16 & 110.72 & 7.33 & 124.45 & 20.64 & 140.07 & 35.78 \\ H-DLT & 0.349 & 108.68 & 123.62 & 13.75 & 134.69 & 23.93 & 159.73 & 46.97 \\ HOL & 0.358 & 189.52 & 194.36 & 2.55 & 207.12 & 9.29 & 218.26 & 15.17 \\ CAP & 0.395 & 120.07 & 122.69 & 2.18 & 126.24 & 5.14 & 143.24 & 19.30 \\ G04 & 0.413 & 108.79 & 132.15 & 21.47 & 169.48 & 55.79 & 187.37 & 72.23 \\ Q03 & 0.547 & 169.79 & 174.69 & 2.89 & 180.37 & 6.23 & 259.14 & 52.62 \\ SCS & 0.612 & 430.69 & 504.98 & 17.25 & 598.28 & 38.91 & 697.79 & 62.02 \\ H-BRC & 0.780 & 197.14 & 214.99 & 9.05 & 243.75 & 23.64 & 259.11 & 31.44 \\ RFS & 0.834 & 659.33 & 717.68 & 8.85 & 794.27 & 20.47 & 837.11 & 26.96 \\ SPV & 0.939 & 272.37 & 286.98 & 5.36 & 292.49 & 7.39 & 356.46 & 30.87 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Maximum roof displacement under mainshock and earthquake sequence. The numerical results show that, under the earthquake sequences with 5 = 0.4, 0.6, and 0.8, the maximum roof displacement increases by approximately 1.46-31.56%, 5.14-66.18%, and 10.93-72.23%, respectively. The maximum ISDR increases by 2.99-51.47%, 7.32-67.01%, and 15.58-76.23%, respectively. Under the same earthquake sequence, with increasing \(\delta\), the maximum roof displacement and the maximum ISDR of the structure gradually increases. In summary, when the PGA of the selected ground motion is relatively small, the amplitudes of the foreshock and mainshock in the earthquake sequence are very small. After the foreshock, the structure is in an elastic state. After the mainshock, which has a slightly greater intensity than the foreshock, the structure is still in an elastic state. At this time, as the damaged structure experiences the aftershock, the risk of damage to structural members can greatly increase. When the PGA of the selected ground motion is relatively large, two situations may occur.