# Structure Analysis of the Fractionator Overhead Vapor Line of a Delayed Coker Unit
## 3 Seismic and Wind Load Analysis
### Analysis of Seismic and Wind Effects
#### 3.2.1 Vibration Caused by a Magnitude 2 Wind or a Magnitude 1 Earthquake  
According to the structure analysis of the pipeline system, Table 5 shows the vibration mode frequencies and maximum harmonic response stresses of the pipeline system under a magnitude 2 wind or a magnitude 1 earthquake, and Figures 5-16 show the stress distribution of the pipeline system. Because the region near the earth's surface can be viewed as the boundary layer of the atmosphere, only the parallel mode of the wind load needs to be considered while the vertical mode does not need to be considered. However, the shaking motion due to the earthquake may include parallel mode or vertical mode, so the seismic part in Table 5 consists of parallel and vertical modes. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Magnitude** & **Description** & **Acceleration** & **Upper Limit (m/s\({}^{2}\))** \\ \hline
0 & Micro earthquake & 0–0.8 gal & 0.008 \\
1 & Very minor earthquake & 0.8–2.5 gal & 0.025 \\
2 & Minor earthquake & 2.5–8 gal & 0.08 \\
3 & Light earthquake & 8–25 gal & 0.25 \\
4 & Moderate earthquake & 25–80 gal & 0.8 \\
5\((-)\) & Strong earthquake & 80–140 gal & 1.4 \\
5\((+)\) & Strong earthquake & 140–250 gal & 2.5 \\
6\((-)\) & Very strong earthquake & 250–440 gal & 4.4 \\
6\((+)\) & Very strong earthquake & 440–800 gal & 8 \\
7 & Great earthquake & \(>\)800 gal & \(>\)8 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Seismic classification [33]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Magnitude** & **Derivation** & **Acceleration** \\  & **(m/s\({}^{2}\))** \\ \hline
2 & 1 kgf/m\({}^{2}\)\(\times\) 60.3 m\({}^{2}\)\(\times\) 9.8 N/kgf \(\div\) 32,189 kg & 0.018 \\
3 & 3 kgf/m\({}^{2}\)\(\times\) 60.3 m\({}^{2}\)\(\times\) 9.8 N/kgf \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Pipelines Connected**} & \multicolumn{3}{c}{**Pipelines Unconnected**} \\ \cline{2-7}  & **Case 1** & **Case 2** & **Case 3** & **Case 1** & **Case 2** & **Case 3** \\ \hline  & \multicolumn{3}{c}{**Static stress (MPa)**} \\ \hline  & \multicolumn{3}{c}{\(11.854\)} & \multicolumn{3}{c}{9.0853} \\ \hline
**Mode** & \multicolumn{3}{c}{**Vibration frequency (Hz)**} \\ \hline
1 & 9.223 & 9.223 & 9.223 & 9.223 & 9.223 & 9.223 \\
2 & 23.027 & 23.027 & 23.027 & 23.027 & 23.027 & 23.027 \\
3 & 29.084 & 29.084 & 29.084 & 29.084 & 29.084 & 29.084 \\
4 & 29.398 & 29.398 & 29.398 & 29.398 & 29.398 & 29.398 \\
5 & 37.67 & 37.67 & 37.67 & 43.657 & 43.657 & 43.657 \\
6 & 45.418 & 45.418 & 45.418 & 45.835 & 45.835 & 45.835 \\ \hline  & \multicolumn{3}{c}{**Maximum harmonic response stress (MPa)**} \\ \hline
1 & 0.0025649 & 0.29822 & 0.21472 & 0.0025649 & 0.29822 & 0.21472 \\
2 & 0.043676 & 0.46407 & 0.33413 & 0.02916 & 0.46407 & 0.33413 \\
3 & 0.057938 & 0.048323 & 0.034793 & 0.035353 & 0.033957 & 0.024449 \\
4 & 0.059103 & 0.049841 & 0.035885 & 0.035808 & 0.032113 & 0.023122 \\
5 & 0.25085 & 0.46965 & 0.33815 & 0.29293 & 0.4252 & 0.30615 \\
6 & 0.60409 & 0.19279 & 0.13881 & 0.29233 & 0.4371 & 0.31471 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The vibration mode frequencies and maximum harmonic response stresses of the pipeline system under a magnitude 1 earthquake (Case 1: vertical mode, Case 2: horizontal mode) or a magnitude 2 wind (Case 3). Figure 5: Stress distribution of the vibration mode 5 under magnitude 1 earthquake (vertical mode) for unconnected pipeline system. Figure 6: Stress distribution of the vibration mode 6 under magnitude 1 earthquake (vertical mode) for unconnected pipeline system. Figure 7: Stress distribution of the vibration mode 5 under magnitude 1 earthquake (parallel mode) for unconnected pipeline system. Figure 8: Stress distribution of the vibration mode 6 under magnitude 1 earthquake (parallel mode) for unconnected pipeline system. Figure 9: Stress distribution of the vibration mode 2 under magnitude 2 wind for unconnected pipeline system. Figure 11: Stress distribution of the vibration mode 5 under magnitude 1 earthquake (vertical mode) for connected pipeline system.