# Dynamic Response of Drill Floor Considering Propagation of Blast Pressure Subsequent to Blowout
## 5 Structural Analysis
### Simulation Results and Discussion  
#### 5.2.1 Displacement of Frame and Plate of Drill Floor  
The response of the structure against blast pressure was evaluated through analytical and numerical studies [29; 30]. Figure 17 presents the displacement of the frame and plate when blast pressure was applied on the drill floor. The displacement of the frame (Figure 17a) shows clear oscillations unlike the plate in Figure 17b due to higher stiffness. The oscillation of the plate is more complicated than that of a single frame, because a plate has lower stiffness and requires more time for attenuation than a frame.  
For displacement of the frame, Overall Average (case-2) has the lowest amplitude of displacement due to the application of the lowest pressure. However, this is the average of the peak pressure of all pressure groups; therefore, using the average value of pressure could result in a less conservative design. Overall Peak (case-1) shows the largest amplitude of displacement among all cases. However, this case applies the highest pressure in each pressure group; therefore, this approach could result in a too conservative design. Group Peak (case-3) and Proposed (case-4) have the peak pressure levels  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Explosion Location**} & \multicolumn{3}{c}{**Load Cases**} & \multicolumn{2}{c}{**Steel Grade**} & \multirow{2}{*}{**Deflection**} & \multirow{2}{*}{**Strain**} \\ \cline{2-2} \cline{5-6}  & **No** & & **Description** & & **(MPa)** & \\ \hline \multirow{6}{*}{Under} & Overall & Pressure & Peak Pressure & 235 & \multirow{2}{*}{Frame} & Frame \\  & Peak & Area & All Area & 355 & & \\  & Case-5 & Time & Same Time & 460 & & \\ \cline{2-6}  & Overall & Pressure & Average Pressure & 235 & \multirow{2}{*}{Frame} & Frame \\  & Average & Area & All Area & 355 & & \\  & Case-6 & Time & Same Time & 460 & & \\ \cline{2-6}  & Group & Pressure & Peak Pressure & 235 & \multirow{2}{*}{Frame} & Frame \\  & Peak & Area & Each Area & 355 & & \\  & Case-7 & Time & Same Time & 460 & & \\ \cline{2-6}  & Proposed & Pressure & Peak Pressure & 235 & \multirow{2}{*}{Frame} & Frame \\  & Case-8 & Area & Each Area & 355 & & \\  & Time & Propagation & 460 & & \\ \hline \hline \end{tabular}
\end{table}
Table 7: _Cont._  
Figure 17: Displacement of (**a**) frame and (**b**) plate (material: S235).  
for each pressure group, which are reasonable pressure levels; however, the two cases have different methods of applying pressure according to time. Group Peak (case-3) applies pressure at the same time, whereas Proposed (case-4) involves propagation of blast pressure. Proposed (case-4) seems to be more realistic, since this reflects the actual pressure propagation shown in Figure 15. Proposed (case-4) has less amplitude of displacement than Group Peak (case-3). The difference in displacement according to the material is not expected. The displacements for S355 and S460 were similar to that for S235, as summarized in Table 8.  
Due to the complex behavior of displacement, clear characteristics are hardly observed in a plate, compared with the displacement of a frame. Fluctuations last longer than that in a frame due to the lower stiffness. The displacements for S355 and S460 were similar to that for S235, as summarized in Table 9.