# Dynamic Response of Drill Floor Considering Propagation of Blast Pressure Subsequent to Blowout
## 5 Structural Analysis
### Simulation Results and Discussion
#### 5.2.3 Strain of Drill Floor Frame for Applied Pressure  
Figure 19a presents the strain profile of frame S235 according to the applied pressure and load cases described in Figures 14 and 15. Overall Peak (case-1) has the largest strain value, followed by Group Peak (case-2) and Overall average (case-3). Proposed (case-4) showed the lowest level of strain. Therefore, the application of propagation of blast pressure can obtain a lower strain result.  
It is notable that Proposed (case-4) has the lowest strain level among all cases, although Overall average (case-2) has the average pressure of the panel. This is considered to be due to the new methodology of blast pressure application. Cases-1, 2, and 3 apply blast pressure at the same time; however, case-4 applies the blast pressure in a time interval. This results in the lower level of strain.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Areas**} & \multicolumn{4}{c}{**Material**} & \multicolumn{2}{c}{**Displacement**} \\  & & & & & **Ratio** \\ \hline Name & Dimension & Ratio & & S235 & S355 & S460 & \\ \hline Area-1 & \begin{tabular}{c} 2.375 m \(\times\) 1.305 m \\ 3.099 \\ \end{tabular} & 1.00 & \begin{tabular}{c} Min \\ Max \\ \end{tabular} & \begin{tabular}{c} -0.031 \\ 0.022 \\ \end{tabular} & \begin{tabular}{c} -0.031 \\ 0.022 \\ \end{tabular} & \begin{tabular}{c} -0.031 \\ 0.022 \\ \end{tabular} & 1.00 \\ \hline Area-2 & \begin{tabular}{c} 2.375 m \(\times\) 1.995 m \\ 4.738 \\ \end{tabular} & 1.53 & \begin{tabular}{c} Min \\ Max \\ \end{tabular} & \begin{tabular}{c} -0.076 \\ 0.060 \\ \end{tabular} & \begin{tabular}{c} -0.076 \\ 0.061 \\ \end{tabular} & 2.62 \\ \hline Area-3 & \begin{tabular}{c} 2.375 m \(\times\) 3.155 m \\ 7.493 \\ \end{tabular} & 2.42 & \begin{tabular}{c} Min \\ Max \\ \end{tabular} & \
\begin{tabular}{c} -0.091 \\ 0.072 \\ \end{tabular} &
\begin{tabular}{c} -0.089 \\ 0.073 \\ \end{tabular} & 3.13 \\ \hline \hline \end{tabular}
\end{table}
Table 10: Displacement of plate for areas in case-1.  
Figure 18: (**a**) Location of displacement measurement and (**b**) measured displacement of plate S235 for each area in case-1.  
Figure 19 presents the strain profile for load case-1 according to the material. S235 has the highest strain level and S460 has the lowest level. The displacements for the same load cases for different materials show almost the same result; however, the material with higher strength shows lower stain. This is due to the higher yield point. Generally, mild steel has been considered to have an advantage when steel experiences ductile behavior, since it has a higher capacity of energy absorbance. However, high strength steel has a low strain level for the same blast pressure. This is meaningful for design, since all blast prevention engineering targets a certain strain level, not a fracture of the structure. High strength materials are preferred for offshore structures due to the payload. Through this study, the selection of high strength materials is justified for strength and blast resistant designs. A plate has no strain at this blast pressure level due to its flexibility compared with a frame structure. A plate is considered to have more capacity for strain than a frame structure. The maximum strain for each load case and material grade is summarized in Table 11.