## 3 Results  
### Single Module Strength Analysis of Offshore Airports  
The strength analysis of the offshore floating airport is very important because of its large volume and huge longitudinal dimension. Especially in bad sea conditions, the overall structure may be damaged. In the non-operational sea condition, the wave impact on the sea airport is more serious, and the oversized floating body structure will have a relatively obvious deformation, at which time, the aircraft should stop the take-off operation. Under normal operating conditions, the airport needs to ensure the normal take-off and landing  
\begin{table}
\begin{tabular}{l c c c} \hline \hline  & **Vibration Type** & **Steps** & **Rate/Hz** \\ \hline
4.659\(\times\)10\({}^{+}\) Max & & & \\
3.033\(\times\)10\({}^{+}\) & & & \\
4.142\(\times\)10\({}^{+}\) & &  
of aircraft, so the upper deck must be sufficiently flat and must not produce excessive undulations under operating sea conditions.  
Figure 6 shows that the maximum relative deformation of the single module floating body is 1.226 m under the self-storage condition. Figure 7 gives the structural deformation of the single module of the offshore airport in a Class 5 sea state. As can be seen from Figure 7, the maximum relative deformation of the single module floating body is 0.49 m, and the relative deformation at different positions on the floating body is very small, which fully meets the requirement of runway levelness for aircraft takeoff and landing as far as the single module is concerned.  
The structural stress clouds at the corresponding moments are given in Figure 8, From the figure, we can see that the maximum stress of the floating body module of the offshore airport occurs at the position where the column is linked to the upper and lower pontoons, and at the position where the lower cross brace is connected to the lower pontoon; the maximum stress is 5.15 Mpa. Figure 9 shows the stress cloud diagram of the single module of the offshore airport at Sea State 5. It can be seen from the figure that the stress distribution in the upper panel of the floating body is relatively uniform at this time, and the maximum stress is 1.88 Mpa. The deformation and stress analysis of the single module of the floating airport at sea under a non-operational sea state and operational sea conditions reveals that both deformation and stress were nearly three times higher in the self-storage sea state than in the working sea state; from the overall point of view, under a non-operational sea state, the floating body produced a slight longitudinal shaking. If the eight modules are connected, the longitudinal size is huge, and the longitudinal shaking will be significantly increased, while the stress distribution is also more uneven. On the surface of the pontoon, it is prone to a stress concentration phenomenon; at this time the sea floating airport is more dangerous. Although the single module floating body of the floating airport can meet the requirement of runway levelness for aircraft take-off and landing under the working sea condition and the stress distribution is relatively uniform, the maximum stress position occurs at the position where the column is connected with the upper and lower pontoons and the position where the lower cross brace is connected with the lower pontoon under both the non-operational and working sea conditions. Therefore, if the safety of the floating airport at sea is to be ensured, the strength of the structure at these locations needs to be increased by further design, pending further research.  
Figure 8: Stress under non-operational sea state.  
Figure 6: Deformation under non-operational sea state.  
Figure 7: Deformation under working sea conditions.