# Scaled Model Simulation and Experimental Verification of Submarine Flexible Pipeline Laying System
## 3 Similarity Verification of Experimental Scaled Model
### Structural Strength Similarity Verification of Scale Model  
According to the stress state of each structure in each working state of the tower, the finite element analysis of each component of the tower can be carried out to check the stress and strain of each component. The maximum stress point of each component of the tower can predict the structural dangerous area during the laying of the tower. Therefore, the scale model and prototype of the tower can be finite elements analyzed separately in the stress analysis of the previous section. The comparative analysis is used to verify the similarity of the structural strength of the tower scale model. The force of each tower structure in each state is shown in Appendix C.  
According to the load on the tower, the finite element analysis of the tower is carried out in ANSYS workbench. The material properties of the scale model are the same as those of _Q235_ steel. The prototype material is _S690 QL_, and its yield strength, density, elastic modulus, and other parameters need to be set. In order to ensure the sufficient safety of the designed structure, the safety factor needs to be determined by the loading condition. Since the selected force is the maximum dynamic load and the impact condition is considered, the safety factor is 1.5. Figure 16: Force comparison diagram at the articulation of upper connecting rod of tower and tensioner support. Figure 15: Comparisons of stresses at the joint of the tower and support under tensioner support. It can be seen from Figure 17 that the maximum stress of the tower during pipe laying occurs at the connection position between the upper connecting rod and the tower. The maximum stress of the scale model \(\sigma_{max1}=228.5\) MPa is \(\sigma_{max2}=218.1\) MPa in the prototype, and the maximum stress of the scale model is about 5% larger than that of the prototype. For the angle adjustment mechanism, the maximum force is the starting time of the angle adjustment mechanism when the tower adjusts the angle. It can be seen from the three-dimensional model that the tower is in a 50\({}^{\circ}\) inclined state at this time, while the support rod of the angle adjustment mechanism is close to the vertical state and bears most of the gravity of the paved tower. Through finite element analysis in workbench, the stress of the scaled model and prototype two support rods can be obtained, respectively, and the results are shown in Figure 18. The max. stress of the angle adjustment mechanism is located at the articulation between the large support rod and the tower. The max. stress of the scale model is \(\sigma_{max1}=141.1\) MPa, and that of the prototype is \(\sigma_{max2}=127.3\) MPa. The max. stress of the scale model is about 11% larger than that of the prototype. Similarly, the components of the tensioner support can be analyzed by the finite element method, as shown in Figures 19 and 20, respectively. It can be seen that the maximum stress of the upper connecting rod of the tensioner support in the scale model and in the model occurs at the pinhole of the upper con  
Figure 17: Stress distribution during the vertical laying of the tower. (**a**) Scaled model; (**b**) prototype. Figure 18: Stress distribution at start-up of the angle adjustment mechanism. (**a**) Scaled model; (**b**) prototype. stress of the scale model \(\sigma_{max1}=129.3\) MPa, and the maximum stress of the prototype \(\sigma_{max2}=112.3\) MPa, respectively. The maximum stress of the lower connecting rod of the tensioner support is about 15% larger than that of the prototype. The maximum stress of the lower connecting rod of the tensioner support is located at the articulation between the tensioner and the lower connecting rod. The maximum stress of the contraction model \(\sigma_{max1}=124.1\) MPa, the maximum stress of the prototype \(\sigma_{max2}=116.96\) MPa, and the maximum stress of the contraction model is about 7% larger than that of the prototype.