Internal force analysis and structure optimization of single oval tube arch solar greenhouse with flexible insulation wall

The ever-increasing span can be found in the single-pipe arch solar greenhouse in recent years. But the cross-section of the rods cannot be adjusted in real time. This study aims to ensure the structural Safety Issues in this case. The research object was taken as the 12m-span solar greenhouse with a flexible thermal insulation wall. A test example was selected as the solanaceous solar greenhouse in Beijing of China. An oval tube was used with a commonly-used section of 80 mm×30 mm×2.0 mm (Height×width×wall thickness). A ‘Midas-Gen finite element software’ was utilized to analyze the greenhouse hanging, and boundary conditions. Finally, the structural parameters were optimized, according to the national standard "Agricultural Greenhouse Structure Load Code" (GB/T 51183-2016) and "Agricultural Greenhouse Structure Design Standard" (GB/T 51424-2022). The results show that the maximum stress was 1146.7 N/mm², when the crop load was suspended at two points and the column feet were hinged in the greenhouse. The position of the maximum stress was the hanging point on the rear wall. The crop load C was the main control load, and the average stress value was 445.4 N/mm² at other positions. Therefore, the small number of hanging points and the large concentrated load at the hanging points were attributed to the extremely uneven distribution of the internal force of the arch frame. The structural parameters were optimized to increase the number of hanging points, in order to disperse and reduce the local concentrated load. As such, the peak value of concentrated stress was effectively reduced to improve the uniformity of the internal force distribution of the whole structure. Furthermore, the arrangement of hanging loads was also optimized to combine with the local reinforcement and adjustment of boundary conditions. The internal force of the structure was reasonably distributed to reduce the stress of the structural skeleton. Further research was recommended that: 1) The increasing hanging points of the crops can be expected to effectively reduce the peak value of internal force. Once the hanging points increased to the three-point type, the hanging load degenerated into a secondary control load, whereas, when increased to the four-point type, the crop load quit the control role. 2) The rest direction was the partial strengthening of weak parts. The rear wall was adjusted from a single tube to a lattice column, while the maximum stress was reduced by about 48%, indicating a more significant improvement. 3) The connection form of column feet was adjusted, when fixed the front and rear column feet of the solar greenhouse with the single-tube arch frame. Once the rear wall arch frame was adjusted to the lattice columns, the hinged form was used to optimize the front column foot. This finding can also provide a strong reference for the structural form and structural materials of flexible insulation wall oval tube single tube arch type solar greenhouse.