柔性保温墙椭圆管单管拱架日光温室内力分析及结构优化

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

    • 摘要: 针对柔性材料围护椭圆管单管拱架日光温室跨度不断加大,而标准化管材市场供应截面单一带来的结构安全性问题,该研究基于北京地区的风、雪荷载,依据国家标准《农业温室结构荷载规范》(GB/T 51183-2016)和《农业温室结构设计标准》(GB/T 51424-2022),选用截面80 mm×30 mm×2.0 mm(高×宽×壁厚)椭圆管,以12 m跨度日光温室为基准,使用Midas-Gen有限元软件建立模型,分析不同作物吊挂模式、后墙立柱不同结构形式以及拱架与基础不同连接形式对结构内力分布的影响,寻找结构最大应力最小的作物吊挂模式和结构形式。结果显示:柱脚铰接的单管拱架作物荷载2点吊挂时,出现强烈的局部应力集中,且作物荷载为主要控制荷载。其中后墙立柱作物吊挂点位置最大应力值为1146.7 N/mm2,其余位置平均应力值为445.4 N/mm2。作物荷载为3个吊挂点时,拱架应力系数为0.61,作物荷载退化为次要控制荷载;吊挂点个数≥4时,拱架应力系数降低到约0.51,作物荷载完全退出控制作用,拱架最大应力仍超出材料允许强度。因此,采用局部加强措施同时结合柱脚连接形式寻找更加合理的拱架结构,并最终提出该温室结构采用前柱脚铰接、后柱脚固接、后墙立柱为格构柱时结构的最大应力最小,应力分布最合理。研究可为北京地区柔性保温墙椭圆管单管拱架日光温室的结构形式和结构用材提供参考。

       

      Abstract: 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.

       

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