摘要
雪灾是导致日光温室倒塌的主要原因之一。为探明几字型钢日光温室在雪荷载作用下的失稳机理,该研究采用有限单元法,以8 m跨日光温室为研究对象,模拟其在雪荷载(均匀分布雪荷载和非均匀分布雪荷载)作用下的失稳破坏过程,计算其极限承载力,并探究纵向系杆、初始几何缺陷、截面参数对极限承载力的影响。结果表明:对于净截面面积、上翼缘宽度、腹板高度和壁厚均相同的几字型钢和空心矩形钢管,几字型钢日光温室极限承载力稍高于空心矩形钢管日光温室极限承载力;相较于均匀分布雪荷载,日光温室拱架对非均匀分布雪荷载更为敏感,非均匀分布雪荷载作用下的极限承载力约是均匀分布雪荷载作用下的28%,在日光温室结构设计中,应重点考虑非均匀分布雪荷载工况;在非均匀分布雪荷载作用下,屋脊和后屋面支座处为危险截面,最先进入全截面屈服状态;纵向系杆的设置可有效抑制结构平面外变形,进而提高结构极限承载力,有纵向系杆约束条件下的结构极限承载力约是无纵向系杆约束条件下的1.25倍;该日光温室拱架对初始几何缺陷敏感度较低,当最大初始几何缺陷幅值从5 mm增加到20 mm时,极限承载力降低约2%;在几字型钢截面选取时,在满足规范要求宽厚比前提下,建议上翼缘宽度与翻边宽度之比控制在4.17左右,腹板高度与翻边宽度之比不大于9.25,下翼缘宽度与翻边宽度之比不大于1.7,上翼缘宽度与下翼缘宽度之比控制在3.33左右,腹板高度与下翼缘宽度之比控制在4.67左右。该研究结果可为开口冷弯薄壁型钢日光温室拱架抗雪设计提供参考。
Hat-shaped steel members are widely used in solar greenhouses,due to their low cost,fast construction,and high material efficiency.This study aims to determine the ultimate bearing capacity of a solar greenhouse with the hat-shaped steel under snow loads.The typical solar greenhouse with an 8 m span and 3.8 m ridge height was selected as the research object.The finite element method(FEM)under ANSYS software was used to analyze the instability mechanism and failure modal of the structure under snow loads(uniform and non-uniform snow loads).An investigation was made to clarify the effects of the longitudinal tie bars,initial geometric imperfections,and sectional dimensions on the ultimate bearing capacity of the structure under non-uniform snow loads.Both the material and geometrical nonlinearity were considered in the finite element model.A bilinear kinematic hardening model was adopted for the steel with a yield strength of 235 MPa,Young’s modulus of 206 GPa,and Poisson’s ratio of 0.3.The geometrical nonlinearity was activated using the‘NLGEOM’option.To consider the local buckling,the greenhouse skeletons were then modeled with the Shell181 element suitable for the large strains and rotations.Fixed hinge supports were used for both ends of the skeleton.An arc-length method was utilized to trace the nonlinear load-displacement curve,in order to calculate the ultimate bearing capacity of the structure under snow loads.The ultimate bearing capacity of the solar greenhouse with the hat-shaped steel was slightly higher than that of the hollow rectangular section under the same conditions of net section area,upper flange width,web depth,and wall thickness.The solar greenhouse was more sensitive to the non-uniform snow loads,compared with the uniform ones.The ultimate bearing capacity of the hat-shaped steel solar greenhouse under non-uniform snow loads was about 28%of that under uniform snow loads.Therefore,some suggestions were presented for the non-uniform snow loads in the design stage of the solar greenhouse structure.The roof ridge and north roof end were dangerous sections under non-uniform snow loads,which firstly entered the full section yield state.The longitudinal tie bars were expected to effectively improve the ultimate bearing capacity of the greenhouse structure.The ultimate bearing capacity of the structure with the longitudinal tie bars was about 1.25 times that without tie bars.The ultimate bearing capacity was only reduced by 2%,when the initial geometric imperfections amplitude increased from 5 to 20 mm.It infers that the solar greenhouse was not sensitive to the initial geometric imperfection.The cross-section size of a hat-shaped steel was recommended that the ratio of the upper flange width to the lip width,the upper flange width to the lower flange width,and the web depth to the lower flange width were about 4.17,3.33,and 4.67,respectively,while,the ratio of the web depth to the lip width,and the lower flange width to lip width were less than 9.25 and 1.7,respectively.These findings can provide a strong reference for the solar greenhouse with the open cold-formed thin-walled steel under snow loads.
作者
王聪
姜迎春
徐占洋
张峰
白义奎
王铁良
Wang Cong;Jiang Yingchun;Xu Zhanyang;Zhang Feng;Bai Yikui;Wang Tieliang(College of Water Conservancy,Shenyang Agricultural University,Shenyang 110866,China;College of Engineering,Shenyang Agricultural University,Shenyang 110866,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2022年第19期172-179,共8页
Transactions of the Chinese Society of Agricultural Engineering
基金
辽宁省重点研发项目(2021JH2/10200022)
辽宁省科学研究经费项目(LJKZ0689)
国家建设高水平大学公派研究生项目(202108210256)
沈阳农业大学研究生创新培育项目(2022YCXB02)。
关键词
温室
承载力
荷载
有限单元法
失稳破坏
冷弯薄壁型钢
开口截面
截面优化
greenhouse
bearing capacity
load
finite element method
buckling failure
cold-formed thin-walled steel
open section
sectional optimization