| Traditional solar greenhouses in severe cold areas lack sunlight in winter,and crop production needs to be heated,resulting in an increase in the cost of greenhouse construction.The production of greenhouse is unstable because of low temperature,which greatly affects the yield and quality of fruit and vegetable in winter.This paper optimizes the design of solar greenhouse in cold area from the aspects of lighting and heat preservation,improves the performance of lighting and heat preservation,optimizes the truss structure,saves the construction cost,and achieves the high efficiency and energy saving.The main findings are as follows:1.Taking Changchun Area(LRB-latitude43°05′～45°15′)as an example,in daylighting design,the objective is to obtain the maximum amount of sunlight and the optimum overall truss structure of the greenhouse,in thermal insulation design,the thermal resistance of the rear wall and the rear slope is increased,in order to reduce the gap and increase the heat preservation ratio of the greenhouse,the structure and size parameters of each part of the solar greenhouse were determined.The azimuth angle of the greenhouse is 12.5 to the west of the south,the reference angle of the front slope is 37.51°,the span is 8 m,the ridge height is 3.8 m,the wall is constructed by 240 red brick + 120 benzene plate + 240 red brick,the height of the back wall is2.8 m,the horizontal projection width of the rear roof is 1.4 m,which can provide reference for greenhouse construction in severe cold area.2.In order to ensure the safety and rationality of the structure,the greenhouse truss structure follows the design principle of the most unfavorable load combination.This study is based on the industry specifications and related load analysis theory.Four kinds of adverse load combinations suitable for solar greenhouse in cold region are determined:(1)roof mounted after snow;(2)The south wind rolled up the roof insulation quilt;(3)The south wind put down the roof insulation quilt;(4)The north wind picked up the roof insulation quilt.It provides the basis for the subsequent analysis of the greenhouse structure stress stability.3.Based on the establishment of the finite element analysis model of the greenhouse,the finite element analysis model of the sunlight greenhouse in severe cold area was established by using the finite element analysis software ANSYS19.2,the stress diagram,axial stress diagram,displacement diagram and displacement vector diagram obtained from the stress diagram,axial stress diagram and displacement vector diagram are analyzed,under the four load combinations,the deformation of the members is less than 1.6% of the greenhouse span,and the maximum stress is less than the allowable stress of 235 Mpa,which meets the requirement of the bearing capacity.The results show that the maximum stress value(44.1Mpa),the maximum axial stress value(35.6Mpa)and the maximum displacement value(0.00975m)of the whole structure under the load combination 4 working conditions are obtained,that is,the most unfavorable load combination mode of greenhouse studied in this paper is load combination 4-wind-driven roof insulation quilt.4.Using the optimization module of ANSYS Software,taking the total amount of steel used in greenhouse as the objective function,the section sizes of upper and lower chords,webs and transverse ties of truss are optimized,the results show that the total steel consumption(steel quality)is reduced by 14.3% after optimization,which achieves the goal of reducing the steel consumption of greenhouse truss and saving the cost of greenhouse construction.The maximum stress is 35.6 mpa<allowable stress =[σ] 235 Mpa,the axial stress is 15.4 Mpa,and the maximum displacement is0.000745m<0.128m(8.0m×1.6% = 0.128 m),that is,the optimized solar greenhouse is safe and stable. |
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