| In recent years,researchers at home and abroad have conducted a lot of research on the structure of solar greenhouses and achieved fruitful research results.However,for a long time,people have paid more attention to the research on the theory and method of solar greenhouse structure design,while ignoring the research on the damage mechanism of the skeleton structure and the evolution law of structural performance during the use process.Although the research on the safety and applicability of solar greenhouses has been paid attention to,the research on the durability of the skeleton is relatively lagging behind,resulting in insufficient research on the damage mechanism of the skeleton structure and the evolution of structural properties during the use of the solar greenhouse.At present,the research on the solar greenhouse structure mainly focuses on its safety and applicability,while the durability of the skeleton is guaranteed through protective measures,construction measures and maintenance systems.However,in fact,the corrosion rate of the skeleton structure under the alternating conditions of high temperature and high humidity and low temperature and high humidity is much faster than that of the steel structure normally exposed to the natural atmosphere,and its structural performance may change during service.Therefore,this paper uses the indoor accelerated corrosion test to measure the corrosion data of Q235 steel,undamaged galvanized steel,and damaged galvanized steel,and conducts gray correlation analysis with the data of natural exposure tests,and proposes a corrosion depth prediction model and ultimate tensile bearing capacity prediction.Model.And use the uniaxial tensile test data to verify.Using ANSYS Workbench to simulate and analyze the long-term skeleton safety of solar greenhouse.The main working conclusions are as follows:(1)Three samples(Q235 steel,undamaged galvanized steel,and damaged galvanized steel)were placed in a simulated solar greenhouse environment at three different temperatures(50°C,70°C and 90°C)with a humidity of 95%.environment for testing.Through the weight change,macroscopic and microscopic observation and analysis of the corrosion products before and after corrosion of the specimens,the corrosion behavior of the specimens in the simulated solar greenhouse environment was explored,focusing on the influence of temperature and galvanized layer damage on the corrosion rate of the specimens.The research results show that the relative increase in the corrosion rate of galvanized steel is greater from 50°C to 70°C than from 70°C to 90°C.Damaged galvanized steel still maintains good corrosion resistance at 50°C and 70°C,but at 90°C,the destruction of the galvanized layer will accelerate the corrosion of the substrate.At 90°C,because the corrosion products of the samples were loose and easy to fall off,the corrosion rate of each sample was the highest,and there was no slowing down trend.(2)The corrosion depth of Q235 steel,undamaged galvanized steel and damaged galvanized steel under the natural exposure conditions of the solar greenhouse was simulated,and the corresponding natural atmospheric corrosion type was selected according to the atmospheric physical and chemical characteristics of the solar greenhouse,and the 16-year natural exposure test data in Qionghai was determined as Based on the reference,and using the gray model GM(1,1)and the gray correlation degree to compare the indoor accelerated corrosion data of the three types of samples with the Qionghai natural exposure test data.The prediction model of corrosion depth and ultimate tensile bearing capacity of three types of samples is proposed,and the uniaxial tensile data of indoor accelerated corrosion samples are used for verification,which provides a theoretical basis for the subsequent mechanical degradation model of the solar greenhouse skeleton.It is believed that the proposed corrosion model can better simulate the degradation model of mechanical properties of samples in the solar greenhouse environment.At the same time,it was found in the research that the corrosion performance of Q235 steel is sensitive to 50°C,70°C,and 90°C,and it is proportional to the increase in temperature and the extension of corrosion time.The corrosion performance of undamaged galvanized steel has little change at 50°C and 70°C,but the mechanical properties degrade significantly at 90°C.The ultimate tensile capacity of damaged galvanized steel is inversely proportional to temperature,but the elongation basically does not change with temperature.(3)According to the solar greenhouse design code,the bearing capacity degradation analysis of two typical solar greenhouses in the Yangling area of Shaanxi was carried out,and the load size and combination form were selected for the solar greenhouse by the most unfavorable load principle.Using ANSYS Workbench software combined with the prediction model of corrosion depth and ultimate tensile bearing capacity,the finite element analysis of the Q235 steel solar greenhouse frame was carried out.Comparing the maximum displacement and stress values with the agricultural greenhouse structure design standards,the service life of the elliptical steel frame and the round tube steel truss is predicted.By comparing with the agricultural greenhouse structure design standards,it is found that the expected service life of the elliptical steel frame is 15 years,which is greater than the design service life(10 years).The expected service life of the round tube steel truss is more than 20 years.It provides reference and demonstration for other types of skeleton solar greenhouses. |
