基于振动台试验的Venlo型温室抗震性能分析

    Seismic performance analysis of Venlo greenhouse in shaking table test

    • 摘要: 《农业温室结构设计标准》(GB/T 51424-2022)规定“抗震设防烈度为8度(0.30 g)及以上地区的农业生产用玻璃温室结构设计应计算地震作用”,为探究Venlo型温室的抗震性能及地震响应,对一形状规则的Venlo型温室其中1跨2开间制作缩尺模型进行振动台试验,研究模型结构的动力特性,以及在7度多遇地震(加速度时程最大值为0.035 g)、7度设防烈度地震(加速度时程最大值为0.10 g)、7度罕遇地震(加速度时程最大值为0.22 g)、8度罕遇地震(加速度时程最大值为0.40 g)及8度半罕遇地震(加速度时程最大值为0.51 g)作用下结构的加速度响应。结合ANSYS进行数值模拟分析,试验和有限元对照结果证明了采用有限元软件进行动力时程分析的可靠性。在此基础上,参考某Venlo温室工程结构设计,建立数值模型,按照规范对永久荷载、雪荷载和作物荷载进行组合,采用时程分析法,通过对温室结构单向输入AKT波、NGA波和人工波共3组地震波,分析其在8度半罕遇地震作用下的振型及有无地震作用下结构的内力、位移。结果表明,地震作用下Venlo温室结构的应力最大值为无地震作用下的1.24~2.12倍,其中人工波作用时的结构应力已超出材料屈服应力。同一组地震波作用时,将可变荷载考虑为作物荷载和雪荷载组合的b1工况与仅考虑作物荷载组合的b2工况分别施加于结构,所得柱顶位移数值相近,此时地震作用对柱顶位移起控制作用,柱顶位移最大值主要出现于外墙抗风柱。其次,人工波作用下结构柱顶产生的位移响应最大,最大值可达72.17 mm,已超过中国建筑抗震设计对弹性层间位移角小于1/250的要求。研究可为Venlo温室在地震作用下的安全设计提供理论参考。

       

      Abstract: Greenhouses have been widely used in facility agriculture at present. Gutter-connected greenhouses have been also extensively implemented to enhance the structural span for high land utilization with simplified mechanization. Among them, Venlo greenhouse has been the preferred choice among various forms of roof trusses, due to the simplified installation, superior light transmittance, and excellent sealing. The "National standard for the design of greenhouse structure " also released that "seismic action shall be calculated in the structural design of glass greenhouse for agricultural production in areas with seismic fortification intensity of 8 degrees (0.30g) and above". In this study, a regular-shaped Venlo-type greenhouse was designed to investigate the seismic performance and response using a shaking table test. A scaled-down model was then established with one span and two openings. The dynamic features of the modeled structure were analyzed to determine the acceleration response of the structure under the action of the 7-degree frequent, 7-degree fortification intensity, 7-degree rare, 8-degree rare, and 8-degree semi-rare earthquake. Numerical simulation was carried out in conjunction with finite element (FE) ANSYS software. The test and simulation were compared to verify the reliability of dynamic time-range analysis. In addition, the numerical model was established, according to the structural design of a Venlo greenhouse project. The time-history analysis was carried out under the action of 8 degrees and half rare earthquakes (the maximum acceleration time history was 0.51g). Meanwhile, the combination of permanent, snow, and crop load was selected, according to the specification. Three groups of seismic waves (namely AKT, NGA, and artificial wave) were input into the structure of the greenhouse. The mode of structure was analyzed to determine the internal force, vibration pattern and displacement with/without the action of the seismic waves. The results show that the maximum stresses in the overall structure of the greenhouse under seismic action were 1.24-2.12 times higher than those under no seismic action. The structural stresses during the action of artificial waves exceeded the yield strength of the material. Two cases (b1 and b2) were applied under the action of the same set of seismic waves. The b1 case was adopted to combine the live load with crop and snow loads, whereas, the b2 case combined the crop load only. There were similar values in the column top displacements. The seismic action dominated the column top displacements in these cases. The maximum displacements occurred in the outside wall storm columns. The largest displacement response was observed at the top of the structural columns under the action of artificial waves. The maximum of up to 72.17 mm exceeded the standard requirement of 1/250 of the elastic inter-story displacement angle for the seismic design of Chinese buildings. The research results can provide a theoretical reference for the safe design of Venlo greenhouse under seismic action.

       

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