Analysis of climate factors for the development of greenhouses in Eastern Blacksea Region

Eastern Blacksea Region is one of the less developed regions of Turkey in agriculture. That is why greenhouses are incited as an alternative income source for the region. In this study, aiming to evaluate the suitability of the climate conditions for greenhouses, heating and ventilation requirements for initially proposed two model greenhouses were calculated based on multi-years climate data. Climate parameters of region provinces were also evaluated and they were compared with climate characteristics of Samsun Province, where there were intensive greenhouse practices. As a result, it was determined that coastal provinces of the region had significant similarities with Samsun Province and they were more suitable than the inner provinces for greenhouse practices. Depending on the evaluations carried out, advantages and disadvantages of the region for greenhouse practices were determined and recommendations were made to regional producers.     

低层双齿大棚屋面风致积雪分布研究

为研究低层双齿大棚屋面的风致积雪分布规律,基于FLUENT软件中的Mixture多相流模型,建立了风雪两相流场模型。为验证风雪两相流场的准确性并选择合适的湍流模型,采用k-w,SST k-w和k-kl-w湍流模型分别对立方体周围积雪分布进行数值分析,并将数值分析结果与试验结果进行对比以验证数值方法的正确性,进而详细研究了风速、风向角、屋面坡度比和结构双齿长宽比对低层双齿大棚屋面风致积雪分布的影响。结果表明:风雪两相流模型和k-kl-w湍流模型建立的风雪两相流流场可以较好地反映低层双齿大棚屋面的积雪分布情况; 大棚屋面积雪厚度随着风速和屋面坡度比增大而减小,且屋面坡度比的影响程度较风速与风向角的影响小; 大棚屋面积雪受侵蚀和堆积区域位置随风向角变化而变化; 大棚结构长宽比对屋面积雪分布的影响较小; 低层三齿大棚屋面和低层四齿大棚屋面的屋面积雪分布系数可参考低层双齿大棚屋面; 提出的低层双齿大棚屋面积雪不均匀分布系数可为低层双齿大棚屋面的冬季防雪灾设计提供参考。     

Full-scale wind pressure measurements on a twin-span 12.2 × 12.2 m inflated roof greenhouse

In recent years plastic film has been extensively used for cladding low cost greenhouses. A limitation of the material is its susceptibility to wind storm damage and its wider use is dependent on good design through a knowledge of wind loads.Results of a limited programme of measurements of wind pressure on a film clad inflated roof greenhouse are presented. The measurements were made on the full-scale structure under natural wind conditions. The shape of the roof was modified by the wind and has been calculated for the measured wind load pattern assuming inviscid uniform flow. The application of these results to design is discussed.     

Energy saving in agricultural buildings through fan motor control by variable frequency drives

A comparison was conducted between ON–OFF and variable frequency drive (VFD) systems to control ventilation fans of greenhouses and poultry houses. The study aimed to determine the effect of each system on the energy consumption and resulting microclimate within the houses. The experiments were carried out in a commercial-size greenhouse in which pepper was grown and in commercial poultry houses. Reducing the fan speed with the VFD system resulted in reductions in the airflow rate through the houses and energy consumption, the latter being much more significant. The study showed that VFD control can reduce electricity consumption compared with ON–OFF operation. In the present study, the average energy consumption with the VFD control system was about 0.64 and 0.75 of that with an ON–OFF system in the greenhouse and poultry houses, respectively. The average greenhouse daily air temperatures and humidity ratios obtained with each control system between 07:00 and 18:00 were nearly equal. The results obtained in the greenhouse further showed that the VFD system has a greater potential than the ON–OFF, to reduce the range of amplitude variations in the air temperature and humidity ratio within the greenhouse. The average air temperatures over day and night, in the poultry houses, with each control system were nearly equal. The relative humidity, however, was slightly lower with VFD than with ON–OFF. Reductions in the range of amplitude variations of the air temperature and humidity were also observed in the poultry houses.     

Compressive strength characteristics of cement stabilized rammed earth walls

In order to minimize the environmental impacts caused by over exploitation of natural resources for the production of building material, the possibility of using cement stabilized rammed earth for load-bearing walls has been assessed. Since the vertical load carrying capacity primarily depends on the compressive strength, a comprehensive study was conducted for rammed earth walls constructed with three commonly available laterite soil types in Sri Lanka. The results indicate the possibility of using rammed earth for single storey houses which may also be extended to two storey houses. The load deformation characteristics were used to determine the suitable partial safety factors for the structural design.     

复采采场再生顶板结构及支架载荷确定

为确定复采采场支架的合理承载,通过理论计算、现场观测和顶板结构探测得到了复采再生顶板的结构分带特征,建立了再生顶板结构模型;基于该结构模型,结合现场观测和相似材料模拟实验,构建了下分层回采"支架–再生顶板"结构力学模型,应用该力学模型推导了支架载荷表达式,并进行了实例计算和现场验证。结果表明,再生顶板结构可分为"四带",即胶结再生带、弱胶结压实带、裂隙带和弯曲下沉带;再生顶板下回采下分层时,支架承载岩体可分为"两区",即完全承载区(A区)和部分承载区(B区);应用所推导的支架载荷表达式进行了实例计算,计算结果得到了现场支架载荷监测数据的验证。     

银川设施园艺产业园特色温室结构设计

温室结构属于农业设施,屋面一般采用玻璃或PC板,结构较轻,荷载取值与民用建筑结构有所不同。介绍银川产业园特色温室的结构设计,参考国内外相关规范考虑荷载取值,并对其在两种极限状态下进行计算分析。建议采用合理的影响系数并制订我国相应的温室设计标准。     

农业温室供热系统的研究与设计

研究中档温室围护结构形式与材料、供暖负荷计算和节能措施,提出适应温室的供暖系统及其供暖调控方式。     

Estimating shipping emissions in the region of the Sea of Marmara, Turkey

Ship emissions are significantly increasing globally and have remarkable impact on air quality on sea and land. These emissions contribute serious adverse health and environmental effects. Territorial waters, inland seas and ports are the regions most affected by ship emissions. As an inland sea the Sea of Marmara is an area that has too much ship traffic. Since the region of the Marmara is highly urbanized, emissions from ships affect human health and the overall environment. In this paper exhaust gas emissions from ships in the Sea of Marmara and the Turkish Straits are calculated by utilizing the data acquired in 2003. Main engine types, fuel types, operations types, navigation times and speeds of vessels are taken into consideration in the study. Total emissions from ships in the study area were estimated as 5,451,224 t y(-1) for CO(2), 111,039 t y(-1) for NO(x), 87,168 t y(-1) for SO(2), 20,281 t y(-1) for CO, 5801 t y(-1) for VOC, 4762 t y(-1) for PM. The shipping emissions in the region are equivalent to 11% of NO(x) 0.1% of CO and 0.12% of PM of the corresponding total emissions in Turkey. The shipping emissions in the area are 46% of NO(x), 25% of PM and 1.5% of CO of road traffic emissions in Turkey data between which and correspond to a higher level than aircraft emissions and rail emissions in Turkey.     

地下大跨度采场围岩突变失稳风险预测

提出了大跨度采场围岩突变失稳的两种形式 :构造控制型失稳和能量控制型失稳。对前者 ,提出了基于块体理论的可靠度分析理论和系统突变失稳预测方法 ;对后者 ,以突变论为理论依据 ,利用有限元分析与可靠度分析中的响应面方法相结合 ,建立了围岩突变失稳预测的可靠度分析方法。提出的预测方法应用于西石门铁矿采场失稳预测 ,获得较满意的结果     

水位对盾构隧道管片结构内力影响研究

当水位处于盾构隧道断面内时,管片侧向水平荷载分解为矩形荷载、满跨(跨高等于隧道直径)三角形荷载、非满跨三角形荷载3部分,已有修正惯用法对第三部分荷载只能作近似处理,导致计算结果有误差。首先针对此荷载做如下处理:理论推导管片在其作用下的内力弹性解和按面积等效原则将其荷载集度换算为对应满跨时荷载集度,并用于计算水平地基反力及其作用下的管片内力;然后利用推导公式并结合已有修正惯用法针对国内4种典型盾构隧道,分析了不同覆土条件下水位变化对管片内力的影响,得出其变化规律,可为盾构隧道结构设计提供借鉴。     

厚型板式结构转换层施工技术

在2m厚板的结构转换层施工中,重点解决了模板支撑系统、合理安排钢筋就位次序、水平施工缝处理、混凝土防裂等难题,采用“斜面分层布料、薄层浇注振捣、分层浇筑成型”的方法浇筑大体积混凝土,严格控制混凝土内外温差,使板式结构转换层支撑系统稳定可靠,温差控制效果及混凝土观感质量好,无结构性裂缝。     

温室结构设计中雪荷载取值方法的初探

在分析比较国外关于温室建筑及我国工业与民用建筑结构荷载规范的基础上 ,针对温室结构设计中雪荷载的定义方法、计算取值等进行了较深入的探讨 ;同时结合工程实践 ,提出了一套适合我国温室结构设计中雪荷载取值的一般原则 :在现有条件下 ,考虑重要性因子、暴露因子和热因子 ,按中国建筑结构荷载规范 (GB5 0 0 0 9- 2 0 0 1)计算雪荷载是可行的     

被动式太阳能温室中传热与气流分布的数值分析

建立了被动式太阳能温室系统的热平衡方程和土壤热、湿迁移过程的理论模型，针对武汉市11月份的典型气候条件，采用数值模拟和实验研究了温室中土温、气温的变化规律；分析了温室北墙内表面采用不同材料或涂层时，对温室中气流和温度分布的影响。     

圆弧钢拱破坏荷载的理论计算

拱结构经常在桥梁、屋顶等大跨结构中使用。尽管这些结构构件容易出现各种失稳现象,但其中短粗拱或细长拱的侧向水平连接失效是由塑性破坏而非平面内或平面外屈曲引起的。通过极限荷载方法分析塑性破坏荷载,以最大限度地发挥截面的塑性能力和出现塑性铰后的内力重分布能力。描述了竖向荷载下圆弧钢拱塑性破坏荷载的计算方法。使用塑性力学中的上限法、下限法和位移协调法来计算塑性破坏荷载,压力致使拱截面的容许塑性力矩减小。确定外荷载与容许塑性力矩之间的非线性关系后,使用迭代法得到塑性破坏荷载。利用有限元方法对分析结果进行检验,二者的分析结果相吻合。最后基于迭代法绘制设计图。     

大连极地海洋动物馆屋盖的结构选型及锯齿状锥面网壳的静、动力特性分析

介绍了大连极地海洋动物馆屋盖结构体系及结构选型依据。其屋盖结构根据建筑造型及功能要求选用了双层网架、单层筒壳、单层球面网壳及锯齿状锥面网壳等4种空间结构体系。重点介绍了锯齿状锥面网壳结构构成;并采用大型通用有限元软件ANSYS对锯齿状锥面网壳部分进行了静力分析及几何非线性稳定分析,得到了此类结构的应力分布、位移分布等静力特性及稳定性能;对结构进行了模态分析,获得了其自振频率、振型等自振特性,为后续对结构进行动力分析提供了基础。结果表明,该结构设计符合规范要求,稳定性良好,适于建筑造型呈锯齿状,屋面恒荷载较小的建筑物屋面。可为今后该类结构的设计提供一定理论依据。     

基于随机Pushdown方法的钢筋混凝土框架结构抗连续倒塌能力概率评估

为了评估钢筋混凝土框架结构的不确定性参数对其抗连续倒塌能力的影响,将确定性Pushdown分析与可以控制相关性的拉丁超立方体抽样方法（LHS）相结合,提出一种随机Pushdown方法。为说明方法的建立和应用,选择一栋8层4跨的钢筋混凝土框架结构,考虑结构的荷载、材料强度以及几何尺寸等17个不确定性参数,采用Pushdown方法分析获得的结构所能承受的最大竖向荷载作为其抗连续倒塌能力,统计得到结构连续倒塌易损性函数,并采用“龙卷风图”方法对不确定性参数的灵敏度进行了分析。结果表明,结构不确定性参数对抗连续倒塌能力影响显著,结构的抗连续倒塌能力的变异系数达到20%,其中,活荷载、楼层恒荷载、钢筋极限应力以及梁截面钢筋面积等参数对结构抗连续倒塌能力的影响最为显著。     

寒冷地区建筑负荷对围护结构热工参数的敏感性分析

为研究建筑围护结构属性对同一热工分区不同城市节能建筑负荷影响的敏感性,以同属于寒冷地区的兰州和郑州为研究目标所在城市,在节能65％的前提下将4种外墙、3种外窗和4种窗墙比进行组合得到了48个可能的办公建筑围护结构计算房间。分别计算了这些房间的冷负荷、热负荷和全年总负荷并分析了各热工参数对负荷的影响。通过与基准房间负荷对比,获得了具有不同热工性能的计算房间的节能率及最优的办公建筑围护结构。     

Comparative study on overall and local static performance of steel open-web girders

To quantify the mechanical properties of five types of steel open-web girders that have been tested or applied in practical engineering, a systematic study of the overall and local mechanical properties of steel open-web girders based on the same dimensions and material conditions was presented. An overall study of the quasi-intersection beam method for shear deformation was introduced for 8 × 8 grid open-web girders to derive the determinants of the load distribution factor. Based on the load distribution factors, the essence and formula of any shear key node domain (SKND) were derived theoretically. The reliability of the numerical model was verified by tests on the H-type unidirectional SKNDs, which led to a comparative load–displacement study of unidirectional and bidirectional SKNDs. Quantitative results of the overall flexural capacity and SKND load capacity of the H-type, TH-type, TS-type, T-type, and DT-type open-web girders were obtained. The maximum shear deformation in the elastic phase of the five open-web girders accounted for 39.04% to 54.76% of the overall deformation. In this study, the adjustment factors of the modeling analysis based on the current practical design of equivalent dense-ribbed solid beams (DRSBs) were revised. A method of SKND's design load capacity under the action of bidirectional forces was put forward for the first time.     

梁柱节点的单元模型校准与其组合体试验方法对比

梁柱节点是钢筋混凝土结构中受力性能复杂的重要部位,其有限元模型的合理性是结构非线性数值模拟成功实施的关键。在OpenSees结构分析平台上,以力学模型较为细化的梁柱节点单元(beam-column joint element)模型为研究对象,在合理确定梁柱节点单元各分量的参数取值方法的基础上,分别以多组钢筋混凝土梁柱组合体试件的梁端加载、柱端加载试验结果为依据,对有限元模拟结果的准确性进行校准,并在此基础上分析了同一组合体试件分别采用梁端加载、柱端加载两种试验方法时模拟结果的差别。结果表明：梁柱节点单元中模拟节点内纵筋滑移分量的材料模型存在较明显误差,当滑移较小时,模拟结果有相对较好的精度;当梁纵筋滑移量较大时,模拟的组合体整体滞回性能与试验结果相比误差较大;当梁、柱纵筋黏结滑移值较小时,同一组合体试件在梁端加载、柱端加载两种试验方法下的节点非弹性变形相近。