Bedding effects in bulk solids in silos: experiments and a polar hypoplastic approach

This paper is concerned with bedding effects in granular bulk solids in silos. Finite element (FE)-analyses were performed for a cylindrical thin-walled steel model silo with imperfections containing dry sand. Numerical calculations were carried out for an axisymmetric case with a polar hypoplastic constitutive relation which can capture the salient properties of granular materials. In the FE-calculations, different types of wall displacements along the silo height were taken into account to model roughly the formation of buckles due to initial imperfections of the silo wall. The effects of the initial void ratio and mean grain diameter of bulk solids, initial stress state, wall roughness, and size and form of buckles were studied. The numerical results clearly show that the modelling of a bedding effect of bulk solids in silos by means of springs is too simple and can lead to strongly unrealistic predictions of the bedding modulus.     

运行工况对筒仓动态侧压力的影响

用离散元程序(PFC2D)研究了筒仓卸料过程中贮料颗粒的流型、力场以及仓壁侧压力的变化,通过数值模拟对其分别进行了分析,得出筒仓运行工况对卸料动态侧压力的影响比较大的结论.     

Steel silos with different aspect ratios: II — behaviour under eccentric discharge

The phenomenon of eccentric discharge is widely recognised as the most dangerous condition for thin-walled metal silos and the cause of many catastrophic buckling failures. A realistic pressure model for this condition appears in a regulating standard for the first time in EN 1991-4 (2006) on Actions on Silos and Tanks. However the structural consequences of its application are currently largely unknown. The behaviour of a silo subjected to these pressures is certainly very dependent on the aspect ratio of the silo, the granular solid properties and the discharge channel geometry.This paper explores the behaviour of four thin-walled cylindrical silos with stepwise-varying wall thickness and aspect ratios varying from intermediate to very slender, subject to the codified EN 1991-4 eccentric discharge pressures. It is shown that a silo design that was found to be very safe under the EN 1991-4 concentric discharge pressures becomes very unsafe under eccentric discharge. Further, as it is known that the aspect ratio has an important effect on the flow pattern in discharging granular solids, and that slender silos exhibit very different flow patterns from squat silos, it is currently not certain whether a suitable range of aspect ratio over which the codified eccentric discharge model is to be applied has been prescribed in the standard.This paper is the second of a pair. In the first, the behaviour of a set of example silos under the EN 1991-4 concentric discharge condition was studied. The same example silos are studied here under eccentric discharge.     

Dynamic FE simulations of buckling process in thin-walled cylindrical metal silos

The buckling of cylindrical steel silos is caused by the wall friction force due to shearing between the silo fill and silo wall. The aim of this paper is to investigate the stability process in a silo composed of thin-walled isotropic plain rolled sheets using a static and dynamic finite element analysis by taking both the geometric and material non-linearity into account during eccentric discharge. Silo shells were subjected to axisymmetric and non-axisymmetric loads imposed by a bulk solid following Eurocode 1. The differences between the results of static and dynamic analyses were comprehensively discussed. The advantages of a dynamic approach were outlined.     

大型筒仓结构与地基的动力相互作用研究

本以某大型筒仓结构为例，考虑到散粒体-结构-地基的相互作用，利用部分集中质量-筒仓耦合相互作用法，对弹性地基上的筒仓结构（包括单体筒仓和筒仓群或排仓）进行了多种工况、系统的有限无动力分析计算。经与刚性地基上的筒仓动力响应的比较，得出以下结论：在对地基施以相同的水平激励时，弹性地基上筒仓的动力响应大于刚性地基上筒仓的动力响应；刚性地基上群仓的动力响应大于单体仓的动力响应；弹性地基上单体仓的动力响应大于群仓的动力响应。     

某带隔板联体钢筋混凝土筒仓裂缝成因分析

某联体筒仓由三仓组成,中仓带隔板,在使用期间仓壁出现多条明显裂缝。本文通过对该联体排仓进行有限元模拟计算,对不同工况的贮料荷载引起仓壁和隔板的应力变化进行了分析,将计算裂缝宽度和配筋与实际情况进行了对比,给出了仓壁裂缝的形成原因和技术说明。     

钢筋混凝土筒仓侧压力的计算与测试

讨论了钢筋混凝土筒仓仓壁的基本压力及动态压力的确定问题。考虑到筒仓卸料时，仓体内的应力状态及侧压力系数随深度变化的实际情况，建立并求解了微分方程，得出仓壁的动态压力的实用计算公式，并进行相应的筒仓模型试验，测试值与理论计算值基本上相吻合。为钢筋混凝土筒仓的设计和筒仓规范修订提供了理论依据和可靠试验数据。     

平底圆形钢筒仓稳定性设计-储料荷载

本文介绍了国外五套钢筒仓荷载规范^[1-5]，并与我国新出版的《粮食钢板筒仓设计规范》^[6]进行了比较．比较结果表明，我国规范只考虑中心装料和中心卸料时荷载的轴对称部分而忽略非轴对称分布对结构行为的影响．对轴对称荷载，我国规范中的竖向摩擦力明显比国外同类规范小，而水平压力修正系数却比国外同类规范大．对常见筒仓(H／D=2，D=20米)和常见储料(小麦)，仓底竖向摩擦力为国外同类规范值的48％～85％；水平压力修正系数却比国外同类规范大33％～54％．因此，我国《粮食钢板筒仓设计规范》在设计出更加经济钢筒仓的同时，也隐含着不安全的因素．本文的结果可为今后编制和修订同类筒仓设计规范提供参考．     

不同仓底支撑结构形式对大直径筒仓内力的影响研究

对于大直径筒仓,其仓底结构可分为仓底板与仓壁连接在一起和仓底板与仓壁脱开两种形式。本文针对这两种不同的仓底结构形式对筒仓仓壁的应力进行了有限元分析,并对有限元分析结果与传统的无矩理论计算结果进行了比较,表明：不同的仓底结构形式对仓壁的应力影响很大；有限元分析结果比传统的无矩理论计算结果更接近于工程实际情况。     

巨型贮煤筒仓在环境温度作用下的有限元分析

本文对一直径120m、容量达10万t的巨型钢筋混凝土贮煤筒仓在环境温度作用下进行有限元分析,分别研究了在空仓和满仓时,环境温度升高和降低时仓壁的应力状态,并与贮煤侧压力作用时的应力状态进行比较分析.分析结果表明,环境温度降低时,仓壁中的最大环向应力比由贮料侧压力所引起的仓壁最大环向应力约大6倍;降温时仓壁最大环向应力是升温时的仓壁中的环向应力的7倍;环境温度作用所引起的仓壁竖向应力与由贮料侧压力所引起的仓壁竖向应力差别不太大.最后分析了《钢筋混凝土筒仓设计规范》(GB 50077-2003)中的有关规定,提出了几点设计参考意见,可给类似工程设计提供参考.     

巴基斯坦某水泥筒仓项目滑模施工技术要点

巴基斯坦某堆场项目包含单仓和多仓两种结构的筒仓,其主体结构采用滑模施工。本文叙述了单仓和多仓两种结构筒仓的滑模施工技术要点和经验总结,为其它筒仓项目的施工提供参考。     

带仓顶室筒承式群仓自振特性的实验研究

通过21个有机玻璃试件对带仓顶室简承式群仓的自振特性进行了试验研究,探讨了组合简数、支承筒开洞方向、仓顶室抗侧刚度、贮料量不同时前2阶自振频率及振型的变化规律．试验表明：组合筒数增加,自振频率提高;贮料量增加,自振频率降低;仓顶室刚度变化对贮料满仓时的第一阶段自振频率及振型影响较小,但对第二自振频率影响较大;开洞方向与仓联结方向相同或垂直时,对白振频率及振型均有影响．     

环向加劲钢筒仓在均匀内压作用下仓壁等效厚度研究

加劲肋通常作为增强筒仓仓壁强度和稳定性的措施,但目前对于如何确定筒仓加劲肋间距及尺寸的设计方法尚不明确。合理设置加劲肋,能起到提高筒仓强度承载力的作用,相当于增加了仓壁厚度。本文用数值方法研究了设置环向加劲肋的钢筒仓在均匀内压作用下的应力分布规律,提出环向加劲肋有效间距的概念,通过参数分析研究了加劲肋尺寸和筒仓几何特征对环向加劲肋有效间距的影响,提出有效间距的实用计算公式。在有效间距公式的基础上,推导出了更准确的均匀内压作用下环向加劲钢筒仓的仓壁等效厚度公式,对《粮食钢板筒仓设计规范》(GB50322-2011)中仓壁折算厚度的计算方法提出修正意见。     

A simplified analytical procedure for assessing the worst patch load location on circular steel silos with corrugated walls

Silos are widely used in the food and chemical industries for the storage of granular materials. The calculation of their wall dimensions is complicated since the interaction between the stored material and that from which the silo is made is complex, a consequence of their very different mechanical behaviours. The loads exerted on the silo walls by stored materials must be taken into account in silo design, and the means for calculating them is contemplated in Eurocode EN 1991-4. The complexity of the phenomena that occur within silos often leads to the appearance of unexpected and asymmetrically distributed pressures. This is taken into account in the above Eurocode via the concept of the patch load, which is asymmetric and can be exerted at any point on the silo wall. A finite element model has been developed in order to check that the stress resultants derived from the patch load on steel silos with corrugated walls may be predicted by using the well-known expressions of shell theory. Then, a simplified analytical procedure has been developed for predicting the worst location of patch loads for all metal silos, but with special application to corrugated steel silos in Action Assessment Class 3. It has been found that significant differences may be found for most cases with the worst location for the patch load defined in Eurocode for welded silos in Action Assessment Class 2. On the other hand, the values obtained for the maximum meridional membrane stress resultant do not significantly differ, except for high slenderness values in intermediate slenderness silos.     

钢筋混凝土筒仓仓壁侧压力的研究

本文讨论钢筋混凝土筒仓仓壁的基本压力及卸料时由于整体流动引起仓壁的动态压力的计算问题。考虑到筒仓卸料时，侧压力系数随仓体深度变化这一实际情况，建立了微分方程，得出仓壁的动态压力的计算公式。并进行了数值计算，其结果与模型筒仓试验测得的侧压力数值相接近。     

Finite element analysis under different boundary conditions of the filling of cylindrical steel silos having an eccentric hopper

A three-dimensional finite element analysis was made of the filling of cylindrical silos having an eccentric hopper, using different boundary conditions—silos supported at the transition or on discrete columns. The analysis included the options of the presence or absence of reinforcement in the transition and walls. The results for the pressures on the wall for a flexible wall and all the boundary conditions were compared with those for a silo with a rigid wall. The membrane stresses and meridional and circumferential bending moments were then evaluated in the silo wall and in the reinforcing elements. Lastly, the influence of the eccentricity of the hopper in a silo of intermediate eccentricity was analysed, and conclusions were drawn for the optimal design of these structures.     

氧化铝钢筒仓的地震谱分析

筒仓结构在抗震设计方面不够完善,利用ANSYS软件建立模型对筒仓进行谱分析,并分三种模式进行分析,得出筒仓的力学反应结果。     

超大型固废筒仓结构设计探讨及应用

超大型固废筒仓的设计和制作在引入公路加筋土设计理念后可以做到构造非常简单和廉价,可广泛应用于各种固废治理和生物质能源利用领域。本文将对该筒仓体的结构强度和刚度进行受力分析,并提出确保筒仓体结构安全的解决方案。     

考虑内压影响的薄壁钢板筒仓屈曲承载力研究

一定程度的内压会降低薄壁钢板筒仓对缺陷的敏感性,提高其弹性屈曲承载力;但内压过高时,筒仓会出现弹塑性强度破坏或弹塑性屈曲破坏,其承载力反而降低。我国现有《粮食钢板筒仓设计规范》（GB50322-2011）给出了考虑内压影响的屈曲承载力计算公式,但该公式只适用于计算内压较低时筒仓的弹性屈曲应力,对高内压下筒仓弹塑性破坏时采用该公式将得到不安全的结果。采用有限元方法对轴压和水平内压作用下有初始缺陷的筒仓进行了参数分析,分别讨论了内压大小、材料强度和径厚比等对筒仓屈曲应力的影响,提出了筒仓在轴压和均匀内压作用下的弹性屈曲应力和弹塑性屈曲应力计算公式,并对《粮食钢板筒仓设计规范》公式进行了修正。经验证,该计算公式与有限元分析结果基本吻合。