装配式落地波纹钢板筒仓在粮食荷载作用下的稳定性分析

装配式落地波纹钢板筒仓的仓壁为波纹钢板,故其结构性能属带肋各向异性壳,其稳定性能被筒仓工程界所关心.我国《粮食钢板筒仓设计规范》(GB 50322-2011)基于各向同性圆柱壳假定而得到的钢板筒仓稳定性计算公式,实际上不能真实反应屈曲承载能力.本文采用ABAQUS程序,结合筒仓算例,建立了包括波纹仓壁板和竖向加劲肋的筒仓模型,进行了粮食荷载作用下的线弹性屈曲分析和几何、材料双重非线性分析,得到屈曲承载能力,并与规范公式进行了比较.结果表明竖向加劲肋屈曲与否决定了装配式波纹钢板筒仓的稳定,规范关于筒仓稳定性的计算公式欠准确.     

钢筒仓地震作用计算方法研究与分析

介绍美国、欧洲和我国钢筒仓设计规范对钢筒仓地震作用计算方法,并采用3本规范进行实例计算并相互比较。计算结果表明:我国规范计算结果偏于保守,我国规范与美国规范计算仓壁应力计算最大差异为15%~43%,位移差异为:11%~43%,按我国规范与美国规范计算钢筒仓加强筋应力最大差异为:10%~24%,位移差异11%~41%。我国GB 50322-2001《粮食钢板筒仓设计规范》正在修订中,本结果可为正在修订的设计规范提供参考。     

粮食钢板筒仓整体稳定设计综述

本文结合钢板筒仓稳定性研究的基础资料和我国<粮食钢板筒仓设计规范>(GB50322-2001)中筒仓整体稳定设计规定,针对我国粮食钢板筒仓结构特点,对粮食钢板筒仓稳定设计计算中粮食荷载计算、仓壁折算厚度、计算参数取值等有关内容及方法进行了分析说明,并提出了需进一步研究的相关问题.     

轴压和均匀内压下钢筒仓圆柱壳屈曲承载力研究

我国的《粮食钢板筒仓设计规范》对仓壁的稳定承载力计算方面的相关规定并不完善。本文以钢筒仓仓壁的圆柱壳体为研究对象,引入了四种常见的初始缺陷模式,对轴压和均匀内压下钢筒仓仓壁的弹性和弹塑性屈曲承载力进行了深入的参数化有限元分析,研究了各种缺陷模式对仓壁壳体屈曲承载力的影响,以及均匀内压对仓壁弹塑性屈曲承载力的提高程度。在有限元分析结果的基础上,结合中国规范的相关公式,拟合出轴压和均匀内压下钢筒仓仓壁的弹塑性屈曲承载力的计算公式。     

轴压和不均匀内压下钢筒仓圆柱壳屈曲承载力研究

我国的《粮食钢板筒仓设计规范》(GB50322-2001)对仓壁的稳定承载力计算方面的相关规定并不完善。本文以钢筒仓仓壁的圆柱壳体为研究对象,引入了四种常见的初始缺陷模式,对轴压和不均匀内压下钢筒仓仓壁的弹性和弹塑性屈曲承载力进行了参数化有限元分析,研究了各种缺陷模式及非均匀内压分布形式对仓壁壳体屈曲承载力的影响。在有限元分析结果的基础上,结合中国规范的相关公式,拟合出轴压和非均匀内压下钢筒仓仓壁的弹性及弹塑性屈曲承载力的计算公式。     

基于三维数值仿真分析竖向荷载对水平承载力的影响

随着我国近年来大跨径桥梁及高层建筑的迅速发展,基桩的承载能力及桩长日益增大,竖向、横向组合荷载(倾斜荷载)作用下基桩的受力分析和设计理论已成为目前土木工程界急待解决的重要问题之一。针对我国现行规范将桩顶倾斜荷载分解为竖向和水平荷载分别计算,进行单方向荷载下的承载力、强度、构造计算、校核存在的不足。采用PLAXIS 3D FOUNDATION对竖向荷载作用下,非扩底桩和扩底桩的水平承载力进行三维数值仿真分析,提出了对规范进行修正的建议。     

筒仓卸料的颗粒流模拟及仓壁侧压力研究

钢筒仓在偏心卸料的情况下,仓壁易发生屈曲破坏,我国《粮食钢板筒仓设计规范》中仅规定了静态储料对仓壁侧压力的计算方法,而缺少偏心卸料的相关规定。本文采用颗粒流程序PFC2D和PFC3D,对偏心卸料情况下储料对仓壁侧压力的分布进行了参数化分析,结合颗粒流程序的结果和若干假定,得到了偏心卸料情况下储料对仓壁侧压力的分布形式。     

大直径直线钢顶管管周受力特性数值模拟研究

钢顶管作为薄壁结构，受力时与土体变形协调，故现有规范在计算钢顶管土压力时存在缺陷。通过ABAQUS有限元软件分析了不同参数设置下钢顶管土压力和摩阻力的数值大小与分布情况，并提出钢顶管侧向土压力的修正系数。模拟结果表明：DN2000钢顶管在113 kPa的竖向土压力作用下，水平向变形可达管径7‰，产生水平土体附加抗力；钢顶管土压力值与管道径厚比、埋深比呈显著正相关，土体变形模量的增大限制了管侧土压力的增加；侧向土压力系数随管侧变形呈指数增长；单位长度管壁摩阻力随径厚比和埋深的增加而上升，而管侧土变形模量对摩阻力的影响几乎不计。     

风力发电钢塔简的荷载计算方法和荷载组合研究

目前我国相关规范和规程尚没有对风力发电钢塔筒给出具体的荷载计算方法。本文分析研究了风力发电塔筒的荷载作用特点,总结了风力发电钢塔筒的荷载计算方法和荷载组合。对水平气动荷载公式进行了修正,并提出了修正系数0．4。通过对某MW级风力发电塔筒的力学性能进行有限元分析,提出了塔筒设计时可变荷载中的第一可变荷载和最不利工况。     

新旧荷载规范关于风振系数表达形式的比较研究

采用随机振动理论建立新、旧两种荷载规范中风振系数表达式之间的内在联系，指出新规范计算风振系数的参数与旧规范中的脉动增大系数、脉动影响系数、位置函数的关系；建立新规范的背景分量因子Bz的具体表达式，可适用于各质点质量、受风面积、阻力系数及振型值任意变化的情况；指出新规范计算风振系数时将用10 m高处的紊流度代替旧规范的脉动系数。数值算例表明，新规范的风振系数比旧规范的有所提高，这种提高主要来自于新规范中峰值因子与紊流度取值的提高；新规范与旧规范相比，由等效静力风荷载引起的结构基底剪力，除了D类地貌的有所减小外，其它3种地貌的基底剪力都有所增大。     

钢板筒仓结构稳定承载力研究现状

文章主要总结目前钢板筒仓结构稳定承载力的研究现状。首先介绍了轴压圆柱壳的弹性经典解,然后总结了筒仓初始缺陷敏感性的研究工作成果,最后对中、欧现行规范中筒仓稳定承载力计算方法进行比较,研究结果对筒仓工程设计与理论分析提供参考。     

冷弯薄壁型钢组合墙体受剪性能研究综述

根据对冷弯薄壁型钢结构体系传力路径的分析,承受和传递水平、竖向荷载的组合墙体的受力性能对整个结构的抗震性能至关重要。按照从局部到整体的顺序,依次对国内外开展的墙体龙骨、墙面板连接件和组合墙体的抗震性能的研究进行综述。结合对国内外具有代表性的剪力墙受剪试验结果进行的统计分析,分别给出墙面板、墙面板连接件、钢龙骨框架、墙体高宽比、墙体开洞及加载类型对墙体受剪承载力的影响。部分墙体受剪试验结果与中国规范相应的设计参考值进行对比,指出按线性内插得到的由大间距连接件连接的墙体受剪承载力规范参考值趋保守。按照中国规范给出的抗力分项系数值进行可靠度计算,计算结果表明规范的设计参考值不能很好的符合目标可靠度为3.2的要求。按文献建议调整抗力分项系数后的计算结果与目标可靠度吻合良好,但应进行更多的研究寻求合理的抗力分项系数值。最后对该类结构体系抗震性能研究领域需要深入研究的问题提出了建议。     

Field measurement data of wind loads on rainscreen walls

Rainscreen wall design is still at its infancy stage even after its introduction about four decades ago. Research continues in an effort to set out appropriate design guidelines for rainscreen walls. This paper presents the key results of yearlong full-scale measurements of wind loading on rainscreen walls. The objective of this study is to estimate the impact of various design parameters on the wind loading on rainscreen. This paper also presents the current status of the available codes and standards regarding the wind loads on rainscreen walls and compares the full-scale results with some available provisions.     

中外荷载规范雪荷载取值及控制影响因素对比分析

基于对当今中外荷载规范雪荷载章节的梳理，以雪荷载对应取值及控制因素的差异为视角进行了深入的对比剖析，得出各国规范体系构架存在较高相似性，均采用由地面雪荷载（基本雪压）乘上一系列用以量化计算的控制因素系数而获得屋面雪荷载值，而屋面雪荷载按作用效应又可划分为基本雪荷载、漂移雪荷载与滑落雪荷载三类，且各类别在不同规范中取值具有差别。由此建议在中国新版建筑荷载规范雪荷载章节继承完善基本雪荷载和漂移雪荷载，并补充对屋面滑落雪荷载取值规定。另外，总结了各国规范中雪荷载控制影响因素，可归为外界环境与建筑本身两大类，并依据国外规范对控制因素的考虑权重，选取影响较大且我国规范尚未考虑的因素进行详细探讨。由此建议引入考虑降雨量与坡屋顶特性的雨雪联合因素，考虑宏观地貌气候与周围环境的建筑暴露状态因素，考虑室内采暖温度与屋面热阻的建筑采暖因素及考虑屋面光滑程度的屋面材料因素，以达到优化规范体系构架的目的。     

受静载和循环荷载作用的基础下加筋挡墙工作性能分析

 基于受静载和循环荷载作用的基础下加筋挡墙模型试验,综合对比分析了基础位置、荷载大小、频率和循环次数等因素对加筋挡墙力学与变形性能的影响。试验结果表明：(1) 以基础极限承载力为标准,确定基础最佳偏移距离为0.3H(墙高);(2) 基础沉降和挡墙水平位移随荷载、频率和循环次数的增加而增加,当基础受静载且达到极限承载力前,沉降与墙高比均小于2%,挡墙水平位移与墙高比均小于1%;当基础受循环荷载时,增加循环荷载水平和频率使初始阶段基础沉降和挡墙水平位移增加明显,但随循环次数增加而变形收敛;(3) 紧邻基础下方的筋材应变显著高于其他层,且循环荷载水平越高,循环次数增多时筋材应变增幅显著;(4) 静载时挡墙破坏随基础偏移距离增加而由初始顶层面板被挤出,逐渐过渡到破坏面沿基础边缘并向挡墙深部发展的剪切破坏为主;当基础受循环荷载且频率较小时,顶层面板以挤出变形为主,增加荷载水平和频率,挡墙以中部面板挤出破坏为主。     

Steel silos with different aspect ratios: I — Behaviour under concentric discharge

The current European standards for the design of thin-walled metal silos require the designer to use a complex combination of rules covering many different aspects of loading, structural behaviour and strength. Each individual rule was often developed autonomously, usually with implicit and undocumented conservative assumptions. When combined, the overall factor of safety of a designed silo may be significantly different from that guaranteed by the standard, making it difficult to reproduce the design rules in a numerical calculation that does not include the same implicit assumptions.This paper explores the behaviour of five thin-walled cylindrical silos with stepwise-varying wall thickness and aspect ratios varying from very squat to very slender, all custom-designed for and analysed under the EN 1991-4 concentric discharge loading condition. The aspect ratio plays a deciding role in both the behaviour and design of silos, and it is important to ascertain that a finding that is valid for one is transferable to the others. The nonlinear finite element analyses reveal that the computed load factor exceeds the partial safety factor in design by a large factor over a wide range of aspect ratio, suggesting that the overall design process is particularly conservative. The reasons for these discrepancies are explored.This paper is the first of a pair. The second paper explores the behaviour of the same set of example silos under the EN 1991-4 eccentric discharge loads, with fundamentally different conclusions.     

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.     

大直径浅圆仓侧压力计算的总体平衡法

采用总体平衡方法给出了一个新的大直径浅圆仓散体静态侧压力计算公式,该公式计算简单,并可用于储料顶部为平顶和锥顶两种情况。本文公式的计算结果经与实仓测试结果、国家规范和库仑公式对比分析表明,本文公式的计算结果与实仓测试结果吻合良好,本文公式的计算精度和吻合趋势好于国家规范和库仑公式。     

Statistical inference of unsymmetrical silo pressures from comprehensive wall strain measurements

A thin cylindrical shell structure which is subjected to local or unsymmetrical loading often displays a very complex pattern of response, involving multiple alternative potential failure conditions in different parts of the structure. The loading may therefore need to be defined with great precision. In the field of silo structures, it is widely recognised that such local loads often exist, but experimental observations of the patterns of load are very difficult to obtain because of the expense of instrumentation and the need to use full-scale testing to avoid granular solid scale errors.This paper presents a newly developed technique which permits these local unsymmetrical load patterns to be determined in a much more cost-effective way. In addition, because the loading is deduced from the structural response, the method has an inherent robustness in that when the deduced loadings are generalised and used to predict a structural response, it is more likely to be close to the real response. The same cannot be said for loading patterns deduced from single discrete observations of loading with imaginative interpolations between them, which form the basis of most current design rules.The paper describes a rigorous procedure for inferring the complete pressure distribution from a large body of strain observations on the silo wall. The method is outlined and a simple practical example, involving unsymmetrical loads, is used to explore the effect of observation errors on the inferred pressures. A sample set of pressures in a specially built full-scale test silo under eccentric solids discharge is also derived.