初始几何缺陷对仓壁柱承钢筒仓稳定性能的影响

仓筒壁直接支承于支柱是小型钢筒仓的一种简单、经济的支承方式。薄壳结构通常对初始几何缺陷十分敏感。引入周向轴对称焊缝凹陷和特征值屈曲模态两种缺陷形式,通过几何非线性分析,研究初始缺陷对轴压下仓壁柱承筒仓稳定性能的影响。研究表明,周向焊缝凹陷会显著降低结构的屈曲荷载,且与焊缝位置密切相关,而特征值模态缺陷只有在支柱接近仓顶时才会显著影响其屈曲强度。     

风荷载作用下柱支承钢筒仓的受力性能

利用数值方法研究在风荷载作用下柱支承钢筒仓中圆柱壳的结构行为。首先总结作用于圆柱壳的周向风压分布,然后通过线性应力分析及几何非线性分析研究柱支承圆柱壳的受力性能特别是其稳定性,着重分析支承宽度的影响,最后探讨柱承圆柱壳的初始缺陷敏感性。     

带仓顶室简承式筒仓的自振周期及地震作用计算

通过对筒承式筒仓的计算分析,带仓顶室筒承式筒仓的整体自振基本周期比筒仓主体的自振基本周期及仓顶室固定在地面的自振基本周期的大值要略大。采用基底剪力法计算筒仓水平地震作用时,计算仓顶室水平地震作用可采用筒仓的整体自振基本周期,其水平地震作用效应的增大系数一般取4.0,取振型指数大于1.0时,增大系数可取3.0;计算支承筒的水平地震作用应采用筒仓主体的自振基本周期。     

钢筋砼筒仓侧压力作用内力分析

钢筋砼筒仓在物料侧压力作用下，仓壁的的一般工程设计计算，采用的是一种简化方法，这种方法忽略了仓壁沿高度方向的连续性，仓壁上部以及仓壁下部没有承受水平压应力一段筒仓壁段以及筒体的顶板和底板的约束影响。本文应用ＳＡＰ结构分析软件，以工程中常见钢筋砼筒仓为算例，进行有了元分析计算。     

悬挂式钢板筒仓摩擦力计算

悬挂式钢板筒仓是一种新型结构，解决了仓壁支承式钢板筒仓仓壁竖向受压失稳不能充分利用钢板强度的问题。本文利用平衡方程法和求导法给出了悬挂式钢板筒仓总竖向摩擦力计算公式，为该新型结构的进一步研究应用奠定了理论基础。     

基于有限元法的蜂窝夹层结构稳定性研究

蜂窝夹层结构随面板厚度的逐渐变化会出现不同的屈曲现象。针对连续芯层有限元模型, 求出不同面板厚度时结构的屈曲因子, 并与经验失稳公式预测值进行对比, 两种方法的结果基本吻合。建立考虑芯层几何特征的有限元模型, 进行屈曲分析并研究芯层几何参数对结构稳定性的影响。介绍了一种局部屈曲现象——蜂窝壁屈曲, 提出了相应的失稳预测分析方法, 并与三维有限元分析结果进行比较, 验证该方法的正确性。对承受多轴惯性载荷的蜂窝夹层承力筒结构进行稳定性分析, 通过改变面板厚度和纵横惯性载荷比, 得到一系列有限元解, 给出了相关的多轴惯性载荷相关方程。     

轴心受压梭形变截面钢管格构柱的弹性屈曲性能

梭形钢管格构柱是由若干钢管分肢以及许多横向缀管组成的变截面轴心受压构件,良好的力学特性和优美的建筑造型使其广泛应用于索膜结构、大跨度空间结构及高层结构的支承体系,它是近年来出现的一种新型的结构构件。利用有限元软件ANSYS分析了梭形三肢钢管格构柱的几何参数对其弹性屈曲荷载和屈曲模态的影响。这些几何参数包括:柱长、整体长细比、分肢钢管几何尺寸(外径和壁厚)、横向缀管几何尺寸(外径和壁厚)、横向缀管数量(或分肢长细比)等。分析结果表明,梭形格构柱在不同的结构参数下的屈曲荷载和屈曲模态与等截面柱有很大的不同,其中“S”形的屈曲模态反映了这种构件新的屈曲性能。     

轴压作用下矩形开口圆柱壳的稳定性

利用数值方法系统研究带矩形开口的薄壁圆柱壳的稳定性能．对矩形开口的周向角度、高度、轴向位置、开口数量等几何参数进行比较分析,并考察两类几何初始缺陷对结构稳定性的影响．分析表明,影响矩形开口圆柱壳轴压下稳定性的主要因素是周向开口角度,屈曲荷载随开口角度的增大而线性下降,而开口高度及开口的轴向位置对屈曲荷载的影响很小．此外,矩形开口圆柱壳对以特征值屈曲模态分布的初始缺陷并不敏感,但对周向轴对称凹陷十分敏感．     

贮仓—地基相互作用一筒仑模型的静力实验研究

本文作者设计制作了有机玻璃筒仓模型，在空仓及装填了散料（大米）的满仓两种情况下，将筒仓分别置于生地基和用海绵橡胶垫模拟的弹性地基上，实测料仓仓壁及支承筒的静力应变值，并与有限元结果进行了比较，两者能够很好的吻合，证明了实验是成功的，所用的力学计算模式及模型分析的简化是正确的。     

初始缺陷对耐压结构承载性能影响

目的基于有限元方法,通过分析研究深海耐压圆筒结构在不同初始缺陷下的屈曲压力,研究初始缺陷对厚壁圆筒承载极限的影响。方法建立了三维厚壁筒模型,分别研究了圆筒在初始几何缺陷、初始应力缺陷和两种缺陷复合的状态下,结构的承载性能,并将得到的结果与理想状态下的结构作对比。结论结果表明,无论是初始几何缺陷,还是初始应力缺陷,都会降低结构的承载极限。     

Application of linear buckling sensitivity analysis to economic design of cylindrical steel silos composed of corrugated sheets and columns

The paper deals with global stability of steel cylindrical silos composed of corrugated walls and vertical columns with loads imposed by a bulk solid following Eurocode 1. The optimum silo design with respect to the steel weight was based on a sensitivity analysis method. The changes of silo column profiles at each design step were performed by means of influence lines for the buckling load factor due to the unit column bending stiffness variation. The corrugated walls were simulated as an equivalent orthotropic shell and vertical thin-walled columns as beam elements. The results were compared with the Eurocode 3 approach and verified by FE results of linear buckling and non-linear analyses with geometric non-linearity carried out with the commercial finite element code ABAQUS for a 3D shell model of a perfect silo. The proposed procedure allowed for a rational silo design with an economic material use. Some recommendations for the silo optimum design were elaborated.     

Failure analysis of steel silos subject to wind load

Steel constructed are made of thin-walled cylindrical shells. They are widely used in various food and agriculture industries for storing granular solids, liquids, and bulk food. The present research study was completed to determine the structural behavior of thin-walled silo when subjected to wind load. The study included determination of deformational behavior of a large field silo and development of a finite element model. This experimental part of the study comprises a challenging full-scale test on 14.55 m diameter and 23.27 m high steel silo located in the open farm land near Bothwell in the province of Ontario, Canada. The finite element model was then developed for undertaking wind analysis to study the effect of different parameters such as different geometric dimensions, stiffener patterns, and wind girders on the wind-induced buckling strength of steel silos made of corrugated steel. Both linear and geometrically nonlinear buckling analyses were carried out to determine the critical wind speed for corrugated steel silos. The study found that the wind girders, also known as wind rings, significantly increase the buckling strength of the silo. This study found that the critical buckling wind speeds of the field silo specimen have increased by about 44%. Further, the optimum location for the addition of wind rings was found to be near the roof of the silo.     

Failure of cylindrical steel silos composed of corrugated sheets and columns and repair methods using a sensitivity analysis

The paper deals with failure of large cylindrical steel silos composed of horizontally corrugated sheets with vertical stiffeners. The failure reasons were discussed. A linear buckling and a non-linear analysis with geometric and material non-linearity were carried out with a perfect and an imperfect silo shell (with different initial geometric imperfections) by taking into account axisymmetric and non-axisymmetric loads imposed by a bulk solid following Eurocode 1. The 3D FE calculations were carried out with the commercial finite element code “Abaqus”. The calculated buckling forces were compared with the allowable one given by Eurocode 3. Repair methods of silos against buckling were proposed. A sensitivity analysis was performed for a silo to predict the location and profile type of strengthening elements.     

Buckling length determination of concrete filled steel tubular column under axial compression in standard fire test

The structural behavior of the column under fire becomes essential since it concerns the safety of buildings and people inside in case of fire event occurs. The standard fire tests were usually used to evaluate the resistance of the members under fire. This paper presents a method to determine the buckling length that was used to predict the resistance of the concrete filled steel tubular (CFST) column under axial compression in standard fire test. In this method, the fourth-order differential equation was used to develop the analytical model. Various boundary conditions of the column at working condition, e.g. fixed–fixed, fixed–pinned, and pinned–pinned, were considered in this analytical model. Design formulae and charts were developed to determine the buckling lengths that considered varying flexural stiffness along the column height in fire. Temperature-independent buckling lengths were also proposed to further simplify the fire resistance design procedure. To establish the validity, the determined fire resistance of CFST columns based on the analytical and proposed buckling lengths were compared with test results in literature and predictions based on empirical buckling lengths.     

Elasto-plastic failure of locally supported silos with U-shaped longitudinal Stiffeners

Ranging from agriculture to food processing, from mining to industrial processing, all these sectors have a need for the temporary storage of (dry) powdered, granular, and bulk materials between different stages of all kinds of manufacturing processes and between manufacturing process and transportation, or vice versa. Silos are therefore the perfect solution to meet this need, because they can easily store large volumes on a relatively limited floor space. Frequently, silos have a circular platform and are placed in elevated position. The latter can be achieved by a limited number of discrete equidistant supports around the barrel circumference. However, in such cases, large loads have to be transferred to the limited number of supports, causing locally high axial compressive stress concentrations, and consequently premature failure due to plastic yielding and/or elastic buckling (depending on the thickness of the silo wall). A possible answer to avoid these problems is to provide a partial-height U-shaped longitudinal stiffener above each support. Such stiffeners allow for a more gradual load transfer to the supports, increasing the maximum failure load. This paper aims to map the influence of the dimensions of such longitudinal stiffeners (i.e. the parameters of the cross-section and the height) on the failure behaviour of thick-walled silos. All results and findings are based on geometrically and materially non-linear analyses or GMNA performed with finite element software. The simulations indicate that correctly, for thick-walled silos, failure will always occur by (elasto-)plastic yielding. Depending on the longitudinal stiffener cross-section, the location of failure will occur in the stiffened zone of the silo just above the supports for silos with stiffeners with a small cross-section, whereas for stiffeners with larger cross-sections, failure occurs in the unstiffened zone just above the terminations of the stiffeners. In addition, the stiffener width in circumferential and radial direction have respectively an advantageous and a disadvantageous influence on the failure load. Finally, the stiffener height only has a positive impact on the failure load when failure occurs in the unstiffened silo wall. This can be addressed to the distribution of the supporting force over the entire circumference with higher stiffeners.     

热贮料作用下浅圆筒仓温度效应研究

为了研究热贮料对筒仓位移及内力的影响并方便设计时计算由热贮料产生的温度效应,本文推导了热贮料作用下仓壁位移和内力的计算公式,并通过数值模拟验证了公式的准确性。利用所推导公式分析了竖向温差对钢筒仓和内外、竖向温差对混凝土筒仓的影响。结果表明竖向温差使钢筒仓在冷热贮料交界面附近的仓壁出现较大的径向位移差;并导致温度应力显著增大;该温度应力随着径厚比的减小而增大。内外温差使混凝土筒仓上端产生较大的周向拉力;竖向温差也使筒仓中部的周向力增大;且径厚比对周向力的影响与钢筒仓相似。     

Q420高强度等边角钢轴压构件整体稳定性能设计方法研究

为研究Q420高强度等边角钢轴压构件的整体稳定受力性能与设计方法, 该文采用有限元软件ANSYS建立数值模型, 并经与试验结果对比验证后进行了大量参数分析, 研究了构件几何初始缺陷、残余应力和钢材屈强比对该类轴压构件整体稳定性能的影响, 分析了已有设计方法的适用性。结果表明, 构件初始缺陷对其稳定性能的影响与构件长细比及失稳模态有关, 残余应力的影响与构件长细比有关, 钢材屈强比的影响较小。基于数值计算结果建议了Q420高强度等边角钢轴压构件考虑板件局部屈曲相关作用的整体稳定设计方法, 为补充和完善我国钢结构设计规范提供了参考, 同时也有利于促进高强度钢材在我国钢结构工程中的应用。