玻璃建筑中带金属紧固件玻璃板的承载性能研究

介绍点式支承玻璃结构中带金属紧固件圆形玻璃板的承载力问题 ,分析了几种参数对带单紧固件圆形玻璃板模型的应力状态和承载力的影响     

驳接式玻璃板面外受弯承载性能的有限元分析研究

近年来,驳接式玻璃幕墙在现代建筑中得到了应用和推广。本文在仅考虑玻璃板面外受弯的情况下,通过有限元软件ANSYS作了比较,将模型1（考虑了垫层）和模型2（既考虑垫层又考虑垫层和玻璃板之间的摩擦滑移）进行了比较,并通过改变模型的几何参数讨论各种参数对玻璃板和驳接件承载性能的影响。研究结果表明：玻璃板厚度和驳接件大小对玻璃板的最大应力和挠度影响较大,而驳接件的厚度以及垫层的参数变化对玻璃板的最大应力和挠度影响较小;垫层对玻璃板的应力影响很小而对减小驳接件的内应力效果很显著;本文在定义平均节点转角的基础上,增大垫层厚度和减小垫层的弹性模量均会增大玻璃板的平均节点转角,但实际的节点平均转角很小。有限元与规范中点支式幕墙中玻璃板的设计方法的比较结果表明规范中规定驳接式玻璃板公式的必要性。     

托板桩复合地基桩体荷载分担比研究

采用有限元法研究了托板桩复合地基垫层内摩擦角、弹性模量、垫层厚度以及桩间距、桩体持力层对桩体荷载分担比和地基沉降的影响。研究结果表明,在满足地基沉降和承载力的前提下,应采用合理的垫层厚度、弹性模量和桩间距以减少工程费用。     

桩顶灰土垫层厚度对单桩水平承载力的影响分析

文章针对黄土场地在桩顶设置灰土垫层工况,就灰土垫层厚度对单桩水平承载力的影响进行研究。当桩顶下存在灰土垫层时,随着灰土垫层厚度增加,单桩水平承载力均呈现非线性增加的趋势,且增加梯度逐渐变小。当灰土垫层厚度较小时,灰土厚度增加引起的单桩水平承载力增幅较大。当灰土垫层厚度较大时,灰土垫层厚度增加引起的单桩水平承载力增幅较小。     

刚性基础按应力分布设置垫层的有限元分析

刚性基础下地基土的反力呈马鞍形分布,即两边反力大而中间反力小,目前的解决方法是按承载力控制或沉降控制等理论在基础底面设置垫层,以使基底土体承载力或沉降达到一致.针对绝对刚性基础,可以从控制基底应力分布一致的角度出发,为减少基底角、边处应力分布与内部之间的差异,考虑在基础底面设置两边强度大而中间强度弱的垫层,即在反力较大的部位设置强度较大的垫层,而在反力较小的部位设置强度较小的垫层,通过改变垫层强弱两部分的强度比、设置位置以及厚度,使得刚性基础的基底土应力分布达到一致.运用有限元软件Plaxis得出了垫层的优化设置方法,并分析了强弱两垫层材料的弹性模量、粘聚力以及摩擦角的变化对地基土应力分布的影响.     

带装配式MDW混凝土框架抗震性能研究

为研究带装配式金属消能减震复合墙板(metal energy dissipation composite wallboard,MDW)混凝土框架的抗震性能,基于有限元数值分析软件ABAQUS建立了10榀单层单跨带装配式MDW混凝土框架试件的有限元模型,分别研究耗能钢板厚度、墙板厚度及墙板间距等参数对试件抗震性能的影响,并将空框架数值模拟结果与已有相关试验结果进行对比验证,以确定数值仿真分析的正确性。研究结果表明:增加耗能钢板厚度能够明显提高试件的滞回性能、初始刚度、承载力,耗能钢板厚度过大的试件框架梁两端弯矩差值较大;增加墙板厚度,试件的初始刚度略有增加,墙板厚度变化对试件的抗震性能影响较小;随着墙板间距的增加,试件的耗能能力、初始刚度及承载力有所降低,延性略有提高。     

CFRP加固钢—混凝土组合梁抗弯承载力的参数分析

应用理论计算公式,对影响抗弯承载力的CFRP片材厚度、弹性模量以及混凝土强度等参数进行了分析,结果表明,使用弹性模量高、厚度大的CFRP片材加固的组合梁,承载力提高更大;采用高混凝土强度的梁,其极限抗弯承载力提高效果更明显。     

刚性桩复合地基垫层土拱效应宏细观机理研究

为了研究刚性桩复合地基垫层土拱效应的作用机理,通过可视化模型箱对不同桩间距及垫层厚度的刚性桩复合地基进行了室内模型试验,利用数字图像无标点量测技术研究土体颗粒的变形场,对桩顶垫层土体形成土拱的变化过程进行全面观测与分析,研究复合地基垫层土拱效应。利用离散元颗粒流方法,研究了复合地基桩间距、桩径、垫层土体厚度、土体内摩擦角和密实度等宏细观因素对土拱效应的影响规律。对离散元颗粒流模拟结果与室内模型试验结果进行对比分析,结果表明:垫层厚度越大、桩间距越小,垫层形成的土拱效应就越明显;土体摩擦系数、孔隙率对土拱效应影响较大,而桩径对土拱效应影响较小。刚性桩复合地基垫层土拱效应机理的研究对于提高垫层设计水平具有重要的参考价值。     

方钢管混凝土柱-钢梁半刚性节点参数分析

为了研究方钢管混凝土柱 钢梁半刚性节点的力学性能和影响因素,以方钢管混凝土柱 钢梁半刚性节点为研究对象,采用数值模拟分析方法研究了节点角钢厚度、角钢短肢长肢比及螺栓直径等参数对该类节点受力性能的影响规律,并给出了节点初始转动刚度的建议公式。结果表明:角钢厚度的变化对节点初始刚度影响较小,但对节点的塑性刚度和承载力影响较大;角钢短肢长肢比在一定范围内对节点刚度和承载力影响较明显,超过范围后只对节点的承载力有较大影响;螺栓直径的变化对节点承载力和刚度有一定影响,但影响程度较小,可不作为主要的影响参数。     

软土地基土工带加筋碎石垫层试验研究

加筋垫层能够提高地基承载力,增加地基稳定性。对某土质条件的加筋垫层进行现场试验,研究加筋垫层的作用和影响加筋效果的主要因素。分析了加筋层数、筋带间距、加筋线密度等参数对加筋地基强度和变形的影响。试验结果表明,垫层加筋后地基承载力显著增加,而且双层加筋效果更好。对于双层加筋,随着荷载的增加,靠近基底的筋带才先发挥作用。影响加筋效果的主要因素有加筋层数和加筋带的间距等。     

CFRP加固圆形钢管抗压承载力研究

以碳纤维增强复合材料(CFRP)加固长圆形钢管轴心受压试验结果为基础,分析了CFRP在加载过程中的力学行为并提出了CFRP的破坏与加固机理。考虑初偏心、材料和几何非线性的影响,建立了一个预测承载力、轴向和横向位移的纤维模型,分析了CFRP的有效抗压弹性模量与CFRP层数的变化关系。将有效抗压弹性模量应用于有限元模型中进行加载试验模拟,验证简化纤维模型的合理性。结果表明:在达到极限承载力之前,圆形钢管轴心受压构件中部全截面均表现为压应变,验证了提出的加固机理; 随着CFRP层数的增加,CFRP的有效抗压弹性模量按自然对数增长; 有效抗压弹性模量的引入较好地模拟了CFRP加固钢管的受压机理,并且纤维模型计算结果与有限元模型计算结果吻合良好; 随着加载偏心距增大,CFRP对长轴压构件承载力的贡献率逐渐降低,因此对于此类加固构件的使用应该尽量减小加载偏心距,以充分利用CFRP的抗压强度。     

Failure mechanisms of dowel-type fastener connections perpendicular to grain

Dowel-type fastener connections perpendicular to grain may fail in either a ductile or a brittle fashion. Whether the failure mechanism should be classified as ductile, depends on the definition of ductility utilized. Generally, the load-slip response is considered as a means of ductility quantification. In this respect, the elastic potential energy is calculated (being the area underneath the load-slip response) or the ratio of the ultimate slip and the slip at the onset of yielding is used, amongst others. Another approach relates to the European Yield Model which is commonly adopted in design standards to calculate the load-bearing capacity of dowel-type fastener connections. In this respect, ductility may be considered to be associated with plastic deformation of the steel fasteners solely since the deformation ability of connections with dowel-type fasteners at yield is much larger compared to situations with non-yielding fasteners. In the case of connections with rigid dowel-type fasteners, it therefore may be suggested that less ductility is exhibited although it is recognized that timber in compression perpendicular to grain exhibits plastic capabilities as well. Whether these connections behave either brittle or ductile is related to the spacing requirements as well.In this paper, first an overview of potential fracture and failure mechanisms of dowel-type fastener connections is provided. Experimental results of a variety of connections and corresponding failure mechanisms are presented. Based on mechanical models to predict the load-bearing capacity, classification of these connections in terms of ductility is provided, and the governing parameters involved are distinguished. This paper does not intend to provide a quantification procedure of ductility. Yet, an extensive overview of failure mechanisms and an analytical analysis of parameters involved are given providing expressions to calculate the failure mechanism being governing.     

弯剪组合作用下点支承玻璃承载性能的试验研究

点式玻璃幕墙玻璃面板在实际工程中通常在弯剪组合作用下工作。本文在试验的基础上分析了不同荷载作用下板内应力分布状况,找出弯剪组合作用下的应力控制点。本文指出,面内剪力对于孔边应力影响较大,且易引起紧固件的弯曲变形;在弯剪组合作用下,玻璃板孔边、大面中心及板边中点的应力均有可能起控制作用;当面外荷载使紧固件受拉时,面内剪力的影响很小,可以忽略,当面外荷载使紧固件受压时,应该考虑面内剪力对板承载性能的削弱作用。以上研究为进一步完善点式玻璃板的设计提供了依据。     

持力层对大直径扩底灌注桩竖向承载性状的影响

大直径扩底灌注桩的沉降以桩端土层的竖向压缩变形为主,因此端承土层特性对大直径扩底桩的竖向承载性状有较大影响。利用有限差分程序建立三维非线性有限差分数值模型,研究了持力层性质对大直径扩底桩竖向承载性状的影响。结果表明,大直径扩底桩承载力随持力层厚度的增加而增大,且在持力层厚度较小时持力层厚度的变化对承载力和桩端阻力影响显著。桩侧土层模量与持力层模量比为0.2时,桩端入持力层深度的变化在持力层厚度较小时对大直径扩底桩的极限承载力影响较大。相同持力层厚度下,桩侧土层模量的变化对大直径扩底桩承载力的影响较大,模量越大承载力越高;下卧层模量的变化对大直径扩底桩承载力的影响较大。     

深长大直径嵌岩桩单桩承载性状的有限元分析

采用线弹性与弹塑性模型,运用有限单元法对深长大直径嵌岩桩单桩的承载性状进行了分析。分析表明:桩身弹性模量、嵌入岩石弹性模量是影响单桩承载力及沉降的主要因素;当嵌入软质岩石时,嵌岩深度可适当加深。     

点式支承玻璃建筑中金属连接件承载性能的试验研究

在点式支承玻璃建筑中 ,金属连接件的承载性能对整个结构的承载性能有很大影响。对北京植物园展览温室点式支承玻璃结构中的金属连接件进行了承载性能试验 ,分别研究了固接浮头、铰接浮头、铰接沉头紧固件和X形、H形中间肢、H形边肢支承件的承载能力 ,并且计算了这些紧固件和支承件在实际工作中的强度储备。分析表明 ,在工程中还可以对金属连接件的设计进行优化 ,以节约材料。     

钢-玻璃组合梁平面内受力性能及计算方法研究

目前国内外对钢-玻璃组合梁结构的受力模式及承载力研究不足,对5个钢-玻璃组合梁试件进行了平面内受力性能试验,并基于多线性和线性材料本构模型进行了有限元分析。研究了采用钢化夹层（胶）玻璃腹板和单片钢化玻璃腹板组合梁的剪压破坏模式及纯弯曲破坏模式,两种破坏模式的区别在于纯弯曲破坏始于梁底弯矩最大部位,而剪压破坏在局部受压及剪跨区域发生。采用我国JGJ 102—2003中关于平面内玻璃肋受弯计算公式分析了组合梁承载力,基于塑性铰线方法提出了该类组合梁承载力的理论计算公式。研究结果表明：剪压破坏时钢化夹层（胶）玻璃腹板随着荷载增大而呈现明显的界面孔隙,相比同厚度的单片钢化玻璃腹板,夹层（胶）玻璃腹板能提高组合梁的弯曲变形能力。增加腹板玻璃厚度和胶结强度均可提高组合梁的承载力,且前者的贡献更为明显,对于后者,剪压破坏和纯弯曲破坏分别取决于结构胶的压缩模量和剪切模量。考虑了胶结部分受拉刚度贡献的有效截面系数能更好预测组合梁的纯弯曲破坏承载力,而提出基于塑性铰线机制的计算方法能更好预测组合梁的剪压破坏承载力。     

Test of screw fastened profiled roofing sheets subject to simulated wind uplift

Screw fastened light gauge steel profiled roofing sheets are predominantly subjected to wind suction, i.e., wind uplift, and may fail locally in the vicinity of screw fasteners under strong or sustained fluctuating wind uplift. A series of static tests was performed on three types of profiled roofing sheets to investigate their structural behaviour and profile effects under simulated wind uplift. The considered sheeting profiles were arc-tangent, trapezoidal and ribbed, and an alternate (or equivalent alternate) sheeting crest fastening system was adopted. It was found that structural behaviour of the roofing sheets under uplift loads was greatly dependent on the sheeting profiles including the shape and height of the crest. Both arc-tangent and trapezoidal type roofing sheets exhibited a large cross-sectional distortion stage and a deflection hardening stage, following a local plastic collapse in the vicinity of the screw fasteners at the central support. The ribbed roofing sheet, however, had a final failure mode of sudden fracture with cracks under the screw fastener head at the central support. The use of cyclone washers with screw fasteners reduced local plastic deformations and, in general, increased initial failure loads of the roofing sheets. Increasing the roofing span only slightly reduced the limit values of the reaction force per fastener at the central support due to the local failure characteristic of the screw fastened profiled roofing sheets.     

In-plane stability and shear deformation analysis of the H-beam hollow arch

H-shaped circular arc is a relatively novel type of open-web steel arch, and currently, no reports have been published concerning its in-plane stability. In this paper, the elastic and elastic–plastic in-plane stability of the H-shaped hollow circular arch is studied by theoretical deduction combined with numerical simulation. First, the overall shear rigidity of the H-shaped circular arch is calculated, and the elastic buckling load formula of the arch is proposed and verified considering double shear deformation under full-span radial and uniform loading. The overall elastic buckling load deduced in this paper is reasonable according to the finite element analysis. The results indicate that the influence of shear deformation on the overall elastic buckling load of the arch decreases with the increase of the span length. The arch-bearing capacity is the largest when the rise-span ratio is 0.25. Second, the restriction conditions necessary for avoiding local buckling of the chordal web before integral buckling of the H-shaped steel hollow circular arch are analyzed. Finally, the elastic–plastic failure mechanism of the H-shaped arch under full-span radial and uniform loading is examined, and the formula for determining the ultimate bearing capacity that is achievable before failure under full-span radial and uniform loading is proposed. ANSYS analysis shows that under the radial uniform loading, the chordal bars will yield near 1/4L and 3/4L, and ultimately, the structural failure of the lower chord occurs in the vicinity of 1/4L. The formulas presented in this paper agree well with the results obtained from the finite element analysis and can be used as a reference for engineering applications.