外伸式端板连接的蜂窝钢梁-复合焊接环式箍筋混凝土柱组合节点抗剪性能研究

通过低周往复加载试验,研究了外伸式端板连接的蜂窝钢梁-复合焊接环式箍筋混凝土柱组合节点的抗剪性能,得到如下结论:由于焊接环式箍筋的约束,三向受压状态下节点域的混凝土抗剪能力比钢筋混凝土节点混凝土的抗剪能力显著提高;外伸式端板连接型蜂窝钢梁-混凝土柱组合节点高强螺栓预压力的存在,使得节点域的混凝土开裂较少,改善了节点域的抗剪性能.     

外伸式端板连接型钢-混凝土组合节点合理螺栓布置研究

对7个高强螺栓外伸式端板连接的蜂窝钢梁-复合焊接环式箍筋混凝土柱组合节点试件进行低周反复加载试验,分析组合节点在模拟地震作用下的破坏形态和抗震性能,研究地震作用下组合节点合理螺栓布置形式,结果表明:相同的螺栓布置形式,螺栓直径大的其抗震受剪承载力高;不同的螺栓布置形式,螺栓尽量靠近梁翼缘的布置形式(3行3列)的节点是外伸式端板连接型钢-混凝土组合节点更为合理的节点形式.     

浅述十字板试验的应用

十字板剪切试验在测试饱和软粘土的抗剪强度中已经被广泛的应用,它是在计算地基的围堤稳定性、固结历史、承载力以及饱和软粘土灵敏度等相应力学参数必不可少的测试方法。该试验所测得的抗剪强度与试验深度处天然土层在原始压力下固结的不排水抗剪强度。     

木桁架齿板连接性能模拟的研究现状

从齿板连接构件材料及连接性质确定和连接性能模拟两方面介绍国内外木桁架齿板连接性能理论及模拟研究现状,并对三种常用的齿板连接性能研究的分析软件SAT、PPSAⅡ和ANSYS作了简单介绍。通过对文献资料的系统分析,认为齿板连接性能研究具有重要的科研和应用价值。     

预制混凝土夹芯保温板抗剪性能研究

对采用桁架筋连接件的新型夹芯保温板进行了剪切试验,以对桁架筋型保温板在受剪工况下进行研究。研究结果表明,当保温板厚度增加时,混凝土板间的相对位移增加,对试件的承载能力影响不大。     

型钢混凝土节点受力性能及承载能力计算方法比较

对型钢混凝土梁柱节点的受力机理和影响因素进行了分析研究.根据已有的节点试验资料,对YB规程、JGJ规程、我国梁柱节点专题组建议公式、AISC规范以及AIJ规范关于节点抗剪承载力计算公式进行分析比较,结果表明:JB规程直接考虑了轴力的有利作用,计算值与试验值整体吻合较好,但对于轴压比较大的试件以及高强混凝土试件,还需要进一步修正;我国梁柱节点专题组建议公式未对型钢混凝土柱-钢梁节点以及型钢混凝土柱-型钢混凝土梁节点做深入研究,应通过更多的试验数据对其进行修正完善.     

西安临潼黄土原位钻孔剪切试验研究

在工程建设中,非饱和土体的抗剪强度值以及内摩擦角的求取具有重要意义。为了精确求得该值,现在常用的方法有室内土工试验及原位试验。相对室内试验,原位试验能够最大限度的保持土的原位状态,并且受剪面非人为选取,试验所得数据更具有代表性。文章介绍一种原位钻孔剪切试验,利用美国生产的BST原位钻孔剪切仪来实地测定土的抗剪强度。主要介绍试验装置、工作原理、操作步骤及结论和建议,为原位求得内聚力及内摩擦角提供了新的思路和方法。     

钢筋再生混凝土梁的抗剪性能

结合国内外大量相关试验成果,本文对钢筋再生混凝土梁的抗剪性能进行了较为系统的研究分析,主要包括钢筋再生混凝土梁的抗剪受力及破坏特征,影响钢筋再生混凝梁抗剪承载力的主要因素以及钢筋再生混凝梁抗剪承载力的计算方法等。研究结果表明,钢筋再生混凝土梁的破坏形态与普通混凝土梁差别不大,主要取决于剪跨比;再生混凝土强度、剪跨比和配箍率以及再生骨料取代率是影响钢筋再生混凝土梁抗剪性能的主要因素;钢筋再生混凝土梁的抗剪机理与普通混凝土基本相同;普通混凝土梁抗剪承载力计算公式应用于再生混凝土偏于不安全。本文的研究成果对再生混凝土在结构中的推广应用具有一定的实际意义和价值。     

简支空心板梁桥粘贴钢板加固分析

对某高速公路中一跨8米钢筋混凝土简支空心板板底粘贴钢板进行理论分析,通过粘贴钢板前后桥梁各梁板极限抗弯承载力和极限抗剪承载力对比,发现粘贴钢板后原桥承载力提高了75%,但刚度提高效果并不明显。     

密封材料剪切性能的探讨

针对密封圈受到液压力作用后被剪切而导致液压缸内泄漏现象，文章设计了一种测试密封材料抗剪强度的试验工具，并对不同硬度、型号的橡胶材料的抗剪强度进行测试，找出了密封材料抗剪强度与硬度的对应关系，为液压缸密封配合间隙设计与密封材料选择提供参考。     

基于ANSYS的KKT型相贯节点承载力性能研究

针对空间管节点几何形式很多、受力复杂、影响节点承载力性能的因素也比较多等问题,对实际工程中常见的空间KKT型相贯节点的极限承载力性能进行了研究。基于数值仿真,主要采用ANSYS软件对空间KKT型圆管相贯节点进行了非线性有限元分析,揭示了节点的承载力性能和破坏模式;着重分析和总结了重要几何参数对节点极限承载力的影响;将此类节点的极限承载力分析结果与规范中T型、K型节点承载力计算公式进行比较分析。研究结果表明,节点的破坏模式大多属于主管管壁塑性破坏;T型支管与主管外径比β1、K型腹管与主管外径比β2、主管径厚比γ对节点极限承载力有主要影响;KKT型相贯节点的极限承载力计算公式与T型、K型节点承载力设计公式有些必然的联系。     

Stabwerkträger mit geleimten Knotenpunkten

The strength behaviour of 27 glued node joints for plane frameworks was determined in short-time failure tests. The different types of nodes and varying types of joints per node were tested. The longitudinal changes of the members at the nodes were measured, using glue-fixed strain gauge strips and novel strain gauge extensometers. After evaluating the test results from single nodes, not only shorttime failure tests, but also tests under dynamic long-duration load (about 10⁶ cycles) with concluding failure tests were carried out on twelve glued frameworks. The results confirm the reliable bearing behaviour of these types of structure. A reduction in bearing capacity due to dynamic long-duration load could not be detected.     

Stabwerkträger mit geleimten Knotenpunkten

The strength behaviour of 27 glued node joints for plane frameworks was determined in short-time failure tests. The different types of nodes and varying types of joints per node were tested. The longitudinal changes of the members at the nodes were measured, using glue-fixed strain gauge strips and novel strain gauge extensometers. After evaluating the test results from single nodes, not only shorttime failure tests, but also tests under dynamic long-duration load (about 10⁶ cycles) with concluding failure tests were carried out on twelve glued frameworks. The results confirm the reliable bearing behaviour of these types of structure. A reduction in bearing capacity due to dynamic long-duration load could not be detected.     

Influence of initial moisture induced stresses in multiple steel-to-timber dowel joints

In this experimental study, multiple steel-to-timber dowel joints were first exposed to controlled climate changes. After being stored in climate chambers, the joints were loaded to failure. The major aim of the study was to investigate how and to what extent initial decrease in moisture in the joint area inducing shrinkage deformations affects the load-bearing capacity of joints of this type loaded in tension parallel to the grain. The load-bearing capacity of the joints was found to be reduced under these conditions, the decrease being greatest for joints in which steel dowels connected to a steel plate inserted into a slot in the wood restrained the shrinkage deformations during storage in the climate chamber. It was also found that the reduction in load-bearing capacity was greater and moisture-induced cracks were more frequent when the distance between the dowel rows were greater.     

Effect of chord splice joints on force distribution and deformations in trusses with punched metal plate fasteners

The span of roof trusses with punched metal plate fasteners (nail plates) makes it often necessary to use splice joints in the top and bottom chords. In the finite element models used for design of the trusses these splice joints are normally assumed to be either rotationally stiff or pinned – their real behaviour is semi-rigid. The influence of splice joints on the distribution of member forces and rotations in the splice joints is investigated in this paper. A finite element program, TrussLab, where the splice joints are given semi-rigid properties, is used to analyse the effect of splice joints. Timber-to-timber contact and non-linear elastic behaviour are included in the model. Results from tests with joints under four-point bending are compared with predictions given by TrussLab, and a good agreement is found. Splice joints in trusses with nail plates may be assumed to be rotationally stiff if their deformation has no significant effect upon the distribution of member forces according to Eurocode 5. Two simple guidelines for the design and location of splice joints are given in Eurocode 5 for treating the splice joints as rotationally stiff. The reasonability of these guidelines and the influence of splice joints on section forces and displacements are discussed considering the results from finite element calculations for a fink truss. It seems that the guidelines for treating splice joints as rotationally stiff do not necessarily lead to more realistic truss models.     

Festigkeit großflächig geleimter Knotenverbindungen

The load bearing behaviour of joints with large overlapped glued areas was tested experimentally in 203 specimens. The following parameters were varied: The angle of gluing (0°, 30°, 60°, 90°), size of overlapped glued area (50, 100, 200, 400, 600 cm²), clamping pressure (0.2 and 0.6 MPa) and pressure technique (conventional clamping pressure, pressure by nailing), wood quality (knots in the overlapped glued area) and the kind of load transmission in the overlapped glued area (shear by loading in tension-compression, shear by loading in pure tension). Corresponding to the joint design the shear strength values obtained ranged from 1.4 MPa to 3.8 MPa. The angle of gluing, the kind of load transmission and, in small overlapped glued areas, the tension stresses perpendicular to the grain as a result of excentric chord junction were found to be the decisive parameters. Nailed-glued joints proved equivalent to conventional glued joints.     

Load-carrying capacity of timber-to-timber joints of fast-growing Argentinean Eucalyptus grandis with nails of small diameter laterally loaded in double shear: analysis according to the criterion adopted by European standards

The present paper reports the results of an investigation regarding the study of the load-carrying capacity of connections with nails of small diameter pneumatically driven in timber-to-timber joints of fast-growing Argentinean Eucalyptus grandis. The effectiveness of the equations provided by Eurocode 5 for calculating the lateral load-carrying capacity of these joints was checked for the specimens exhibiting the geometrical parameters adopted by the European design rule and also for those with reduced spacing and end distances. A failure mode presenting features common to both j and k types of failure according to the criterion of the European design rule confirmed that the plastic hinges could be developed before brittle failure due to splitting or block shear occurred, even if the specimens present reduced spacing and end distances. The load-slip curves confirmed ductile behaviour for all cases. The empirical results showed that the structural design is situated on the conservative side if the equations adopted by Eurocode 5 are applied to the analysed connections when the spacing and end distances recommended by this design rule are used. The results also showed that the joint area may be decreased by up to 31 % in relation to that corresponding to the recommended spacing and end distances without reducing the load-bearing capacity below the characteristic value determined according to the European design rule.     

Plug shear failure in nailed timber connections

Brittle failures in mechanical timber joints should be avoided, because this often results in low capacity and brittle failure of the structure. Nailed joints experience three ultimate failure modes: embedding, splitting or plug stear failure. To avoid plug shear failure, short and wide joints are preferred, limiting the number of fasteners in line with the load and grain direction. Plug shear failure was examined in short-term experiments on nailed steel-to-timber joints in glulam loaded in tension parallel to the grain with five different joint geometries. The aim of the study was to examine if the fastener group layout can be adjusted to avoid plug shear failure and to gain an insight into the causes of failure initiation. Using spring models, it is shown that the load distribution creates pronounced stresses at the last nail in the joint, which probably initiates the plug shear failure. Test results are compared with prediction models found in the literature. It was found that fasteners placed in groups can be a successful way of reducing the risk of plug shear failure. The failure is probably initiated at the nail farthest from the free end, where tensile stresses perpendicular to grain occur.     

PET板和金属板串联下的介电常数及其影响因素分析

含金属纤维纱线由金属纤维、普通纤维和空气的混合体构成,其介电常数的研究较为复杂。本文采用PET板、铜板和空气以不同方式进行串联,模拟含金属纤维纱线及其理想结构,推导出不同串联方式下介电常数的计算公式。同时,采用介电谱仪测试不同串联方式下的介电常数,表明测试结果和计算结果具有较好的一致性。实验条件下,串联复合体的介电常数随着金属含量增加而增加,随着空气含量和PET含量增加而减少。