落叶松规格材的钉连接性能

钉连接是木结构中常用的连接方式之一。依据美国钉连接的试验方法及设计值的确定方法,对我国东北地区落叶松的钉连接性能进行了检测。结果表明,随着圆钉直径的增大,落叶松的抗拔出力和抗剪切力基本呈上升趋势。并对东北地区落叶松钉连接的参考设计值进行了分析。     

兴安落叶松规格材握钉性能及钉连接承载性能研究与评价

钉连接是轻型木结构重要的连接方式之一,本文介绍了美国握钉性能和钉连接承栽性能评价方法,并以兴安落叶松为研究对象,对其握钉性能和钉连接承载性能进行了研究分析。     

三种规格材圆钢钉拔出握钉力性能研究

借鉴国家标准GB/T 14018—2009"木材握钉力试验方法",通过对横截面为38 mm×50 mm的国产日本落叶松、兴安落叶松和进口云杉三种规格材拔出握钉力性能进行试验,分析木材切面、圆钢钉直径及规格材种类对拔出握钉力性能的影响。研究结果表明:日本落叶松规格材三切面的拔出握钉力大小依次为弦切面径切面端面,且端面拔出握钉力的变异系数明显大于径切面和弦切面;日本落叶松规格材各切面的拔出握钉力及其变异系数均随钉直径的增加而增加;三种规格材试样的拔出握钉力性能为:日本落叶松兴安落叶松云杉,且兴安落叶松规格材握钉力的变异系数较大而云杉规格材较小;木材切面、钉直径和规格材种类对木材圆钢钉拔出握钉力均具有极显著影响,该研究中的木材拔出握钉力三个影响因子的效应大小为:钉直径木材切面规格材种类。     

日式剪力墙覆面板钉连接性能试验研究

剪力墙是日式梁柱式木结构最主要的抗侧力构件,其抗侧力取决于覆面板钉连接的性能。按照日式剪力墙构造制作剪力墙覆面板钉连接试件,分别进行单调和往复加载试验,分析钉连接的破坏模式、荷载-位移曲线及承载力,并对相关曲线进行拟合分析。研究表明,加载方式对钉连接测试结果有明显影响;落叶松胶合板和辐射松/杨木复合胶合板的覆面板钉连接性能均较好,二者承载力相近。     

轻型木结构用规格材握钉性能试验及钉连接承载性能评价方法

通过作者掌握的有关技术资料和标准,简述了轻型木结构用规格材的握钉性能及钉连接承载力评价方法,并对相关标准的试验评价方法进行比较。     

开槽沉头自攻螺钉增强轻型木结构剪力墙抗侧性能研究

轻型木结构剪力墙在水平荷载作用下常发生墙骨柱上拔破坏,从而削弱剪力墙的抗侧性能。本研究提出采用自攻螺钉连接边墙骨柱与底梁板的轻型木结构剪力墙,并以骨架钉种类、自攻螺钉直径和长度为变量,对传统轻型木结构剪力墙和自攻螺钉增强轻型木结构剪力墙进行单调加载对比试验。结果表明：剪力墙破坏时,其边墙骨柱弯曲且上拔较小,覆面板与墙骨柱间破坏较轻。与普通剪力墙相比,自攻螺钉增强剪力墙抗剪强度提高16%～33%,弹性抗侧刚度提高27%～111%,延性系数提高1.7%～31.7%,耗能提高2%～18.8%。因此,采用自攻螺钉连接边墙骨柱与底梁板可以有效提高剪力墙抗侧性能。     

锈蚀诱导处理下竹钉和钢钉的抗剪性能

以钢钉、普通竹钉和压缩竹钉连接SPF(云杉-松木-冷杉类)规格材试件,用质量分数为5%的盐水对试件作锈蚀诱导处理,进行短梁剪切和抗剪试验,探讨锈蚀诱导处理对钉抗剪性能的影响。结果表明,竹钉和木材连接部位呈犬牙交错状,能有效约束木构件,维持其抗剪性能;锈蚀诱导处理对钉连接的水平剪切承载力和极限抗弯承载力的影响不显著,不同钉连接的水平剪切承载力和极限抗弯承载力无显著差异,水平剪切承载力范围为6.08~6.90 k N,极限抗弯承载力范围为6.19~7.01 k N;锈蚀诱导处理使钢钉剪切破坏提前,而对竹钉的极限荷载影响并不显著;锈蚀诱导处理使普通竹钉的极限荷载对应位移显著增大,而对钢钉和压缩竹钉影响不显著。     

无框蜂窝板板式家具五金连接件的开发与应用

1 板式家具连接原理 1.1 现代板式家具连接方式 现代板式家具主要以人造板材为基材,家具五金配件做"搭桥"式结构连接.家具五金安装在板材上,需要对板材打孔,"32mm"孔分为系统孔和结构孔,系统孔为直径5mm,深度13mm,孔中心间距32mm的预钻孔;系统孔用作结构孔时,孔直径与深度按照家具五金件要求进行加工.     

重组竹材结构连接性能的研究进展

对重组竹材的基本性能进行综述,其力学性能与木材相近,密度大,碳化后的重组竹纹理与高级木材相近,干缩系数较小,适用于家具制作。重点对榫卯连接、螺栓连接和钉连接三种常用连接方式对用重组竹材的结构连接性能进行了综述分析,榫卯结构连接比一般的木材强度高;螺栓直径、纹理方向和含水率对连接点的影响显著;螺钉的拧入深度和导入直径比螺钉种类对结合强度的影响更为显著。     

工字梁翼缘与覆板钉连接的承载性能测试

采用钉连接工字梁翼缘与覆板,研究钉直径、覆板种类和厚度对钉连接节点处静态和动态承载性能的影响。结果表明,对于两种覆板材料,随着覆板厚度和钉直径的增大,连接节点处的静态承载和动态承载性能基本呈现增加的趋势;采用直径3.8 mm的圆钉,进行22 mm厚定向刨花板(OSB)与工字梁翼缘连接时,试样具有较佳的静态和动态承载性能。实际生产过程中,需根据覆板的厚度选择不同直径的圆钉。     

木结构连接用圆钉性能研究

钉连接是木结构中常用的一种连接方式，圆钉是木结构钉连接的主要材料，本文对国内和美国不同厂家生产的圆钉力学性能和尺寸进行了检测。试验证明，国产圆钉与进口圆钉的尺寸及力学性能相近，国产圆钉可以代替进口圆钉用于现代木结构建造中。     

Withdrawal strength of nailed joints with decay degradation of wood and nail corrosion

Nailed timber joints are widely used in timber structures, and their deterioration may cause significant damage. We investigated the withdrawal strength of joints using steel wire nails in specimens exposed to a brown-rot fungus. We also examined the effects of nail corrosion on withdrawal strength, because high humidity conditions accelerate not only wood decay but also the corrosion of nails. We found that nail corrosion increased the withdrawal strength. The ratios of withdrawal strength of nailed joints with rusted nails to that of joints with a minimally rusted nails were 1.47 and 1.56 in joints nailed in radial and tangential directions to annual rings, respectively. Withdrawal strength, excluding the effects of nail corrosion, had a negative correlation with mass loss and Pilodyn-pin-penetration-depth-ratio. We estimated the withdrawal strength of the nailed joint with decayed wood and rusted nails by multiplying the values from the empirical formula (obtained from mass loss and Pilodyn-pin-penetration-depth-ratio) by 1.47 and 1.56 for joints nailed in radial and tangential direction to annual rings, respectively.     

Yield load prediction of nailed timber joints using nail diameter and timber specific gravity

Prediction of yield load has nowadays been accepted as the basis for the limit state method of the design. Currently, there are many methods to predict the yield load of timber joints. These methods, i.e Foschi, Johansen, Smith and US 5% nail diameter offset, are reviewed in-depth in this paper. In this study, the authors presented a new approach which, hopefully, is simpler than the existing methods. The paper outlines the works carried out to arrive at the formula. About 300 Malaysian timber nailed joints were fabricated and tested to obtain the relationship between yield load and maximum load and to propose a new method to predict the yield load of a nailed joint. There seems to be a direct relationship between the yield load and the maximum load. From this relationship, a new formula, which depends only on nail diameter and specific gravity, was established.     

Effects of density profile of MDF on stiffness and strength of nailed joints

Nail-head pull-through, lateral nail resistance, and single shear nailed joint tests were conducted on medium density fiberboard (MDF) with different density profiles, and the relations between the results of these tests and the density profiles of MDF were investigated. The maximum load of nail-head pull-through and the maximum load of nailed joints were little affected by the density profile. However, the ultimate strength of lateral nail resistance, the stiffness, and the yield strength of nailed joints were affected by the density profile of MDF and showed high values when the surface layer of the MDF had high density. It is known that bending performance is also influenced by density profile. Therefore, the stiffness and the yield strength of nailed joints were compared with the bending performance of MDF. The stiffness of nailed joints was positively correlated with the modulus of elasticity (MOE); in the case of CN65 nails, the initial stiffness of joints changed little in response to changes in MOE. The yield strength of nailed joints had a high positive correlation with the modulus of rupture (MOR). The stiffness and the yield strength of nailed joints showed linear relationships with MOE and MOR, respectively.     

Shear resistance and failure modes of nailed joints loaded perpendicular to the grain

Shear tests were conducted on nailed joints in wood that were loaded perpendicular to the grain; these joints had 21 specifications depending on different combinations of wood species, nail dimensions, number of nails, and edge distances of the main members, and their effects on the shear resistance of the nailed joints were also investigated. The nailed joints with CN75 nails had higher initial stiffness than the joints with CN50 nails, provided the initial stiffness of nailed joints connected with 3 or 5 nails was not always a simple product of the number of nails and the initial stiffness of nailed joints connected with a nail, and instead depended on the combination of wood species of the main member and nail dimensions. When the edge distance decreased, the maximum load and energy capacity decreased, thereby affecting the energy capacity. The maximum load of the nailed joints with CN75 nails may be smaller than those with CN50 nails depending on the combination of wood species and nail dimensions. When the edge distance of the nailed joints was less than 26 mm, the energy capacity of the nailed joints with CN75 nails was less than or similar to those with CN50 nails.     

Analysis of load-slip characteristics of nailed wood joints: application of a two-dimensional geometric nonlinear analysis

We used a two-dimensional finite element method to analyze the load-slip characteristics of nailed wooden joints sheathed with a panel. We used tests of nail bending, nail shank embedment in a wood or a panel, nail-head embedment in a face of a panel, nail withdrawing from a wood, friction between a wood and a panel, and initial axial forces of the nails. The values of the material properties for the analytical models were determined with the above tests. With a conventional one-dimensional analysis it is impossible to evaluate the shearing performance accurately because the axial forces of the nail are not calculated. Therefore, we used two-dimensional geometric nonlinear analysis. The computed load-slip curves closely matched the original experimental results; and when the friction and initial axial forces were considered, the computed curves were more likely to match the original experimental results. Our results suggested that it is better to use geometric nonlinear analysis to analyze the shearing characteristics of nailed joints, and that friction and axial forces are important factors for accurate analysis.Parts of this report were presented at the 7th World Conference on Timber Engineering, Malaysia, August 2002     

Effect of moisture content of members on mechanical properties of timber joints

To investigate the effect of moisture content (MC) of members on the mechanical properties of timber joints, bending tests of precut joints and shear tests of dowel-type joints were carried out using timbers of Japanese cedar (Cryptomeria japonica D. Don) with three moisture conditions: green, kiln-dried with a MC target of 15%, and over-kiln-dried with a MC target of 5%. For the bending test, timbers were processed with a precut processing machine into “koshikake-ari” (a kind of dovetail joint) and “koshikake-kama” (a kind of mortise and tenon joint). A pair of members was jointed together without mechanical fasteners. Bolts (diameter = 12 mm) and nails (diameter = 2.45 mm) were used as dowels in the shear test. Bolted joints were constructed with one bolt and two metal side plates. Two nails and two metal side plates were used for the nailed joint. For precut joints, no clear effect of MC was recognized on maximum moment and initial stiffness. The maximum strength of mechanical joints assembled with kiln-dried wood was changed by the degree of drying. Stiffness of the joints assembled with kiln-dried specimens was larger than that of the joints assembled with green specimens.Part of this study was presented at the 7th International IUFRO Wood Drying Conference, Tsukuba, July 2001