Development of LVL frame structures using glued metal plate joints II: strength properties and failure behavior under lateral loading

In past years high priority was given to developing a seismic design for wood structures, including research on the response of wood structures to earthquakes. In this study a new type of portal frame with relatively large span was developed for the traditional Japanese wooden houses with large openings at the front to strengthen the structure. Stainless steel plates coated with zinc and glued with epoxy adhesives on laminated veneer lumber (LVL) members, composed of Douglas fir veneer and bonded with phenolformaldehyde resin, were used. The connection between the frame's beam and columns and between the columns and groundsills was mechanical, with bolts. The subject of this research was to analyze strength properties and failure behavior of glued LVL metal joints used as structural components and to evaluate the response of LVL portal frames under cyclic lateral loading. The results show that portal frames using glued LVL metal plates have a good multiplier for the shear walls and may be applied to traditional Japanese structures. The equivalent viscous damping provided good energy dissipation in the frames. The joints displayed good mechanical behavior during tests; moreover, the structures demonstrated high strength, stiffness, and ductility, which are necessary for a seismic design.Part of this paper was presented at the 47th annual meeting of the Japan Wood Research Society, Kouchi, April 1997; and at the 5th world conference on timber engineering. Montreux, Switzerland, August 1998     

Investigation of the maximum front to back load in the chairs made from curved and modified poplar wood

The aim of this research was to build a chair resistant to force from front to back. To achieve this goal, poplar wood was treated with heat and steam, and then curved at an angle of 90°. Curved frame was used for manufacturing chairs. In this study, three different designs of chairs were used. Control sample is a chair of custom type. The first design was a chair with a curved frame forming the structure back down to bottom (one-piece type) and the second design with two curved parts (two-piece type). Front to back load tests were conducted by mechanical universal testing machine in accordance with DIN EN 1729-2 standard. For each design, the test was repeated three times. The results of the experiment showed that differences between the designs were significant. The full type chairs were broken at the load about 1725 N, but the partial type chairs at about 1421 N. For the top to bottom load test, the full type chairs were broken at about 1052 N, other chairs were more resistant. In general, by introducing a design using the curved frame made of treated poplar, the resistance of chairs is improved.     

“C”型平面高层结构设计分析与调整措施探讨

为研究平面凹凸特别不规则以及结构扭转、楼层抗剪承载力一般性不规则结构的受力性能,采用PKPM-SATWE软件建立模型并进行计算分析.结果表明,结构楼层质量分布均匀,结构刚度分布合理,不存在薄弱层,结构剪重比满足规范要求,在规定风荷载（100a一遇）及地震作用下存在一定超出规范一般限值要求项,但均满足较为严格的规定要求;为降低平面不规则给结构所带来的不利影响,可采取提高框架柱抗震等级、增加楼板配筋和增加结构薄弱层剪力墙及框架柱的配筋三种措施进行调整.     

Lateral performance of a semi-rigid timber frame structure: theoretical analysis and experimental study

Semi-rigidness of the joint connections is one of the main characteristics of timber structures. The pin-joint assumption for the semi-rigid joint connections might be not conservative in the timber structural design. In this paper, structural analysis was conducted on a semi-rigid timber portal frame; the formulas were derived in terms of the internal force and the lateral stiffness, and the influence of the semi-rigid connections was discussed. Moreover, experimental tests were performed on three full-scale timber portal frames and five bolted timber connections to study the lateral performance of the frames and the moment resistance of the connections. For consistency, the connections from the portal frames and the connections for bending tests were of the same configuration. Finally, a calculation flowchart of the lateral performance on a semi-rigid frame was presented to verify the derived formulas and to show a framework of the lateral structural design process.     

正交胶合木横纹承压性能研究现状

正交胶合木（CLT）在木结构建筑中应用越来越广泛，特别是在中高层建筑物中。CLT作为楼盖构件使用时，承受柱或墙体施加的垂直荷载，因此CLT产品的设计及应用需要其横纹承压弹性模量和强度方面的参数；改善CLT横纹承压性能，也可以提高整体结构强度和建筑安全系数。文中主要介绍目前CLT横纹承压性能测试方法，总结CLT横纹承压性能影响因素方面的研究进展，以期为国内CLT研究提供参考。     

空心胶合木梁柱式结构抗侧力性能研究

为研究空心胶合木梁柱式结构体系抗侧力性能,对纯框架及框架-人字撑两种单跨结构试件进行了单调及低周反复加载试验,考察了结构破坏模式、耗能能力、刚度等抗震性能。结果表明:纯框架与框架-人字撑结构均具有一定抗侧力性能,但纯框架结构承载能力较弱,不建议单独用于工程实践;框架-人字撑结构具较大抗侧刚度及承载力,分别为纯框架的6.3倍及2.68倍,但其延性仅为纯框架的67%。两种结构失效前强度退化小于30%,具足够剩余承载力。     

连续压机活动式机架变形与热力耦合特性研究

为研究连续压机机架变形及热力耦合效应对其性能的影响,根据人造板生产热压工艺,确定了高压段机架受载条件;基于CPS型压机机架,设计一种可活动式机架,根据材料力学理论分析、求解了活动式机架中主要构件的受载变形情况,确定了活动式机架立柱与上、下横梁的主要结构尺寸;利用软件建模分析方法,建立了活动式机架结构模型,得出机架温度场与热应力分布状况,分析了热力耦合效应与静载条件下机架结构的应力、应变分布状态。结果表明:热力耦合效应对活动式机架结构变形及其应力、应变状况的影响显著,其不仅会改变机架最大应力与应变的位置,还会显著增大应力与应变的幅值;因此,针对连续压机机架进行热力耦合分析具有重要实用价值,可为连续压机机架结构的设计与优化提供理论指导。     

角钢⁃集成材L形组合柱的受压性能研究

为提高装配式木结构中异形柱的力学性能,设计了一种用热压等边角钢和SPF集成材为原料,环氧树脂胶黏剂连接制作的角钢-集成材L形组合柱,作为框架结构或框架剪力墙结构的角柱。以角钢边宽度对L形柱正截面承载力的影响进行了轴压试验研究,并进行ANSYS有限元模拟,以判断模拟预测的准确性。结果表明:角钢-集成材L形组合柱相对于同截面面积的木柱而言承载能力上升37.0%~51.4%,刚度上升36.5%~72.8%,同时L形柱有良好的延性;适当增加L形柱中的角钢边宽度可以使承载能力有效提高,但是其短边处的集成材易产生破裂,增加试件的脆性破坏;集成材之间的环氧树脂胶合界面在破坏前后都性能良好,在材料弹性阶段钢材和木材有效共同受力,承载力计算时需要考虑钢材的塑形增强作用;ANSYS有限元模拟的角钢-集成材L形组合柱弹性模量结果和试验结果一致,误差在10%以内,模拟结果基本可靠。研究成果对于预测角钢-集成材L形组合柱在实际预制装配时的安全可靠性提供了理论依据。     

胶合空心木柱结构设计与制造工艺

胶合木结构建筑中,柱作为轴心受压构件,需要对其承载能力进行强度和稳定性验算。对空心柱进行理论设计计算,从而确定一定尺寸、规格下柱能承受的最大载荷。由于没有专用设备进行实验论证,本研究仅对不同规格的空心木柱和实心木柱进行对比,得出了在保证空心木柱强度与实心木柱相当时,空心木柱的外围直径与实心木柱相比均有一定程度扩大的结论,从而使胶合木结构中的胶合木柱达到了美观与结构的双向要求。同时提供了几种具体空心木柱的外观设计。     

Bending resistance of repaired column members and shear resistance of opening frames with repaired columns of conventional Japanese wooden houses

When it is necessary to repair conventional Japanese wooden houses, the decayed lower parts of columns should be replaced with new wood material. The bending resistance of columns repaired by four methods and the shear resistance of opening frames with those repaired columns were investigated in this study. Bending tests of the repaired columns showed differences in initial bending stiffness and maximum bending moment related to the repair methods and loading direction. Racking tests were conducted on door opening frames with conventional door head members or upper partial walls sheathed with 12-mmthick plywood. The conventional frame specimens broke at door head-column joints with no obvious bending deformation of the columns, resulting in little difference in load-shear deformation curves among the repair methods. The columns of plywood-sheathed specimens, on the other hand, clearly were bent after the nails at the plywood-to-wood frame joints started to pull off. The load-shear deformation curves of the plywood-sheathed specimens did not vary regardless of the repair methods when shear deformations were small but were affected by repair methods as shear deformation increased.     

Fuel types and crown fire potential in <Emphasis Type="Italic">Pinus halepensis</Emphasis> forests

There is a lack of knowledge to identify and classify forest structures according to the risk of crown fires, especially in Mediterranean regions. In this study, for the first time, we use real information, obtained after a wildfire that burnt under extreme meteorological conditions, to classify forest structures of Pinus halepensis into fuel types as a function of crown fire potential. We identified fourteen forest structures which characterize many forest types in Western Mediterranean areas depending on canopy closure, number of tree layers, percent of each tree layer and overall tree density. By using the pattern of fire types that burnt the most numerous forest structures, we have identified four fire hazard groups of forest structures which are considered different fuel types. The first two had the lowest risk of active crown fires and they differed in the proportion of surface fires and passive crown fires. The third fuel type was the threshold between structures with low and high extreme fire behavior; while the fourth had a high risk of active crown fires. Firefighters and forest managers who are demanding this kind of schema, will test and upgrade this classification of fuel types in function of crown fire potential during future wildfires.     

结构调控对沙地樟子松人工林生长及枯梢病的影响

经对沙地樟子松人工林进行不同方式的结构调整试验,结果表明:对40年生左右染病较重的沙地樟子松人工林进行卫生伐引导成疏林草地,7年间疏林处理的胸径生长量比对照的高62.96%,疏林处理和对照的蓄积收获总量差异不大,疏林的树势得到增强,病害防控效果明显。对30年生左右的沙地樟子松人工林进行改造后,伐1留1从伐后第3年胸径生长量显著超过对照;伐1留1的总蓄积最大;伐1留1和伐2留2改造措施均对病害有抑制作用,且伐1留1效果更明显。处理的冠层结构发生了明显的变化,群落的透光率上升。疏林模式和林分改造措施有利于改善林分水分状况,在干旱年份效果更加明显。对30年生左右的沙地樟子松带状人工林,选用6个树种进行树种结构调整,建立了5种混交模式林,增加了树种多样性,改善了林分树种、年龄结构,丰富了沙地樟子松人工林景观,提高了林地生产力。     

合肥环城公园城市森林群落结构与树木配置特点

本文应用植被研究方法,采用样方调查资料来分析环城公园的树种构成、树木的高度及径阶分布、健康状况,并通过计算主要组成树种的生长指数,种间关联度来揭示群落构成的特点。结果表明环城公园群落结构比较复杂,有22对组成种表现正相关,其中侧柏-红叶李-桂花,刺槐-女贞,刺槐-银杏-石楠,加杨-女贞-桂花,中槐-女贞-黄杨,青冈-蚊母的组合中树木的生长良好,群落结构也比较稳定,       

Effect of lintel on horizontal load-carrying capacity in post-beam structure

This study is aimed to evaluate whether lintel has structural effect because it has not been categorized as a structural member. This study experimentally evaluated the horizontal load-carrying capacity of post-beam timber frame structures with bi-linear model and energy dissipation mechanism. To evaluate the effect on horizontal performance of lintel which has been widely used as wall frame in Korean traditional post-beam structure, two frames were tested in different types. One had no lintel and the other one had lintel at the height of 800 mm, respectively. Cyclic loading tests were conducted for each frame according to the standard loading protocol. Frame which had lintel showed slightly higher stiffness. And it showed noticeably significant energy dissipation performance after yield point of the joint. And that leads to the conclusion that lintel has structural effect and it should be considered as an important factor when evaluating horizontal performance of the structure after yield point of the joint.     

The Optimum Structure of Forest Type and Tree Species in Qiuqiangou Forest Farm,

选用层次结构的层次分析法作为数学工具,对山西省秋千沟林场的林种和树种结构进行了研究．结果表明：该法对于“目标结构比较复杂,缺乏必要数据的结构优化问题”比较适用,可按兼顾生态效益、社会效益和经济效益,又要有所侧重的原则,将各林种、树种的面积比例落实到合理的水平上．     

古尔班通古特沙漠2种土壤培育的梭梭幼苗木射线解剖特征

采用盆栽模拟试验,结合使用WinCell木细胞成像系统和光学显微镜技术对在2种土壤类型上培育的梭梭幼苗木射线解剖结构进行观测,探究木射线组织比量的特征。结果表明:梭梭木射线为单列或多列共存,属Kribs异形Ⅰ和异形Ⅱ,所观察到的木射线多为多列射线。沙土木射线平均高度为182.33μm,为砾石射线高度的1.7倍;沙土木射线平均宽度为39.58μm,为砾石木射线宽度的1.1倍;沙土类型的木射线细胞壁厚度为0.65μm,砾石类型的木射线细胞壁厚度为0.31μm,沙土类细胞壁厚度极显著大于砾石类(P0.01);沙土类梭梭平均木射线细胞高度为3.25μm,砾石类梭梭平均木射线细胞高度为2.97μm,二者没有显著差异;沙土类梭梭平均木射线细胞宽度为1.82μm,砾石类梭梭平均木射线细胞宽度为1.65μm,二者没有显著差异;沙土类梭梭平均木射线细胞面积为4.64μm2,砾石梭梭平均木射线细胞面积为3.84μm2,二者没有显著差异;沙土类型梭梭平均木射线比量为5.20%,砾石类型梭梭平均木射线比量为3.93%,二者没有显著差异。梭梭采用不同木射线解剖结构特征来适应不同沙漠土壤结构状况。     

Response of maple sapwood to injury and infection

In sapwood challenge experiments in Acer rubrum, columns of discolouration initiated by wounding and inoculation with pioneer fungi (Cephalosporium sp., Phialophora sp.) were similar in size to untreated wounds. Inoculation with decay fungi (Pleurotus ostreatus, Trametes versicolor) produced larger columns of wound-initiated discolouration. The removal of bark around a bore wound caused a significantly larger column to form compared to the sum of the columns inititiated by separate wounds. Stage-I discoloured wood, not associated with obviously rotted wood, had concentrations of mobile cations and soluble phenols similar to sapwood. Stage-II discoloured wood, spatially associated with rotted wood, was frequently bounded by a chemically distinct boundary layer and the discoloured wood contained significantly greater concentrations of mobile cations and soluble phenols than stage-I discoloured wood.     

Lignin fragments rich in detached side-chain structures found in water-soluble LCC

The content of the glyceraldehyde-2-aryl ether-type structure in water-soluble lignin–carbohydrate complex (LCC) fractions, which were obtained from Japanese cedar and birch residual wood meal after milled wood lignin isolation, was determined by ozonation. Quite high amounts of the glyceraldehyde-2-aryl ether-type structure were found in water-soluble LCC fractions of both species; about 3–5 times higher than those of other fractions. This result, as well as the high content of the β-1 structure in these fractions shown in our previous reports, suggest that lignin in these fractions has the characteristics of endwise-type lignin, because the glyceraldehyde-2-aryl ether-type structure and β-1 structure are typical characteristics of this type of lignin fraction. These results are in good agreement with the generally accepted hypothesis that the glyceraldehyde-2-aryl ether-type structure and β-1 structure are generated at the same time by a radical coupling reaction. The results also indicated that these two structures are present in close proximity in the lignin.     

双臂篱架赤霞珠葡萄架式结构对光照及浆果品质的影响

通过对赤霞珠葡萄传统的双臂篱架架式结构进行改造,改变双篱架上口的宽度,将传统的“U”字型架式改造为“V”字型架式,达到改善架面通风透光条件,提高浆果品质的目的。试验表明,“V”字型架式上口间距应不小于100cm。     

Using landscape metrics and topographic analysis to examine forest management in a mixed forest,Hokkaido, Japan: Guidelines for management interventions and evaluation of cover changes

In this study, we identified the distribution characteristics of a mixed forest of coniferous and broad-leaved trees (a typical forest type in Hokkaido, Japan) using landscape metrics and topographic factors, and attempted to apply this knowledge to examine forest management. This approach provides a new perspective (i.e., the landscape structure) on forest management, which traditionally has been determined on the basis of individual forest stands. We first created a cover type map of the study area by means of aerial photo interpretation. The characteristics of each cover type identified from the photographs were determined using landscape metrics for each cover class. We digitized a forest administrative map (1:20,000 scale) using 20-m contours, and imported this into GIS software to produce a terrain model; on this model, we overlaid the cover types. Our examination of landscape metrics showed that most of the natural forest could be managed similarly. However, our examination of topographic characteristics revealed exceptions (e.g., areas that are difficult to regenerate) that will require particular attention when managing the natural forest. Based on the information we obtained, we proposed a guideline for sustainable forest management. From the land cover map, we proposed an “improved” cover type map to illustrate the development of a high growing stock of forest based on forest management. We compared the current cover map with the “improved” cover map and demonstrated that the improved form would have more significant effects on fauna that do not recognize differences in the proportion of the dominant species types than on those that can recognize these differences. Our results show how the information obtained using landscape metrics and terrain models is an essential tool for various stages of forest management planning.