Evaluation of Mechanical Properties of Cross-Laminated Timber with Different Lay-ups Using Japanese Larch

Japanese larch is one of the main plantation tree species in China.A lack of engineered wood products made by Japanese larch,however,limits its application in wood stnuctures.In this study,based on optimum process parameters,such as pressure(12 MPa),adhesive spread rate(200 g/m^(2))and adhesive(one-component polyurethane),the mechanical properties of Japanese larch-made cross-laminated timber(CLT)with different lay-ups were evaluated by means of the static method.Results of this study showed that variations in lay-ups significantly affected the mechanical properties of CLT.The strength and modulus of bending and parallel compression for CLT increased with the thickness of lumber,while that of bending,parallel compression and rolling shear all decreased with the number of layers.Thickness,layup orientation and the number of layers all had an impact on the strength of CLT.Failure modes obtained from numerical simulation were basically the same as those of experimental tests.There was also strong alignment between theoretical value and test value for effective bending stifness and shear stifness.Thus,the shear analogy method can be used to predict the mechanical properties of CLT effectively.This study proved great potential in using Japanese larch wood for manufacturing CLT due to its good mechanical properties.

Bending,Compression and Bonding Performance of Cross-Laminated Timber(CLT)Made from Malaysian Fast-Growing Timbers

This study investigated the bending,compression as well as the bonding performance of CLT panels made from fast-growing timber species,i.e.,Laran(Neolamarckia cadamba)and Batai(Paraserianthes falcataria).The variables studied were timber species(Laran and Batai),layers of lamination(3-layer and 5-layer),loading direction in bending(in-plane and out-of-plane),loading direction in compression(x-,y-,and z-axis)and different treatment conditions for bonding performance test.The desired outputs of this study were bending and compression properties(strength and stiffness)as well as bonding performance(block shear strength,wood failure percentage and delamination value).The bending and compression test were conducted according to EN16351:2015 and EN408:2012,respectively.On the other hand,the bonding performance test was determined by block shear and delamination test based on EN16351:2015 and EN14374:2004,respectively.Prior to block shear test,the samples were subjected to three different treatment conditions.The results showed that CLT made from 3-layer Laran timber,loaded at out-of-plane direction exhibited the highest bending properties.Contrarily,CLT made from 5-layered Batai timber,loaded at in-plane direction showed the lowest bending properties.Laran samples for compression loaded at x-axis exhibited the best compressive properties.Generally,Laran CLT showed greater bonding performance determined by shear test compared to Batai CLT for both 3-and 5-layer panels.On the contrary,delamination results showed that Batai CLT demonstrated better bonding performance compared to Laran CLT.In terms of bonding performance measured by wood failure percentage(WFP),most samples under various treatment conditions showed WFP≥80%except for samples under wet condition with WFP≤60%.

Comparative Study on Various Strength Parameters of Structural Elements Made from Cross-Laminated Timber

Cross laminated timber(CLT)is an innovative and environment friendly engineered timber product with superior structural performance.CLT offers strong resistance against both in-plane and out-of-plane loading.Hence,it is widely used as floors,roofs or wall elements.Considerable experimental research on CLT under various loading conditions has been done in the recent past.This article presents a comprehensive review of various design methods to determine basic mechanical properties such as tension,compression and rolling shear strength of CLT with primary focus on Norway spruce.All relevant experimental data available from existing literature were collated and consequently been used to evaluate the performance of various methods to design CLT structures.The comparison revealed that different methods show considerable variance in predicting the capacity of CLT panels due to the variation in timber species,which affects the corresponding mechanical properties of the lamella.In addition to species,rolling shear properties can also vary considerably depending on the type of experimental technique used for testing.A predictive model has also been proposed to correlate rolling shear strength obtained from shear analogy method to that obtained using planar shear.

Understanding the Impacts of Plant Capacities and Uncertainties on the Techno- Economic Analysis of Cross-Laminated Timber Production in the Southern U.S.

Understanding the economic feasibility of cross-laminated timber(CLT),an emerging and sustainable alternative to concrete and steel,is critical for the rapid expansion of the mass timber industry.However,previous studies on economic performance of CLT have not fully considered the variations in the feedstock,plant capacities,manu-facturing parameters,and capital and operating costs.This study fills this gap by developing a techno-economic analysis of producing CLT panels in the Southern United States.The effects of those variations on minimum sell-ing price(MSP)of CLT panels are explored by Monte Carlo simulation.The results show that,across all the plant capacities from 30,000 to 150,000 m^(3)/year,the MSP ranges from$345 to$609/m^(3) with a±6%–9%range caused by the variations in feedstocks,key manufacturing parameters,capital and operating cost.The MSP decreases sig-nificantly along the increasing capacities.A sensitivity analysis exhibits that the lumber price,lumber preparing loss,plant capacity,and the installed costs of layering and gluing,finishing,and miscellaneous,are the top driving factors to CLT MSP.Supported by Geographic Information System,this study also studies the transportation cost of delivering CLT to customers under three CLT demanding levels(1%,5%,15%).The results show that the trans-portation cost is 1%–8%of the MSP.Lower demanding level or higher plant capacity can increase the transporta-tion cost due to average longer delivering distance.When considering the delivered cost that sums MSP and transportation cost,larger plant capacity does not necessarily generate lower delivered cost.

Evaluation of the Out-of-Plane Shear Properties of Cross-Laminated Timber

The out-of-plane shear properties of cross-laminated timber(CLT)substantially influence the overall mechanical properties of CLT.Various testing methods and theories related to these properties have recently been developed.The effects of the number of layers(three and five layers)and testing method(short-span three-and four-point bending tests)on the out-of-plane shear properties of CLT were evaluated.The out-of-plane shear strength values were calculated based on different theories for comparison.The failure mode in the short-span four-point bending(FPB)method was mainly the rolling shear(RS)failure in the cross layers,indicating that the FPB method was appropriate to evaluate the RS strength of CLT.The out-of-plane shear capacity obtained using the three-point bending(TPB)method was higher than that tested by the FPB method.The testing methods significantly influenced the out-of-plane shear capacity of the three-layer specimens but not that of the five-layer specimens.With an increase in the number of layers,the out-of-plane shear strength of the specimens decreased by 24%.A linear correlation was found among the shear strength values obtained from different theories.

Analysis of Crack Expansion and Morphology of Cross-Laminated Timber Planar Shear Test

To describe the dynamic cracking process of the CLT vertical layer,the correlation between a load-displacement curve,specimen cracking,and planar shear failure mechanism of the CLT were explored.A three-point bending test and an improved planar shear test are used to evaluate the shear performance of the CLT.In this study,the load-displacement curve is recorded,the experimental part is synchronized with the video,the dynamic process of cracking of the vertical layer is observed and analyzed throughout the test.From the load-displacement curve,the image characteristics of the initial cracking and the sudden increase of the cracking of the specimen are summar-ized.The description results of the whole dynamic process of the CLT vertical layer cracking are analyzed by pla-nar shear strength value,cracking phenomenon,and azimuth angle of cracking surface.The main conclusions show that the three-point bending test and the improved plain shear test can be used to test the plain shear strength of the CLT,with a difference of only 5.7%.The original crack and the new crack expansion account for 18.9%and 81.1%of the main cracking surface,respectively.And the vertical layer of the CLT specimen under three-point bending has three cracking morphologies,such as radial shake,ring shake,neither along with the radial shake nor along with the ring shake.The azimuth angle of the cracking surface of the CLT vertical layer under planar shear is quite consistent with the first main plane azimuth of the vertical layer of the CLT specimens under the three-point bending test and the shearing test.The shape in the cracking direction of the left half-span or the right half-span of the vertical layer of the specimen is similar to the Chinese character eight.

Mechanical Experimental Study on Tensile Bolted Connections of Cross-laminated Timber

In order to explore a kind of high-strength,earthquake-resistant,eco-nomical and suitable connection,4 groups of cross-laminated timber wall-to-floor and wall-to-wall bolted connections were tested under monotonic and cyclic load-ing.The defommation characteristics and failure modes of the cross-laminated tim-ber wall-to-floor and wall-to-wall bolted connections were exploited.Load-slip curves,bearing capacity,yielding point,stiffness and ductility of each group of specimens were analyzed.The test results indicate that the loading process of cross-laminated timber bolted connections under tension can be categorized as five stages,namely the elastic stage,the slip stage,the embedding stage,the yield-ing stage and the ultimate stage.The ultimate tensile capacity of cross-laminated timber bolted wall-to-floor connections is 2.67 times that of the wall-to-wall bolted connections.Compared with cross-laminated timber self-tapping screwed connections,the ultimate tensile capacity of the cross-laminated timber wall-to-floor bolted connections is 2.70 times that of the self-tapping screwed connec-tions,and the ultimate tensile capacity of the cross-laminated timber wall-to-wall bolted connections is 3.83 times that of the self-tapping screwed connections.The crosslaminated timber bolted connections have larger yielding displacement and wider plastic range,and they are more energy dissipative and more ductile.Furthermore,the cost of the cross-laminated timber wall-to-floor bolted connec-tions is 46%that of the self-tapping screwed connections,while the cost of cross-laminated wall-to-wall bolted connections is 53%that of the self-screwed connections.

Test and Analysis of the Sound Insulation Performance of Four Types of Timber Structure Floors under Jumping Excitation

To improve the impact sound insulation performance of building floors and meet the objective requirements for living comfort of residents,in this article,three kinds of elastic cushion materials,Portuguese cork board,BGL insulation sound insulation foam board,and EPP polypropylene plastic foam board,are applied to the sound insulation of a light frame wood floor structure of the same bedroom and compared to the ordinary floor.This study uses the transfer function method and transient excitation method to measure the sound insulation,damping ratio,and elastic modulus of materials,as well as the sound insulation of the floor under the jumping excitation method of daily behavior.Through comparative analysis,the results and factors of improving the sound insulation performance of the floor are obtained,according to which three types of elastic cushion materials and the floor covering composed of them have higher vibration and noise reduction performance.Among them,the overall sound insulation performance of BGL board floor is the highest,followed by EPP board and cork board floor,and ordinary OSB floor is the lowest.Under the jumping excitation method,three floating floors can improve the impact sound insulation performance of the middle and low-frequency bands.

Structural Performance of Prefabricated Timber-Concrete Composite Floor Constructed Using Open Web Truss Joist Made of LVL Paraserianthes Falctaria

This paper investigates an open web truss joist (OWTJ) made of laminated veneer lumber (LVL) Paraserianthes falctaria as a prefabricated timber-concrete composite floor system. The four-point bending test showed that structural performances of the OWTJ, conventional composite floor (CCF), and prefabricated composite floor (PCF) were similar. Although composite action was not developed as no lateral deformation was observed at the shear connectors, installing a concrete slab above the OWTJ can slightly increase the ductility factor of the composite floor. Furthermore, a finite element model was developed, and the model proved to be suitable for simulating the structural performance of the composite floor.

大跨度齿板连接木桁架搁栅楼盖竖向振动性能试验研究

为研究齿板连接木桁架搁栅楼盖的人致振动响应,对12m跨度齿板连接木桁架搁栅楼盖振动性能进行了足尺试验研究,分析了横撑和隔墙对木楼盖振动特性、楼盖刚度的影响,分析了单人步行荷载和自由落体冲击荷载作用下木楼盖的振动响应。结果表明:木楼盖前三阶振型符合预期,单跨木楼盖的基本自振频率在8Hz以下,低于连跨形式木楼盖的基本自振频率;安装横撑和设置隔墙都可以增加木楼盖的前三阶频率;在不同位置安装横撑均可提高木楼盖的刚度,减小木楼盖的静态挠度,均匀安装4排横撑可将楼盖中心静态挠度降低47.5%;不同方向步行荷载激励下木楼盖的振动响应略有不同,纵向行走而致的振动响应较大,横向较小,安装隔墙后木楼盖中心的振动响应能降低40%左右;木楼盖的纵向振动传递大于横向和斜向两个方向,安装隔墙有助于木楼盖振动的传递。

正交胶合木楼板全尺寸耐火性能试验研究

开展全尺寸正交胶合木楼板在加载情况下的耐火性能试验,所测试的楼板整体厚度为175 mm,在楼板上方均布2.0 kN/m2的砝码进行加载。两块楼板分别采用耐热型聚氨酯(PUR)胶和普通PUR胶制作,并分别采用单层15 mm厚和双层12 mm厚的耐火石膏板进行防火保护。试验发现,对于采用耐热型PUR胶和15 mm厚耐火石膏板的试件,石膏板的脱落时间约为45~50 min,层板炭化后未发生明显的脱落现象;对于采用普通PUR胶和双层12 mm厚耐火石膏板的试件,第一层石膏板的脱落时间约为30 min,第二层石膏板的脱落时间约为60 min,层板炭化后发生了较明显的脱落现象,脱落时间发生在85~100 min。试验进行至121 min,两块楼板中心的竖向位移值分别为-25、-33 mm,楼板背火面整体完好,表面最高温升不超过2℃。结果表明,所测试的楼板试件在加载情况下的耐火极限不低于2.00 h。

江苏省康复医院木-混凝土混合结构体系设计与分析

江苏省康复医院项目采用了胶合木梁柱+正交胶合木(CLT)组合楼盖+混凝土框架结构体系,可充分发挥木材与混凝土材料各自的性能优势,此类新型结构体系在国内外较为少见。应用国内外设计标准与理论,并结合有限元分析方法,对该工程整体及构件开展各项设计与分析工作。系统介绍了整体结构性能、CLT组合楼盖的强度与舒适性、木结构的抗火设计以及BIM技术的应用等方面的内容与成果。

Cross-laminated Timber(CLT)in China:A State-of-the-Art

As a new type of green low-carbon engineered wood product,cross-laminated timber(CLT)is widely used in various types of wooden buildings in Europe and North America,and the number of high-rise wood construction is also increasing.Based on the introduction of the structural characteristics of the CLT and the development status of the CLT in developed countries,this paper focused on the review of the status of research and development of the CLT in China,with an emphasis on the breakthrough technologies of new bamboo-wood composite CLT developed.Finally,the prospects of the CLT in China were discussed.

木质组合梁抗弯性能试验研究

通过12根矩形截面梁、24根T型组合梁和6根工字型组合梁,共计42根木质梁试件的2点加载受弯试验,研究了木基结构板—矩形截面木搁栅组合梁的抗弯性能.结果表明,木质梁试件破坏前能产生较大的变形,最终破坏主要有4种模式:纯弯段腹板弯曲破坏、沿腹板顺纹方向劈裂破坏、弯剪区沿腹板截面高度剪切破坏和梁端部局部扭转.木质组合梁中连接翼缘与腹板的钉连接节点在梁受弯时滑移变形较小,因此其能有效地传递翼缘与腹板之间的组合作用.T型组合梁与矩形截面梁相比,刚度和承载力有明显增加,工字型组合梁与T型组合梁相比,受弯性能进一步提高.因此可按组合梁理论进行更加合理的木楼盖相关设计.

以杉木纵横交错层积材为基材的地热地板研制

以人工林杉木纵横交错排层积材为基材,采用网状导电节点连接与热熔胶(PUR)胶合制备地热地板,测定其导热效能、通电后温度变化、连续通电后的耐热干缩率以及耐湿膨胀率,并与杉木纵横交错层积材、径切板、弦切板进行比较。结果表明:地热地板通电1 h后板面平均温度达到29.8℃,连续通电72 h的耐热干缩率和80%湿度处理的耐湿膨胀率均可满足木质地板采暖国家标准的相关要求。杉木板材的纵横交错层积排列有效地提高了耐热干缩率和耐湿膨胀率,完全可以用作地热地板的基材,为低等级杉木在地热地板中的应用及高附加值产品开发提供了理论依据。

浅析森林认证对我国木地板出口企业的影响及对策

介绍了森林认证的现状,分析了开展森林认证对我国木地板出口企业的影响,指出了开展森林认证面临的问题,提出木地板出口企业自己建立木材原料基地、采用多种方式解决森林认证费用问题、市场调节与政策调节并举、健全我国木地板市场、保证交易规范等推动我国森林认证发展的建议。

现代木结构楼盖振动与控制研究进展

房屋建筑的宜居性和舒适性是目前研究热点之一,日益受到人们的关注。现代木结构具有绿色宜居、建筑工业化程度高等特点,应用广泛,然而由于木材质量轻、楼盖刚度偏低,往往会产生较大的振动,从而影响其舒适性,因此对木结构楼盖振动性能与控制指标开展研究非常必要。本文对现代木结构楼盖的振动与控制研究进行回顾总结,主要从振动性能与控制指标两个方面进行梳理;并对比国内外研究,分析现代木结构楼盖振动与控制的研究现状,总结归纳研究对象、研究方法、控制指标等内容。本文还对木结构的发展趋势进行了展望,为今后的研究方向与工程应用提供一定参考。

正交胶合木墙体-楼板角撑连接节点受火后受剪承载力计算方法

为研究正交胶合木(CLT)墙体-楼板角撑连接节点受火后受剪承载力计算方法,对自攻螺钉长度分别为60和80 mm的CLT墙体-楼板角撑连接节点进行了常温及受火后的受剪试验.基于CLT层板销轴类紧固件常温受剪承载力计算方法,考虑节点受火后钢销轴抗弯强度折减以及CLT层板有效持力截面减少,提出了节点受火后受剪承载力计算方法.结果表明,对于常温试件,将自攻螺钉长度由原来的60 mm增至80 mm,屈服荷载增加到原来的1.51倍,而延性系数则降为原来的0.77倍;对于受火20 min后的试件,自攻螺钉长度增加时,屈服荷载和延性系数几乎不变.根据该计算方法得到的受火后受剪承载力与试验结果吻合较好,从而验证了所提方法的正确性与适用性.

轻型木结构建筑楼盖隔声技术的研究进展

轻型木结构目前在国外应用广泛,在国内常用于中低层居住式建筑,其建筑楼盖的隔声问题关系到用户居住的生活质量。主要介绍了国内外轻型木结构建筑楼盖隔声技术的研究进展,提出加速行业标准制订工作,重视建筑楼盖隔声理论基础性研究和不同激励方式下的试验方法研究,运用层板复合材料、动力学和声学理论等进行隔声楼盖结构优化设计等提高我国轻型木结构建筑楼盖隔声技术的主要措施,对于提升我国木结构建筑行业楼盖隔声技术,更好满足用户居住舒适度具有现实意义。

地板生产企业向供需网企业转化的通路研究

复杂性以及对人类理性的反思是后现代社会学术界的一个热门话题,SDN理念及其管理模式将复杂性思想引入到对企业经营管理的研究中来。在对SDN及我国木地板行业生存现状分析的基础上,提出了我国木地板企业发展的方向,即向供需网企业转化。并进一步研究了木地板企业向SDN企业转化的通路选择。