《建筑结构用木工字梁》国家标准的编制

作为《建筑结构用木工字梁》国家标准起草人,介绍标准的编制依据和原则,并对标准中木工字梁所用材料的要求、承载性能技术指标、检测方法、质量控制等主要技术内容以及附录进行解释和说明,为标准使用单位提供参考。     

单面木工压创床空载功率的检测分析

通过对金华市瑞隆木工机械厂等厂家生产的9台MB104D单面木工压创床空载功率的实测，得到了单面木工压创床空载功率占额定功率的比值，并对该类机床产生空载功率的原因进行了分析。这些研究为设计者提供了确定单面木工压创床空载功率的可靠数据，同时也为今后制定相关标准提供了理论依据，有利于木工机床的节能降耗。     

木工刨床的空转噪声及对人与环境的影响

本文从人一机一环境系统角度出发，以ＭＢ１０６Ａ型木工压刨床为例，通过对其空转噪声及机床操作者心率的实测，系统地研究了木工压刨床本身一些因素对木工压刨床空转噪声的影响；同时也研究了机床空转噪声与传播距离的关系；最后研究了木工压刨床噪声对机床操作者心率的影响。同时分析了噪声产生的机理，并进行了试验论证，最后建立了木工压刨床空转噪声的数学模型，从而为木工机床的研究与设计及人一机一环境系统工程的研究提供了依据。     

整体式板桥静力荷载试验及计算方法研究

基于新施行的《公路桥梁承载能力检测评定规程》(JTG/T J21-2011),对整体式板桥进行静力荷载试验研究,利用桥梁结构专用分析软件Midas civil建立该整体式板桥的空间板单元模型,对静力荷载试验进行模拟,并将实测挠度、应力值和荷载横向分布系数与计算值进行对比分析。分析结果表明,该桥能够满足公路-Ⅰ级汽车荷载的使用要求;实测荷载横向分布系数与理论计算荷载横向分布系数相一致,且刚接板梁法计算值略大于有限元法计算值,设计时若按照简化刚接板梁法计算荷载横向分布系数偏于安全。     

重组竹工字梁抗弯特性研究及模拟分析

开展了6根腹板与翼缘板之间采用异氰酸酯胶黏剂胶接和螺栓连接的重组竹工字梁抗弯试验研究,考察重组竹工字梁抗弯承载力特性和破坏模式。试验表明:重组竹工字梁的破坏模式为腹板受拉区撕裂破坏;随着荷载的增加,截面各部位应变发展迅速,尤其是腹板边缘处应变发展最快,首先进入塑性变形并发生撕裂破坏;继续加载,该裂纹发生纵向延伸,逐渐形成通缝,并且螺栓连接处出现撕裂。此时,试件两端上、下翼缘变形明显小于腹板边缘处,翼缘和腹板之间变形极其不协调,上翼板下端与腹板上边缘发生脱胶现象,说明腹板和翼缘连接处的剪应力传递效果不佳,影响了构件的刚度和承载力。重组竹工字梁破坏时挠度较大,工字梁的受力变形明显,6根试验工字梁的延性系数为6.0~9.0,说明重组竹工字梁的延性较好,并且工字梁的设计控制因素是变形而不是承载力。进行重组竹工字梁抗弯特性的非线性有限元模拟,分析得到的工字梁荷载-位移曲线与试验结果吻合较好,工字梁的变形及应力分布特征均与试验相一致。     

现代木工刀具材料与展望

介绍了构成木工刀具材料的各种物质的化学成分及其物理力学性能、刀具材料新品种、新牌号，以及刀具材料与被切工件在物理、力学和化学性质匹配方面的重要性，并对未来木工刀具材料的发展提出预测和展望。     

分离刚度法在单向竹篾积成胶合板机械性质测试中的应用研究

介绍了一种实用的材料机械性质测试方法-分离刚度法，用该方法实测了造船工业用的单向竹蔑积成胶合板的弯曲刚度与横向剪切刚度，对单向竹蔑积成胶合板梁弯曲变形的有限元计算与实测基本吻合的事实说明，分离刚度法的测试结果是可靠的。     

碳纤维增强重组竹梁的极限挠度计算方法

重组竹力学性能优于木材,非常适用于装配式梁柱结构。重组竹抗压强度高于普通混凝土材料,受压应力-应变关系非线性特征明显,但其弹性模量仅为混凝土弹性模量的1/2左右。采用碳纤维(CFRP)增强重组竹梁可充分利用重组竹的抗压性能,提高梁的承载能力,但其非线性变形更加显著。考虑重组竹的受压非线性本构关系,提出计算梁极限挠度的弹性理论修正计算方法。该方法将梁简化为带塑性铰的杆件,假设非线性变形仅发生在塑性铰区域,杆件其余部分始终处于弹性工作状态,将梁的变形分为弹性变形与塑性变形。通过截面应变分析,得到塑性变形的计算公式,进而得到CFRP增强重组竹梁的非线性变形计算公式。CFRP增强重组竹梁的四点弯曲试验表明,所提出的计算方法具有足够的精度。     

木工平刨床噪声产生机理分析与控制

通过对MB503型木工平刨床进行试验模态和空气动力学的分析，确定了木工平刨床的主要噪声源，并进行了实验验证。运用机械噪声控制的基本原理提出了减振降噪措施，试验证明，采用这些减振降噪措施后，木工平刨床的空转噪声有了显著下降。     

基于静态弯曲性能的木质工字梁设计计算方法探讨

参照钢质工字梁静态弯曲理论,对木质工字梁（IJ）的“荷载一位移”曲线、IJ正应力理论计算值与实测值、IJ整梁挠度理论计算值与实测值的对比分析,结果认定：1）钢质工字粱的静态弯曲理论计算公式,可用于IJ弹性段应力和挠度的分析计算;2）IJ整梁静态弯曲性能的分析计算时,应注意IJ上翼缘压缩特性和下翼缘拉伸特性的差异。     

Derivation and application of an equation for calculating shear modulus of three-ply laminated material beam from shear moduli of individual laminae

In a detailed study of the relation between the deflection caused by shear force and the constitution of a laminated material beam, we derived an equation for calculating the shear modulus of a laminated material beam from the shear moduli of individual laminae. The validity of the derived equation was investigated using crosslaminated wood beams made with five species. The calculated shear moduli parallel to the grain of face laminae ranged from 48.3 MPa to 351 MPa, while those perpendicular to the grain of face laminae ranged from 58.0 MPa to 350 MPa. The calculated shear moduli increased markedly with increasing shear modulus in a cross section of perpendicular-direction lamina of a cross-laminated wood beam. The calculated apparent modulus of elasticity (MOE) of cross-laminated wood beams agreed fairly well with the measured apparent MOE values. This fact indicated that the apparent MOE of cross-laminated wood beam was able to be calculated from the true MOE values and shear moduli of individual laminae. The percentage of deflection caused by shear force obtained from the calculated apparent MOE (Y _sc) was close to that obtained from the measured apparent MOE (Y _s) and there was a high correlation between both values. From the above results, it was concluded that the derived equation had high validity in calculation of shear modulus of a cross-laminated wood beam.     

Characterization of major,unused, and unvalued Indonesian wood species I. Dependencies of mechanical properties in transverse direction on the changes of moisture content and/or temperature

Mechanical property changes due to the moisture content (MC) and/or temperature changes were examined for 15 Indonesian wood species. A static bending test was carried out at 20°C, 65% relative humidity (air-dry), and water-saturated at 20°C (wet-20) and 80°C (wet-80). For individual test conditions, modulus of elasticity (MOE) and modulus of rupture (MOR) increased linearly with specific gravity regardless of wood species; however, maximum deflection did not correlate with specific gravity for any MC or temperature conditions. The relative values of MOE and MOR measured in wet-20 to air-dry conditions were variously affected from slightly to strongly depending on the wood species. However, the relative values always decreased markedly when saturated in water at 80°C, regardless of wood species. The relative MOE, MOR, and maximum deflection values due to the change in MC or MC and temperature combined were independent of specific gravity but may be dependent on wood type: softwood or hardwood.     

Bending creep performances of three-ply cross-laminated woods made with five species

To improve the performance of cross-laminated woods, 30 types of three-ply parallel-laminated and cross-laminated woods were prepared from five species with various densities and shear compliances in cross section, and their bending creep performances were investigated on the basis of our previous research in cross-laminated wood made with sugi (Japanese cedar). The creep deformation perpendicular to the grain was decreased by cross laminating. The creep deformation perpendicular to the grain of parallel-laminated woods (P_⊥ type), that perpendicular to the grain of face laminae of cross-laminated woods (C_⊥ type), and also that parallel to the grain of face laminae of cross-laminated woods (C_║ type) tended to decrease with increasing density of species used for perpendicular-direction lamina. It was found that the extent of the decrease was greater in creep deformation than in initial deformation. The degrees of anisotropy for both deformations of laminated wood were markedly decreased by cross laminating. The extent of the decrease was much greater in creep deformation than in initial deformation and considerably smaller in buna with higher density than in sugi with lower density. The measured values of initial deformation and creep deformation of C_⊥ type were almost equal to the calculated values obtained from the measured values of parallel-laminated woods, whereas the measured values of both deformations of C_║ type were much greater than their calculated values and increased markedly with increasing shear compliance in cross section of perpendicular-direction lamina used for core. The ratios of the average of measured values to the calculated value of C_║ type ranged from 1.05 (katsura) to 1.50 (sugi) in initial deformation and from 1.30 (katsura) to 3.69 (sugi) in creep deformation. This result can be explained as the effect of deflection caused by shear force.     

Shear fracture characterization of green-glued polyurethane wood adhesive bonds at various moisture and gluing conditions

Abstract

The shear fracture properties of green-glued one-component polyurethane (PUR) wood adhesive bonds subjected to kiln drying were investigated. The local shear strength and fracture energy of the wood adhesive bonds were determined from experimentally recorded complete shear stress versus deformation curves of the bond line. A stable test set-up and small specimens that were anti-symmetrically loaded were used in order to get a uniform and pure state of shear stress. Different moisture contents (MCs) and pressing times were investigated. The fracture properties of conventionally dry-glued wood adhesive bonds and of solid wood were used as reference. The results show that the fracture energy of green-glued bonds with PUR adhesive is dependent on the MC of wood and on the pressing time. The same fracture energy and strength can be obtained by green gluing as by dry gluing, but there seems to exist a maximum MC of sapwood, in the range between 78% and 160%, and a minimum pressing time, in the range between 3 h and 48 h, for which it can be achieved. Both dry- and green-glued polyurethane adhesive bonds were more ductile than solid wood.     

Quantitative Analysis on Measure Results by Resistograh for Wood Decay of Ancient Architecture

INTRODUCTION The main body of ancient architecture is wood construction in China, and the main bearing components of the buildings usually use timber, such as pillar, beam, purlin, crossbeam and rafter. Timber is a kind of biomaterial and will be damaged by fungal attack or insects after long time use, which will cause wood frames destroyed ultimately. Timber decay not only exists in its surface, but also usually begins with the inner of wood. It is therefore imperative to consider using …     

木材静曲蠕变成套测试系统的研发

为解决木材变湿蠕变测试普遍存在的环境参数(温湿度和风速)控制方式和控制精度不足、蠕变变形量测试灵敏度和精度不足、数据智能采集和处理以及系统安全防护不足等问题,在集成现有技术的基础上研发出一套木材蠕变测试系统。该系统包括环境气候箱、蠕变测试机架、木材蠕变变形量及干缩湿胀测试单元、荷载同时装卸单元、数据采集和处理单元、系统保障和防护单元6个部分。该系统可在温度为0~70℃、相对湿度为10%~98%、风速为0.3~5.6 m/s时对木材或木基材料的普通蠕变和机械吸附蠕变进行长时间稳定的测试、记录,蠕变变形量及木材厚度方向的干缩湿胀检测精度为±0.01 mm,数据采样间隔在1 s~24 h范围内可调。与现有木材蠕变测试系统相比,本系统在多参数自动同步获取、数据采样精度、运行稳定性、安全性和环境风速可调性等方面有独特优势。通过前期对木材112 d循环变湿蠕变量、干缩湿胀量及环境温湿度参数的观测和测试结果分析,证实该套检测系统可对木材的蠕变挠度、干缩湿胀量、环境温湿度等参数进行长期连续稳定的检测、记录和显示,所有测试指标均能达到设计预期。同时,由于该系统具有多参数协同检测和精度较高等特性,使得实测木材变湿蠕变比采用喷蒸变湿处理试件所获蠕变测试结果在局部地方存在明显差异,如吸湿过程中的木材静曲挠度并不都是反向减小,而是取决于吸湿速率和外荷载的竞争关系,从而为木材静曲变湿蠕变机理的揭示提供了有力证据。该系统的研制为精确可控变温变湿环境下木材蠕变机理的研究提供了新的平台。     

Twelve Elastic Constants of Betula platyphylla Suk.

Wood elastic constants are needed to describe the elastic behaviors of wood and be taken as an important design parameter for wood-based composite materials and structural materials. This paper clarified the relationships between compliance coefficients and engineering elastic constants combined with orthotropic properties of wood, and twelve elastic constants of Betula platyphylla Suk. were measured by electrical strain gauges. Spreading the adhesive quantity cannot be excessive or too little when the strain flakes were glued. If excessive, the glue layer was too thick which would influence the strain flakes?performance, and if too little, glues plastered were not firm, which could not accurately transmit the strain. Wood as an orthotropic material, its modulus of elasticity and poissons ratios are related by two formulas:μij /Ei =μji /Ej and μij < (Ei /Ej)1/2. The results showed that the elastic constants of Betula platyphylla Suk. measured by electrical strain gauges were accurate and reliable. The results of shear elastic modulus GTL and GLR show a high linear regression correlation coefficient (> 0.95) between the reciprocal of elastic modulus MOE-1 and the square of the ratio of depth to length (h/l)2, which indicate that shear modulus values measured were reliable by three point bending experiment.     

Tests for outdoor window profiles: 90° mortise tenon corner joints strength assessment

The research focuses on the assessment of the performances of glued laminated wood corner joints for outdoor window profiles applications, proposing a methodology to appreciate the strength of 90° tenon mortise corner joints. The rationale relies on the potential damage (i.e. breaking of the frame) that can be caused by poor glueing processes and/or typology of adhesives. There is a number of standards for assessment of wood-adhesive bonds for outdoor windows; however, there is a lack of specific standards related to glueing assessment for outdoor wood frames, which can take into account all the factors influencing the glueing quality. The proposed methodology was tested on red oak window profiles. A commercially available polyvinyl acetate-based adhesive was used for corner joints. Bending strength of 90° tenon mortise corner joints was measured and compared with maximum admissible loads on the frame to limit its deformations within admissible ranges. The test results show that the 90° tenon mortise corner joints strength exceeds the admissible load to preserve the functionality of the frame. In order to appreciate the influence of conditioning processes on adhesion, shear strength tests of the flatwise glued joint samples (bond lines of lamellae) were carried out after different conditioning processes.     

木材压缩改性技术研究进展

为改善速生材自身固有的缺陷,提升其利用价值,需对速生材进行强化改性处理。木材压缩改性技术作为一种木材物理强化改性方法,具有生产效率高、无化学污染和易于产业化生产等优点,是扩展速生材应用范围最具潜在商业价值的木材改性技术之一,已成为木材改性研究领域的前沿和热点。笔者在广泛阅读文献的基础上,对木材压缩强化改性方面的代表性成果进行了梳理和总结,主要从木材压缩改性类别、木材软化、压缩木定型、木材压缩工艺、压缩木材性能及应用等方面进行了深入广泛的论述。最后,基于木材压缩改性的应用现状,对压缩改性技术研究中存在的问题以及未来发展趋势进行了分析展望。木材压缩改性技术有必要在高效型木材压缩改性技术开发、复合型木材压缩改性技术开发和森林?压缩木价值链评估方面取得突破,这些突破对推动木材压缩改性技术向商业化发展以及实现压缩木的高附加值利用具有重大意义。