论天然用材林采伐方式的合理选择

以鹤北林业局森林采伐资料为依据，分析了选择采伐方式的条件和采取的技术措施，达到因林因地科学选择采伐方式的目的。     

福建省国有林场采运工艺与技术探讨

文章对国有林场采集作业方式、装车和运材方式、工艺技术方案的选择进行了较深入的探讨。     

采伐小班(伐区)超证采伐现象剖析

伐区超证采伐和无证采伐是导致编限单位超限额采伐的主要原因,控制伐区超证采伐是保证限额采伐制度有效执行的关键措施之一。结合近年采伐限额执行情况检查的结果,对伐区超证采伐的类型、产生的原因、超证采伐量的确定等问题进行了探讨,并就如何控制伐区超证采伐提出了对策。     

Influence of knot area ratio on the bending strength of Canadian Douglas fir timber used in Japanese post and beam housing

A study was conducted to establish the engineering properties and the influence of knot area ratio (KAR)-based grading rules on the bending strength properties of full-size Canadian Douglas fir timber used in Japanese post and beam building construction. In-grade tests were conducted on lumber selected at random from coastal mills in British Columbia, Canada, that manufacture products for the Japanese post and beam housing market. Bending strength and modulus of elasticity test results and KAR-based out-turn information on the 105 × 105mm and 45 × 105mm specimens are presented in this article. The in-grade test results indicate that KAR-based grading rules can be successfully applied to Canadian Douglas fir timber to meet strength property requirements.     

基于IC卡技术的林木采伐限额管理计算机系统研究

论述了基于IC卡技术和计算机网络技术的县级林木采伐审批管理系统的网络结构、总体设计、系统功能，并附例证。     

Stochastic model for predicting the bending strength of glued-laminated timber based on the knot area ratio and localized MOE in lamina

The aim of this study was to develop a stochastic model for predicting the bending strength distribution of glued-laminated timber (GLT). The developed model required the localized modulus of elasticity (MOE) and tensile strengths of laminae as input properties. The tensile strength was estimated using a regression model based on the localized MOEs and knot area ratios (KAR) which were experimentally measured for lamina grades samples. The localized MOE was obtained using a machine stress-rated grader, and the localized KAR was determined using an image-processing system. The bending strength distributions in four types of GLTs were simulated using the developed GLT beam model; these four types included: (1) GLT beams without finger joints; (2) GLT beams with finger joints; (3) GLT beams with different lamina sizes; and (4) GLT beams with different combinations of lamina grades. The simulated bending strength distributions were compared with actual test data of 2.4 and 4.8 m-long GLTs. The Kolmogorov–Smirnov goodness-of-fit tests showed that all of the simulated bending strength distributions agreed well with the test data. Especially, good agreement was shown in the fifth percentile point estimate of bending strength with the difference of approximately 1%.     

2002年进口木材应如何打理

自国家实施天然林保护工程以来,由于木材资源逐年减少以及行业内外对木材市场供需缺口加剧扩大的预期判断,致使木材进口数量逐年飞涨:1999年为630.8万m3（已经比1981年增长了7.5倍）;2000年则为1361.2万m3;2001全年超过1500万m3。以上的统计数字仅为进口的各类原木,尚不含锯材、合板、单板和纸浆等。据统计,我国进口木材无论是数量或其总值都已列各种进口商     

Ecoeffective production of timber

Abstract

Development in surface mould growth on painted/unpainted wooden claddings and acting climatic factors were investigated over a period of 3 years. Eight wood substrates, including modified, preservative-treated and untreated wood, were tested in combination with three types of paint: (1) water-borne alkyd modified acrylic paint without fungicide; (2) solvent-borne alkyd paint without fungicide; and (3) ICP (internal comparison product). One set of samples was exposed unpainted. The samples were tested according to a modified version of EN 927-3. A logistic regression model was fitted to the data. The degree of mould growth varied with exposure time, coating typology, wood substrate, temperature and relative humidity. Exposure time and coating typology contributed most to the model. After 3 years of outdoor exposure unpainted panels and panels coated with solvent-borne paint without fungicide had more mould growth than panels coated with ICP and water-borne paint without fungicide. Unpainted oil/copper–organic preservative-treated claddings had higher resistance to mould growth than other unpainted wood substrates. Coated untreated pine and coated acetylated pine were more susceptible to mould growth than other coated wooden substrates.     

关于我国木材市场分析

本文就我国森林资源现状、东北国有林区市场状况、林口林木贸易情况、中俄木材贸易情况进 行了详细分析,阐明了我国木材市场的发展趋势,以供借鉴和参考。     

Structural health assessment of in situ timber: An interface between service life planning and timber engineering

Abstract

The in situ assessment of timber structures has gained considerable attention in recent years due to some unexpected failures of public buildings. The assessment of timber, however, has been used in the evaluation of historic structures for a number of years, and the methods employed have evolved from visual observation (which is still one of the most effective ways of evaluating in situ timber) to more sophisticated methods that use various physical phenomena such as stress-wave or X-ray energy attenuation. In the health assessment of timber, effects of biotic elements such as insects and fungi are of interest, which, of course, is always connected with the presence of water in wood. The structural assessment encompasses questions related to the structural integrity of in situ members and the performance of components and the system. The structural health assessment not only focuses on biotic elements but also attempts to quantify engineering properties of the material such as strength degradation, modulus of elasticity, loss of cross-section, extent of checks, and other quantitative parameters needed for subsequent evaluation of the structural system, frequently expressed as load-bearing capacity. Service life planning of a structure is a complex issue that is related not only to the materials but also the environment and the use of the structure. Assessment of the health and properties of existing timber elements yields a piece of information that is necessary but not sufficient for the service life estimate. In the evaluation of structural timber, a mere use of various assessment techniques is not sufficient and usually an involvement of disciplines such as wood anatomy, wood physics, and statistics is needed. A reliable estimate of the parameters of in situ timber requires careful planning of measurements (experiments) since the material is highly variable and any statement about the properties of an element or even the entire system must reflect the random character of the wood properties. This paper will summarize the state-of-the art methods used in the assessment of in situ timber and analyze the strengths and the weaknesses of selected methods. An attempt will be made to outline future directions in the development of in situ assessment methods.     

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.     

Non-destructive evaluation of checking in thermally modified timber

Non-destructive measurement techniques were used to study the characteristics of thermally modified timber (TMT), especially checking. Two non-destructive measurement techniques were evaluated: air-coupled ultrasound (ACU) and electrical impedance spectroscopy (EIS). In the studied TMT (N = 38), density and pith location in the cross-section were positively correlated with the number of checks in the cross-section. Several ultrasound signal features correlated with TMT characteristics, most strongly with number of checks. Severely checked samples and other samples were considered as two different classes of checking, and the potential of ultrasound for differentiating between the two classes was tested by using Bayesian classification method. The correct classification rate was 97 %. EIS parameters correlated with density and latewood content of TMT more strongly than the ACU parameters. Thus, for determination of checking and density or earlywood/latewood content, both EIS and ACU measurements are recommended.     

Withdrawal capacity of washers in bolted timber connections

Abstract

The European yield model (EYM) has been accepted to determine the load-carrying capacity of structural timber connections. However, experiments of bolted connections are still not in agreement with the EYM unless the additional bearing capacity offered by the washers is taken into account. This bearing capacity is depending on the compressive strength perpendicular to grain of the structural timber. Tests results carried out with M16 and M24 washers on solid and glued laminated timber are used to verify the reliability of three strength capacity predicting models, one of which is an analytical model while the other two are empirical. It was concluded that the analytical model is the superior one. This model should be incorporated in all new structural timber design code revisions.     

The global timber market: implications of changes in economic growth,timber supply,and technological trends

A partial equilibrium model was applied to the global forest sector in order to assess regional and global impacts of changes in economic growth, timber supply potentials, and technical trends. The model uses recursive price-endogenous linear programming and deals with eight geographical regions and 16 products. The base line projections of the model gave an average annual increase in global supply of industrial roundwood of 1.2% until the year 2010. The real price of sawlogs and sawnwood was found to remain approximately constant, whereas the prices of pulpwood and particles increased significantly during the first years, and then declined after the year 2000. The real prices of pulp and paper increased less than those of pulpwood and particles. The assumed variations in GDP growth rates had limited influence on quantities supplied and traded due to restricted timber supply potentials, but affected the real prices, especially of pulpwood and particles. Changes in the assumed timber supply potentials and technical change affected the real prices of pulpwood and particles significantly. Introduction of a price responsive timber supply also dampened the price peaks of pulpwood. Possible improvements of the methodology include empirical estimation of timber supply and of key parameters that determine capacity expansion, trade inertia, and technical changes.     

关于合理造材作业的几点探讨意见

本文论述了进入市场经济合理造材工作的重要意义;搞好合理造材工作的基本环节;量材设计是合理造材工作的关键环节;针对量材、造材作业提出了几点探讨性意见与建议。     

论木材生产物流管理的趋势

本文分析了木材生产物流管理状况，讨论了影响木材生产物流管理的主要因素，进而提出了木材生产物流管理的三大趋势。     

Revenue loss from legal timber in Indonesia

The link between forest revenue administration and under performance of revenues from legal timber has received little attention in the literature. This article analyzes revenues from the timber royalty and reforestation fund fee, two important forest non-tax revenues in Indonesia whose tropical forest has been under threat of extensive deforestation particularly from commercial timber logging. It shows that revenue realization does not reflect potential with two key findings: first, timber royalty revenues represent only 52% of their potential, and second, revenues from reforestation fund fee suggest a counter-intuitive pattern – revenue realization is 34% above its potential. We provide plausible explanations from the perspective related to features of revenue collection. We further consider policy relevance in terms of forest revenue administration.     

A three-dimensional paradigm of fiber orientation in timber

Knowledge of the three-dimensional orthogonal directions of wood material at any position within a tree is necessary for the understanding of strength reducing effects of knots and essential for the continuation of research in areas which relate small clear wood specimen behavior to the behavior of full size structural timber. A complete three-dimensional paradigm describing the geometry of knots and related fiber distortion, initially derived to predict the strength-reducing behavior of knots in structural timber of Norway Spruce with the finite element method, is presented in this article. Besides strength prediction analyses, it is believed that the paradigm may be useful in other areas of research on structural timber that are effected by fiber orientation, such as drying and form change of structural timber. The paradigm generates fiber orientation in any position within a log or lumber from assumed fiber patterns in planes parallel to the longitudinal direction of the original tree. Fiber patterns in the radial and tangential directions are derived from physical restraints related to fiber production within the annual increase surfaces of the tree and from theories of knot formation. The adaptability of the paradigm allows practically any softwood knot to be modeled with an accuracy that is limited only by input-data. The knot-axis may be non-linear, and the knot cross-section oval with its vertical and horizontal axis increasing from the pith of the stem at chosen rates. Spiral grain may also be included in the paradigm and vary with the annual growth layers. Investigations presented in this article showed that generated fiber orientations for Picea abies complied well with measured fiber distortions, and that the general trends of fiber orientation, explained by the applied knot formation theory, is reflected in the measured specimens. Received 12 May 1999