Dynamic responsive characteristics of nailed plywood–timber joints under harmonic vibrations

Dynamic tests of nailed plywood–timber joints are conducted under harmonic vibrations from 2 to 7 Hz. The principal results are as follows: under dynamic loading, nailed plywood–timber joints may break in low-cyclic bending fatigue failure of nails besides the other failure modes typical under static loading. The dynamic response of nailed plywood–timber joints is clearly dependent upon both the input frequency and the acceleration. These responsive characteristics arise from the nonlinear load–slip relationships and the characteristic cyclic stiffness degradation of nailed joints; that is, the cyclic degradation of the equivalent linear stiffness decreases the resonant frequencies of the same joints, which results in a transition of dynamic responses. It indicates that frequency components of seismic waves resonant to the frequencies corresponding to safety-limit stiffness of nailed joints may lead them to critical failures, even if the accelerations do not exceed the accelerations equivalent to the static damage-limit resistance.     

Fixed–fixed flexural vibration testing method of actual-size bars for timber guardrails

Resonance frequencies of bars with various types of end supports were examined in terms of flexural vibration. Sugi (Japanese cedar, Cryptomeria japonica D. Don) was used for the specimens. Small rectangular bars with dimensions of 25?mm (R)?×?5?mm (T)?×?300?mm (L), small round bars of 25?mm in diameter and 250?mm in length, actual-size rectangular bars with the dimensions of 45?mm (R)?×?95?mm (T)?×?1500?mm (L) and actual-size round bars of 180?mm in diameter and 2000?mm in length were made. Varying compression stress was applied to the parts around both ends of test specimen, whereupon flexural vibration tests were performed. The measured resonance frequency rose rapidly early in the increasing compression load process and was nearly stable for the larger compression load. The significant increases in the resonance frequency for round bars are thought to be derived from the wide area between the round bar and jig. It is necessary to compare the resonance frequency of a bar tightly fixed to a post with that of the same bar loosely fixed to the post.     

Three-dimensional inversion of knot defects recognition in timber cutting

The comprehensive utilization of wood is the main goal of log cutting,but knot defects increase the difficulty of rationally optimizing cutting.Due to the lack of real shape data of knot defects in logs,it is difficult for detection methods to establish a correlation between signal and defect morphology.An image-processing method is proposed for knot inversion based on distance regularized level set segmentation(DRLSE) and spatial vertex clustering,and with the inversion of the defects existing ...     

The non‐timber value of northern Swedish forests

For the forests in the county of Västerbotten in northern Sweden, this study attempts to quantify the non‐timber value arisen from on‐site consumptive use (berry‐ and mushroom‐picking), on‐site non‐consumptive use (hiking, camping, etc.), and off‐site visual experience. The contingent valuation method (CVM) was applied in a mail survey for obtaining empirical data. A follow‐up survey was also conducted in order to get knowledge about the representativeness of the respondents to the CVM survey. The results indicated that the non‐timber value accounted for a considerable portion of the total forest value. On‐site consumptive use was more valuable to rural people than to urban, while on‐site non‐consumptive use was more valuable to urban people. Taken together, these on‐site use values—which to a large extent depend on the Right of Common Access—accounted for two‐thirds of the non‐timber value. The value of the off‐site visual experience thus accounted for one‐third of the non‐timber value.     

Environmentally sound timber extracting techniques for small tree harvesting

Forestcontractors,loggersandengineershavebeenpayingahighattentiontotimberextractionoperationssince1990's.Sincetimber-extractingoperationproducesthehighestproportionofoperationcosts,largestareadisturbedandmostresidualstandsdamagedamongalloperationsofsmalltreeharvesting,manytechniquesweredevelopedtomeettherequirementsoftimberextractioninsmalltreeharvesting.Animalskidding13Animalskidding,oneoftimberextractionmethods,usessomespecialdevicessuchassledgesandcarriagesasshowninFig.1toreducetheresistanc…     

Multi-storey timber construction and bioeconomy – barriers and opportunities

Multi-storey timber construction has been developed and promoted in Finland since the 1990s. Despite these efforts, the share of timber frames in multi-storey construction has remained very low. Construction business is also very resource intensive and accounts for a large share of greenhouse gas emissions. Increasing the use of renewable materials, mainly wood, in buildings, could make construction more sustainable and a part of bioeconomy. This study aimed at identifying barriers to the adoption of multi-storey timber construction, ways in which wood could compete with established solutions and possibilities for partly integrating construction into bioeconomy. Based on 18 interviews of representatives from the entire value chain, this study presents insights into introducing new solutions into a conservative field. Our results indicate that multi-storey timber construction could offer competitive solutions for more sustainable construction, even though barriers to its adoption still exist.     

Predicting site productivity of the timber tree Pterocarpus angolensis§

Pterocarpus angolensis is an important timber tree of the miombo woodlands of sub-Saharan Africa. The species only grows in natural mixed forests and little is known about is productivity potential. This study aimed at investigating productivity of P. angolensis on a local scale in Namibia and Angola and on a regional scale in southern Africa. The most commonly accepted productivity indicator is stem diameter increment and this was used to study productivity at a regional scale. Indicators of productivity used at the local scale were basal area, proportional basal area and site form, which were derived from 217 forest inventory plots in Namibia and Angola. The productivity measures were modelled with abiotic site factors; biotic factors were added for the local scale. Results indicated that the most consistent site factors at local and regional scale were not related to climate but to forest cover, with the species having a competitive advantage in more open forests. Mean annual diameter increment in the open forests of Namibia was 0.51 cm after 50 years. Boosted regression tree models at a local scale showed that species presence can be modelled more successfully than species basal area, proportional basal area (correlation of 0.72 vs 0.56 and 0.45, respectively) and site form. The sites with the highest productivity of P. angolensis at the local scale had a temperature seasonality below 34.5 °C, a slope of less than 1.5°, tree cover less than 20% and stand basal area higher than 9 m² ha^?1. The results can assist in establishing a site-dependent growth model for the species and direct forest and fire management towards the most productive areas.     

How to improve the marketing of timber in France?

Large forest estates actively participate in the marketing of timber in France. However, the marketing of wood from private and public large forest estates (over 25 ha) could be improved by better managing price risk in multiannual supply contracts of the timber industry: creation of compensation funds for forest owners or calls to financial markets linked to processed timber products for industrialists. But, the development of supply contracts does not mean that private or public auction procedures should be abandoned. Similarly, by supplementing “forest area development schemes”, it would be possible to increase the mobilisation of timber produced on small (1 to 10 ha) and medium (10 to 25 ha) forest estates: more forestry cooperatives or local forest agencies and a new timber pre-sale mode adapted to small forest estates are necessary (sales subject to the buyer's choice of purchasing standing timber or cut wood delivered to a depot by the seller).     

Predicting timber harvests from private forests—a utility maximisation approach

Forest owners’ values and the ownership structure of forest are changing continuously. One probable consequence of the current trends in Finland is that the significance of forest-related income will decrease, which may have a significant impact on the round wood supply. This study developed and demonstrated a new method, which allows policy makers to make forecasts on the future timber supply. The method is based on the assumed temporal changes in the distributions of the importance of different forest management goals. The distributions are converted into utility functions, generated separately for each forest holding. The utility functions are maximised, using heuristics, to obtain the optimal forest management plans for the holdings. The regional cutting budget is calculated by summing the removals of the optimal treatment schedules of stands over the whole area. The method was demonstrated by assuming four different scenarios for the forest management goals, in which the importance of net income from realised cuttings decreased by 0%, 25%, 50% or 100% in 60 years. The decrease was compensated for by an increased importance of the other goals, namely economic security, recreation, and nature values. The calculations were made with three different methods. Methods 1 and 2 derived the optimal plans directly for the whole 60-year period while Method 3 developed three consecutive 20-year plans. Method 2 assumed that the holding is sold or inherited once in 20 years with an abrupt change in the management goals. In Methods 1 and 3 the goals changed only gradually. The results were logical, indicating that the more the importance of net income decreases the lower the future timber supply will be.     

Loss function analysis of private forest owners’ timber price change expectations

Loss function analysis was introduced to timber market price analysis. Methods found in Bayesian statistical decision analysis were applied to expectations of market price changes. These were obtained from a forest owner survey conducted in Finland in 2009. Forecast errors of heterogeneous price expectations of the individual private forest owners were derived with observed price changes in six different timber price regions. The forecast errors were complemented with random number simulations to control for unobserved response heterogeneity. The properties and estimation of generalized loss functions – LIN-EX and flexible loss functions – allowing for asymmetry in individual forecast errors were introduced into the analysis. Estimation results for different price regions implied that forest owners’ perceived costs related to positive forecast errors of negative price changes that took place in 2009 were larger than those related to negative errors. This under-prediction vs. over-prediction asymmetry was large in some price regions. The forest owners exhibited an aversion to losses reflected in price expectations errors in the year 2009. The observed loss aversion means that forest owners were cautious in their selling decisions during periods of declining market prices. This has a negative impact on the recovery of slack timber markets.     

Application of single neuron adaptive PID controller during the process of timber drying

The paper presents a method of using single neuron adaptive PID control for adjusting system or servo system to implement timber drying process control, which combines the thought of parameter adaptive PID control and the character of neural network on exactly describing nonlinear and uncertainty dynamic process organically. The method implements functions of adaptive and self-leaming by adjusting weighting parameters. Adaptive neural network can make some output trail given hoping value to decouple in static state. The simulation result indicates the validity, veracity and robustness of the method used in the timber drying process     

The economics of timber supply: Does it pay to reduce harvest levels?

Sustained yield policies designed to ensure an even annual flow of timber harvests remain the most common approach to forest management on public lands in Canada. Such policies have been criticized on the environmental grounds that timber production is emphasized at the expense of other values, and on the economic grounds that policy-makers try to maximize the harvests level without regard for economic optimality (measured by whether or not revenues cover variable costs of production). In a case study from Northern Ontario, we used a spatially explicit harvest scheduling model to evaluate financial outputs for various scenarios, introducing different timber flow constraints, as well as varying utilization policies. We show that current policies do contribute to firms harvesting at uneconomic levels. More specifically, our results show that reducing harvest levels could increase firm profitability (measured in an increase in net revenues associated with harvesting operations). We estimate that to meet the annual allowable cut (AAC) of approximately 375,000 cubic metres (m³), the firm loses $500,000 annually (measured by the amount by which total harvesting costs exceed log values delivered at the mill). Reducing the target AAC to just under 300,000 m³ leads to a reversed situation, harvesting revenues now exceeding costs by $1.2 million annually. Dropping the even flow constraint leads to even higher annual profitability of $3.5 million, with the drawback that harvesting levels show significant variation over the 100-year planning period. Our results also show that the largest factor influencing the level of profitability is attributed to access costs (principally roading costs). In this case, other harvesting policies, such as utilization standards, may not be significant factors affecting costs in this region of Northern Ontario.     

Do multipurpose companion trees affect high value timber trees in a silvopastoral plantation system?

Establishment of native timber trees on deforested land may contribute to the livelihood of farmers, to improved ecosystem services and to increased greenhouse gas uptake. Here, we present a new silvopastoral planting design to assess species performance and interspecific competition or facilitation effects among native timber and multipurpose trees in Central America. Two timber species, Tabebuia rosea and Cedrela odorata, were established in three low-density planting regimes allowing combined tree and future livestock production: (1) solitary planting, (2) companion planting with Guazuma ulmifolia, and (3) companion planting with the nitrogen-fixing Gliricidia sepium. We quantified survival, growth and reforestation potential of the two timber species subjected to the different planting regimes for the first 2 years after establishment. Nitrogen concentration as well as stable nitrogen and carbon isotope composition (δ¹⁵N, δ¹³C) of leaves of the timber saplings were determined. T. rosea showed higher survival and better growth than C. odorata under varying environmental conditions (soil, concomitant vegetation). Performance of the timber saplings was unaffected by either companion species. Planting regimes had no effect on foliar nitrogen concentration and δ¹⁵N of the two timber species, although δ¹⁵N values indicated nitrogen fixation activity in G. sepium trees. Planting regimes affected foliar δ¹³C values in T. rosea. δ¹³C values were significantly higher in solitarily growing individuals, suggesting lower exposition to water stress conditions in saplings surrounded by companion species. As we found positively correlated growth traits among timber and multipurpose trees, a combined planting may benefit farmers by providing additional goods and services.     

Cost sharing for timber stand improvements: Inducement or crowding out of private investment?

Cost sharing has been widely used to encourage the management of privately owned forests. While there is evidence of its capacity to promote management activities, it still remains open whether cost sharing induces additional private investments or whether it substitutes public funds for private capital. This study re-examines the latter issue in the case of Finnish family forest owners' pre-commercial and restoration thinnings using data from a nation-wide survey (n = 3801). A two-step model of cost-share participation and stand improvements is used to account for the endogeneity of cost-share participation. Cost-share participation was related to personal assistance and clearly encouraged forest owners' engagement in and extent of stand improvements. The inducement or crowding out of private capital is analytically shown to depend on the relative magnitude of forest owners' response to cost-share incentives in each specific situation. In the present case evidence suggests that cost sharing has had an inducement effect on private investment. This is likely related to the advanced personal assistance that has promoted the knowledge of and participation in cost sharing. The findings suggest that cost sharing can be a useful component in a balanced policy mix especially when combined with informational instruments.     

Influence of growth stresses and material properties on distortion of sawn timber — numerical investigation

? The board distortion that occurs during the sawing and the drying process causes major problems in the utilisation of sawn timber. The distortion is highly influenced by parameters such as spiral grain angle, modulus of elasticity, shrinkage, growth stresses and sawing pattern.

? In this study a finite element simulation of log sawing and timber drying was performed to study how these parameters interact to affect board distortion. A total of 81 logs with different material combinations were simulated. From each simulated log four boards with different annual ring orientation were studied.

? The results showed that the elastic modulus, shrinkage coefficient and growth stresses had a large influence on the final bow and spring deformation. After sawing of the log into boards, the release of growth stresses was the main contributor to the bow and spring deformation. For boards with low modulus of elasticity, the bending distortion became larger than for the boards with high modulus of elasticity. The twist deformation was very small after sawing but increased significantly during drying of the boards. The results showed that spiral grain angle and the board location within the log were the main contributors to the twist deformation.

     

Spatial integration in the Nordic timber market: Long‐run equilibria and short‐run dynamics

This study presents an econometric analysis of the spatial integration of the Nordic timber market as reflected in timber prices. The statistical model is a vector autoregressive (VAR) model with cointegration. The degree of spatial integration is tested through a cointegration analysis and a complete identification of the statistical model's long‐run structure. When the results were interpreted in terms of factor price equalization and efficient commodity arbitrages, the Nordic markets were found to be strongly integrated. The pattern of interdependence is investigated through an analysis of the model's short‐run structure and interpreted in terms of Granger causality. Finland, and to some extent Sweden, were found to act as “price‐leaders” in the long run and Denmark and Norway were very sensitive to changes in timber prices in competing countries.     

Influence of moisture content on estimating Young’s modulus of full-scale timber using stress wave velocity

The effect of moisture content on the stress wave propagation velocity was investigated in order to estimate the Young’s modulus of full-scale timbers in an air-drying state using the measurement of stress wave propagation velocity above the fiber saturation point. Using Japanese cedar lumber, the velocity and the density under high-moisture condition and air-drying states were measured respectively; after measuring the modulus of elasticity in an air-drying state, the moisture content of each condition was measured. By performing numerical analysis on these data, the relationship between the moisture content and the rate of change of velocity of full-scale timbers was derived. This relationship was used to estimate the Young’s modulus of the timber in the air-drying state from the velocity in high-moisture condition. First, the velocity and the Young’s modulus in an air-drying state were estimated accurately from its density, moisture content and velocity under high-moisture condition. In cases where the density could not be measured, using the database of mechanical properties with the Monte Carlo simulation method, the Young’s modulus of the full-scale timber in an air-drying state might be estimated within 20% accuracy from its moisture content and velocity under high-moisture condition.     

Product diversification in South Africa’s commercial timber plantations: a way to mitigate investment risk

We used the portfolio method to examine how a forest company can lower investment risk by producing a mix of timber products. We derived optimum combinations of pine (Pinus patula) saw timber production and eucalypt (Eucalyptus grandis) pulpwood production at landscape level. Our results indicate that producing a product mix rather than a single product improves aggregated financial returns and lowers investment risk over multiple rotation periods. The optimum mixture depended on past timber price correlations for pulpwood and sawn timber in South Africa between 1980 and 2011. This ideal mixture is comprised of areal ratios of about 45% saw timber and 55% pulpwood. Our example shows how economic risk of a forest investment can be reduced by creating a portfolio of a number of products. The risk that an investor has to accept for each monetary unit that is expected in return can be reduced by over 40% when comparing the risk–return combinations of a pure pine saw-timber stand with that of a portfolio of forest products. The risk associated with the production can be reduced by 20% when growing a portfolio of products rather than eucalypt pulpwood only.     

The use of forest information in timber sales planning – a case study in a Swedish forest-owning company

Interactions between value-creating activities are vital to increasing product value. Information sharing is a cornerstone of such interactions. For a forest-owning company with the primary objective to be leading in selling roundwood to forest industries, it appears therefore crucial that the sales people within a forest company have up-to-date knowledge about the forest in planning their sales, and that the forest knowledge is presented in a format that is suitable for them. To investigate if this is the case, a study was conducted at Sveaskog, a large Swedish forest-owning company. Semi-structured interviews were conducted with respondents from different levels in the organization. The results show that most sales managers did not directly use the knowledge about the forests when planning their sales; instead, they relied on historical data and had low trust in the knowledge presented in the tactical forest plan. The study pinpoints the organizational obstacles for using forest information in sales planning. These obstacles need to be addressed if more sophisticated information made available through new technology is to be utilized.