Volume 7, numéro 2, january 1996

EN :

One part of the procedure for improvement of machinery performance criteria is a multi-objective algorithm for thinning regime optimization. A "relative centre mass" method is used as its basis with relative unit harvesting cost and total and/or merchantable (intermediate and final) cutting volume criteria. The problem of optimum density over time for even-aged, one-species stands is formulated as a nonlinear programming task. The number of cuttings, the intensity of the thinning, and the thinning intervals are defined simultaneously using a "random search" algorithm. The method is applied to pine stands growing in the Russian Northwest region.

EN :

In this paper a study is made of the semi-rigid and non-linear behaviour of nailed knee joints in timber frames. A numerical analysis is applied to the non-linear deformation of the joints. The solution is derived using the stiffness method of analysis in which the rotation of each nailed joint is modelled by a series of piece-wise linear relationships, based on the load-deformation characteristics of nailed joints laterally loaded in single shear. The stiffness matrix is corrected at each step, to allow for joint flexibility; and the short-term non-linear deformation of frames, up to ultimate load, is calculated. Experimental verification is made using knee joint specimens and 6 m span timber portals with nailed plywood knee joints. The test results confirm the applicability of the analysis.

EN :

Certain properties of continuously advancing planting machines restrict their speed, thereby limiting their capacities. The cycle time of the planting device is predetermined by the design and is therefore difficult to alter. It is easier to influence the cycle timeof the seedling feed system, especially by changing the technical properties of the seedlings. In the case of pneumatic feed systems, air flow and hose diameter are also important physical factors. In cases where the seedling is not delivered to the planting device when required, the device will have to wait, and there will be a corresponding fall in productivity.

Consequently, it would be advantageous if we could predict the likelihood of such a delay occurring. To be able to do this, we need to know the statistical distribution of the feed cycle times for different combinations of the physical variables. One hypothesis is that feed cycle times exhibit a chi-square distribution. If this is true, future work should focus on developing transformations between physical properties and statistical parameters.

EN :

This report summarizes the findings of an ergonomie evaluation of first lift manual pruning of Douglas fir under New Zealand plantation forestry conditions. Six subjects were each observed undertaking their normal work methods throughout their complete working day. Heart rate data were collected and analysed using several heart rate indices in order to determine the workload of first lift pruning. The average working heart rate was 112 bt.min"1 ± 10.6 (SD). Results indicate first lift pruning to be a moderate to heavy workload activity. The manual pruning work method may place severe pressures on the workers' tendons, related bones and nerves of the hand, wrist, and elbow. Alternative pruning methods may contain inherent health and safety risks which must be carefully considered by those involved in the occupation of professional tree pruning.

EN :

This study determines the impact of fewer water crossings on hauling and road construction costs in a case study situation, and demonstrates the ease and versatility of network analysis in the planning and analysis of forest roads. Using a fixed grid network and modification of a standard network analysis technique allows the solution of large networks in only a few seconds on a personal computer (486-33MHz). The removal of 15 out of a total of 38 culverts resulted in a haul cost increase of $20 068 (CAD) for 1.2 million m3 hauled. However, removal of the first 14 culverts only increased the haul cost by $5236. The road construction cost saving from not installing the culverts was estimated to be $75 000 if all 15 culverts were not installed or $70 000 if 14 culverts were not installed. The case study indicated that considerable savings are possible through better planning of forest roads, especially with the additional expenses required to mitigate environmental impacts.