Mathematical growth and yield models were developed for the major plantation timber species, Cupressus lusitanica, growing in Munessa Shashemene State Forest Project (MSSFP), in Southwest Ethiopia, based on data from 106 temporary sample plots. Stand dominant height development was predicted by Schumacher's growth equation as a function of age and site index, defined as dominant height at reference age of 15 years. Initial diameter distributions of trees were generated using the Weibull probability density function with scale and shape parameters predicted as a function of stand parameters. Stand basal area for unthinned stands was predicted as a function of dominant height, stand age and number of stems using a modified Weibull growth equation. The basal area after thinning was simulated using a single tree diameter increment equation. The mid-diameters of each diameter class were incremented and added to the initial diameter values of each class for subsequent ages which when multiplied by class frequencies and summed gave the stand basal area. Thinnings were simulated using a power function. A compatible tree volume/taper estimation system which determined tree volume and taper was developed. The growth functions were integrated in a logical sequence, using the readily available and user friendly simple spreadsheet package, EXCEL, to produce a whole-stand distance simulation model (SIMCUP). This model also predicted final maincrop yield by size classes. Validation of the volume and diameter distribution models showed that the model (SIMUL) worked satisfactorily. Using SIMUL the effects of different levels of spacing, thinning frequency and thinning intensities on cumulative volume and sawlog volume were investigated. Experimental runs with the most frequently used thinning intensity (37.5% by stem number) at MSSFP showed that the current thinning intensity was too heavy and resulted not only in loss of cumulative volume but also merchantable volume. The cumulative volume of once, twice and three times thinned stands at the age of 25 years could be decreased by between 12.3%, 19.7% and 23% of the unthinned stand respectively. The highest merchantable sawlog volume was with no or one thinning at the age of 7 years with a rotation age of 25 years. In contrast by adopting a 25% thinning intensity the merchantable volume could be increased by between 20.4% to 10.7% relative to current yields for site index classes 27 to 12 and a stand with 1588 stems per hectare respectively. The highest merchantable sawlog volume per hectare to 15 cm top diameter was obtained at the spacing of 2.1 x 2. lm at the rotation age of 25 years The model is intended to promote silvicultural management of C. lusitanica stands in MSSFP, Southwest Ethiopia. Using SIMCUP, different levels of spacing, time of first thinning and alternative thinning intensities have been investigated and appropriate silvicultural measures suggested to achieve higher merchantable volume per hectare.

Thesis (Ph. D.)--Columbia University, 1945. / Vita. Bibliography: p. 71-75.

Thesis (M.S.) in Forestry--University of Maine, 2001. / Includes vita. Includes bibliographical references (leaves 80-84).

To improve the performance of the conventional nail laminated bridge deck, three generations of innovative decks have been developed during the last three decades: (a) the stress laminated wood deck, (b) the stressed log bridge, and (c) the grout laminated wood deck. The grout laminated wood deck, the most recent wood deck, consists of trimmed logs interconnected with internal grout cylinders, in compression or tension. Previous research has shown that the grout cylinders have superior load distribution characteristics, but the cost of trimming the treated logs was found to be relatively high. Recently, research has been conducted to develop the next generation of the bridge wood decks, called the anchored log decks. The anchored log deck, meant for use as decking of steel girder bridges, consists of untrimmed discarded utility timber poles which have been treated with preservatives. The logs are held together by means of unstressed transverse proprietary Cintec anchors. The anchors consist of stainless steel rods encased in grout cylinders. Panels, each comprising of 5 to 6 logs, are preassembled to fit on a flatbed trailer for shipping. The smooth wearing surface over the log deck is provided by longitudinal sawn timber planks, with high-density foam filling the gap between the logs and the planks. The panels are inter-connected through inclined anchors passing through adjacent logs. At the University of Manitoba, an anchored log deck with five preassembled panels was constructed and tested to failure at several locations under both static and fatigue loads. The test results have shown that anchored log decks have the potential of being economical preassembled decks for steel girder bridges.

An experimental program was carried out to investigate the effect of post-tensioning on timber beams and the performance of timber bridge decks with post-tensioned stringers. The experimental program contains three phases. As part of the first phase, twenty shear tests were performed to determine the ultimate capacity of lag screws that could be used in the post-tensioning process. Results showed that six lag screws with a diameter of 12.7 mm were adequate for the anchorage system. The second phase included testing 22 full scale timber beams. Six beams were control without any reinforcement. The remaining sixteen beams were post-tensioned with either draped or straight carbon fiber reinforced polymer (CFRP) tendons (Groups CD and C) or steel cables (Groups SD with draped cables and S with straight cables).The results revealed that the strength and the stiffness for Group CD were increased on average by 70% and 10%, respectively, while the strength for Group C was increased on average by 56%. In contrast, the strength and the stiffness for Group SD were increased on average by 45% and 4%, respectively, while the strength for Group S was increased on average by 49%. The bending strength of the post-tensioned timber beams was predicted using analytical model. The third phase of the research included the construction of four timber bridge decks: control deck (BD-CO), deck with stringers post-tensioned with draped CFRP tendons (BD-DC), deck with stringers post-tensioned with draped steel tendons (BD-DS), and a deck with stringers strengthened with near-surface mounted glass fibre-reinforced polymer bars (NSM-GFRP) referred to as BD-G. Post-tensioning the stringers of BD-DS and the stringers of BD-DC increased the apparent stiffness on average by 2% and 3%, respectively. In contrast, the apparent stiffness for the stringers of BD-G increased on average by 29%. SECAN program was used to analyze the four timber bridge decks. It was found that SECAN can predict the behaviour of the timber bridge deck based on the experimental stiffness of the individual tests. Cost analysis was done for the three strengthening techniques. It was found that post-tensioning stringers with draped steel cables can be cost effective.

No description available.

No description available.

Thesis (M. Eng.)--New South Wales Institute of Technology, 1985.

Thesis (Ph. D.)--Columbia University, 1945. / Vita. Bibliography: p. 71-75.

Thesis (M.S.)--University of California, May 1925. / Maps accompanied by sheets with description. Description based on print version record. Bibliography: p. i-iii at end.