Treesearch

This study was conducted to evaluate the accuracy and reliability of several stress-wave devices widely used for locating deteriorated areas in timber bridge members. Bridge components containing different levels of natural decay were tested using various devices. The specimens were then sawn (along their length) into slabs to expose their interior condition. The interior faces of these slabs were inspected visually and with a resistance micro-drill to confirm if deterioration was present. On the basis of these tests, we conclude that all four devices evaluated in this study can successfull...

Opportunities for use of northeastern species such as balsam fir, eastern spruce, eastern hemlock, and red maple could be improved if these species could be adequately penetrated with preservatives and subsequently shown to be durable in outdoor exposures. In this study, specimens cut from lumber of northeastern species were pressure-treated with either chromated copper arsenate type C (CCA-C), ammoniacal copper citrate (CC), alkaline copper quat type C (ACQ-C), or copper azole type A (CBA-A). Treatability was assessed by measuring retention and penetration of preservative. The results...

The complex of xylan and iodine and its formation in a solution of xylan, CaCl2, and I2 + KI was investigated by UV/Vis, second-derivative UV/Vis, and Raman spectroscopy. The complex forms only at very high concentrations of CaCl2, suggesting that when the water available in the solution is not sufficient to fully hydrate the calcium cation the chelation with the hydroxyl groups of the xylan can occur. The electronic spectra indicate that iodine is present in the form of three linear polyiodides I9 3-, I11 3-, and I13 3- structures, which the Raman spectra show to be linear aggregates of...

The softwood lumber industry in the United States and Canada consists of about 1,067 sawmills. In 2005 these sawmills had a combined capacity of 189 million m3 (80 × 109 bf). In 2004, they employed about 99,000 people and produced 172 million m3 (nominal) (73.0 × 109 bf) of lumber. In the process, they consumed about 280 million m3 (9.9 × 109 ft3) of timber. Employee productivity was near 2,125 m3 (900,000 bf) per worker per year for dimension and stud mills but about half that for board, timber, and specialty mills. Average saw log size varied from 42 cm (16.6 in.) in British Columbia to...

The primary means of inspecting buildings and other structures is to evaluate each structure member individually. This is a time-consuming and expensive process, particularly if sheathing or other covering materials must be removed to access the structural members. The objective of this study was to determine if a low frequency vibration method could be used to effectively assess the structural performance of wood floors as component systems. Twelve wood floors were constructed with solid sawn wood joists in the laboratory and tested with both vibration and static load methods. The results...

An early focus on structural use of processed rather than round timber resulted in an underestimation of the structural advantages of retaining the natural form of small-diameter round timber. In the round and tapered form, timbers are not susceptible to the strength-reducing effects of diving grain and exposed juvenile wood. Fiber continuity around knots on the surface of a debarked log rarely exhibits the stress concentration and fracture propagation commonly seen in disrupted grain around knots in lumber. Symmetry of material properties about the centroidal axis in a round timber...

With the need for evaluating the utilization of veneer peeler log cores in higher value products and the increasing importance of utilizing round timbers in poles, posts, stakes, and building construction components, we conducted a cooperative project to verify the suitability of stress wave nondestructive evaluation techniques for assessing peeler cores and some mechanical properties of lumber that might be derived from peeler cores. Longitudinal stress waves were used to evaluate peeler cores from 111 Douglas-fir stems. Supplementary dynamic and static tests were then conducted on 2 by 4...

Thermal conductivity is a very important parameter in determining heat transfer rate and is required for developing of drying models and in industrial operations such as adhesive cure rate. Geometric models for predicting softwood thermal conductivity in the radial and tangential directions were generated in this study based on obervation and measurements of wood structure. Modeling effective thermal conductivity in the radial and tangential directions is helpful in understanding the heat transfer mechanism in the two directions and predicting the values for a wide range of moisture...

Fully oxidized [alpha]-AlIIIW12O405-(1ox), and one-electron-reduced [alpha]-AlIIIW12O406-(1red), are well-behaved (stable and free of ion pairing) over a wide range of pH and ionic-strength values at room temperature in water. Having established this, 27Al NMR spectroscopy is used to measure rates of electron exchange between 1ox (27Al NMR: 72.2 ppm relative to Al(H2O)63+; [upsilon]1/2 = 0.77 Hz) and 1red (74.1 ppm; [upsilon]1/2 = 0.76 Hz). Bimolecular rate constants, k, are obtained from line broadening in 27Al NMR signals as ionic strength, [mu], is increased by addition of NaCl at the...

Nano-sized particles may be small, but for our industry they offer huge potential. Nanotechnology represents a major opportunity for the forest products industry to develop new products, substantially reduce processing costs, and open new markets in the coming decades.