Treesearch

This chapter presents a summary of the Wood and Timber Condition Assessment Manual. It focuses on current inspection techniques for decay detection and provides guidelines on the use of various non-destructive evaluation (NDE) methods in locating and defining areas of deterioration in timber bridge components and other civil structures.

Near infrared spectroscopy (NIRS) was used to study a set of Southern Yellow Pine boards exposed to natural weathering for different periods of exposure time. This non-destructive spectroscopic technique is a very powerful tool to predict the weathering of wood when used in combination with multivariate analysis (Principal Component Analysis, PCA, and Projection to Latent Structures, PLS). Absorbance spectra contained information about weathering behavior, and PLS models to predict exposure time were very strong, with the correlation coefficients above 0.9. These results, and the “non-destr...

This paper describes an effort to develop a global dynamic testing technique for evaluating the overall stiffness of timber bridge superstructures. A forced vibration method was used to measure the natural frequency of single-span timber bridges in the laboratory and field. An analytical model based on simple beam theory was proposed to represent the relationship between the first bending mode frequency and bridge stiffness (characterized as EI product). The results indicated that the forced vibration method has potential for quickly assessing superstructure stiffness of timber bridges,...

This study evaluated the potential of acoustic analysis as presorting criteria to identify warp-prone boards before kiln drying. Dimension lumber, 38 by 89 mm (nominal 2 by 4 in.) and 2.44 m (8 ft) long, sawn from open-grown small-diameter ponderosa pine trees, was acoustically tested lengthwise at green condition. Three acoustic properties (acoustic speed, rate of wave attenuation, and acoustic modulus of elasticity (MOE)) were then determined through waveform analysis. Boards were then kiln dried, and warp was measured immediately after drying and after equilibrating to about 13 percent...

Recent investigation of [alpha]-hydroxy 5–O–4-lignin model compounds by NMR indicates that the short-range 13C-1H correlations for the ring 2- and 6- carbons should be distinct in HSQC NMR spectra of softwood MWLs and possibly in guaiacyl-type synthetic lignins (DHPs). The levels of 5–O–4-type linkages have been reported to be on the order of 17% of C9 units for MWLs. A comparison of the aromatic spectral regions from the short-range 13C-1H correlation spectra of [alpha]-hydroxy 5–O–4- models and loblolly pine MWL suggests that 5–O–4- type units are either not present at the suggested...

It is well known that paper produced from mechanical-pulp-containing fiber furnish yellows upon exposure to light. Although the accelerated light-aging test method has been used to compare papers and predict long term performance, the reliability of the light-aging method has been questioned. Therefore, a method that can correctly predict a paper’s light stability is desirable. In this work, a new technique is proposed that is capable of ranking papers for their photoyellowing characteristic and is based upon the amount of the pulp-hydroquinone present. The technique entails quenching, by...

A new method for quantifying percentage wood failure of an adhesively bonded block-shear specimen has been developed. This method incorporates a laser displacement gage with an automated two-axis positioning system that functions as a highly sensitive profilometer. The failed specimen is continuously scanned across its width to obtain a surface failure profile. The laser is then moved incrementally along the length of the specimen and repeatedly scanned to obtain a three-dimensional digital profile of the surface. This digital profile can then be reconstructed and analyzed with appropriate...

In this study, recent developments in headspace gas chromatography (HSGC) are briefly reviewed. Several novel HSGC techniques developed recently are presented in detail. These techniques were developed using the unique characteristics of the headspace sampling process implemented in commercial HSGC systems and therefore can be easily applied in laboratory and industrial practices. These techniques greatly expand the capability of traditional HSGC from simply analysis of volatile species to the measurements of nonvolatile species in solid systems and their properties in aqueous systems. The...

Wood preservatives extend the useful service life of all wooden commodities used above ground and in ground contact, Over SO years ago, the USDA-Forest Products Lab established tests in a high decay and high termite hazard zone in southern Mississippi. During the last five decades, periodic reports have been issued by researchers located at the USDA-FPL, in Madison, WI, on the efficacy and performance of southern pine fence posts treated with a variety of wood preservatives. Since 1977, no report has been issued by the USDA-FPL on the performance of these various preservatives in southern...

In 1993, unseasoned pine posts were treated with groundline remedial treatment containing 3.1% copper hydroxide and 40% sodium tetraborate decahydrate (borax). The soundness of the posts was periodically evaluated using a push test. After 3.5, 6.5, and 10 years, sections were taken from two posts to determine retention of borax and copper hydroxide below ground to 36 cm (14 in.) above ground. By 3.5 years of exposure, all untreated control posts had failed. After 6.5 and 10 years, the remedially treated posts were generally sound at the groundline but most suffered top decay. Average borax...