Treesearch

The standardized bridge design aides in this publication are for superstructures manufactured with glued-laminated timber (glulam) that was pressure-treated with preservatives. Four superstructure types are included: two longitudinal (slab-type) deck systems and two transverse deck systems resting on either glulam or steel girders. Simple span designs for both single- and multiple-lane bridges that conform to the American Association of State Highway Transportation Officials (AASHTO)–Load and Resistance Factor Design (LRFD) bridge design specifications are included.

Recent developments in image processing play a significant role in identifying and classifying features on ground penetrating radar (GPR) radargrams. Two groups of timber specimens were examined in this study. The first group comprised laboratory prepared Douglas-fir (Pseudotsuga menziesii) timber sections with inserts of known internal characteristics. The second group comprised timber girders salvaged from timber bridges on historic Route 66 that had been exposed to weather for more than 80 years. A subsurface interface radar system with a 2-GHz palm antenna was used to scan these two...

Ecofriendly materials such as polylactic acid (PLA) and cellulose nanocrystals (CNCs) are widely sought as potential substitute for petrochemical-based plastics. Uniform dispersion of cellulose nanocrystals in polymer matrices has inhibited their wide-spread application. In this study the influence of masterbatch preparation techniques on molecular structure, melt strength, rheological and dynamic mechanical properties of nanocomposite were systematically analyzed. Film casting and spin-coating methods were used to prepare masterbatches. Nanocomposites were obtained by masterbatch dilution...

Lignin, a byproduct from the chemical processing of lignocellulosic biomass, is a polyphenolic compound that has potential as a partial phenol substitute in phenolic adhesive formulations. In this study, HBr and HI were used as reagents to demethylate an alkali lignin (AL) to increase its hydroxyl content and thereby enhance its reactivity for the preparation of phenolic resins. Analyses by FT-IR, 1H-NMR and 2D-NMR(HSQC) demonstrated both a decrease in methoxyl groups and an increase in hydroxyl groups for each demethylated lignin (DL). In addition, the molar amounts of phenolic hydroxyls,...

Early illustrations of juvenile wood in hard pines have depicted a central core of wood, varying little by diameter or cambial age, to be nested within mature wood tapering to the upper portion of the stem; other depictions show greater complexity in attributing the variability of this central core of wood with its proximity to the crown and/or actual maturity of the tree when the wood was formed. The present discussion addresses the degree to which different representations of juvenile wood (corewood) are applicable to mature longleaf pine (Pinus palustris Mill.) trees. Wood property maps...

Cross Laminated Timber (CLT) is part of a new generation of engineered wood products that are now widespread across Europe, Australia, and Canada. As this trend is now growing in the United States, manufacturers are looking to expand the use of CLT into the North American market, which includes states located in the southeastern U.S. As this region is known to have an increased risk of termite attack, standards should be developed to evaluate termite damage on CLT products prior to extensive use of the product in this region. However, existing standard test methods cannot be applied...

In this report, wooden members of sizes typically used in bridge construction are examined using x-ray computerized tomography (CT) to determine the presence of internal decay. This report is part of an overall study in which Douglas-fir (Pseudotsuga menziesii) glue-laminated (glulam) beams and solid sawn timbers were inoculated with brown rot fungus, Fomitopsis pinicola, and exposed to aboveground conditions approximately 25 miles (40 km) north of Gulfport, Mississippi, USA. The goal of the overall study is to develop interior decay within the test specimens and then identify and character...

The study summarized in this report was conducted to examine the relationships between nondestructive evaluation parameters and the modulus of elasticity (MOE) of spruce–pine–fir structural lumber. A random sample of lumber was obtained from a local lumber yard and conditioned to approximately 10% equilibrium moisture content in the laboratory. Static bending and vibration (transverse and longitudinal) nondestructive tests were conducted on each specimen, and MOE was calculated. The relationship between static and dynamic modulus values was examined, and empirical models were developed...

The fammability of synthetic thermoplastic polymers has been recognized as an increasingly important safety problem. The goal of this study was to evaluate a green and safe fre-retardant system comprising of cellulose nanocrystals (CNC) and zinc oxide nanoparticles (ZnO). CNCs coated with nano ZnO were incorporated in the high-density polyethylene polymer (HDPE) matrix at different concentrations. Fire testing results of different formulations of HDPE containing 0.4 to 1.0% zinc oxide coated CNC exhibited a substantial decrease in the average mass loss, peak heat release rate and total...

The literature related to the phenomenon of pseudo-truncation has emphasized that the mechanical property distributions of graded lumber subpopulations are determined by the mechanical property distributions of the mill-run (or full) lumber populations from which the subpopulations are formed. Whereas previous studies have shown that the means and variances of mechanical properties in the same visual grade of lumber can vary from mill to mill, there have been no studies on the stability of the means and variances of modulus of elasticity (MOE) and modulus of rupture (MOR)in mill-run lumber...