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In the living tree, wood contains large quantities of water. As green wood dries, most of the water is removed. The moisture remaining in the wood tends to come to equilibrium with the relative humidity of the surrounding air. Correct drying, handling, and storage of wood will minimize moisture content changes that might occur after drying when the wood is in service and such changes are undesirable. If moisture content is controlled within reasonable limits by such methods, major problems from dimensional changes can usually be avoided. The discussion in this chapter is concerned with...

In this research, an investigation on the mechanical behavior of corrugated board has been performed using finite element analysis. Numerical finite element models for corrugated board geometries have been created and executed. Both geometric (large deformation) and material nonlinearities were included in the models. The analyses were performed using the commercial nonlinear finite element code ABAQUS executed on Sun SparcStations and the State of Alabama Cray C90 Supercomputer. Both in-plane and transverse loadings of corrugated board configurations have been examined. The models...

During the past century, millions of structures were built from sawn lumber and timber. When these structures reach the end of their service lives, contemporary practices emphasize landfill disposal. In recent years, the public has expressed a strong interest in developing environmentally acceptable and efficient reuse options for this solid-wood material. As a result of this interest, a test program was developed to evaluate the grades and engineering properties of nominal 2-by 10-inches (standard 38- by 236-mm) lumber collected from the Twin Cities Army Ammunition Plant and compare this...

Bridge railing systems in the United States have historically been designed based on static load criteria given in the AASHTO Standard Specifications for Highway Bridges. In the past decade, full-scale vehicle crash testing has been recognized as a more appropriate and reliable method of evaluating bridge railing acceptability. In 1989. AASHTO published the Guide Specifications for Bridge Railings, which gave the recommendations and procedures to evaluate bridge rails by full-scale vehicle crash testing. In 1993, the National Cooperative Highway Research Program (NCHRP) published Report...

Design criteria are needed specifically for portable bridges to insure that they are safe and cost effective. This paper discusses different portable bridge categories and their general design criteria. Specific emphasis is given to quantifying the effects of dynamic live loads on portable bridge design. Results from static and dynamic load tests of two portable timber bridges showed that dynamic loads can be significantly greater than static loads. Under smooth bridge entrance conditions, the mean dynamic bridge deflections were 1.13 times greater than static bridge deflections. Under...

The results of this study showed that the same relative reductions in thickness swelling (TS) previously obtained with steam-injection-pressed (SIP) resinless mats are also obtained in boards bonded with 3% isocyanate resin. Reductions in thickness swelling were proportional to steam time and pressure. Thickness swelling of 40% measured in conventionally pressed boards following a vacuum-pressure-soak treatment was reduced to 25% in a board exposed to 20 sec of steam at 600 kPa and to 6% in a board exposed to 40 sec of steam at 1,900 kPa. We believe that the reductions in thickness...

A physical, yet analytical, model of fire growth has predicted flame spread and rate of heat release (RHR) for an ISO9705 test scenario using bench-scale data from the cone calorimeter. The test scenario simulated was the propane ignition burner at the comer with a 100/300 kW program and the specimen lined on the walls only. Four phases of fire growth were simulated. The first two phases, the wall ignition and upward flame spread, have separate physical formulations. Some empiricism, however, was required to predict the phases of lateral and downward flame spread. Two groups of materials...

In this study, the microstructure of injection-molded polypropylene reinforced with cellulose fiber was investigated. Scanning electron microscopy of the fracture surfaces and X-ray diffraction were used to investigate fiber orientation. The polypropylene matrix was removed by solvent extraction, and the lengths of the residual fibers were optically determined. Fiber lengths were reduced by one-half when compounded in a high-intensity thermokinetic mixer and then injection molded. At low fiber contents, there is little fiber orientation; at high fiber contents, a layered structure arises....

A program was undertaken at the Forest Products Laboratory in conjunction with the American Society for Testing and Materials (ASTM) to develop guidelines for a credible accelerated photoaging protocol for printing and writing papers. In support of this, indepth studies of photodegredation were undertaken in sufficient detail to establish the validity of the protocol. Photoaging was carried out in two different environments. The first was intended to simulate natural aging conditions with exposure to artificial and daylight illumination. The second environment provided higher photon flux...

Removal of pressure sensitive adhesives (PSAs) from recovered paper is a major problem facing the paper recycling industry. As a result of a United States Postal Service (USPS) initiative, which currently purchases about 12% of domestic PSA production, a team was formed consisting of representatives from the USPS, the Forest Products Laboratory, Springborn Testing and Research, paper recovery companies, paper recyclers, adhesive manufacturers, and chemical suppliers. This large team of cooperators has the common goal of formulating PSAs that can be efficiently removed during the fiber...