Thesis (M.E.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references (leave 107-112).

A comparison of the creep/duration of load (DOL) performance of a new structural wood composite material called Parallam® parallel strand lumber (PSL) to two grades of machine-stress-rated (HSR) Douglas-fir lumber is presented in this thesis. Evaluation of the creep/DOL performance was made on nominal 2x4 members under constant bending stress at three stress levels. A total of 306 test specimens were evaluated for a 15-1/2 month time period. The analysis suggests that the duration of load effect for Parallam PSL was consistent with the Madison curve for the time period studied while the MSR Douglas-fir lumber was consistent with recent duration of load models developed for structural lumber. The analysis also indicates that the current duration of load adjustment factors can be applied to develop working stresses for Parallam. The creep behaviour of the Parallam PSL was found to be equivalent or better than the two MSR lumber grades under dry-service conditions. Furthermore, evidence of linear viscoelastic behaviour was found for all test materials within the range of applied stresses evaluated. Two mathematical models of creep were fitted to the creep data and compared. A '4-parameter linear viscoelastic' model fitted the creep data better than an empirical 'power curve' model. The model parameters developed provide a basis for estimating the mean creep behaviour and variability in creep response for these materials under in-service load conditions for dry-service environments. / Forestry, Faculty of / Graduate

Southern pine (SP) lumber, the primary softwood lumber in the United States, has been popular since early colonization of the U.S.A. and remains a preferred choice for today’s lumber construction professionals. SP trees, as the major commercial softwood forest in South region, are largely grown, managed, and harvested on privately owned plantation forests. In the United States, softwood lumber consumption as a percentage of total lumber consumption has remained around 83% since the 1960s. Most softwood lumber is used for housing construction. SP comprises the primary softwood lumber products in the United States due to its superior mechanical properties, rapid drying capability, versatility, and availability. SP lumber also has long been the preferred species for pressure treatment because of its unique cellular structure that permits deep, uniform penetration of preservatives. However, as a natural material, the mechanical and physical performance of SP lumber has changed over the past decades according to the intensive lumber plantation management and dynamic market consumption. As a result, visually graded lumber products contain a large portion of juvenile wood and a lack of large cross section became two main issues in the most recent SP lumber marketing activities. According to the recent United States timber production statistic report, the South has given up its position as the largest softwood lumber-producing position in 2011. The total U.S. softwood lumber production in 2011 was about 26.8 × 109 bf, with 13.3 × 109 bf produced from West region and 12.0 × 109 bf produced from South region (Howard and Westby 2013). In this study, research that attempts to develop better and higher value SP lumber has been conducted for lumber construction marketing purpose. Five chapters are included in this study to fulfill the research purposes. Two lumber composite products made with low grade SP lumber were fabricated and evaluated for market purpose. A prototype in-grade testing plan to assess the actual design values of visually graded southern pine lumber from the gulf south region in the USA was developed. For comparison purpose, nondestructive tests (NDT) with four commercial techniques on on-grade No.2 SP lumber were conducted.

During the past two decades much scientific investigation has been directed toward the elimination and profitable utilization of the waste products of manufacture and agriculture. One of the outstanding developments has been an industry that utilizes agricultural waste products to produce synthetic lumber. Such materials as cornstalks (1), bagasse (2), wheat straw (3), wood (4), whole cotton plants (5) and etc., have entered into the manufacture of the different synthetic lumbers, and the different products have met with varied degrees of success. An investigation was undertaken to determine the feasibility of utilizing cotton stalk as a basic material in the manufacture of synthetic lumber. The cotton stalk is not just an ordinary waste, but a highly undesirable refuse when left standing in the fields; for, during the winter months the dead plant acts as a home for the boll weevil then in its dormant stage. / Ph. D.

Thesis (M.S.)--Oregon State University, 1985. / Typescript (photocopy). Includes bibliographical references (leaves 81-82). Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 1983. / Typescript (photocopy). Includes bibliographical references (leaves 212-216). Also available on the World Wide Web.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xi, 154 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 112-122).

Thesis (M.S.)--Oregon State Agricultural College, 1930. / Typescript. Includes bibliographical references (leaves 126-131). Also available on the World Wide Web.

Thesis (M.S.)--Oregon Agricultural College, 1928. / Typescript. Also available on the World Wide Web.

Thesis (Ph.D.)--University of Melbourne, Institute of Land and Food Resources, 2005. / Typescript. Includes bibliographical references (leaves 106-111).