Date of Award

8-2010

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Roberto Lopez-Anido

Second Committee Member

William G. Davids

Third Committee Member

Eric N. Landis

Abstract

Over the past several years, researchers at the University of Maine’s Advanced Structures and Composites Center (AEWC) have developed a blast-resistant wood composite structure to replace the existing structures used for the temporary housing of United States Army personnel during long-term deployments. The damage modes seen in the connections of the blast-resistant building during the most recent blast tests have shown the need to better understand the effect of strain rate on material behavior. As a result of this damage and the interest in a new material, an alternative high performance wood composite material, Laminated Strand Lumber (LSL), was selected for this research. The objective of this research was to study the strain rate effects on the modulus of elasticity and strength values of LSL. Two different grades of LSL (1.35E and 1.75E) were tested in tension and compression over a range of strain rates from 1E-5 to 1E-1 sec-1. Compression tests were conducted in the longitudinal and transverse directions of the material while uniaxial tension tests were conducted in the longitudinal direction only. The results of the experimental testing show that there is no strain rate effect in either the longitudinal modulus of elasticity or strength of the LSL in tension. The longitudinal compressive strength of the LSL increased by 37% and 31% for the 1.35E and 1.75E grade LSL respectively, while the transverse compressive strength increased by 41%and 16%. No statistical increase in EL was observed for the 1.35E grade LSL while an increase of 16% was noted for the 1.75E grade LSL between 1E-5 and 1E-3 sec-1. The transverse modulus of elasticity increased by 28% and 18% for the 1.35E and 1.75E grade LSL respectively. It was determined that the changes in EL may be affected by the variable density of the LSL. Recommendations for improving the testing procedure for future testing are given. In addition to the experimental testing, a simple mechanics based model was used in an attempt to predict the effect of strain rate on the modulus of elasticity of LSL at strain rates higher than those tested in the laboratory.

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