Date of Award

Spring 5-14-2016

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Roberto Lopez-Anido

Second Committee Member

William Davids

Third Committee Member

Eric Landis

Abstract

The objective of this research was to conduct a technical assessment of the engineering properties of cross-laminated timber (CLT) made from local Northeastern lumber, laminated strand lumber (LSL) and mixtures of the two. The technical assessment provided the bending and shear strength and stiffnesses values for select CLT configurations, which were used to determine the feasibility of using local Northeastern lumber and LSL in CLT. Experimental lay-up designs were created for six three-layer CLT configurations using Spruce-Pine-Fir (South) (SPFs) No.2 and better and 1.35E LSL. Preliminary shear block tests were run to determine the optimal spread rate, and a board characterization was conducted by dynamic E-rating the materials to determine their modulus of elasticities. Seven 105 mm x 1.3 m x 2.45 m panels, five in the major strength direction and two in the minor, per CLT lay-up configuration were then manufactured by hand with a polyurethane adhesive.

Specimens cut from major and minor strength direction panels for each lay-up were tested in four-point quasi static bending and short span three-point bending. From the four-point bend tests, the average maximum bending stress, elastic stiffness and shear stiffness were determined for each lay-up for both strength directions. From the short span three-point bend tests, the average maximum shear stresses for four selected lay-ups in the major strength direction were determined.

From the testing results, LSL was concluded to be the stronger material in perpendicular-to-grain shear and SPFs to be the stronger material in bending when used in three-layer CLT. By using LSL in the core with SPFs in the faces, the maximum bending stress was increased by 23% compared to when SPFs was used. The use of LSL sheets in CLT produced higher elastic stiffness results in both strength directions in comparison to LSL boards. The lay-ups containing SPFs in the faces with either SPFs or LSL in the core were found to exceed the design requirements of the top, E1, CLT grade. Each of the six three-layer CLT configurations consisting of SPFs, LSL and combinations of the two investigated produced bending and shear stiffnesses in the major strength direction and bending stiffnesses in the minor strength direction exceeding those of the CLT design grades. Therefore it was concluded that both SPFs and LSL are feasible materials for use in CLT.

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