Date of Award

Summer 8-16-2024

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Forest Resources

Advisor

Ling Li

Second Committee Member

Zhiyong Chen

Third Committee Member

Stephen Shaler

Abstract

Cross-laminated timber (CLT), a product in the mass timber family, is an innovative engineered wood product that enables the construction of mid- and high-rise timber buildings. CLT has been used extensively in timber construction. A typical use of CLT panels is in the construction of walls, floors, and roofs which can carry a continuous load. This load can impact the long-term performance of the CLT structure and must be considered in the design phase.

The primary goal of this research was to better understand the long-term creep behavior of CLT beams and contribute to the development of numerical approaches. The creep performance of CLT beams was assessed under elevated relative humidities using computational simulation and validated against experimental investigation. This study consists of two parts. In the first part, the flexural response of CLT beams was assessed. Material characterization experiments were conducted on spruce to provide the necessary material data for the numerical models. Flexural tests of CLT beams were performed to determine the modulus of elasticity (MOE) and modulus of rupture (MOR) of the CLT beams. In addition to the experimental work, a computational model was developed to predict the flexural response of CLT beam. The 3D Hashin failure criterion was adopted to predict the intralaminar failure of the CLT beam. The mean experimental and numerical values of MOE of the CLT beam were 9.14 GPa and 8.69 GPa, respectively with a difference of 5.10 %. In terms of the MOR, the mean experimental value and numerical value were 39.16 MPa and 40.11 MPa, respectively with a difference of less than 3 %.

The second part of this study was focused on the assessment of creep performance of the CLT beam. A finite element creep model was developed to predict the interaction between the stress and moisture content change in the CLT beam simultaneously loaded under a constant dead load and subject to an elevated relative humidity condition, 30%, 60%, and 90%. ABAQUS user-defined UMAT and DFLUX subroutines were used to evaluate the material behavior and the elevated relative humidity loadings, respectively. The numerical model showed a well prediction of the moisture content distribution in the CLT model. Also, the numerical deflection result had shown a good agreement when compared to the experimental creep deflection. The results of this study showed that the current computational model can be used to predict the long-term creep behavior of such beams, and it can easily be adapted to account for different timber and geometry once the appropriate material properties are available.

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