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Strength, stiffness, and stability of solid continua: gravity loading scenario on cross-laminated timber

University of British Columbia

Given the variety of wood species available, understanding of cross-laminated timber (CLT) materials is by no means complete. This dissertation serves to advance the state-of-the-art in understanding the material and structural response of the CLT system and developing engineering tools for modelling and predicting such responses. The investigation consisted of an experimental study, numerical study and reliability analysis. The hypothesis being tested is that the cross-layers have some contributions towards the CLT’s behaviour under the axial compression load. In this context, to evaluate the physical and mechanical properties of CLT-lamella(sawn lumber), testing was done on the small-scale (specimens’ length ≤ 250 mm) clear wood and wood contains defects specimens. Then, a medium-scale (495 mm ≤ specimens’ length ≤ 1000 mm) 3-, 5-, 7- and 9-layer CLT columns and a full-scale (specimens’ length ≥ 2400 mm) 3- and 5-layer CLT elements have been tested. In addition, to characterize the stiffness (modulus of elasticity) of CLT materials, we employed three types of testing, namely, compression test, flexural test, and transverse vibration test. A numerical study is then employed. In order to compute the strength and stiffness of medium-scale CLT composite, we developed a nonlinear material model, namely, Subroutine for Orthotropic Materials’ Elasticity & Rate-independent Plasticity (SOME&RIP), and implemented into ANSYS as an UserMat library. In addition, a finite element tool, namely, Analysis of Universal Beam-Columns (AnUBC), considering the material and structural nonlinearities for the stability analysis of full-scale CLT structures is developed in MATLAB. Finally, reliability analysis is carried out considering the sources of uncertainties that can be resulted from production, construction, material and loading conditions. Results show that characteristic strengths of the medium-scale 3-, 5-, 7-, and 9-layer CLT specimen groups are 42%, 21%, 64% and 65% higher than the code specified strength, respectively. Moreover, characteristic stiffness is approximately the same as its code’s counterpart. Following the reliability analysis, we conclude that for utilizing CLT capacity efficiently and economically, using the characteristic properties and a performance factor of 0.9 instead the current practice value of 0.8 is recommended in the CSA O86 code design equation.

Text

2019-11-21

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/72348

Forestry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/