The objective of this research was to determine the feasibility of using lumber from Northeastern U.S. forests and laminated strand lumber (LSL) in cross laminated timber (CLT). Three-layer 105 mm x 1.32 m x 2.45 m CLT panels consisting solely of Spruce-Pine-Fir (South) and 1.35E LSL were manufactured by hand. Four-point bending tests were performed for specimens in the minor and major strength directions. From these tests, bending strengths and elastic and shear stiffnesses were determined for both strength directions. The all-SPFs lay-up exceeded the design requirements of CLT grade E1 and the all-LSL lay-up exceeded those of CLT grade E3. Therefore, low grade SPFs could be used to create high grade CLT panels. In addition, the use of LSL as the cross-ply material in CLT could increase the perpendicular-to-grain shear strength of CLT designs in comparison to typical lumber, which can enhance overall panel stiffness and strength.
In-plane shear and planar shear due to out-of-plane bending are important properties for the design of CLT-type floor systems. Properties of CLT-type panels are influenced by the orientation of the layer’s major stiffness directions and the properties of their layers. The layers are influenced by their characteristics, laminate aspect ratio, growth ring orientation and edge-gluing. In order to utilize the mechanical potential of CLT-type panels, it is necessary to understand the effects of layer and laminate properties on CLT performance. CLT and CLT-hybrid panels were tested in planar and in-plane shear tests. The shear properties were evaluated using static and modal test procedures, the accuracy of non-destructive test methods was evaluated. Relationships between specimen properties and the characteristics of laminates and layers, such as aspect ratio, growth ring orientation and edge-gluing, were established.
Hybrid cross laminated timber (HCLT) was fabricated using lumber and/or laminated strand lumber (LSL), the mechanical performances of which were evaluated. To reach this goal, the mechanical properties of LSL and the bending properties of CLT and HCLT were measured in this study. The properties of LSL measured included the tension strength (only in the major direction), shear strength, shear modulus, and modulus of elasticity (MOE) and modulus of rupture (MOR). The failure mode of each kind of specimens was visually examined and recorded. Four types of CLT panels, one generic CLT (used as control) and three types HCLT were fabricated. The properties measured included the bending properties (in the major direction) and planar shear properties (in both major and minor directions). It was found that the HCLT had better bending and planar shear properties than that of generic CLT. The MOE and MOR of HCLT having LSL as the outer layers were 19% and 36% higher than those of generic one, respectively. The MOE and MOR of HCLT having LSL as core layer (replacing the cross lumber layer) were 13% and 24% higher than that of generic CLT, respectively. The failure modes of four types of CLT observed included the planar shear failure of cross lumber layer, tension failure of bottom LSL, and tension failure of bottom lumber, especially tension failure of lumber originated at a knot(s).
The objective of this study is to evaluate the fire behavior of CLT manufactured with different types of SCL or lumber boards, namely with laminated veneer lumber (LVL), laminated strand lumber (LSL) and Trembling Aspen. The fire test data is also compared to those of CLT manufactured in accordance with ANSI/APA PRG-320 using solid-sawn lumber grades. More specifically, the study aims at evaluating the charring rates of this new generation of CLT panels as well as the impact of their manufacturing parameters.
The latest developments in seismic design philosophy have been geared towards developing of so called "resilient" or "low damage" innovative structural systems that can reduce damage to the structure while offering the same or higher levels of safety to occupants. One such innovative structural system is the Pres-Lam system that is a wood-hybrid system that utilizes post-tensioned (PT) mass timber components in both rigid-frame and wall-based buildings along with various types of energy disspators. To help implement the Pres-Lam system in Canada and the US, information about the system performance made with North American engineered wood products is needed. That information can later be used to develop design guidelines for the designers for wider acceptance of the system by the design community.Several components influence the performance of the Pres-Lam systems: the load-deformation properties of the engineered wood products under compression, load-deformation and energy dissipation properties of the dissipators used, placement of the dissipators in the system, and the level of post-tensioning force. The influence of all these components on the performance of Pres-Lam wall systems under gravity and lateral loads was investigated in this research project. The research project consisted of two main parts: material tests and system tests.