With the introduction of Cross Laminated Timber (CLT) into North America and gaining popularity it is of interest to the design and code development community to have codified provisions to facilitate the design of CLT structures. This paper addresses the design aspect of CLT panels subjected to combined bending and compressive axial loads. Fifteen specimens covering different combinations of grades and layups of commercially available Canadian CLT panels were tested at different eccentricities to validate the proposed interaction equation. Testing program was reported in this paper and the test data was compared with the model prediction. It was concluded that the current nonlinear interaction equation given in the Canadian timber design standard (CSA O86) for timber and glulam tends to overestimate the capacity of CLT wall panel. A linear interaction equation was found to be appropriate
The Canadian standard for engineering design in wood (CSA O86) adopted the European yield model for calculations of the lateral resistance of connections with dowel-type fasteners. This model takes into account the yielding resistance of the fastener, the assembly's geometry and the embedment strength of wood. The latter is considered a function of the relative density of wood and diameter of the fastener. The purpose of this study is to verify the significance of these variables as applied to the embedment strength for threaded dowel-type fasteners of diameters 6.4 mm and greater in Canadian glulam products. The importance of this research is justified by the growing interest in the use of large-diameter threaded fasteners in heavy timber and hybrid structures of high load-bearing capacity. Based on the results of 960 tests, a new design model for the embedment strength is proposed for potential implementation in CSA O86 standard and the impact of such a change is presented.
The Canadian standard for engineering design in wood (CSA O86) adopted the European yield model for calculations of the lateral resistance of connections with dowel-type fasteners. This model takes into account the yielding resistance of the fastener, the assembly's geometry and the embedment strength of wood. The latter is considered a function of the relative density of wood and diameter of the fastener. The purpose of this study is to verify the significance of these variables as applied to the embedment strength for threaded dowel-type fasteners of diameters 6.4 mm and greater in Canadian glulam products. The importance of this research is justified by the growing interest in the use of large-diameter threaded fasteners in heavy timber and hybrid structures of high load-bearing capacity. Based on the results of 960 tests, a new design model for the embedment strength is proposed for potential implementation in CSA O86 standard and the impact of such a change is presented.
Wood-concrete composite slab floors provide a promising solution for achieving long spans and shallow wood-based floor systems for large and tall wood buildings. In comparison with conventional wood floor systems, such long span and heavy floors have a lower fundamental natural frequency, which challenges the floor vibration controlled design. A laboratory study, including subjective evaluation and measurement of the natural frequencies and one-kN static deflections, was conducted on wood-concrete composite floors. Method of calculation of the composite bending stiffness of the wood-concrete composite floor is proposed. The design criterion for human comfort was derived from the subjective evaluation results using the calculated fundamental natural frequency and 1 kN static deflection of one meter wide strip of the composite floor. The equation to directly determine the vibration controlled spans from the stiffness and mass was derived. Limited verification was performed. Further verification is needed when more field wood-concrete composite floors become available.
The design and application of cross laminated timber (CLT) is s trongly influenced by rolling shear properties of cross layers. Hence, predicting the mechanical behaviour of CLT requires accurate information about its rolling shear properties. In this study, black spruce wood laminates with three different growth ring orientations (flat sawn, in-between, quarter sawn) were edge glued to produce wooden cross layer (WCL). Two-plate shear tests were carried out on WCL to investigate the influence of growth ring orientation on the rolling shear properties. The experimental results showed that the growth ring orientation had a significant effect on rolling shear modulus of WCL, however, almost no effect on the rolling shear strength. The WCL of in-between end grain had the maximum rolling shear modulus of 89MPa and rolling sh ear strength of 2.13 MPa.
Several analytical and empirical methods have been developed and adopted in Europe for the determination of shear and bending properties of Cross-laminated Timber (CLT) elements loaded out-of-plane and in-plane. However, proposed evaluation methods for determining in-plane shear strength in CLT elements acting as deep beam or lintels need to be verified on Canadian CLT products. This paper presents results from recent testing program following established ASTM standard methods for evaluating the in-plane shear strength of CLT elements for beam applications. Results indicate that the existing test method applicable to Structural Composite Lumber (SCL) may be suitable for the evaluation of in-plane shear strength of CLT elements.
Information on ductile and brittle failure modes is critical for proper design of timber connections in Crosslaminated Timber (CLT). While considerable research has been conducted in Europe and Canada on the ductile performance of connections in CLT, little is known about the brittle behaviour. This paper presents new information from testing programs and analysis performed in Canada and in New Zealand on the brittle performance of dowel-type fasteners in CLT. The testing programs have been designed to trigger brittle failure modes based on minimum end distances and fasteners spacings specified in the Canadian timber design standard. Timber rivets and bolts/dowels are covered under this study. At the time of writing of this abstract, the testing program is advancing and results will be available at the time of paper submission.
Cross-laminated timber (CLT), a new generation of engineered wood product developed initially in Europe, has been gaining popularity in residential and non-residential applications in several countries. Numerous impressive low- and mid-rise buildings built around the world using CLT showcase the many advantages that this product can offer to the construction sector. This article provides basic information on the various attributes of CLT as a product and as structural system in general, and examples of buildings made of CLT panels. A road map for codes and standards implementation of CLT in North America is included, along with an indication of some of the obstacles that can be expected.
