The cross laminated timber (CLT) technology is nowadays a well-known construction system, which that can be applied to several typologies of residential and commercial buildings. However some critical issues exist which limit the full development of the CLT construction technology: problems in handling, difficulty in assembling...
The development of this primer commenced shortly after the 2018 launch of the Mass Timber Institute (MTI) centered at the University of Toronto. Funding for this publication was generously provided by the Ontario Ministry of Natural Resources and Forestry. Although numerous jurisdictions have established design guides for tall mass timber buildings, architects and engineers often do not have access to the specialized building science knowledge required to deliver well performing mass timber buildings. MTI worked collaboratively with industry, design professionals, academia, researchers and code experts to develop the scope and content of this mass timber building science primer. Although provincially funded, the broader Canadian context underlying this publication was viewed as the most appropriate means of advancing Ontario’s nascent mass timber building industry. This publication also extends beyond Canada and is based on universally applicable principles of building science and how these principles may be used anywhere in all aspects of mass timber building technology. Specifically, these guidelines were developed to guide stakeholders in selecting and implementing appropriate building science practices and protocols to ensure the acceptable life cycle performance of mass timber buildings. It is essential that each representative stakeholder, developer/owner, architect/engineer, supplier, constructor, wood erector, building official, insurer, and facility manager, understand these principles and how to apply them during the design, procurement, construction and in-service phases before embarking on a mass timber building project.
When mass timber building technology has enjoyed the same degree of penetration as steel and concrete, this primer will be long outdated and its constituent concepts will have been baked into the training and education of design professionals and all those who fabricate, construct, maintain and manage mass timber buildings.
One of the most important reasons this publication was developed was to identify gaps in building science knowledge related to mass timber buildings and hopefully to address these gaps with appropriate research, development and demonstration programs. The mass timber building industry in Canada is still a collection of seedlings that continue to grow and as such they deserve the stewardship of the best available building science knowledge to sustain them until such time as they become a forest that can fend for itself.
Project contact is Kevin Van Den Wymelenberg at the University of Oregon
The goal of this project is to accelerate the application of structural mass timber, such as cross-laminated timber (CLT), in outpatient healthcare construction. In particular, this project will address concerns related to hygienic and moisture performance of CLT, as well as exploring other challenges faced in mass timber construction. The project will engage with industry partners representing architecture, engineering, and construction (AEC), healthcare professionals, and policy-makers to advance the state of knowledge and market penetration of CLT in healthcare. Healthcare construction is a large and growing sector; pioneering the use of CLT in this market would significantly increase utilization of small-diameter and lower-quality timber. Ultimately, successful implementation of this project would help achieve USFS regional priorities of supporting ecosystem restoration and wildland fire management, as well as Oregon’s State Forest Action Plan goals of protecting communities at risk of wildfire, maintaining the forestland base, and preserving diversity of upland habitats.
This paper related to elimination of the deficiencies. The behaviour of multi-storey buildings braced with cores and CLT shear walls is examined based on numerical analyses. Two procedure for calibrating numerical analysis models are proposed using information from Eurocode 5  and specific experimental test data. This includes calibration of parameters that characterise connections between CLT panels and other CLT panels, building cores and shear walls. The aim is to make the characterizations of behaviours of connections that reflect how those connections perform within complete multi-storey superstructures, rather than in isolation or as parts of substructures. The earthquake action for cases studied was according to Eurocode 8  and using the appropriate behaviour factor (q factor). Results of analyses of entire buildings are presented in terms of principal elastic periods, base shear and up-lift forces. Discussion addresses key issues associated with behaviour of such systems and modelling them. Obtained results permit creation of appropriate guidelines and rules for design of the aforementioned types of hybrid buildings incorporating CLT wall panels.
At present in Chile it is not possible to construct buildings higher than 3 storeys using timber as structural material. This difficulty is due to high demands of regulations, in addition to cultural reasons, even though there are buildings in timber with more than 5 storeys built in 1910 in Chile (Sewell), which are preserved nowadays. A multidisciplinary team at UC Timber Innovation Center (CIM UC) works on the design of a mid-rise building in timber with a platform frame system for a mining company with few budget restrictions for this specific project. The results will be presented in this paper. Been the economic feasibility the main concern of the UC Timber Innovation Center (CIM UC), in order to spread this technology to a standard client, a larger team is working in parallel towards a proposal of modification of structural design regulations for the construction of mid-rise buildings in Chile with timber platform frame system. The work included an extensive bibliographic revision, followed by structural tests on 2D and 3D timber structures.
Cross laminated timber (CLT) has been rapidly developed and utilized for multi-rise constructions in recent years, even high-rise CLT buildings with 40 stories have been proposed and designed. A use of unbonded post-tensioning (PT) steel bars through over CLT walls of the high-rise CLT buildings to take up the tensile forces produced by wind load has been considered, following the regulations of unbonded post-tensioned (UPT) concrete walls. This paper introduces a finite element model to simulate the nonlinear lateral load behavior of the UPT high-rise CLT buildings with elastic connections between the CLT elements. The analysis results indicate that the unbonded PT bars can effectively reduce the lateral displacement of the high-rise CLT building. While compared with a theoretical full rigid CLT model, the advanced model is found to be more accurate for estimating the response of UPT high-rise CLT building under horizontal load.
Cross-Laminated-Timber (CLT) is increasingly gaining popularity in residential and non-residential applications in North America. To use CLT as lateral load resisting system, individual panels need to be connected. In order to provide in-plane shear connections, CLT panels may be joined with a variety of options including the use of self-tapping-screws (STS) in surface splines and half-lap joints. Alternatively, STS can be installed at an angle to the plane allowing for simple butt joints and avoiding any machining. This study investigated the performance of CLT panel assemblies connected with STS under vertical shear loading. The three aforementioned options were applied to join 3ply and 5-ply CLT panels. A total of 60 mid-scale quasi-static shear tests were performed to determine and compare the connection performance in terms of strength, stiffness, and ductility. It was shown that – depending on the screw layout – either very stiff or very ductile joint performance can be achieved.
International Conference on Structural Health Assessment of Timber Structures
September 9-11, 2015, Wroclaw, Poland
A timber building made of cross-laminated timber (CLT) panels is a modular system where all panels are pre-cut in factory. On site, the single components are then assembled connecting the panels with mechanical fasteners, mainly angle brackets with nails and/or screws, hold-downs, metal plates and self-tapping screws. CLT wall panels are very rigid in comparison to its connections. Thus, connections play an essential role in maintaining the integrity of the structure providing the necessary strength, stiffness and ductility, and consequently, they need close attention by designers. However, there is still a lack of proper design rules for these connections, in particular under cyclic loads, mainly due to a large variety of connectors and connection systems. In this paper, the different properties of connections for CLT buildings, on both monotonic and cyclic behaviour, are described using recent works from different authors. From the bibliography, it is clear that experimental data, regarding both monotonic and cyclic tests, is required for the assessment of the performance of the CLT structural system attending to the interaction between rigid panels and connections. This work evidences results from experimental campaigns and numerical analysis regarding definition and quantification of the cyclic response of CLT connections. Examples regarding monotonic and cyclic tests aimed to evaluate cyclic behaviour of connections through physical parameters, such as the impairment of strength and the damping ratio, are presented and discussed.