Developed in the mid-1990s in Austria and Germany, Cross Laminated Timber (CLT) is an innovative wood product known for its strength in both orthogonal directions, and its dimensional stability, making it a sustainable alternative to concrete slabs. CLT is created through the cross-lamination process, which glues together odd number of layers of wood planks placed in orthogonally alternating directions. With the growing interest in the application of CLT in North America, numerous studies has been conducted to characterize the acoustical properties of CLT panels. However, most of them focused on the sound-transmission aspect of CLT, very few on the sound absorption. This thesis will explore the sound-absorption characteristics of CLT, the effect on overall room-acoustical conditions, the utilization of resonant sound-absorbing layers on CLT to make it more sound-absorptive, and proposed solutions to improve this performance aspect. To demonstrate the low sound absorption and poor acoustical conditions in rooms with exposed and untreated CLT panels, several in-situ reverberation-time (RT) measurements were conducted in multiple buildings in British Columbia. Average sound-absorption coefficients and estimated Speech Intelligibility Indices (SII) were calculated as baseline performance measures for this study. Based on the results from five different buildings, involving 8 rooms configurations, average sound-absorption coefficients for exposed CLT panels are approximately between 0.02 to 0.13, resulting in barely acceptable conditions for verbal communication. To optimize the sound-absorption characteristics of prototype CLT panels, a transfer-matrix model has been developed to predict the performance of multi-layered CLT panels. This theoretical model was then validated by using three different sound-absorption measurement methods (impedance tube, spherical decoupling, and reverberation chamber) for multiple HR array configurations. After identifying the important parameters of an HR system and their effects on performance, a final prototype configuration with Helmholtz Resonator Array was then created with the goal of improving the room- acoustical performance of CLT, as well as responding to input from the CLT manufacturers and experts. Both the theoretical and experimental results confirmed that the proposed solution has the required sound-absorption performance and achieves all research objectives.
As 6-storey wood-frame, massive-timber and hybrid wood buildings are increasingly accepted by more jurisdictions across Canada, there is a need to develop reliable elevator shaft designs that meet the minimum structural, fire, and sound requirements in building codes. Elevator shaft walls constructed with wood-based materials have the advantages of material compatibility, use of sustainable materials, and ease of construction.
In this exploratory study, selected elevator shaft wall designs built with nail-laminated-timber (NLT) structural elements were tested to investigate their sound insulation performance because little is known about the sound insulation performance of such wall assemblies. The tests were carried out in an acoustic mock-up facility in accordance to standard requirements, and provide preliminary data on the sound insulation performance of elevator shaft walls built with NLT panels.
Four different elevator shaft walls built with NLT panels were tested and their measured apparent sound insulation class (ASTC) ratings ranged from 18 to 39 depending on their construction details. Some of the reasons that may have contributed to the ASTC ratings obtained for the elevator shaft walls described in this report as well as recommendations for future designs were provided.
It is recommended to continue improving the sound insulation of elevator shaft walls built with NLT panels to meet or exceed the minimum requirements in building codes.
The current outbreak of Mountain Pine Beetle (MPB) in the province of British Columbia (B.C.) is the most extensive disturbance event occurring in North American forests in recorded history. The concept of converting the beetle killed wood into engineered wood products by defect removal and reconstitution is employed to maximize value recovery from the material. Cross Laminated Timber (CLT), which is produced in modular form and can be utilized as part of a structural system for floor, wall or roof elements, is considered as an excellent application of the concept. CLT originates from Europe. Such products have been developed as a proprietary product by individual companies aimed at servicing specific markets. There is a need to investigate different ways of making CLT and to define its structural performance suitable for North America. The main focus of this study is to investigate the structural performance of box based CLT system used in floor applications. Comprehensive three dimensional finite element models, which can be used to analyze the mechanical and vibration behavior of the plate and box type structures, were developed. Four prototype box elements, each having five replicates, were designed and manufactured locally. Third point bending tests were conducted on the specimens in the Timber Engineering and Applied Mechanics (TEAM) Laboratory at the University of British Columbia. The numerical analysis agreed well with experimental data in terms of vertical deflection and bending stiffness. Vibration, which is critical to floor serviceability, was also studied. Three types of excitation were applied to measure the fundamental frequency of the twenty specimens. Finite element analysis provided good predictions of fundamental frequency values comparing to the experimental results. A local built demonstration building, L41home, was presented and analyzed as an example using the tools developed in this study for CLT applications. As a pioneer research of CLT materials in North America, this work has contributed to the understanding of the structural performance of floor systems using CLT panels for the commercial and residential applications.
The application of cross-laminated timber (CLT) as floor panels is limited by excessive deflection and vibration. A composite system combining CLT and ultra high-performance fibre-reinforced concrete (UHPFRC) was developed to extend span limits. Push-off tests were conducted on different connectors, and a glued-in rod connector was chosen and further refined for the proposed system. Static bending tests and free vibration tests were conducted on bare CLT panels and two composite specimens. By comparing the results, it is concluded that the proposed system considerably extend the span limits of CLT panels.
The current interest and growth of cross laminated timber (CLT) products has spurred interest in the manufacture of CLTs in the United States. The purpose of this paper is to explore the development of CLT materials from southern pine lumber commonly available in Virginia. A 5-layer CLT panel has been constructed using No. 2 southern pine lumber. Evaluation of mechanical properties, fire performance and acoustical performance were conducted. Results of these evaluations can guide the development and acceptance of CLT products in the International Building Code.
This book has been written to cover the design and performance of CLT within construction. Chapter 1 showcases its uses for architects and building designers. Chapter 2 focuses on design principles and Chapter 3 covers CLT performance, including structural design, fire performance, acoustics, thermal performance, durability, appearance, and sustainability. Chapter 4 concludes the book with thirteen case studies based on several building types. Highly illustrated with photos and technical drawings, this book demonstrates the versatility of CLT as a sustainable, engineered timber solution and will assist architects, engineers and their clients looking to work with this material.
A balanced combination of heat flows creates suitable conditions for thermal comfort—a factor contributing to the quality of the internal environment of buildings. The presented analysis of selected thermal-technical parameters is up-to-date and suitable for verifying the parameters of building constructions. The research also applied a methodology for examining the acoustic parameters of structural parts of buildings in laboratory conditions. In this research, selected variant solutions of perimeter walls based on prefab cross laminated timber were investigated in terms of acoustic and thermal-technical properties. The variants structures were investigated in laboratory but also in model conditions. The results of the analyses show significant differences between the theoretical or declared parameters and the values measured in laboratory conditions. The deviations of experimental measurements from the calculated or declared parameters were not as significant for variant B as they were for variant A. These findings show that for these analyzed sandwich structures based on wood, it is not always possible to reliably declare calculated values of thermal-technical and acoustic parameters. It is necessary to thoroughly examine such design variants, which would contribute to the knowledge in this field of research of construction systems based on wood.
This paper presents the first results of the flanksound project, a study promoted by Rotho Blaas srl regarding flanking transmission between CLT panels jointed with different connection systems. The vibration reduction index Kij is evaluated according to the EN ISO 10848 standard by measuring the velocity level difference between CLT panels. The performance of the X-RAD connection system is compared to the performance of a traditional connection system made of shear angle bracket and hold-down, both the configurations being tested with and without a resilient material placed between the construction elements. Concerning the traditional system, the influence of the difference sizes and types of fasteners - including the method of nailing or screwing - was also evaluated. The results of the measurements exposed in this work will hopefully contribute to the development of the acoustic design of timber buildings by providing a solid database of Kij values, which can be used to forecast the acoustic performance of the building according to the prediction models proposed in EN 12354-1.