The growing diffusion of cross-laminated timber structures (CLT) has been accompanied by extensive research on the peculiar characteristics of this construction system, mainly concerning its economic and environmental benefits, lifecycle, structural design, resistance to seismic actions, fire protection, and energy efficiency. Nevertheless, some aspects have not yet been fully analysed. These include both the knowledge of noise protection that CLT systems are able to offer in relation to the possible applications and combinations of building elements, and the definition of calculation methods necessary to support the acoustic design. This review focuses on the main acoustic features of CLT systems and investigate on the results of the most relevant research aimed to provide key information on the application of acoustic modelling in CLT buildings. The vibro-acoustic behaviour of the basic component of this system and their interaction through the joints has been addressed, as well as the possible ways to manage acoustic information for calculation accuracy improvement by calibration with data from on-site measurements during the construction phase. This study further suggests the opportunity to improve measurement standards with specific reference curves for the bare CLT building elements, in order to compare different acoustic linings and assemblies on the same base. In addition, this study allows to identify some topics in the literature that are not yet fully clarified, providing some insights on possible future developments in research and for the optimization of these products.
This client report on the acoustics research component regarding sound insulation of elements and systems for mid-rise wood buildings is structured into a main part and four appendices. The main part outlines the background, main research considerations and summarizes conducted research and major outcomes briefly. It is structured like the Acoustics tasks in the Statement of Work of the Mid-rise Wood research project to identify accomplishments. For details on the research, testing and results, the main part references to four appendices that contain more details including test plans, test methods, specimen descriptions and all test data that is vetted so far.
Cross-Laminated Timber (CLT) is a renewable, sustainable, and cost-efficient building element that has been growing in popularity in recent years. To improve one of its weaknesses, suboptimal noise and vibration isolation performance, computationally efficient, accessible, and extensible CLT vibro-acoustic models are required. An effective approach for such models is the homogenisation of layered materials. This paper presents a validated homogenisation method based on First-Order Shear Deformation Theory (FSDT) that obtains the frequency-independent elastic material properties. It is applicable to arbitrary stacking sequences and orientations. The homogenised material properties are utilised with FSDT Equivalent Single Layer (ESL) models that are readily implemented with many finite element method codes to calculate the vibro-acoustic behaviour of CLT elements, even including thickness resonance effects when applied with an appropriate model. The presented homogenisation method for CLT is validated in a numerical study by comparing the mechanical mobilities of ESL models against layerwise dynamic models. The numerical study is conducted based on a validated 5-ply model, for 2- to 7-ply CLT plates with proportionally increasing thicknesses and three idealised boundary conditions. The frequency-independent material properties allow for graphical exploration of the anisotropic nature of CLT and the calculation universal anisotropic index of the considered CLT plates. The flexibility of the homogenisation method, combined with its ready implementation in already widely implemented FSDT models can have an application and impact beyond the vibro-acoustic considerations of CLT, into the general mechanical modelling of CLT as it is implemented in ever more advanced applications.
Project contact is Christopher Higgins at Oregon State University
Summary
This project will optimize the strength, stiffness, vibration characteristics, acoustic qualities and fire resistance of cross-laminated floor systems utilizing a composite concrete and cross-laminated timber product. This project includes development, testing and optimization of an economical shear connector (to connect the CLT panel to the concrete slab) that will be compared with existing screw and steel plate solutions. The resulting prototype floor system will be tested at full scale.
In many mass timber buildings, CLT or nail laminated timber (NLT) floors are designed with a concrete topping to improve acoustic separation, reduce vibration or act as a fire barrier. Little research has examined the fire behavior of these floor systems, but some preliminary tests involving LVL show that they may be able to meet three-hour fire resistance ratings, which could potentially open up the use of mass timber in Type I buildings, representing a large market opportunity. This project will test the behavior of composite floors under fire loading conditions considering the following parameters: shear connector type, mass timber panel types and thicknesses and concrete thicknesses. It will also test and validate an innovative fire research methodology using radiant panels.
Facilitation of Acoustics Testing for Sustainable Mass Timber Technologies, Leading to Publication of Open Source Acoustics Data for Standard Acoustics Scenarios
Project contact is Kevin Van Den Wymelenberg at the University of Oregon
Summary
Our aim is to support the acceptance and increase market share of sustainable mass timber construction technologies such as Cross Laminated Timber (CLT), Mass Plywood Panel (MPP), Glue Laminated Timber (GLT), and Nail Laminated Timber (NLT), by lowering or eliminating barriers due to lack of acoustics data for mass timber construction assemblies. Currently, sustainable mass timber projects carry the cost of required acoustics testing, impairing their economic feasibility. With our new acoustics testing facility, testing supported by this grant will produce common acoustics data on the assemblies most in market demand. These data will be hosted in an online open-access database, supporting rapid growth in this industry. Increasingly specialized testing scenarios will be more easily accommodated, as this facility is located closer to USFS source materials and production facilities than currently operating facilities and is designed specifically for the specialized requirements of testing mass timber assemblies. Since sustainable mass timber technologies allow increased utilization of lower quality timber, and timber with insect damage, increasing the market share of mass timber will increase utilization of USFS timber, specifically that which might otherwise remain on-site unused. With removal of this type of timber, fire load will be lessened as well. Initial testing supported by this grant will include mass timber assemblies constructed with lower quality and smaller dimension timber.
These Joint Professional Practice Guidelines – Encapsulated Mass Timber Construction Up to 12 Storeys were jointly prepared by the Architectural Institute of British Columbia (AIBC) and Engineers and Geoscientists British Columbia.
The AIBC and Engineers and Geoscientists BC regulate and govern the professions of architecture, engineering, and geoscience under the Architects Act and the Professional Governance Act. The AIBC and Engineers and Geoscientists BC each have a regulatory mandate to protect the public interest, which is met in part by setting and maintaining appropriate academic, experience, and professional practice standards.
Engineering Professionals are required per Section 7.3.1 of the Bylaws - Professional Governance Act to have regard for applicable standards, policies, plans, and practices established by the government or by Engineers and Geoscientists BC, including professional practice guidelines. For Engineering Professionals, these professional practice guidelines clarify the expectations for professional practice, conduct, and competence when providing engineering services for EMTC buildings. For Architects, these guidelines provide important information and identify issues to be considered when providing architectural services for EMTC buildings. These guidelines deal with the performance of specific activities in a manner such that Architects and Engineering Professionals can meet their professional obligations under the Architects Act and the Professional Governance Act.
These guidelines were developed in response to new classifications of building size and construction relative to occupancy introduced in the 2018 British Columbia Building Code (BCBC), under Division B, Article 3.2.2.48EMTC. Group C, up to 12 storeys, Sprinklered, and Article 3.2.2.57EMTC. Group D, up to 12 storeys, Sprinklered. These new classifications were introduced in Revision 2 of the 2018 BCBC on December 12, 2019 and in Amendment 12715 of the 2019 Vancouver Building By-law (VBBL) on July 1, 2020. Additionally, provisions related to Encapsulated Mass Timber Construction (EMTC) were introduced in Revision 1 of the 2018 British Columbia Fire Code (BCFC) on December 12, 2019.
These guidelines were first published in 2021 to provide guidance on architectural and engineering considerations relating to these significant changes to the 2018 BCBC, the 2019 VBBL, and the 2018 BCFC. For Engineering Professionals, these guidelines are intended to clarify the expectations of professional practice, conduct, and competence when Engineering Professionals are engaged on an EMTC building. For Architects, these guidelines inform and support relevant competency standards of practice to be met when Architects are engaged on an EMTC building.
As with all building and construction types, the EMTC-specific code provisions prescribe minimum requirements that must be met. The majority of EMTC of 7 to 12 storeys are considered High Buildings, and as such are subject to the BCBC, Subsection 3.2.6. Additional Requirements for High Buildings.
Set plans and requirements for monitoring vertical movement, energy efficiency, acoustics, and moisture management in demonstration buildings, and collaborate with the University of Ottawa for measuring structural characteristics of the demonstration buildings
This paper describes the design of a 12-story apartment building on a single story basement, which has wood floor diaphragms, and structural steel gravity and lateral load resisting systems. The design objective was to develop the most cost-effective structural system while meeting building functionality goals and adhering to code requirements. The main structural and non-structural design issues considered in this all-wood floor building are reviewed: gravity loads, lateral loads imposed by wind and earthquake, floor vibration, acoustics, and changes in wood moisture content. The lightweight structural form proved to be a practical system to lower construction material cost and enable alternative construction techniques to be employed. A comparison with a concrete floor option is briefly made.
