This report addresses serviceability issues of tall wood buildings focusing on vibration and sound insulation performance. The sound insulation and vibration performance may not affect building's safety, but affects occupants' comfort and proper operation of the buildings and the funciton of sensitive equipment, consequently the acceptance of midrise and tall wood buildings in market place. Lack of data, knowledge and experience of sound and vibration performance of tall wood buildings is one of the issues related to design and construction of tall wood buildings.
Mass timber is a generic name for a broad range of thick and heavy wood products such as cross-laminated timber (CLT), dowel-laminated timber (DLT), nail-laminated timber (NLT), and gluelaminated timber (GLT), among others. So far, vibration-controlled design methods have been developed mostly for CLT floors.
La construction massive en bois est un terme générique qui englobe une grande variété de produits du bois épais et lourds, notamment le bois lamellé-croisé (CLT), le bois lamellé-goujonné (DLT), le bois lamellé-cloué et le bois lamellé-collé (GLT). À ce jour, les méthodes de conception à vibrations contrôlées ont surtout été élaborées pour les planchers en CLT.
Project contact is Sylvain Ménard at Université Laval
Designers of large buildings generally want floor systems with large spans (9 m). These floors are often sized by the requirement of vibratory performance and, correlatively, deflection. The composite wood-concrete floors allow large spans with reduced static height. They are a promising alternative to simple concrete slabs. Objective 1 - Determine the evolution of the natural frequency of the CLT-concrete composite floor as a function of the stiffness of the connector, and correlate the experimental results with the model by the finite element method. Objective 2 - Parametric study of the vibration performance of the CLT-concrete composite floor. The impact of several parameters on the dynamic performance of the floor will be determined, especially the characteristics of the constituent materials, connector and the creep of the floor. Objective 3 - Build the metamodels for the study of multi-objective optimization optimization of a wood-concrete composite floor solution in relation to a regional problem in Aquitaine.
In order to address the lack of measured natural frequencies and damping ratios for wood and hybrid wood buildings, and lack of knowledge of vibration performance of innovative CLT floors and sound insulation performance of CLT walls and floors, FPInnovations conducted a series of performance testing at the Wood Innovation Design Centre (WIDC) in Prince George, BC in April 2014, during construction, and in May 2015, after building completion and during its occupation.
This report describes the building, tested floor and wall assemblies, test methods, and summarizes the test results. The preliminary performance data provides critical feedback on the design of the building for resisting wind-induced vibration and on the floor vibration controlled design. The data can be further used to validate the calculation methods and tools/models of dynamic analysis.
Three performance attributes of a building for serviceability performance are 1) vibration of the whole building structure, 2) vibration of the floor system, typically in regards to motions in a localized area within the entire floor plate, and 3) sound insulation performance of the wall and floor assemblies...
FPInnovations launched the “Next Generation Building Systems” research program to support the expansion and diversification of wood into new markets. “Next Generation Wood Buildings” can be described as buildings that implement design and construction practices, and use innovative wood-based materials and systems beyond those defined and addressed in current building codes. As part of this program, the serviceability research focuses on addressing issues related to floor and building vibrations, sound transmission and creep.
CLT is a next generation wood building material, which is a promising alternative to concrete slabs. To facilitate wood expansion into the market traditionally dominated by steel and concrete, several CLT buildings have been designed or built. Taking this opportunity, we conducted this study on two CLT buildings in the province of Quebec (i.e.,Desbiens and Chibougamau) to collect data that will form a database for the development of design provisions and installation guides for controlling vibrations and noise in CLT floors and buildings. The study also provides some information to designers and architects to strengthen their confidence in using CLT in their building projects. It is our hope that the collaboration through this study demonstrates to both designers and users of CLT buildings that if we work together, we can build good quality CLT buildings.
During the construction, ambient vibration tests were conducted on the two CLT buildings to determine their natural frequencies (periods) and damping ratios. Vibration performance tests were conducted on selected CLT floors to determine their frequencies and static deflections. ASTM standard sound insulation tests were conducted on the selected CLT walls and floors in Chibougamau CLT building to develop the sound insulation solutions. After the two CLT buildings were completed, ASTM sound insulation tests were conducted in the selected units to determine the Field Sound Transmission Class (FSTC) of the finished floors and walls, and the Field Impact Insulation Class (FIIC) of the finished floors.
We found that in general, the vibration performance of these two CLT buildings and their floor vibration performance are functional. The efforts made by the design engineers, the architects, and the contractors to make it happen are commendable, considering the lack of design provisions and guidelines in building codes for controlling vibrations in such innovative wood floor and buildings. The sound insulation of the selected units in Chibougamau building was very satisfactory. This confirmed that with proper design, construction, and installation of the sound insulation solutions studied in this report, CLT floors, walls and buildings can achieve very good sound insulation.
Some specific recommendations for CLT building sound insulation:
If flanking paths can be minimized, then it is expected that better sound insulation than what we measured on the CLT floors during the building construction will be achieved ;
Increasing the stud spacing from 400mm to 600mm for the wood stud walls enhances the airborne sound insulation of the current wood stud-CLT wall assemblies tested in this study ;
Decoupling ceiling from the structure frame and from the CLT floors is a significant factor for cost-effective sound insulation solutions ;
Selection of solutions for FSTC and FIIC above fifty (50) for non-carpeted CLT floors will ensure the satisfaction of the majority of occupants ;
Conducting subjective evaluation is useful to ensure occupants satisfaction ;
For implementation of the sound insulation solutions for floating floors, it is necessary to consult wood flooring and ceramic tiles installation guides for floating the flooring.
As interest has grown in using mass timber for commercial building projects, so too has the need to better understand the vibration characteristics of mass timber floor systems. Vibration requirements typically drive the spans and thicknesses of mass timber floors. Our team has a unique opportunity to close several crucial knowledge gaps while designing the new Health Sciences Education Building (HSEB) at the University of Washington, which is under design and is scheduled to start construction in the summer of 2019.
Case Study for Design Guide – The HSEB will be designed using the U.S. Mass Timber Floor Vibration Design Guide. Vibration performance will be measured to further validate or refine the model calibration suggestions put forth in the Design Guide.
Damping Measurements – The HSEB will contain a wide variety of program spaces with varying damping characteristics that will be measured and correlated.
Stiffness Measurements – Laboratory and in situ testing will be performed on a several floor framing systems. This will include a variety of span lengths and member depths. It will also include composite behavior of concrete and CLT floors with different connection types.
The results of this study will allow for more accurate predictions of floor vibrations. This will significantly reduce the cost of mass timber systems in way that is repeatable and scalable for future architects and engineers.
Long span timber floor solutions have demonstrated their potential to compete with concrete and steel construction for multi-storey commercial buildings. Due to the high strength-to-weight ratio of timber, serviceable vibration performance is a critical structural design issue for long spans. This project investigates the vibration...