This Report presents the results from experimental studies of the airborne sound transmission of mass timber assemblies, together with an explanation of the calculation procedures to predict the apparent sound transmission class (ASTC) rating between adjacent spaces in a building constructed of mass timber assemblies.
The experimental data which is the foundation for this Report includes the laboratory measured sound transmission loss of wall and floor assemblies constructed of Cross Laminated Timber (CLT), Nail-Laminated Timber (NLT) and Dowel-Laminated Timber (DLT), and the laboratory measured vibration reduction index between assemblies of junctions between CLT assemblies. The presentation of the measured data is combined with the presentation of the appropriate calculation procedures to determine the ASTC rating in buildings comprised of such assemblies along with numerous worked examples.
Several types of CLT constructions are commercially available in Canada, but this study focused on CLT assemblies with an adhesive applied between the faces of the timber elements in adjacent layers, but no adhesive bonding between the adjacent timber elements within a given layer. These CLT assemblies could be called “Face-Laminated CLT Assemblies” but are simply referred to as CLT assemblies in this Report. Another form of CLT assemblies does have adhesive applied between the faces of the timber elements in adjacent layers as well as adhesive to bond the adjacent timber elements within a given layer. These assemblies are referred to as “Fully-Bonded CLT Assemblies” in this Report. Because fully-bonded CLT assemblies have different properties than face-laminated CLT assemblies, the sound transmission data and predictions in this Report do not apply to fully-bonded CLT assemblies.
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.
Cross-Laminated Timber (CLT) is gaining momentum as a competitor to steel and concrete in the construction industry. However, with CLT being relatively new to North America, it is being held back from realizing its full potential by a lack of research in various areas, such as vibration serviceability. This has resulted in vague design guidelines, leading to either overly conservative designs, hurting profit margins, or leading to overly lenient designs, resulting in occupancy discomfort. Eliminating these design inefficiencies is paramount to expanding the use of CLT and creating a more sustainable construction industry.
This thesis focuses on the effect of a heavy topping, in this case 2" of concrete over a layer of rigid insulation, on a CLT floor. To this end, modal analysis was performed on two spans of three CLT panels in the Andy Quattlebaum Outdoor Education Center at Clemson University. By performing a series of instrumented heel-drop tests with a roving grid of accelerometers, the natural frequencies, mode shapes, frequency response functions, and damping coefficients were determined. By comparing the results to several different numerical models, the most appropriate model was selected for use in future design. In addition, a walking excitation test was performed to calculate the root mean square acceleration of the floor for comparison to current design standards.
This study found that, with a layer of rigid insulation separating the topping and the panel, the system behaved predictably like a non-composite system. The resultant mode shapes also verified that the boundary conditions behaved very close to “hinged” and showed that the combination of the surface splines and the continuous topping provide significant transverse continuity in terms of response to vibrations. Lastly, the results of the walking excitation test showed that, with some further study, the current design standards for steel vibration serviceability can be applied to great effect to CLT systems.
The report aims to investigate norms, standards, guidelines and experience within the industry for how to design CLT (cross-laminated timber) regarding vibrations induced from humans. The following is being researched, ISO137, KL-trähandboken, Eurocode 5 and a new unpublished working draft of Eurocode 5 final working draft, Canadian CLT handbook and Cross-laminated timber structural design according to Eurocode from Austria.The conclusion is that the literature for CLT is non-existent in the current Eurocode 5 which only addresses timber floors with joists, however the new Eurocode draft suggests an update to include CLT which is similar to the norm CLT from Austria.The report contains a calculation part in which an analysis is conducted for a real project with calculations based on Eurocode 5 and the Eurocode 5 final working draft, the design tool Calculatis and FEM program RFEM. The calculations are compiled and evaluated.The calculation results show differences between the different standards. The natural frequencies are typically the same. The biggest difference is between the accelerations which is in direct relation to the modal mass, and the modal mass differs a lot between the calculations. It is understandable how Eurocode 5 final draft and RFEM calculate the modal mass, but not so for Calculatis as it doesn’t show any calculations in the technical documentation.There is a difference of the modal mass between Eurocode 5 final draft and RFEM, likely because EK5 calculate the modal mass for a rectangular floor simply supported at two or four sides. Whereas the RFEM model is not strictly rectangular nor is it simply supported everywhere, instead there are beams in some places. This suggests that caution should be regarded in calculations where floor structures have been simplified.
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.
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.
As part of its research work on wood buildings, FPInnovations has recently launched a Design Guide for Timber-Concrete Composite Floors in Canada. This technique, far from being new, could prove to be a cost-competitive solution for floors with longer-span since the mechanical properties of the two materials act in complementarity. Timber-concrete systems consist of two distinct layers, a timber layer and a concrete layer (on top), joined together by shear connectors. The properties of both materials are then better exploited since tension forces from bending are mainly resisted by the timber, while compression forces from bending are resisted by the concrete. This guide, which contains numerous illustrations and formulas to help users better plan their projects, addresses many aspects of the design of timber-concrete composite floors, for example shear connection systems, ultimate limit state design, vibration and fire resistance of floors, and much more.
Self-centring Cross-Laminated Timber (CLT) walls are a low damage seismic force resisting
system, which can be used to construct tall wood buildings. This study examines two
approaches to model self-centring CLT walls, one that uses lumped plasticity elements, and
another that uses fibre-based elements. Finite element models of self-centring CLT walls are
developed using the Python interpreter of Opensees, OpenSeesPy, and tested under monotonic
and reverse cyclic loading conditions. Outputs from the analysis are compared with data from
two existing experimental programs. Both models accurately predict the force displacement
relationship of the wall in monotonic loading. For reverse cyclic loading, the lumped plasticity
model could not capture cyclic deterioration due to crushing of CLT. Both models slightly
overpredict the post-tension force. Sensitivity analyses were run on the fibre model, which
show the wall studied is not sensitive to the shear stiffness of CLT.
OpenSeesPy models are also created of a two-story structure, which is tested dynamically
under a suite of ground motions. The structure is based on a building tested as part of the
NHERI TallWood initiative. During testing the foundation of the building was found to be
inadvertently flexible. To determine the appropriate model parameters for this foundation,
calibrations were performed by running a sequence of OpenSeesPy analyses with an
optimization algorithm. Outputs from the lumped plasticity and fibre models were compared
to experimental results, which showed that both could capture the global behaviour of the
system with reasonable accuracy. Both models overpredict peak post-tension forces. The suite
of analyses is then run again on the building to predict the performance with a rigid foundation.
Cyclic deterioration is more significant for the building with a rigid foundation, and as a result
the fibre mode is more accurate.