Advanced Wood-Based Solutions for Mid-Rise and High-Rise Construction: In-Situ Testing of the Brock Commons 18-Storey Building for Vibration and Acoustic performances
This report addresses serviceability issues of tall wood buildings focusing on their vibration and sound insulation performance. The sound insulation and vibration performance may not affect the building’s safety, but affects the occupants’ comfort and the proper operation of the buildings and the function of sensitive equipment, consequently the acceptance of the 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.
The measured and estimated values should also be correlated with actual experiences of the occupants in the building if such information is obtained, for example, through a survey.
Advanced Wood-Based Solutions for Mid-Rise and High-Rise Construction: In-Situ Testing of the Origine 13-Storey Building for Vibration and Acoustic Performances
Serviceability performance studied covers three different performance attributes of a building. These attributes 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. Serviceability performance of a building is important as it affects the comfort of its occupants and the functionality of sensitive equipment as well. Many physical factors influence these performances. Designers use various parameters to account for them in their designs and different criteria to manage these performances. 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.
In order to bridge the gaps in the data, knowledge, and experience of sound and vibration performance of tall wood buildings, FPInnovations conducted a three-phase performance testing on the Origine 13-storey CLT building of 40.9 m tall in Quebec city. It was the tallest wood building in Eastern Canada in 2017.
This paper discusses the impact of the natural frequency of multi-storey timber structures, focusing on force-based seismic design. Simplified approaches to determine the frequency of light-frame and cross-laminated timber structures are investigated. How stiffness parameters for simple two-dimensional analysis models can be derived from the different contributions of deformation...
Vibrations induced by people walking is one of the most important issue in timber floor design. Low natural frequency and low mass require a careful analysis in order to prevent significant annoyance and to guarantee an acceptable human comfort. This paper is concerned with the assessment of vibration performance of a timber-concrete composite timber floor and a cross laminated timber floor used in two timber buildings under construction in Trento (Italy). Different approaches suggested by Standards and literature were employed: analytical methods, numerical analyses and laboratory tests. About analytical methods the uniformed distributed load deflection criterion (ULD), the Eurocode 5 criterion and some criterions from literature were compared, whereas the Vibration Dose Value (VDV) method, as suggested by ISO 10137, was used for the numerical models and the laboratory tests. The numerical analyses were carried out by means of a finite element modelling. The load due to footfall was simulated by static and dynamic vertical forces. The laboratory tests were characterized by thirty walking tests for each floor. Impact testing with modal hammer was also undertaken in order to investigate the dynamic properties of the specimens. All results are compared and discussed.
Wood-concrete composite slab floors provide a promising solution for achieving long spans and shallow wood-based floor systems for large and tall wood buildings. In comparison with conventional wood floor systems, such long span and heavy floors have a lower fundamental natural frequency, which challenges the floor vibration controlled design. A laboratory study, including subjective evaluation and measurement of the natural frequencies and one-kN static deflections, was conducted on wood-concrete composite floors. Method of calculation of the composite bending stiffness of the wood-concrete composite floor is proposed. The design criterion for human comfort was derived from the subjective evaluation results using the calculated fundamental natural frequency and 1 kN static deflection of one meter wide strip of the composite floor. The equation to directly determine the vibration controlled spans from the stiffness and mass was derived. Limited verification was performed. Further verification is needed when more field wood-concrete composite floors become available.
This research focuses on the dynamic behaviour of long span LCC flooring systems. Experimental testing and finite element modelling was used to determine the dynamic behaviour, with particular regard to the natural frequency, fn and mode shape of an LCC floor.
Both the experimental results and the finite element analyses agreed and showed that increased stiffness increased the natural frequency of the floor, and the boundary conditions influenced the dynamic behaviour of the LCC floor. Providing more restraint increased the stiffness of the floor system. The connectors' stiffness did not influence the dynamic performance of the floor.
The research showed that a 8 m LCC long span floor can be constructed using LVL joists of between 300 mm to 400 mm depth with a concrete thickness of 65 mm for the longer spans, and joists of between 150 mm to 240 mm depth in conjunction with a concrete topping thickness of 100 mm for the shorter spans.
Engineered Wood Products like Cross-Laminated-Timber (CLT) are transforming capabilities of wood as a construction material, enabling architects and engineers to create innovative buildings. Using CLT can have many advantages compared with using traditional materials, not least of which is reducing total superstructure gravitational weights. Reducing gravitational weight can simplify and speed up construction processes and reduce foundation costs. Plus, being made from wood, CLT has desirable ‘green’ credentials like renewability of forest resources and carbon sequestration for the lifespans of buildings. However, like other lightweight structural systems, CLT buildings can be susceptible to high-amplitude motions during ambient or other dynamic force and displacement disturbances. Studies reported here address the dynamic behaviour of mid-rise multi-storey buildings constructed from massive CLT elements, with a focus on predicting lateral modal response characteristics of such buildings. The vehicle for this is detailed Finite Element (FE) models verified as accurate replicators of ambient dynamic motions of completed CLT buildings. Here applications of FE models relate to performances of buildings during seismic events. However, the intent is to also use them to predict motions of buildings during windstorms.
This study focuses on the vibrational behaviour of 3, 5 and 7-layer cross-laminated timber (CLT) plates supported on two sides with different support conditions. Three end support setups are proposed; 1) top load over the two supported edges, 2) direct fastening to support using self-tapping screws, 3) steel angle bracket support. The measured response parameters are natural frequencies, damping, and static deflection under a point load. The rotational stiffness with load, screws and steel angle brackets will be characterized through static tests. In addition, the effect of the span is studied by varying the test span and repeating the vibration and deflection tests. The laboratory tests will be supplemented with analytical modelling. The expected outcome is the development of approaches to more accurately calculate the natural frequency and static deflection under a point load, which can account for the influence of common support conditions encountered in service.
It has been shown that measurement of elastic constants of orthotropic wood-based panel products can be more efficiently measured by modal testing technique. Identification of vibration modes and corresponding natural frequencies is key to the application of modal testing technique. This process is generally tedious and requires a number of measurement locations for mode shape identification. In this study, a simplified method for frequency identification was developed which will facilitate the adoption of the vibration-based testing technique for laboratory and industrial application. In the method, the relationship between frequency order and mode order is first studied considering the boundary condition, elastic properties of the orthotropic panel. An algorithm is proposed to predict the frequency values and mode indices based on corresponding normalized sensitivity to elastic constants, initial estimates of orthotropic ratios and measured fundamental natural frequency. The output from the algorithm can be used for identification of sensitive natural frequencies from up to three frequency spectra. Then the algorithm is integrated with the elastic calculation algorithm to extract the elastic constants from the sensitive frequencies. The elastic constants of cross laminated timber panels were measured by the proposed method. The moduli of elasticity agree well with static testing results. The calculated in-plane shear modulus was found to be within the expected range.
Project contact is Sylvain Ménard at Université Laval
Summary
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.
