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MEMBER Forest Operations; Pulp, Paper and Bioproducts;

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Summary

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. The two-phase testing was performed: 1) on June 08, 2017, after near completion of the building, to measure the building and bare CLT floor natural frequencies and damping ratios, and 2) on January 25, 2018, after the building was completed and partially occupied, to measure the sound insulation ratings of a CLT floor-ceiling assembly and a CLT partition wall, and on February 08, 2018, to repeat the building vibration test to measure the building natural frequencies and damping ratios. Ambient vibration testing was conducted on the building to determine its natural frequencies and damping ratios before and after occupied using FPInnovations’ verified AVT protocol. Hammer impact testing was conducted on the bare CLT floor to determine its fundamental natural frequency and damping ratio. Static deflection testing was performed on the floor to measure the deflection under 1-kN point static load. The floor vibration performance tests used ISO floor vibration test methods. Informal subjective evaluations were conducted on the floor to assess the floor vibration performance. ASTM standard field test methods for building sound insulation were used to determine apparent sound transmission class (ASTC) and apparent impact insulation class (AIIC) of the selected CLT floor-ceiling assembly, and ASTC of the selected CLT partition wall. The measured frequencies for the first three vibration modes of the finished building without occupants were 1.4 Hz for the translational vibration in the building short axis, 1.8 Hz for the torsion and 3.8 Hz for the translational vibration in the building long axis. The damping ratios for these three modes were 2% to 3% of the critical damping. With the occupants and snow, the measured building frequencies slightly reduced. The measured fundamental natural frequency of the bare CLT floor was 10.8 Hz and the 1kN static deflection was 0.19 mm. The floor vibration performance was satisfied to the evaluators. The measured ASTC and AIIC of the selected CLT floor-ceiling assembly were 58 and 54, respectively. The measured ASTC of the selected CLT partition wall was 65. In general, the quality of the results indicated that the approaches, methods and equipment selected for use for the tests were reasonable for meeting the objectives of this project. The CLT floor vibration performance is deemed to be satisfactory. The sound insulation performance of the tested CLT floor-ceiling assembly and CLT wall is beyond the code requirement and recommendation. The data provided useful information on the building lateral and shear stiffness, on the floor vibration performance, and the building sound insulation performance. It also enhances the database of damping ratios of mass timber buildings. The measured frequencies can be directly used to verify the calculated building periods by the designers using the design tool, the model and the assumptions. Therefore the data can be directly used to improve the design tool, and refine the assumptions and the model. The measured ASTC ratings of the CLT floor and the CLT wall, and the measured AIIC of the CLT floor can be used to verify the tool used for the floor and wall acoustical design, and the acoustical design goal. In March 2018, a monitoring system was installed in the building to record time histories of the building accelerations to wind excitation for a period of at least one year. The data will be used to verify the NBCC acceleration equations and criterion for controlling tall building vibration induced by wind. It is recommended to compare the building frequencies estimated by the design tool or model with the measured values, to seek out the reasons why if the discrepancies are significant, and to decide if and how the models and assumptions should be refined. 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.

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