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 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.
For wood floor systems, their vibration performance is significantly dependent on the conditions of their supports, specifically the rigidity of the support. Detrimental effects could result if the floor supports do not have sufficient rigidity. This is special ture for floor supporting beams. The problem of vibrating floor due to flexible supporting beams can be solved through proper design of the supporting beams. However, there is currently no criterion set for the minimum requirement for floor supporting beam stiffness to ensure the beam is rigid enough. Designers’ current practice is to use the uniform load deflection criteria specified in the code for designing the supporting beams. This criterion is based on certain ratios of the floor span (e.g. L/360, L/480 etc.). The disadvantage of this approach is that it allows larger deflections for longer-span beams than for shorter beams. This means that engineers have to use their experience and judgement to select a proper ratio, particularly for the long-span beams. Therefore, a better vibration-controlled design criterion for supporting beams is needed.
It is recommended to further verify the ruggedness of the proposed stiffness criterion for floor supporting beams using new field supporting beam data whenever they become available.
Mass timber products have shown promise as an innovative alternative to conventional framing systems for use in tall wood buildings, but this new trend in design and construction poses concerns for the long-term durability of the products. A major challenge that classically faces timber products is the threat of moisture-induced mold and decay fungi, which are a heightened concern in mass timber buildings exposed to the environment for extended duration during construction. Consequently, it is important to understand the hygric and thermal (hygrothermal) conditions that mass timber products can experience in multi-story constructions and to be able to quantify the behavior of the products for their suitable design and implementation. An eight-story mass timber building located in Portland, Oregon was chosen for this study and was instrumented for moisture content monitoring through its production, construction, and in-situ use. Record breaking precipitation levels occurred during the building’s construction and while dimension lumber and glulam products subsequently dried to acceptable levels, cross laminated timber products (CLT) dried more slowly. These measurements have an observed bias and the decay risk for the products is inconclusive. Samples of CLT used in the building were characterized for hygrothermal properties and integrated into WUFI, a simulation software, for analysis of the building. The software showed limitations for correctly simulating the behavior of CLT in isolated lab experiments and therefore a re-calibration was performed for accurate simulation. Preliminary on-site simulation results provide a decent approximation of observed data despite its high variance, but drying rate predicted by the program is lower than what was measured.