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.
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.
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.
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.
The key objective of this study is to analyze full-scale fire-resistance tests conducted on structural composite lumber (SCL), namely laminated veneer lumber (LVL), parallel strand lumber (PSL) and laminated strand lumber (LSL). A sub-objective is to evaluate the encapsulation performance of Type X gypsum board directly applied to SCL beams and its contribution to fire-resistance of wood elements.
The test data is being used to further support the applicability of the newly developed Canadian calculation method for mass timber elements, recently implemented as Annex B of CSA O86-14.
In this study market opportunities for treated glue-laminated (glulam) products were investigated in the industrial wood sector. The main benefits of treated glulam are through-product treatment and the ability to manufacture treated products in shapes and sizes that do not fit into common treating chambers. These attributes provide for very durable and large glulam structures that are appropriate for outdoor use. For these reasons bridges, power poles, and sound abatement barriers were investigated. These are markets where wood has lost market share to or is being challenged by concrete and steel substitutes.
The vehicular bridge market was once heavy to the use of wood. Today wood accounts for only 7% of the number bridges in the US and less than 0.9% of the actual surface area of bridges in place. In interviewing municipalities in Canada it is clear that wood is not the preferred material with many wood bridges being replaced by concrete. Further, none of the municipalities contacted were planning wood bridges. However, wood bridges are still being installed. In the US 0.9% of the bridges installed by area in 2007 were wood. This is good news as wood is holding its market share. Steering clear of high volume or large bridges, local bridges are well suited for wood as they are plentiful, small in scale, and many are in disrepair. If 20% of local bridges were built with wood in Canada this would have equalled approximately $51 million in wood bridge construction in 2007.
Municipalities are much more open to the use of wood for pedestrian bridges and overpasses. Their quick construction and aesthetics are positive attributes in this application. One municipality contacted is planning multiple wood pedestrian bridges in the next five years. However, for the purpose of this market review there is little published information on pedestrian bridges.
Noise abatement barriers are a good high-volume technical fit for treated glulam. Increases in traffic and current road infrastructure improvements will lead to more demand for sound abatement in the future. This market is dominated by concrete, but at a very high price. If treated glulam can give adequate durability and sound performance properties it would be approximately 20% cheaper than concrete. The market for sound barriers in Canada could utilize up to 10 mmbf of wood per year to construct 80 km of barrier. This product can also be marketed as a high-performance acoustic fence for residential markets.
Treated glulam was also considered for utility poles. It is transmission grade poles where glulam would best fit the market as the demand is for longer poles which are more difficult to get in solid wood. This type of pole is where wood is currently being displaced by tubular steel. If glulam poles were used in 25% of the replacement transmission poles per year this could equal 8 mmbf. Light poles or standards are another market to consider. While this is a relatively low volume market glulam light standards are a premium product in European markets.
This report summarises the findings in a project directed at determining what is known about the fire performance of connections between heavy timber members.
In Canada, where a 45 minute fire-resistance rating is required, the NBCC lists minimum dimensions of solid sawn or glulam columns (loaded in compression), beams (loaded in bending) and trusses (bottom chord loaded in tension) which achieve the rating. Methods for designing connections between solid sawn or glulam members that preserve the 45-minute rating are also provided. Where a one-hour fire resistance rating is required, the NBCC provides equations to calculate the dimensions of glulam columns (loaded in compression) and beams (loaded in bending) which achieve the rating. However, no guidance is given for designing glulam members loaded in tension and no guidance is given on connections between glulam members that preserve the one-hour rating. Furthermore, no guidance is provided for designing solid sawn members (or their connections) when loaded in compression, bending or tension.
In the U.S.A., the minimum cross-sectional dimensions of glulam and solid-sawn timber beams and columns that achieve a 1-hour rating can be calculated from the same simple formulae provided in NBCC. As an alternative, a more advanced mechanics-based method can be used to calculate minimum cross-sectional dimensions of glulam and solid-sawn timber loaded in bending, compression and tension. Where a 1-hour fire-resistance rating is required, connectors and fasteners must be protected from fire exposure by wood, fire-rated gypsum board, or any coating approved for the required fire-resistance time. This approach does not account for any inherent fire resistance of the connection but rather requires it be protected by wood, fire-rated gypsum board or a coating that can provide the entire 1-hour rating.
In Europe, guidance is provided on how to design wooden structures and their connections to achieve fire resistance ratings up to one hour. Extensive guidance is given for connections consisting of two structural members spliced together with side plates of wood or steel and held together with dowel-type fasteners (nails, bolts, dowels and screws). Unprotected wood-to-wood connections of this sort, designed in compliance with ambient (non-fire) design standards, have an inherent fire resistance rating of at least 15 minutes. The fire-resistance rating can be increased to 30 minutes or even 60 minutes by the application of wood, wood-based or gypsum board panels with thickness calculated using simple formulas. As an alternative, a fire-resistance rating up to 60 minutes can be achieved using connections with internal steel plates.
There is currently no guidance provided to designers in Canada on how to design a connection between heavy timber members that can ensure a 1-hour rating. As this seems inappropriate, it is strongly recommended that Canadian building code committees be approached and requested to adopt either the approach taken in the USA or the one in Europe.