Optimizing Floor Vibration Performance: A Probabilistic Approach to Sustainable Laboratory Structural Design

Michael Wesolowsky, Swallow Acoustic Consultants Ltd. | Thornton Tomasetti

In the pursuit of more sustainable construction practices, advanced materials and design techniques have led to lighter and more flexible structural systems in buildings. These lightweight systems are more susceptible to structural vibration. Besides creating uncomfortable working conditions for the occupants of a building, sensitive laboratory equipment can be negatively impacted to the point that it loses its ability to function properly and reliably. This can lead to conflict within the design team as vibration consultants often recommend more robust construction around the area where sensitive equipment is to be located, while structural engineers, architects and sustainability consultants prefer to keep the structural elements at a minimum.

Since construction materials are typically manufactured from non-renewable resources and transported over long distances, a more accurate prediction of floor vibrations is likely to allow refinements to the structural design, resulting in lower construction costs for the owner and a more environmentally responsible approach, as well as an improved design that will support multiple uses, reducing the likelihood of requiring future retrofits.

Vibration consultants have employed both simplistic and more advanced models of footfall-induced vibration prediction over the years. However, in both types of models the assumption is made that the serviceability design load should be an average walker with an average weight and walking characteristics. This approach disregards half of the occupants of a building who either weigh more than average, or walk with a heavier foot In many laboratories, experiments can last several hours or even days, where one exceedance of the vibration criterion can lead to significant loss of time and money.

A more realistic and flexible solution to this problem has been developed where a probabilistic approach is now taken. Using this methodology, hundreds of walkers are now considered and a probability of vibration criterion exceedance can be determined. This can be used to appropriately and optimally design a floor to ensure that sufficient structure is present to control vibrations for individual laboratory-specific criteria. The decision can now be made by the owners and the design team to target a performance level that is appropriate for any given application, and the cost implications of designing an average-performance versus a high-performance laboratory can be explored.

This approach will allow owners and design teams to produce a more optimal and sustainable structural design for laboratory buildings, and will allow for the reduction of construction material waste compared to traditional design practices.

Learning Objectives

  • Understand how vibration criteria for sensitive laboratory equipment can often drive the structural and architectural design of laboratory buildings.
  • Identify when a simplistic vibration prediction analysis is insufficient for a high-performance laboratory.
  • Learn how a probabilistic approach to vibration analysis of a building can lead to an optimal and more sustainable structure.
  • Understand the cost implications of designing either an 'average' or 'high' performance structure.

Biography:

A senior member of Thornton Tomasetti's acoustics, noise and vibration control engineering team, Dr. Wesolowsky has more than 10 years of experience in analysis, project management and design. Mike specializes in such areas as vibration studies for architectural and structural design, dynamic data acquisition and analysis, architectural acoustic studies and vibration control research and development. Mike joined Thornton Tomasetti in 2017 through its acquisition of Swallow Acoustic Consultants.

 

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