Vibrations in buildings: modeling and measurement

Last month, RWDI was pleased to host the Acoustics Week in Canada conference in Guelph, Ontario. This is the sixth in a short series of blog posts highlighting some of the research and insights shared by the acousticians and engineers.

Two papers presented by members of RWDI’s acoustics, noise and vibration (ANV) team shared findings from measurement programs conducted to determine how well accepted modeling approaches matched actual vibrations in particular building settings. One paper focused on how closely measured footfall vibrations conformed to predictive finite element modeling, while the other studied vibrations in a 17-storey building located above a subway line.

Footfall vibration. In any multi-storey building, vibrations caused by occupants’ footfalls on the elevated floors can cause problems – if only mild annoyance to people on the floors below. In advanced research facilities running highly sensitive equipment, it’s especially vital for designers to mitigate footfall vibrations so the labs can function effectively. Because the adaptations required to keep footfall vibrations to a minimum have to be developed in the building’s design phase, engineers need ways to accurately model the problem they’re trying to address before it exists. Finite-element analysis is widely viewed as the most accurate way of generating a predictive model. At the Acoustics Week in Canada conference, RWDI engineers Brizi Coetzer, Julia Graham and Steve Meszaros presented data they’d gathered to compare with a finite-element analysis. The three authors measured footfall vibration in a concrete floor in a partially completed quantum materials research facility in British Columbia, observing how well predictive modeling had anticipated the eventual vibration challenge.

Subway noise. As the world continues to urbanize and cities continue to densify, engineers will keep exploring how to make major urban infrastructure like subways coexist comfortably with commercial and residential land uses. So far, ANV specialists have developed many ways to model and predict how vibration from subway trains will affect multi-storey buildings – but considerable uncertainty remains about exactly how vibration travels through the ground, into building foundations, and up into occupied spaces. To shed light on how well vibration levels in an existing building conform to what models (generated using a range of methodologies) might predict, two members of RWDI’s ANV team, Mihkel Toome and Shayne Love, conducted measurements over a number of hours at multiple locations – from the subway tunnel itself to a given building’s foundation to three separate elevated floors inside the building. They shared their findings with conference participants, evaluating the differences and similarities between the various predictive models and the measured data.