Accurately measuring floor vibrations typically requires highly calibrated (and very expensive) equipment, but from time to time it is useful to take a quick measurement of the vibration of a floor, before embarking on a fully instrumented investigation.
Recognising that most smartphones now include serviceable accelerometers – a type of sensor used to measure vibration – Arup has developed a smartphone app for measuring vibrations by placing the phone on the vibrating surface. The app is intended to be a handy tool for preliminary, quick-look vibration measurements in the field, and does not replace subsequent more detailed measurements using traditional technology.
The app, FOOTFALL, can be used for preliminary on-site vibration testing in buildings, floors, stairs and footbridges.
The FOOTFALL app provides the following:
- a dominant natural frequency of the floor
- the response factor and response factor time history, a measure of vibration intensity
- the ability to email the recorded raw data to the user for further processing.
The app has been benchmarked against calibrated equipment and shows a good correlation for typical natural frequencies of floors and stairs. It captures response factors in the range expected for buildings and footbridges.
The app is available for download from the Apple iTunes store. The current release is for iOS, with development earmarked for Android devices.
Users of the app can undertake a preliminary investigation of vibration levels in offices, stairs or footbridges without the need for specialist testing equipment. Users can evaluate results instantly on their smartphone and send the results via email for analysis back at the office. Results are also stored in a database, creating a data resource.
Building owners, operators and potential clients can use the app to gain insight into the performance of their buildings and bridges. Technical specialists and members of the public will find the app useful tool, as well as being a valuable educational resource centred around vibrations in the built environment.
The FOOTFALL app enables quick initial vibration measurements in the field. This makes preliminary vibration testing much more accessible. Previously, this was only available as a specialist service offered by a specially-equipped team.
Whilst the app is not intended to replace a more formal vibration test, it allows for preliminary tests to be undertaken with minimal preparation beforehand, and is an invaluable asset for preliminary site surveys.