Written by Aleksandar Pavic.
A quarter of a century of my dealings with excessive vibrations of building floors under footfall loading has taught me that, once a floor experiences a vibration problem, fixing it is somewhere between quite hard and impossible. Options available to structural engineers, architects, building owners, tenants, and letting agents have always been very limited, often ineffective, highly disruptive, and prohibitively expensive. Such options include:
- adding a huge amount of structural mass, stiffening beams and/or additional columns
- installing heavy and not sufficiently effective tuned mass dampers, and
- installing constrained layer damping.
Those who did not want to put up with large bills to rectify their vibrating floor through structural modifications have had to put up with wobbly computer screens, visibly shaking potted plants, and rattling china whenever people simply walk around the floor. This phenomenon, happening hundreds of times per day, day-in-day-out, can affect concentration, productivity, and – generally – the wellbeing of the people occupying the floor. Occupants of one particularly problematic open-plan floor I worked on were resorting to taking motion sickness medication before going to work!
The advent of lightweight, slender and open-plan floors has only exacerbated this problem. A 2015 IStructE survey found that roughly a quarter of structural engineers have experienced issues with the vibration performance of structures they designed. Crucially, and worryingly, these were often floors that comply with current design guidance. I wrote about this at the SECED conference in 2019 – see Session 25 – Vibration serviceability, paper 25.7.
Throwing huge amounts of steel and concrete at the problem goes against all the principles of lean design which is woefully wasteful for today’s climate emergency state in which we all are and the urgent need to reduce embodied energy in construction.
There is a clear need for a new and better way to reduce vibrations in floors. After multi-£m investment in years of research and development, I am delighted that our FSD Active Ltd has brought to market a novel Active Mass Damper (AMD) to solve the problem of the lively floor for good.
Our patent-pending CALMFLOOR technology provides a huge amount of additional damping, far beyond anything seen on the market to date. When factored in at the design stage of a new building, we have shown how this autonomous mechatronics device could replace tens to hundreds of tonnes of traditional construction materials, such as steel and concrete, by increasing damping by 10 or more times. Our CALMFLOOR AMD makes use of the simple yet underappreciated fact that walking-induced forces are actually incredibly small compared with all other forces these structures are subject to. And yet, despite this, the few microns of oscillatory displacement they cause are not only perceptible to humans but annoying and even sickness-inducing. The CALMFLOOR system continuously monitors such tiny floor vertical vibrations and cancels them in a manner similar to noise-cancelling headphones, but on a huge scale.
Our brand new CALMFLOOR technology provides a timely opportunity to revolutionise how problematic vibrations in floors are solved. Get in touch today to find out more about how we can help you.