Monday, December 07, 2015

Improving High Rise Building Structural Design

We don’t often get the opportunity to cover innovations in the structural design of high rise buildings because improvements are so often incremental. The development discussed below is perhaps most applicable to locations with high seismic loads, a topic put on my radar after my experiences living overseas.

Kinetica, a University of Toronto research spin-off, is attempting to bring a new product to market for damping seismic and wind loads in high rise structures. I’m not sure how much market demand exists for such an innovation as their work seems to have been heavily subsidized. Be that as it may, their technology indisputably offers benefits for the construction of concrete high rise buildings.

Comparing first steel structures; it’s a rather trivial process to place decoupling devices in either braces or walls because they’re exposed. However, with cost structures changing, more and more projects are utilizing concrete in high rise construction. The long thick walls which characterize concrete high rise construction lack areas to integrate high performance damping systems in. This leads to the use of heavy counterweights high above to dampen swaying. 

The damper braces introduced by the company are made of large sheets of a rubber-like material — known as a viscoelastic polymer — sandwiched between steel plates. (Seen in yellow in the above picture during the testing phasing.) They work by absorbing vibrational energy and transforming it into heat energy, thereby reducing the stresses transferred into adjacent structural elements. The company’s founders Michael Montgomery and Constantin Christopoulos’ key insight was “to realize that there was a place to put viscoelastic dampers into a concrete building after all: the coupling beams. These smaller, horizontal concrete beams are used on each floor to connect the two giant walls together and increase the rigidity of the building. Under high winds and earthquakes, these smaller coupling beams become heavily stressed, so replacing them with something that can absorb energy — like a viscoelastic damper — seemed like an ideal solution.”  

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