17 May 2012
Arup’s innovative structural engineering for Manhattan office tower 250 West 55th Street, which topped out on May 17th, is leading the way toward more efficient, cost-effective tall building design.
After the initial design of the 40-story building was complete, wind tunnel testing revealed an unacceptable level of wind-induced movement. Because conventional remedies — adding approximately 500 tons of steel to the building frame, or installing a massive tuned-mass damper on the top floor — would have raised the project’s cost by over $1M, we searched for a less expensive option.
Following extensive analysis, we decided to control wind movements with a damped outrigger system, which uses a series of viscous dampers to stabilize the relative movements of the building’s core and perimeter. Although viscous damping systems are common in seismic design, they have not often been used to control wind movements. 250 West 55th’s damped outrigger configuration will be the first of its kind in the United States.
This solution was substantially cheaper than both conventional alternatives — in fact, the new design allowed us to remove 500 tons of steel from the building frame. Integrating seven small viscous dampers into the mechanical space at the top of the building also preserved valuable space which would otherwise have been taken up by a tuned-mass damper.
The project team also saved the client time and money by maximizing the use of BIM. During the design, bidding, shop drawing review and fabrication phases we shared 3D models with the architect, SOM, along with the rest of the design and construction team, greatly expediting the design process and reducing RFIs.
Although 3D design is common practice at Arup today, this project, started in 2007, was among the first to employ it. Despite the fact that the effort was put on hold for two years after construction began due to the financial downturn, the use of BIM across the entire design and construction team is now paying dividends. The fully integrated 3D model has substantially reduced clashes and sped completion.