Timothy Schenck, writing for Engineering News Record, discusses the elaborate solution that was implemented during the Empire State Building’s retrofit in order to protect pedestrians:
When engineers made plans to reinforce and upgrade the carrying capacity of the Empire State Building’s mast and tower by adding 39 tons of steel, they had to find a way to protect pedestrians from falling rivets, tools and materials. Roofing the observatory and building bridges over the sidewalks 1,250 ft below were lousy options. The top of the iconic New York City building has an open-air observatory at the 86th floor and premium viewing spaces at the 102nd and 103rd levels. Annually, these spaces host about 4.3 million visitors and generate about $85 million in revenue. Soaring above the busy streets, a 200-ft-tall steel broadcast tower bristles with antennas that generate about $20 million more. Together, the observatory, mast and tower are the crowning jewel of the 86-year-old icon, which is owned by the Empire State Realty Trust Inc.
The search for an alternative to scaffolding dates to February 2014, when the ESRT’s building engineer, engineer-of-record Thornton Tomasetti, site safety engineer Plan B Engineering and contractor Skanska USA Building Inc. began to consult with New York City Dept. of Buildings officials to devise a plan that would not only protect the public and workers but also allow for the strengthening of the mast and tower without having to resort to sidewalk bridges.
They came up with a design for a sheltering “cocoon,” which sits on a 560-sq-ft aluminum elevated work platform, or “dance floor.” The platform is braced from below by steel brackets through the conical ice shield, which is there to shatter ice falling from the tower.
It just goes to show that proactive safety and risk management practices don’t have to be boring, and in fact, there is a lot of room for innovation in those areas.