John Hancock Building Façade Failure Group 8 Design Architect – Henry Cobb of I.M Pei, Boston 1.7 acre site in Copley Sq Boston 60 stories high Reflective blue tinted glass Pin strip geometry Construction 1968 - 1976 Glazed curtain walls (hold no floor loading) Failure! During contruction 20th Janurary 1972 75 mph gusts 65,500 lb glass panels shattered Solution 10,344 panels were replaced with single pane panels Costing the window company $7 million Why? The building did vibrate but this was not the main cause. Failure was due to the double paned windows that failed due to a design defect. It was still thought the building might fall? Vibration was solved by adding a “tuned mass damper” Prevention of the building tipping during stiff wind $5 million reinforcement was added consisting of 1,500 tonnes of steel bracing ,these were placed along the walls at the core of the building. How did such a big mistake happen? It was discovered that the developers had opted for less expensive aeronautical tests which didn’t stimulate gusty winds. Lesson Engineers when looking at the wind effects of a building should also look at the envelope. Cost cutting could be crucial.