Group 8
Façade failure of the John
Hancock Building
“The Hancock”
• Construction completed
in 1976.
• 241m high.
• Tallest building in Boston
and the135th tallest in the
world.
• It’s fully glazed façade
was comprised of 10,344
windows.
• American Institute of
Architecture Award
(1977)
Problems with the Building
• Budget overrun, $75m to $175m
• Collapse of temporary retaining walls during
excavation….This caused damage to nearby
buildings, including the famous Trinity Church.
• Motion Sickness experienced by people in the
upper floors. A tuned mass damper costing $3m
was installed on the 58th floor to combat the
problem.
Façade Failure!!!
• January 20, 1973, building still under
construction.
• Winter Storm, gusts reaching 75mph at the
upper floors.
• The huge panels of glass, each weighing 500
pounds, fell off.
• Holes were covered with sheets of painted black
plywood.
• Over the next few months, more windows kept
falling off, nobody knew why!
Incorrect theories
• These theories erupted due a legal pact signed by all
parties involved in it’s construction, not to disclose what
really happened.
• The tower was swaying too much.
• The glass was sucked out by excessive wind forces at
“hotspots” caused the sharp angles of the tower’s
rhomboid shape.
• The windows stressed when the tower’s foundations
settled.
What really happened
• Each layer was a “sandwich”, two panes of glass
with an air space in between held together with
a metal frame.
• To cut the glare and heat of the sun, the inside
surface of the outside pane of glass was coated
with a reflective coating of chromium.
• The window frame was bonded to the chromium
with a lead solder.
• The lead solder was bonding too well with the
glass!!!
• Now the joint couldn’t absorb any
movement!
• But glass always moves as it expands and
contracts with temperature and vibrates
with the wind.
• So the solder fatigued and cracked, and
the crack continued through the glass.
Solution
• All 10,344 double-pane windows were replaced
with single sheets of tempered glass.
• The window maker covered the cost of $7m.
• The 5,000 undamaged windows that were
removed went on sale in bargain outlets in
Boston at $100 each!
Further Problems
• The architect needed further assurance the
building was safe, hired Thurlimann, the world’s
leading authority on high-rise steel frame
buildings.
• He announced under entirely possible wind
conditions, the building might fall over on it’s thin
side, despite it being built to every structural
code.
• Solution: The tower was stiffened from its base
to the top with 1,500 tonnes of diagonal steel
braces costing $5m.
Lessons learned
• The problem with the glass façade was
rectified and not used again in future
design.
• More research into structural behaviour.
• Greater understanding of high rise
structures due to the extensive testing the
Hancock building underwent.
The paradox
• After all the testing the Hancock
underwent, it must be one of the safest
high rises in the world!