Knowledge

Why are high-rise building windows so hard to break, even with a lot of force?

About 50 years ago, the 60 story John Hancock Building in Boston ( now called 200 Clarendon ) was constructed with over 10,000 multi-pane windows which during construction started popping out and under high winds.

The fallen windows were replaced with plywood until a solution could be found. We called it the Plywood Building. The owner sued the contractor who sued the architect who sued the engineer who sued the manufacturer who sued his mother-in-law.

After much research, all windows were replaced with single paned tempered glass to reduce thermal expansion and oscillations, which are of common use today.

I should also note that glass is very weak in tension (pulling forces) but extremely strong in compression (pushing forces), much stronger than steel. As a result, tempered glass is pre-compressed during fabrication, such that any tension forces are mitigated by the internal compressive stress.

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