Leo didn't finish his espresso. He bolted out the door, waving the envelope like a white flag. He reached the foreman just as a loud crack echoed through the street.
The foreman looked at the frantic physicist, then at the envelope covered in scratched-out numbers and coffee stains. He looked up at the girder, which gave another ominous groan. He didn't ask for a peer-reviewed study; he grabbed his radio. Back-of-the-Envelope Physics
: The wind was gusting. The girder was oscillating about 5 degrees from the vertical. Leo scribbled a quick triangle. The centripetal force at the bottom of the swing would add to the tension. Estimate : At that height and arc, the velocity was maybe Leo didn't finish his espresso