Engineering
Cable Sag Effects in Long-Span Suspension Bridges Under Aerodynamic Flutter
Quick fact
In a long-span suspension bridge, the sag of the main cables can lower the bridge's flutter critical wind speed by up to 10-15%, meaning the bridge could become unstable in a wind storm that it otherwise would have survived if the cables were perfectly straight.
Why this is interesting
You might think that a heavy cable hanging between two towers is just a static, curved shape. But that slight curve, known as sag, can make a suspension bridge more likely to sway dramatically in the wind. How?