About 40 years ago, I went to presentation at Structural Engineering Association of Illinois (SEAOI) on a rehab of one of O'Hare Airports Runways. They rehabbed about a 1/4 of it (1800 feet, if I'm remembering right) and this was a major project.
What surprised me and the guy I went with was that the controlling case for runways is the takeoff section. This is because:
[ul]
[li]All the planes take off from the same starting point, while planes land in a band of a thousand feet or so.[/li]
[li]The planes are heaviest when they're filled with fuel.[/li]
[li]Planes touch down pretty lightly.[/li]
[/ul]
Anyway, I've never designed a runway, but that stuck with me.