Twin Towers

[Xollob]

If only one tower had been hit on September 11, would the other tower have been able to withstand the impact as its twin collapsed?

[andy hughes]

I would suggest so. The design of each tower meant that the impact caused the tower to collapse on tiself, as opposed to falling over like a factory chimney, so one tower could have faalen, with minimal damage to the other one. This is a fact which I am sure the bombers investigated, and why they ensured there were two planes involved.

[Octavius]

I don't think buildings are designed like dominoes

[Peter Pedant]

yes it would have stayed standing

there is a web page somewhere - why the towers fell down - written by a physicist - which goes into the problems from a sensible physics point of view.

he also goes into why it didnt topple over, why the ruins were 10% of the volume of the standing towers and why they collapsed at free-fall speed.

[zmudge]

The structural system for the Twin Towers, deriving from the I.B.M. Building in Seattle, was impressively simple. The 208-foot wide facade was, in effect, a prefabricated steel lattice, with columns on 39-inch centres acting as wind bracing to resist all overturning forces; the central core taking only the gravity loads of the building. A very light, economical structure resulted and by keeping the wind bracing in the most efficient place on the outside surface of the building it did not transfer forces through the floor membrane to the core, as in most curtain-wall structures. Office spaces had no interior columns. In the upper floors there is as much as 40,000 square feet of column free office space per floor. The floor construction was of prefabricated trussed steel, only 33 inches in depth spanning the full 60 feet to the core, and also acting as a diaphragm to stiffen the outside walls against lateral buckling forces from wind-load pressures. It is quite probable that the ground vibration and heave from one tower falling could cause one storey of the other tower to collapse which would cause all floors above to begin to fall. The huge mass of falling structure would gain momentum, crushing the structurally intact floors below, resulting in catastrophic failure of the entire structure.  Whilst the columns at say level 50 were designed to carry the static load of 50 floors above, once one floor collapsed and the floors above started to fall, the dynamic load of 50 storeys above would be very much greater, and the columns would be almost instantly destroyed as each floor progressively "pancaked" to the ground.