Waves and Vibrations below the collapse front

[cmcaulif]

As far as I understand it, and someone please correct me if I'm wrong, a column receiving a dynamic load and failing at the collapse front will transmit an impulse load to the lower structure, which cause elastic waves below the collapse front. Due to the fact that the impulse loads will be delivered eccentrically, flexural vibrations will be another result.

I have read some background info on waves, as well as Manuel Garcia's discussion on this, but is there any way to attempt to assess and predict what effect these will have on the lower structure in greater detail? I would imagine column splices and bolted connections would be most effected.

[Alferd_Packer]

The collapses initiated as buckling failures, so certainly the idea of a buckle wave propagating downward, ripping the floors from the angle clips is a valid one. As the mass of collapsed floors built up, it would have pushed outward on the exterior floors, and the critical failure would have been the floor clip connection. After that, the exterior walls were useless and unsupported.

[JamesB]

The collapses initiated as buckling failures, so certainly the idea of a buckle wave propagating downward, ripping the floors from the angle clips is a valid one. As the mass of collapsed floors built up, it would have pushed outward on the exterior floors, and the critical failure would have been the floor clip connection. After that, the exterior walls were useless and unsupported.

But would they go "clunkity-clunk" as they did so? That is what I want to know.

[steve s]

Also, some of the video and photos show that the perimeter curtain of the collapsing section had moved inside of the curtain of the lower section. It was just shearing off large portions of the outer curtain. The columns of the lower section weren't even supporting anything.

Steve S.