Don't use steel.

Seriously.

Although it would be difficult and expensive, there are other materials that have much higher melting/softening points than steel.

This thought reminds me of something I saw about a building fire years ago. It might have been on a TV show....

There was a tremendous fire in some old building somewhere. But the building didn't collapse because it was built with oak beams. The wood was chared but it retained its strength while steel I beams would have softened tremendously.

Of course finding enough oak beams to build a 110 story building would be a problem (assuming oak would have the strength necessary and that may be a bad assumption). But if fire and collapse become primary safety considerations in large buildings, then other materials will have to be considered. Maybe titanium alloys or something....

Cheers,
Scott.