2 Story Masonry Stair Tower - SDC D

[Galambos]

I have a steel, braced frame, two story building in a seismic design category D. the architect has chosen to put masonry stair towers in the corners of the building.

I need to isolate this tower from my braced frames. The only solution i can come up with is laterally supporting the first floor and carrying the walls above with the floor steel at the second floor. the concern is carrying this vertical load with no slab backspan at the openings.

Seems like an easy solution, but has anyone else gone a different route?

 

[a2mfk]

A better solution may be to ask the architect for additional services fees and redesign the lateral system to use those stair cores. You said a two story building but not the dimensions but stair towers at the corners is perfect for many two story buildings. Tell the architect how much money the owner will save in steel costs to help justify your additional services.

Not to be a fly in the ointment even more, but nobody knew about the need for fire protected stairwells (usually CMU or concrete) at the kickoff meeting or sometime early in design? Wondering how that got overlooked until you are almost done with your lateral design. Not saying its your fault....

 

[Galambos]

a2mfk,

agreed on both points. However, we were brought on late into DD's after the first engineer was forced out.

we need more masonry than the towers provide, and we've also been told more masonry isnt an option.

fortunately, we have been able to solve the problem.

 

[larsacious]

What about using a cold formed stud wall with the appropriate UL assembly to achieve your fire rating? This would be lighter and cheaper and easier to detail a separation to avoid transfering lateral load into the wall.