EDub24
Structural
- Mar 8, 2016
- 185
For seismic design, the IBC and ASCE 7 define a story as the 'portion of a building included between the upper surface of a floor and the upper surface of the floor or roof next above". So basically the story height would be the floor-to-floor dimension. However there is no definition of what the horizontal dimension would be. Typically it would be the horizontal dimension of the building perpendicular to the direction being considered (which usually matches the diaphragm length) however i'm working on a 2-story building where the 2nd floor doesn't extend the entire length of the building. We need a large crane to pick up large equipment and then lower onto trucks that can pull up on the bottom/1st floor. The 2nd story is more than 1/3 of the floor area so it doesn't meet the requirements of a mezzanine. When trying to determine the story drifts to check torsional irregularity and any amplification of accidental torsion I'm stuck on how to determine this. My understanding of the code language and the intent of the code tells me that for the 2nd story, the story height would differ on either end of the building (one end going down to the 2nd floor and the other end going down to the 1st floor since the 2nd floor doesn't extend all the way). The 1st story height would then just be the story height on either end of the 2nd floor diaphragm (see attached sketch). Does this sound reasonable? Has anybody else approached this issue differently or read the code in a different way? Thanks!
