1. What is the difference between an open web steel joist and a plain steel joist? Which is a better approximation for typical steel construction of Wide Flange beams and composite concrete floor?
2. How should penetrations through the floor be handled in calculation of square footage? I'm working under the assumption that large openings, such as atria, will not be counted, but that smaller ones like elevator shaft penetrations are.
Whit Faulconer
Director – LEED Technical DevelopmentUSGBC
51 thumbs up
April 1, 2011 - 2:36 pm
Laura,
I'm going to guess, because I think I know, and then have someone check my answer. An open web beam is one that has had excess material machined from it so that it will be lighter. It likely has a less load bearing capacity as a result, but the goal is probably material efficiency much like a fancy tennis racket or bicycle. It creates a web like pattern of holes where the material was removed.
Your assumptions in #2 sound correct, but I will have to get back to you on the square footage question, it seems too small to matter, but cumulatively it may be significant enough to take the area of the lost floor area and multiply it by the number of penetrations and subtract from the total area. Seems like we are not looking for the typical interior area measurements for room square-footage, but rather the material surface area square-footage.
That's a big fat guess though and I will have Brendan or someone else may weigh in before i get back to you. Just wanted to let you know we hear you! -whit
Kelly Roberts
PrincipalWalter P Moore
29 thumbs up
June 23, 2011 - 4:12 pm
I just wanted to add that it is also very unclear to me which assembly is a better approximation for typical steel construction of wide flange beams and composite concrete floor. You'd think that for such a typical construction assembly, there'd be a clear-cut choice.