How to subtract the weight of overlapping volumes in ETABS ?

[zineelabedine]

I'm modelling a high rise building, and need to know if there is an option for subtracting the weight of overlapping volumes between members ?

 

[MrHershey]

I'm not aware of anything other than doing it by hand. For unique cases I'd tend to get information out of ETABS into Excel or whatever and then adjust values myself so we're not doubling up on weight.

For beam/slab overlaps you could try going with a slightly thinner slab than you're actually providing with the reduction in thickness equal to the overlapping areas. Or slightly reduce any superimposed dead load you have applied to your slab to account for the overlapping. Important to keep track of what you're doing with this and be ready to clarify why you're doing it to anyone reviewing your model or calculations as it won't be obvious.

I tend to ignore it unless we're reviewing someone else's work and we're very close (but on the wrong side) of the working/not working threshold. For our own designs I usually leave the overlap in. Doesn't typically come out to much extra weight we have to contend with, and adds a little bit of conservatism into the design.

 

[zineelabedine]

MrHershey,

I wouldn't have given it so much value, if it weren't for the fact that this issue has a major effect on the calculation for the model i'm currently working on. Normally i would ignore it for the same reasons you just mentioned. Thanks for your input, much appreciate it.