huangyhg

shored or unshored composite construction?
do you generally design or specify shored or unshored composite steel construction? obviously, each has its drawbacks.
do you always do one opposed to the other? i'm curious what everyone's thoughts are.
at the firms i worked for, all composite constructon was unshored. i'm sure others do differently at times, but i think unshored is more common.
lol, there was only one shored job in the offices i worked for. some un-named engineer accidentally turned on the "shored" option in ramsteel and the entire job got designed as shored, but constructed as unshored. the error got by the designer, his supervisor who stamped it, the detailer, the shop drawing checker, the fabricator, and the erector. didn't get by gravity, though. those 34' long w12x14 didn't stand a chance when they dumped the concrete on there! pretty large building and it was all in teh air before they discovered the error.
we always design for unshored construction. my understanding is that it is much more expensive to shore beams than to add some steel weight.
we always us unshored construction for as well.
have always done unshored. seems to be the local norm.
i feel pretty sure if there was a cost savings in shored construction, several of our local contractors would not have hesitated to push for it. they are usually not too shy about those type of things.
generally unshored, but sometimes for thicker topping slabs, it is necessary to provide shoring and sometimes for beams, they are designed for a simple support post at mid span.
dik
unshored always. we have had to specify to shore the just the deck itself during construction when it was a very large single span.
just be sure to specify the design basis (shored or unshored) in your structural notes. having been around long enough to have experienced what happens when you don't shore floors designed as being shored, you really don't want to see what can happen. also be sure that the beams' compression flanges are adequately laterally braced, particularly if the metal doesn't provide adequate lateral bracing or there is no metal deck.
designed a suspended shoring system once for a formed concrete slab + composite steel beam floor - eor declared the beams did not require shoring. first concrete placement proved otherwise.

ralph
structures consulting

we also give the contractor a conservative estimate of dead load deflection so that he has no basis to ask for more money for additional concrete.
ralph:
i can see the beam would twist somewhat under the unbalance load from concrete pour. was that the case?
kslee:
that job goes way back. the problem was one of excessive deflection, both vertically and horizontally. the beams were very light sections and the slab was an early version of post-tensioned concrete. we ultimately shored the beams.

ralph
structures consulting

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