crack control bars
we are reviewing a project where the owner wants to add additional loads of 10-12 psf on an existing floor. the framing consists of psi joists and soffit beams.
the joists are designed for a simply supported condition and we have provided
#5@12" oc over the soffit beams as crack control bars.
i am calculating a negative moment capacity based on the steel in the slab and am ending up with a moment capacity of the order of 35 k-ft. this in addition to the positive moment of the joists makes up for the total static moment based on the additional loads.
has anyone done something similar and are there any pointers?
thanks
if the joists are still simply supported after adding rebar to the top of the beams, there is no increase in the capacity of the joists.
the joists are supported on soffit beams with atleast a 4" bearing. i am assuming that this gives it some fixity.
the 4" weld at the top chord is still a simple span condition. for fixity, the bottom chord must be extended until attached to the opposite bottom chord or to the bearing wall or deep beam.
@civilperson:
timeout.....
this is a concrete prestressed joist. it is not an open web joist.