Does Staad take the floor load and apply it directly to the beams even if a slab is entered? Graphically in the GUI it appears like the floor load is distributed to the beams correctly, however the shear/moment diagrams do not appear to be correct.
please see attached word document with some screen shots. Any suggestions?
When beams and plates are connected through common nodes, the load is resisted by the two entities together, regardless of whether the load is applied on the beam or on the plate.
In your model, the member group B1 is attached throughout its length to the slab. If you specify a PRINT ELEMENT FORCES command for those elements which share the boundary with B1, the program will report the moment about the global X axis for those elements at those common nodes. You'll notice that those MX moments are non-zero values, indicating that the beam is being propped up to some degree by the slab.
There are also a couple of other aspects at work here.
1. At one of the ends of B1, you have specifed not a full release, but a partial release of 0.9999. A small MZ moment is developed as a result of the minute stiffness that is available by the 0.0001 factor of restraint. This prevents the beam from displacing like a complete simply supported beam.
2. You have grouped the floor loads on the entire slab into a single load case. If you break it up into 4 separate cases, you'll see that Loads on regions at some distance away from B1 produce effects transmitted through the slabs due to which moments (small, but non-zero) are formed on the top side of B1 at node 5444.
3. At node 5444, the slab provides sufficient stiffness to produce a moment on the top side of B1. This reduces the amount of moment that can form on the underside of B1.
4. If you isolate the following floor load into a single load case
YRANGE 0 0 FLOAD -0.1 XRANGE 60 150 ZRANGE -10 41 GY
you'll see that the moment on segment 2205 is almost 44 kip-ft.
Based on all this, the assumption that B1 should develop a 64.5 kip-ft moment at its mid-span is not fully justified.
A few other suggestions.
In the command
YRANGE 0 0 FLOAD -0.15 XRANGE 0 60.1 ZRANGE -10 100 GY
the upperbound for XRANGE should be changed from 60 to 60.1
YRANGE 0 0 FLOAD -0.15 XRANGE 54 150 ZRANGE 30 44 GY
is 54 correct for the lower bound of XRANGE? There is a beam at X=53.336, and the next row of beams is at X=60.003.