Space frame
Space frame
(OP)
Hi , For Space Frame ( 3D) analysis , what should be the member releases ( Release Mx , My , Mz) , i tried defining truss(3D) for members but it causes a error in output , " **WARNING - THERE WERE MORE THAN 12 DOF WITH ZERO STIFFNESS "
I think the Space frame members should be release at the starting node and end node of the member .
kindly advice ,
Thanks !!!
I think the Space frame members should be release at the starting node and end node of the member .
kindly advice ,
Thanks !!!





RE: Space frame
RE: Space frame
Sorry this post is a little late. Usually when model in STAAD I release MZ and MY on each end of the member. This will tell STAAD that it is not a moment connection but a simple shear connection. When you release these two moments you will have to supply horzontal and vertical bracing; if not than you will still get the same warning as you mentioned above and perhaps large deflections.
I really don't agree with SethGuthrie when he says that "at least one member connected to the node should not be released so that the node does not spin". It all depends what you release. Example, if you have a column and have a beam on each side of the column you can release MZ and MY to make the connections a simple shear connection. Again, you will have to supply bracing.
Hope this helps.
RE: Space frame
RE: Space frame
StructuralJay's reply ends with "Again you will have to supply bracing." As we know, in the real world, a omposite deck consist of a concrete slab (diaphram) connected to floor beams by the shear lugs welded to the top of the beam. The combination is a rigid horizonal member which transfer horizintal shear force to the columns which are braced to transfer the force to the foundation. Columns not braced do not transfer this horozontal load.
My question is how to provide "bracing" for a space frame to get rid of the 12 DOF warning without puting bracing in each of the four corners of my space frame with composite deck and bracing in a "core bay?