Hi all,
I am doing a composite beam design right now. STAAD has some specific function to simulate the composite beam section. But when we do the 3D analysis design, if we put the concrete plate on the floor steel beam directly, should we still use this part to define the cross section? Based on my understanding, the deck and the floor beam will incorporate each other together based on their relative stiffness, does that mean the concrete deck can take some effect from steel beam, just like the composite beam design? Can anybody tell me if my assumption is correct? Thank you very much.
If the concrete plate is being modeled using finite elements, then, the steel beam ought to be assigned the pure steel non-composite cross section. Assigning it a composite section property when the floor is modeled using plates would mean that you are double counting the contribution of the slab.
By fragmenting the physical beam into a number of small length segments, and by meshing the slab adequately, you are
achieving a beam-slab system with a number of points of connection at all the nodes that are created along their common boundary. So, the more such nodes, the more the chances that the two entities will jointly participate in sharing the load. The total load transferred through any node is the shear in the beam plus the out-of-plane shear in the elements meeting at that node. The composite beam representation of this system was just a simplified way to simulate this behavior.
The drawback of modeling it as a beam-slab system is that the steel beam and the concrete slab have to be designed separately. The traditional rules for designing composite beams cannot be easily applied when they are modeled as separate entities.
Thanks SKLose. It is very helpful. :)
About the beam-slab system, can we manually define the one-way slab? Still don't quite understand how the plate load transfer to the connected beam. If we release the nodal freedom or ignore plate stiffness, does the load still go to beam? Thanks again. Appreciate it.