Hello,
What should i do in order to simply design my building for gravity loads.I am using the plate elements in my structure.How staad works out the loads from slab to beams?
Your question is very brief and general. It is not posible to furnish the full particulars. Only few lines I can spell out is that you will have to assign thickness and material property to plate. I believe you are aware of creating plates. Apply pressure as per plate load item. But before applying the load, plate has to be meshed so that plate load is transferred to the beam through the common nodes between plate and beam. I will suggest you to take the help of Technial Reference Manual and Staad Graphical to clear your doubts. One more thing that I feel it is better to simulate plate with the floor load and Master slave .If you are not applying lateral loads Master slave also may be omitted. Meshing of plate leads to poor management with the model.
sureshprsharma
yes i know the said thing but in actual practice we have different conditions for plate such as simply supported, fixed etc. then in space frame with the model say 3*3 bay both sides and height of building say 20 meter then in that case if i am using the plate element and applying the pressure then how to assigned the different conditions of plate. i think i have to separately design it or what ? The building may be of composite type
If by FIXED, you are referring to a monolithic connection between the beam and slab, here is a way to simulate that. Model the slab using a mesh of plates. Subdivide the beam into several segments. Ensure that those segments and elements are connected to each other at all those nodes which lie along the boundary between the beam and slab. The default connection between a beam segment and a plate element is treated by STAAD as one through which all three forces (FX, FY and FZ) and all 3 moments (MX, MY and MZ) are transmitted to each other which is what you would expect from a monolithic connection. Hence, other than the properties, material data and loads, there is nothing extra that you need to assign.
If the connection is not monolithic, meaning, if the slab is simply resting on the beam and does not transfer any moments to the beam, you could model the beam and slab at the elevations of their respective shear centers (or centerlines if that's what you prefer). This too requires that the slab is meshed and the beam is segmented. Then, use the master-slave feature to link the beam segment nodes to the element nodes along their boundary. The link will be just for FX, FY and FZ. By leaving out MX, MY and MZ, there will be no moment transfer. Without this additional step, the slab and beam would be identified as being physically separate entities with no connection, and no load transfer would be possible.
For designing the slab, the quickest way is to use the link between STAAD.Pro and RAM Concept. In the STAAD.Pro GUI's modeling mode, look for the tab called Advanced Slab Design. After the analysis, click on this page to launch the RAM Concept program if you have a license for it. If you don't have RAM Concept, you'll have to take the results from all those elements and design the slab manually, which can be quite tedious.
Dear Lose,
In paragraph 2 of your posting you have suggested to place the slab/plate in such a manner that top of slab and beam is at one level (global Y) with the nodes of beam and slab connected through master slave with appropriate rigidity so as to simulate the condition of simply supported. I do not find anything wrong with what you have suggested except that the modeling would be a bit complicated. In my view let the modeling be carried out on the lines of what has been advised by you in paragraph 1 of your posting and release the nodes connecting the beam and slab to simulate the condition of simply supported slab. If you do not agree with me, I would welcome your comments .
2. Is advanced slab design the only option to design slab? Staad is also designing slab as per some country code and giving output for reinforcement/steel for the sagging moment in the middle of the slab. It is also outputting moment at the nodes. What I feel the output generated by Staad in respect of RCC plate/slab almost satisfies 75% of the requirement of the designer to create quick design for the slab. I do not mean that further improvement in the design output for the slab is not required. As I have so far not come across advanced slab designer I am not in position to draw a comparison.
The reason I didn't suggest ELEMENT RELEASES is because when you release an element, it is not just the transfer of forces/moments between that element and the beam it is attached to that is halted, but also between that element and other elements it is connected to at that node. Since the elements form part of a single slab, you don't want a release between adjoining elements.
The element design feature available through the DESIGN ELEMENT command in the STAAD command file has two drawbacks in my opinion. a) Design is done only for MX and MY. Important checks like one-way shear and punching shear are presently not done. b) In the case of an irregular mesh where the elements can have local X and Y pointing in various directions, there is no common line of reference about which design is done. Instead, design is done for MX and MY as they are obtained from each element with no transformation of axis.
Both these limitations are overcome by using the advanced slab designer which is a very targeted solution for folks doing slab design. For those who don't have RAM Concept, there is another way. In the Concrete Design tab, which most people think is just for beam and column design, there is a slab design component too, though not as comprehensive as RAM Concept.