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?
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.
Hi All,
When modeling like this, there is a large axial force in the beams, which is not realistic
How can we overcome this problem ?
The reason a beam develops an axial force is, the two ends of a beam move by different distances resulting in a relative displacement along the local X axis between the 2 ends. So, if you can prevent or minimize this relative deformation, the axial force can be prevented.
To achieve this, you'll either have to release FX at one end, or provide a very large value for AX (the cross section area). You can find a discussion on a similar topic at
communities.bentley.com/.../166243.aspx
Is it realistic to release the beam at one end ?
Is it due to the method of reporting of STAAD ?
Dear SKLOse,
I refer to your posting dtd. Mar 25 2011. Is it not possible to control the differential displacement of the two nodes of the beam in the local X direction with the help of Master Slave so that axial force is not developed in the beam?
hmmbe,
You asked if it is realistic to release a beam at just one end. A release is simply a reflection of the connection details at that joint. So, there should be no problem with a release at one end, if the connection at that end represents a condition which is different from the default.
sureshprsharma,
Using master-slave to prevent axial deformation sounds like a logical approach, provided the member also is parallel to one of the global axes. This is because the master-slave feature in STAAD allows for linkages to be along the global axes only.