floor load Vs plate load

Question

dear friends, 
 what is the difference between floor load and plate load?Can't we use one of them as substitute of one another?if yes, in what case? 
 thanks in advance 
 yours truely

Sye · Answer

It is not that one is better than the other. The load you use would depend on the way you have modeled the structure. If you have modeled the floor using a mesh of plates, you would use floor load. If you have not modeled the slab but would like the pressure loading on the slab to be distributed to the supporting beams, you would use floor load. 
 Column getting designed or not getting designed may not be related to the meshing. Will need to take a look at the model. 
 The connectivity between the various element in a FEA model happens through the nodes. So unless the beams are segmented, there would be no connectivity between the plates and the beams and load transfer would not be correct. Even though the beams are segmented, these are still treated as continuous members for the analysis. 3a. Yes you have to do meshing. It is required to establish connectivity with other structural elements and ensure proper load transfer. 
 You would need to use a mesh of plates and not just 4 plates for 4 slabs. 
 The design may be failing to satisfy spacing requirements with that bar size. Model and more details needed to check further. 
 I think you are referring to offsets. You may use center to center modeling as that is simplest and widely accepted.

Sye · Answer

Tolu Alao: Floor Loads are applied on beam members and not on plates but if you are looking for an option to add pressure loading on plates, you can do so as shown next

Sye · Answer

You can definitely model the floor with plates and then also use floor loads to apply the loading. Modeling the floor with plates accounts for the stiffness due to the diaphragm. On the other hand floor load takes care of the distribution of the loading. Generally a more common approach is not to model the plates and apply the loads using floor load and then use FLOOR DIAPHRAGM to simulate the in plane rigidity offered by the diaphragm. 
 
The results of the two case will differ as the load distribution is different in each case. I would think if you apply the loading as a plate pressure loading as opposed to floor loading ( plates still being present even when applying the floor loading ) then the former would give you higher beam deflections and moments. You also should consider the fact that if you need to find out deflection within the slab, modeling the slab using plates and using the plate pressure load is the only option because if you apply the loading as floor load in this case, the load will directly go to the beam without getting to the slab.

Sye · Answer

Floor Diaphragm is actually a more sophisticated and automated solution compared to master slave and offers additional advantages like accounting for torsion in the rigid diaphragm. Section 5.28.2 of the Technical Reference Manual has more details on Floor Diaphragm.

Sye · Answer

If you are modeling the slabs and walls with plates then the only thing to ensure is that the nodes at the edges of the walls are aligned with the nodes for the plate mesh used for the slabs. You may want to create the walls first and then use the Parametric Models tool to create the mesh for the slabs so that wall nodes are considered as density points when the slab is meshed. 
 As far as modeling is concerned. both shear walls and partition walls have to be modeled with plate elements. When partition walls are used for separation and do not carry loads then you may not even model those and just consider the loads from these walls directly on the supporting elements.

Sye · Answer

The following wiki has more on offsets 
 https://communities.bentley.com/products/ram-staad/f/ram-staad-forum/200168/member-offset-consideration-in-model 
 If you have beams below partition walls, you would model them. Else you do not have to. 
 The Generate Mesh or Generate Plate Mesh would give you regular shaped quad plates whereas the Parametric Models would generate triangular meshing. So for regular shaped rectangular slabs, Generate Mesh is preferred as it allows you more control on the meshing and local axes of plates are oriented the same way. However for irregular shaped slabs or where you have columns or walls inside the slab at odd locations and the meshing for the slab needs to account for those entities for connectivity, you would have to go with Parametric Models. 
 For proper connectivity, you need to make sure that adjacent plates share common nodes 
 What mesh size to use depends on the structure and what the end goal of the analysis is. Finer mesh can give you more accuracy but increases the problem size. So you need to strike a balance, do some trials and find out which size works the best for your case. The following wiki has more information on mesh size 
 https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/25337/higher-stresses-with-reduced-mesh-size 
 If ground floor walls are supporting the beams/slabs, you need to model them. If not, and if considering the stiffness for those are not important for your analysis, you may ignore those and just consider the loads from those walls. 
 It is possible to design both strip and isolated footing. You may use the Foundation Design module ( STAAD Foundation Advanced ) for that. 
 Any surfaces would have to be modeled using a mesh of plates. We used to have Surface Elements in older versions which were specifically developed for modeling/designing shear walls but those have been deprecated. 
 Solid elements are generally used for modeling huge concrete block foundations (TG foundations, turbine foundations) and mass concrete structures like dams, piers for bridges etc.

Sye · Answer

Seems like you have modeled the slabs with a mesh of plates. So you should use the different plate loading options to apply loads from partition walls ( if those are not modeled). 
 Also please refer to the wiki below which would help answer connectivity questions 
 https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/20702/connectivity-issues

Sye · Answer

Yes you have to. You need to follow the same process you follow for the slabs. Also I would highly recommend that you go through a STAAD.Pro Training offered by Bentley.

Sye · Answer

At the end of these tutorial sets you will find one titled Modeling Finite Elements in STAAD.Pro. There is a practice workbook and dataset that you can use to practice what is being taught in these sessions 
 https://learn.bentley.com/app/Public/ViewLearningPathWithMasterCourseExpanded?lpId=111706&mcId=102943 
 Also there is a On Demand Webinar titled SIG Workshop: STAAD - Modeling Finite Elements which you should also look into

floor load Vs plate load

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