Please see the attached model.
I have defined self weight, applied loads and repeat loads. Repeat loads are basically my actual load cases. Thats is self weight and live loads applied a the same instance.
I have to perform analysis and do code check only for repeat load cases. This is important since i have defined compression only springs and therefore under live loads solution does not converge.
Two questions:
A) Are my compression only spring definition correct. I intended compression only springs in global Z direction and in global X and Y direction springs with relatively larger stiffness
B) Am i thinking correctly when i want to analyse repeat loads only. Is there a way to ask STAAD to analyse and do code check for repeat load cases only. I want to do this is because i think this way i wont run into errors / convergence issues, which is what i happens when analysis is performed live loads are analysed without self weight.
N8_Rpt_CS_20190210.std
You can analyze the primary load cases without the COMPRESSION ONLY support, then use the PERFROM ANALYSIS and CHANGE commands after the primary load cases and redefine the supports, but this time use the COMPRESSION ONLY support. In that case compression only will be used for the REPEAT LOADs only. A similar example can be found here (you should review the input file of it for a better understanding): https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/36525/modeling-base-plate-with-anchors-in-staad-pro
Alternatively, you could define your primary load cases in the Reference Load Definitions and then do the combinations using the Reference Loads.
Modestas,
appreciate your response.
Have a follow up questions
1) As i understand with "repeat loads" STAAD calculates a load vector from the loads which are part of he repeat load combination and then applies it. what you suggested above where i apply the primary load cases and then "change". That wont affect the load vector STAAD calculates under repeat loads, right ? Do I have even analyse the primary loads. Does staad require that ?
2) In reality what i ideally would like to do a is stage analysis. Wherein i apply dead loads (stage 1) and "compress" the compression only springs and then apply live load combination (stage 2). Any advice ?
3) Also another question is about the applying weights/mass as part of the stage 1 above. That is nodal mass or weights which become part of the dead load case. Can i do that in staad. And as i explained above after i apply the dead load+nodal weight, the springs compress and as a second stage i apply the live loads. Any advice on achieving this ?
1) All loadings in the REPEAT LOADS are combined and then analyzed, so it does not use the results of the primary load cases as simple LOAD COMB does. Primary load cases has to be analyzed, unless it is entered as Reference Loads.
2) I think using the PERFORM ANALYSIS and CHANGE commands after dead loads and the redefining the supports should serve this purpose.
3) Mass is required for the seismic analysis. You can enter mass as a Reference Load case with Mass type selected (in all 3 directions). Then this mass reference load case will be used in your static seismic or response spectra load case to generate the mass matrix.
Hi
i have tried this in one mode, its working fine. and same is applied in another model, and this time im facing issue of
**ERROR- SPRING TENSION/COMPRESSION SPECIFIED AT A JOINT DIRECTION THAT DOES NOT HAVE A SPRING DEFINED. JOINT= 2239 DOF= 2
More over i have assigned the springs as per Figure 5-29: Example for elastic mat generation for a convex polygonal shape
still i am facing this issue. any solution for this?