I have been doing Seismic Anaysis of buildings using Auto Lateral Load option, i have a question, while assigning the Seismic Defination (IS 1893-1984), I have applied seismic self weight, member weight & floor weight. Is it necessary to add Joint weight also??? What is the correct procedure for applying auto lateral load in Staad Pro for RCC Buildings?
I am using Staad Pro 2006.
Thanks in advance for my query..
No, it is not necessary to add Joint Weights in a seismic definition. The joint weight option is provided for instances where it may be convenient to use. One example that comes to mind is modeling the weight associated with connection material used in large gusset/bracing connections.
Fortunately, the procedure for applying seismic loads is the same regardless of the material/construction type.
Note that a new build of STAAD.Pro is now available for downloading from the SELECT site. It goes by the name STAAD.Pro V8i SELECT Series 1 and has the build number 20.07.06.23.
Thanks for your reply to my querry, I am attaching a STAAD file of seismic analysis done by me, please check, If I have done it correctly.
Thanks for your help,
It looks like your model will work. I am not familiar with the analysis requirements stipulated by IS 1893, but I am accustomed to seeing P-Delta analyses performed for concrete structures. So this would be a something for you to investigate.
If it turns out that you decide to implement a P-Delta analysis, then your load combinations should be created by using the REPEAT LOAD specification as opposed to the LOAD COMB spec. (REPEAT LOAD instructs the program to analyze the constituent load cases concurrently, for the proper determination of P-Delta effects, whereas LOAD COMB simply instructs the program to combine the results of the constituent load cases analyzed independently.)
And if you implement the REPEAT LOAD specs, then you will want to issue a PERFORM ANALYSIS and CHANGE command after each of your IS 1893 seismic load cases.
Thanks for your reply, I haven't used P-Delta Analysis so far. I will look further regarding P-Delta Analysis. If you have run my staad file, you may notice that, I am getting more column steel area in upper floors as compare to lower floors in few columns. Is it normal in case of seismic analysi?
thanks & best regards,
When I look at the version of the model you posted below, there are some columns where the moment due to lateral load is not significantly larger at the lower levels than it is at the upper levels. Thinking in terms of the shape of a typical column interaction diagram, I suppose it is possible that for a given moment value, the reinforcing requirements could actually be REDUCED as the design axial load is increased. This could be represented by the shift indicated on the interaction diagram below. In any case, your question underscores the importance of establishing the proper P-Delta analysis procedure with REPEAT LOAD cases before going too far with any concrete design results.