hello guys, I NEED TO CHECK THE NON-LINEAR ANALYSIS LIKE P - DELTA EFFECT, CONSIDER I HAVE 25 STOREY BUILDING AND TOP OF the BULIDING I HAVE LUMPED MASS LOAD LIKE WATER TANK FOR THAT APPLIED MY AXIAL LOAD, AND I HAVE APPLIED 25 STOREY WIND LOAD (lateral load)ALSO LIKE (4, 8 , 12....102 M ) AND MY QUESTION IS IN P DELTA ANALYSIS WE HAVE NO OF ITERATION. AND THAT ITERATION IS NOT BUT WHAT, BECAUSE I CHECK-IN VERIFICATION EXAMPLE A SINGLE column ITSELF ITERATION GOES UPTO 4, AND WHICH EXTEND it CAN gO, ANOTHER DOUBT IS NO OF ITERATION IS NOTHING BUT NO OF STORIES OR WHAT. OR ELSE WE CAN TAKE EACH COLUMN AND APPLY NO OF ITERATION ,p - delta.std KINDLY GIVE SOME CLARITY I WILL ATTACH MY STD FILE KINDLY HAVE a LOOK
Generally 15 to 20 iterations of PDelta should be enough. To check for any divergence, you may run a test with 35 iterations. If the solution has converged you would not see any difference in results with increased number of iterations. For example for your model if you run with 15 iterations vs. 35 iterations, results would be same. You need to use REPEAT LOAD as opposed to LOAD COMB. Also PDELTA analysis is only relevant for cases where you have gravity and lateral loads acting together. A modified file is attached for your reference p - delta_rev.std
Answer Verified By: prashanth p
THANK YOU FOR YOUR CLARIFICATION AND MY DOUBT IS WHAT IF I HAVE ANY LUMPED MASS TOP OF MY STRUCTURES SHOULD I NEED TO CONSIDER THAT LUMPED GRAVITY LOAD WHICH I CONSIDER ON TOP OF STRUCTURES (POINT LOAD) p - delta_rev 1.std
Yes you should.
Ok sye and my last doubt is each storey we have to do the iteration process like each column and each storey like (25) and then 24like that or total storey which i had done before itself enough .. only need to check each storey deflection and moment (secondary) amd design
If you are asking whether you have to carry out separate pdelta analysis at each story level or not then the answer is no. Pdelta analysis is for the whole structure and the results from the analysis would include all second order effects for all members in all stories.