Hi, I need help defining seismic loads by using the response spectra line graph. I add seismic periods and accelerations in the 'Load Case Details' section (attached image). I did not use the 'Definitions' section to consider seismic. My question is how to add loads to gather seismic loads in load case 12. I have used repeat load. Is this approach correct?
You need to create mass modelling over here. You need to defined the loading for dead load of the model along with required % of LL in X, Y and Z direction in the RS load case. There has been another option of defining this loads in mass reference load case. If you have a mass reference load case, the program will from mass matrix on the basis of that loading that will be used in RS loads.
Thank you for replying. What I understand: In the 12 Load case ( RS) I have to add dead loads and other necessary loads in 3 directions by the required %. And repeat loading method is not correct.
Yes, you are correct.
Answer Verified By: lachin nuriyev
Excuse me...
THE FINAL MASS MATRIX FOR DYNAMIC ANALYSIS.
EIGEN METHOD : SUBSPACE
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NUMBER OF MODES REQUESTED = 300
NUMBER OF EXISTING MASSES IN THE MODEL = 38229
NUMBER OF MODES THAT WILL BE USED = 300
Does it mean the analysis is not correct?
Response to Q-1. Please check if % of the sum of mass participation in the direction of application of RS loads is at least 90%. if not, increase the number of codes to be considered in the analysis. It is evident that program is not facing any problem in modal analysis.
Response to Q-2. It is suggested that you apply permanent plate loading in Global direction and then use them in mass modelling in three orthogonal directions.
Thank you! but this structure is a storage tank (circular) and that means Hydrostatic pressure acting on local axis in the tank wall (vertical plates). My only choice is to apply loads on local axis