Sir,
I want to clear two situations of earthquake analysis in STAAD Pro:
First case:
I use load cases
1. EQ X Direction,
2. EQ -X Direction,
3. Eq Z Direction,
4. EQ -Z Direction,
5. Dead Load,
6. Live Load
And uses load combination as per IS code
1. 1.5 (5+6) i.e.1.5 (DL+LL)2. 1.5 (5+1) i.e. 1.5 (DL+ EQ in X +ve)3. 1.5 (5+2) i.e. 1.5 (DL+ EQ in X –ve)4. 1.5 ((5+3) i.e. 1.5 (DL+ EQ in Z +ve)5. 1.5 ((5+4) 1.5 (DL+ EQ in Z –ve)6. 1.2 (5+6+1) i.e 1.2(DL+LL+ EQ in X+ve)7. 1.2 (5+6+2) i.e. 1.2(DL+LL+ EQ in X-ve)8. 1.2 (5+6+3) i.e. 1.2(DL+LL+ EQ in Z+ve)9. 1.2 (5+6+4) i.e. 1.2(DL+LL+ EQ in Z-ve)10. 0.9 (5) + 1.5 (1) i.e. 0.9DL+ 1.5 EQ in X +ve11. 0.9 (5) + 1.5 (2) i.e. 0.9DL +1.5 EQ in X-ve12. 0.9 (5) + 1.5 (3) i.e. 0.9DL+ 1.5 EQ in Z+ve13. 0.9 (5) + 1.5 (4) i.e. 0.9DL + 1.5 EQ in Z-ve.
Second case:
2. Eq Z Direction,
3. Dead Load,
4. Live Load
1. 1.5 (3+4) i.e.1.5 (DL+LL)2. 1.5 (3+1) i.e. 1.5 (DL+ EQ in X)3. 1.5 (3-1) i.e. 1.5 (DL- EQ in X)4. 1.5 ((3+2) i.e. 1.5 (DL+ EQ in Z)5. 1.5 ((3-2) 1.5 (DL- EQ in Z)6. 1.2 (3+4+1) i.e 1.2(DL+LL+ EQ in X)7. 1.2 (3+4-1) i.e. 1.2(DL+LL- EQ in X)8. 1.2 (3+4+2) i.e. 1.2(DL+LL+ EQ in Z)9. 1.2 (3+4-2) i.e. 1.2(DL+LL- EQ in Z)10. 0.9 (3) + 1.5 (1) i.e. 0.9DL+ 1.5 EQ in X 11. 0.9 (3) - 1.5 (1) i.e. 0.9DL -1.5 EQ in X12. 0.9 (3) + 1.5 (2) i.e. 0.9DL+ 1.5 EQ in Z13. 0.9 (3) - 1.5 (2) i.e. 0.9DL - 1.5 EQ in Z
Above bot cases are correct and have same result or not.?
or I should use first case with some more load cases like:
14. 1.5 (5-1) i.e. 1.5 (DL- EQ in X +ve)15. 1.5 (5-2) i.e. 1.5 (DL- EQ in X –ve)16. 1.5 ((5-3) i.e. 1.5 (DL- EQ in Z +ve)17. 1.5 ((5-4) 1.5 (DL- EQ in Z –ve)18. 1.2 (5+6-1) i.e 1.2(DL+LL- EQ in X+ve)19. 1.2 (5+6-2) i.e. 1.2(DL+LL- EQ in X-ve)20. 1.2 (5+6-3) i.e. 1.2(DL+LL- EQ in Z+ve)21. 1.2 (5+6-4) i.e. 1.2(DL+LL- EQ in Z-ve)22. 0.9 (5) - 1.5 (1) i.e. 0.9DL- 1.5 EQ in X +ve23. 0.9 (5) - 1.5 (2) i.e. 0.9DL -1.5 EQ in X-ve24. 0.9 (5) - 1.5 (3) i.e. 0.9DL- 1.5 EQ in Z+ve25. 0.9 (5) - 1.5 (4) i.e. 0.9DL - 1.5 EQ in Z-ve.
The effect of reversing the load may not be the same as combining the load with a - 1 load factor for all structures. So I would go with the first set. The additional sets 14 to 25 may not be required as 14 in the final set would be covered by 3 in the first set and so on.
Thanks