Staad Base reactions are differing

Question

Hi, 
 I am facing a problem with reference to the Staad pro v9i SS6. Please help in solving the same if its a known bug or a workaround is available. 
 I have imported the load data for seismic in all 6 directions (+/-X,+/-Y, +/-Z ) This is a Z up model and X & Y are Horizontal directions 
 When i am running the model with full loading, I get different reactions for +/-X & +/Y even though the inputted vaules summation are the same 
 Load Cases 
 8 SEISMIC_+X 9 SEISMIC_-X 10 SEISMIC_+Y 11 SEISMIC_-Y 12 SEISMIC_+Z 13 SEISMIC_-Z 
 Equipment Loading with self weight 
 
 Equipment Loading without Selfweight (all Values are matching in both directions Fx and Fy = 693.3 kN) 
 
 Only Self Weight

In the above it is very well seen that the Total Value needs to be 693.3 + 45.542 = 738.84 for all load cases (8,,9, 10, 11) but i am getting lower value for + / - Y Direction 
 which is actually 693.3 - 45.542 = 647.76 
 Kindly look into the issue and suggest possible solution. 
 
 Thanks 
 Ram

Sye · Accepted Answer

Looking at the screenshots you sent, here is what I see 
 
For your load cases 10 and 11, your equipment loading and selfweight are acting in opposite directions. For example if you consider the load case 10, applied equipment loading without self weight = -693 KN as seen from your second screenshot. For only self weight, the applied loading for load case 10 is 45.542 Kip as seen in the third screenshot. So when equipment loading + self weight is acting together, the load case 10 becomes = -693 KN + 45.542 KN = -647.458 KN which is what is shown in the first screenshot. Similarly one can arrive at the value for load case 11 as well.