Sequence of Rayleigh Command

Question

Could you please let me know why placing the "Calculation Rayleigh Frequency" command in a different location within a load case makes a big difference in results. Please take a look at the two files attached. The frequency command is placed at the end of Load Case 101 in one file, while it is placed in the middle of Load Case 101 in the other file. Then, a factored load case (with Repeat load), Load Case 1, is followed for the steel design. It can be seen, based on Load Case 1, that the utilization ratios between two files are very different. 
 Note that the model in the file has been cut off from a larger model. Therefore, many nodes and elements shown in the command files are not graphically shown. Structure1_Frequencycommandatend.STD Structure1_Frequencycommandinmiddle.STD 
 Thank you, 
 Kasidit Chansawat

Modestas · Answer

The Rayleigh frequency command considers the loads which are entered above that command. The frequency calculated estimates the frequency as if the structure were constrained to vibrate in the static deflected shape generated by the loads in the load case which are above that command. So in your models, different loads are considered during the frequency calculation due to different location of the Rayleigh command.