Hi,

I have to perform steady state dynamic analysis in frequency domain of a steel structure supporting two different compressors with different operating speeds.

I have unbalance loading, which is varying with square of machine frequency.

Question: Can I perform dynamic analysis of structure which is supporting different operating speed machines whose unbalance loading is varying with square of speed.

What would be the possible command for dynamic analys in staad since there are different operating speed machines?

The format of applying dynamic load is as below as per staad help is as follows:

Machine 1:

BEGIN HARMONIC FORCE

FREQUENCY FLO 1 FHI 80 NPT 5 MODAL

HARMONIC FORCE DAMP 0.03

JOINT LOAD PHASE Z 0

Unit KNS

927 FZ 0.00028

AMPLITUDE Z A 1 B 0 C 0

PRINT HARMONIC DISPLACEMENT LIST 14 20 21 28 29 923 924 927 TO 931 -

934 TO 937 942 943 950 TO 952

Machine 2:

BEGIN HARMONIC FORCE

FREQUENCY FLO 1 FHI 200 NPT 5 MODAL

HARMONIC FORCE DAMP 0.03

JOINT LOAD PHASE Z 0

Unit KNS

930 FZ 0.000106

AMPLITUDE Z A 1 B 0 C 0

PRINT HARMONIC DISPLACEMENT LIST 14 20 21 28 29 923 924 927 TO 931 -

934 TO 937 942 943 950 TO 952

Machine 3:

BEGIN HARMONIC FORCE

FREQUENCY FLO 1 FHI 36 NPT 5 MODAL

HARMONIC FORCE DAMP 0.03

JOINT LOAD PHASE Z 0

Unit KNS

931 FZ 0.000106

AMPLITUDE Z A 1 B 0 C 0

PRINT HARMONIC DISPLACEMENT LIST 14 20 21 28 29 923 924 927 TO 931 -

934 TO 937 942 943 950 TO 952