Response Spectrum Analysis as per Eurocode

Hello Experts,

I am not well versed with the dynamic analysis, since we could not perform linear static analysis for seismic load application as per Eurocode, Someone please guide me how to apply the response spectrum properly as per Eurocode.

I tried with the example EC8 frame from STAAD installation folder and did like that. Getting some of the following warnings.

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***WARNING: NO RIGID FLOOR DIAPHRAGM EXISTS FOR THE STRUCTURE.
RESULTS ON EARTHQUAKE MODE IN USER-INTERFACE MAY BE APPROXIMATE.

*** Note: ALL MASS RELATED WARNINGS, IF ANY, WILL BE WRITTEN IN _MASSEURO.TXT FILE.

** WARNING : NO MASS IS DEFINED AT LEVEL 12.00 MET . OUTPUT RESULT MAY BE ERRONEOUS.

** WARNING : NO MASS IS DEFINED AT LEVEL 23.70 MET . OUTPUT RESULT MAY BE ERRONEOUS.

** WARNING : NO MASS IS DEFINED AT LEVEL 33.43 MET . OUTPUT RESULT MAY BE ERRONEOUS.

** WARNING : NO MASS IS DEFINED AT LEVEL 34.56 MET . OUTPUT RESULT MAY BE ERRONEOUS.

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I was in a confusion that, whether I can neglect these warnings or how to get rid of them. It will be helpful if some Experts throw some light into this topic.

And for your reference, this is my input.

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CUT OFF MODE SHAPE 50
LOAD 1 LOADTYPE Seismic TITLE SEISMIC X
JOINT LOAD
1 FX 5.38
5 FX 6.54
18 FX 59.65
22 FX 55.84
35 FX 59.6
39 FX 54.2
52 FX 5.58
56 FX 8.27
69 FX 12.44
73 FX 12.44
86 FX 12.42
90 FX 12.42
103 FX 14.02
107 FX 14.03
120 FX 12.44
124 FX 12.44
137 FX 12.33
141 FX 12.33
163 FX 23.53
164 FX 24.16
165 FX 24.16
166 FX 23.53
2 FX 220.98
4 FX 215.71
19 FX 313.11
21 FX 304.23
36 FX 301.61
38 FX 294.23
53 FX 210.41
55 FX 206.72
70 FX 208.66
72 FX 208.65
87 FX 274.69
89 FX 274.68
104 FX 264.62
106 FX 265.24
121 FX 208.58
123 FX 209.22
138 FX 207.51
140 FX 207.51
**
1 FY 5.38
5 FY 6.54
18 FY 59.65
22 FY 55.84
35 FY 59.6
39 FY 54.2
52 FY 5.58
56 FY 8.27
69 FY 12.44
73 FY 12.44
86 FY 12.42
90 FY 12.42
103 FY 14.02
107 FY 14.03
120 FY 12.44
124 FY 12.44
137 FY 12.33
141 FY 12.33
163 FY 23.53
164 FY 24.16
165 FY 24.16
166 FY 23.53
2 FY 220.98
4 FY 215.71
19 FY 313.11
21 FY 304.23
36 FY 301.61
38 FY 294.23
53 FY 210.41
55 FY 206.72
70 FY 208.66
72 FY 208.65
87 FY 274.69
89 FY 274.68
104 FY 264.62
106 FY 265.24
121 FY 208.58
123 FY 209.22
138 FY 207.51
140 FY 207.51
**
1 FZ 5.38
5 FZ 6.54
18 FZ 59.65
22 FZ 55.84
35 FZ 59.6
39 FZ 54.2
52 FZ 5.58
56 FZ 8.27
69 FZ 12.44
73 FZ 12.44
86 FZ 12.42
90 FZ 12.42
103 FZ 14.02
107 FZ 14.03
120 FZ 12.44
124 FZ 12.44
137 FZ 12.33
141 FZ 12.33
163 FZ 23.53
164 FZ 24.16
165 FZ 24.16
166 FZ 23.53
2 FZ 220.98
4 FZ 215.71
19 FZ 313.11
21 FZ 304.23
36 FZ 301.61
38 FZ 294.23
53 FZ 210.41
55 FZ 206.72
70 FZ 208.66
72 FZ 208.65
87 FZ 274.69
89 FZ 274.68
104 FZ 264.62
106 FZ 265.24
121 FZ 208.58
123 FZ 209.22
138 FZ 207.51
140 FZ 207.51
SPECTRUM CQC EURO 2004 ELASTIC RS1 X 1 ACC DAMP 0.05 LIN DOMINANT 1
SOIL TYPE D ALPHA 0.12 Q 1.5
********************
LOAD 2 LOADTYPE Seismic TITLE SEISMIC Y
SPECTRUM CQC EURO 2004 ELASTIC RS1 Y 1 ACC DAMP 0.05 LIN
SOIL TYPE D ALPHA 0.12 Q 1.5
********************
LOAD 3 LOADTYPE Seismic TITLE SEISMIC Z
SPECTRUM CQC EURO 2004 ELASTIC RS1 Z 1 ACC DAMP 0.05 LIN
SOIL TYPE D ALPHA 0.12 Q 1.5
*****
PERFORM ANALYSIS
CHANGE

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Thanks in advance.