clarification on the steel structure seismic analysis

Sir,

I am trying to qualify a existing steel structure for MCE condition with site spectra (model attached)

Analysis results showed a maximum displacement of around 255mm but the stress levels are with in limits. 

To reduce displacement , planning to provide some bracing members & additional EP support ( model attached) . 

Clarification / suggestions required on the following points.

1 . With the observed displacement of 255mm , it is correct to perform linear analysis. Doudt is whether linear analysis  gives wrong indication? 

2.  With the bracing + EP support , the displacement in model is reduced to the requirement limit. Whether this approach is correct.

 

STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 22-Jul-21
END JOB INFORMATION
INPUT WIDTH 79
UNIT MMS NEWTON
JOINT COORDINATES
1 0 0 0; 2 0 0 700; 3 0 0 750; 4 0 -500 700; 5 0 -600 700;
MEMBER INCIDENCES
1 1 2; 2 2 3; 3 2 4; 4 4 5;
DEFINE MATERIAL START
ISOTROPIC STEEL
E 205000
POISSON 0.3
DENSITY 7.68195e-005
ALPHA 1.2e-005
DAMP 0.03
TYPE STEEL
STRENGTH FY 253.2 FU 407.8 RY 1.5 RT 1.2
END DEFINE MATERIAL
MEMBER PROPERTY INDIAN
1 TO 4 TABLE FR ISMC150
CONSTANTS
MATERIAL STEEL ALL
SUPPORTS
1 FIXED
LOAD 1 LOADTYPE Dead  TITLE DL
SELFWEIGHT Y -1 
JOINT LOAD
4 FY -60
LOAD 3 LOADTYPE Live  TITLE SL(SSE)
JOINT LOAD
4 FZ 405
LOAD 5 LOADTYPE Live  TITLE SL(SSE)WITH -VE
JOINT LOAD
4 FZ -405
LOAD 9 LOADTYPE Seismic  TITLE EQX(SSE)
SELFWEIGHT X 1 
SELFWEIGHT Y 1 
SELFWEIGHT Z 1 
JOINT LOAD
4 FX 405
4 FY 405
4 FZ 405
4 FX 60
4 FY 60
4 FZ 60
SPECTRUM SRSS X 1 ACC DAMP 0 LIN MIS 0
20 1311.4; 4 1311.4; 2.85714 1663.3; 2.5 1785.8; 2.22222 2274.4; 2 2665.2;
1.66667 3039.6; 1.53846 3071.9; 1.42857 3918.7; 1.25 3987; 1.17647 4783.8;
1.05263 5576.7; 1 6227.5; 0.952381 6227.5; 0.869565 6627.7; 0.833333 7083.4;
0.8 7785.5; 0.740741 8205.3; 0.689655 9690.8; 0.666667 10830.2; 0.645161 13734;
0.625 15498.4; 0.588235 15976.4; 0.555556 19562.9; 0.540541 23149.4;
0.487805 32463.4; 0.47619 41230.3; 0.454545 49997.2; 0.425532 71228.4;
0.416667 87276.7; 0.4 105219; 0.338983 105219; 0.327869 108236; 0.3125 119504;
0.307692 127759; 0.285714 149554; 0.28169 158271; 0.273973 166989; 
0.263158 174140;
0.196078 174140; 0.192308 168813; 0.188679 158439; 0.186916 153393;
0.185185 148627;
0.183486 144423; 0.18018 129992; 0.178571 125182; 0.175439 108844;
0.173913 102126;
0.172414 98310.1; 0.169492 84569.5; 0.166667 80923.4; 0.165289 77277.3;
0.16129 70845.7; 0.16 65604.8; 0.15873 64148.4; 0.15625 62692;
0.152672 59434.3;
0.150376 57692.1; 0.148148 57084.6; 0.145985 55869.5; 0.142857 52951;
0.141844 52329.8; 0.13986 51708.6; 0.138889 51087.4; 0.136986 50991;
0.136054 52958.4; 0.134228 56113; 0.133333 61155; 0.131579 66197; 
0.12987 70245;
0.129032 72236.8; 0.128205 76220.5; 0.127389 76564.4; 0.0938967 76564.4;
0.0930233 76343.7; 0.0925926 76286.8; 0.0921659 76158.8; 0.0913242 76030.7;
0.0909091 75902.7; 0.0896861 74330.5; 0.0888889 73014.7; 0.0881057 72356.8;
0.0877193 71698.9; 0.0869565 70440.9; 0.0865801 70440.9; 0.0858369 70056;
0.0843882 70041.8; 0.083682 69720.7; 0.0829876 68851.6; 0.0823045 68417.1;
0.0809717 65290.1; 0.0806452 59884.6; 0.08 59063.5; 0.0796813 58242.4;
0.0793651 55791.9; 0.0787402 53398.4; 0.078125 51562.6; 0.0775194 50742.1;
0.0772201 49921.6; 0.0766283 48152.2; 0.0760456 46578.9; 0.0754717 45792.3;
0.0740741 43953.9; 0.0738007 42762.6; 0.0732601 41571.3; 0.0724638 40072.1;
0.0719424 39653.1; 0.0716846 39503.7; 0.0711744 39354.3; 0.0704225 38811.3;
0.0701754 38333.9; 0.0696864 38236.7; 0.0692042 38188.1; 0.0687285 38090.9;
0.0682594 37427.2; 0.0680272 37328.1; 0.0675676 37229; 0.0657895 37047.8;
0.0645161 36412; 0.0641026 36296.8; 0.0630915 35689.7; 0.0626959 35559.8;
0.0591716 35056.9; 0.0588235 34077.8; 0.0584795 33588.3; 0.0554017 33212.9;
0.0550964 33071.1; 0.0547945 33000.3; 0.0546448 32929.4; 0.0526316 32811.9;
0.0522193 32399.3; 0.0508906 32309.3; 0.0507614 32206.5; 0.050505 32103.6;
0.0503778 32000.8; 0.0496278 31922; 0.0492611 31773.9; 0.0483092 31603.7;
0.0465116 31542.5; 0.0433839 30959.8; 0.04329 30876.4; 0.030303 30211.3;
LOAD 10 LOADTYPE Seismic  TITLE EQY(SSE)
SPECTRUM SRSS Y 1 ACC DAMP 0 LIN MIS 0
20 808.8; 4 808.8; 2.85714 966; 2.5 1097.3; 2.22222 1328.8; 2 1494.3;
1.53846 1731.3; 1.42857 2004.2; 1.25 2061.9; 1.17647 2217.1; 1.05263 2361.5;
1 2411.3; 0.869565 2411.3; 0.740741 2759.8; 0.689655 2762.1; 0.666667 2985.5;
0.645161 3335.9; 0.625 3462.9; 0.588235 3508; 0.555556 3684.4; 0.540541 3860.8;
0.487805 5454.8; 0.47619 5948.4; 0.454545 6442; 0.425532 7885.3; 
0.416667 8852.2;
0.4 9823.9; 0.377358 10912.1; 0.37037 11714.5; 0.344828 13319.2;
0.338983 13751.8;
0.333333 13783.2; 0.3125 13783.2; 0.30303 14199.2; 0.285714 15975.4;
0.28169 16863.4; 0.273973 17751.5; 0.263158 19547.6; 0.25974 20621.5;
0.253165 21695.3; 0.246914 23581; 0.243902 24655.2; 0.238095 25729.5;
0.232558 27029.4; 0.229885 27926.3; 0.227273 29045.1; 0.224719 29266.9;
0.217391 29266.9; 0.212766 29348.2; 0.206186 31940.2; 0.204082 32964.3;
0.20202 35138.9; 0.192308 40893.5; 0.190476 41410; 0.188679 41668.2;
0.138889 41668.2; 0.136986 40248.3; 0.135135 38591.3; 0.134228 37817.9;
0.133333 37154.5; 0.13245 36711.4; 0.131579 36346.8; 0.130719 36139.4;
0.12987 36072.1; 0.129032 36692.2; 0.128205 37932.5; 0.127389 38469.3;
0.125786 38932.1; 0.0930233 38932.1; 0.0925926 38624.9; 0.0909091 38505.5;
0.0896861 37746.1; 0.0888889 37054.6; 0.0881057 36708.9; 0.0877193 36363.2;
0.0873362 36100.3; 0.0858369 35615.9; 0.0823045 35615.9; 0.0809717 35589.9;
0.0806452 34047; 0.08 33588.4; 0.0796813 33129.7; 0.0793651 31488.8;
0.0787402 30108; 0.078125 29196.9; 0.0775194 28663.6; 0.0772201 28130.2;
0.0766283 26953.4; 0.0760456 25697.4; 0.0740741 23468; 0.0738007 22750.1;
0.0732601 22032.2; 0.0727273 20857.3; 0.0724638 20422.3; 0.0719424 20000.4;
0.0716846 19813.5; 0.0711744 19626.6; 0.0704225 18882.6; 0.0701754 18457.5;
0.0687285 18391.6; 0.0682594 17761.7; 0.0680272 17721.5; 0.0657895 17541.5;
0.0645161 16536.6; 0.0641026 16362.9; 0.0634921 16002.7; 0.0630915 15675.4;
0.0626959 15511.7; 0.0591716 15314.7; 0.0588235 14593.4; 0.0584795 14232.8;
0.0576369 13707.8; 0.0574713 13576.7; 0.0571429 13445.7; 0.0568182 13183.6;
0.056338 13036.8; 0.0560224 12987.8; 0.0554017 12792; 0.0550964 12592.8;
0.0547945 12493.3; 0.0546448 12393.7; 0.0526316 11948.2; 0.0522193 11162.9;
0.0508906 11053.3; 0.0507614 10855.6; 0.050505 10657.8; 0.0503778 10460.1;
0.0498753 10221.5; 0.0496278 10161.9; 0.0492611 9921.5; 0.0486618 9801.4;
0.0483092 9610.9; 0.0465116 9485.9; 0.0462963 9264.8; 0.0460829 9154.2;
0.0458716 8933.1; 0.030303 7961.7;
LOAD 11 LOADTYPE Seismic  TITLE EQZ(SSE)
SPECTRUM SRSS Z 1 ACC DAMP 0 LIN MIS 0
20 1309.7; 4 1309.7; 2.85714 1535.1; 2.5 1751.5; 2.22222 2141.9; 2 2485.3;
1.66667 2769.2; 1.53846 3080.5; 1.42857 3471.4; 1.25 3619.8; 1.17647 4334.7;
1.05263 4934.8; 1 5122.2; 0.952381 5122.2; 0.869565 5123.7; 0.833333 5606.9;
0.8 6068; 0.740741 6701.6; 0.689655 7992.1; 0.666667 8868; 0.645161 10689.1;
0.625 11634.3; 0.588235 12126.5; 0.555556 14905.5; 0.540541 17684.5;
0.487805 22461.4; 0.47619 28287; 0.454545 34112.7; 0.425532 43014.1;
0.416667 49311; 0.4 55970.5; 0.377358 61544.6; 0.37037 68450.2; 
0.344828 82261.5;
0.338983 87627.6; 0.333333 89540.9; 0.28169 89540.9; 0.273973 90086.6;
0.266667 90086.6; 0.253165 92539.6; 0.246914 93985.7; 0.183486 93985.7;
0.181818 92863.1; 0.178571 91740.5; 0.175439 90786.8; 0.169492 90786.8;
0.166667 90186.8; 0.165289 89586.9; 0.16129 85604.1; 0.15873 78316.8;
0.15748 76357.7; 0.15625 75051.6; 0.153846 69953.9; 0.152672 67613.1;
0.151515 65688.2; 0.150376 64595.1; 0.149254 63701.9; 0.148148 63208.4;
0.145985 61234.4; 0.142857 57726.2; 0.141844 56833.2; 0.13986 55940.2;
0.138889 55047.2; 0.136986 51142.9; 0.134228 48512.8; 0.13245 47725.8;
0.131579 46938.8; 0.12987 45278.4; 0.126582 41708.6; 0.125 38827.5;
0.124224 37703;
0.123457 36946.8; 0.121951 36914.1; 0.110497 36914.1; 0.10929 36841.4;
0.108696 36189.5; 0.108108 34767.5; 0.106952 33275.6; 0.10582 31961;
0.104167 30570.3; 0.103627 29730.3; 0.102564 28534.7; 0.102041 28445.9;
0.10101 28357; 0.0943396 28357; 0.0938967 28336.3; 0.0930233 28116.3;
0.0925926 27873.4; 0.0921659 27693.8; 0.0913242 27514.2; 0.0909091 27334.6;
0.0896861 26947.5; 0.0877193 26909.2; 0.0873362 26879.5; 0.0865801 26868.6;
0.0858369 26405.7; 0.0851064 26239; 0.0843882 25905.7; 0.083682 25003;
0.0829876 24694.7; 0.0823045 24540.6; 0.0809717 23459.9; 0.0806452 22271.9;
0.08 22206.6; 0.0796813 22141.2; 0.0793651 21970; 0.0775194 21727.6;
0.0772201 21671.2; 0.0766283 21510.7; 0.0760456 21303.1; 0.0749064 21077.9;
0.0743494 21044.6; 0.0687285 21044.6; 0.0657895 20903.1; 0.0645161 20413.6;
0.0630915 20061; 0.0576369 19830.3; 0.0574713 19784.7; 0.0571429 19739.2;
0.0568182 19648.1; 0.0554017 19533.2; 0.0526316 19533.2; 0.0508906 19504.1;
0.0507614 19459.6; 0.050505 19415.2; 0.0503778 19370.7; 0.0465116 19170.2;
0.0449438 18948.4; 0.0414079 18948.4; 0.030303 18516.6;
LOAD COMB 20 LC1(SSE)
1 1.0 9 1.0 3 1.0 
LOAD COMB 21 LC2(SSE)
1 1.0 10 1.0 3 1.0 
LOAD COMB 22 LC3(SSE)
1 1.0 11 1.0 3 1.0 
LOAD COMB SRSS 23 LC4(SSE)
-1 1.0 9 1.0 10 1.0 11 1.0 -3 1.0 1
LOAD COMB 24 LC1(SSE WITH -VE SL)
1 1.0 5 1.0 9 1.0 
LOAD COMB 25 LC2(SSE WITH -VE SL)
1 1.0 5 1.0 10 1.0 
LOAD COMB 26 LC3(SSE WITH -VE SL)
1 1.0 5 1.0 11 1.0 
LOAD COMB SRSS 27 LC4(SSE WITH -VE SL)
-1 1.0 -5 1.0 9 1.0 10 1.0 11 1.0 1
PERFORM ANALYSIS PRINT STATICS CHECK
FINISH
FINISH