Design Spectrum for elastic Analysis

Dear Engineers

I have a question regarding designing Seismic using EC8-2004 where the problem for output of Shape Elastic Response Spectrum in staad pro with manual calculation to develop Shape of the elastic response spectrum are different. Please give some technical advice for me more understanding how system run the analysis.

Thanks

Parents
  • Please describe the issue in details. What are the differences which you see? Can you illustrate it with a screenshot? Which STAAD.Pro version are you using? Can you attach the related STAAD.Pro model?



  • For your information, I just run the seismic design by using Staad Pro step for EC8 codes. Then what I can see is the input data that Staad Pro developed for the elastic response spectrum are different from my manual design output data (the shape of the graph is still the same). I'm using Staad Pro connect edition version V22 update 12.

  • PDF

    Here the manual calculation then compare this Staadpro model show that the value to developed the Response Spectrum Analysis are not same.

    Here sample from std file:

    STAAD SPACE
    START JOB INFORMATION
    ENGINEER DATE 19-Jun-08
    END JOB INFORMATION
    INPUT WIDTH 79
    UNIT METER KN
    JOINT COORDINATES
    1 0 0 0; 2 3 0 0; 3 6 0 0; 4 9 0 0; 5 0 0 3; 6 3 0 3; 7 6 0 3; 8 9 0 3;
    9 0 0 6; 10 3 0 6; 11 6 0 6; 12 9 0 6; 13 0 0 9; 14 3 0 9; 15 6 0 9; 16 9 0 9;
    17 0 3 0; 18 3 3 0; 19 6 3 0; 20 9 3 0; 21 0 3 3; 22 3 3 3; 23 6 3 3; 24 9 3 3;
    25 0 3 6; 26 3 3 6; 27 6 3 6; 28 9 3 6; 29 0 3 9; 30 3 3 9; 31 6 3 9; 32 9 3 9;
    33 0 6 0; 34 3 6 0; 35 6 6 0; 36 9 6 0; 37 0 6 3; 38 3 6 3; 39 6 6 3; 40 9 6 3;
    41 0 6 6; 42 3 6 6; 43 6 6 6; 44 9 6 6; 45 0 6 9; 46 3 6 9; 47 6 6 9; 48 9 6 9;
    49 0 9 0; 50 3 9 0; 51 6 9 0; 52 9 9 0; 53 0 9 3; 54 3 9 3; 55 6 9 3; 56 9 9 3;
    57 0 9 6; 58 3 9 6; 59 6 9 6; 60 9 9 6; 61 0 9 9; 62 3 9 9; 63 6 9 9; 64 9 9 9;
    65 0 12 0; 66 3 12 0; 67 6 12 0; 68 9 12 0; 69 0 12 3; 70 3 12 3; 71 6 12 3;
    72 9 12 3; 73 0 12 6; 74 3 12 6; 75 6 12 6; 76 9 12 6; 77 0 12 9; 78 3 12 9;
    79 6 12 9; 80 9 12 9; 81 0 15 0; 82 3 15 0; 83 6 15 0; 84 9 15 0; 85 0 15 3;
    86 3 15 3; 87 6 15 3; 88 9 15 3; 89 0 15 6; 90 3 15 6; 91 6 15 6; 92 9 15 6;
    93 0 15 9; 94 3 15 9; 95 6 15 9; 96 9 15 9;
    MEMBER INCIDENCES
    25 1 17; 26 2 18; 27 3 19; 28 4 20; 29 5 21; 30 6 22; 31 7 23; 32 8 24;
    33 9 25; 34 10 26; 35 11 27; 36 12 28; 37 13 29; 38 14 30; 39 15 31; 40 16 32;
    41 17 18; 42 18 19; 43 19 20; 44 17 21; 45 18 22; 46 19 23; 47 20 24; 48 21 22;
    49 22 23; 50 23 24; 51 21 25; 52 22 26; 53 23 27; 54 24 28; 55 25 26; 56 26 27;
    57 27 28; 58 25 29; 59 26 30; 60 27 31; 61 28 32; 62 29 30; 63 30 31; 64 31 32;
    65 17 33; 66 18 34; 67 19 35; 68 20 36; 69 21 37; 70 22 38; 71 23 39; 72 24 40;
    73 25 41; 74 26 42; 75 27 43; 76 28 44; 77 29 45; 78 30 46; 79 31 47; 80 32 48;
    81 33 34; 82 34 35; 83 35 36; 84 33 37; 85 34 38; 86 35 39; 87 36 40; 88 37 38;
    89 38 39; 90 39 40; 91 37 41; 92 38 42; 93 39 43; 94 40 44; 95 41 42; 96 42 43;
    97 43 44; 98 41 45; 99 42 46; 100 43 47; 101 44 48; 102 45 46; 103 46 47;
    104 47 48; 105 33 49; 106 34 50; 107 35 51; 108 36 52; 109 37 53; 110 38 54;
    111 39 55; 112 40 56; 113 41 57; 114 42 58; 115 43 59; 116 44 60; 117 45 61;
    118 46 62; 119 47 63; 120 48 64; 121 49 50; 122 50 51; 123 51 52; 124 49 53;
    125 50 54; 126 51 55; 127 52 56; 128 53 54; 129 54 55; 130 55 56; 131 53 57;
    132 54 58; 133 55 59; 134 56 60; 135 57 58; 136 58 59; 137 59 60; 138 57 61;
    139 58 62; 140 59 63; 141 60 64; 142 61 62; 143 62 63; 144 63 64; 145 49 65;
    146 50 66; 147 51 67; 148 52 68; 149 53 69; 150 54 70; 151 55 71; 152 56 72;
    153 57 73; 154 58 74; 155 59 75; 156 60 76; 157 61 77; 158 62 78; 159 63 79;
    160 64 80; 161 65 66; 162 66 67; 163 67 68; 164 65 69; 165 66 70; 166 67 71;
    167 68 72; 168 69 70; 169 70 71; 170 71 72; 171 69 73; 172 70 74; 173 71 75;
    174 72 76; 175 73 74; 176 74 75; 177 75 76; 178 73 77; 179 74 78; 180 75 79;
    181 76 80; 182 77 78; 183 78 79; 184 79 80; 185 65 81; 186 66 82; 187 67 83;
    188 68 84; 189 69 85; 190 70 86; 191 71 87; 192 72 88; 193 73 89; 194 74 90;
    195 75 91; 196 76 92; 197 77 93; 198 78 94; 199 79 95; 200 80 96; 201 81 82;
    202 82 83; 203 83 84; 204 81 85; 205 82 86; 206 83 87; 207 84 88; 208 85 86;
    209 86 87; 210 87 88; 211 85 89; 212 86 90; 213 87 91; 214 88 92; 215 89 90;
    216 90 91; 217 91 92; 218 89 93; 219 90 94; 220 91 95; 221 92 96; 222 93 94;
    223 94 95; 224 95 96;
    DEFINE MATERIAL START
    ISOTROPIC CONCRETE
    E 2.17185e+07
    POISSON 0.17
    DENSITY 23.5616
    ALPHA 1e-05
    DAMP 0.05
    END DEFINE MATERIAL
    MEMBER PROPERTY AMERICAN
    25 TO 224 PRIS YD 0.4 ZD 0.4
    CONSTANTS
    MATERIAL CONCRETE ALL
    SUPPORTS
    1 TO 16 FIXED
    LOAD 1 LOADTYPE None TITLE LOAD CASE 1
    SELFWEIGHT X 1
    SELFWEIGHT Y 1
    SELFWEIGHT Z 1
    SPECTRUM CQC EURO 2004 DESIGN RS1 X 1 ACC DAMP 0.05 LIN SAVE
    SOIL TYPE E ALPHA 0.151 Q 3.9
    LOAD 2 LOADTYPE None TITLE LOAD CASE 2
    SPECTRUM CQC EURO 2004 DESIGN RS1 Z 1 ACC DAMP 0.05 LIN SAVE
    SOIL TYPE E ALPHA 0.151 Q 3.9
    PERFORM ANALYSIS
    FINISH

  • What soil class are you considering in your manual calculations? In your STAAD model, soil class E is used. However, if we change the soil class to A, the response spectrum values become quite similar. Make sure that the same soil class is considered in STAAD model and your manual calculations.



  • For your remark that the soil class chosen by class E. Can you check the value for Period and Acceleration in staadpro for soil type E with design ground acceleration and behavior factor is 0.151 and 3.9. 

  • In my opinion, the response spectrum accelerations in your calculations are not multiplied by soil factor S=1.4 for the soil type E. If you would multiply your spectra by 1.4, the resulst will be close to STAAD.

      



  • For your information, my response spectrum acceleration is multiplied with soil factor S=1.4. But the value for Design Ground Acceleration in STAADPRO is for ag value not ag.S. It is right? My manual calculation is ag.S that I put in Design Ground Acceleration in STAADPRO. After redo back so my manual are same as STAADPRO value.

    Sir, one more thing can you share the file on how STAADPRO runs DESIGN RESPONSE SPECTRUM with completion mode in EC8.

Reply
  • For your information, my response spectrum acceleration is multiplied with soil factor S=1.4. But the value for Design Ground Acceleration in STAADPRO is for ag value not ag.S. It is right? My manual calculation is ag.S that I put in Design Ground Acceleration in STAADPRO. After redo back so my manual are same as STAADPRO value.

    Sir, one more thing can you share the file on how STAADPRO runs DESIGN RESPONSE SPECTRUM with completion mode in EC8.

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