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Instability in the direction of Fz Please help me to solve this

Vasanthakumar
Offline

Dear sir,

I am getting the warning as instability in the direction of Fz.Please help me solve this.

I am not able to understand the instability problems.Please help me

STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 14-Jun-16
END JOB INFORMATION
INPUT WIDTH 79
UNIT METER KN
JOINT COORDINATES
1 0 0 0; 2 3 0 0; 3 0 2.629 0; 4 3 2.629 0; 5 0 0 3.8; 7 3 0 3.8;
8 3 2.629 3.8; 9 0 2.629 3.8; 10 3 2.629 0.95; 11 3 2.919 0.95; 12 3 2.629 1.9;
13 3 3.209 1.9; 14 3 2.629 2.85; 15 3 2.919 2.85; 16 0 3.209 1.9; 17 6 0 0;
18 6 2.629 0; 19 6 0 3.8; 20 6 2.629 3.8; 21 6 2.629 0.95; 22 6 2.919 0.95;
23 6 2.629 1.9; 24 6 3.209 1.9; 25 6 2.629 2.85; 26 6 2.919 2.85; 27 9 0 0;
28 9 2.629 0; 29 9 0 3.8; 31 9 2.629 0.95; 32 9 2.919 0.95; 33 9 2.629 1.9;
34 9 3.209 1.9; 35 9 2.629 2.85; 36 9 2.919 2.85; 37 12 0 0; 38 12 2.629 0;
39 12 0 3.8; 40 12 2.629 3.8; 41 12 3.209 1.9; 47 0 0 0.154; 48 0 0 1.304;
49 0 0 2.696; 50 0 0 3.646; 52 3 0 0.154; 53 3 0 1.304; 54 3 0 2.696;
55 3 0 3.646; 56 6 0 0.154; 57 6 0 1.304; 58 6 0 2.696; 59 6 0 3.646;
61 9 0 0.154; 62 9 0 1.304; 63 9 0 2.696; 64 9 0 3.646; 65 12 0 0.154;
66 12 0 1.304; 67 12 0 2.696; 68 12 0 3.646; 71 9 2.629 3.8; 72 3 0 2;
73 9 0 2;
MEMBER INCIDENCES
1 3 4; 2 1 3; 3 2 4; 4 5 9; 5 9 8; 6 8 7; 7 4 10; 8 10 12; 9 12 14; 11 4 11;
12 11 13; 13 13 15; 14 15 8; 15 10 11; 16 10 13; 17 13 14; 18 14 15; 19 12 13;
20 3 16; 21 16 9; 22 2 17; 23 4 18; 24 7 19; 25 8 20; 32 17 18; 33 20 19;
34 18 21; 35 21 23; 36 23 25; 37 25 20; 38 18 22; 39 22 24; 40 24 26; 41 26 20;
42 21 24; 43 24 25; 44 25 26; 45 23 24; 46 17 27; 47 18 28; 48 19 29; 56 27 28;
58 28 31; 59 31 33; 60 33 35; 62 28 32; 63 32 34; 64 34 36; 66 31 34; 67 34 35;
68 35 36; 69 33 34; 70 37 38; 71 39 40; 72 38 41; 73 41 40; 74 1 2; 75 5 7;
76 27 37; 77 29 39; 79 28 38; 85 4 17; 86 17 28; 87 28 37; 88 1 4; 98 1 47;
99 47 48; 100 48 49; 101 49 50; 103 2 52; 104 52 53; 105 53 72; 106 54 55;
108 17 56; 109 56 57; 110 57 58; 111 58 59; 113 27 61; 114 61 62; 115 62 73;
116 63 64; 118 37 65; 119 65 66; 120 66 67; 121 67 68; 139 21 22; 140 31 32;
147 12 23; 148 23 33; 149 41 34; 150 34 24; 151 24 13; 152 13 16; 163 50 5;
164 55 7; 165 59 19; 166 64 29; 167 68 39; 172 20 71; 173 71 40; 174 29 71;
175 19 8; 176 19 71; 177 71 39; 178 8 5; 179 14 8; 180 35 71; 181 36 71;
186 48 53; 187 53 57; 188 57 62; 189 62 66; 190 49 54; 191 54 58; 192 58 63;
193 63 67; 194 72 54; 195 5 72; 196 1 72; 197 72 17; 198 72 19; 199 73 63;
200 17 73; 201 19 73; 202 73 37; 203 73 39;
DEFINE MATERIAL START
ISOTROPIC STEEL
E 2.05e+008
POISSON 0.3
DENSITY 76.8195
ALPHA 1.2e-005
DAMP 0.03
END DEFINE MATERIAL
MEMBER PROPERTY INDIAN
15 TO 19 42 TO 45 66 TO 69 139 140 195 TO 198 200 TO 203 TABLE ST ISA75X75X8
MEMBER PROPERTY BRITISH
2 4 20 21 70 TO 73 98 TO 101 104 TO 106 108 TO 111 113 TO 116 118 TO 121 163 -
164 TO 167 194 199 TABLE ST UC152X152X23
MEMBER PROPERTY INDIAN
7 TO 9 11 TO 14 34 TO 41 58 TO 60 62 TO 64 147 TO 152 179 TO 180 -
181 TABLE SD ISA65X65X8
85 86 175 176 TABLE SD ISA90X90X8
3 6 32 33 56 174 TABLE SD ISA110X110X10
1 5 23 25 47 79 87 88 172 173 177 178 TABLE SD ISA130X130X10
22 24 46 48 74 TO 77 103 TABLE D ISMC200
186 TO 193 TABLE ST ISMC125
CONSTANTS
MATERIAL STEEL ALL
SUPPORTS
1 5 PINNED
37 39 ENFORCED BUT FX MX MY MZ
MEMBER TRUSS
15 TO 19 42 TO 45 66 TO 69 85 TO 88 139 140 175 TO 178 195 TO 198 200 TO 203
MEMBER RELEASE
3 6 32 33 56 174 END MY MZ
3 6 32 33 56 174 START MY MZ
1 5 7 11 23 25 34 38 47 58 62 74 75 79 104 109 114 147 TO 152 172 173 186 -
187 TO 193 START MY MZ
1 5 14 23 25 37 41 47 76 77 79 106 111 116 147 TO 152 172 173 179 TO 181 186 -
187 TO 193 END MY MZ
LOAD 1 LOADTYPE None TITLE DEAD LOAD
MEMBER LOAD
11 TO 14 38 TO 41 62 TO 64 181 UNI GY -0.945
20 21 72 73 UNI GY -0.4725
104 106 109 111 114 116 UNI GY -2.25
99 101 119 121 UNI GY -1.125
JOINT LOAD
52 TO 59 61 TO 64 FY -0.406134
47 50 65 68 FY -0.203067
53 54 57 58 62 63 FY -2.27288
48 49 66 67 FY -1.13644
LOAD 2 LOADTYPE None TITLE LIVE LOAD
MEMBER LOAD
11 TO 14 38 TO 41 62 TO 64 181 UNI GY -2.745
20 21 72 73 UNI GY -1.3725
104 106 109 111 114 116 UNI GY -15.75
99 101 119 121 UNI GY -7.875
JOINT LOAD
53 54 57 58 62 63 FY -2.45152
48 49 66 67 FY -1.22576
LOAD 3 LOADTYPE None TITLE WIND LOAD SUCTION +Z
MEMBER LOAD
3 32 56 UNI GZ 8.604
6 33 174 UNI GZ -1.7925
2 70 UNI GZ 4.302
4 71 UNI GZ -0.89625
LOAD 4 LOADTYPE None TITLE WIND LOAD PRESSURE +Z
MEMBER LOAD
3 32 56 UNI GZ 1.434
2 70 UNI GZ 0.717
6 33 UNI GZ 5.3775
4 71 UNI GZ 2.68875
LOAD 5 LOADTYPE None TITLE WIND LOAD SUCTION +X
MEMBER LOAD
11 12 38 39 62 63 UNI GY 2.2944
13 14 40 41 64 181 UNI GY 0.717
20 72 UNI GY 1.1472
21 73 UNI GY 0.3585
LOAD 6 LOADTYPE None TITLE WIND LOAD-PRESSURE +X
MEMBER LOAD
11 12 38 39 62 63 UNI GY 9.4644
13 14 40 41 64 181 UNI GY 7.887
20 72 UNI GY 4.7322
21 73 UNI GY 3.9435
LOAD COMB 7 1(DL+LL+CL)
1 1.0 2 1.0
LOAD COMB 8 1DL+1WL+Z(PRE)
1 1.0 3 1.0
LOAD COMB 9 1DL+1WL+Z(SUC)
1 1.0 3 1.0
LOAD COMB 10 1DL+1WL+X(PRE)
1 1.0 6 1.0
LOAD COMB 11 1DL+1WL+X(SUC)
1 1.0 5 1.0
LOAD COMB 12 1DL+1LL+CL+1WL+Z(PRE)
1 1.0 2 1.0 4 1.0
LOAD COMB 13 1DL+1LL+CL+1WL+Z(SUC)
1 1.0 2 1.0 3 1.0
LOAD COMB 14 1DL+1LL+CL+1WL+X(PRE)
1 1.0 2 1.0 6 1.0
LOAD COMB 15 1DL+1LL+CL+1WL+X(SUC)
1 1.0 2 1.0 5 1.0
LOAD COMB 16 1(DL+LL+CL)
1 1.0 2 1.0
LOAD COMB 17 0.75DL+0.75LL+0.75CL+0.75WL+Z(PRE)
1 0.75 2 0.75 4 0.75
LOAD COMB 18 0.75DL+0.75LL+0.75CL+0.75WL+Z(SUC)
1 0.75 2 0.75 3 0.75
LOAD COMB 19 0.75DL+0.75LL+0.75CL+0.75WL+X(PRE)
1 0.75 2 0.75 6 0.75
LOAD COMB 20 0.75DL+0.75LL+0.75CL+0.75WL+X(SUC)
1 1.0 2 1.0 5 1.0
PERFORM ANALYSIS PRINT ALL
PARAMETER 1
CODE IS800 LSD
STEEL MEMBER TAKE OFF LIST 1 TO 9 11 TO 25 32 TO 48 56 58 TO 60 62 TO 64 66 -
67 TO 77 79 85 TO 88 98 TO 101 103 TO 106 108 TO 111 113 TO 116 118 TO 121 -
139 140 147 TO 152 163 TO 167 172 TO 181 194 199
PARAMETER 2
CODE IS800 LSD
CHECK CODE MEMB 1 TO 9 11 TO 25 32 TO 48 56 58 TO 60 62 TO 64 66 TO 77 79 -
85 TO 88 98 TO 101 103 TO 106 108 TO 111 113 TO 116 118 TO 121 139 140 147 -
148 TO 152 163 TO 167 172 TO 181 194 199
PARAMETER 3
CODE IS800 LSD
STEEL TAKE OFF LIST 1 TO 9 11 TO 25 32 TO 48 56 58 TO 60 62 TO 64 66 TO 77 -
79 85 TO 88 98 TO 101 103 TO 106 108 TO 111 113 TO 116 118 TO 121 139 140 -
147 TO 152 163 TO 167 172 TO 181 194 199
FINISH

  • 0 Offline

    Dear Vasanth,

    I can see in your model that the loads in FZ can't find its way to the supports. You can check the same in Post-Processing > Reaction > Static Check. The Static check is not passed for load case 3 and 4 which are imposing load on the structure in FZ direction. Instability warnings are reported for the same direction. Generally they are reported whenever the load can't flow to the supports. You can find more about it in the following posts.

    communities.bentley.com/.../29018.do-instability-messages-mean-my-analysis-results-are-unsatisfactory

    communities.bentley.com/.../2046.staad-pro-instability-and-zero-stiffness-faq

    Answer Verified By: Vasanthakumar 

  • 0 Offline in reply to Kaushal Aggarwal
    Dear Kaushal Aggarwal sir,


    The following staad model also has same problem.How can i solve this?

    Please help me sir.


    STAAD SPACE
    START JOB INFORMATION
    ENGINEER DATE 16-Jun-16
    END JOB INFORMATION
    INPUT WIDTH 79
    UNIT METER KN
    JOINT COORDINATES
    9 0 6.975 -0.845; 10 10.92 6.975 -0.845; 11 0.6 6.975 11; 43 0.824 6.975 11;
    44 1.654 6.975 11; 45 2.884 6.975 11; 46 4.114 6.975 11; 47 5.344 6.975 11;
    48 6.574 6.975 11; 49 7.804 6.975 11; 50 9.034 6.975 11; 51 10.254 6.975 11;
    62 12.95 7.475 8.395; 63 14.25 7.475 8.395; 64 15.6 7.475 8.395;
    65 16.011 7.475 8.395; 66 0 6.975 8.395; 67 10.92 6.975 8.395;
    68 0.824 6.975 8.395; 69 1.654 6.975 8.395; 70 2.884 6.975 8.395;
    71 4.114 6.975 8.395; 72 5.344 6.975 8.395; 73 6.574 6.975 8.395;
    74 7.804 6.975 8.395; 75 9.034 6.975 8.395; 76 10.254 6.975 8.395;
    77 0 6.975 10.395; 78 10.92 6.975 10.395; 79 -0.5 6.975 8.395;
    81 11.654 7.475 10.703; 82 12.954 7.475 10.703; 83 14.254 7.475 10.703;
    84 15.604 7.475 10.703; 85 16.014 7.475 10.703; 86 -0.5 6.975 10.395;
    88 10.229 6.975 11; 89 11.679 7.475 10.703; 90 11.675 7.475 8.395;
    MEMBER INCIDENCES
    35 66 68; 36 11 43; 37 43 44; 38 44 45; 39 45 46; 40 46 47; 41 47 48; 42 48 49;
    43 49 50; 44 50 88; 46 68 69; 48 69 70; 50 70 71; 52 71 72; 54 72 73; 56 73 74;
    58 74 75; 60 75 76; 62 76 67; 64 67 90; 66 62 63; 67 63 64; 68 64 65; 69 66 9;
    70 67 10; 71 66 77; 72 67 78; 73 66 79; 74 68 43; 75 69 44; 76 70 45; 77 71 46;
    78 72 47; 79 73 48; 80 74 49; 81 75 50; 82 76 88; 85 81 89; 86 82 83; 87 83 84;
    88 84 85; 89 90 89; 90 62 82; 91 63 83; 92 64 84; 93 79 86; 106 88 51;
    107 89 82; 108 90 62; 109 79 77; 110 77 68; 111 68 44; 112 44 71; 113 71 48;
    114 48 75; 115 75 78;
    DEFINE MATERIAL START
    ISOTROPIC STEEL
    E 2.05e+008
    POISSON 0.3
    DENSITY 76.8195
    ALPHA 1.2e-005
    DAMP 0.03
    ISOTROPIC CONCRETE
    E 2.17185e+007
    POISSON 0.17
    DENSITY 23.5616
    ALPHA 1e-005
    DAMP 0.05
    END DEFINE MATERIAL
    MEMBER PROPERTY INDIAN
    69 TO 72 TABLE TB ISMB500 WP 0.25 TH 0.016
    35 TO 44 46 48 50 52 54 56 58 60 62 106 TABLE ST ISMB500
    76 TO 78 80 TO 82 90 TO 93 TABLE ST ISMC125
    73 TO 75 79 89 TABLE ST ISMC200
    64 66 TO 68 85 TO 88 107 108 TABLE ST ISMB200
    109 TO 115 TABLE ST ISA65X65X6
    CONSTANTS
    MATERIAL STEEL ALL
    SUPPORTS
    9 TO 11 51 77 78 81 PINNED
    65 85 86 FIXED BUT FX FZ MX MY MZ
    *1 TO 4 13 TO 16 PINNED
    MEMBER RELEASE
    74 TO 82 89 TO 93 START MY MZ
    74 TO 82 89 TO 92 END MY MZ
    64 START MZ
    62 END MZ
    MEMBER TRUSS
    109 TO 115
    LOAD 1 LOADTYPE Dead TITLE DEAD LOAD
    SELFWEIGHT Y -1 LIST 35 TO 44 46 48 50 52 54 56 58 60 62 64 66 TO 82 -
    85 TO 93 106 TO 108
    MEMBER LOAD
    71 72 74 TO 82 89 TO 93 UNI GY -0.42
    75 79 89 CON GY -3.63
    74 CON GY -2.74
    LOAD 2 LOADTYPE Live TITLE LIVE LOAD
    MEMBER LOAD
    71 72 74 TO 82 89 TO 93 UNI GY -3.4
    71 72 74 TO 82 89 TO 93 UNI GY -1.36
    75 79 89 CON GY -4.72
    74 CON GY -3.57
    LOAD COMB 101 1.0(DL+LL)
    1 1.0 2 1.0
    LOAD COMB 201 1.5(DL+LL)
    1 1.5 2 1.5
    PERFORM ANALYSIS PRINT ALL
    ****************************************************
    LOAD LIST 201
    PARAMETER 1
    CODE IS800 LSD
    BEAM 1 MEMB 35 TO 44 46 48 50 52 54 56 58 60 62 64 66 TO 82 85 TO 93 106 TO 108
    MAIN 250 MEMB 35 TO 44 46 48 50 52 54 56 58 60 62 64 66 TO 82 85 TO 93 106 -
    107 TO 108
    FU 410000 MEMB 35 TO 44 46 48 50 52 54 56 58 60 62 64 66 TO 82 85 TO 93 106 -
    107 TO 108
    FYLD 250000 MEMB 35 TO 44 46 48 50 52 54 56 58 60 62 64 66 TO 82 85 TO 93 -
    106 TO 108
    LZ 11.24 MEMB 35 TO 44 46 48 50 52 54 56 58 60 62 64 66 TO 73 85 TO 88
    TRACK 1 MEMB 35 TO 44 46 48 50 52 54 56 58 60 62 64 66 TO 82 85 TO 93 106 -
    107 TO 108
    CHECK CODE MEMB 35 TO 44 46 48 50 52 54 56 58 60 62 64 66 TO 82 85 TO 93 106 -
    107 TO 108
    STEEL TAKE OFF LIST 35 TO 44 46 48 50 52 54 56 58 60 62 64 66 TO 82 -
    85 TO 93 106 TO 108
    ********************************************
    ********FOR DEFLECTION
    *LOAD LIST 101
    *PARAMETER 2
    *CODE IS800 LSD
    *DFF 325 MEMB 35 TO 44 46 48 50 52 54 56 58 60 62 64 TO 73 85 TO 88 105 TO 108
    *DJ1 11 MEMB 36 TO 44 106
    *DJ2 51 MEMB 36 TO 44 106
    *DJ1 79 MEMB 35 46 48 50 52 54 56 58 60 62 64 TO 68 73 105 108
    *DJ2 65 MEMB 35 46 48 50 52 54 56 58 60 62 64 TO 68 73 105 108
    *DJ1 81 MEMB 85 TO 88 107
    *DJ2 85 MEMB 85 TO 88 107
    *DJ1 77 MEMB 69 71
    *DJ2 9 MEMB 69 71
    *DJ1 78 MEMB 70 72
    *DJ2 10 MEMB 70 72
    *CHECK CODE ALL
    FINISH
  • 0 Offline in reply to Vasanthakumar

    Dear Vasanth,

    You can deal with those warnings after ensuring that your static check is passed successfully.  In the above model, the static check is passed so a weak spring can be added in the same direction in which the instability warning reported. The modified structure is attached for your reference. Two pair of duplicate node also found in your model. I suggest you to check the attached file carefully.

    be 16.06.16. 2.std

  • 0 Offline in reply to Kaushal Aggarwal
    Thank you very much sir but how you given that support kindly tell the technical reason or concept to understand so that if any problem comes in future means i will solve independently.

    One more help i need to understand or solve the instability and zero stiffness problems independently.How can i learn please help me sir?
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