Dff results or Deflection Check Results

Hi, can someone give some guidance to a new STAAD user as to how to do a proper deflection check for beams for a structure?

Ive tried to use the DFF command for a STAAD model im working on now but am unable to see any tangible results. After reading the forum posts I could find, it seems that DFF can only be checked by actually going through the STAAD PRO output file manually and will not be displayed in the post processing results, am I correct?

My problem is that I do not know what I am looking for. (As in what a DFF failure would look like) I am unable to find any indication in the post processing tab of any failure in my model. My model passes for design.

However I know that my model would fail a DFF check as using the post processing page, I have observed that there is a beam in the model with a dff of 114.4. The DFF value for the analysis is set to 360.

I calculated the dff manually by using,  span length = 1258.5 & resultant beam deflection = 11. dff =1258.5/11=114.4

Can someone please advise me if my understanding if correct? And if so, how to check dff results for an analysis.

Thanks

Dave

Parents
  • DFF command is available only for steel design. Please let me know as to whether  you have put in DFF command in the file and also put in the value and assigned the same to the member for which you are looking for the DFF result. If the command is not assigned to the member for which the DFF is working out to 114.4, the Staad will not take cognizance of the input DFF for the member. . Please also check whether there is any node between the support of the beam in question. . Please check and post.

  • The steel design output can also be viewed in a report. After the analysis, choose File-Report Setup. In the drop down list for Available, choose Output. Select Steel Design Detail followed by OK. Go back to the File menu and choose Print Preview Report. The deflection check results will be part of the design output. The value calculated as L/d is reported using lowercase "dff". Attached is the screen grab of a sample.

  • Hi all! Thanks for the advice! Well Im finally able to see the dff results but it seems my dff results are all 0. I am not sure what but I am guessing that it is because ive done a deflection check on beams that are not in between supports am I correct?

    If that is incorrect, please correct me and also advise me how I may perform a deflection check for a model of this kind.

    STAAD output follows in trailing posts

Reply
  • Hi all! Thanks for the advice! Well Im finally able to see the dff results but it seems my dff results are all 0. I am not sure what but I am guessing that it is because ive done a deflection check on beams that are not in between supports am I correct?

    If that is incorrect, please correct me and also advise me how I may perform a deflection check for a model of this kind.

    STAAD output follows in trailing posts

Children
  • STAAD SPACE

    START JOB INFORMATION

    JOB COMMENT Geometry- NA

    JOB COMMENT Specifications-NA

    JOB COMMENT Joint Modeling-NA

    JOB COMMENT Supports-OK

    END JOB INFORMATION

    INPUT WIDTH 79

    UNIT MMS NEWTON

    JOINT COORDINATES

    1 0 0 0; 2 7832 0 0; 3 3916 0 0; 4 0 0 2830; 5 7832 0 2830; 6 3916 0 2830;

    7 0 2734.5 0; 8 7832 2734.5 0; 9 3916 2734.5 0; 10 0 2734.5 2830;

    11 7832 2734.5 2830; 12 3916 2734.5 2830; 13 0 2343 0; 14 7832 2343 0;

    15 0 2343 2830; 16 7832 2343 2830; 17 -1637 2343 0; 18 -1637 2343 2830;

    19 9469 2343 0; 20 9469 2343 2830; 21 -804 2343 0; 22 -804 2343 2830;

    23 8636 2343 0; 24 8636 2343 2830; 25 -1637 2343 1880; 26 9469 2343 1880;

    27 -804 2343 1880; 28 8636 2343 1880; 29 -1637 2343 950; 30 9469 2343 950;

    31 -804 2343 950; 32 8636 2343 950; 33 -1330 2343 0; 34 -1330 2343 2830;

    35 9162 2343 0; 36 9162 2343 2830; 37 0 1013 0; 38 7832 1013 0; 39 0 1013 2830;

    40 7832 1013 2830; 41 0 493 2830; 42 7832 493 2830; 45 -1485 493 2830;

    46 9317 493 2830; 47 2183.5 2734.5 0; 48 5648.5 2734.5 0;

    49 5648.5 2734.5 2830; 50 2183.5 2734.5 2830; 51 1408.5 2734.5 0;

    52 6423.5 2734.5 0; 53 6423.5 2734.5 2830; 54 1408.5 2734.5 2830;

    55 2183.5 1956 0; 56 5648.5 1956 0; 57 5648.5 1956 2830; 58 2183.5 1956 2830;

    59 1408.5 1956 0; 60 6423.5 1956 0; 61 6423.5 1956 2830; 62 1408.5 1956 2830;

    63 1408.5 1956 1415; 64 2183.5 1956 1415; 65 5648.5 1956 1415;

    66 6423.5 1956 1415; 67 1408.5 1956 156.5; 68 2183.5 1956 156.5;

    69 5648.5 1956 156.5; 70 6423.5 1956 156.5; 71 1408.5 1956 2673.5;

    72 2183.5 1956 2673.5; 73 5648.5 1956 2673.5; 74 6423.5 1956 2673.5;

    75 0 2734.5 1415; 76 7832 2734.5 1415; 77 1050 2734.5 0; 78 6782 2734.5 0;

    79 6782 2734.5 2830; 80 1050 2734.5 2830; 81 2866 2734.5 0; 82 4966 2734.5 0;

    83 4966 2734.5 2830; 84 2866 2734.5 2830; 85 0 450 0; 86 7832 450 0;

    87 3916 450 0; 88 3916 450 2830; 89 0 450 2830; 90 7832 450 2830;

    91 0 2964.5 0; 92 7832 2964.5 0; 93 3916 2964.5 0; 94 0 2964.5 2830;

    95 7832 2964.5 2830; 96 3916 2964.5 2830;

    MEMBER INCIDENCES

    1 1 85; 2 2 86; 3 3 87; 4 4 89; 5 5 90; 6 6 88; 7 7 77; 8 8 78; 9 11 79;

    10 10 80; 11 7 75; 12 8 76; 13 9 12; 14 13 7; 15 14 8; 16 15 10; 17 16 11;

    18 13 21; 19 15 22; 22 17 29; 23 19 30; 24 21 33; 25 22 34; 26 23 35; 27 24 36;

    28 21 31; 29 23 32; 30 25 18; 31 26 20; 32 27 22; 33 28 24; 34 29 25; 35 30 26;

    36 31 27; 37 32 28; 38 31 29; 39 27 25; 40 32 30; 41 28 26; 42 33 17; 43 34 18;

    44 35 19; 45 36 20; 46 37 13; 47 38 14; 48 39 15; 49 40 16; 50 39 34; 51 37 33;

    52 40 36; 53 38 35; 54 41 39; 55 42 40; 60 41 45; 61 42 46; 62 47 81; 63 48 82;

    64 49 83; 65 50 84; 66 51 47; 67 52 48; 68 53 49; 69 54 50; 70 47 55; 71 48 56;

    72 49 57; 73 50 58; 74 51 59; 75 52 60; 76 53 61; 77 54 62; 78 59 67; 79 55 68;

    80 56 69; 81 60 70; 82 63 71; 83 64 72; 86 63 64; 87 65 66; 88 67 63; 89 68 64;

    90 69 65; 91 70 66; 92 71 62; 93 72 58; 94 73 57; 95 74 61; 96 67 68; 97 71 72;

    98 69 70; 99 73 74; 102 85 75; 103 89 75; 104 86 76; 105 90 76; 106 77 51;

    107 78 52; 108 79 53; 109 80 54; 110 81 9; 111 82 9; 112 83 12; 113 84 12;

    114 80 89; 115 84 88; 116 83 88; 117 81 87; 118 82 87; 119 77 85; 120 79 90;

    121 78 86; 122 16 24; 123 14 23; 124 11 76; 125 10 75; 126 85 37; 127 86 38;

    128 87 9; 129 88 12; 130 89 41; 131 90 42; 132 7 91; 133 8 92; 134 9 93;

    135 10 94; 136 11 95; 137 12 96; 138 73 65; 139 74 66;

    START GROUP DEFINITION

    MEMBER

    FLOOR

    _FIXD_PLAT 22 24 25 28 30 32 34 36 38 39 42 43

    _FLOT_PLAT 23 26 27 29 31 33 35 37 40 41 44 45

    END GROUP DEFINITION

    START USER TABLE

    TABLE 1

    UNIT MMS NEWTON

    CHANNEL

    PLENUM

    3588 460 6 75 6 9.13365e+007 1.23246e+006 43056 11.6538 2760 600

    MOTFRAME

    2628 300 6 75 6 3.13947e+007 1.13143e+006 31536 14.8151 1800 600

    PLENUMT

    4752 460 8 75 8 1.1965e+008 1.58807e+006 101376 12.4596 3680 800

    TABLE 2

    UNIT MMS NEWTON

    WIDE FLANGE

    MIDBEAM

    4488 460 6 150 6 1.37715e+008 3.38306e+006 53856 2760 1200

    END

    DEFINE MATERIAL START

    ISOTROPIC STEEL

    E 205000

    POISSON 0.3

    DENSITY 7.68195e-005

    ALPHA 1.2e-005

    DAMP 0.03

    END DEFINE MATERIAL

    MEMBER PROPERTY CHINESE

    18 19 22 TO 45 60 61 122 123 TABLE ST CH16B

    MEMBER PROPERTY JAPANESE

    50 TO 53 70 TO 77 102 TO 105 114 TO 121 TABLE ST L75X75X9

    MEMBER PROPERTY CHINESE

    1 TO 6 14 TO 17 46 TO 49 54 55 126 TO 137 TABLE ST HW150X150

    MEMBER PROPERTY CHINESE

    78 TO 83 86 TO 99 138 139 UPTABLE 1 MOTFRAME

    13 UPTABLE 2 MIDBEAM

    MEMBER PROPERTY CHINESE

    7 TO 12 62 TO 69 106 TO 113 124 125 UPTABLE 1 PLENUMT

    CONSTANTS

    BETA 180 MEMB 7 9 12 18 22 24 27 29 30 33 34 37 38 41 42 45 61 62 64 66 68 -

    79 81 83 89 91 93 95 96 98 106 108 110 112 122 125 138

    BETA 315 MEMB 50 53 73 76 103 104 114 116 117 121

    BETA 45 MEMB 51 52 70 75 102 105 115 118 TO 120

    BETA 90 MEMB 1 TO 6 14 TO 17 46 TO 49 54 55 86 87 126 TO 137

    BETA 135 MEMB 71 74

    BETA 225 MEMB 72 77

    MATERIAL STEEL MEMB 1 TO 19 22 TO 55 60 TO 83 86 TO 99 102 TO 139

    MEMBER OFFSET

    18 19 50 51 60 START -75 0 0

    52 53 61 122 123 START 75 0 0

    70 TO 77 114 TO 121 START 0 -230 0

    50 TO 53 END 0 -80 0

    114 116 118 119 END 75 0 0

    115 117 120 121 END -75 0 0

    103 105 END 0 -230 150

    102 104 END 0 -230 -150

    102 104 START 0 0 75

    103 105 START 0 0 -75

    70 TO 77 END 0 -150 0

    79 81 83 89 91 93 95 139 START 50 0 0

    79 81 83 89 91 93 95 139 END 50 0 0

    78 80 82 88 90 92 94 138 START -50 0 0

    78 80 82 88 90 92 94 138 END -50 0 0

    86 87 96 TO 99 START -37.5 0 0

    86 87 96 TO 99 END 37.5 0 0

  • SUPPORTS

    1 TO 6 FIXED

    MEMBER TRUSS

    50 TO 53 102 TO 105 114 TO 121

    DEFINE WIND LOAD

    TYPE 1

    INT 0.00128452 0.00128452 0.00128983 0.00129505 0.00130016 0.00130518 -

    0.00131011 0.00131496 0.00131972 0.0013244 0.001329 0.00133353 0.00133799 -

    0.00134238 0.0013467 HEIG  0  4572  4681.85  4791.69  4901.54  5011.38 -

    5121.23  5231.08  5340.92  5450.77  5560.62  5670.46  5780.31  5890.15  6000

    EXP 1 JOINT 1 TO 42 45 TO 96

    TYPE 2

    INT 0.00119521 0.00119521 0.00120016 0.00120501 0.00120977 0.00121444 -

    0.00121903 0.00122354 0.00122797 0.00123232 0.00123661 0.00124082 0.00124497 -

    0.00124905 0.00125307 HEIG  0  4572  4681.85  4791.69  4901.54  5011.38 -

    5121.23  5231.08  5340.92  5450.77  5560.62  5670.46  5780.31  5890.15  6000

    EXP 1 JOINT 1 TO 42 45 TO 96

    LOAD 1 LOADTYPE None  TITLE SELFWEIGHT

    SELFWEIGHT Y -1

    LOAD 2 LOADTYPE None  TITLE LOAD 1

    MEMBER LOAD

    7 TO 10 62 TO 69 106 TO 113 UNI GY -4.14

    LOAD 3 LOADTYPE None  TITLE LOAD 2

    JOINT LOAD

    91 94 FY -15880

    LOAD 4 LOADTYPE None  TITLE LOAD 3

    MEMBER LOAD

    7 TO 10 62 TO 69 106 TO 113 UNI GY -0.47

    JOINT LOAD

    91 92 94 95 FY -637.65

    LOAD 5 LOADTYPE None  TITLE LOAD 5

    FLOOR LOAD

    _FIXD_PLAT FLOAD -0.005 GY

    _FLOT_PLAT FLOAD -0.005 GY

    LOAD 6 LOADTYPE None  TITLE LOAD 6

    MEMBER LOAD

    86 87 CON GY -770 425

    LOAD 7 LOADTYPE None  TITLE LOAD 7

    MEMBER LOAD

    86 87 CON GY -1300 425

    LOAD 8 LOADTYPE None  TITLE LOAD 8

    MEMBER LOAD

    86 87 CON GY -490.5 425

    LOAD 9 LOADTYPE None  TITLE LOAD 9

    MEMBER LOAD

    88 89 138 139 CON GY -2207.5 560

    LOAD 10 LOADTYPE None  TITLE LOAD 10

    MEMBER LOAD

    86 CON GZ -2061 425

    87 CON GZ 2061 425

    LOAD 11 LOADTYPE None  TITLE LOAD 11

    MEMBER LOAD

    7 TO 10 62 TO 69 106 TO 113 UNI GY -0.828

    86 87 CON GY -154 425

    86 87 CON GY -260 425

    86 87 CON GY -98.1 425

    88 89 138 139 CON GY -442 560

    86 CON GZ -415 425

    87 CON GZ 415 425

    LOAD 12 LOADTYPE None  TITLE LOAD 12

    MEMBER LOAD

    7 TO 10 62 TO 69 106 TO 113 UNI GY -0.828

    86 87 CON GY -154 425

    86 87 CON GY -98.1 425

    88 89 138 139 CON GY -442 560

    LOAD 13 LOADTYPE None  TITLE LOAD 13

    MEMBER LOAD

    7 TO 10 62 TO 69 106 TO 113 UNI GX 0.828

    86 87 CON GX 154 425

    86 87 CON GX 98.1 425

    88 89 138 139 CON GX 442 560

    LOAD 14 LOADTYPE None  TITLE LOAD 14

    MEMBER LOAD

    7 TO 10 62 TO 69 106 TO 113 UNI GZ 0.828

    86 87 CON GZ 154 425

    86 87 CON GZ 98.1 425

    88 89 138 139 CON GZ 442 560

    LOAD 15 LOADTYPE None  TITLE LOAD 15

    WIND LOAD X 1 TYPE 1 XR -2000 0 YR 0 6000 ZR 0 4000 OPEN

    LOAD 16 LOADTYPE None  TITLE LOAD 16

    WIND LOAD Z 1 TYPE 2 XR -2000 10000 YR 0 6000 ZR -50 100 OPEN

    LOAD COMB 18 LOAD 17

    1 1.0 2 1.0 3 1.0 5 1.0 6 1.0 7 1.0 8 1.0 9 1.0 10 1.0 11 1.0 15 1.0 -

    16 1.0

    LOAD COMB 19 LOAD 18

    1 1.0 2 1.0 3 1.0 4 1.0 5 1.0 15 1.0 16 1.0 6 1.0 8 1.0 9 1.0 10 1.0

    LOAD COMB 20 LOAD 19

    1 1.0 2 1.0 6 1.0 5 1.0 8 1.0 9 1.0 10 1.0 12 1.0 13 1.0 14 1.0 15 1.0 -

    16 1.0 3 1.0

    PERFORM ANALYSIS

    CHECK CODE ALL

    PARAMETER

    CODE AISC

    DFF 360 MEMB 1 TO 19 22 TO 49 54 55 60 TO 83 86 TO 99 106 TO 113 122 TO 139

    DJ1 60 MEMB 81 91 95 139

    DJ2 61 MEMB 81 91 95 139

    DJ1 56 MEMB 80 90 94 138

    DJ2 57 MEMB 80 90 94 138

    DJ1 55 MEMB 79 83 89 93

    DJ2 58 MEMB 79 83 89 93

    DJ1 59 MEMB 78 82 88 92

    DJ1 62 MEMB 78 82 88 92

    DJ1 7 MEMB 11 125

    DJ2 10 MEMB 11 125

    DJ1 8 MEMB 12 124

    DJ2 11 MEMB 12 124

    DJ1 10 MEMB 10 65 69 109 113

    DJ2 12 MEMB 10 65 69 109 113

    DJ1 11 MEMB 9 64 68 108 112

    DJ2 12 MEMB 9 64 68 108 112

    DJ1 7 MEMB 7 62 66 106 110

    DJ2 9 MEMB 7 62 66 106 110

    DJ1 8 MEMB 8 63 67 107 111

    DJ2 9 MEMB 8 63 67 107 111

    DJ1 21 MEMB 28 32 36

    DJ2 22 MEMB 28 32 36

    DJ1 17 MEMB 22 30 34

    DJ2 18 MEMB 22 30 34

    DJ1 23 MEMB 29 33 37

    DJ2 24 MEMB 29 33 37

    DJ1 19 MEMB 23 31 35

    DJ2 20 MEMB 23 31 35

    DJ1 19 MEMB 26 44 123

    DJ2 14 MEMB 26 44 123

    DJ1 16 MEMB 27 45 122

    DJ2 20 MEMB 27 45 122

    DJ1 15 MEMB 19 25 43

    DJ2 18 MEMB 19 25 43

    DJ1 13 MEMB 18 24 42

    DJ2 17 MEMB 18 24 42

    CAN 1 MEMB 60 61

    FINISH

  • The problem lies in the sequence of your input. You currently have

    PERFORM ANALYSIS

    CHECK CODE ALL

    PARAMETER

    CODE AISC

    DFF 360 MEMB 1 TO 19 22 TO 49 54 55 60 TO 83 86 TO 99 106 TO 113 122 TO 139

    Since the CHECK CODE command is ahead of the parameters like DFF, those parameters are not being used in the code checking. Instead, the default values of those parameters are used. The default value of DFF is 0, which indicates no deflection check.

    You need to place the CHECK CODE command after the line

    CAN 1 MEMB 60 61

  • Check the output file. There are numerous messages stating that the deflection check cannot be performed on members which have been assigned offsets.

    Usually, **** indicates that the value is so large that it does not fit within the space allotted for writing it. Nan indicates "Not a number" which usually occurs when the deflection is zero. Looks like that message is appearing for member 92. That happens to be one of the members for which an offset is provided.

    Deflection check can be performed for an member as long as there it undergoes a lateral deflection (a non-zero deflection perpendicular to its X axis). If there is no lateral deflection, then, L/d term ("dff") will turn out to be very large or Nan because the "d" is very small or zero.

  • Hello All,

    I have a similar problem.

    My structure members are split in smaller elements, but i have specified JD1 and JD2 for every member. But still when I get the results from the File-Reports it gives me design results for all the small elements. How can i get the results for the members i have specified using jd1 and jd2? I am chasing mainly the results for the deflection check.