Group Loads / Link text / Rayleigh Calc a load case?

I need to perform some rayleigh frequency analysis on several load cases of a foundation I am working on. 

Is there a way to either link text, group loads (other than the obvious load combinations), or run a rayleigh frequency analysis on a load combination rather than a load?

I would like to only enter a load once and not track it down in several places in the input file if it changes down the road (likely). 

My current understanding of the way rayleigh frequency is calculated is to run the code in its own set of primary loads .This is in order to run it with several different primary loads at the same time -- because I have not determined how to run the Rayleigh frequency code on a load case. 

Any help is appreciated.

  • In the input file below, Load Case 1 calculates the Rayleigh frequency of the structure subject to selfweight and plate pressure loads in the X direction.  Then I created Load Case 3 which contains only the laterally directed selfweight, and Load Case 4 which contains only the laterally directed plate pressures.  In Load Case 5 I created a Repeat Load that considers Load Case 3 with a factor of 1 concurrently with Load Case 4 with a factor of 1, and then I issued the CALCULATE RAYLEIGH FREQUENCY command within Load Case 5.  If you run the model and look at the output file, you'll see that the Rayleigh frequency calculated for Load Case 1 is identical to the frequency calculated for the Repeat Load Case 5.  I hope that helps, but if not, shoot back and we'll dig into it further.

    Cheers,

    Chris

     

    STAAD SPACE
    START JOB INFORMATION
    ENGINEER DATE Today
    END JOB INFORMATION
    UNIT FEET KIP
    JOINT COORDINATES
    1 0 0 0; 2 0 0 20; 3 20 0 0; 4 20 0 20; 5 40 0 0; 6 40 0 20; 7 0 15 0;
    8 0 15 5; 9 0 15 10; 10 0 15 15; 11 0 15 20; 12 5 15 0; 13 10 15 0;
    14 15 15 0; 15 5 15 20; 16 10 15 20; 17 15 15 20; 18 20 15 0;
    19 20 15 5; 20 20 15 10; 21 20 15 15; 22 20 15 20; 23 25 15 0;
    24 30 15 0; 25 35 15 0; 26 25 15 20; 27 30 15 20; 28 35 15 20;
    29 40 15 0; 30 40 15 5; 31 40 15 10; 32 40 15 15; 33 40 15 20;
    34 20 3.75 0; 35 20 7.5 0; 36 20 11.25 0; 37 20 3.75 20; 38 20 7.5 20;
    39 20 11.25 20; 40 5 15 5; 41 5 15 10; 42 5 15 15; 43 10 15 5;
    44 10 15 10; 45 10 15 15; 46 15 15 5; 47 15 15 10; 48 15 15 15;
    49 25 15 5; 50 25 15 10; 51 25 15 15; 52 30 15 5; 53 30 15 10;
    54 30 15 15; 55 35 15 5; 56 35 15 10; 57 35 15 15; 58 20 11.25 5;
    59 20 11.25 10; 60 20 11.25 15; 61 20 7.5 5; 62 20 7.5 10; 63 20 7.5 15;
    64 20 3.75 5; 65 20 3.75 10; 66 20 3.75 15; 67 20 0 5; 68 20 0 10;
    69 20 0 15;
    MEMBER INCIDENCES
    1 1 7; 2 2 11; 3 3 34; 4 34 35; 5 35 36; 6 36 18; 7 4 37; 8 37 38;
    9 38 39; 10 39 22; 11 5 29; 12 6 33; 13 7 8; 14 8 9; 15 9 10; 16 10 11;
    17 18 19; 18 19 20; 19 20 21; 20 21 22; 21 29 30; 22 30 31; 23 31 32;
    24 32 33; 25 7 12; 26 12 13; 27 13 14; 28 14 18; 29 18 23; 30 23 24;
    31 24 25; 32 25 29; 33 11 15; 34 15 16; 35 16 17; 36 17 22; 37 22 26;
    38 26 27; 39 27 28; 40 28 33;
    ELEMENT INCIDENCES SHELL
    41 7 8 40 12; 42 8 9 41 40; 43 9 10 42 41; 44 10 11 15 42;
    45 12 40 43 13; 46 40 41 44 43; 47 41 42 45 44; 48 42 15 16 45;
    49 13 43 46 14; 50 43 44 47 46; 51 44 45 48 47; 52 45 16 17 48;
    53 14 46 19 18; 54 46 47 20 19; 55 47 48 21 20; 56 48 17 22 21;
    57 18 19 49 23; 58 19 20 50 49; 59 20 21 51 50; 60 21 22 26 51;
    61 23 49 52 24; 62 49 50 53 52; 63 50 51 54 53; 64 51 26 27 54;
    65 24 52 55 25; 66 52 53 56 55; 67 53 54 57 56; 68 54 27 28 57;
    69 25 55 30 29; 70 55 56 31 30; 71 56 57 32 31; 72 57 28 33 32;
    73 18 19 58 36; 74 19 20 59 58; 75 20 21 60 59; 76 21 22 39 60;
    77 36 58 61 35; 78 58 59 62 61; 79 59 60 63 62; 80 60 39 38 63;
    81 35 61 64 34; 82 61 62 65 64; 83 62 63 66 65; 84 63 38 37 66;
    85 34 64 67 3; 86 64 65 68 67; 87 65 66 69 68; 88 66 37 4 69;
    MEMBER PROPERTY AMERICAN
    1 TO 40 PRIS YD 1 ZD 1
    ELEMENT PROPERTY
    41 TO 88 THICKNESS 0.5
    UNIT FEET POUND
    DEFINE MATERIAL START
    ISOTROPIC CONCRETE
    E 4.536e+008
    POISSON 0.17
    DENSITY 149.99
    ALPHA 5.5e-006
    DAMP 0.05
    END DEFINE MATERIAL
    CONSTANTS
    MATERIAL CONCRETE ALL
    SUPPORTS
    1 TO 6 FIXED
    LOAD 1 LOADTYPE None TITLE LOAD CASE 1
    SELFWEIGHT X 1
    ELEMENT LOAD
    41 TO 88 PR GX 300
    CALCULATE RAYLEIGH FREQUENCY
    LOAD 3 LOADTYPE Traffic TITLE LOAD CASE 3
    SELFWEIGHT X 1 LIST 1 TO 88
    LOAD 4 LOADTYPE None TITLE LOAD CASE 4
    ELEMENT LOAD
    41 TO 88 PR GX 300
    LOAD 5 LOADTYPE None TITLE LOAD CASE 5
    REPEAT LOAD
    3 1.0 4 1.0
    CALCULATE RAYLEIGH FREQUENCY
    PERFORM ANALYSIS
    FINISH



  • Ah ha!

    REPEAT LOAD

    excellent!  This is exactly what I was after!

     Thanks