Structural Engineering

Hello Everyone,

I designed a Tapered Built up section in STAAD as per AISC 360-10 and the same member as per AISC 360-16. The member failed in AISC 360-16. Can anyone help on this?

Can someone explain me how STAAD calculates Elastic section modulus about x axis referred to Compression flange (Sxc).

Thanks In advance.

  • Can you send a sample file to illustrate the failure? Also, please confirm the version of STAAD you are using. 



  • I am currently using STAAD 21.03.00.146 version.

    Please find the sample file below. The same file has been run using AISC UNIFIED 2016. It shows that the member has failed. I found that the member failed in Bending. Can you please illustrate how Iyc and Sxc are calculated for finding Rpc and Rpt.

    Thanks in Advance.

    STAAD PLANE
    ********************************************************
    START JOB INFORMATION
    JOB NAME 2010
    JOB CLIENT 2010
    JOB NO 2010
    JOB REV 0
    ENGINEER NAME tvb
    APPROVED NAME KJ
    ENGINEER DATE 15-Feb-19
    END JOB INFORMATION
    ********************************************************
    INPUT WIDTH 79
    ********************************************************
    UNIT METER KN
    JOINT COORDINATES
    1 0 0 0; 2 20.686 0 0; 3 0 6.426 0; 4 20.686 6.426 0; 5 10.343 7.4603 0;
    6 0 3.048 0; 7 20.686 3.048 0; 10 16.3132 6.86328 0; 11 13.3281 7.16179 0;
    12 4.37278 6.86328 0; 13 7.35789 7.16179 0;
    *NODE X Y Z
    MEMBER INCIDENCES
    1 1 6; 2 6 3; 3 2 7; 4 7 4; 10 3 12; 11 12 13; 12 13 5; 13 11 5; 14 10 11;
    15 4 10;
    ********************************************************
    DEFINE MATERIAL START
    ISOTROPIC STEEL
    E 2.05e+08
    POISSON 0.3
    DENSITY 76.8195
    ALPHA 1.2e-05
    DAMP 0.03
    END DEFINE MATERIAL
    ********************************************************
    CONSTANTS
    MATERIAL STEEL ALL
    ********************************************************
    UNIT MMS KN
    MEMBER PROPERTY AMERICAN
    ********************************************************
    * COLUMN
    1 3 TAPERED 262 5 462 150 8
    2 4 TAPERED 462 5 666 150 8
    * RAFTER
    10 15 TAPERED 662 5 462 150 8
    11 14 TAPERED 462 5 462 150 6
    12 13 TAPERED 462 5 462 150 6
    ********************************************************
    SUPPORTS
    1 2 PINNED
    ********************************************************
    ******************** SEISMIC FORCE ***********************
    * IS 1893(PART-1) 2002 ZONE-III,I=1.00;R=5.0;
    UNIT METER KN
    DEFINE 1893 LOAD
    ZONE 0.16 RF 5 I 1 SS 2 ST 2
    *
    SELFWEIGHT 1
    MEMBER WEIGHT
    * 0.1 * 7.877 = 0.79 KN/M
    10 TO 15 UNI 0.79
    * 0.57 * 7.877 * 0.25 = 1.13 KN/M
    10 TO 15 UNI 1.13
    *
    LOAD 1 EQ +X DIR
    1893 LOAD X 1
    PERFORM ANALYSIS
    CHANGE
    *
    LOAD 2 EQ -X DIR
    1893 LOAD X -1
    PERFORM ANALYSIS
    CHANGE
    ********************************************************
    LOAD 3 DEAD LOAD
    ************
    SELFWEIGHT Y -1
    * 0.1 * 7.877 = 0.79 KN/M
    MEMBER LOAD
    10 TO 15 UNI GY -0.79
    ********************************************************
    LOAD 4 LIVE LOAD
    **************
    * 0.57 * 7.877 = 4.49 KN/M
    MEMBER LOAD
    10 TO 15 UNI GY -4.49
    * COLL LOAD
    * 0 * 7.877 = 0 KN/M
    10 TO 15 UNI GY 0
    ********************************************************
    ************** WIND PRESSURE CALCULATIONS ****************
    * WIND SPEED = 33 M/SEC
    * WIND PRESSURE = 0.54 KN/M2
    **************************************
    * WIND ANGLE PERPENDICULAR *
    **************************************
    * ON LEFT COLUMN
    * 0.22 * 0.54 * 7.877 = 0.94 KN/M
    * ON RIGHT COLUMN
    * -0.47 * 0.54 * 7.877 = -2 KN/M
    * ON LEFT RAFTER
    * -0.87 * 0.54 * 7.877 = -3.69 KN/M
    * ON RIGHT RAFTER
    * -0.55 * 0.54 * 7.877 = -2.34 KN/M
    *************************************
    * WIND ANGLE PARALLEL *
    *************************************
    * ON COLUMN
    * -0.63 * 0.54 * 7.877 = -2.68 KN/M
    * ON RAFTER
    * -0.87 * 0.54 * 7.877 = -3.69 KN/M
    *************************************
    LOAD 5 WL LEFT
    MEMBER LOAD
    1 2 UNI GX 0.94
    3 4 UNI GX 2
    10 TO 12 UNI Y 3.69
    13 TO 15 UNI Y 2.34
    ********************************************************
    LOAD 6 WL RIGHT
    MEMBER LOAD
    1 2 UNI GX -2
    3 4 UNI GX -0.94
    10 TO 12 UNI Y 2.34
    13 TO 15 UNI Y 3.69
    ********************************************************
    LOAD 7 WL PARALLEL
    MEMBER LOAD
    1 2 UNI GX -2.68
    3 4 UNI GX 2.68
    10 TO 12 UNI Y 3.69
    13 TO 15 UNI Y 3.69
    ********************************************************
    **************************
    ** LOAD COMBINATIONS **
    **************************
    LOAD COMB 8 1.0DL + 1.0LL
    3 1.0 4 1.0
    LOAD COMB 9 0.6DL + 1.0WLL
    3 0.6 5 1.0
    LOAD COMB 10 0.6DL + 1.0WLR
    3 0.6 6 1.0
    LOAD COMB 11 0.6DL + 1.0WLP
    3 0.6 7 1.0
    LOAD COMB 12 0.6DL + 0.7EL +X
    3 0.6 1 0.7
    LOAD COMB 13 0.6DL + 0.7EL -X
    3 0.6 2 0.7
    ********************************************************
    PERFORM ANALYSIS
    LOAD LIST 8 TO 13
    PARAMETER 1
    CODE AISC UNIFIED 2010
    METHOD ASD
    FYLD 345000 ALL
    FU 490000 ALL
    BEAM 1 ALL
    MAIN 180 ALL
    CB 0 ALL
    STP 2 ALL
    TRACK 2 ALL
    ********************************************************
    ********************
    * DESIGN PARAMETRS *
    ********************
    * COLUMN
    LX 1.5 MEMB 2 4
    LY 1.5 MEMB 2 4
    UNT 1.5 MEMB 2 4
    UNB 1.5 MEMB 2 4
    LZ 6.426 MEMB 1 TO 4
    *************
    * RAFTER
    LX 1.5 MEMB 10 TO 15
    LY 1.5 MEMB 10 TO 15
    UNT 1.5 MEMB 10 TO 15
    UNB 1.5 MEMB 10 TO 15
    LZ 10.395 MEMB 10 TO 15
    ********************************************************
    CHECK CODE ALL
    UNIT METER KG
    STEEL TAKE OFF ALL
    FINISH

  • Sorry I could not get to it today. I will do so tomorrow and get back to you with my response.