Bi-moment (torsion) in staad pro as per SP 16.13330.2011

Hi

           why staad is not considering the torsional moment B as per SP 16.13330.2011 in Eq F(106).

it shows "      Bi-moment                     :   0.000E+00 Value of Bi-moment not being entered!!!" like this in output file and

 "  CRITICAL CONDITIONS FOR EACH CLAUSE CHECK
      F.(106) (N/A+Mx*y/Iz+My*x/Iy+B*w/Iw)/(Ry*GammaC)=
              ( 476.7E-01/ 1.5E-02+ 959.2E-02* 1.50E-01/ 3.98E-04+ 312.5E-02* 2.00E-01/
               1.20E-04+ 0.000E+00* 2.80E-02/ 4.18E-06)/( 235.0E+03* 1.00E+00)
               = 5.08E-02=<1"

And also whats this BMT in design parameters used for ??!! could any one please help me to understand

This is just fixed beam with some torsion and forces to check.

My Staad pro version is staad pro v8i (select series 6) V 20.07.11.70tap.std

  • Hi

    In continuation to my earlier post I want to know how staad is performing design for Class 2 & 3 as per SP 16.13330.2011. any worked verification (manual cal) for simple beam if shared will be helpful.

    I'm having issue especially with Eq (F51) in which Cx and Cy is arrived. for Af/Aw > 2 staad is taking Cx =0 due to denominator zero it prints stress ratio as 0. To me is Af/Aw > 2 i can strict to the value of Af/Aw=2 given in table F as 1.04 or on safer side 1.0 to avoid this issue.

    And also not able to calculate as per table value 1.47 < 1.15 * load factor (based on moment). whether gamma f is considered = 1 in staad calculation as any one point the moment reached plastic moment in class 2 & 3 cases.

    Af/Aw > 2 is a obvious case in Offshore structures and also when checked for Blast loading case we can use the class 2 & 3 property of beam to design ecnomically.

    This point of application in staad is not clear please kindly anyone clarify my query.

    Thanks in advance for your support

  • This was a known defect in STAAD.Pro SS6:

    The bi-moment is not considered in STAAD.Pro SS6 2007.11.90, the Output reports:
        
     Bi-moment :   0.000E+00 Value of Bi-moment not being entered!!!

    while the parameter BMT is specified.