SACS 13.2_Unusual High Member UC

Hi Sir/Madam,

  There is unexpected high out of plane bending UC based on API22 by using SACS 13.2, see attached screenshot and Detailed Calculation as below.

  Manual computation of UC based on actual / allowable bending stress is small but SACS is giving unreasonable large UC.

  Please advise.

 

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        Detailed review report of member  3410 - 3406

     <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<


     Units: Length -(cm)         Force -(kN)         Stress -(N/mm2)

     Design Code - API RP2A,22nd 
     ------------------------------------------------------------------------

     ****** Member Infomation ******

     Group                               41   

     Section Name                        Tubular  

     Total Length                        13.82  (m) 

     Location                             0.00  (m) 

     Segment                             1 of 2

     LC Option                           Single 

     Critical LC                         OP17 

     AMOD                                 1.00


     ------------------------------------------------------------------------

     ****** Basic Properties ******

     Section Type                         Tubular

     Outer Diameter                       55.88

     Wall Thickness                        1.27

     Elastic Modulus                     210.00  1000(N/mm2)

     Shear Modulus                        80.00  1000(N/mm2)

     Yield Strength                      345.01  (N/mm2)

     Axial Area              A           217.88

     Mom. of Inertia         Iy        8.1E+004

     Mom. of Inertia         Iz        8.1E+004

     Shear Area Y                        108.94

     Shear Area Z                        108.94

     Tors. Constant          J         1.6E+005

     ------------------------------------------------------------------------

     ****** Member's Properties ******

     Slenderness Ratio     (KL/r)y        64.09

     Slenderness Ratio     (KL/r)z       142.59

     Radius of Gyration      ry           19.31

     Radius of Gyration      rz           19.31

     Eff. Length Factor      Ky            0.90

     Eff. Length Factor      Kz            0.90

     Overall Buck. Length    Ly           13.80  (m) 

     Overall Buck. Length    Lz           30.70  (m) 

                   Final (K*L)y           12.42  (m) 

                   Final (K*L)z           27.63  (m) 

      - Segmented Member:  Overall buckling length is re-calculated
        from apprximate buckling load effectively at this segment.
                           Leffy          13.77    (m)
                           Leffz          13.77    (m)
     TUB Ring Spacing                     13.82  (m) 

     Reduction Factor        Cmy           0.85

     Reduction Factor        Cmz           0.85

     ------------------------------------------------------------------------
     ****** End Forces and Moments ((kN), (kN-m)) ******

     Tor. Moment             Mx           -3.3895

     Bending Moment          My           38.3418

     Bending Moment          Mz            9.2645

     Axial force             fx        -1148.9885

     Shear force             fy           -0.9487

     Shear force             fz           -7.5851

     ------------------------------------------------------------------------

     ****** Actual Stresses ******

     Axial stress            fa          -52.7339

     Bending Major           fby          13.1821

     Bending Minor           fbz           3.1852

     Resultant Shear         fv            0.7017

     Torsional Shear         fvt          -0.5827

     ------------------------------------------------------------------------

     ****** Allowable Stresses ******


     --- Allowable Stresses without Hydrostatic Pressure    

     Axial Tension           Ft          207.0001     (6.1)

     Shear                   Fv          138.0001     (6.12)

     Axial Compression       Fa           53.1890     (6.2~5)

     Bending about Y         Fby         246.4070     (6.6~8)

     Bending about Z         Fbz         246.4070             

     Euler Buckling Y        Fey         263.2328     (6.3)

     Euler Buckling Z        Fez          53.1890    

     Elastic Loc Buckling    Fxe        2863.6379     (6.4)

     INelast Loc Buckling    Fxc         345.0002     (6.5)


     --- Allowable Stresses with Hydrostatic Pressure

     Axial                                53.1890

     Major Axis Bending                  246.4070

     Minor Axis Bending                  246.4070    

     Shear in Local Y                    138.0001    

     Shear in Local Z                    138.0001    

     Euler Buckling                       53.1890    

     ------------------------------------------------------------------------

     ********     Unity Ratios     ********

     Critical Unity Ratio                  2.2769      (6.20      )     Cmp>.15A

     Combined Unity Ratio                  2.2769      (6.3.2~5)

     Axial Component                       0.9914    

     Bending Major Y-Y                     0.0025    

     Bending Minor Z-Z                     1.2829    

     Shear in Y                            0.0093    

     Shear in Z                            0.0042    

     Euler Buckling Y-Y                    0.2003    

     Euler Buckling Z-Z                    0.9914    

     ------------------------------------------------------------------------

     ****** Hydrostatic Pressure Analysis ******
    

--- Parameters

     Safety Fac. Tension        SFxt        1.6700    

     Safety Fac. Compression    SFxc        2.0000    

     Safety Fac. Bending         SFb         1.4001    

     Safety Fac. Hoop Comp      SFh         2.0000    

     Crit Hoop Buck. Coeff.      Ch         0.0100    

     Geometric Parameter          M       232.0019    

     Imperf. Reduc. Fac        Alpha        0.8000    

     Water Depth                  d        78.2360  (m) 

     Water Depth at Member        z        30.5356  (m) 

     Wave Height                  Hw        0.0000  (m) 

     Wave Length                  L       N/A
                    


     --- Stresses    

     Hoop Stress                fh         6.7856     (6.14)

     Axial Stress               fa       -52.7339    

     Result Bending Stress      fb        13.5614    

     Elastic Hoop Buck Stress  Fhe        95.4546     (6.16)

     Crit Hoop Buck Stress     Fhc        95.4546     (6.18)
          'NOTE: Marine Method selected'

     --- Hydrostatic UC Ratios    

     MAX Hydro Collapse UC                 0.3804

     Combined Tension and Hydro UC         0.0000     (6.26)

     Combined Comp and Hydro UC            0.3804     (6.27)

     Hoop Compression UC                   0.1422     (6.28)

     Large Compression UC                  0.0528     (6.29)

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