OpenSTAAD function to extract the capacity of members

Member capacities can certainly change per load case. Take for example the lateral torsional buckling capacity Mn defined in AISC 360-16 (F2-2) is dependent on the value of Cb, the lateral torsional buckling modification factor defined in (F1-1) As you know this factor is about the moment profile, hence different in each load case.

hi,

what we are looking for is the highligted member capacities which is listed in steel design report in my previous comment, it not requried for all load cases. i hope there will not any change in member capacities based on different load cases forces, since the member capacity is based on member properties and material of construction which is same for all load cases.

if design code is with allowable stress, then member capacity can be reported as NA.( Not applicable).

So you are looking for the 9 capacities from the governing load case, i.e..

1) Axial Tensile capacity, major axis

2) Axial Tensile capacity, minor axis

3) Axial Compressive capacity, major axis

4) Axial Compressive capacity, minor axis

5) Shear capacity, major axis

6) Shear capacity, minor axis

7) Bending capacity, major axis

8) Bending capacity, minor axis

9) Lateral Torsional Buckling (LTB) capacity.

Would it not make more sense to report these from ALL design load cases?

What I mean is that say a member is designed in 2 load cases the first has a higher overall ratio, but it may that in the second load case, one of the conditions results in a lower capacity. So the nine values are reported from each load case.

Also different design codes require different checks. How would you report a capacity if the code does not have such a check. E.g. stress codes like the AISC 9th Edition would not report LTB capacities. If 0.0 is reported, how would you know if it was not supported rather than having no capacity? Perhaps reporting a capacity of -1 means not determined and 0.0 means no capacity.

Thanks for your reply,

please find below a example case with what need, this is the steel design result we got from staad analysis output for one member.

in this report, member design detailed output is provided. in that we need the Below YELLOW Highlighted results as a openstaad function output. hope this clarifies our requirement.

EMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/

FX MY MZ LOCATION

=======================================================================

615 ST H150X150X7X10 (JAPANESE SECTIONS)

PASS Eq. H1-1a 0.306 102

40.49 C -0.06 -2.52 4.80

|-----------------------------------------------------------------------|

| SLENDERNESS |

| Actual Slenderness Ratio : 157.901 L/C : 102 |

| Allowable Slenderness Ratio : 200.000 LOC : 4.80 |

|-----------------------------------------------------------------------|

| STRENGTH CHECKS |

| Critical L/C : 102 Ratio : 0.306(PASS) |

| Loc : 4.80 Condition : Eq. H1-1a |

|-----------------------------------------------------------------------|

| DESIGN FORCES |

| Fx: 4.049E+01(C ) Fy: 8.126E-01 Fz: -2.010E-02 |

| Mx: 2.651E-04 My: -6.493E-02 Mz: -2.523E+00 |

|-----------------------------------------------------------------------|

| CHECK FOR AXIAL TENSION |

| |

| FORCE CAPACITY RATIO CRITERIA L/C LOC |

| Yield 0.00E+00 5.82E+02 0.000 Eq. D2-1 101 0.00 |

| Rupture 0.00E+00 7.93E+02 0.000 Eq. D2-2 101 0.00 |

|-----------------------------------------------------------------------|

| CHECK FOR AXIAL COMPRESSION |

| |

| FORCE CAPACITY RATIO CRITERIA L/C LOC |

| Maj Buck 4.25E+01 3.75E+02 0.113 Eq. E3-1 104 0.00 |

| Min Buck 4.25E+01 1.69E+02 0.252 Eq. E3-1 104 0.00 |

| Flexural |

| Tor Buck 4.25E+01 4.79E+02 0.089 Eq. E4-1 104 0.00 |

|-----------------------------------------------------------------------|

| CHECK FOR SHEAR |

| |

| FORCE CAPACITY RATIO CRITERIA L/C LOC |

| Local-Z 1.72E-01 2.64E+02 0.001 Eq. G2-1 111 0.00 |

| Local-Y 8.13E-01 1.03E+02 0.008 Eq. G2-1 102 0.00 |

STAAD SPACE -- PAGE NO. 37

STAAD.PRO CODE CHECKING - ( AISC-360-10-ASD) v1.4a

********************************************

ALL UNITS ARE - KN METE (UNLESS OTHERWISE Noted)

|-----------------------------------------------------------------------|

| CHECK FOR BENDING-YIELDING |

| |

| FORCE CAPACITY RATIO CRITERIA L/C LOC |

| Major 2.52E+00 3.56E+01 0.071 Eq. F2-1 102 4.80 |

| Minor -1.61E-01 1.67E+01 0.010 Eq. F6-1 204 4.80 |

|-----------------------------------------------------------------------|

| CHECK FOR BENDING-LATERAL TORSIONAL BUCKLING |

| |

| FORCE CAPACITY RATIO CRITERIA L/C LOC |

| Major 2.52E+00 3.56E+01 0.071 Eq. F2-2 102 4.80 |

|-----------------------------------------------------------------------|

| CHECK FOR FLEXURE TENS/COMP INTERACTION |

| RATIO CRITERIA L/C LOC |

| Flexure Comp 0.306 Eq. H1-1a 102 4.80 |

| Flexure Tens 0.075 Eq. H1-1b 102 4.80 |

|-----------------------------------------------------------------------|

|-----------------------------------------------------------------------|

| SEISMIC PROVISION(AISC 341:10):- |

| |

| MOMENT FRAME TYPE: OMF |

| |

| SEISMIC CLASSIFICATION: FLANGE: Compact WEB: Compact |

| |

| REQUIREMENTS:- VALUE CRITERIA |

| EXPECTED FLEXURAL STRENGTH 1.18E+00 Sec. E.1.4. |

| BRACING STRENGTH 6.76E-02 Eq. A-6-5 |

| BRACING STIFFNESS 1.41E+01 Eq. A-6-6 |

| BRACING SPACING 0.00E+00 |

|-----------------------------------------------------------------------|

| MOMENT FRAME TYPE: OMF |

| |

So you are just looking for the axial capacity. However, that can be different depending on the applied loading, so you would be asking for a function that you would provide the member number AND load case AND the design code, THEN the function returns the axial direction (i.e. tension or compression) AND the axial capacity. Does that correctly frame your idea?

we need to get the capacity of member used for the calculation of steel design ratio. For e.g in steel design output , we have axial capacity of member which is compared with actual axial forces to give the steel utilization ratio. we need that axial capacity of member to use for additional checks.

Thank you for posting this idea. However, this perhaps requires a little more detail. Depending on the code that the member is being checked against, there may be many different capacities compression, tension, major and minor bending, torsional etc. Those capacities may vary at different positions along the member and under different load cases. If you are thinking about just having a report of the minimum capacities for all load cases and all positions? If so you might be performing your additional checks on results that are not coincident.