D9.B.2 Member Capacities
D9.B.2.1Design Capabilities
All types of available shapes like H-Shape, I-Shape, L-Shapes, CHANNEL, PIPE, TUBE, etc. can be used as member property and STAAD.Pro will automatically adopt the design procedure for that particular shape if Steel Design is requested. STEEL TABLE available within STAAD.Pro or UPTABLE facility can be used for member property.
D9.B.2.2Methodology
For steel design, STAAD.Pro compares the actual stresses with the allowable stresses as required by AIJ specifications. The design procedure consist of following three steps.
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Calculation of sectional properties
The program extracts section properties cross sectional area, A, moment of inertia about Y and Z axes, Iyy and Izz , and the St. Venant torsional constant, J, from the built-in steel tables. The program then calculates the elastic section moduli, Zz and Zy , torsional section modulus, Zx , and radii of gyration, iy and iz , using the appropriate formulas.
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Calculation of actual and allowable stresses
Program calculates actual and allowable stresses by following methods:
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Axial Stress:
Actual tensile stresses,
Actual compressive stress , FC = force / A
Allowable tensile stress, ft
- =
FYLD
/ 1.5 (For Permanent Case) - =
FYLD
( For Temporary Case )
Allowable compressive stress, fc
Actual torsional stress, ft = torsion / Zx
- =
-
Bending Stress:
Actual bending stress for My for compression:
( Fbcy) = My / ZcyActual bending stress for Mz for compression
( Fbcz) = Mz / ZczActual bending stress for My for tension
( Fbty ) = My / ZtyActual bending stress for Mz for tension
Allowable bending stress for My
(fbcy) = ftAllowable bending stress for Mz
When λb ≤ pλb , fb = F/ν
When pλb < λb ≤ eλb ,
When eλb < λb ,
Note: M2/M1 will be +ve for double curvature and -ve for single curvature.For Temporary case, fbcz = 1.5 x (fbcz for Permanent case)
Note: The parameterCB
can be used to specify a value for C directly. -
Shear Stress
Actual shear stresses are calculated by the following formula:
Allowable shear stress:
- Permanent Loads: fs = (Fy/√(3))/ 1.5
- Temporary Loads: fs = Fy / √(3)
-
-
Checking design requirements:
User provided
RATIO
value (default 1.0) is used for checking design requirements:The following conditions are checked to meet the AIJ specifications. For all the conditions calculated value should not be more than the value of
RATIO
. If for any condition value exceedsRATIO
, program gives the message that the section fails.Conditions:
- Axial tensile stress ratio = FT / ft
- Axial compressive stress ratio = FC / fc
- Combined compression & bending compressive ratio = FC / fc+Fbcz/fbcz+Fbcy/fbcy
- Combined compression & bending tensile ratio = (Fbtz+Fbty-FC) / ft
- Combined tension & bending tensile ratio = (FT+Fbtz+Fbty) / ft
-
Combined tension & bending compressive ratio = Fbcz/fbcz+Fbcy/fbcy- FT/ft
- Shear stress ratio in Y = qy / fs
- Shear stress ratio in Z = qz / fs
- von Mises stress ratio (if the von Mises stresses were set to be checked) = fm/(k⋅ft)