Product(s):	SACS
Version(s):	ALL
Area:	SACS Solve

 

ANGLE CROSS-SECTIONS:

 

The orientation of an angle section is determined from the signs of the A and B dimensions input on the 'SECT' input line.

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SACS IV uses properties about the member principal axes for stiffness calculations. 

Normally, the cross-section input local axes are axes of symmetry and are therefore principal axes. For angles, however, the input axes are not principal axes. Therefore, the inertia properties calculated about the input axes must be transformed to the principal axes by the program using the following:

The shear areas about the principal axes are used in member stiffness calculations and are taken as:

where the IVi and QVi are with respect to the m principal axis.

 

Bending stress and Euler buckling stress are calculated with respect to the principal axes. The effective buckling length factors, Ky and Kz, are input with respect to the local coordinates. The program transforms the input K-factors into the principal axes system to obtain the factors to be used in Euler buckling calculations, from:

Where:

K1,2 = Principal axes effective length factors
Ky,z = Input effective buckling length factors
α = Angle between input axes and principal axes

The shear stress at any point is calculated with respect to the local coordinate system using the following equation:

Where:

Iy, Iz, Iyz = Inertia properties with respect to Y and Z axes
Vy, Vz = Shear in Y and Z directions
t = Thickness
Qy, Qz = First moments about Y and Z axes of a portion of the cross-section area between the point and the free edge (Shaded area in the figure below).