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Material Properties, Sections & Member Orientation - Material Properties And Sections

Connect section geometry and material properties to EA, EI and GJ; assign sections/materials correctly; and verify strong/weak-axis orientation, beta angles, modifiers, releases, and member specifications.

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Section Geometry → Material → Stiffness

Geometry controls A and the centroidal section inertias. Material stiffness E and G then convert those geometric properties into EA and EI.

Material preset

The G relation below assumes a linear isotropic material. Orthotropic materials such as structural timber require directional elastic constants rather than this isotropic shortcut.

Area A
112,500 mm²
Shear modulus G
76.9 GPa
Ih = b h³/12
1.90e+9 mm⁴
Iv = h b³/12
5.86e+8 mm⁴
EA
22500.0 MN
Strong-axis EI
379.69 ×10¹² N·mm²
horizontal section axisvertical section axis
Axis note: this is a cross-section view. These two lines are centroidal section axes—not the STAAD member-local x-axis. Member-local x runs longitudinally along the member, out of this section plane.

Behavior check: 6 m simply supported member, 20 kN midspan point load

Strong-axis bending
0.24 mm
Uses the larger of the two centroidal inertias
Weak-axis bending
0.77 mm
Uses the smaller of the two centroidal inertias

Try changing only E: A and both section inertias stay constant, while EA, EI and deflection change. If b becomes larger than h, the strong/weak designation follows the actual larger/smaller inertia rather than a hard-coded axis name.

G=E2(1+ν),δmid=PL348EIG=\frac{E}{2(1+\nu)},\qquad \delta_{mid}=\frac{PL^3}{48EI}

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