Beam properties

A beam is a one-dimensional member that carries axial force, bending, shear and torsion. Describing that behaviour takes eight parameters rather than the two a truss needs.

The tab is shown when the element type is set to Beam.

Parameters

Parameter	Unit	Meaning
A	m²	Cross-sectional area
E	kN/m²	Young's modulus
G	kN/m²	Shear modulus
I_yy	m⁴	Second moment of area about the local y-axis
I_zz	m⁴	Second moment of area about the local z-axis
J	m⁴	St. Venant torsional constant
kappa_y	–	Shear correction factor in the local y-direction
kappa_z	–	Shear correction factor in the local z-direction

A and E give the axial stiffness, as for a truss. I_yy and I_zz give the bending stiffness about the two local axes, J and G the torsional stiffness, and the two shear correction factors account for shear deformation across the section.

Units are shown for the m section unit. With mm selected, the area is read in mm² and the second moments in mm⁴.

Note

Enter every value in the unit currently selected above. The manager does not convert values that are already in the table when the unit is changed, and a second moment left in mm⁴ while the unit says m⁴ is wrong by twelve orders of magnitude.

Profile

Selecting an IPE profile from the Profile list fills A, I_yy, I_zz and J for the chosen section, converted to the section unit currently selected.

E, G, kappa_y and kappa_z remain your inputs. For structural steel E and G are the usual constants; the shear correction factors depend on the shape of the section.

Validation

All eight parameters must be filled, along with the density. Pressing Apply & Save with one missing shows a warning naming the problem, and the material stays open so it can be corrected.

See Beam properties in the numgeo reference manual.