Glossary

Ix = in4

Moment of inertia about the x-x axis (strong axis), used in DEFLECTION calculations.

Sx = in3

Section modulus about the x-x axis, used in STRESS calculations.

Rx = in

Radius of gyration about the x-x axis, used in AXIAL load calculations.

Iy = in4

Moment of inertia about the y-y axis (weak axis).

Sy = in3

Section modulus about the y-y axis.

Ry = in

Radius of gyration about the y-y axis.

Allowable deflection (L/120, L/240, L/360, L/600)

The length of the stud or joist (inches) divided by 120 or 240 or 360 or 600. The permitted deflection of a wall or floor framing member. Allowable deflection is often indicated for wall framing. NOTE: Steel is a ductile or flexible material and can thus perform within a rather large range of deflections. Allowable wall deflection is often indicated by either the project specifications or project architect for the purpose of defining an acceptable wall deflection in order to eliminate the possibility of the wall sheating materials from cracking.

Wind load = lbs./ sq. ft. (PSF)

Forces produced by wind, either direct wind (positive pressure), a vacuum (negative pressure), or those generated by wind whipping around the corners of a building. These forces are usually calculated according to the prevailing building code. Wind forces are referred to as transverse load, are perpendicular to the wall and cause the wall to deflect.

Axial load = lbs.

A vertical force produced by overhead loads such as floors and roofs contain both dead loads and live loads, which combined make up most of the vertical loading.

Combined load

A combination of a transverse load (usually wind) AND axial load.

Header

A joist or beam that is usually a built-up assembly of two or more studs, accepts overhead loads from floors and roofs and distributes the overhead loads to the adjacent studs below.