Buckling
Failure of a column, usually from compressive forces. Determined not only by loads but also by the type of end connection.
K Value
A factor used in column buckling calculations; higher K value = more likely to buckle.
Column End Connections
The type of connection at the top or bottom of a column, which affects its buckling behavior. Types include pinned, moment, free, rotation-fixed/translation-free, and roller.
Pinned Connection
Column end condition where rotation is free but translation is fixed. Depicted with a small triangle between slab and column. Includes a shear connection in steel.
Moment Connection
Column end condition where both rotation and translation are fixed. Depicted with an open slab at the connection.
Free Connection
Column end condition where both rotation and translation are free, like a flagpole. Depicted with a small circle at the connection.
Rotation Fixed / Translation Free Connection
Column end condition where rotation is fixed but lateral translation is allowed. Depicted with a closed box at the connection. Used for seismic isolation.
Roller Support
A support condition that prevents vertical displacement but allows horizontal movement and rotation.
Internal Axial Forces (Normal Forces)
Forces that run along the same axis as the member (horizontally in a beam), causing tension or compression.
Tension (Beam)
Axial force along the bottom of a loaded beam; members stretch in tension.
Compression (Beam)
Axial force along the top of a loaded beam; members are squeezed together.
Shear Forces
Forces that run perpendicular to the axis of a member (vertically on a beam), causing layers or planes of the member to want to slide past each other.
Vertical Shear
Shear force caused by a column pushing up on a beam, acting in the opposite direction from the loads pushing down.
Moment
A measure of a force acting perpendicular to a distance, causing rotation or bending. Mathematically the same as torque, though moment typically describes bending.
Bending Moment
A moment that causes bending in a structural member. See also: Moment.
Torque
A measure of a rotational force, mathematically the same as moment. Torque typically describes twisting/rotation, while moment typically describes bending.
Deflection
The physical deformation resulting from bending; the displacement of a member when a load is applied.
Simply Supported
A beam or member supported at two ends only.
Kip
A unit of force equal to 1000 lbs.
KSI
Kips per square inch; a unit of stress.
PSI
Pounds per square inch; a unit of stress.
w (Load Symbol)
In moment equations: total load/weight per linear unit (e.g. plf). If given in PSF, convert by multiplying by the spacing of members.
W (Max Weight Symbol)
In moment equations: maximum weight for an unevenly distributed load, expressed per linear unit (e.g. plf).
L (Length Symbol)
In moment equations: the length of the member.
