A condition in structural analysis and mechanics where a joint, support, or shell carries only axial or shear forces without resisting rotation. Engineers model pin joints and thin membranes as lacking the capacity to support bending moments. This simplification allows for statically determinate calculations in trusses and tensile structures.
Treat the truss connections as momentless for the initial hand calculation before running the full finite element model.
Assuming a joint is perfectly momentless is a common modeling simplification, but real-world friction always introduces some small bending resistance.
Related terms
Moment
The tendency of a force to rotate an object about an axis or pivot.
Torque
To tighten a threaded fastener to a specific rotational force.
Force pair
Two forces of equal magnitude acting in opposite directions on interacting bodies.
FEM
The finite element method, a numerical technique for solving complex engineering problems.