Member Nonlinearity

Nonlinearities related to members can be employed to depict nonlinear connections between forces (or moments) and strains within the members. Some nonlinear attributes can be established during the specification of the member type itself. For instance, a tension member can be conceived as a truss where strain increases proportionally with tension force. However, such a member's strain might escalate under compression without a ascertainable force being necessary for this phenomenon.

In principle, member nonlinearities are applicable to various member types, albeit logical combinations must be ensured. For instance, designating "Failure under compression" as the criterion for a compression member would lead to computational issues. Consequently, member nonlinearities are proscribed for tension members, compression members, buckling members, and cable members.

Member Type	Diagram in RFEM	Description
Failure if tension	01 Member Nonlinearity "Tension"	The member cannot absorb tensile forces.
Failure if compression	02 Member Nonlinearity "Compression"	The member cannot absorb compressive forces.
Failure under tension with slippage	03 Member Nonlinearity "Tension Slippage"	The member cannot absorb tensile forces. Compressive forces are not absorbed until the slippage ux is overcome.
Failure under compression with slippage	04 Member Nonlinearity "Compression Slippage"	The member cannot absorb compressive forces. Tensile forces are not absorbed until the slippage ux is overcome.
Slippage	05 Member Nonlinearity "Slippage"	The member only absorbs axial forces after having exceeded a strain or shortening by the value ux. Note: A line refinement on a member with Slippage causes an internal member division into small member parts. The slippage criterion is applied to each of these partial members.
Failure under tension	06 Member Nonlinearity "Tension Failure"	The member absorbs compressive forces without limitation, but fails if tensile forces exceed Nt.
Yielding under tension	07 Member Nonlinearity "Tension Yield"	The member absorbs compressive forces without limitation, but only a maximum tensile force of Nt. If the strain increases, the tensile force remains constant in the member.
Failure under compression	08 Member Nonlinearity "Compression Failure"	The member absorbs tensile forces without limitation but fails if compressive forces exceed Nc.
Yielding under compression	09 Member Nonlinearity "Compression Yield"	The member absorbs tensile forces without limitation, but only a maximum compressive force of Nc. If the strain increases, the compressive force remains constant in the member.
Failure	10 Member Nonlinearity "Failure"	The member fails when the compressive force Nc or the tensile force Nt is reached.
Yielding	11 Member Nonlinearity "Yielding"	The member starts to yield if the compressive force Nc or the tensile force Nt is reached: If the strain increases, the force remains constant.