Gap/Hook curve - gap_hk

This is a curve employed to model structural gapping/pounding, expansion joints, deck restrainers, and so on. Four parameters need to be defined:

Locking/Engaging displacement in positive region (d+)
The default value is 5

Gap/Hook stiffness in positive region (K+)
The default value is 1e12

Locking/Engaging displacement in negative region (d-)
The default value is -5

Gap/Hook stiffness in negative region (K-)
The default value is 1e12

Note: Stiffness values K+ and K- must be positive.