$matTag

unique material object integer tag

$u1p

$q1p

slip and bond at first detachment -- tensile bond-slip backbone

$u2p

slip at start of degradation -- tensile bond-slip backbone

$u3p

$q3p

slip and bond at ultimate -- tensile bond-slip backbone

$u1n

$q1n

slip and bond at first detachment -- compressive bond-slip backbone*

$u2n

slip at start of degradation -- compressive bond-slip backbone*

$u3n

$q3n

slip and bond at ultimate -- compressive bond-slip backbone*

$s0

unloading stiffness

$bb

exponent for the first branch of the backbone (prior to first detachment). i.e. q=u^bb