Bond slip CEB-FIP 1990 Model Code 90

The extra slip displacements are determined from the condition that the bond shear stresses cannot exceed maximum allowed shear stress $\tau_{b,max}$ as a function of the size of the slip $s$.

$$\tau_{b,max} = \tau_{max} ( \frac{s}{s_1} ) ^ \alpha ~~~~~~~~ 0 <= s <= s_1$$

$$\tau_{b,max} = \tau_{max} ~~~~~~~~ s_1 <= s <= s_2$$

$$\tau_{b,max} = \tau_{max} - ( \tau_{max} - \tau_f ) \frac{s-s_1}{s_3-s_2} ~~~~~~~~ s_2 <= s <= s_3$$

$$\tau_{b,max} = \tau_f ~~~~~~~~ s_3 <= s$$

You need to specify in group_truss_bond_slip_ceb_fip_1990 the parameters of the CEB-FIP 1990 Model Code 90.