An experiment-based nonlinear model of shear force-slip relationship for perfobond strips in an unreinforced narrow joint with high-strength steel fiber mortar

Perfobond strips are widely utilized as shear connectors in composite structures or to join precast concrete members. In the case of narrow dimension joints, high-strength steel fiber mortar (SFM) presents a promising alternative instead of normal concrete, as it eliminates the need for surrounding reinforcement. This study endeavors to establish a nonlinear model for the shear force-slip relationship of the perfobond strip in a narrow joint with high-strength SFM, based on a series of push- and pull-out tests. Firstly, the test results of 42 specimens are evaluated and compared with existing models of the shear force-slip relationship from several design codes and previous studies. The findings indicate a weak correlation between the existing models and the experimental results, indicating their unsuitability for this new type of joint. Consequently, both power and exponential functions are utilized to devise a new relationship model of the shear force and slip, accounting for critical values such as shear capacity, initial stiffness, slip at critical points, and behavior of the softening region. The results demonstrate the superiority of the exponentiation-based model, which exhibits a strong correlation with the experimental data, and serves as a criterion for the practical design of this type of joint.