<p>Rock joints play an important role in the overall stability of rock masses. The existing models characterize the shear stress evolution of rock joints in the pre-peak and post-peak stages with non-smooth transitions, and their numerical efficiency can be further improved. A reduced-order constitutive model is proposed by assembling multiple spring–slider–separator (SSS) elements in parallel, which captures the continuous evolution of shear stiffness observed in experiments. The SSS elements provide an intuitive description of stress softening induced by interface damage, while reducing the number of interface degrees of freedom and thereby improving computational efficiency in general numerical frameworks. The modeling parameters are expressed as functions of shear displacement and can be directly calibrated from experimental data. Based on the discretized model, a displacement-incremental algorithm is developed to describe the shear behavior of rock joints. The results demonstrate that the proposed model accurately reproduces joint deformation in both pre-peak and post-peak stages, with the evolution of shear stress at peak closely matching experimental observations. High numerical accuracy is achieved using only 24 elements, yielding peak and residual stress errors of 1.38% and 0.79%, respectively, while a complete direct shear simulation of a single joint requires only 0.18&#xa0;s. Further application of the proposed model to cyclic loading tests confirms its capability to reproduce the shear behavior of rock joints.</p>