Buckling restrained braces (BRBs) are widely used as seismic structural fuses to protect the structure's main elements from collapse. Most of the simplified models used to study and design BRBs depend on employing a nonlinear truss element with a constant area along the whole length of the brace. Whereas, the effect of the different regions located along the braces, the two non-yielding parts and the inner core, is represented using an equivalent stiffness calculated based on the geometric properties of each part. In this paper, an enhanced model consisting of shell and truss elements is proposed to allow the study of the geometry of different parts of BRBs while at the same time not significantly increasing the analysis time. The proposed model is verified by comparing the obtained results with the results of two different experimental tests and good agreement is observed. Effects of the varying core lengths in a multi-story building are investigated and analyzed using this model to assess the performance of BRBs. Nonlinear time-history analyses are performed using ABAQUS software. The proposed model can be used effectively to study the properties of BRB such as the areas and lengths of its different parts, which are considered important factors in design, as they are found to have a significant impact on the results.