Abstract: The vital role of bridges, as one of the main urban facilities, in emergencies especially after destructive earthquakes made seismic evaluation of bridges even much more significant in loss and economic estimations. Middle span regular steel I-girder bridge is one of the most common types of bridges in the world that has been considered rarely hence, seismic evaluation of these bridges can reveal efficient results in loss and damage mitigation for engineers. This study was conducted to evaluate the analytical approach and the degree of accuracy and reliability of the simplified method of the codes and performance-based method in bridges. To this end, large scale of two common bridges (steel piers and reinforced concrete slab) was modeled and analyzed using Finite Element Method (FEM). In first model the obtained results of modal analysis were compared with the results of grillage model and simplified methods of the codes. Then in the second model, results of time history dynamic analyses (linear and nonlinear), spectrum analysis (CQC and SRSS), push-over (performance point of the bridge) were compared to find the effectiveness of them. The output volume and timing of each analysis was considered. The results showed the great accuracy of push-over analysis and some Code methods. It also showed that, time consuming process and large volume of output in nonlinear FEM dynamic analysis and push-over analysis methods made them ineffective for seismic analysis of bridges. Also, performance point can be obtained accurately if the load pattern is suitable. Regarding the obtained results of this study it is suggested to apply simplified methods or spectral analysis for large scale regular-bridge models.