SEISMIC EVALUATION OF AL-NAJIBIYA BRIDGE USING PUSHOVER ANALYSIS

Al-Najibiya bridge was designed to be constructed in the north of Basrah province to connect Garmat Ali sub-district to Basrah city crossing Euphrates branch near it's connection with Tigris to form Shat Al Arab river. The bridge consists of 7 spans with a movable (turn over) part for navigation allowance with a total length of 250m. and a width of 16m. The bridge was designed using a forced based design method (FBDM) according to AASHTO 2011[1] specifications. During the implementation of the piles of the bents, technical difficulties faced the contractor due to the high amount of steel reinforcements which required a solution. The bridge owner decides to review the design and reduce the amount of longitudinal rebars in the piles by an amount of 35% with no change to the section dimension. This change eased the implementation but as it believed that most of the reinforcement required by the seismic demands, a more advanced seismic analysis is required to check the performance of the bridge due to the design extreme earthquake. A pushover analysis of the bridge piers is performed to evaluate their capacity compared to their seismic demand. Results reveal acceptable performance of the bridge piers under the extreme design earthquake.