N-M INTERACTION FOR STEEL JACKET RETROFITTING RC BRIDGE COLUMN DUE TO EARTHQUAKE Mahmoud S. Sayed-Ahmed Biography: M. Sayed-Ahmed is a Research and Graduate Assistant at the Civil Engineering Department, Faculty of Engineering, Architectural and Science (FEAS), Ryerson University, Toronto, ON, Canada. He received his B.Sc. from High Institute of Engineering; M.A.Sc. from Ryerson University, and continuing his PhD in Ryerson University. He is a Canadian Society of Civil Engineering student member (CSCESM). His research interests include steel bridges, glass fiber reinforced polymers (GFRP), and sandwich structures. ABSTRACT: The increase of column capacity ratio for existing structure, especially bridges, is required to adopt the changes of the traffic volume, the environmental loading as the earthquakes, or changes in the design standards. Steel jacket confining reinforced concrete (RC) column is one of the accepted retrofitting methods to enhance the axial and-or shear strength, and improve the ductility for RC structural member. Half-circled steel sheets are welded to form the circular jacket. Numerical study with finite element analysis (FEA) for RC bridge bent-columns integrated with prestressed concrete box-girder deck was performed to study the combined axial- force bending (N-M) interaction for the conventional RC column retrofitted by steel jackets. The study validated the efficiency of the steel jacketing in terms of enhancing the column capacity ratio and the lateral drift ratio.