Seismic retrofit of a reinforced concrete bridge bent

This research project is the second part of a research program carried out by Itagawa (2005) who studied the seismic response of a half-scale model of an existing Montreal bridge built in the 1960's. This project studies the seismic behaviour of the retrofit carried out on the frame structure studied in the first part of the research program. The retrofit was made following the requirements of the current Canadian Highway Bridge Design Code (CHBDC). The philosophy of the CHBDC is to provide flexural yielding in the ductile elements so that brittle failure modes such as shear are prevented. This capacity-design approach resulted in a ductile response and significant energy dissipation of the retrofitted structure.The retrofit was designed in accordance with the CHBDC provisions. The cap beam and the beam-column joint regions were strengthened with a reinforced concrete sleeve containing additional transverse and longitudinal bars so that plastic hinging would form in the columns. This retrofit represents minimum intervention to improve the response of the frame. The retrofit frame was then subjected to both gravity loads and reversed cyclic loading to simulate seismic loading on the structure. The predictions of the response of the retrofitted frame provided reasonable estimates of first yielding in the column and the general yielding of the frame. Although the columns would not meet the requirements for ductile columns, they had sufficient shear strength and did exhibit a displacement ductility of about 2.3