SEISMIC RETROFIT OF BRIDGE COLUMNS USING PREFABRICATED COMPOSITE JACKETS

This paper describes an on-going multi-phase research program to develop methods for seismic analysis and retrofit design of bridge columns using prefabricated composite jackets. Nine half-scale model circular columns have been tested and the results established the effectiveness of the prefabricated composite jackets for strength enhancement and ductility improvement. A construction test with retrofitting two actual columns of a typical California bridge also demonstrated the superior constructability of prefabricated composite jacketing. Several recent destructive earthquakes have alerted the society the urgent need to upgrade existing older bridges to current seismic design standards in regions with high seismicity. Although steel jacketing has been widely used in practices in California and elsewhere, the society is also looking for other alternatives to improve the retrofitting process for the vast number of existing, structurally deficit bridges both in the U.S., and throughout the world. One of the key areas is east to construction. Advanced composite materials have been recently recognized and applied to bridge retrofit. The general expectations from composite retrofit systems include light weight, high stiffness or strength to weight ratios, etc. Several composite jacketing systems have been developed and validated in laboratory or field conditions. These composite retrofit measures can be categorized as in-situ fabricated jacketing which involves hand or automated machine placement of epoxy saturated glass or carbon fabrics on the surface of existing concrete. An in-situ fabricated jacket can match the shape of the existing column. However, due to the fact of in-situ fabrication, these systems may need special attention to the job-site quality control and curing of the composite jackets. This paper presents the results of investigations on prefabricated composite jacketing systems for retrofitting reinforced concrete columns.