EVALUATION AND CFRP STRENGTHENING OF EXISITNG GARAGE: A CASE STUDY

Over the last five years, fiber reinforced polymers (FRP) have been introduced to the US civil engineering community as a product to externally strengthen existing reinforced-concrete structures. Since 1995, carbon fiber reinforced polymers (CFRP) have been applied to strengthen concrete decks of a troubled post-tensioned garage in Atlanta, Georgia – first as a prototype and recently on a larger scale. During the construction of the garage, design deficiencies were found. A remedial repair, involving heavily-reinforced, 3-in. thick gunite (shotcrete) beams, applied to the underside of the slab between drop panels in the E-W direction, was immediately installed in 1984. Since then, delamination of gunite beams and other structural problems repeatedly occurred. Epoxy injection and other limited repairs were done over the years. Due to the growing delamination concerns, confirmed with non-destructive impact-echo testing, and due to a structural analysis that showed additional, original design deficiencies, field testing, including load tests and a limited 5-year prototype strengthening program with CFRP, began. The first phase of recent CFRP repairs included a load test program to study the strength and stiffness performance of the existing typical slab spans, including the effects of gunite beams, the loss of gunite beams due to delamination, and the CFRP-strengthening of spans. The tests showed that the CFRP replacement of delaminated gunite beams is warranted and beneficial. Further monitoring of the performance of gunite beams is required, and additional CFRP strengthening will be done periodically. In addition, structural deficiencies of the typical secondlevel end bays were repaired using supplemental steel framing supports.