Development of CFS Jacketing Retrofit Method for Rectangular High Strength Concrete Columns by Cross Sectional Shape Modification

Abstract

Numerous past studies have shown that safety and serviceability of many concrete infrastructures and buildings built in 1970's have far less strength capacities than their original intended design capacities, thereby requiring repair and strengthening. Currently, aged concrete structures are being repaired using various methods developed in the past. Unfortunately, these methods do not consider the specific conditions that these members are under, but they merely attach repairing materials on the external surface for random strength improvements. Therefore, in order to improve repair and strengthening methods by considering composite behavior between repairing material and structural member, enhanced construction methodologies are needed. Also, the enhanced repairing and strengthening methods must be able to be implemented on structural members constructed using high performance concrete to meet the present construction demand of building mammoth structures. Therefore, in this study, a repairing and strengthening method for retrofitting high strength concrete (HSC) columns that can effectively improve column performance is developed. A square HSC column's cross-sectional shape is converted to an octagonal shape by attaching precast members on the surface of the column. Then, the octagonal column surface is surface wrapped using Carbon Fiber Sheets (CFS). The method allows maximum usage of confinement effect from externally jacketing CFS to improve strength and ductility of repaired HSC columns. The research results are discussed in detail.