Various Frp Strengthening Techniques for Retrofitting Concrete Structures

The need for repair and strengthening of deteriorated, damaged and substandard infrastructures has become an important challenge worldwide. The demand for increasingly heavier truck loads is forcing bridge owners to upgrade existing structures. In response to the growing need for concrete repair and rehabilitation, an experimental program was conducted to investigate the feasibility of using different strengthening techniques as well as different types of FRP in strengthening concrete members. Three half-scale models of a prestressed concrete bridge were constructed and tested to failure. Five different strengthening techniques were investigated including near surface mounted Leadline bars, C-BAR CFRP bars, CFRP strips as well as externally bonded CFRP sheets and strips. The dimensions of the specimens are 8.5 x 1.2 x 0.4 meters and consisted of one simple span and two overhanging cantilevers. Cost-effectiveness of each of the strengthening techniques considered in this study is presented. To evaluate bond characteristics of the most efficient techniques, a total of 24 concrete beams were constructed and tested under monotonic static loading. Design guidelines for the development length of near surface mounted CFRP bars, strips and externally bonded CFRP sheets used in strengthening concrete beams are proposed. Ultimate capacity as well as failure mechanism of concrete beams strengthened with various FRP techniques are presented.