Application of externally post-tensioned FRP bars for strengthening reinforced concrete members

The volume and weight of heavy vehicles using national road networks has been increasing over the last few decades. At the same time, more than half of the bridges around the world are over forty years old and deterioration of the existing bridges due to increasing traffic loads, adverse environmental conditions, fatigue and structural aging is becoming a major problem. Consequently, restoring and increasing the capacity of bridges and extending their serviceable life by using cost-effective strengthening techniques which ensure minimal traffic disruption, will be of vital importance for protecting the transport system. External post-tensioning is one of the best methods for rehabilitation of the reinforced concrete members owing to speed of construction and minimal disruption to traffic load. However, less attention has been paid to application of external post-tensioning for strengthening reinforced concrete bridge pier. Accordingly, in this paper the application of external posttensioning for strengthening reinforced concrete members is explored. In particular, a detailed nonlinear finite element model is developed and the feasibility of using post-tensioned FRP bars for strengthening a reinforced concrete beam is assessed. To evaluate the efficiency of this system, the results are compared to another finite element model, simulating RC beams strengthened with externally bonded FRP sheets. The flexural and shear strength enhancement achieved by these systems of external post-tensioning is calculated. For the case considered in this paper, application of external post-tensioning can increase the ultimate loading capacity of member by 60% depending on magnitude of post-tensioning forces.