Investigation of Effective Parameters on Reliability of RC Bridge Piers Strengthened with FRP Sheets

Fiber Reinforced Polymer (FRP) materials are increasingly used to strengthen and retrofit of RC structures. Their high stiffness and strength-to-weight ratio, resistance to corrosion, and easy handling and installation are making FRP jackets the material of choice in an increasingly large number of seismic retrofitting projects, despite the relatively high material costs.FRP jackets provide lateral confinement to concrete which increases the strength and ductility of piers. Several empirical models are available that predict the compressive strength and the axial strain of confined concrete using FRP sheets. Comparing the models with available empirical data indicates a considerable stage of uncertainty. In this paper this uncertainty is predicted and taken into account in reliability analysis of FRP-confined piers. Based on analytical results, some recommendations are suggested to modify the strength reduction factor for design of confined piers so as to ensure the same level of reliability as for unconfined piers. Also a suggested relationship between the reduction factor and the ratio of confinement for FRP-confined piers in axial compression and axial compression with flexure is proposed. As a final approach, the effectiveness of parameters such as ratio of reinforcement, ratio of live to dead load and ratio of eccentricity have been studied.