Flexural strengthening of precast reinforced concrete bridge girders using bonded carbon fibre reinforced polymer strips or external post-tensioning

Strengthening of reinforced concrete bridge girders has become a major concern. Many reinforced concrete highway bridges were constructed in Canada using precast reinforced concrete girders, and currently many of them need rehabilitation. Thus, two techniques for flexural strengthening of precast reinforced concrete bridge girders (HC-type) were investigated experimentally. The first technique involved bonding carbon fibre reinforced polymer (CFRP) strips to the soffits of the girders. The second technique was classical external post-tensioning with steel bars. A simple, yet innovative method was developed for applying the external prestressing to these girders. The experimental investigation was performed on full-scale girders from a dismantled bridge in Alberta (Canada). Outcomes of the experimental investigation led to the conclusion that classical methods of flexural strengthening (e.g., external prestressing) should not be completely disregarded. Also, an additional mode of failure needs to be added to currently available prediction models for estimating the gain in flexural strength of reinforced concrete girders retrofitted using bonded CFRP strips.Key words: bridges, CFRP, flexure strengthening, precast girders, post tension, prestressing, rehabilitation.