Bridges

Two existing bridges located along the M80 Ring Road were upgraded as part of the M80 Upgrade between Sydney Road and Edgars Road. An additional lane was added to each carriageway without widening either bridge. Both bridges were constructed with super-T girders in 1998 and preliminary assessments identified that strengthening works were required to meet current requirements by state authorities and Australian Standard AS5100.8:2017. A detailed assessment carried out identified that the girders were deficient in shear. Carbon Fibre Reinforced Polymer (CFRP) wrap was adopted to provide additional shear capacity. However, the latest update of VicRoads Bridge Technical Note BTN 005 - FRP for Strengthening of Bridge Structures (2018) limits the use of FRP composites to concrete with compressive strengths not exceeding 60 MPa and requires the design life of FRP strengthening to at least equal the remaining life of the strengthened structure. Both bridges failed to satisfy these requirements. The relevant authorities were engaged to discuss the strengthening options and details. This paper discusses the development and optimisation of the shear strengthening design with CFRP wrap, and the challenges encountered in developing a design that achieved the intent of the standards in collaboration with the client and relevant authorities.