Shear Capacity Assessment of an Existing Prestressed Concrete Bridge with Corrosion Damage
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The thesis contains shear capacity calculations of the structural beams in The Hulvågen Bridge, a concrete element bridge consisting of prefabricated and pre-tensioned beams with a continuous cast-in-place bridge deck. The calculations have been performed using both NS 3473:1977 (valid when the bridge was designed) and Eurocode 2 (valid today). It is found that the capacity is more than sufficient for the three main shear failure mechanisms (diagonal tension, compressive shear and anchorage failure). The shear resistance in the interface between the beams and bridge deck is almost entirely utilized. Due to its location at the Norwegian coastline, the bridge is exposed to extremely aggressive marine environment. Low requirements to concrete cover when the bridge was designed in 1987 makes it prone to chloride induced reinforcement corrosion. Observations from an excursion to the bridge in May 2017 indicates leakage of sea water through the bridge deck, while no visual signs of corrosion in the NIB beams have been found. The effect that the various consequences of reinforcement corrosion can have on the shear capacity of the beam has been investigated. Based on the lack of observed corrosion damage, it can be concluded that neither of the three main shear failure mechanisms are likely to occur at this time. However, the prestressing steel in particular may corrode without visible signs at the concrete surface, and further examinations of chloride content in relevant parts of the bridge should therefore be performed. Leakage of sea water through the bridge deck may result in corrosion of the reinforcement crossing the interface, which may reduce the shear resistance at the interface. It is recommended to further examine the damages to the bridge deck and interface, and perform repairs where necessary.