UHPFRC precast slabs and field-cast joint of the Isabey-Darnley pedestrian bridge

A cast-in-place reinforced concrete footbridge built in 1967 suffering from extensive concrete spalling and rebar corrosion needed to be replaced. The use of a steel Pony-Warren truss combined with thin precast UHPFRC slabs linked by short UHPFRC field-cast joints was selected to build an innovative, durable and aesthetic footbridge minimizing impact on traffic during construction. Material rationalization allowed respective reductions of 64 % and 91 % of concrete and rebar volumes in the slab in comparison to a conventional reinforced concrete slab. The design process was completed with non-linear finite element calculations to obtain an adequate behaviour of the UHPFRC slabs and joints at service and ultimate limit states. A full size proof specimen was then tested under positive bending moment and confirmed being adequate and fulfilling all the design specifications. Construction of the precast slab was successful and required less time than a conventional slab. The long-term performance provided by the UHPFRC slab will be followed up in the next decades.