Strengthening of Irwell Valley Bridge, UK.

The Irwell Valley Bridge in the UK comprises seven steel- concrete composite box girders with a simply supported span of 60$96 m at a skew of 238. It carries the M60 motorway across the River Irwell adjacent to junction 16 and was constructed in 1970. Structural assessment highlighted deficiencies in the shear studs connecting the concrete deck slabs to the steel boxes, steel diaphragms and end cross-bracing. The first of these three deficiencies was addressed through a departure from standards, while the other two deficiencies required strengthening and modification. A means of jacking the boxes for future bearing replacement also needed to be provided. This paper identifies the various ways in which a cost-efficient and buildable design was produced for strengthening of the diaphragms and how detailing problems specific to strengthening a steel box with restricted access were overcome. Key to the project was the need to minimise disruption to the highway network and to work within tight programme constraints imposed by the hibernation and roosting requirements of bat colonies living within the bridge. The motorway was therefore kept open during jacking operations and multiple boxes were strengthened simultaneously. Due to the complexity of the construction sequence for the strengthening work, a virtual reality model of the bridge and all stages of strengthening was set up and distributed to all parties. The benefits of using this model to assist both design and work on site are discussed. [ABSTRACT FROM AUTHOR]