ICE - Institution of Civil Engineers - Virtual Library

The use of Eurocodes on real projects in the UK highways sector is nearing reality. National Annexes for all the parts required for bridge design are nearing completion and should be ready by the end of 2007. The Highways Agency and British Standards Institution (BSI) committees are completing production of BSI Published Documents to give non-contradictory complementary information to help with the use of the Eurocodes and a variety of organisations are producing design guides. Despite the cultural and technical changes that the Eurocodes bring, pilot studies have shown that designers adapt remarkably quickly. There are also incentives to embrace the Eurocodes. The less prescriptive approach and more up-to-date rules provide the user with greater scope for innovation and economy. This paper identifies the various areas in steel and concrete design where there are technical differences between the new Eurocodes and BS 5400 and also where the new rules lead to the potential for greater structural economy.

At White City in west London, the Hammersmith and City line runs on a high-level brick arch viaduct that crosses over both Wood Lane and the eastbound Central line. As part of the White City development, a section of this viaduct was removed and replaced with a new twin-track highly skewed bridge. This comprised a half-through bridge formed from three principal steel girders with connecting cross-beams and concrete infill. The deck was built off line, then slid into position during a four-day possession of the Hammersmith and City line, requiring part of the existing viaduct to be demolished; the Central line below remained open throughout. The piled substructure was constructed within the constraints of the existing viaduct arches. The existing early 1930s steel bridge deck over Wood Lane was strengthened in advance to provide new bearing positions. During the possession it was truncated by 2 m and supported on new piers.

This paper summarises the results obtained from non-linear finite-element analysis (NLFEA) of a series of reinforced-concrete one-way slabs with various boundary conditions representative of a bridge deck slab strip in which compressive membrane action governs the structural behaviour. The application of NLFEA for the optimum analysis and design of in-plane restrained concrete slabs is explored. An accurate material model and various equation solution methods were assessed to find a suitable finite-element method for the analysis of concrete slabs in which arching action occurs. Finally, the results from the NLFEA are compared and validated with those from various experimental test data. Significantly, the numerical analysis was able to model the arching action that occurred as a result of external in-plane restraint at the supports and which enhanced the ultimate strength of the slab. The NLFEA gave excellent predictions for the ultimate load-carrying capacity and far more accurate predictions than those obtained using standard flexural or elastic theory.

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 23°. 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.

This technical note outlines the concept of double composite action. It summarises the potential advantages of a double composite steel–concrete structure over the more common steel–concrete composite construction, particularly for continuous structures. A comparative study of three bridge forms with and without double composite action is outlined and the reduction in steel tonnage for the double composite type of each form is estimated.