ICE - Institution of Civil Engineers - Virtual Library

• Introduction

• End anchorage

• Replacement procedure

• Articulation

• Stub columns

• Stub column replacement

Maintenance of bridge structures has undergone rapid development over recent decades. New deterioration mechanisms have become evident as bridge stocks age, requiring new testing and remedial techniques. Bridges assets are of critical value to the economy, and demand maintenance with the minimum disruption to the flow of traffic. This chapter considers the techniques required for particular materials – concrete, metal and masonry. These include methods of repair and strengthening, with particular reference to those which have undergone rapid recent development, such as plate bonding.

Contents

• Introduction 695

• Repair and strengthening of concrete structures 695

• Repair and strengthening of metal structures 701

• Repair and strengthening of masonry structures 707

• Replacement of structures 719

• References 727

• Further reading 728

• 15.1 Objective

• 15.2 Routine maintenance

• 15.3 Protection, repair and rehabilitation or replacement

This short paper describes the replacement of a failed timber footbridge in Cumbernauld, North Lanarkshire, UK. The significance of the paper is its recognition of the importance of providing and maintaining sustainable walking and cycling links within an urban environment. This is demonstrated in the speed of delivery of the project and its minimisation of disruption to the users, together with the use of sustainable-source, low-maintenance materials. It emphasises the significance of sustainable development in urban regeneration, and the need to develop the existing pattern of usage of walkways and cycleways, thereby encouraging healthy alternative means of transport, and avoiding the promotion of a culture where short journeys are made by car.

The Forth replacement crossing will be built across the Firth of Forth in Scotland to maintain and enhance a vital transport link in the country. The wide estuary will be crossed by a pair of 650 m main spans over the two navigation channels, with crossing stay cables employed to stabilise the central tower – a unique design feature for a bridge of this scale. The project aims to provide a fitting twenty-first century icon standing alongside existing nineteenth and twentieth century grade A listed bridges. A statutory consultation process is currently under way, with competitive dialogue taking place throughout 2010. Construction will commence in 2011 and the bridge is expected to be completed in 2016.

Heath Town footbridge was constructed in 1999–2000 to replace an existing concrete bridge that was in poor condition and had failed its assessment. The existing bridge had performed two functions, one as a footbridge over an urban dual carriageway and service road between high-level walkways in Heath Town, Wolverhampton, the other being to carry district heating pipes from the boiler house on one side of the road to flats and other premises on the other side of the road. The new bridge is a parabolic arch in steel, on piled foundations. It was originally designed to carry the district heating pipes in the same way as the previous one, but permission was given to bury these permanently beneath the dual carriageway, which prompted a redesign of the deck, making it simpler in detail.

The Saltire Society Design Commendation for the New Daer Viaduct reads ‘It will become the benchmark to which other similar schemes are prepared'. A two-span bridge carrying the West Coast main line over the River Clyde was replaced by a single river span. All construction of the new substructure and superstructure and jacking of the superstructure into its permanent position was carried out below the existing bridge with no disruptive track possession. Only one 42 h possession was utilised to remove the old superstructure and the original central pier and to install minor precast infill units. The superstructure comprised two steel edge through girders supporting a transverse steel composite deck. The edge girders were aligned to pass the ends of the original central pier. When the superstructure was jacked up, the concrete robust kerb and edge girders moved up outboard of the original bridge edge girders. Thus, prior to the possession, the superstructure had all been built except for the portion occupied by the original pier. Following removal of the pier, this portion was completed with a precast concrete unit.

• Introduction

• Propping

• Brackets

• Model

• Removal

• Reconcreting

• Creep and shrinkage

• Dejacking

• Problem

• Wider columns

• Summary

• The problem

• The objective

• Safety and reliability

• The options

• Deck supports

• Beam to one side

• Beam under

• Conclusion

• Temporary steelwork supports

• Modifications to the existing structure

• Bracings

• Bearings

• Shock transmission units

• Temporary guides to bearings

• Dynamic behaviour

• Viaduct articulation

• Erection and installation of supports

• Sand lorry trials

• Demolition and reconstruction

• Dejacking

• Further applications

• Simplifications

• Foundations

• Other modifications

• Conclusions