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Introduction: Extending the Design Life of Structurally Deficient Steel and Composite Bridges

In many economies around the world, steel and composite bridges are at the core of the increasingly aging infrastructure problem. Many have been rated either too old with little structural redundancy or simply structurally deficient and unfit for use. Some may also have been seriously damaged by environmental loads. Faced with escalating traffic demand related to both load intensity and frequency, and increasingly aggressive environmental conditions, there is an urgent need for appropriate, innovative and cost-effective engineering solutions for the rehabilitation and strengthening of deficient bridges. These solutions must facilitate rapid construction to minimize downtime, while increasing traffic load capacity. This conglomerate of structural, economic, environmental and social constraints presents a complex design challenge to bridge engineers and may lead to the development of ad-hoc solutions to strengthen and extend the design life of existing bridges. The dissemination of research results and practical technical experience would lead to the development of coordinated and sustainable retrofit techniques.