IIW White Paper

9 Needs and challenges of major industry sectors for future applications

Bridges are classified as redundant and non-redundant. With non-redundant bridges, certain elements are deemed “fracture critical”. If fracture critical elements fail, the entire bridge is expected to collapse. The foregoing challenge of inspection is all the more critical for such structures. Amajor challenge to steel buildings is corrosion. Bridges havebeenpainted for years, but painting is expensive, not only for a new structure, but as an ongoing maintenance cost of existing structures. The greatest cost is when severe corrosion is not detected and members fail due to loss of section. Weathering steel has been used successfully in some applications although it offers no advantage in situations involving salt spray. Hot dipped galvanised members have also been used, but the economics are typically unacceptable. Thermal Spraying with corrosion resistant materials is yet another technically viable option that lacks cost effectiveness. New materials with better corrosion resistance or more viable coating methods will result in better bridge systems and will expand the role for welded metallic structures. The development and refinement of fatigue enhancement methods, both for existing structures as well as new structures is an ongoing opportunity for the bridge segment. For more widespread application of such technologies, the degree of enhancement must be carefully defined, and the means of application must be safe, practical, repeatable and verifiable. Breakthrough designs are needed to make steel bridge construction more cost effective with concrete alternatives. Such advancements will likely make use of other than I-shaped girders. Innovative composite designs with concrete filled tubes for example should be pursued. As the strength of steel used is increased, welding-related problems such as fabrication cracking and in service fatigue will be of greater concern. Fracturemechanics analysis suggests that asmaterial toughness levels are increased, thereexists thepotential for increases in allowable stresses, or relaxed inspection and acceptance criteria. Accurate characterisation of material properties, particularly for multiple pass welds and for heat affected zones, as well as accurate models for prediction of fatigue cracking may reduce the frequency for ongoing in-service of bridges. Bridges are essential to the transportation of goods and people. No form of surface transportation can survive without them. Bridge needs vary from country to country (for example in financing, planning, method of construction, and maintenance of bridges), but all nations have strategic issues in common. Rather than routine engineering details for designing, construction and maintenance of bridges, focus on the strategic goal of what one may call “transportation solutions” that are vital and significant but more importantly that are influenced by the bridge industry and particularly relate to welded steel bridges and welded products, is dealt with here. To advance integrated bridge technology to meet transportation needs for planning for long lasting bridges, several factors must be considered: The impact of growing population. The need to travel faster but safely and efficiently. A greater emphasis on protecting the environment. Information that is available to practicing bridge engineers today through research and technology developments. New avenues and values because of expedient communication and globalisation. These factors, in addition to the routine considerations for cost effective bridges using conventional standards for design, construction and maintenance, are significant in meeting challenging demands of the communities that must be considered and supported by the government, bridge industry and academia in a coordinated manner to meet today’s demands on bridges.

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Through Optimum Use and Innovation of Welding and Joining Technologies

Improving Global Quality of Life