COST-EFFECTIVE BRIDGE MODIFICATIONS

This paper was presented at the 'Strategic investments in structures' session. As a result of the aging bridge population and increased volumes of traffic, Canadian municipalities have been faced with the thorny issue of bridge upgrading. Many bridges require imporved pedestrian faiclities or safer traffic barriers. Others are suffering from increased axle loads and require deck imporvements. Some bridges are functionally inadequate and need widening. Some of these structures are in good condition, others have deteriorated decks on sound substructure. Few are candidates for complete replacement. Under current budget constraints, ways to utilize the residual life expectancy needed to be found, which required creative solutions to be developed. The author's firm has undertaken many such projects and describe cases of innovative designs that proved constructible, reduced maintenance, and were highly cost-effective. None were 'traditional' solutions to bridge engineering problems. Examples include: concrete deck overlays to strengthen timber deck bridges, deck slabl overlays for timber superstructure replacement, supplementing existing stringers with new members, precast removable shear-connected slabs for timber superstructure replacement, provision of a separate pedestrian structure to permit deck widening and safety improvements, lightweight short-span pedestrian trusses, strengthening weakened abutments by backfilling, and traffic barrier upgrades for aging bridge superstructures. The paper describes the situation prior to the improvement and examines the alternative solutions. The advantages gained by the imporvement and the method of using the residual life expectancy of the structure are described. For the covering abstract of this conference see IRRD number E200820. (A)