An International Perspective: Widening Existing Bridges with Orthotropic Steel Deck Panels

Rehabilitation of existing bridges is an extremely complex and challenging aspect of bridge engineering. Widening of existing bridges without interruption of traffic is even more complex. The I-35W tragedy demonstrates the danger to the public during bridge renovation. The focus of this discussion is conceptual solutions, an overview of the fundamental issues or choices in practicable widenings. The USA Federal Highway Administration (FHWA) is promoting the term Accelerated Bridge Construction "ABC" for economical efficient construction methods with more prefabrication and less site work. The slogan is "Get-In, Get Out and Stay out". The technique of orthotropic steel deck panel replacement is the innovative ABC technique for widening existing bridges. The goal of any ABC method is to minimize the effects on other stakeholders and achieve the FHWA's desired 100-year service life for a new bridge. Typical stakeholders are commuters, shipping companies, the environment, railroads, etc. FHWA's goal is (a) to minimize traffic delays while erecting a bridge, (b) to minimize river commerce and harbor shipping delays while erecting a bridge over navigable bodies of water, and (c) to minimize environmental impacts while erecting a bridge. Some of the featured existing bridges were not physically widened, but their traffic flow was increased via renovation of the existing deck system with orthotropic steel deck panels. Bridges built and in operation with steel orthotropic steel decks in North America are very rare; about 100–120 are orthotropic while there are 650 000 bridges in the USA alone. Many American engineers feel that welded orthotropic steel decks are too challenging to design and offer little benefit to the owners of bridges. The FHWA is currently in the process of creating a new orthotropic bridge manual to replace the 1963 Orthotropic Bridge Manual authored by Roman Wolchuk and published by the American Institute of Steel Construction (AISC). There is lack of enthusiasm in the USA for orthotropic bridges that existed in the 1960s among the US steel industry and affiliated trade associates. Another design challenge is the lack of orthotropic bridge design software. Although US software has many excellent specialized bridge design programs, none is specific for orthotropic bridges based on the American Association of State Highway and Transportation Officials (AASHTO) Bridge codes. Ironically USA orthotropic experts are involved in the actual design or review of designs of bridges located in other countries. Featured widened bridges from around the world include the Cologne-Rodenkirchen Bridge of Germany (1994); Wakato Ohashi Suspension of Japan, (1999); Angus L. Macdonald Bridge (1999); Tamar Suspension Bridge, UK (2001)), and the Songsu Bridge, Korea (2002). A comprehensive reference list is provided to assist in obtaining more detailed design and fabrication information about renovated bridges with orthotropic steel decks. A comprehensive table of projects located around the world is also included.