Concerns about underwater bridge substructures have tended to focus on scour. Structural deterioration, however, is also important. Because most substructures are concrete, rates of decay are of particular interest. The purpose of this paper is to discuss what has been learned about substructure deterioration. Specific issues addressed include: how substructure material deterioration rates vary by material and structural type, how waterway deterioration rates reflect structural configuration, the importance of designing repairs to avoid future problems, and how to use deterioration rates to select the best interval for underwater inspections. Examples are used to illustrate the lessons learned from underwater inspections.

The reconstruction of the I-15 corridor through the heart of Salt Lake City, Utah, is a massive $1.6 billion project encompassing 27 km (17 mi) of freeway. The project scope involves building 144 new bridges over four and a half years. To expedite completion of construction, the Utah Department of Transportation (UDOT) selected the design-build delivery process. The I-15 Reconstruction project represents one of the first attempts to implement a displacement-based seismic criteria for a major highway project. These comprehensive seismic criteria addressed modeling, analysis and design procedures. They also provided guidance regarding the selection of different materials and seismic strategies. The multi-faceted approach addressed all aspects of design including constructibility.

Incremental bridge launching is a competitive construction method in a wide range of spans and bridge dimensions. Its competitiveness also derives from the repetitiveness of operations, which can be further enhanced by optimizing the deck segmentation according to the industrialization possibilities of the site and the criteria illustrated in the article. Particular cases such as precast segmental incremental launching and superstructures launched onto arches are also discussed.

Tren Urbano project is a mass transit rail system located in San Juan, Puerto Rico. The construction cost for this project is approximately $1.7 billion (U.S.). Tren Urbano construction phase began in the summer of 1997 with four out of seven design/build contracts awarded at that time. The mass transit system is 17.2 km (10.

To achieve a sustainable level of development in the next century, it is apparent that funding for bridge repair and maintenance will have to be increased substantially. Recognizing the funding constraints that exist due to the other deficient components of the infrastructure, it is apparent that the effectiveness or return on the available funding needs to be maximized. This can only be accomplished by increasing the minimum service life, or useful life, to 100 or 120 years and selecting structures on the basis of reasonable life-cycle cost analyses. For major bridges in urban environments, the minimum service life should probably not be less than 150 years.