Life-Cycle Analysis of Corroding Sheet Pile Structures for a Lock and Dam

摘要

This report documents research conducted at the Thomas J. O'Brien Lock and Dam on the Illinois Waterway in Chicago to assess its structural condition,provide a structral quality-vs.-time prognosis, and develop an appropriate corrosion mitigation program. Although there is an abundance of design information for steel sheet pile structural design, including a program in the Corps of Engineers' computer-aided structural engineering (CASE) library, these programs are for new construction and do not consider the consequences of corrosion damage. To realistically determine the structural quality of the O'Brien Lock and to develop a credible projection of its usable life, a specialized analysis had to be developed for this particular structure; however, the analysis had to be general enough for use in other similar structures throughout the Corps. Detailed field and laboratory analyses indicated that there is a large safety factor in the structure and that 0.25 in. of corrosion can be tolerated anywhere without catastrophic results. However, corrosion that exceeds 0.25 in. in highly stressed areas could cause catastrophic results. The extreme value of corrosion calculated for the lock and dam is 0.0024 in. per year, which means that 83 years of corrosion must occur to achieve that 0.25 in. value. It was found that cathodic protection could be used successfully at this structure to prevent additional corrosion damage. A deep well anode system is ideally suited for this project.