Evaluation of H-pile Corrosion Rates for Wisconsin Bridges Located in Aggressive Subsurface Environments

On September 25, 2013, Pier 22 for the Leo Frigo Bridge (B-05-381) near Green Bay, Wisconsin, moved vertically approximately two feet. One of the root causes of the vertical movement was the reduced structural capacity due to the loss of section of the steel H-piles that supported the pier as a result of severe corrosion. The purpose of this research is to evaluate the corrosion rate at a limited number of structures around the State of Wisconsin, which are founded in similar subsurface environments. This work will also provide a frame work for service life prediction of such structures. Wisconsin Department of Transportation’s (WisDOT) Bureau of Structures and Bureau of Technical Services has compiled a list of structures which could have similar subsurface conditions to those encountered at the Leo Frigo Bridge. The objective of this research is to evaluate the potential corrosion rates of the piles at a limited number of specific bridges and to develop guidelines for future investigation procedures for evaluating potential pile corrosion in the project design stage. The efforts here aim to evaluate H-pile corrosion rates for Wisconsin bridges located in aggressive subsurface environments. The obtained information from the literature review, laboratory tests and field investigation will be used to derive the following conclusions: (i) The environments based on corrosion activity of the embedded steel will be ranked. (ii) The best corrosion measurement technique(s) for monitoring the corrosion activity of steel in soil, by comparing the results from the gravimetric test and different electrochemical methods will be determined. (iii) The remained service life of steel specimens in selected environments will be evaluated and determined. (iv) Different corrosion mechanisms (galvanic vs. localized or combined) will be compared and the significance of each mechanism in corrosion of the H-pile in different soil environments will be determined. WisDOT installs H-pile foundations on many structures throughout the state. Through this project, the design assumptions related to the corrosion will be evaluated and confirmed so that estimated design life of these structures will be achieved. Results will also give an indication on corrosion potential of these structures and provide information on what sites/subsurface parameters are important when considering estimating potential pile corrosion. Furthermore, by taking samples of the subsurface environments, it could be possible to estimate the remaining life of the H-pile in that environment. In addition, more reliable and advanced corrosion monitoring program will be developed during this work which enables WisDOT to overcome some current difficulties in estimating the accurate corrosion rate of the H-piles in corrosive environments. The products of the proposed research project will be the correlation between subsurface environments and the corrosion activity of the H-piles throughout the State of Wisconsin. The project reports will include recommendations that will be used by WisDOT personnel as the basis for a comprehensive corrosion policy in design and installation of bridges with H-pile foundations. Based on the laboratory and field studies in this work, a procedure will be established to help WisDOT staff and engineers to optimize the installation and use of H-piles in different environments. Results from this work will be used in each region of the state to refine the corrosion mitigation measures applied to H-piles in that region. With this information, bridge replacement/repair can be scheduled earlier, thus allowing WisDOT to schedule the resources and traffic control well in advance. Results from this study will provide WisDOT with corrosion related recommendations to incorporate into H-pile design in potential aggressive subsurface environments.