On a bridge structure, the most vulnerable components to the routine application of deicing salts, repeated freeze-thaw cycles, and other damaging effects are bridge decks and elements of substructure under bridge joints. They are constantly experiencing observable deterioration. The concern arose in the 1970s when bridge decks designed for an expected service life of 30 to 50 years began to deteriorate after only 20 years in service. In addition to bridge decks, their supporting members, such as abutment walls, piers, and exposed piles, are also subject to deterioration, even more so those in coastal environments. Based on years of experience, Maryland has gained a certain degree of knowledge on bridge decks, but not enough on bridge substructures. Two questions must always be answered when rehabilitation work is required on a bridge:
(1) How can the condition of the substructure be assessed?
(2) Based on the assessment, can the bridge substructure unit be rehabilitated or must it be replaced?
Having accurate assessment information is essential, since the cost associated with replacing every bridge substructure in doubt is extremely high. Therefore, typical damage mechanisms and test methods, including destructive and non-destructive testing, for determining the extent of damage due to chlorides need to be identified and correlations between the two be reported.
Research Objectives- The objective of this proposal is to identify typical damage mechanisms and test methods, including destructive and non-destructive testing, for determining the extent of damage on substructure elements and to develop correlations between testing results and substructure condition for MDSHA consideration on whether rehabilitation or replacement of a given bridge substructure element is most appropriate.
Implementation- The proposal is divided into four tasks:
- Task 1 Collect and Study the State-of-the-Art and State-of-the-Practice Methods Throughout the Bridge Community including Specifically Maryland Bridges with Substructures Replaced or Rehabilitated due to Material Problems
- Task 2 Field investigation of replaced / rehabilitated substructure units and potentially problematic substructure elements
- Task 3 Develop correlations between testing results and substructure condition for SHA consideration in determining which substructure units can be rehabilitated and which must be replaced.
- Task 4 Summary and conclusions