Evaluating Deteriorated Marine Structures with Limited Remaining Service Life

Abstract: Evaluation of remaining service life of marine structures has often been focused on concrete structures and how migration of chlorides through concrete eventually initiates corrosion in the embedded reinforcing steel, with subsequent damage to the surrounding concrete. Although deterioration of timber structures is often more visually apparent, extended rot and marine borer activity can often be hidden below the surface of seemingly sound structural members. A good understanding of how much timber deteriorates over time can therefore be very useful in predicting future repairs for a waterfront structure. This can for instance be used for capital planning purposes or decision making with respect to upgrades.

When an understanding of the expected deterioration rate is known, this can also be utilized in situations where an owner faces a situation where a decision needs to be made regarding repairs before an upgrade is made. On one side, the structure needs to be safe, but on the other side, the owner does not need to spend unnecessary money before an upgrade is made. This paper will therefore explore a methodology where known and expected deterioration is combined with calculations of acceptable capacities for a reduced remaining service life. Two case studies will be presented where this methodology was utilized in the decision-making process for repairs combined with replacement of the structures.

How does this project / topic contribute to the advancement of the industry and profession?: It provides a methodology for determining acceptable damage for structures that will be replaced in the near future. It will also give examples of typical deterioration rates of timber piles in salt water.

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: The authors are not aware of this methodology being applied to timber structures before.

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: The greatest challenge was to find enough data for meaningful projections of deterioration rates.

Who is the target audience for this paper?: The target audience of this paper includes both owners and engineers who make decisions regarding repairs of timber structures.