Mutiple Criteria Decision-Making in the Design of Innovative Lock Walls for Barge Impact: Phase 2, Implementation of Methodologies

The objective of this research is to develop and implement a methodology for multiple-criteria tradeoff analysis supportive of lock wall design subject to extreme events. The work is the first effort of the U.S. Army Corps of Engineers (USACE) to perform tradeoff analysis for lock wall design and to consider very rare and severe damages such as barge impacts and earthquakes.

In designing lock walls, engineers consider different levels of the extreme events for which to design (e.g., a 50-, 100-, or 500-year return period event). In the past, lock walls may have been designed for the conservative and extreme scenario. Looking at tradeoffs among design alternatives may reasonably lower costs without sacrificing significant performance.

Several criteria or metrics are identified for considering tradeoffs among different designs, including construction cost, the ratio of repair cost to reconstruction cost, repair cost, time to recover, and cost to industry. These metrics reflect the degree of severity of a barge impact or earthquake. In the methodology, three scenarios each of possible barge impacts or earthquakes are selected by a lock wall designer for evaluating the alternatives. By studying the metrics, adecision-maker can see the tradeoffs among different designs.

Graphs with the cost of alternative on the vertical axis and the value of a risk metric (e.g., repair cost) on the horizontal axis show the tradeoffs among the alternatives under the extreme event scenarios. A software workbook is developed for the methodology. The implemented methodology is tested using a realistic design situation, making use of data from actual lock projects. Sensitivity analysis is performed to assess the robustness of the model results.