WP5 - Multi-objective performance-based optimization of maintenance strategies and repair or strengthening interventions

Main researcher: ir. Karel Van Den Hende

Affiliation: Ghent University

Title PhD dissertation: Reliability-based Assessment of Corroding Concrete Structures and Optimization of Interventions in View of Service Life Extension

Supervisors: Prof. dr. ir. Robby Caspeele, prof. dr. ir. Stijn Matthys, prof. dr. ir. Geert Lombaert

References: link

Work package description

In order to exploit the available resources as efficiently as possible, a consistent way to evaluate existing structures and propose the most suitable maintenance, repair or strengthening strategy is needed. Therefore, this workpackage focusses on the decision making and optimization of structural interventions based on all relevant information from monitoring, inspection and testing. The optimization is performed considering different performance objectives related to durability considerations, target safety levels and budgetary constraints.
In order to make decisions, a minimal life-cycle based cost optimization procedure will be used. This total life-cycle cost includes besides the construction cost and direct or indirect costs associated with stuctural failure, also the costs of inspection and monitoring, and the costs associated with the repair or strengthening strategy. This life-cycle cost will be used to objectively optimise sructural interventions including the type of intervention, the amount of interventions throughout the structures lifetime and the quality of the inspection.

research results

Chloride ingress is a common issue in concrete structures that can result in reinforcement corrosion. In this work, analytical approaches are developed to predict the influence of different repair interventions on the chloride ingress prediction. This enables the assessment of each repair method in a probabilistic framework with limited computational resources.

In order to evaluate existing concrete structures, different levels of assessment have been developed. In the first level, the need for a preventive intervention is based on the prediction of the probability of depassivation (typically considered the starting point of corrosion). In the fourth level, a full probabilistic evaluation is executed of the ultimate limit state and the reliability level is determined explicitly and compared to a target value. The second and third level provide a good balance between accuracy and ease of application.

The third and fourth level require an evaluation of the ultimate limit state over time. Therefore, chloride ingress prediction models are combined with structural models that incorporate the effect of corrosion in the load-bearing capacity of a structure.

The application of interventions can be optimized based on the minimization of the total life-cycle cost. An approach is developed where the corrosion-induced effects are predicted and linked to a certain cost. Based on this analysis, the effect of a preventive intervention can be quantified and its applicability can be evaluated in an objective manner.

main objectives

This workpackage aims for the following Deliverables (D) and Milestones (M):

  • D5.1 – Algorithm for the cost-optimization of maintenance and interventions
  • D5.2 – Report on performance verification framework and suitable target performance levels
  • M5.1 – Performance verification framework available
  • M5.2 – Basic life-cycle cost optimization procedure available (M24)