Investigation into reliability of existing Infrastructure and the calibration and capacity to use FRP for retrofit repairs on degraded reinforced conc

Project title Investigation into reliability of existing Infrastructure and the calibration and capacity to use FRP for retrofit repairs on degraded reinforced concrete structures

Existing infrastructure in modern countries is becoming an increasing risk to society and asset owners as engineered structures reach the end of their designed periods (around 50 years). Changes of use, increased traffic loading, material degradation in addition to variations in code designs result is many structures being deemed as unsafe. Furthermore, in developing countries, the infrastructure in place can have no or limited design documentation available to aid inspection procedures, resulting in increased uncertainty in the decision making process. Investigation and inspection procedures from past and present also provide subjective data that can vary greatly between nations, making it difficult to improve any assessment models of structures without detailed further analysis from expensive testing methods (Destructive and indirect testing methods) whilst monitoring in the majority of existing structures is limited or non-existent.
As a result, the need to assess existing structures due to the uncertainties in the current performance, limited data collected on site, and the large number of reinforced or pre-stressed concrete small to medium span bridges make these structures particularly critical.
Furthermore, where an assessment dictates that repairs, retrofitting or rehabilitation is necessary to return the structure to a reliability state above the required criterion, the current design codes are inapplicable. In fact, design partial factors and characteristic parameters are defined for new structures which can significantly differ from those observed in existing structures. This can be a result of improved consistency of material production, assumptions in commonly applied structural models, and loads designed for fifty year expected life-times compared to that of a structure with a remaining life of less than 10 years. Combining this with the uncertainties in existing structures discussed prior, the only method with which structures can be repaired is by setting very conservative assumptions at large costs or by applying reliability techniques for the materials and elements in the current structure based on their current state and design procedures at the time of construction, and assessing their combination with the anticipated possible repair methods in a series of probabilistic structural models. This should enable asset owners to identify appropriate courses of action to provide sufficient reliability at minimal costs, whether repairs, demolition and replacement are the most viable options.
The methods of rehabilitation that can be applied to structures is therefore of interest with many repairs performed at significant costs such as external post-tensioning of bridge decks. Meanwhile, the potential of FRP (Fibre Reinforced Polymers) applied to the exterior of structures with their low mass, high-tensile strength and the ability to apply them over a range of surface shapes, make them an interesting alternative to more traditional methods like steel plates. However, the lack of standards makes the development of design codes for strengthening elements explicitly for damaged or deteriorated existing structures critical
Objective:
Develop an assessment and design probabilistic tool for deteriorated concrete bridges
As a result, the objective of this PhD is to develop an assessment and design probabilistic tool for deteriorated concrete bridges investigated the reliability and applicability of FRP as repair methods providing groundwork for a simple solution which can be applied in 'repair' design codes for the future.