Shifting qualitative approach in condition monitoring of bridge assets towards a quantitative approach

Bridges are epitome of civil engineering and social and economic infrastructure. Degradation of bridges is a natural phenomenon and demands timely assessment and maintenance, to be in serviceable condition. In Australia, 60% of aging bridges are believed to be around 60 years old. Aging occurs due to increase in applied loads, surrounding environment, climatic conditions or any natural disaster. In Victoria, a state of Australia, most of aging bridges have experienced three major shifts in applied loads since construction, both in magnitude and configurations. Proposed methodology assesses the effects of these changes on bridge girders, in conjunction with change in material behaviour.

This dissertation also aims to propose a theoretical assessment framework which can be used to support the visual inspection condition data. Visual inspections are performed on regular basis to document the present condition of a bridge asset and considered qualitative, as data is recorded in subjective format. Asset owners use the condition data sets as the primary source of evidence for developing maintenance programs, capital forecasting and identifying the intervention time. This dissertation examines the possibility of theoretically predicting the crack widths, which is regarded as a key measure of degradation, to supplant subjective visual reporting of cracks using theoretical and empirical models. Hypothesis of this research argues and begs the question, as to why the codified and empirical based crack width prediction models, widely used in design practise, cannot be used in condition evaluation and maintenance forecasting over bridge’s life span.

To further strengthen the proposed assessment method, reliability of theoretically established crack widths is instituted using reliability theory. Application of the proposed methodology is verified by assessing four R/C bridges, designed in early 1960s and currently in service.

As an original contribution to the body of knowledge, this dissertation provides an assessment framework for asset owners, which can be implemented for informed decision making and proactive measures. Dissertation also addresses the needs of regional bridge asset management owners who may not have access to structural health monitoring systems. In essence, an asset owner can supplant the qualitative outcomes of visual condition monitoring with statistically treated theoretical outcomes, supplementing each other in providing scientifically justifiable informed decision environment.