Theoretical prediction of age dependent crack widths in r/c bridge girders for sustainable asset management

Abstract

This paper discusses the viability of using theoretical crack prediction models as a means of identifying the most appropriate age for maintenance intervention. Usually bridge asset owners rely heavily on superficial observations, especially in early ages, 20-30 years, of a bridge. Visual inspection, a qualitative and subjective approach, is predominantly used as a prime method for bridge condition monitoring by the bridge asset owners. Desired outcomes of qualitative assessment have the limitations of providing satisfactory results and lead to failure in function and safety. Reinforced concrete is a live material which cracks due to shrinkage, creep and flexural stresses. Shrinkage cracks are dominant over the first few years, whereas the flexural and creep cracking, resulting from sustained and periodic loading, can continue whole of life. Depths and widths of these cracks, when reaching a critical level, encourage elements of corrosion at play. The system may enter a vicious-cycle of stiffness and strength degradation, without timely intervention. This paper investigates and proposes a methodology in theoretically predicting most appropriate time of intervention. Authors propose this methodology as a supplement to traditional practice of visual inspection for more informed decision making. It equips bridge owners with greater insight to what cannot be physically perceived by the human eye and could help decision-making to be more objective and cost effective. Research work presented in this paper is, in application, more relevant in reviewing existing bridge maintenance processes adopted by local, regional, state or national levels of governance. Methodology is demonstrated using time-series behaviour of a rectangular R/C section simulating a bridge girder. Post corrosion time series behaviour is not included within the scope of this discussion.