Development of a relationship between external measurements and reinforcement stress

As many countries around the world face an aging infrastructure crisis, there is an increasing need to develop more accurate monitoring and assessment techniques for reinforced concrete structures. One of the challenges associated with assessing existing infrastructure is correlating externally measured parameters such as crack widths and surface strains with reinforcement stresses as this is dependent on a number of variables. The current research investigates how the use of distributed fiber optic sensors to measure reinforcement strain can be correlated with digital image correlation measurements of crack widths to relate external crack width measurements to reinforcement stresses. An initial set of experiments was undertaken involving a series of small-scale beam specimens tested in three-point bending with variable reinforcement properties. Relationships between crack widths and internal reinforcement strains were observed including that both the diameter and number of bars affected the measured maximum strain and crack width. A model that uses measured crack width to estimate reinforcement strain was presented and compared to the experimental results. The model was found to provide accurate estimates of load carrying capacity for a given crack width, however, the model was potentially less accurate when crack widths were used to estimate the experimental reinforcement strains. The need for more experimental data to validate the conclusions of this research was also highlighted.The authors would like to thank the Natural Science and Engineering Research Council of Canada, the Canada Foundation for Innovation, and the Ontario Research Fund for their financial support of this research. The authors would also like to thank Adam Hoag, Jaime Escobar, Neil Porter, and Paul Thrasher for their assistance with the experimental program.This is the author accepted manuscript. The final version is available from SPIE at http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2213474