Characterization of cracks in bridge beams with welded wire fabric reinforcement using image processing

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Texas Tech University

The Texas Department of Transportation (TxDOT) widely uses prestressed concrete I-beams as bridge girders. The current TxDOT policies allow the substitution of an equal area of Welded Wire Fabric (WWF) for the traditional vertical steel reinforcement. However, TxDOT does not provide details for the WWF substitution.

A research project was conducted to study the behavior of WWF as shear reinforcement m the high shear regions of prestressed concrete beams. The main purpose of the project was to test the anchorage capacity of the WWF bars. As alternatives, a simplified WWF design and an equivalent strength WWF design were also proposed.

Another main objective of this research was the study of the cracks to have a better understanding for the performance of these alternative designs. The crack controlling behaviors of different WWF vertical shear reinforcement details were studied by using "digital image processing" techniques. Image processing techniques provide a faster and easier analysis of concrete cracks than manual crack measurement methods. A fast and accurate technique has been tried to provide for this analysis.

The digital images of the crack regions were taken of the beams with different shear reinforcement details under common loads near failure. These digital images were converted into binary images by using a series of digital image processing techniques. Then the crack properties such as areas, lengths, and average widths were computed automatically. The results showed that the crack properties of the different WWF reinforcement designs were consistent with those of the standard reinforcement design. The equivalent strength designs exhibited the widest cracks and largest total crack areas.

Bridges, Wire netting, Prestressed concrete beams, Concrete -- Cracking