ABSTRACT
The performance of concrete bridge decks was identified as the top performance issue within the Federal Highway Administration’ (FHWA’s) Long Term Bridge Performance (LTBP) Program. To enable accurate, rapid and economical condition assessment of decks on a large number of bridges, the system named RABIT (Robotics Assisted Bridge Inspection Tool) was developed. The system concentrates on the characterization of internal deterioration and damage, in particular three most common deterioration types: rebar corrosion, delamination, and concrete degradation. For that purpose, the RABIT implements four nondestructive evaluation (NDE) technologies: electrical resistivity (ER), impact echo (IE), ultrasonic surface waves (USW) and ground-penetrating radar (GPR). Multiple NDE probes or large sensor arrays significantly improve the spatial resolution of the results. In addition, high resolution cameras image the surface of the deck for crack mapping and documentation of previous repairs.
The results from RABIT surveys are described in three forms: condition images, stitched images of the deck surface, and calculated condition indices. Condition indices quantify the overall condition of the deck. Condition indices vary from 100 for the best to 0 for the worst, or completely deteriorated condition. They represent a weighted average of percentages of the deck area in various states of deterioration. The significance of the description of the deck condition in terms of the condition index is that it enables quantified and consistent description of the condition. As a result, objective comparison between bridges, or between conditions of the same deck but at different times, can be made. Such a description of the bridge deck condition will be essential in the development of deterioration and predictive models. RABIT’s sensor and navigation components. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig120_1.jpg"/>
To illustrate the potential of NDE data, results of four surveys conducted during a period of five years on a bridge inVirginia, USA, are presented. The results are Clear trends of deterioration progression can be observed for all three NDE technologies, as well for the overall condition described by the combined condition index. The development of complete deterioration curves and models will require large sets of data that describe conditions at all stages of bridge deck lives.
