5.6 NDE Data Analysis Summary and Conclusion

Figure 57. Defect index calculated from HD and IR images

5.6 NDE Data Analysis Summary and Conclusion In the previous subsections, the periodic data collected using multiple NDE techniques were thoroughly analyzed and assessed against the life cycle of a representative bridge. In essence, the deployed NDE techniques included a variety of contact and non-contact techniques. Consequently, multiple NDE performance indicators were developed and compared. After a careful review of the results and performance indicators, the criteria shown in Table 8 were set. Table 8 is developed based on the review of the NDE performance indexes discussed in the previous subsections. The performance indexes were compared against the predicted performance of the bridge deck (during real work in-service conditions) and the frequency and timing of NDE assessment were identified. It should be noted that the proposed criteria were set based on very preliminary collection and analysis of the data from BEAST with its unique structural characteristics and testing scheme. The extension of such criteria for actual bridges under different loading circumstances shall be further evaluated. The table consists of six main columns, where each column sets certain thresholds for each NDE technology. The first and second columns refer to the proposed timing of NDE assessment in terms of age and rating of the deck, respectively. Third column subsequently proposes the time interval between consecutive NDE assessment periods. The proposed time interval between consecutive NDE assessment was determined based on the change sensitivity of a given NDE technology during the age of the concrete deck that has been observed within the aforementioned performance plots. The fourth column also indicates another criterion to specific changes in a given NDE technology that could also trigger another set of required NDE assessment. Ultimately, the last two columns correspond to defect and condition indexes, where the expected percentages were listed based on the observations made during BEAST experiment. Any values abnormally out of this range seem to trigger serious concern about the functionality of NDE