corrosion stack is particularly useful for character- izing cyclic or condition-based bridge preserva- tion activity—especially useful for bridges with a National Bridge Inventory (NBI) rating between 7 and 9 (bridges in “good” condition). Ñ Damage Stack: IE is the primary NDE technique for the detection and characterization of deck delamination. USW provides a quantitative assessment through the measurement of concrete modulus and is an indicator of concrete quality. It sometimes indicates delaminated areas as well. The damage stack is useful for characterizing the extent of condition-based preservation activity— especially useful for bridges with an NBI rating of 5 or 6 (“fair” bridges). Figures 8 and 9 demonstrate a sample of an NDE stack from a bridge in the Mid-Atlantic cluster obtained through the FHWA Long-Term Bridge Performance (LTBP) program (Gucunski et al. 2016 Kim et al. 2019). As a part of the QC/QA process, it is important to ensure all NDE results are consistent and follow reasonable correlation across different 30 0 10 20 30 40 50 60 70 80 90 100 110 120 0 0.5 1 1.5 2 2.5 in. 3 3.5 4 4.5 kΩ × cm 100 (mV) Attenuation at top bar level (dB) 150 –7 Sound Fair Poor Serious –9–1 1 –13 –15 –16 –17 –18 –19 –20 –25 –30 –43 50 90 % probability of no corrosion activity 90 % probability of no corrosion activity Moderate High Low Very low Corrosion activity uncertain –50 –150–250–350–450–550–650–750 908070605040302010 0 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 20 10 30 0 20 40 60 80 100 120 140 160 180 200 220 240 260 20 10 30 0 20 40 60 80 100 120 140 160 180 200 220 240 260 20 10 30 0 20 40 60 80 100 120 140 160 180 200 220 240 260 20 10 Figure 8. Comparative assessment of NDE technologies on corrosion stack: (a) GPR cover depth (b) ER (c) HCP (d) GPR amplitude. J A N U A R Y 2 0 2 3 • M AT E R I A L S E V A L U AT I O N 31 2301 ME Jan New.indd 31 12/20/22 8:15 AM Co ve r ER HC P GPR COURTESY: DR. NENAD GUCUNSKI, RUTGERS UNIVERSITY

test methods. The results indicate that ER, GPR, and HCP generally correlate in defective zones (shown in the broken rectangle), showing the onset of the corrosion activity (Figure 8). The same conclusion is observed for the correlation between the IE and USW contours for the damage phase (Figure 9). Such strong correlation between multiple NDE techniques confirms the improved reliability of complementary NDE technologies to monitor the progression of corrosion leading to damage in a bridge deck. The above correlation between defec- tive zones provides for a qualitative assessment of condition a more rigorous, statistically based condition evaluation of the deck is presented in Babanajad and Jalinoos (2022). Several efforts are underway from FHWA, which is currently working with nine state trans- portation agencies to determine the feasibility and cost-benefit of incorporating NDE and SM methods into bridge deck preservation strategies. Adoption of NDE/SM information should complement data- driven decision-making systems in the selection of various preservation actions. This ongoing effort includes investigating and documenting the con- ventional NDE/SM technologies that are currently being used quantifying the value of NDE/SM using return on investment methodology and developing a model that relates NDE/SM results to the struc- ture’s condition and quantifies the associated return on investment for each maintenance and preserva- tion strategy. In addition, FHWA and Iowa DOT led an initiative to develop the framework for a bridge deck preservation portal (BDPP) intended to be widely available to engineers across the nation and widely applicable but tailorable to bridge-specific scenarios the engineers encounter. The BDPP frame- work (ElBatanouny et al. 2020) provides a system- atic approach for predicting changes to bridge deck service life by combining physical characteristics, condition assessments, and user preferences/con- straints with the application of specific bridge deck maintenance actions. When completed, the devel- oped cloud-based tool will be hosted on the FHWA’s InfoBridge website (https://infobridge.fhwa.dot.gov/). Conclusion Despite the obvious advantages, deployment of multiple complementary NDE technologies still has not gained widespread use for informed main- tenance and replacement decision-making. This is attributed to the following factors: Ñ Reliability of advanced technologies: Technological advancement has been rapid while there are few studies available on their reliability. Many NDE technologies have been well proven for local defect characterization, but their use in large-scale components is still not very clear. The standardization of methods, measurement incon- sistency among multiple NDE technologies, lack of temporal and spatial correlations for multiple datasets, lack of repeatability between multiple vendor technologies, reliability of a given method, reporting requirements, and different measurement resolution limit the capabilities of many NDE tech- niques in being integrated into routine practice. More work is underway to address these areas. Ñ Cost-effectiveness: Cost-effectiveness has been a major issue in implementing advanced tech- nologies. New technologies should provide value to owners. To augment them with routine visual FEATURE | BRIDGEINSPECTION 0 30 20 10 50 0 2500 Sound Fair Poor Serious 3200 3800 4400 (Ksi) 5000 5600 100 150 200 250 0 30 20 10 50 100 150 200 250 Figure 9. Comparative assessment of NDE technologies on damage stack: (a) USW (b) IE. 32 M AT E R I A L S E V A L U AT I O N • J A N U A R Y 2 0 2 3 2301 ME Jan New.indd 32 12/20/22 8:15 AM COURTESY: DR. NENAD GUCUNSKI, RUTGERS UNIVERSITY US W IE