Tomonori Nagayama Assistant professor the department of Civil Engineering University of Tokyo

1. Inspection and dynamic measurement of the Pilot-Study Bridge of the Long-Term Bridge Performance Program in New Jersey Tomonori Nagayama Assistant professor the department of Civil EngineeringUniversity of Tokyo

2. Univ of Tokyo Involvement (April 19-21, 2010) Visual Inspection following Japanese Bridge Inspection Standard Three days of a dynamic measurement campaign using dense wireless sensors and wired accelerometers.

3. Inspected spans A1 A2 Four spans were inspected by Mr. Haneoka for three days. Identified damages are evaluated one by one. No overall rating (health index) for the bridge nor substructures are provided in inspection. Some owners have their own ways of rating for asset management. (ex. 100 % – Σdamagei) B1 B2 Classificationfor each damage Countermeasure assessment

4. Major findings from the inspection 1 • Fatigue cracks at the gusset plates connecting the main beam and lower lateral bracing • Stop-holes and bolts already stop the cracks, but potentially dangerous. Reduction of the stress concentration at all the gussets plates is recommended. Recommendation cut Newconnection

5. Major findings from the inspection 2,3 2 bolts are lost • Two bolts connecting an intermediate bracing are lost. The other one is likely loose. New bolts need to be installed. • Bearing shoe stopper is cut or deformed Lost bolts B1 Loose bolt? ΔＬ Cut A1 Stopper Cut B1 Deformed Deformed

6. Major findings from the inspection 4,5 Deformed flange • Anchor bolts of bearing shoes are loose, or short. • A part of P2 concrete pier cap is degraded (cracks, missing concrete) A2 Lose bolt, deformed bottom flange Loose bolts B2 Short bolts

7. Visual Inspection report practice: summary figure (span A1) Possible fatigue crack locations All the assessed damages are written down on the drawing and listed in summary table formats .

8. The detailed description follows

9. Other points • The inspection cost is $50,000 for the eight spans. $18,000 is personnel cost for inspection. $23,000 is personnel cost for the other tasks (preparation, report, etc.). • For damages judged as “C” (and sometimes “B”), further investigation and repair work planning (may include health index evaluation) are ordered. Damages evaluated as “A” are referred to at the next inspection. “E1”, and “E2” need repair work immediately. • It is possible to provide “health index” for each substructure, but it is not a part of common bridge inspection practices in Japan. Based on inspection results, owners may rank each substructure for asset management.

10. Inspection by image processing techniques(demonstration) Mr. Sugimoto applied image processing techniques to assess the substructure condition. 1pix=1mm 0.5mm crack can be identified. 100 millon pix 460 MB/TIF 4000 pix Width legend－－： <0.5mm ， －－： 0.5mm～0.7mm， －－： >0.7mm

11. 1.6mm 0.2mm 1.4mm 800mm Crack on the abutment A1; Photos taken 22 meters away; Theresolution can be as good as 0.1mm/pix if appropriately prepared.

12. Mr. Sugimoto’s overall impression about the bridge:“Very good condition” as compared to bridges in Japan. Automatic crack detection About 70 % of the cracks are identified

13. DynamicMeasurement Campaigns A4 A1 A2 B4 B1 B2 • Wireless sensors, Imote2s, were employed on the two outer spans (A1,B1 and A4, B4). (41 nodes = 123 channels at a time) • Wired accelerometers were employed on the two inner-spans (A2, B2, A4, and B4) (

14. Findings: motions below and above bearings Longitudinal direction -> fix A little different Longitudinal direction -> move Move Fix Longitudinal direction -> fix “Move” condition is not always satisfied. Fix is not necessarily satisfied either. Depends on the direction. Direct relationship with the inspection results has yet to be found.

15. Finding: acceleration amplitude distribution among girders Lateral acceleration Malfunctioning sensor A1 B1 Vertical acceleration Lateral vibration: large at outer girders Vertical vibrations: similar among girders -> Emphasis onthe fatigue cracks corresponding to the lateral motions A1 B1

16. Findings: global motion Acceleration power spectral density Freq(Hz) Mode shape of Span A1 Freq =2.81 Hz Freq =14.5 Hz 9 modes were identified. Some nodes giving noisy data could have distorted the estimated mode shapes

17. Conclusion • Major findings from the visual inspection are the fatigue cracks, gusset plate bolts, bearing stoppers and bolts, and the concrete pier cap. • Image processing has been demonstrated for concrete crack detection. • Vibration measurement revealed that the motion of bearings are not necessarily the same as the design conditions. Vibration modes are also identified. The insufficient quality of the data limits the analysis of the data.