long-term monitoring of us202-nj23 bridge (wayne, nj)
DESCRIPTION
IBS Workshop at CAIT 14-15 June 2011, Rutgers University, NJ, USA. Long-term monitoring of US202-NJ23 Bridge (Wayne, NJ). Branko Glisic 1 , Daniele Inaudi 2 , Dorotea Sigurdardottir 1 1 Princeton University, Princeton, NJ, USA 2 SMARTEC SA (Roctest Group), Switzerland. Outline. - PowerPoint PPT PresentationTRANSCRIPT
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Long-term monitoring of US202-NJ23 Bridge (Wayne, NJ)
Branko Glisic1, Daniele Inaudi2, Dorotea Sigurdardottir1
1Princeton University, Princeton, NJ, USA2SMARTEC SA (Roctest Group), Switzerland
IBS Workshop at CAIT
14-15 June 2011, Rutgers University, NJ, USA
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Outline
• Introduction
• Aims
• Monitoring system
• Installation
• Preliminary results
• Acknowledgements
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Introduction• SHM has potential to improve bridge safety and
management
• Although it is frequently applied to “signature” structures, SHM can truly be declared as “useful” if its utility is proven on “ordinary” (typical) structures
• Nevertheless, SHM is scarcely applied to typical structures due to several reasons among which are ease of use of data and the cost
• US202-NJ23 Bridge close to Wayne, NJ, is a good example of typical structure and excellent opportunity to test utility of SHM applied to typical structures
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Aims of SHM• To deploy affordable SHM system
• To register structural behavior of bridge girders over long term and perform structural identification based on periodic dynamic measurements
• To identify unusual behaviors related to monitored parameters: average strain, average curvature, natural frequency, and evaluate concrete-steel interaction
• To evaluate suitability of employed monitoring system for achieving above aims in terms of measurement performance and longevity
• To estimate value of information and evaluate long-term costs and benefits of monitoring
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Fiber Bragg Grating (FBG) Sensors
The reflected wavelength depends on the strain and temperature of the fiber: l1=Ce·De+CT·DT+l1,0
~ 10 mm
• FBG = periodic refractive index perturbation generated in the core• Strain and temperature in fiber change the back-reflected WL
l1(De1 ,DT1)
l1(De1 ,DT1)
l2(De2,DT2)
l2(De2 ,DT2)
Multiple FBG can be inscri-bed over the same fiber
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Position of sensors
• Pairs of parallel sensors were installed in girders #2 and #5 of the southbound part of the bridge
• Positions of the sensors were adjusted to the site conditions
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Summary of instrumentation • Reading unit:
– Dyn.: 250 Hz (1 kHz), 4 me, 1°C– Static: 0.4 me, 0.1°C– 12 (of 16) channels
• Girder #2: – Gauge length at quarter span = 1m– Gauge length at mid span = 2m– 6 strain + 6 temperature sensors
• Girder #5: – Gauge length at quarter span = 2m– Gauge length at mid span = 2m– 12 strain + 12 temperature sensors
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Installation• Using L-brackets, by gluing
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Installation, continued
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Examples of results• Average strain generated by traffic has been
measured and several “events” were registered
• The following parameters will be calculated:
– average curvature
– position of center of gravity (concrete-steel interaction)
– natural frequency
– thermal expansion
– correlation in behavior of two girders
• These parameters will be observed in long term
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Examples of results
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Acknowledgements• Drexel University, in particular Prof. Emin Aktan, Prof.
Frank Moon, and graduate student Jeff Weidner for opportunity to participate in the project, organization, and help during the installation
• LTBP Program, NJDOT, and CAIT for opportunity to participate in the project
• IBS partners for comprehension in sharing the lifts during the installation
• Kevin for help in operating the lifts
• Yao Yao, graduate student of Princeton University for availability and help in installation of sensors