Funding:

• • National Science Foundation

  • California Department of Transportation

Collaborators:

• • Prof. Jose Restrepo, UCSD

Purpose:

To develop an ultrasonic wave-based technique using embedded sensors to (1) detect defects and (2) monitor the level of prestress in multi-wire prestressing tendons used in post-tensioned concrete structures.

Synopsis:

Prestressing tendons are the main load carrying components of cable-stayed and suspension bridges as well as post-tensioned concrete structures. 90% of bridges in California, for example, are post-tensioned concrete. Defects in the tendons (e.g. corrosion, broken wires) as well as loss of prestress, if not detected early, can lead to catastrophic collapse of the structure. We are optimizing ultrasonic guided wave means to provide both detection of defects in the tendons (corrosion and broken wires), and measurement of applied prestress levels.

On the prestress measurement side, we have identified both linear ultrasonic features (inter-wire leakage) and nonlinear ultrasonic features (inter-wire contact) which are indeed sensitive to the level of load applied to a multi-wire strand. We have carried out numerical analyses (SAFE, FEA) and experimental tests that confirm this statement.

We have also validated the linear and nonlinear ultrasonic features for tendon monitoring in large-scale tests of post-tensioned concrete joints conducted at UCSD’s Powell Structural Laboratories in collaboration with Prof. Restrepo’s group.

The work in this project indicates that ultrasonic probing of the prestressing strands can indeed be effective for the detection of defects as well as for the monitoring of prestressing forces in post-tensioned concrete structures. Based on these findings, strategies for both real-time health monitoring and routine-based inspections of post-tensioned bridges have been proposed. These strategies will need to be validated in additional large-scale laboratory tests and field tests of bridges in service.

Selected Publications:

Salamone, S., Veletzsos, M., Lanza di Scalea, F., and Restrepo, J., “Detection of Initial Yield and Onset of Failure in Bonded Post-tensioned Concrete Beams,” ASCE Journal of Bridge Engineering, Special Issue on NDE/NDT for Bridge Inspection and Evaluation, 17(6), pp. 966-974, 2012.

Salamone, S., Bartoli, I., Phillips, R., Nucera, C., and Lanza di Scalea, F., “Health Monitoring of Prestressing Tendons in Post-Tensioned Concrete Bridges,” Journal of the Transportation Research Board, Transportation Research Record no. 2220, pp. 21-27, 2011.

Bartoli, I., Salamone, S., Phillips, R., Lanza di Scalea, F. and Sikorsky, C., “Use of Interwire Ultrasonic Leakage to Quantify Loss of Prestress in Multiwire Tendons,” ASCE Journal of Engineering Mechanics, 137(5), pp. 324-333, 2011.

Nucera, C. and Lanza di Scalea, F., “Monitoring Load Levels in Multi-wire Strands by Nonlinear Ultrasonic Waves,” Structural Health Monitoring International Journal, 10(6), pp. 617-629, 2011.

Bartoli, I., Salamone, S., Phillips, R., Nucera, C., and Lanza di Scalea, F., “Health Monitoring to Detect Failure of Prestressing (PS) Cables in Segmental Box-girder Bridges,” Technical Report No. CA-090938 to the California Department of Transportation, University of California, San Diego, 2009 (131 pages).

Lanza di Scalea, F., Bartoli, I., Rizzo, P., Marzani, A., Sorrivi, E., and Viola, E., “Structural Health Monitoring of Multi-wire Strands,” Chapter 151 of Encyclopedia of Structural Health Monitoring, C. Boller, F-K. Chang and Y. Fujino, eds., Johns Wiley & Sons, Chichester, UK, pp. 2487-2503, 2009.

Bartoli, I., Salamone, S., Phillips, R., Lanza di Scalea, F., Coccia, S., and Sikorsky, C., “Monitoring Prestress Level in Seven-wire Prestressing Tendons by Inter-wire Ultrasonic Wave Propagation,” Journal of Advances in Science and Technology – Embodying Intelligence in Structures and Integrated Systems, Vol. 56, pp. 200-205, 2008.

Rizzo, P., Sorrivi, E., Lanza di Scalea, F., and Viola, E., “Wavelet-based Outlier Analysis for Guided Wave Structural Monitoring: Application to Multi-wire Strands,” Journal of Sound and Vibration, Vol. 307(1-2), pp. 52-68, 2007.

Rizzo, P. and Lanza di Scalea, F., “Feature Extraction for Defect Detection in Strands by Guided Ultrasonic Waves,” Journal of Structural Health Monitoring, Vol. 5(3), pp. 297-308, 2006.

Rizzo, P. and Lanza di Scalea, F., “Wavelet-based Feature Extraction for Automated Defect Classification in Strands by Ultrasonic Structural Monitoring,” Smart Structures and Systems, Vol. 2(3), pp. 253-274, 2006.

Rizzo, P. and Lanza di Scalea, F., “Wave Propagation in Multi-wire Strands by Wavelet-based Laser Ultrasound,” Experimental Mechanics, Vol. 44(4), pp. 407-415, 2004.

Lanza di Scalea, F., Rizzo, P. and Seible, F., “Stress Measurement and Defect Detection in Steel Strands by Guided Stress Waves,” ASCE Journal of Materials in Civil Engineering, Special Issue on NDE/Health Monitoring, Vol. 15(3), pp. 219-227, 2003.