Vibrational Tension Measurement of External Tendons in Segmental Posttensioned Bridges
Publication: Journal of Bridge Engineering
Volume 11, Issue 5
Abstract
A rapid and economical vibrational tension measurement method is presented to detect distress in external tendons used in segmental posttensioned bridges. This method provides a complementary technique to traditional inspection methods currently employed in the field. The natural frequency and overtones produced by an impact excitation are measured and used to determine the tendon segment’s tension and flexural stiffness using a differential equation describing a stiff string with clamped-clamped boundary conditions. The flexural stiffness is not negligible in tendons of this type causing the vibration modes to be inharmonically related. This method provides consistent (typically within 1%) and reasonably accurate (typically within 10%) estimates of tendon tension. Accuracy can be improved by lessening uncertainty in input constants such as the tendon mass and tendon length. Application examples from several in-service bridges have shown that detection of corrosion damage, improper tensioning, and force distribution effects from friction at deviation blocks can be detected.
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Acknowledgments
This investigation has been supported by the Florida Department of Transportation (FDOT) and the Federal Highway Administration (FHWA). The findings and conclusions expressed here are those of the writers and not necessarily those of the funding agencies. The writers are indebted to the cooperation of field test teams from Vector Engineering, KSC, Corven Engineering, and to many FDOT investigators with special recognition for R. G. Powers who first suggested the use of vibrational tests for these systems. The writers also recognize the assistance of R. Hoehne, F. Presuel-Moreno, V. Balakrishna, C. Cotrim, and A. Saradhi in programming, data evaluation, and test equipment and procedures.
References
Ciolko, A. T., and Yen, W. P. (1999). “An immediate payoff from FHWA’s NDE initiative.” Public Roads, 62(6), 10–17.
Corven Engineering, Inc. (2001). Mid-Bay Bridge post-tensioning evaluation final rep., Final Report to Florida Department of Transportation District 3 (available through the Florida Department of Transportation at http://www.dot.state.fl.us/ ).
Fletcher, H. (1964). “Normal vibration frequencies of a stiff piano string.” J. Acoust. Soc. Am., 36(1), 203–209.
Mehrabi, A., and Tabatabai, H. (1998). “Unified finite difference formulation for free vibration of cables.” J. Struct. Eng., 124(11), 1313–1322.
Morse, P. M. (1948). Vibration and Sound, McGraw-Hill, New York.
Naaman, A., and Bren, J., eds. (1990). “External prestressing in bridges.” ACI SP-120, American Concrete Institute, Detroit.
Parsons Brinckerhoff Quade & Douglas, Inc. in association with Concorr Florida, Inc. and Kisinger Campo & Associates Corp. (2002). Sunshine Skyway Bridge post tensioned tendon investigation, FPN: 411135 1 32 01, Report to Florida Department of Transportation District Seven.
Sagüés, A. A., Eason, T. G., Cotrim, C., and Saradhi, A. (2003a). Results of detailed analysis of vibration testing of external tendons in the high approaches of the Sunshine Skyway Bridge, Final Report to Florida Department of Transportation, Task 4, Project BC353-44.
Sagüés, A. A., Kranc, S. C., Balakrishna, V., and Saradhi, A. (2004). Test preparation and data analysis for vibrational testing of Mid Bay Bridge tendons, Final Report to Florida Department of Transportation, Contract No. BC353–17 (available through the Florida Department of Transportation at http://www.dot.state.fl.us/ ).
Sagüés, A. A., Kranc, S. C., and Hoehne, R. H. (2000). Initial development of methods for assessing condition of post-tensioned tendons of segmental bridges, Final Report to Florida Department of Transportation, Contract No. BC374 (available through the Florida Department of Transportation at http://www.dot.state.fl.us/ .
Sagüés, A. A., Powers, R. G., and Wang, H. (2003b). “Mechanism of corrosion of steel strands in post tensioned grouted assemblies.” Corrosion/2003, Paper No. 03312, NACE International, Houston.
Young, R. W. (1962). “Frequencies of simple vibrators.” American Institute of Physics Handbook, McGraw-Hill, New York, 3–110.
Young, W. C. (1989). Roark’s formulas for stress and strain, 6th Ed., McGraw-Hill, New York.
Zui, H., Shinke, T., and Namita, Y. (1996). “Practical formulas for estimation of cable tension by vibration method.” J. Struct. Eng., 122(6), 651–656.
Information & Authors
Information
Published In
Journal of Bridge Engineering
Volume 11 • Issue 5 • September 2006
Pages: 582 - 589
Copyright
© 2006 ASCE.
History
Received: May 27, 2004
Accepted: Dec 15, 2004
Published online: Sep 1, 2006
Published in print: Sep 2006
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