Experimental investigation of the pre-tension effects on the modal parameters of a slender pre-tensioned concrete beam
Slender pre-tensioned concrete structures are nowadays of common use, due to their unique features. Slender beam can be used to sustain large structures and important loads leaving the architects a lot possibilities in the structure design. The health of such structures is strictly related to the conditions of the tendon that, in many cases, are not accessible. Visual inspection is the most used technique to assess the tendon condition even if in many cases access to the inspection points is very difficult or impossible. This paper investigates the possibility of detecting a pre-stress loss or a tendon failure by means of modal analysis. A pre-stressed concrete beam has been built and tested under laboratory conditions, varying the applied prestress and the number of active tendon. Modal analysis has been performed in each of the experimental condition and attention has been focussed on the variation of all identified modal parameters, frequency, damping and mode shapes. Furthermore a set of damage indexes have been computed to highlight the most sensible magnitude able to identify a change on the structure. Obtained results showed that an accurate analysis is needed in order to identify a change in modal parameters due to variations in the pre-stress, while tendon failure leads to more important changes in the identification results. The performed study are the starting point in order to properly tune a numerical model of the beam useful to accurately interpreter structural changes.
KeywordsCoherence Assure Decid Stimated Cond
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- 1.M. G. Ali, A. R. Maddocks, “Evaluation of corrosion of prestressing steel in concrete using non-desctructive techniques” Corresion and Materials;Vol.28,No 5, 42–48,2003.Google Scholar
- 2.M. Bruggi, A. Caprioli, M. Vanali, P. Venini, “Investigation of the Pre-Stress Loss in the Dynamical Behaviour of Concrete Beams ”, in Proceedings of the 26 International Modadl Analysis Conferences- IMAC, 2008Google Scholar
- 3.W. Doebling, C. R. Farrar, M. B. Prime, D. W. Shevitz “Damage Identification and Health monitoring of Structural Mechanical Systems from Changes in Their Vibration Characteristics: a Literature Review” Los Alamos National Laboratory, Los Alamos, NM, USA, Tech. Rep. LA-13070-MS, May 1996.Google Scholar
- 6.J.T. Kim, C.B Yun, Y.S. Ryu, H.M. Cho, “ Identification of prestress-loss in PSC beams using modal data”, Structural Engineering and Mechanics, Vol. 17, No 3–4, 467–482, 2004.Google Scholar
- 8.J.F. Unger, A. Teughels, G. De Roeck, “System Identification and Damage Detection of a Prestressed Concrete Beam” Journal of Structural Engineering, 132, 1691–1698, 2006 ASCE.Google Scholar
- 9.UNI EC 1–2006 UNI EN 1992-1-1:2005 “Eurocode 2 – Design of Concrete Structures Part 1–1: General rules and rules for buildings”Google Scholar
- 10.UNI EN 206–1:2006 “Concrete – Part 1: Specification, performance, production and conformity”Google Scholar
- 12.Peeters, B. "The PolyMAX frequency-domain method: a new standard for modal parameter estimation?" Shock and Vibration, 11(3–4), 395–409, 2004.Google Scholar
- 13.Caprioli, A., Cigada, A., and Vanali, M. "Comparison between different operational modal analysis techniques for the identification of large civil structure modal parameters" in Proceedings of the 24th International modal analysis conference, St. Louis, Mo, USA, 2006.Google Scholar