11-13-2012, 09:09 AM
Validation and Practical Procedure for Vibrational Evaluation of Tendons
Author: Sagues, Alberto A | Size: 1.62 MB | Format: PDF | Quality: Original preprint | Publisher: University of South Florida, Tampa | Year: 2008 | pages: 189
Vibrational testing of tension to identify potentially distressed external tendons of post-tensioned segments and columns has been successfully used in major Florida Department of Transportation (FDOT) bridges. This investigation provided validation of basic assumptions and verification of tension obtained by the vibration method against independent load cell measurements with tendon segments of size, length, and tension levels comparable to those used in actual structures. Measurements were conducted in a specially built tendon test facility with 12-strand tendons up to nearly 10 m (400 in.) long, some including a deviation block. Tension estimated from vibration tests was on average within ~6% of load cell measurements, after correction for the effect of metal pipe ends in some cases. Upon simulated strand failures at the anchorage area there was tension loss that was tracked adequately in nearly all cases by the vibration tests. Advanced data processing methods were developed to perform rapid evaluation of data from large populations (thousands) of tendons in actual bridges. Vibration test field equipment was developed for simplified operation and analysis procedures. A portable field equipment prototype was designed and constructed to permit testing by a single operator. Extensive vibration tests of tendons were conducted in the segmental approaches of the Sunshine Skyway Bridge, revealing generally normal tension levels but flagging specific tendons with fringe performance for subsequent inspection. A user-oriented summary of findings and applications is provided.
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