El-Badry, MamdouhMoravvej Hamedani, Mohammad Hossein2019-04-182019-04-182019-04-17Moravvej Hamedani, M. H. (2019). Reference-free response-only damage identification in bridges using relative wavelet entropy (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.http://hdl.handle.net/1880/110178Bridges are designed and built to be safe against failure and to perform satisfactorily over their service life. To ensure safety and serviceability, it is essential to evaluate the structural performance of bridges through identification of potential damage at the earliest time possible. A vibration-based damage identification technique (DIT) that can detect structural damage, determine its location, and estimate its severity has been investigated in this research. The technique combines discrete wavelet transform (DWT) – a powerful signal processing tool for decomposition of signals – and spectral entropy in a relative procedure to detect and quantify the damage-induced disturbances in the measured dynamic response of bridges under ambient vibration. This relative wavelet entropy (RWE)-based DIT is a practical means for damage identification in in-situ cases, where the normal operation of bridges cannot be interrupted to perform dynamic excitation tests, and the data obtained from a reference (undamaged) state of the bridges are not available for comparison with the data measured from their current (damaged) state. Through its relative procedure, the technique has the advantage of mitigating undesirable effects of varying operational and environmental conditions on the damage detection process. In this research, the theoretical bases of the technique are presented, and its efficacy has been experimentally validated against false damage indications under varying operational and environmental conditions, such as the location of input dynamic excitation, location and extent of damage, support conditions, and temperature levels. The technique has also been implemented in small- and large-scale bridge specimens of various structural systems tested under different loading conditions. The test specimens included push-off columns, reinforced concrete beams, strengthened beams, precast concrete truss girders, slab-on-truss girder bridges, and post-tensioned concrete girders. The RWE-based DIT showed successful performance in identifying a wide variety of test-induced damage, including fracture in shear reinforcement, concrete cracking/crushing, debonding of strengthening sheets, rupture of truss elements’ confining tubes, and failure in truss connections. The technique has also been used to investigate the effects of pre-stressing on the dynamic behaviour of post-tensioned concrete girders to address the disagreement in the research community about the effectiveness of vibration-based DITs in pre-stress force identification.engUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.BridgesDamage Identification TechniqueDiscrete Wavelet TransformEntropyRelative Wavelet EntropyReference-FreeResponse-OnlyStructural Health MonitoringVibrationEngineering--Civildoctoral thesis10.11575/PRISM/36371