Browsing by Author "Moravvej Hamedani, Mohammad Hossein"

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    Reference-Free Response-Only Damage Identification in Bridges Using Relative Wavelet Entropy
    (2019-04-17) Moravvej Hamedani, Mohammad Hossein; El-Badry, Mamdouh; Duncan, Neil A.; Dann, Markus R.; Dilger, Walter H.; Sudak, Leszek Jozef; Narasimhan, Sriram; Khoshnazar, Rahil
    Bridges 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.
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    Static and Fatigue Behaviour of Hybrid FRP-Concrete Bridge Truss Girder with Connections Reinforced with Double-Headed Bars
    (2014-01-30) Moravvej Hamedani, Mohammad Hossein; El-Badry, Mamdouh
    An innovative hybrid FRP-concrete bridge system for short- and medium-span bridges has been developed at the University of Calgary. This system is composed of concrete deck slabs composite with precast prestressed concrete truss girders, consisting of pre-tensioned top and bottom chords connected by vertical and diagonal truss members made of concrete-filled fiber-reinforced polymer tubes. The advantages of this system include reduced self-weight and enhanced durability. The objective of this research is to investigate the performance of the truss girder under static and fatigue loading. An experimental program including fabrication of ten full-scale truss girders with the number of panels varying from two to eight is presented. The effect of several parameters, such as the span-to-depth ratio and the amplitude of fatigue loading on the performance of the truss girder are investigated. The tests showed excellent performance of the girder system in terms of strength and stiffness.