Department: Structural Engineering
Francesco Lanza di Scalea
Name: Ivan Bartoli
Email: ibartoli @ ucsd.edu
Grad Year: 2007
Elisa Sorrivi, esorrivi @ ucsd.edu | Robert Ronald Phillips, rrphilli @ ucsd.edu
High-strength, multi-wire steel strands are widely used in civil engineering such as in prestressed concrete structures, and cable-stayed or suspension bridges. Material degradation of the strands, usually consisting of indentations, corrosion or even fractured wires, may result in a reduced load-carrying capacity of the structure that can lead to collapse. In a survey involving the study of more than one hundred stay-cable bridges Watson & Stafford (1988) pessimistically reported that most of them were in danger mainly because of cable defects. Strand failures that caused bridge collapses were documented in Wales (Woodward 1988), Palau (Parker 1996), and North Carolina (Chase 2001). Hence the need for developing monitoring systems for strands that can detect, and possibly quantify, structural defects, as well as alert of any prestress loss. Structural monitoring methods based on Guided Ultrasonic Waves (GUWs) have the potential for both defect detection and stress monitoring. GUWs have been used for the detection of defects in multi-wire strands and reinforcing rods (Kwun and Teller, 1995; Beard et al. 2003; Reis et al. 2005) and for the evaluation of stress levels in post-tensioning rods and multi-wire strands (Kwun et al. 1998). The authors have used GUWs for defect detection and stress monitoring in seven-wire steel and composite strands (Rizzo and Lanza di Scalea, 2006). This paper summarizes representative results obtained to date by the authors on the detection of defects and the monitoring of prestress levels in strands.
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