Title: Evaluation of Progressive Damage in GFRP Bars – Low and Large Strain Experimental Program and Numerical Simulations
Author(s): Piotr Wiciak, Maria Anna Polak, and Giovanni Cascante
Publication: Symposium Paper
Appears on pages(s): 88-108
Keywords: ultrasonic evaluation; non-destructive testing; GFRP deterioration; laser vibrometer; finite element analysis; wave propagation; accelerated ageing evaluation
The long-term durability of glass fiber-reinforced polymer (GFRP) in concrete remains an unresolved issue. The necessity of reliable NDT techniques for GFRP bars is critical for in-situ testing of concrete members with GFRP reinforcement. Such bars embedded in concrete show no visual deterioration and cannot be cut out of a structure to test in a traditional way. This paper presents a study of progressive damage of GFRP bars subjected to accelerated aging in alkaline solution and elevated temperature. The study offers four sections: (i) ultrasonic evaluation based on wave velocity and amplitude attenuation approaches, including characterization of ultrasonic transducers using the laser vibrometer, (ii) numerical simulations adding a more comprehensive understanding of wave propagation and investigating other testing methods, (iii) a destructive shear test carried on the bars, which investigates the level of damage in the bars and verifies the ultrasonic evaluation, and (iv) ultrasonic evaluation of bond loss for GFRP bar embedded in concrete beams. The comparison of ultrasonic evaluation, destructive shear test, and numerical simulations shows that ultrasonic techniques can successfully predict the degradation of shear strength (and ultimately tensile strength) of GFRP bars (with a maximum error of 7%). The amplitude-based ultrasonic technique is also capable of bond loss between concrete and GFRP bars.