Debonding characterization for all-lightweight RC T-Beams strengthened in flexure with FRP

• Published in: Journal of Building Engineering 2021-12, Vol.44, p.103377, Article 103377
• Main Authors: Al Shboul, Khalid W., Raheem, Mustafa M., Rasheed, Hayder A.
• Format: Article
• Language: English
• Subjects: All-lightweight concrete; Debonding strain; Flexural strengthening; FRP; RC T-beams
• ISSN: 2352-7102; 2352-7102
• DOI: 10.1016/j.jobe.2021.103377

This paper presents an experimental, analytical and numerical comparison of the behavior of lightweight and normal weight concrete beams strengthened with externally bonded high modulus carbon fiber. The main objective of this paper is to study the efficiency of using CFRP with all-lightweight concrete beams in flexural performance and validate the use of the modification factor (λ), proposed by ACI 318-19 for various concrete parameters, in adjusting the ACI 440.2 debonding strain. An experimental program was conducted using six full-scale T-beams made of two different concrete types, normal weight concrete, and all-lightweight concrete. Each series consisted of a control beam, and two beams strengthened using either two or four layers of high modulus CFRP. The results showed that the percent increase in flexural capacity is more evident in the normal weight beams as the number of layers increases. At the same time, this increase in lightweight beams is shown to be about the same beyond the use of two layers. Moreover, the reduction factors were found to be 0.93 and 0.85 leading to accurate recovery of the debonding experimental failure using the ACI 440.2 equation for the two-layered and four-layered beams, respectively. A nonlinear analysis parametric study was conducted to examine the parameter not varied in the experiments. A comparison to the debonding strain specified by other standards and models was also performed. •A first of its kind full scale experiments are conducted on all lightweight concrete T beams with bonded high modulus FRP.•The debonding strain was experimentally and analytically characterized in comparison with full scale normal weight beams.•A reduction factor l is needed to adjust the debonding strain in ACI 440.2 developed for normal weight concrete.•The reduction factors are found to differ from the λ factor suggested by ACI-318 for all lightweight concrete.