Date of Award

11-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Civil and Environmental Engineering

First Advisor

Dr. Bilal El-Ariss

Second Advisor

Dr. Said ElKhouly

Third Advisor

Ayman M. Okeil

Abstract

Steel reinforced concrete members with small shear span-to-effective depth ratios (a/d), such as corbels; have many classical applications, mostly in tall building, precast structures, factory buildings, bridges, and foundations. Despite extended research works on the performance of such members, little information is available on the performance of these members when reinforced totally with internal fiber reinforced polymer (FRP) bars. The use of FRP bars in reinforcing concrete members would eliminate corrosion problems thus increasing the service life of the structure. This thesis aims at investigating the shear strength of double-sided concrete corbels reinforced with glass-fiber reinforced polymer (GFRP) bars. The study comprises of testing twelve double-sided concrete corbel specimens. The test parameters include the shear span-to-effective depth ratio (a/d), GFRP reinforcement ratio, and concrete compressive strength. The study also includes an analytical investigation to predict the strength of the corbels using the strut-and-tie modelling (STM) technique.

Development of arch action was confirmed by the formation of the main diagonal shear cracks and the typical crushing mode of failure of the concrete in diagonal compression struts formed between the main diagonal cracks. The tested GFRP-reinforced corbel specimens failed due to crushing in concrete in the diagonal compression strut in seven specimens. In addition, two specimens failed by flexural crushing of the concrete, another two specimens failed by splitting of the concrete, and one specimen showed simultaneous failures by flexural crushing and diagonal strut concrete crushing. Increasing the GFRP reinforcement ratio increased the shear strengths of the tested specimens with the exclusion of those that exhibited splitting failure mode. Increasing the concrete strength from 20 MPa (C20) to 40 MPa (C40)

Increased the shear strength of specimens with a/d ratio of 1.0, except those with GFRP reinforcement ratio of 6 ρb (where ρb is the balanced reinforcement ratio), and decreased the shear strength of specimens with a/d ratio of 1.5.The strut and tie model utilized in this study is based on the Canadian Code CSA-S806-12 which assumes that the concrete struts fail in crushing of the concrete. However, specimens with concrete C20 and a/d=1.5 experienced flexural crushing of the concrete while specimens with concrete C40 and high GFRP reinforcement ratio of 6 ρb experienced concrete splitting failure in the diagonal strut. The STM technique slightly overestimated the shear capacity of specimens with same concrete strength (C40) and reinforcement ratio (6 ρb) but with different a/d ratios (1.0 and1.5) in comparison with the corresponding experimentally obtained results. Nevertheless, conservative predictions of the shear capacity of the rest of specimens were estimated by the STM. The predicted STM shear strengths displayed comparable values with those in the literature. However, when compared with the experimental test results, the STM gave better shear strength predictions for GFRP reinforced specimens with concrete C40 and GFRP reinforcement ratio of 6 ρb than those obtained from the literature.

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