Effect of Shear Span-Depth Ratio on Shear Strength of Porcelanite Lightweight Aggregate Reinforced Concrete Deep Beams Strengthened by Externally Bonded CFRP Strips

Abstract

This paper presents an experimental investigation of structural behaviour of reinforced concrete deep beams strengthened in shear by CFRP strips. The experimental program consisted of fabricating, casting and testing of nine identical porcelainte lightweight aggregate reinforced concrete deep beams. Three of the tested deep beams were unstrenghtened to serve as reference beams, while the remaining beams were tested after being strengthened using CFRP strips in two different orientations (vertical and horizontal). The locally available natural porcelanite aggregate is used to produce lightweight aggregate concrete. The beams were designed to satisfy the requirements of ACI 318M- 14 building code. In order to insure shear failure modes, adequate flexural steel reinforcement were provided. Effect of three different values of shear span to effective depth ratio (a/d =1.0, 0.8, 1.2) were selected. All beams have been tested as a simply supported beams subjected to two concentrated points loading. The beam specimens were tested up to failure under monotonic loads. The experimental work showed that the failure load increases as the shear span to effective depth ratio deceases. As the shear span to effective depth ratio decreased from 1.0 to 0.8, the percentage of increase in the ultimate load was about 24%. In addition, the diagonal compression strut crack of unstrenghtened control beams was changed to several diagonal cracks at mid depth within the shear span of the strengthened beams and exhibited more ductile failure mode.

Keywords

• shear span
• shear strength
• lightweight concrete
• cfrp
• deep beams