Influence of longitudinal reinforcement type on the shear strength of reinforced concrete beams without transverse reinforcement
Abstract
Since FRP bars are not susceptible to corrosion, they have emerged as a replacement to steel reinforcement in concrete, with the potential of reducing lifetime costs in applications where corrosion of steel bars causes costly maintenance. However, there may be differences in the behavior of reinforced concrete members reinforced with these materials as compared to steel. The shear design of reinforced concrete members has been based on empirical methods developed from experiments. Considering experimental evidence from steel reinforced concrete shear tests, the use of low longitudinal reinforcement ratios can cause a reduction in shear strength. The use of FRP bars as flexural reinforcement, which produces unusually low longitudinal reinforcement ratios when converted to equivalent steel areas, may yield a similar effect. The investigations conducted here consisted of two phases: an experimental and an analytical. The experimental phase investigated the effect of using FRP bars as longitudinal reinforcement on the shear strength and behavior of rectangular concrete beams without transverse reinforcement. It was determined that when equal areas of tensile reinforcement are provided, FRP bar reinforced concrete beams fail at a lower shear strength than steel reinforced ones. However, when the bending stiffness after flexural cracking was kept constant (concrete strength and ρeff constant), the shear strength was approximately the same regardless of the reinforcement type used. The analytical phase concentrated on the relationship between the neutral axis depth at cracking and the shear strength of the member. Considering this relationship, a simple analysis method based on mechanics to calculate the concrete contribution to shear strength of rectangular reinforced concrete beams regardless of the longitudinal reinforcement type was developed. The proposed design method was shown to be valid by testing it on a 339-specimen database of rectangular reinforced concrete specimens regardless of the type of flexural reinforcement. Finally, the applicability of the proposed design method in calculating the concrete contribution to the shear strength of members with other cross sectional shapes such as flanged and circular sections was discussed.
Degree
Ph.D.
Advisors
Frosch, Purdue University.
Subject Area
Civil engineering
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