Abstract
This paper discusses the use of confinement in over-reinforced concrete beams. This reinforcement consists of square stirrups, placed in the compression zone of the beam cross-section, in order to improve its ductility. A parametric numerical study is initially performed, using a finite element computational program that considers the material nonlinearities and the confinement effect. To investigate the influence of the transverse reinforcing ratio on the beam ductility, an experimental program was also conducted. Four over-reinforced beams were tested; three beam specimens with additional transverse reinforcement to confine the beams, and one without it. All specimens were fabricated with a concrete designed for a compressive strength of 25 MPa. The experimental results show that the post-peak ductility factor is proportional to the confining reinforcement ratio, however the same is not observed for the pre-peak ductility factor, which varied randomly with changes in the confining reinforcement ratio. It was also observed from the experiments that the confinement effect tends to be smaller close to the beam neutral axis.
Highlights
The ductility analysis of reinforced concrete beams has been studied by several researchers, Base [1], Base & Read [2], Nawy [3] and Ziara et al [4]
Considering the results obtained through the numerical analysis along with an understanding acquired through bibliographic review, an experimental program was elaborated with the aim to analyze the ductility of the beams with confinement reinforcement
This was already expected, because according to the numerical analysis developed in item 4, the predominant factor of the pre-peak ductility index for beams confined through square stirrups is the concrete compression strength, followed by tensile reinforcement strain and the spacing between confinement stirrups
Summary
The ductility analysis of reinforced concrete beams has been studied by several researchers, Base [1], Base & Read [2], Nawy [3] and Ziara et al [4]. A statistics plan was created to determine the ideal ductility indexes, considering normally balanced beams These indexes were determined by numerically analyzing underreinforced beams with 10 ‰ longitudinal strain in the tensile reinforcement and 3.5 ‰ concrete longitudinal strain (compressive zone), varying the height and width of the beam cross section as well as the concrete compression strength. Considering the results obtained through the numerical analysis along with an understanding acquired through bibliographic review, an experimental program was elaborated with the aim to analyze the ductility of the beams with confinement reinforcement. This program consisted of testing four reinforced concrete beams, whereas three of them were designed with confinement reinforcement and one without it. All the tested beams were designed following normally balanced beams specifications considering the specific concrete strains equal to 3.5 ‰, in the compressive zone
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