Flexural Behavior of Beams Reinforced with Steel Bars Exceeding the Nominal Yield Strength

Abdelhamid Charif,M Iqbal Khan,Shehab M Mourad

doi:10.1590/1679-78251683

Abdelhamid Charif, M Iqbal Khan + Show 1 more

Open Access

https://doi.org/10.1590/1679-78251683

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Abstract

If steel manufactures usually comply with the minimum code specifications, the nominal yield strength of rebar can however be significantly exceeded in many countries, depending on the steel manufacturing processes. Such an increase in yield strength can have negative effects on the flexural behavior of beams designed as tension controlled, and reduce their ductility, an essential property in seismic resisting structures. An experimental and analytical study of the flexural behavior of reinforced concrete (RC) beams was conducted through the investigation of the Moment-Curvature relationships and the ultimate steel strains. The main variable was the level of the actual steel yield stress as compared to the nominal value. It was found that unexpectedly high values of steel yield stress reduce the beam ductility and violate the tension-control condition which was enforced in the design stage. Appropriate design corrections are proposed to account for high yield stress values in order to achieve the desired ductility of beams while maintaining the moment capacities.

Highlights

While much attention has been given to the effect of the variability of concrete strength and properties on the response of reinforced concrete structures, there is little, if any, information on the effects of variability of steel strength
The values of u for both types of steel rebars are within reasonable range (1.00 to 1.15). These results indicate that rebars produced by the quenching process exhibit high values of yield strength as compared to the nominal value
While for concrete any strength increase may effectively be welcome without concern, for steel an unexpected increase in yield strength may reduce the structural ductility and violate the tension-control condition of reinforced concrete beams

Summary

Introduction

While much attention has been given to the effect of the variability of concrete strength and properties on the response of reinforced concrete structures, there is little, if any, information on the effects of variability of steel strength. Seismic standards have been developed with the aim of allowing steel to yield without rupture during an earthquake, in order to enhance seismic energy absorption of the structure and avoid collapse For this purpose, steel bars should possess high strength with sufficient ductility and low variation in yield strength to experience large number of inelastic cycles of deformation with large plastic strains. Steel bars should possess high strength with sufficient ductility and low variation in yield strength to experience large number of inelastic cycles of deformation with large plastic strains

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