Page 4 - June-2022

TECHNICAL PAPER

SHEAR PERFORMANCE OF

CONCRETE BEAMS OF LOW SHEAR

SPANS REINFORCED WITH

HIGH-STRENGTH STEEL SURAJ KUMAR SAHU

DIPTI RANJAN SAHOO*

Abstract led to the production of different types of high-performance
reinforcing steel worldwide. It is possible to achieve a substantial
This paper presents an experimental investigation on the shear increase in the yield strength as well as corrosion resistance
behavior of concrete beams of low shear span-to-depth ratios of steel by metallurgically modifying its microstructure. Even
with the high-strength reinforcing steel. Six beam specimens though extensive studies have been conducted to evaluate the
with two different grades of steel (500 and 550 MPa) as the mechanical material properties of high-strength steel, research
longitudinal reinforcement and three different grades of steel on the use of high-strength steel in RC members seems to be
(500, 550, and 600 MPa) as the transverse reinforcement were insufficient.
tested under monotonic loading conditions. Two different
concrete grades were considered in the test specimens, whereas High-strength steel (HSS) reinforcement may strongly influence
the shear span-to-depth (a/d) ratios were varied in the range of the shear behavior and the mode of failure of concrete
1.05-1.70. The spacing of stirrups in the beam specimens was members. Many building codes do not recommend the use of
proportionately varied based on their specified yield strengths nominal yield strengths of high-strength materials in the shear
for a constant percentage of longitudinal steel. Test results design of concrete members and limit the design yield strength
showed that beams with low concrete compressive strength and to a value of 420 MPa [1-2] . This limit has recently been raised
[3]
reinforced with 500 MPa grade longitudinal steel exhibited the to 550 MPa in ACI 318-19 to compute the shear strength of
diagonal shear failure, whereas the beams with high concrete concrete members. The primary reasons for limiting the yield
compressive strength and reinforced with 550 MPa grade strength of shear reinforcement are to control the width of
longitudinal steel failed in the predominantly flexure mode. diagonal shear cracks and to ensure the yielding of stirrups
In addition to the yielding of longitudinal reinforcement bars, before the sudden shear failure of members. The increase in
the yielding of stirrups was observed in all beams including the material yield strength results in the wider spacing of stirrups
specimen having a higher a/d ratio. It was concluded that the along the length of concrete members. This may lead to
yield strength of transverse steel reinforcement in the concrete the widened diagonal cracks before the failure of members.
beams could be increased to 600 MPa without exceeding the Further, due to the higher yield strain capacity of HSS stirrups,
safety and serviceability criteria. it is possible that the crushing of concrete compression struts
may take place in the RC member before utilizing its full load-
Keywords: Concrete beams; Diagonal shear failure, High- resisting capacity.
strength steel; Shear strength; Shear span-depth ratio
Efforts have been made in recent years to explore the shear
behavior of RC members with high-strength steel as transverse
1. INTRODUCTION
[4]
reinforcement. Hara et al. conducted an experimental
The demand for high-strength steel and concrete has increased investigation on four RC beams with steel stirrups having the
in recent years to meet the requirements of smaller member specified yield strength of 785 MPa. Test results showed that the
sizes, cost savings, and faster construction. For large-sized high-strength stirrups reached their yielding strain limits when
reinforced concrete (RC) structures, such as high-rise buildings, the concrete compressive strength was higher than 50 MPa. Lee
long-span bridges, and nuclear power plants, the use of high- et al. concluded that the shear failure mode of members was
[5]
strength steel reinforcement results in improved concrete influenced by the concrete compressive strength if the yield
placement, the reduction of reinforcement congestion in the strength of shear reinforcement exceeds 700 MPa. Sumpter
critical regions, and enhanced corrosion resistance in some et al. conducted shear tests on nine concrete beams reinforced
[6]
cases. The recent advancements in material technology have with the conventional Grade 60 (yield strength = 420 MPa) steel

14 THE INDIAN CONCRETE JOURNAL | JUNE 2022
*Corresponding author : Dipti Ranjan Sahoo, Email: drsahoo@civil.iitd.ac.in