07-01-2014, 04:57 PM
Shear Resistance of High Strength Concrete Beams Without Shear Reinforcement
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ABSTRACT
The use of high strength concrete in major constructions has become obligatory, whose
mechanical properties are still at a research phase. This paper deals with the review of available
data base and shear models to predict the shear strength of reinforced concrete beams without
web reinforcement. An attempt has been made to study shear strength of high strength concrete
beams (70 Mpa) with different shear span to depth ratios (a/d = 1, 2, 3 & 4) without web
reinforcement and compare the test results with the available shear models. Five shear models
for comparison are considered namely, ACI 318, Canadian Standard, CEPFIP Model, Zsutty
Equation and Bazant Equation. The results revealed that the most excellent fit for the test data is
provided by Zsutty’s Equation and a simplified equation is proposed to predict the shear capacity
high strength concrete beams without shear reinforcement.
Introduction
Use of high strength concrete in construction sector, has increased due to its improved
mechanical properties compared to ordinary concrete. One such mechanical property, shear
resistance of concrete beams is an intensive area of research. To Estimate the shear resistance of
beams, standard codes and researchers all over world have specified different formulae
considering different parameters into consideration. The parameters considered are varying for
different codes and researchers leading to disagreement between researchers, making it difficult
to choose an appropriate model or code for predicting shear resistance of reinforced concrete.
Therefore an extensive research work on shear behavior of normal and high strength concrete is
being carried out all over the world. The major researchers include Bazant Z.P. [1], Zsutty T.C,
[2] Piotr Paczkowski [3], JinKeun Kim [4], and Imran A. Bukhari [5] and many more.
Estimation of shear resistance of high strength concretes is still controversial therefore it’s a
thrust area for research.
Research Significance
This paper provides the test data related to behaviour of HSC beams in shear. The data is useful
for developing constitutive models for shear response of structural elements where high strength
concrete is used.
Experimental Programme
Eight reinforced high strength concrete beams were cast and tested, under two point loading
varying the shear span to effective depth ratio (a/d). The test specimens are divided into four
series. Each series consisted of two high strength concrete beams with out shear reinforcement
with a/d ratio 1, 2, 3 & 4. For all the series, the parameters viz., concrete proportions and
percentage of longitudinal steel were kept constant.
Conclusions
With the discussion on shear models and the experimental studies conducted on HSC beams
without shear reinforcement the following conclusions can be drawn:
· The prediction of shear capacity of High strength concrete beams without shear
reinforcement using the shear equations (Eqs 1 to 6) listed in this paper with a/d ratio is
less than 2.0, a separate equation has to be used as there is remarkable difference between
experimental values and predicted values and for a/d ratio more than 2.0, the available
equations satisfactorily predict the shear capacity of the beams.
· The equation (Eq. 8) stated above includes almost all the parameters required to predict
the shear capacity beams without shear reinforcement. Therefore a single simplified
equation can be used to predict the shear capacity of HSC beams with a/d = 1, 2, 3 & 4.