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ARTICLE
Fracture behavior of plain concrete beams – experimental verification of one parameter model
B.K.Raghu Prasad1, Rabindra Kumar Saha1, A.R.Gopalakrishnan1
1 Department of Civil Engineering, Indian Institute of Science, Bangalore, 560012, India.
Structural Longevity 2009, 1(3), 135-154. https://doi.org/10.3970/sl.2009.001.135
Abstract
Several different models have been proposed to characterize mode-I
crack propagation in concrete. The fictitious crack model proposed by Hillerborg et
al. and the blunt crack band theory developed by Bazant & Oh are particularly well
suited for a finite element analysis. The two-parameter fracture model proposed by
Jenq & Shah is found to be applicable only for beams with s/w=4, where s=span
& w=depth of the beam. The general applicability of the model for other testing
configurations is not published. In the present study an experimental verification
of a one-parameter model based on fundamental equation of equilibrium developed
by Ananthan, Raghu Prasad, and Sundara Raja Iyengar to explain the mode - I fracture behavior of notched and un-notched plain concrete beams subjected to three or
four-point bending, also called Softening Beam Model are reported and discussed
in this paper. The influence of structural size in altering the fracture mode from
perfect brittle fracture to plastic collapse is explained through the stress distribution obtained across the un-cracked ligament. The key factor affecting the stress
distribution is found to be the strain softening modulus and is considered to dependent on structural size. Based on large number of experimental results available in
the literature pertaining to the testing of plain concrete beams in either three-point
or four-point bending, an empirical relationship for the determination of process
zone length (L
p) has been developed. With the knowledge of L
p,
the maximum
load P
max can be obtained. It is demonstrated that the model can predict P
max quite
accurately. Here the objective is to experimentally verify the predicted P
max. The
comparison is valid within a range of errors, reasonable in the cementetious materials like concrete. In this model only an inelastic fracture mechanics parameter
‘L
p’ has been used. The parameter L
p has been obtained as a function of the size of
the beam and also softening modulus in order to consider the effect of softening on
the tensile stress-strain behavior of concrete. Further, the P
max predicted by the one
parameter model as obtained for mode-I failure has been experimentally verified
to see how far it is valid for mixed mode type of failure. Since a very few experimental investigations have been so far carried out to study the fracture behavior of
concrete under mixed mode condition, the present experimental program is carried
out, so as to obtain a wide range of test results pertaining the mixed mode fracture
of concrete.
Keywords
Cite This Article
Prasad, B., Saha, R. K., , A. (2009). Fracture behavior of plain concrete beams – experimental verification of one parameter model.
Structural Longevity, 1(3), 135–154. https://doi.org/10.3970/sl.2009.001.135