Abstract:
Building structures designed by limit state approach may have adequate strength but, they
exhibit excessive deflection and excessive crack widths. This study focuses on
serviceability of reinforced concrete beams using finite element approach. The effects of
span to depth ratio, comparison of computed deflection with allowable limits,
reinforcement ratio, steel grade and concrete grade computed based on various design
standards is studied. The design standards include, EBCS-2 (1995), ACI 318 (2002), EC2
(2004) and BS 8110 (1997). The analytical computations were performed with the
commercial general finite element method Abaqus software which incorporates linear and
nonlinear behavior of reinforced concrete beams. Hand calculations are performed with
regard to design codes. The accuracy of the model is verified with laboratory results
which are taken as secondary data. In the finite element model three sample beams were
modeled by using concrete damage plasticity at mesh sizes of 50mm to obtain load deflection curves. The results of mid span deflections of the three beams were calculated
by the above code standards, and using finite element software Abaqus. The results of
finite element method were more accurate than manual computation of the different
codes. From three samples of beams in sample one the result of ACI code is closer to the
finite element result for long term deflection and for short-term deflection. The result of
EBCS codes, long term-deflection had larger values due to the deflection factor included
in the formula. In the cases of sample two the concrete grade, the steel grades and
young‟s modulus of the beam were changed, and the results of manual computation for
long term deflection for EC-2 was obtained as near to that of the Finite element result.
But for short-term deflection EBCS-21995 result was obtained to be better than the
others. In sample three model, reinforced concrete grade as per Ethiopian most applicable
material properties have been used and the results were compared with that of the finite
element method, and the results were obtained with better values of deflection for the
Finite element approach. service loads increase more than cracking loads, the crack
width becomes wider and number of cracks becomes larger. The crack widths of RC
beam are calculated by four codes. EBCS2,1995 and EC-2 code crack widths results are
smaller than another two of codes.
