Abstract:
It is a common practice in Bangladesh to design
buildings in reinforced concrete frame ignoring the
composite actions of wall-beam. Due to the ignorance of this
composite action of wall-beam a considerable waste of
materials result in building through under-utilazation.
Although the concept is used extensively in many countries
of the world, its optimum utilazation has been restrained to
some extent due to the lack of proper investigations in the
area. The previous investigations were mainly confined in
the laboratory and very limited theoretical investigation
based on finite element method was performed considering the
brickwork as homogeneous material. This type of macro level
model is suitable for the macro study but incapable of
modeling local behaviour at the region of beam and wall ends
where the stress gradients are very high and the fracture
process is complex.
, A project therefore has been undertaken in the Dept. of
Civil Engineering ,which involves both experimental and
theoretical investigations of the problem. The present study
is a part of this on-going study which involves the
development of linear elastic finite element model to study
the composite action of wall-beam structures. Isoparametric elements have been used to model the bricks, mortar joints,
supporting beams, and the interface elements in between the
wall and the beam. The brickwork has been modeled both as a
homogeneous material or nonhomogeneous material (Bricks and
joints as different materials).The model is very useful in
predicting. the local behaviour of the regions where the
stress gradients are very high.
A series of analyses of a number of wall-beam
structures with different height to span ratios, sizes of
the beam, different stiffness parameters and different
modular ratios have been made in this study. Particular
emphasis has been given to the variation of shear stress,
vertical stress, and the bending moment in the beam of the
wall-beam structures. From this parametric study it has been
found that the maximum moment in the beam occurs at about
1/15th of the span from the supports rather than at midspan.
Whereas the tension attains its maximum value at or near the
midspan. It was also found that the shear stress along the
wall-beam interface is parabolic for lower values of
relative stiffness parameter and the spread of the shear
stress along the length of the beam is twice that of the
vertical stress.
