The first paper of this issue, "Analysis of Anchorage Zone by Finite Element
Method on Windows Nt Cluster", by the authors, P K Gupta and R N Khapre,
deals with the anchorage zone of a prestressed post-tensioned concrete
beam. The problem has been analyzed by finite element technique using cluster
approach of computing. Three parallel solvers of Gauss-Seidel Method (GES), Gauss
Elimination Method (GEM) and Matrix Inversion Method (MIM) have been used on the
cluster to achieve reduction in computational time for obtaining solution of system of
linear equations. The performance of these solvers is compared and the most efficient
one has been utilized in the finite element analysis. The
FEM software has been developed on Windows NT platform to obtain solution. The efficiency of the performance
of these solvers has been compared. For the problem analyzed, it is found that
the matrix inversion method is the most efficient of the three parallel solvers and
it gives highest speed and takes minimum computational time. The significant
finding of this work is that employing three to five computers is most efficient, but it
is dependent on the size of the finite element mesh. Excessive increase in the
number of computers results in increase of total time.
The next paper, "Boundary Element Analysis of Elastic Line
Inclusions", by Mohammed Ameen, deals with modeling of elastic line inclusions in a
two-dimensional elastic continuum of finite extent using boundary element method. The previous
works, as reported in the literature, have dealt with elastic line inclusion by replacing it
with rigid inclusion so as to reduce the complexity of the problem. In this work, a
boundary integral formulation with the elasticity of the line inclusion is accurately
modeled. The elastic continuum is discretized using the boundary element method,
whereas the line inhomogeneity is modeled using linear and quadratic interpolation
element. A linearly elastic, homogeneous, isotropic two-dimensional continuum
matrix, with a few embedded linearly elastic line inclusions, has been considered for analysis.
The formulations have been developed and applied to a problem of fiber composite
under uniaxial loading. Another example demonstrated is a simply supported concrete
beam with tension and compression reinforcement. Numerical results obtained
demonstrate the validity and usefulness of the above method.
Unreinforced Masonry (URM) infills are invariably used in all parts of the
world to fill up the space between columns in framed buildings. This is due to their
low cost, ease in construction and good sound and heat absorption properties. But
safety of these infills under seismic forces is a major problem. They are subjected to
inplane forces due to inter-storey drift and out-of-plane forces due to floor
acceleration. Their behavior under such excitations have been observed in high rise
framed structures. Base isolation is a good tool to control inter-storey drift and
floor acceleration at the same time. Base isolation tries to separate the foundation
from the superstructure so that minimum earthquake forces are transmitted to
the superstructure and thus the vibration of the structure is controlled. In the
third paper, "Efficacy of Base Isolation for Seismic Safety of URM Infills in RC
Frame Buildings", by the authors Yogendra Singh, Samik Chakraborty and Ratnesh
Kumar, explore the efficacy of base isolation for achieving desired seismic response of
URM infills. A procedure for base isolation system using URM infill in framed building
has been outlined. Two buildings have been studied and their dynamic
characteristics, seismic performance, inter-storey drift and peak floor acceleration have been studied.
The fourth paper, "Free and Forced Vibration Interactive Analysis of a
Framed Structure Under Varying Soil Medium", by Kumar Venkatesh, Y K
Gupta and Alok Athaley, deals with the interactive analysis for free and forced vibration of a
framed structure, including soil medium. The properties of soil on which a structure
stands plays a significant role in its dynamics response. In this analysis, the authors
have calculated the dynamic response under varying soil properties. The finite
element technique has been employed for estimation of response, including soil
interaction effect. The soil continuum and raft foundation on which the structure is assumed
to be founded have been discretized using four-noded isoparametric element
and superstructure by two-noded beam elements. With this idealization, the free
vibration under varying soil conditions have been studied. Similarly, forced vibration effect
has been studied in terms of stress and strain developed. The study of the example
problem concludes that variation of Young's modulus of soil effectively influences the
frequency response of framed structure, whereas variation of Poisson's ratio of soil has
modest influence frequency. Free vibration analysis of the structure consists of
horizontal, vertical and rocking mode of vibration, whereas in non-interactive case
horizontal mode is predominant. Variation of soil properties influences significantly the
stresses at soil foundation interaction as compared to structure foundation interaction.
Young's Modulus of soil plays a key role in static and dynamic behavior of structure as
compared to Poisson's ratio. These findings are significant and would help in practical application.
The next paper, "Structural Properties of Polypropylene Fiber Reinforced
Concrete", by K Saravana Raja Mohan, P Jayabalan and A Rajaraman,
deals with strength of concrete reinforced with fly ash and polypropylene fiber. Such studies have
been reported by various researchers with varying results. Fly ash has been used as a
partial substitute in concrete mix because of its easy availability. The authors report
that addition of fly ash reduces the strength of concrete and to compensate for the loss
of strength, polypropylene fiber has been introduced. The fly ash has been varied from
0-30% and fiber content from 0-0.60% in the mix. It has been found that the loss
in strength due to addition of fly ash can be compensated with the addition
of polypropylene fiber. The authors conclude that fly ash and polypropylene fiber
mixed concrete shows a better performance than ordinary concrete. From the results
obtained, it appears that 15% of fly ash by weight of cement and 0.15% of fiber by weight
of concrete produce a maximum compressive strength after 7, 14 and 28 days as
25.25 N/mm2, 24.25 N/mm2 and 26.00
N/mm2 respectively. It means strength
reduction takes place for 14 days and there is not much increase in strength between 7 days
and 28 days. From the results reported, no definite conclusion can be arrived at and
more work needs to be done for any specific recommendation for practical application.
-- Satyendra P Gupta
Consulting Editor
