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Innovative
application of prestressed soil anchors for an underpass
Navneet
Gupta and Vinay Gupta
An
underpass has the distinct advantage of not causing
visual obstruction. In this paper, the authors describe
the salient design and construction features of
the underpass completed recently in Delhi with special
reference to the use of prestressed soil anchors
for the base slab. They conclude that the prestressed
soil anchors offer efficient and economical solution.
Concrete
for hydro-electric projects: Combating alkali-aggregate
reaction
S.C.
Maiti, Raj K. Agarwal and Rajeeb Kumar
Generally
speaking, alkali-aggregate reaction (AAR) is not
a serious durability problem in India. However,
some of the aggregates used in concrete structures
of hydro-electric projects exhibit reactivity. In
a few projects in the country, reactive carbonate
rocks have also been noticed. The authors present
a brief overview of durability aspects of concrete
to be used for structures in hydro-electric projects
with particular reference to steps needed for AAR
mitigation. If alkali-silica reaction is envisaged
in concrete, the authors suggest that the best option
is to use factory-made blended cement (with 25-30
percent Grade I fly ash or with 50-60 percent ground
granulated blast furnace slag), with the parent
ordinary portland cement having alkali content of
less than 0.60 percent as Na20 equivalent. For achieving
high-strength, high-performance and abrasion-resistant
concrete for intake structures and spillways, silica
fume, superplasticiser and fibres can be used in
concrete.
Development
and characterisation of flowable high-calcium fly
ash-gypsum slurry
V.
Revathi and V.L. Narasimha
This
paper presents the development of gypsum-activated
lignite fly ash and the use of this blend as a binder
for controlled low strength material (CLSM). The
CLSM is a combination of high-calcium fly ash, fluro-gypsum,
sand and adequate amount of water. Two mixes of
different fluidity were prepared and evaluated for
various engineering properties such as compressive
strength, plastic properties, CBR value, thermal
conductivity, drying shrinkage and water absorption.
The test results obtained showed that fly ash-gypsum
slurry could provide a low cost and environmental
friendly material for various civil engineering
applications.
Brick-infilled
vierendeel girders as foundation for low-lying,
low bearing-capacity soil terrain
S.
Sundaramurthy and A.R. Santhakumar
The
scarcity of land prevalent in urban areas calls
for utilisation of available low-lying terrains
outside metropolis. These low-lying terrains require
filling with selected earth. Normally, shallow foundation
is a suitable option for low-rise residential buildings.
If the fill warrants a depth of more than 2 m, adoption
of shallow foundation is an arduous task. The problem
gets worse if the virgin soil has poor bearing capacity.
Suitability of various types of shallow foundation
in landfill areas is discussed in this paper. A
practical example is also presented involving adoption
of brick-infilled vierendeel girder foundation system
in a landfill terrain. This system proved to be
superior in strength and stiffness characteristics.
Preliminary
Report: Recent tsunami and earthquake devastation
Source:
NICEE
The Indian Institute of Technology (IIT), Kanpur
organised a reconnaissance study of the affected
areas of the recent earthquake and the tsunami with
a view to document the scientific, engineering and
disaster management lessons from this tragedy. A
total of 13 investigators were divided into six
groups with independent responsibilities: each of
the groups spent about eight days in the field,
during January 1 to January 13, 2005.
Tsunami
Special: An introduction to tsunami in the Indian
context
Sudhir K. Jain, Anil Agarwal and Amit R. Hirani
Tsunami is a water wave caused due to tectonic activities
under water and travels across oceans with very
high speed and can inflict great damage to life
and property at the shores. The recent Sumatra earthquake
of magnitude 9.0 triggered the most devastating
tsunami of the recorded history causing a death
toll of more than 150,000. Many regions around the
globe, especially the Pacific Ocean have witnessed
many damaging tsunamis in the past. Countries around
the Pacific Ocean have developed an early warning
system that has been very effective for the last
50 years. Tsunamis have not been so frequent in
the Indian Ocean, therefore lack of awareness has
been a major cause for the great devastation caused
by the tsunami of 26 December 2004. This feature
gives a brief background about tsunamis.
Case
Study: Partial collapse of a multi-storeyed concrete
structure
D.S. Prakash Rao and K. Sridevi
A part
of a seven-storeyed reinforced concrete framed structure
collapsed even before it was inhabited. Reportedly,
the structure groaned and rumbled for a few weeks
prior to its collapse, but the signs of structural
distress were regarded as inconsequential till a
few columns developed longitudinal cracks and the
bars buckled. A part of the structure collapsed
after a loud groan even as the ground floor beams
on one of the distressed columns were being supported
with steel pipes. The probable sequence of events
leading to the collapse and the causes are discussed
in this paper. Poor estimation of structural loads
coupled with poor construction practices besides
lack of quality control, supervision and expertise
appear to be the causes for the failure.
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