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Design
solutions for enhancing the fire resistance of high
strength concrete columns
V.K.R.
Kodur
High
strength concrete (HSC) is being increasingly used
in a number of building applications, where structural
fire safety is one of the major design considerations.
Many research studies clearly indicate that the fire
performance of HSC is different from that of normal
strength concrete (NSC) and that HSC may not exhibit
same level of performance as NSC in fire. This paper
discusses the performance of HSC under fire conditions.
A comparison is made of the fire resistance performance
of HSC column with that of NSC column. The various
factors that influence the structural behaviour of
HSC columns under fire conditions are discussed. Data
from earlier experimental and numerical studies is
used to illustrate the impact the concrete (material)
mix design and structural detailing (design) has on
fire performance of HSC systems. Finally, design solutions
are presented for mitigating spalling and enhancing
fire endurance of HSC columns.
A
comparative evaluation of OPC and PPC concretes
Virendra
Raghav Savalia, Praveen Kumar and Surendra Kumar Kaushik
Test
results of an experimental study aimed at investigating
the performance of fly ash based blended cement for
compressive strength, chloride permeability and electrical
resistivity of concrete are presented. Three concrete
mix proportions were made with water to cement ratios
in the range 0.42 to 0.27, each with three different
brands of commercially available PPCs and one OPC.
Significant amounts of increase in the concrete resistivity
and decrease in the chloride permeability of concrete
is observed with the use of fly ash based PPC as compared
to OPC. It is also observed that concrete showing
higher compressive strength may not have good durability
characteristics.
Modelling
of reinforced concrete framed buildings with soft
ground storey : A case study
M.
Koti Reddy, D.S. Prakash Rao and A.R. Chandrasekaran
Natural
frequencies of a seven storey reinforced concrete
framed structure with open stilt floor were determined
by monitoring its ambient vibrations using a triaxial
seismometer and the results were compared with those
of the analytical models. The framed structure was
modelled as bare frame, frame with floor slabs and
with staircase to determine the most appropriate model
to predict its natural frequencies and thereby its
seismic behaviour. The effective modulus of elasticity
of concrete to be used in the analysis was obtained
by matching the experimental and analytical values.
The contribution of staircase and lift well in sharing
the lateral forces due to seismic loading was also
investigated, particularly in the sensitive stilt
floor. Suggestions to improve the performance of the
building by introducing additional structural elements
at stilt floor level without affecting parking requirements
are also included.
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