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High
performance cement based materials and holistic design
for sustainability in construction (Part I)
R.N.
Swamy
The
cement/concrete industry is faced with two major challenges
- an infrastructure crisis, and a sustainability problem.
Both are worldwide issues with tremendous implications
not only for ourselves but also for the lives of generations
to come. The focus of this paper is to show that a
holistic approach to the formulation and fabrication
of concrete materials with emphasis on durability,
ductility, environment and sustainability can lead
to the development of a large number of eco-friendly
and innovative cement-based construction materials
for a wide range of applications in infrastructure
regeneration and reconstruction. Quality of life is
the one single goal that all humanity wants and aspires
for, and a judicious combination of pozzolanic/cementitious
materials, chemical admixtures, fillers, fibres and
other appropriate constituents can meet the insatiable
demand for basic infrastructure facilities and at
the same time contribute to sustainable growth with
the least damage to our environment. The paper illustrates
this philosophy of manufacturing and designing sustainable
concrete materials for durability rather than for
strength with various examples such as fly ash/slag
concrete, high volume fly ash concrete, structural
lightweight aggregate concrete, low energy-cements,
and fibre reinforcement. It is also shown that the
philosophy of holistic design with emphasis on material
stability, structural integrity and ductility can
successfully meet the challenges of the infrastructure
crisis and sustainable development of the concrete
industry.
Modelling
of masonry infill walls for nonlinear static analysis
of buildings
Amlan
K. Sengupta and Asokan A.
In
the seismic analysis of a framed building with masonry
infill walls, it is necessary to model the effect
of the walls on the lateral stiffness, strength and
ductility of the building. The equivalent strut method
is a convenient method for modelling the walls. Out
of the two approaches of equivalent strut method,
the one based on elastic analysis is suitable for
linear methods of seismic analysis such as equivalent
static and response spectrum methods. The approach
based on ultimate load is suitable for nonlinear methods
of seismic analysis such as pushover analysis. The
present study proposes a nonlinear axial load versus
deformation behaviour for the equivalent strut to
be used in conjunction with a pushover analysis.
Fuzzy
lifetime prediction of reinforced concrete structures
subjected to chlorides
Giuseppe
Carlo Marano, Giuseppe Quaranta and Sara Sgobba
Pitting
corrosion of steel bars is a process that strongly
jeopardises the durability of reinforced concrete
structures exposed to chlorides. This is a problem
widely studied in order to evaluate structural life.
Nevertheless, the proper treatment of the noteworthy
sources of uncertainty, that affect the numerical
values of geometrical and mechanical structural parameters,
is still an open question. Such properties, in fact,
cannot be considered as deterministic quantities.
In many real problems, very few certain data are available
and new non-probabilistic procedures need to be defined
to perform lifetime estimation. In the present study,
parameters are modelled using fuzzy set theory and
a time-dependent fuzzy safety factor is defined in
order to indicate how distant the critical chloride
front is from the bars. Moreover, the study provides
a more proper mathematical analysis of chloride penetration
into concrete and an improved calibrating procedure
to estimate sampling model parameters, also accounting
time variability. The analysis confirms that the application
of oversimplified Fick's solutions leads to substantial
conceptual errors in service lifetime estimation.
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