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Reliability Analysis Of A Prestressed Concrete Beam
CHAPTER ONE -- [Total Page(s) 2]
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CHAPTER ONE
INTRODUCTION
1.1 PREAMBLE
Prestressed concrete beam
is one of the most widely used construction element in bridge projects
around the world. It has rent itself to an enormous array of structural
applications, including buildings, bridges, nuclear power vessels,
Television towers and offshore drilling platform (Antonie,2004).
Prestressing
involves inducing compressive stresses in the zone which will tend to
become tensile under external loads. Thesecompressive stresses
neutralize the tensile stresses so that no resultant tension exists (or
in only very small values). Cracking is therefore eliminated under
working load and all of the concrete may be assumed effective in
carrying load. Therefore lighter sections may be used to carry a given
bending moment and over much longer spans than reinforced concrete.
The
prestressing force also reduces the magnitude of principal tensile
stress in the web so that thin webbed I sections may be used without the
risk of diagonal tension failures and with further savings in self
weight.
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The prestressing force has to be produced by high
tensile steel and it is necessary to use high quality concrete to resist
the higher compressive stresses that are developed(Mosley and Bungey,
2002).
In the design and construction of the prestressed concrete,
there are many sources of uncertainties which are put into consideration
during the construction in order for the structure to serve its
intended purpose. Consequently, structures must be designed to serve
their functions with a finite probability of failure (Nowak and Colins,
2002).
In order to treat these uncertainties in the construction
processes of the prestressed concrete, reliability analysis comes into
play. Reliability is the probability that the structure will perform its
required function without failure under a specified limit state during a
specified reference period (Thoft-Christensen and Baker, 1982). The
probability of structural failure from all possible causes is
inevitable. However, the uncertainties and their significance on the
structural safety and performance can be analyzed systematically only
through methods of probability.
CHAPTER ONE -- [Total Page(s) 2]
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ABSRACT - [ Total Page(s): 1 ]The Reliability Analysis of a Prestressed Concrete Beam (PCB) was presented using First Order Reliability Method and Eurocode 2 procedures to carry out the analysis. The results show that the safety of the PCBin bending decreasedfrom 2.9 to 1.0 and 3.1 to 2.6 as prestress force and the depth from the extreme compressive fiber to the neutral axis of the beam increased from 20kN to 100kN and 150mm to 350mm respectively, therefore the PCB is safer at low prestress force and depth to the bottom laye ... Continue reading---
