Author Name:- J. Gopi Krishna
Abstract:- In our country many
of the existing reinforced concrete structures are in need of repair or
reconstruction, rehabilitation, because of deterioration due to various factors
like corrosion, lack of detailing, failure of bonding between beam-column
joints, increase in service loads, improper design and unexpected external
lateral loads such as wind or seismic forces acting on a structure, environment
and accident events etc., leading to cracking, spalling, loss of strength,
deflection, etc. Strengthening of existing reinforced concrete structures is
necessary to obtain an expected life span and achieve specific requirements.
The need for efficient rehabilitation and strengthening techniques of existing
concrete structures has resulted in research and development of composite
strengthening systems. Recent experimental and analytical research have
demonstrated that the use of composite materials for retrofitting existing
structural components is more cost-effective and requires less effort and time
than the traditional means. Fiber Reinforced Polymer (FRP) composite has been
accepted in the construction industry as a capable substitute for repairing and
strengthening of RCC structures. The superior properties of (FRP) polymer
composite materials like high corrosion resistance, high strength, high
stiffness, excellent fatigue performance and good resistance to chemical attack
etc., has motivated the researchers and practicing engineers to use the polymer
composites in the field of rehabilitation of structures. During past two
decades, much research has been carried out on shear and flexural strengthening
of reinforced concrete beams using different types of fiber reinforced polymers
and adhesives. A detailed Literature review based on the previous experimental
and analytical research on retrofitting of reinforced concrete beams is
presented. Proposed method of strengthening the RC beam is decided based on the
previous experimental and analytical research. Behaviors of retrofitted
reinforced concrete beams with externally bonded CFRP with various types of
resins (Epoxy, Orthophthalic Resin (GP), ISO resin) after initial load (60 %
control beam) is investigated. Static load responses of all the beams under two
point load method had evaluated in terms of flexural strength, crack
observation, compositeness between CFRP fabric and concrete, and the associated
failure modes.
Keywords: Fiber Reinforced Polymer (FRP), CFRP fabric,
reinforced concrete structures
I. Introduction
Concrete is the most widely used man-made
construction material in world. It is obtained by mixing cementing materials,
water and aggregates, and sometimes admixtures is required proportions.
Concrete has high compressive strength, low cost and abundant raw material, but
its tensile strength is very low. Reinforced concrete, which is concrete with
steel bars embedded in it. Concrete is an affordable material, which is
extensively used throughout in the infrastructure of nation’s construction,
industry, transportation, defense, utility, and residential sector. The
flexibility and mould ability of this material, its high compressive strength,
and the discovery of the reinforcing and prestressing techniques which helped
to make up for its low tensile strength have contributed largely to its
widespread use.
Reinforced
concrete structures often have to face modification and improvement of their
performance during their service life. In such circumstances there are two
possible solutions. The first is replacement and the other is retrofitting.
Full structure replacement might have determinate disadvantages such as high
costs for material and labour, a stronger environmental impact and
inconvenience due to interruption of the function of the structure e.g. traffic
problems. So if possible, it is often better to repair or upgrade the structure
by retrofitting. Retrofitting methods is shown in figure 2.1.1. In recent years
repair and retrofit of existing structures such as buildings, bridges, etc.,
have been quite prevalent among the most important challenges in Civil
Engineering.
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