JEC COMPOSITES MAGAZINE - Issue #111 - March 2017 - Special JEC World - o - 100

CONSTRUCTlON
regulations

Seismic retrofitting of reinforced concrete
structures using FRP: French guidelines

EMMANUEL FERRIER, Professor,
LAURENT MICHEL, Associate Professor,
Laboratory of composites materials
for construction, University of
Claude Bernard Lyon 1
M. QUIERTANT, Researcher, IFSTTAR

In various countries, including France, the regulations concerning buildings and
civil engineering structures contain recommendations aimed at achieving acceptable seismic performance; that is, the structures designed must withstand
minor earthquakes without damage, moderate earthquakes with minimum
non-structural damage and major earthquakes without collapsing. The seismic
recommendations proposed in building regulations were thus updated over
the years to achieve this aim.

n France, the new earthquake zone map
and regulatory changes resulting from
Eurocode 8 (EC 8) have contributed to
defining the performance objectives of new
structures.
For existing structures, at least in certain
cases, reinforcement is required to reduce
seismic risks. This concept was introduced in
Eurocode 8 Part 3 and in the implementing
decrees and orders. Seismic retrofitting can
therefore be either voluntary or compulsory. Based on the current construction rate, it
would take one hundred years to completely
replace France's housing stock. Therefore,
the seismic retrofitting of existing structures
appears necessary to ensure the strength of
all building constructions and the safety and
security of people and property. The need to

Fig.1 : AFGC
French Design
guideline for FRP
strengthening

100

reduce the effects of an earthquake on a reinforced concrete structure can involve two different situations:

In the first case, the strategy will consist in treating the problem of a single component whose
probable failure would lead to consequences
on a global level. In the second case, the strategy will be to carry out major works on the
entire structure. In both cases, the retrofitting
works need to be validated on both a technical
and an economic level. Several reinforcement
scenarios are possible: reducing seismic loads
(insulators, dissipators, change of mass) and/
or improving the performance, resistance and/
or rigidity of the structure.

This document presents recommendations for the seismic retrofitting of concrete
structures using fibre-reinforced polymers
(FRP). For more than fifteen years, national
and international research ([1], [2], [3], [4],
[5], [6]) has shown that composite materials (polymer matrix with textile reinforcements) can be used to protect, repair and
reinforce not only reinforced concrete, prestressed concrete, metal and timber structures, but also masonry structural components. Three types of technologies are used
(wet lay-up, adhesive bonding of flat pultruded composites and bag moulding) and
the main materials used are carbon, glass or
aramid fibres combined with an epoxy-type
thermosetting matrix. The performance of
the retrofitted system is essentially related
to the load transfer between the reinforcement and its substrate, by means of adhesive
bonding or confinement.

The retrofitting techniques generally used are
classified according to their purpose and technology:
- Retrofitting by addition (chaining, bracing,
buttressing, etc.);
- Enhancing shock absorption and/or reducing rigidity (isolators, dissipators, etc.);
- Enhancing strength and/or ductility
(sprayed concrete, bonded composites, steel
lining and bracing, etc.);
- Anchoring (floor-chaining, frameworkchaining, foundation-framework).

Research results have been used to draw up
recommendations and design rules in the
case of quasi-static loading, taking serviceability limit state and ultimate limit state
conditions into consideration (ACI 440 [7],
ISIS Canada [8], JCI Japan [9], AFGC [10],
Fib TG9.3 [11], EC8-3). The aim of this document is to provide in-depth information on
the use of materials for the seismic retrofitting of existing structures. These guidelines
are a complement to existing guidelines on
earthquake engineering.

1. The weak points identified are localised and
confined within a particular area;
2. There are many weak points everywhere and
a global approach is necessary.

jec composites magazine / No111 March 2017

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