The aim of strengthening is to increase the capacity of an existing structural element.  Strengthening can be achieved by;  Replacing poor quality or defective material  Attaching additional load-bearing material  Redistribution of the loading actions

1. STRENGTHENING
MEASURES
PRESENTED BY:
SAFNA.K.A
02-01-2019

2. STRENGTHENING OF RC ELEMENTS
 The aim of strengthening is to increase the capacity of an existing
structural element.
 Strengthening can be achieved by;
 Replacing poor quality or defective material
 Attaching additional load-bearing material
 Redistribution of the loading actions
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STRENGTHENINGMEASURES

3. Load-
bearing
material
High quality
concrete
• UHPC
• Polymer
Modified
Concrete
Reinforcin
g steel bars
Thin steel
plates and
straps
Post-
tensioning
tendons
Using
Composite
elements
such as
Steel W
sections
FRP
composite
materials
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STRENGTHENINGMEASURES

4. FLEXURAL STRENGTHENING OF RC BEAMS
 The critical area for beam under bending stresses is a tension zone of the
RC beam.
 Mostly, the failure initiated by the development of crack.
 These cracks usually start from the bottom of applied load, which
indicates flexural failure.
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STRENGTHENINGMEASURES

5. There are several Flexural strengthening techniques.
Span shortening
Section enlargement
Ferrocement cover
External plate bonding
External post-tensioning
Fiber Reinforced Polymer (FRPs)
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STRENGTHENINGMEASURES

6. STRENGTHENINGMEASURES
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Span Shortening
o Span shortening is accomplished by installing additional supports
underneath existing members.
o Appropriate materials; steel members and cast-in-place reinforced
concrete members.
o Connections can be designed easily using bolts and adhesive anchors.

7. SECTION ENLARGEMENT
 Section enlargement is one of the famous method.
 Section enlargement maybe easier and cheaper compared to other
approaches.
 Enlargement consists of the placement of reinforced concrete jacket
around the existing structural member.
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STRENGTHENINGMEASURES

8. • Increasing of the
load-carrying
capacity
• Increasing of the
stiffness
• Increase in the
concrete member
size obtained after
the jacket
• The need to
construct a new
formwork
Advantages
Disadvantages
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STRENGTHENINGMEASURES

9. FERROCEMENT COVER
 Thin composite material made of cement mortar reinforced with
wire meshes.
 The wire meshes are uniformly distributed in continuous layers.
 The Ferro cement is used to replace the damaged concrete.
 Strengthening with Ferro cement improves:
 Cracking resistance
 Flexural stiffness
 The ultimate loads compared to the original un-strengthened
element.
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STRENGTHENINGMEASURES

10. EXTERNAL PLATE BONDING
 Steel plates or steel flat bars are bonded to the structural elements.
 Widely appear in strengthening of bridge structures.
 The bonding is ensured by:
 The use of epoxy adhesives
 Additional fastening by means of dowels or bolts.
 Disadvantages: it can be applied only to the relatively sound structures
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STRENGTHENINGMEASURES

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STRENGTHENINGMEASURES

12. Roughing
and
cleaning
the
concrete
surfaces.
Coating the
concrete
surfaces
with a
bonding
epoxy
material.
Making
holes in the
concrete
surfaces and
plates.
Putting a
layer of
epoxy
mortar on
top of the
plates with a
5mm
thickness.
Attaching
the steel
plates to the
concrete
using bolts
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STRENGTHENINGMEASURES

13. EXTERNAL POST-TENSIONING
 Effective in increasing the flexural and shear capacity.
 Applied to reinforced and prestressed concrete members.
 The post-tensioning forces are delivered by:
 Standard pre-stressing tendons
 High-strength steel rods
 Usually located outside the original section.
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STRENGTHENINGMEASURES

14. If there are
existing spalls
patching must be
done, because this
repairs must
ensure that the
pre-stressing
forces are
distributed
uniformly across
the section of the
member
The existing
cracks must be
repaired by means
of epoxy injecting
or other known
methods
The tendons are
connected to the
structure at anchor
points, typically
located at the ends
of the member
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STRENGTHENINGMEASURES

15. FIBER REINFORCED POLYMER (FRP)
FRP
High
Strength
• ×10
Steel
Multifuncti
onal
• Suit any
project
Corrosion
Resistance
• Durable
Structure
Light
Weight
• Easy to
install
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STRENGTHENINGMEASURES

16.  FRP is a new class of composite material.

 FRPs are organized in a laminate structure.
 each lamina (flat layer) contains an arrangement of unidirectional
fibers fabrics embedded within a thin layer of light polymer.
 FRP consists of two main components:
 Fibers.
 Resin or Matrix
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STRENGTHENINGMEASURES

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STRENGTHENINGMEASURES

18. Advantages
• Corrosion Resistance
• Lightweight
• Ease of installation
• Less Finishing
• Less maintenance
• Improve Ductility
• They are ideal for external
application
• Anti-seismic behavior
Disadvantages
• High cost
• susceptibility to
deformation under long-
term loads
• Temperature and moisture
effects
• lack of design codes
• lack of awareness
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STRENGTHENINGMEASURES

19. SHEAR STRENGTHENING OF RC BEAMS
 Shear failure is a sudden failure which make it more devastating than
the Flexural failure.
 Shear failure start occurring from the critical section at high shear zone
near support.
 Shear force maximum at support and the diagonal cracks start from
support to applied load.
 Shear strengthening techniques - External anchored stirrups, external
post-stressing, plate bonding using steel plates, FRP .
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STRENGTHENINGMEASURES

20. STRENGTHENING OF RC COLUMNS
 Strengthening of reinforced concrete columns is needed when;
 The load carried by the column is increased due to either increasing
the number of floors or due to mistakes in the design.
 The compressive strength of the concrete or the percent and type of
reinforcement are not according to the codes’ requirements.
 The inclination of the column is more than the allowable.
 The settlement in the foundation is more than the allowable.
 There are many techniques for strengthening RC columns, the most
famous techniques are:
1. RC jacketing
2. Steal Jacketing
3. Using FRP wraps 20
STRENGTHENINGMEASURES

21. JACKETING
 Process of fastening a durable material over concrete &filling the
gap with grout that provide needed performance characteristics.
 The loads applied to the column shall be reduced or eliminated by:
 Putting mechanical jacks between floors.
 Putting additional props between floors.
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STRENGTHENINGMEASURES

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STRENGTHENINGMEASURES

23. STEEL JACKETING
 This technique is chosen when the loads applied to the column will be
increased, and at the same time, increasing the cross sectional area of
the column is not permitted.
FRP WRAPS
 FRP improve the confinement of the RC columns leading to:
• Improving Axial Capacity
• Buckling Resistance
• Bomb Blast Resistance
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STRENGTHENINGMEASURES

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