1
1
1
Stephanos E. Dritsos
Department of Civil Engineering
,
University of Patras
Differences in the design of interventions
according to EC8 part 3 and the Greek CSI
COUNCIL OF EUROPE/EUROPEAN CENTRE ON PREVENTION AND FORECASTING OF EARTHQUAKES (ECPFE)
EARTHQUAKE PLANNING AND PROTECTION ORGANIZATION (EPPO)
ATHENS, APRIL 12/2013
Implementation of EC8 part 3
:2005.
Assessment and
interventions on buildings in earthquake prone regions
WORKSHOP
:
2
2
2
Interfaces
Retrofitting of Buildings
Retrofitting
between existing
–
new elements
Greek Code
Greek Code
Eurocode
Greek Code
Retrofitting
of existing elements
(strengthening)
by adding new elements
(of the whole structure)
3
3
CONTEXT STRUCTURE
(CONCEPT)
EUROCODE
GREEK CODE
Types of
strengthening
offered (in flexure,
shear, ductility)
Specific techniques
are adopted
Alternative and
appropriate techniques
are proposed
Specific deficiencies are
diagnosed and purpose of
intervention is decided
Moreover, Greek Code a much more detailed document
4
4
BASIC DESIGN CONSIDERATIONS
Influence of Interface Connection
Repaired/Strengthened Element
Multi
–
Phased Element
Composite Element
INTERFACES
GCSI
:
5
5
5
VERIFICATION OF A SUFFICIENT CONNECTION
BETWEEN
CONTACT SURFACES
d d
S R
V V
d d
interface interface
S R
Interface
Shear
Force
Interface
Shear
Resistance
Under
specific
construction
conditions
(measures),
verification
may
not
be
necessary
6
6
6
6
6
6
F
δ
F
y,μ
F
y,ε
Monolithic Element
Strengthened Element
F
res,μ
F
res,ε
δ
y,μ
δ
y,ε
δ
u,μ
δ
u,ε
Κ
μ
Κ
ε
y,
ε
r
y,
μ
F
Κ =
F
y,
ε
δy
y,
μ
δ
Κ =
δ
ε
κ
μ
Κ
Κ =
Κ
u,
ε
δu
u,
μ
δ
Κ =
δ
INFLUENCE OF INTERFACES
CAPACITY CURVES
Deformation
Action Effect
7
7
7
MONOLITHIC BEHAVIOUR FACTORS
For
the
Stiffness
:
k
the stiffness of the strengthened element
k
the stiffness of the monolithic element
For
the
Resistance
:
r
the strength of the strengthened element
k
the strength of the monolithic element
(EI)
strength
en
ed
= k
k
(EI)
M
R
strengthened
= k
r
R
M
For
the
Displacement
:
y
the displacement at yield of the strengthened e
lement
k
the displacement at yield of the monolithic ele
ment
y
the ultimate displacement of the strengthened
element
k
the ultimate displacement of the monolithic el
ement
δ
i
,
strengthened
= k
δ
i
δ
i,M
8
8
8
Infilling
Frames
•
Addition
of
simple
“
infills
”
•
Conversion
of
frames
to
shear
walls
•
Strengthening
of
existing
masonry
infills
•
Addition
of
bracing
.
Conversion
of
frames
to vertical trusses
Construction of new lateral shear walls
GREEK CSI
:
(Reinforced or unreinforced concrete walls,
reinforced or unreinforced masonries)
(
Shotcreting
reinforced
layers)
(By steel or RC elements)
Reinforced concrete walls
and jackets
STRENGHTENING THE WHOLE STRUCTURE
9
9
9
9
Adding Simple Infills
Addition
of
walls
from
:
a
)
Unreinforced
or
reinforced
concrete
(
cast
in
situ
or
prefabricated
)
b
)
Unreinforced
or
reinforced
masonry
No
specific
requirement
to
connect
infill
to
the
existing
frame
Modelling
of
infills
by
diagonal
strut
Low
ductility
of
infill
.
Recommended
m
≤
1
,
5
WARNING
Additional shear forces are induced in the columns and beams of the frame
GCSI
:
10
10
10
10
Strengthening of existing masonry infills
Reinforced
shotcrete
layers
applied
to
both
sides
of
the
wall
Minimum
concrete
thickness
50
mm
Minimum
reinforcement
ratio
ρ
vertical
=
ρ
horizontal
=
0
,
005
Essential
to
connect
both
sides
by
bolting
through
the
wall
No
need
to
connect
to
the
existing
frame
as
it
is
an
infill
All
new
construction
must
be
suitably
connected
to
the
existing
foundation
GCSI
:
11
Reinforced walls are constructed from one column to another enclosing the
frame (including the beam) with jackets placed around the columns. Note,
all new construction must be suitably connected to the existing foundation
Frame Encasement
New column
Existing column
New wall
New column
Existing column
New wall
conversion of frames to shear walls
GCSI
:
12
12
12
Addition of New External Walls
Schematic arrangement of connections between
existing building and new wall
GCSI
:
13
13
13
Addition of a Bracing System
GCSI
:
14
14
14
OBJECTIVES
GREEK CODE (2012)
DESIGN OF
INTERVENTIONS
EC 8
-
PART 3 (2005)
CAPACITY MODELS FOR
STRENGTHENING
1
Verification of the
interface connection
Yes
No
2
Interventions in critical
regions of linear
structural members
Yes
Yes
3
Interventions to frame
joints
Yes
No
4
Interventions on shear
walls
Yes
No
5
Interventions on
foundation elements
Yes
No
6
Frame encasement
Yes
No
7
Construction of external
new shear walls
Yes
No
Interfaces
Strengthening
of elements
Retrofitting
whole
structure
15
15
15
GREEK CSI (2012)
EC 8 PART 3 (2005)
8.2.1.1
Local repair of a damaged member region
-
-
8.2.1.2
Restoration of insufficient lap splice length of the
reinforcement
A.4.3.3
A.4.4.4
Clamping of lap
-
splices
by FRP wrapping
8.2.1.3
8.2.1.4
Interventions to strengthen the tension or
compression zone against flexure with axial force
-
-
8.2.1.5
Column jackets with the objective of simultaneous
strengthening in the tension and compression zone
A.4.2.2
Enhancement of strength,
stiffness and deformation
capacity
by concrete jackets
8.2.2.1
8.2.2.2
Interventions to increase the shear capacity
a) inadequacy of the compression struts
b) inadequacy of transverse reinforcement
A.4.3.2
A 4.4.2
Enhancement of shear strength
(inadequacy of transverse
reinforcement)
by steel or FRP wrapping
8.2.3
Interventions to increase local ductility
A.4.2.2
A.4.4.3
Enhancement of strength,
stiffness and deformation
capacity
by concrete jackets
Confinement action
by
FRP
wrapping
8.2.4
Interventions to increase the stiffness
A.4.2.2
Enhancement of strength,
stiffness and deformation
capacity
by concrete jackets
Interventions in Critical Regions of Linear Structural Members
16
16
16
EC 8
-
3
ANNEX A (informative)
:
REINFORCED CONCRETE STRUCTURES
CAPACITY MODELS FOR STRENGTHENING
Concrete
Jacketing
Steel
Jacketing
FRP
Plating
and
Wrapping
17
17
17
Concrete
Jacketing
Proposed to enhance the strength
stiffness and deformation capacity
Correlation with a monolithic equivalent
R
0,9V
*
R
v
*
y y
M M
*
y y y
1,05 or 1,20
*
u u
EC 8
-
3
if roughened
if not
18
18
18
Steel
Jacketing
(a)
Increase
shear
strength
(b)
Prevent
lap
-
splice
failure
Only
construction
detailing
to
:
EC8
-
3
(in
case
of
inadequate
shear
reinforcement)
19
19
19
FRP
Plating
and
Wrapping
(a)
Increase
shear
strength
(b)
Increase
ductility
of
critical
regions
(c)
Prevent
lap
-
splice
failure
to
:
EC8
-
3
(more
extended
part
-
6
pages
out
of
9
)
20
20
NECESSARY AMOUNT OF CONFINEMENT
for a target curvature ductility
,t r
Applied
to
circular
and
rectangular
cross
sections
2
2
1,5
0,4
cu
x c
ju
f I f
(A.34)
,t ar
x
,
I
j
f f
f f ju f j j
c
f
4t 2t
1 1 1
f E f f
2 2 2 D f D
j
f
s s w
c c
f
f
2t
k 0,5 k
f D f
2
1,5
ju
,t r
s w
2
ave cu
1,25 k
First choice
EC
8
-
3
:
(A.34)
Confinement
pressure
s
f k f
s
k 1,0
c
s
2R
k
D
circular
rectangular
In
practice
s
k 0.2 0.35
21
21
Second
choice
Applied
only
to
rectangular
cross
sections
wx
0,35
v 0,225
s
um c
el
L
1
0,016 0,3 f 25
h
EC
8
-
3
:
u
u,y u
y
f f
w
wx w
(1 0,35 )
2
where
f,e
f
c
f
0,35
f
v 0,225
s
um c
el
L
1
0,016 0,3 f 25
h
where
f
f,e u u
c
f f (1 0,7f )
f
p p
1
3 (1 0.5 )
1
e.g.
p
p
s
L
for 0.10 3.5 2.5
L
p
p
s
L
for 0.20 2 1
L
22
22
GREEK CODE
cu,c
sy
2,2 v
CFRP
:
2
2
cc
cu,c w
c
f
0,0035 0,0035(1,125 1,25a )
f
y
sy
s
f
E
c
N
v
bhf
Yield
strain
Normalized
axial
load
Approximate
procedure
23
23
Therefore,
w
f a
However,
quite
different
relationships
are
proposed
with
different
influences
from
crucial
parameters
.
w
...a
w
w
1 0.35
2
...25
2
w
...
EC8
-
3
EC8
-
3
GCSI
In all Expressions
24
24
circular
D
rectangular
b
j j j
w
2
con c c
V f f
Dt
V f ( D/4) f
Collars
or
stirrups
A
t
S
j
w
c
f
4t
b f
Assume
Φ
8
/
100
stirrups
in
a
300
x
300
mm
cross
section
or
circular
D
=
300
mm,
f
ck
=
14
-
16
MPa,
f
cm
=
20
MPa
eq
50
t 0,5mm
S 100
w
4 0,5 500 10
0,2
300 20 6
If
10/75 0,4
w
For
an
CFRP
jacket
t
=
1
mm
w
4 3000
2
300 20
j
c
f
4t
D f
j j j j
0,015 f E 200.000 0,015 3000MPa
Volumetric
Confinement
Ratio
ω
w
w
maxa?
A
collar
cross
section
area
25
0
5
10
15
20
25
30
0
0.5
1
1.5
2
2.5
ω
w
μ
φ
GCSI
EC8(1)
EC8(2)
300mm
300mm
50mm
20
cm
f MPa
4 20,500
S
1.4%
ju
3.0
L m
1.5
s
L m
0.25
v
26
500mm
500mm
50mm
20
cm
f MPa
8 20,500
S
1.4%
ju
3.0
L m
1.5
s
L m
0
5
10
15
20
25
0
0.5
1
1.5
2
2.5
ω
w
μ
φ
GCSI
EC8(1)
EC8(2)
0.25
v
27
0
5
10
15
20
25
30
0
0.5
1
1.5
2
2.5
ω
w
μ
φ
GCSI
EC8(1)
EC8(2)
300mm
300mm
50mm
20
cm
f MPa
4 20,500
S
1.4%
ju
3.0
L m
1.5
s
L m
0.50
v
28
500mm
500mm
50mm
20
cm
f MPa
8 20,500
S
1.4%
ju
3.0
L m
1.5
s
L m
0
5
10
15
20
25
0
0.5
1
1.5
2
2.5
ω
w
μ
φ
GCSI
EC8(1)
EC8(2)
0.50
v
29
0
5
10
15
20
25
30
0
0.5
1
1.5
2
2.5
ω
w
μ
φ
GCSI
EC8(1)
EC8(2)
0.75
v
300mm
300mm
50mm
20
cm
f MPa
4 20,500
S
1.4%
ju
3.0
L m
1.5
s
L m
0.75
v
30
0
5
10
15
20
25
0
0.5
1
1.5
2
2.5
ω
w
μ
φ
GCSI
EC8(1)
EC8(2)
500mm
500mm
50mm
20
cm
f MPa
8 20,500
S
1.4%
ju
3.0
L m
1.5
s
L m
0.75
v
31
31
EXPERIMENTAL DATA FOR CONCRETE JACKETING
(UNIVERSITY OF PATRAS)
32
32
-150
-100
-50
0
50
100
150
-200
-150
-100
-50
0
50
100
150
200
Δύναμη
(KN)
Οριζόντια μετακίνηση (mm)
I2
-150
-100
-50
0
50
100
150
-200
-150
-100
-50
0
50
100
150
200
Δύναμη (mm)
Οριζόντια μετακίνηση (mm)
I4
O
F2
F4
R
D
RD
NT
M
Displacement (mm)
L
ateral force
(kN)
Displacement (mm)
L
ateral force
(kN)
L
ateral force
(kN)
Displacement (mm)
Displacement (mm)
Displacement (mm)
Displacement (mm)
L
ateral force
(kN)
L
ateral force
(kN)
L
ateral force
(kN)
Displacement (mm)
Displacement (mm)
Displacement (mm)
L
ateral force
(kN)
L
ateral force
(kN)
L
ateral force
(kN)
NTP
33
33
-200
-150
-100
-50
0
50
100
150
200
-150
-100
-50
0
50
100
150
Displacement (mm)
Load (kN)
R1
R2
D1
D2
RD1
RD2
W1
W2
Mo
O
Load Against Displacement Envelope Curves for All Tested Specimens
(Bousias et al. 2004, Vandoros and Dritsos, 2006b, Vandoros and Dritsos, 2006c)
34
y,GCSI y,exp
?
Total data (42 specimens)
,exp GCSI
y y
k?if
(Kappos et al, EPPO report 2012)
y
k 1.26
GCSI
:
y
k 1.25
EC8
-
3
:
y
k 1.05 or 1.20
35
35
RECENT
PROJECTS
FUNDED
BY
EPPO
On
the
specific
subject
of
Ch
.
8
of
GCSI
:
Design
of
Interventions
(Budget
150
.
000
Euro)
1.
Investigation
of
the
behaviour
of
old
type
RC
columns
strengthened
by
concrete
jackets
.
(Aristotle
University
of
Thessaloniki)
.
2.
Investigation
of
the
behaviour
of
RC
columns
after
restoring
insufficient
reinforcement
lap
splice
lengths
.
(Aristotle
University
of
Thessaloniki)
.
3.
Experimental
investigation
of
shear
strengthening
of
beams
in
their
support
areas,
under
seismic
actions
.
(Aristotle
University
of
Thessaloniki)
.
4.
Experimental
investigation
of
the
behaviour
or
RC
frames
strengthened
by
infilling
with
new
concrete
walls
.
(Thessali
University)
5.
Experimental
investigation
of
4
-
floor
RC
frames
strengthened
by
infilling
with
new
concrete
walls
.
(University
of
Patras)
Also,
5
more
projects
funded
(Budget
150
.
000
Euro)
on
the
topic
of
strengthening
RC
buildings
with
one
or
more
soft
storeys
.
36
36
CONCLUDING REMARKS
EC
8
-
3
and
the
GCSI
deal
with
the
crucial
issue
of
the
seismic
risk
of
existing
buildings
and
try
to
give
guidance
for
assessment
and
retrofitting
However,
when
specifically
looking
at
the
design
of
interventions,
two
crucial
differences
can
be
identified
Concept
Detail
and
topics
covered
-
From
the
three
main
parts
of
the
Greek
Code
:
a)
verification
of
force
transfer
at
interfaces,
b)
strengthening
of
elements,
c)
strengthening
of
the
whole
structure,
only
b
is
considered
by
EC
8
-
3
.
-
Even
when
common
objectives,
different
analytical
expressions
are
provided
leading
to
different
outcomes
.
-
In
the
specific
objective
of
“interventions
to
increase
local
ductility”,
the
GCSI
is
found
to
be
more
conservative
in
comparison
to
EC
8
-
3
and
is
drastically
influenced
by
the
normalized
axial
load
.
-
More
research
is
needed
not
only
in
the
objectives
where
the
two
Codes
are
contradictory
but
also
in
the
areas
that
EC
8
-
3
does
not
touch
while
the
GCSI
attempts
to
provide
guidance,
however
with
extremely
limited
experimental
existing
data
.
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