EMBEDMENT OF STEEL BARS FOR THE SHEAR STRENGTHENING OF CONCRETE ELEMENTS

foulgirlsUrban and Civil

Nov 15, 2013 (3 years and 8 months ago)

74 views


























Figure 4:
Relationship between the applied load versus the loaded
section
deflection

The analysis of
the results
prompts the following remarks
:

(i
)

The

ETS

shear

strengthening

technique

can

convert

a

brittle

shear

failure

in

a

ductile

flexural

failure
.


(ii
)

The

maximum

load

and

the

deflection

capacity

of

the

beams

reinforced

with

conventional

stirrups

were

similar

to

the

values

registered

on

beams

strengthened

with

ETS

bars
.

Thus,

it

was

verified

the

feasibility

of

using

the

ETS

bars

to

correct

construction/design

deficiencies,

strengthening

or

rehabilitation

of

structures

that

become

unsafe

due

to

changes

in

loading,

use,

configuration

or

seismic

actions
.

(
iii)

The

ETS

shear

strengthening

elements

have

higher

protection

against

fire

and

vandalism

acts

than

FRP

systems

applied

according

to

the

E
xternally

Bonded

Reinforcing

or

Near

Surface

Mounted

techniques
.


Conclusions

According

to

the

results

it

was

verified

the

feasibility

of

using

the

proposed

shear

strengthening

technique,

since

shear

brittle

failure

mode

can

be

avoided,

resulting

significant

increases

in

load

carrying

and

deformational

capacities

of

the

strengthened

elements
.

Furthermore,

appreciable

levels

of

residual

strength

after

the

peak

load

were

obtained
.


Acknowledgments

The

first

author

would

like

to

acknowledge

the

National

Council

for

Scientific

and

Technological

Development

(
CNPq
)



Brazil

for

financial

support

for

scholarship

(GDE

200953
/
2007
-
9
)
.

The

research

is

part

of

PTDC/ECM/
73099
/
2006

project

supported

by

FCT
.



0
5
10
15
20
25
30
35
0
30
60
90
120
150
180
210
240
270
S-225-90
o
/ETS-225-90
o

S-300-90
o
/ETS-300-45
o
S-300-90
o
/ETS-300-90
o
ETS-300-45
o
ETS-300-90
o
S-225-90
o
S-300-90
o
Load, F (kN)

Displacement
(
mm
)
3558
c
Reference
Sirrups_300
Stirrups_225
No stirrups_ETS_300_90؛
No stirrups_ETS_300_45؛

Stirrups_300_ETS_300_45؛
Stirrups_225_ETS_225_90؛
Ref.

Stirrups_300_ETS_300_90º
0
5
10
15
20
25
30
35
0
50
100
150
200
250
300
350
400
450
S-225-90
o
/ETS-225-90
o

S-300-90
o
/ETS-300-45
o
S-300-90
o
/ETS-300-90
o
ETS-300-45
o
ETS-300-90
o
S-225-90
o
S-300-90
o

3558
c
Reference
Sirrups_300
Stirrups_225
No stirrups_ETS_300_90؛
No stirrups_ETS_300_45؛

Stirrups_300_ETS_300_45؛
Stirrups_225_ETS_225_90؛
Ref.
Load, F (kN)
Displacement
(
mm
)

Stirrups_300_ETS_300_90º

University of Minho


School of Engineering


ISISE,
Departament

of

Civil
Engineering

Uma Escola a Reinventar o Futuro


Semana da Escola de Engenharia


24 a 27 de Outubro de 2011

GLÁUCIA

DALFRÉ

*


Supervisors:
Joaquim

Barros

*
gmdalfre@civil.uminho.ptt

EMBEDMENT OF STEEL BARS FOR THE SHEAR STRENGTHENING OF CONCRETE ELEMENTS

Introduction

An

ongoing

experimental

program

formed

by

continuous

slab

strips

strengthened

in

flexure

with

NSM

CFRP

laminates

is

being

carried

out,

and

the

obtained

results

show

the

possibility

of

increasing

significantly

the

load

carrying

capacity

of

these

elements,

maintaining

high

levels

of

ductility
.


However
,

the

occurrence

of

shear

failure

in

the

continuous

slab

strips

limits

the

efficacy

of

the

NSM

technique
.

In

general,

the

shear

failure

is

followed

by

the

detachment

of

the

strengthened

concrete

cover

layer

(Figure

1
)
.








In

the

case

of

beams,

NSM

CFRP

laminates

can

be

applied

into

slits

opened

on

the

concrete

cover

of

the

lateral

faces

of

the

element
.

However
,

in

case

of

slabs,

the

NSM

shear

strengthening

has

no

applicability,

and

a

strengthening

strategy

that

avoids

the

occurrence

of

shear

failure

and

provides

extra

resistance

to

the

detachment

of

the

NSM

laminates

is

proposed

in

this

work
.


According

to

the

proposed

strengthening

strategy

(Figure

2
),

holes

are

opened

across

the

slab/beam

thickness,

with

the

desired

inclinations,

and

bars

are

introduced

into

these

holes

and

bonded

to

the

concrete

substrate

with

adhesive

materials
.

To

assess

the

effectiveness

of

this

technique,

a

comprehensive

experimental

program

was

carried

and

the

obtained

results

confirm

the

feasibility

of

the

strengthening

system
.










Existing steel bars
Existing steel bars
Potencial shear
crack
CFRP bars bonded with an adhesive
CFRP bar
Adhesive
S-S
S
S
Experimental

Program

The

experimental

program

is

formed

by

two

series,

A

and

B,

composed

of

beams

with

a

cross

section

of

150
x
300

mm
2

and

300
x
300
mm
2
,

respectively,

with

a

total

length

of

2450

mm

and

the

shear

strengthening/reinforcement

configurations

represented

in

Figure

3
.





Results

of

the

experimental

program

The

applied

loads

versus

deflection

curves

of

the

tested

RC

beams

are

presented

in

Figure

4
.

It

can

be

noted

that

the

use

of

embedded

steel

bars

allowed

significant

increment

of

the

shear

resistance

of

reinforced

concrete

beams,

regardless

of

the

orientation

of

the

bar
.

The

effectiveness

is

not

only

in

terms

of

the

beam

load

carrying

capacity,

but

also

in

terms

of

the

ductility

of

the

beam’s
.

Beam
´
s

designation

Shear
strengthening

arrangements

Shear span

strengthening/
reinforcement

Reference





S
-
300
-
90º





S
-
225
-
90º





ETS
-
300
-
90º





ETS
-
300
-
45º





S
-
300
-
90º/

ETS
-
300
-
90º





S
-
300
-
90º/

ETS
-
300
-
45º





S
-
225
-
90º/

ETS
-
225
-
90º





Figure
3:
Shear
strengthening configurations


Figure 1:
Slab strip failure mode


Figure 2: Shear Strengthening concept


Institu
t
e
f
or Sustainability and
Inn
o
v
ation in Structural Engineering
F
F
300
300
300
F
225
225
225
225
F
150
300
150
300
F
300
300
300
F
150
300
150
300
F
300
300
300
F
225
225
225
112,5
300
300
300
150
300
300
300
150
300
300
300
150
300
300
300
150
300
300
300
150
300
300
300
150
300
300
300
150
300
300
300
150
A Series

B
Series