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04 / 11
-
02 Weightman Bridge


Page
1

of
6

Press Release

Reprint free of charge. Copy requested.





Schöck Bauteile GmbH

Rosa Weimer

Vimbucher Straße 2

D
-
76534 Baden
-
Baden

Tel.: 07223 967
-
410

E
-
mail: presse@schoeck.de




Bridge rehabilitation with “Schöck ComBAR”


GFRP rebar in use at the Weightm
an Bridge in Niagara Falls, Ontario


In 2010 t
he City of Niagara Falls
rehabilitated

the Weightman
Bridge which crosses the Welland River along Portage Road. The
approximately
4 million dollar

project comprise
d

the replacement
of the complete bridge deck,
the side walks
as well as

the steel
railings. The bridge consists of two approach spans made of
concrete slabs on steel girders and a central pre
-
stressed
concrete girder navigational span. The deck

joints of the existing
bridge

we
re replaced
by

continuous
ly reinforced flexible links.
Several technical
innovations

regarding the use of
glass fibre
reinforced polymer

(
GFRP
)

we
re
involved in
the design, including
special rebar splices
.

Because of its excellent
material properties,
the newest generation GFRP re
bar “
Schö
ck ComBAR”
from

Schöck

Canada was
selected
for
the
reconstruction

of the bridge
deck

and
the
sidewalk slabs.


The four
-
lane

Weightman Bridge in Niagara Falls,
Ontario
,

was built in
1967. Heavy daily traffic crossing the bridge and the numerous fro
st
-
thaw cycles in the winters since the op
ening of the bridge ha
d

taken

their toll on the bridge deck and side walk slabs, which showed
extensive damage due to corrosion of the steel rebar.
After

a detailed




04 / 11
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02 Weightman Bridge


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analysis of the structure
,

the City of Niagara Fa
lls
decided

that it was
more economical to replace
the entire bridge deck
than to rehabilitate
it
.


A net value analysis
showed that

the installation of glass fibre
reinforced polymer (GFRP) rebar in the upper layers of the deck and
sidewalk slabs as well
as in the barrier walls
w
as

the most economic
al

renovation

concept. As a result, the city included this concept in the
o
riginal contract specifications.


Structural details


The three
-
span Weightman Bridge is located along Portage Road in
Niagara Falls, On
tario. It is 97.5 met
re
s long and 18.8
met
re
s

wide. The
bridge supers
tructure is a classical slab
-
on
-
girder system. The
substructure is formed by two outer spans



each
consisting of six large
steel girders



which cantilever beyond the two piers
in order
to support
a central pre
-
cast concrete segment. The steel girders are nearly 43
met
re
s long, extending about 9 metr
e
s beyond the piers. The shallow
central section is about 12.1 met
re
s long. It allows for limited navigation
underneath the bridge. Flexible
links at
each end

of the pre
-
cast section
allow
for
the transfer of vertical loads while rotation within the link is
still
possible.
In comparison to the old expansion joints, t
hese links are a
technically sounder solution
.


The original deck and sidewalk
slabs
of the bridge
had been heavily
damaged by rebar corrosion and needed to be replaced. While the steel
girders were deemed to be structurally sound
,

the central pre
-
cast
section was also removed in the course of the rehabilitation. It was
replaced by f
ourteen pre
-
cast
,
pre
-
stressed hollow core panels oriented
along the axis of the bridge. The panels are 1.2 metr
e
s wide and only
400
millimetres

high. Steel stirrups
we
re installed in the top of the
panels for connection of the cast
-
in
-
place deck slab.






04 / 11
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02 Weightman Bridge


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Th
e new deck
wa
s cast onto the hollow core planks in the central
section and
onto
the steel beams along the two outer spans. The
sidewalk slabs
we
re then cast directly onto the deck slab. Finally, the
new PL
-
2 concrete barrier walls a
re cast onto the sidewal
k slab
s
.


GFRP reinforcement


The original contract documents for the rehabilitation called for the
installation of either epoxy
-
coated o
r

GFRP rebar in the top layers of the
deck and sidewalk slabs. An analysis was
performed

after the tender
was
close
d

sh
owing that it was more economical to use the GFRP
reinforcement. The bottom layers were reinforced using carbon steel
rebar.


The contract for the bridge rehabilitation
contained the installation of
grade I (E ≥
6
0 GPa) GFRP rebar in the top layers of the bridge and
sidewalk slabs and grade II (E ≥
5
0 GPa) GFRP rebar in the PL
-
2 type
barrier walls. The final design of the bridge deck called for 16

millimetre

diameter grad
e I GFRP rebars at a spacing of 250mm in the
longitudinal direction and
16mm
bars
at 250mm

in the transverse
direction. Below the inner edge of the sidewalk slab
,

additional 25mm
bars were placed at 300mm to transfer the tensile forces in the top of
the ca
ntilevering deck slab. The sidewalk slabs were reinforced with
16
mm

bars at 200
mm

in the longitudinal direction and 16
mm

bars at
125
mm

in the transverse directions in the top layer. Carbon steel rebar
was placed in the bottom layer of the deck and the side
walk slabs. Bent
epoxy
-
coated steel bars were used in the bottom layer in select
ed

locations prone to rebar corrosion.


Due to its superior material properties
,

the
latest

generation GFRP
rebar Sch
ö
ck Com
BAR, distributed by Sch
ö
ck Canada, was chosen for
th
e upper layer of the bridge d
eck and the sidewalk slabs. Sch
ö
ck not
only supplied the material but also provided the installation, which was




04 / 11
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02 Weightman Bridge


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6

performed by To
tal Bridge Services Inc. (TBSI)


a long
-
term p
artner
company of Sch
ö
ck Can
a
da.

For economic reasons
,

the barrier walls
were reinforced using the grade II GFRP reinforcement V
-
Rod supplied
by Pultrall Inc.


Stages of the project


To minimis
e disruption of city traffic in Niagara Falls
,

the r
ehabilitation of
the Weightman B
ridge was executed in two stage
s. In stage
one,

the
right
, western

half of the bridge was closed. Both directions of traffic
were
then
redirected onto the left
-
hand

side of the bridge. In stage
two,

traffic
wa
s diverted onto the new deck
while
the east side of the bridge
wa
s rehabilitat
ed
.

This construction schedule required splicing the
transverse reinforcement in the deck along the
centre

line of the bridge.
In order to
do

this,

a new technology using GFRP bars glued into
corrugated polyester tube sleeves was
developed by Sch
ö
ck and TB
SI.
In stage
one,

pieces of 650
mm

long corrugated PE tube with an interior
diameter of 18
mm

were installed in the deck along the border between
the two phases. In stage
two,

ComBAR bars with a core diameter of
16
m
m

w
ere

inserted and glued into these tube
s
using an epoxy
-
based
adhesive.



Along the two abutments of the bridge
,

another special detail in the
rebar lay
-
out had to be developed on account of the unique material
properties of fibre reinforced polymer rebars

(FRPs). Unlike steel, FRPs
can
not be ben
t once they
have

hardened. Stirrups and bent bars have
to be prefabricated at the shop. More significantly, fibrous materials are
not isotropic. Their strength is substantially
higher

in the direction of the
fibres than it is perpendicular to them. As with

wood, for instance, any
redirection of the fibres in FRPs results in a substantial loss of strength
.

This can be compared
to a knothol
e in wood
. The problem arises when
a tensile load is applied on a bent portion of a FRP bar. As the fibres on
the outside

of the bend are extended much more than the fibres along




04 / 11
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02 Weightman Bridge


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the inner side, interlaminar shear stresses and transverse stresses are
induced in the bar. These result in premature failure of the bar along the
bent portion. To alleviate the resulting problems i
n the concrete
structure
,

straight ComBAR bars with end heads were used wherever
possible in the design of the Weightman Bridge when bent epoxy
-

coated bars were replaced.


At the abutments
,

the longitudinal bars at the top were thus provided
with end head
s, as were the vertical bars at the
centre

of the abutment
end beam. To provide closure in the system of load vectors
,

a short
section of bent bar was placed at each intersection of these headed
bars.

Structural design


The structural design of the new bri
dge deck and sidewalk slabs was
performed by ELLIS Engineering Inc. of St. Catharines,
Ontario


in
close cooperation with the
Sch
ö
ck
engineers. Ellis Engineering is a
well
-
k
nown consulting engineering firm specialis
ed

in the design and
rehabilitation of b
ridge structures. The design was performed according
to the Canadian Highway Bridge Design Code CAN/CSA
-
S6
-
06.
Reinforcement drawings were draw
n up by TBSI and checked by
Sch
ö
ck.


The Weightman Bridge is the first project
in which

the newest
generation gra
de
I

GFRP rebar
Schö
ck ComBAR is being installed in a
bridge deck in Canada. It is also the first project ever
in which

Sch
ö
ck
supplied the material and the placement of
the bars in a combined
package.


approx.
8
,
5
00 characters








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02 Weightman Bridge


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6

Project data

owner:



Cit
y of Niagara Falls, Ontario

contractor:


Rankin Construction Inc.

structural engineer:


ELLIS Engineering Inc.

installation:


May


December 2010


This text is available online at:

www.schoeck
-
canada.com

(“News & Media” section)

www.dako
-
pr.de

(“Servic
e” section).



Caption
s


[11
-
0
2

Onset
]

Weightman Bridge at onset of rehabilitation
.

Source
:
Sch
ö
ck Canada Inc.


[11
-
02 Detail]

Detail
of
flexible link joints with the
continuous reinforcement
.

Source: Sch
ö
ck Canada Inc.


[11
-
02 GFRP]

GFRP rebar grade I in
top layer of deck
.

Source
:
Schöck

Canada Inc.






Please address any queries to


Schöck Bauteile GmbH

dako pr corporate communications

Rosa Weimer

Johannes Eisenberg

Tel.: +49 (0)
7223 967
-
410

Tel.:
+49 (
0
)
214 20691
-
0

Fax:
+49 (
0
)
7223 9677
-
410

Fax:
+49 (
0
)
214 20691
-
50

E
-
mail: presse@schoeck.de

E
-
mail:
j.eisenberg
@dako
-
pr.de

www.schoeck.de

www.dako
-
pr.de