U.S. patent application number 11/665018 was filed with the patent office on 2009-01-15 for method of reinforcing a bridge.
This patent application is currently assigned to Intelligent Engineering (Bahamas) Limited. Invention is credited to Stephen John Kennedy.
Application Number | 20090013482 11/665018 |
Document ID | / |
Family ID | 33548513 |
Filed Date | 2009-01-15 |
United States Patent
Application |
20090013482 |
Kind Code |
A1 |
Kennedy; Stephen John |
January 15, 2009 |
Method of reinforcing a bridge
Abstract
A method of repairing, reinforcing or reinstating a bridge,
comprising fixing a reinforcing plate in a spaced relationship with
an existing plate or girder, especially on the underside of the
bridge structure, to form a closed cavity, and injecting plastics
or polymer material into said cavity in liquid form, whereby said
plastics or polymer material sets or cures so as to bond to said
reinforcing and existing plates with sufficient strength to
transfer shear forces therebetween.
Inventors: |
Kennedy; Stephen John;
(Ontario, CA) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
Intelligent Engineering (Bahamas)
Limited
|
Family ID: |
33548513 |
Appl. No.: |
11/665018 |
Filed: |
October 25, 2005 |
PCT Filed: |
October 25, 2005 |
PCT NO: |
PCT/GB05/04116 |
371 Date: |
March 18, 2008 |
Current U.S.
Class: |
14/77.1 ;
14/78 |
Current CPC
Class: |
E01D 22/00 20130101 |
Class at
Publication: |
14/77.1 ;
14/78 |
International
Class: |
E01D 22/00 20060101
E01D022/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 18, 2004 |
GB |
0425454.6 |
Claims
1. A method of repairing, reinforcing or reinstating a bridge,
comprising fixing a reinforcement plate in a spaced relationship
with an existing plate or girder of the bridge structure to form a
closed cavity, and injecting plastics or polymer material into said
cavity in liquid form, whereby said plastics or polymer material
sets or cures so as to bond to said reinforcing and existing plates
with sufficient strength to transfer shear forces therebetween.
2. A method according to claim 1 wherein the existing plate or
girder is on the underside of the bridge.
3. A method according to claim 2 wherein the bridge has a plurality
of trough-shaped stiffeners, the reinforcing plate spans between
the bottoms of the trough-shaped stiffeners and a lightweight form
is provided in the space between the troughs prior to injection of
the core material.
4. A method according to claim 3 wherein the lightweight form has a
lower density than the core material.
5. A method according to claim 3 wherein the lightweight forms are
hollow elongate bodies.
6. A method according to claim 5 wherein the lightweight forms are
made of telescoping hollow prisms closed by end caps.
7. A method according to claim 6 wherein the prisms have
trapezoidal cross-sections arranged to fit the space between the
stiffening troughs.
8. A method according to claim 2 wherein the bridge has a plurality
of plates spanning between girders and said step of fixing a
reinforcing plate comprises fixing a first reinforcing plate to a
first girder and a second reinforcing plate to a second girder
adjacent the first girder, the first and second reinforcing plates
cooperating to span the distance between said girders.
9. A method according to claim 8 wherein said first and second
reinforcing plates overlap in a lap joint.
10. A method according to claim 8 wherein the first and second
reinforcing plates are curved to match the curvature of the
existing plates.
11. A method according to claim 1 wherein the existing plate is a
web of a box or plate girder.
12. A method according to claim 1 wherein the reinforcing plate is
metal, e.g. steel, stainless steel or aluminium.
13. A method according to claim 1 wherein the reinforcing plate has
a thicknesses in the range of from 0.5 to 20 mm.
14. A method according to claim 1 wherein the plastics or polymer
core is an elastomer such as polyurethane.
15. A method according to claim 14 wherein the elastomer is
compact.
16. A bridge comprising an existing structure adjacent which is
provided a reinforcing plate, the reinforcing plate being bonded to
the existing structure by an intermediate layer of plastics or
polymer material that is bonded to the reinforcing plate and the
existing structure with sufficient strength to transfer shear
forces therebetween.
Description
[0001] The present invention relates to the repair or reinforcement
of bridges, in particular, all-steel orthotropic bridges, all-steel
railroad bridges and composite concrete-deck, steel-girder
bridges.
[0002] Structural sandwich plate members which comprise two outer
metal plates and a core of plastics or polymer material, e.g.
unfoamed polyurethane, bonded to the outer plates with sufficient
strength to substantially contribute to the structural strength of
the member are described in U.S. Pat. No. 5,778,813 and U.S. Pat.
No. 6,050,208, which documents are hereby incorporated by
reference. These sandwich plate systems (SPS) may be used in many
forms of construction to replace stiffened steel plates, formed
steel plates, reinforced concrete or composite steel-concrete
structures and greatly simplify the resultant structures, improving
strength and structural performance (e.g. stiffness, damping
characteristics) while saving weight. Further developments of these
structural sandwich plate members are described in WO 01/32414,
also incorporated hereby by reference. As described therein, foam
forms or inserts may be incorporated in the core layer to reduce
weight and transverse metal shear plates may be added to improve
stiffness.
[0003] According to the teachings of WO 01/32414 the foam forms can
be either hollow or solid. Hollow forms generate a greater weight
reduction and are therefore advantageous. The forms described in
that document are not confined to being made of light weight foam
material and can also be make of other materials such as wood or
steel boxes, plastic extruded shapes and hollow plastic
spheres.
[0004] As well as new build applications, the principles of SPS
construction have been applied to the repair of maritime
structures, in particular vehicle decks of RoRo ferries. This
procedure, known as overlay, is described in WO 02/20341, which
document is hereby incorporated in its entirety by reference.
Briefly, the existing metal panel is cleaned and prepared, e.g. by
grit blasting, then a reinforcement plate is welded above the
existing metal panel so that a cavity is formed. The cavity is then
filled with a liquid thermoset polymer, such as polyurethane, which
sets and bonds the reinforcement plate to the existing panel with
sufficient strength to transfer shear forces between the existing
panel and reinforcement plate. This repair method can be performed
in much less time than a traditional cut-and-replace repair,
reducing the period for which the vessel is out of action, and can
provide a deck with improved structural and wear
characteristics.
[0005] It has also been proposed to use SPS panels to form the deck
of D-bridges, Bailey bridges and girder bridges, as described in WO
02/29160.
[0006] Many road and rail bridges are made of steel or composite
(steel & concrete) construction. A transverse cross-section
through a typical composite road bridge is shown in FIG. 1 of the
accompanying drawings. As can be seen, a concrete deck 10 is
supported by longitudinal steel girders 11. The size, spacing and
number of girders depend on the size of the bridge, loads to be
carried and the designer's choices. Traditional repair methods
associated with concrete deck deterioration vary from resurfacing
to complete deck replacement Deck replacement requires the old
concrete deck to be removed and is generally replaced with precast
prestressed concrete planks that span across several girders. The
planks contain block outs for continuity reinforcing steel, shear
connectors, guard rails, traffic barriers and abutting joints.
Subsequently to being placed these planks are post-tensioned and
grouted to make them continuous and composite with the existing
girders. The durability of the in-field grouted joints is
questionable.
[0007] An all-steel orthotropic bridge is shown in FIG. 2 of the
accompanying drawings. In this bridge, the steel deck 20, which may
for example carry an asphalt road, is stiffened by a number of
longitudinal troughs, also of steel. A steel box girder 22 spans
between piers to support transverse beams and the orthotropic deck.
Bridges of this type are susceptible to fatigue, with cracks
forming in the deck plate at or near welds joining the trough
stiffeners to the deck plate or in the webs or transverse
beams/diaphragms where the trough stiffeners pass through the web.
Traditional repair methods requires identification of the fatigue
cracks, back gouging and (re)welding of the cracks. Additional
local reinforcement may be applied, or modifications to the
geometry or weld groups made, to lessen the stress range locally
and the probability of the reformation of these cracks.
[0008] In the elevated steel railway bridge shown in FIG. 3 of the
accompanying drawings, the steel panels 30 are used to hold ballast
31 which in turn supports sleepers (railway ties) and rails 32. The
steel deck plate is pre-formed in double curvature and riveted to
transverse beams 33. Repeated dynamic loads cause fatigue cracks to
form through the plate within the cantilever section that protrudes
beyond the flange tip of the transverse beams. With old structures,
the steel grade may not be weldable, in which case the only known
method of repair is to replace the pre-formed steel deck and
transverse beams with new steel construction.
[0009] The methods of repair to rehabilitate the bridge types
described disrupt traffic flow and adversely affect the local
economy. As a result repair times are minimised and are often
conducted with limited night-time or off-peak closures. However,
complete closures may be required in some cases. Re-routing traffic
also adds costs.
[0010] It is an aim of the present invention to provide a method by
which a bridge may be repaired, reinstated or improved, e.g to
increase load carrying capacity or to enhance structural
performance, in particular shear resistance and reduce structural
borne noise.
[0011] According to a first aspect of the present invention
existing concrete deck composite steel girder bridges can be
rehabilitated by either replacing the existing concrete deck with
prefabricated SPS deck panels, which are subsequently made
composite with the steel girders by bolting and welding between
panels, or by completely replacing the superstructure with SPS
panels with integrated girders. In either case the use of
prefabricated SPS deck panels offers simplicity in deck replacement
which translates into shorter construction schedules that can be
accommodated by limited closures. Prefabricated SPS deck panels
offer further advantages of factory quality control and a limited
amount of field fabrication which is well understood and widely
used, thus providing a deck structure with a service life similar
to the steel superstructure.
[0012] In additional the first aspect of the present invention can
provide a deck of equivalent or greater strength and stiffness
whilst weighing up to 75% less than the original corresponding
reinforced concrete deck. Deck weight savings of this order of
magnitude allow for either increase load carrying capacity or an
increased number of traffic lanes without need to reinforce the
substructure or to add additional girders.
[0013] According to a second aspect of the present invention there
is provided a method of repairing, reinforcing, or enhancing the
structural performance of an existing bridge comprising fixing a
reinforcing plate in a spaced relationship with an existing plate
or girder of the bridge structure to form a closed cavity, and
injecting plastics or polymer material into said cavity in liquid
form, whereby said plastics or polymer material sets or cures so as
to bond to said reinforcing and existing plates with sufficient
strength to transfer shear forces therebetween.
[0014] By fixing the reinforcing plate to the underside of the
bridge structure, minimum disruption to the load-carrying deck is
caused and in many cases traffic may continue to flow throughout
the repair process. The completed repair provides structural
sandwich plates which have increased stiffness and provided better
vibration damping characteristics. Increased transverse stiffness
aids in lateral load sharing of concentrated wheel loads between
adjacent trough stiffeners, and advantageously lessons the stress
ranges at critical weld groups joining the trough stiffeners to the
deck plate and where the troughs pass through either diaphragms or
transverse beams, resulting in substantially increased fatigue
resistance and service life.
[0015] The materials, dimensions and general properties of the
reinforcing plates or the invention may be chosen as desired for
the particular bridge to which the invention is to be applied and
in general may be as described in U.S. Pat. No. 5,778,813 and U.S.
Pat. No. 6,050,208. Steel or stainless steel is commonly used in
thicknesses of 0.5 to 20 nm and aluminium may be used where light
weight is desirable. Similarly, the plastics or polymer core may be
any suitable material, for example a compact elastomer such as
polyurethane, as described in U.S. Pat. No. 5,778,813 and U.S. Pat.
No. 6,050,208.
[0016] In the second aspect of the invention where the repair is
applied to the underside of a bridge having a plurality of
trough-shaped stiffeners, the reinforcing plate spans between the
bottoms of the trough-shaped stiffeners and a lightweight form is
provided in the space between the troughs, prior to injection of
the core material. The lightweight forms or inserts should have a
lower density than the core material and should resist sufficiently
temperatures and pressures experienced in the injection and setting
of the core material but otherwise their mechanical properties are
not particularly important as they do not significantly contribute
to the strength of the repaired structure. The lightweight forms
should not completely fill the space between the troughs but should
allow a layer of the core material all around them.
[0017] Conveniently, the lightweight forms may be hollow elongate
bodies. In one particular embodiment, the lightweight forms are
made of telescoping hollow prisms closed by end caps. The prisms
may have trapezoidal cross-sections arranged to fit the space
between the stiffening troughs.
[0018] In the second aspect of the present invention, the repair
may instead be applied to the deck surface. In this case it may be
advantageous to use heat resistant adhesives to fix the perimeter
bars of an SPS overlay cavity to the existing structure. Subsequent
welding of the new deck faceplates to the perimeter bars and to
each other will not damage the paint or corrosion protective
coatings on the underside surface.
[0019] The present invention will be described below with reference
to exemplary embodiments and the accompanying schematic drawings,
in which:
[0020] FIG. 1 is a cross-sectional view of a typical concrete deck
composite steel girder bridge;
[0021] FIG. 2 is an isotropic view of a typical steel orthotropic
bridge with box girders;
[0022] FIG. 3 is an isotropic view of a railway bridge with
preformed steel panels;
[0023] FIG. 4 is a cross-sectional view of the deck of a composite
steel girder bridge according to a first embodiment of the
invention;
[0024] FIG. 5 is an isotropic view of the deck of a composite steel
girder bridge according to a second embodiment of the
invention;
[0025] FIG. 6 is an isotropic view of the bridge depicted in FIG. 2
to which a method according to a third embodiment of the present
invention has been applied to rehabilitate and reinforce the deck
structure from the underside;
[0026] FIG. 7 is an expanded view of the repaired bridge of FIG.
6;
[0027] FIG. 8 is an isotropic view of the bridge depicted in FIG. 2
to which a method according to a fourth embodiment of the present
invention has been applied, from above;
[0028] FIG. 9 is an isotropic view of the railway bridge depicted
in FIG. 3 to which a method according to a fifth embodiment of the
present invention has been applied;
[0029] FIG. 10 is a longitudinal section of the repaired bridge of
FIG. 9;
[0030] FIG. 11 is a cross-section view illustrating a-drain detail
of the repaired-bridge of FIG. 9;
[0031] FIG. 12 is an expanded view of the panel of the repaired
bridge of FIG. 9;
[0032] FIG. 13 is an isotropic view of a typical box girder bridge
(without deck for clarity) with structurally enhanced webs
according to a sixth embodiment of the present invention; and
[0033] FIG. 14 is an isotropic view of stiffened plate girder with
structurally enhanced webs according to a sixth embodiment of the
present invention.
[0034] In the various drawings, like parts are indicated by like
reference numerals.
[0035] According to a first embodiment of the present invention
existing concrete deck composite steel girder bridges is
rehabilitated by replacing the existing concrete deck with
prefabricated SPS deck panels 101, as illustrated in FIG. 4. The
SPS deck panels are subsequently made composite with the existing
steel girders 102 by bolting and welding between panels 101. The
replacement SPS panels 101 are made continuous by welding them
together at abutting edges. The existing, or a new, steel guard
rail 103 may be bolted to the SPS deck panels.
[0036] The SPS panels 101 each comprise outer metal faceplates 104,
106 bonded together by an intermediate, or core, layer 105 of
plastics or polymer material. The faceplates may be steel plates
with a thickness in the range of from 2 to 20 mm, as required for
the particular application. For the plastics or polymer material,
preferably a compact (i.e. not a foam) thermosetting material such
as polyurethane elastomer, is used. Core layer 105 may have a
thickness in the range of from 15 to 200 mm and is bonded to the
faceplates 104, 106 with sufficient strength and has sufficient
mechanical properties to transfer shear forces expected in use
between the reinforcement and existing structure. The bond strength
should be greater than 3 MPa, preferably 6 MPa, and the modulus of
elasticity of the core material should be greater than 200 MPa,
preferably greater than 250 MPa, especially if expected to be
exposed to high temperatures in use. By virtue of the core layer,
the reinforced structure has a strength and load bearing capacity
of a stiffened steel plate having a substantially greater plate
thickness and significant additional stiffening. The replacement
panels 101, of course, need not be flat but may take whatever form
is required to fit to the existing structure.
[0037] The use of prefabricated SPS deck panels offers simplicity
in deck replacement which translates into shorter construction
schedules that can be accommodated by limited closures.
Prefabricated SPS deck panels offer further advantage of factory
quality control and a limited amount of field fabrication which is
well understood and widely used, thus providing a deck structure
with a service life similar to the steel superstructure.
[0038] In a second embodiment of the invention the superstructure
is completely replaced with SPS panels 201 with integrated girders
202, as illustrated in FIG. 5. The SPS panels 201 are essentially
the same as the panels 101 of the first embodiment but the
longitudinal and/or transverse girders 202 are integrated into the
panels during off-site fabrication. The webs of the girders may
form parts of the side walls to the cavities into which the core
material is injected whilst one or both faceplates may act as the
flanges of the beams. As in the first embodiment, the use of
prefabricated SPS deck panels offers simplicity in deck
replacement, factory quality control and a limited amount field
fabrication with attendant advantages.
[0039] In addition, the first and second embodiments of the present
invention provide a deck of equivalent or greater strength and
stiffness than the original corresponding reinforced concrete deck
whilst weighing up to 75% less. Deck weight savings of this order
of magnitude allow for either increase load carrying capacity or an
increase number of traffic lanes without need to reinforce the
substructure or to add additional girders.
[0040] In a third embodiment of the invention, shown in FIG. 6, the
existing structure of a bridge comprising load carrying deck 20 and
stiffening troughs 21 has been repaired or reinforced by the
addition of a reinforcing plate 331 which spans between the bottoms
of stiffening troughs 21. The reinforcing plate 331 may be a steel
plate with a thickness in the range of from 2 to 20 mm, as required
for the particular application. To bond the reinforcing plate 331
to the existing structure, a core layer 332 of plastics or polymer
material, preferably a compact thermosetting material such as
polyurethane elastomer, is used. This core may have a thickness in
the range of from 15 to 200 mm. The core 332 is bonded to the
reinforcing plates 331 and the existing structure 20, 21 with
sufficient strength and has sufficient mechanical properties to
transfer shear forces expected in use between the reinforcement and
existing structure. The bond strength should be greater than 3 MPa,
preferably 6 MPa, and the modulus of elasticity of the core
material should be greater than 200 MPa, preferably greater than
250 MPa, especially if expected to be exposed to high temperatures
in use. By virtue of the core layer, the reinforced structure has a
strength and load bearing capacity of a stiffened steel plate
having a substantially greater plate thickness and significant
additional stiffening. The reinforcing plate, of course, need not
be flat but may take whatever form is required to fit to the
existing structure.
[0041] To reduce the volume of core material required to bond the
reinforcement to the existing structure, lightweight forms or
inserts 333 are provided in the space between stiffening troughs
21. The forms 333 preferably have a cross-sectional shape matching
that of the space between troughs but sized so as to leave a layer
of core material of thickness in the range of from 15 to 200 mm all
around. The forms are preferably elongate hollow bodies of the
appropriate cross-section but may also be made of lightweight
materials such as foam. Each insert may also be made up from a
plurality of elongate parts of standard cross-section, to avoid the
need to manufacture special forms for each bridge.
[0042] As more clearly shown in FIG. 7, which is an expanded view
of the repaired bridge, each form 333 is preferably made of two
parts 334 which fit into a sleeve 335 so that the length of the
form may be adjusted by sliding the parts 334 into or out of the
sleeve 335. End caps 336 close the two ends of the form. This
arrangement suits bridges where the profile and spacing of the
stiffening troughs is constant but the spacing between transverse
girders may vary.
[0043] Especially when hollow, the forms may be fitted around any
utilities, e.g. water or gas pipes, power or communications cables,
that may be attached to the underside of the bridge. Hollow forms
can also serve as trunking for the later addition of utilities if
suitable access points and through-holes in transverse girders are
provided.
[0044] To effect the repair, firstly the undersurfaces of all
troughs 21 and exposed plates of the deck 20 are grit blasted to
provide a clean surface to which the core material can adhere. Then
the forms 333 are fixed in place, e.g. by tack welding, and the use
of suitable spacers as required. Once this has been completed,
landing bars are welded in place at the positions of the edges of
the reinforcing plates so that the reinforcing plates can be welded
in place. The cavities defined by the reinforcing plates and
existing structure are sealed, leaving injection ports and vent
holes as required. Core material is then injected and allowed to
cure to form a strong bond between the reinforcing plates and
existing structure. To finish off, the injection ports and vent
holes can be sealed and ground flush before any desired surface
treatment, e.g. paint, is applied to prevent corrosion or for
aesthetic reasons.
[0045] The same bridge may be repaired by the addition of an
overlay to the top surface, as shown in FIG. 8, which illustrates a
fourth embodiment of the invention. In this embodiment, a
reinforcing plate 401 is fixed above the existing plate 20 so as to
form a cavity. The cavity is then filled by injection of plastic or
polymer material 402 which, when set, bonds the reinforcing plate
401 to the existing plate 20 with sufficient strength to transfer
shear forces expected in use. In this respect, the fourth
embodiment is the same as the other embodiments of the invention
and the reinforcing plate and core material may be as described
above. An asphalt road surface 403 is laid on top of the
reinforcing plate once the core layer is fully cured.
[0046] To fix the reinforcing plate 401 in place prior to the
injection of the core, welded or adhered perimeter bars may be used
to define the cavity to be filled. Spacers and lightweight forms or
inserts may also be employed, as in the other embodiments of the
invention.
[0047] In a fifth embodiment of the present invention a repair is
applied to the underside of pre-formed steel plate of an elevated
railway bridge to enhance the fatigue resistance and to extend the
service life of the structure. The repair, illustrated in FIG. 9,
is consistent in shape and construction with the existing structure
and does not detract from its historic nature.
[0048] Applied from below without disrupting rail services, two
preformed plates 501, 502 of matching shapes to the existing
structure are bolted to the webs of transverse beams of the
existing structure and riveted with one-sided rivets to each other,
forming a lap joint 503 at mid panel length that extends across the
bridge as shown in FIG. 10. The lap joint provides a simple
connection detail that will allow for dimensional variations that
will occur in each panel along the length of the bridge.
Subsequently drains 504 are re-established as shown in FIG. 11.
[0049] A combination of flexible, closed-cell foam-like material
and caulking is used to seal the ends of the cavity. The cavity is
subsequently injected from below, first through the central region
and then at either end, to ensure complete filling with core
material 505. This method of repair not only lessens the stress
range in the existing pre-formed steel panel (at or near the
leading edge where the cantilever plate section passes over the
flange tip of the transverse beams) thereby increasing the fatigue
resistance, it also provides a visco-elastic layer to absorb
structural-borne noise, an added benefit for urban centres where
elevated railway systems like this exist.
[0050] A sixth embodiment of the present invention is a
modification to the existing structures by the application of SPS
overlay 601 to webs 602 of box and plate girders 603, 604, as shown
in FIGS. 13 and 14, with the prime objective to reduce
structural-borne noise associated with vibrations induced by the
traffic (road or rail) which the bridge carries. A by-product is a
structural enhancement, increased shear resistance and fatigue
resistance for weld groups joining the stiffeners to the web.
[0051] In the fifth and sixth embodiments the materials and
dimensions of the reinforcing plates and the core layer may be the
same as in the previously described embodiments.
[0052] It will be appreciated that the above description is not
intended to be limiting and that other modifications and variations
fall within the scope of the present invention, which is defined by
the appended claims.
* * * * *