U.S. patent application number 10/833029 was filed with the patent office on 2004-11-04 for corrosion-free bridge system.
Invention is credited to El-Badry, Mamdouh M..
Application Number | 20040216249 10/833029 |
Document ID | / |
Family ID | 33304413 |
Filed Date | 2004-11-04 |
United States Patent
Application |
20040216249 |
Kind Code |
A1 |
El-Badry, Mamdouh M. |
November 4, 2004 |
Corrosion-free bridge system
Abstract
The present invention relates to a system of short- and
medium-spans for bridges and other structures. The bridge
superstructure is built mainly from components that are not
vulnerable to corrosion. It consists of precast prestressed
concrete truss girders and a concrete deck. The girders have top
and bottom concrete bulbs (i.e. flanges) connected by precast
vertical and diagonal truss members made of corrosion-resistant
metallic or non-metallic tubes filled with concrete. The deck can
be a cast-in-situ reinforced concrete slab or an assembly of
precast concrete panels tied together by longitudinal with or
without transverse prestressing tendons. The reinforcement in the
slab can be fibre reinforced polymer (FRP) bars and/or
corrosion-resistant steel bars. The term corrosion-resistant metal
or steel means a product that has delayed corrosion properties.
Inventors: |
El-Badry, Mamdouh M.;
(Calgary, CA) |
Correspondence
Address: |
THOMAS E. MALYSZKO
SUITE 1500
250 - 6 AVENUE, S.W.
CALGARY
T2P 3H7
CA
|
Family ID: |
33304413 |
Appl. No.: |
10/833029 |
Filed: |
April 28, 2004 |
Current U.S.
Class: |
14/13 |
Current CPC
Class: |
E01D 2101/264 20130101;
E01D 2101/266 20130101; E01D 2/02 20130101; E01D 2101/40 20130101;
E01D 2101/285 20130101; E01D 6/00 20130101; E01D 19/125
20130101 |
Class at
Publication: |
014/013 |
International
Class: |
E01D 021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 29, 2003 |
CA |
2,427,152 |
Claims
I claim:
1. A corrosion-free bridge system comprising precast prestressed
concrete truss girders and a concrete deck, the girders having top
and bottom concrete flanges connected by precast vertical and
diagonal truss members made of corrosion-resistant metallic or
non-metallic tubes filled with concrete.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a structural system in
general, and in particular to bridge systems which are resistant
to, or are not suseptible to, corrosion.
BACKGROUND OF THE INVENTION
[0002] Corrosion is of concern for any structure made of mettalic
components. Bridge superstructures are of special concern as they
are entirely exposed to the corrosive elements of the ambient,
particularly those near or passing over bodies of salt water. Many
current designs continue to employ materials and arrangements which
are prone to corrosion. What is therefore desired is a novel system
which overcomes the limitations and problems of corrosion in prior
art structural designs. It should also provide for a lighter weight
superstructure, thus allowing for longer spans, and for increased
durability to reduce maintenance costs and extend the useful life
of the structure.
DESCRIPTION OF THE DRAWINGS
[0003] Embodiments of the invention will now be described, by way
of example only, with reference to the accompanying drawings,
wherein:
[0004] FIG. 1 is an elevational view of a system of truss girders
and concrete deck according to a preferred embodiment of the
present invention;
[0005] FIG. 2 is a cross-sectional view along line A-A of FIG. 1
showing a cast-in-situ deck slab atop a truss girder according to
one version of the present invention; and,
[0006] FIG. 3 is a cross-sectional view along line A-A of FIG. 1
showing precast deck panels atop truss girders according to another
version of the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0007] This invention is an innovative system of short- and
medium-spans for bridges and other structures. The new system can
apply to hundreds of bridges constructed every year. In this
system, the superstructure is built mainly from materials that are
not vulnerable to corrosion. Additional advantages are reduced
self-weight of the structure and enhanced durability. The light
weight should reduce load on the supports and allow for longer
spans, resulting in reduction in the size of substructure and in
the number of supporting piers in multi-span bridges and, hence,
reduction in the initial cost. The improved durability should
reduce the maintenance cost and extend the life span of the
structure.
[0008] FIGS. 1, 2 and 3 show two versions of a corrosion-free
bridge system according to a preferred embodiment of the present
invention. The invention consists of precast prestressed concrete
truss girders (generally indicated by the reference numeral 10) and
a concrete deck slab 30. Each girder 10 has top and bottom concrete
bulbs (i.e. flanges) 12, 14 connected by precast vertical and
diagonal truss members 16, 18. In addition to concrete, the
materials used are fibre-reinforced polymers (FRP) and
corrosion-resistant steel. The term corrosion-resistant steel or
metal means a product that has delayed corrosion properties.
[0009] The materials used in the present invention will now be
descibed in some greater detail. Referring first to the bridge deck
30, particular attention is given to the bridge deck as it
represents an important component that considerably affects the
overall cost and quality of the structure.
[0010] The bridge deck can be made of a cast-in-situ reinforced
concrete slab 30a (as illustrated in FIG. 2) or of an assembly of
precast concrete panels 30b tied together by longitudinal with or
without transverse prestressing tendons 32, 33 (FIG. 3).
[0011] Reinforcement of a cast-in-situ deck slab 30a (FIG. 2) can
be glass, carbon or other FRP bars 34. Alternatively, the FRP bars
can be used in both the transverse and longitudinal directions for
the top reinforcement, whereas the bottom reinforcement can be
composed of corrosion-resistant steel bars 36 in the transverse
direction and FRP bars in the longitudinal direction.
[0012] Post-tensioning of precast deck slab panels 30b (FIG. 3) can
be done by FRP or corrosion-resistant steel tendons 32, 33.
[0013] Corrosion-resistant steel double-head studs 38 (i.e. steel
bars with heads for anchorage) will be used to connect the deck
slab to the girders. When precast deck panels 30b are used, pockets
are left in the panels at the location of the studs to be filled
with grout subsequent to post-tensioning.
[0014] Specific attention will now be given to the various features
of the bridge girders 10.
[0015] The concrete bulbs 12, 14 are pretensioned with FRP or
corrosion-resistant steel tendons 16. The bulbs are provided with
corrosion-resistant steel stirrups 18 and with longitudinal
non-prestressed FRP or corrosion-resistant steel bars 20 at the
corners of the stirrup.
[0016] The vertical and diagonal truss members 16, 18, for
resisting shear forces are made of FRP or corrosion-resistant steel
tubes filled with high-strength concrete. The truss members can
alternatively be made of precast concrete elements, thus
eliminating the need for hollow tubes. In this case,
corrosion-resistant steel stirrups or spirals may be provided. A
preferred outer diameter of the verticals 16, which are mainly in
compression, is approximately 150 mm, although other sizes may be
suitable as well. The diagonals 18, which are mainly in tension,
have an outer diameter of approximately 90 mm, although other sizes
may also be suitable depending on the application. Both the
verticals and the diagonals are produced prior to the bulbs 12, 14.
FRP or corrosion-resistant steel dowels 22 protrude from the ends
of the verticals to connect them to the bulbs. Double-head studs 24
connect the diagonals to the bulbs. Alternatively, the diagonals
can be pretensioned with FRP flexible tendons or
corrosion-resistant steel tendons. The pretensioning should provide
the diagonals with a reserve tensile capacity in case the FRP tubes
are damaged by fire. The tendons protrude from the ends of the
diagonals and are bent to serve as dowels connecting the diagonals
to the bulbs. For ease in production, it is preferable that the
bulbs be cast in a rotated position, while the verticals and
diagonals lie on a horizontal surface. In case of damage by fire,
the FRP tubes can be easily replaced by wrapping the concrete
diagonals and verticals by FRP sheets or jackets.
[0017] After casting the concrete slab 30a or placing the deck
panels 30b, the precast truss girders 10 are post-tensioned by
external FRP or corrosion-resistant steel tendons to balance the
slab weight, to provide continuity between the different spans, and
to resist subsequent loads on the bridge. The external tendons are
harped (i.e. held down) to the bottom bulb 14 at two points within
the span and held up to the top bulb 12 at one or two points near
the intermediate supports in continuous bridges. No deviators will
be required at the harping points. The horizontal parts of the
tendons between the harping points pass through ducts placed inside
the bottom bulb, for a single-span bridge, or inside both the top
and bottom bulbs in a continuous bridge. The ducts may be left
ungrouted for easy replacement of the tendons, or may be grouted to
achieve bond between the horizontal parts of the tendons and the
concrete bulb(s).
[0018] The above description is intended in an illustrative rather
than a restrictive sense and variations to the specific
configurations described may be apparent to skilled persons in
adapting the present invention to specific applications. Such
variations are intended to form part of the present invention
insofar as they are within the spirit and scope of the claims
below. For instance, the system of the present invention may be
applied to curved bridges and may be easily adapted to space
trusses and segmental construction for use in bridges and other
structures.
* * * * *