U.S. patent application number 13/411590 was filed with the patent office on 2012-09-06 for method to compress prefabricated deck units by tensioning elements at intermediate supports.
Invention is credited to Yidong He.
Application Number | 20120222375 13/411590 |
Document ID | / |
Family ID | 46752411 |
Filed Date | 2012-09-06 |
United States Patent
Application |
20120222375 |
Kind Code |
A1 |
He; Yidong |
September 6, 2012 |
Method to Compress Prefabricated Deck Units by Tensioning Elements
at Intermediate Supports
Abstract
A structural system comprised of prefabricated deck units spaced
along longitudinal load-carrying members which produces
longitudinal axial compression in deck units. During construction,
prefabricated deck units are erected on top of and supported by the
longitudinal load-carrying members via leveling devices, which also
permit relative motion between the longitudinal load-carrying
members and the prefabricated deck units. Anchor assemblies are
affixed to the longitudinal load-carrying members near intermediate
supports. Tensioned structural elements are installed in the anchor
assemblies between spans and stressed to induce tension in the
longitudinal load-carrying members and subsequently produce deck
compression.
Inventors: |
He; Yidong; (Naperville,
IL) |
Family ID: |
46752411 |
Appl. No.: |
13/411590 |
Filed: |
March 4, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61449713 |
Mar 6, 2011 |
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Current U.S.
Class: |
52/223.7 ;
52/745.13 |
Current CPC
Class: |
E04B 5/10 20130101; E04B
5/43 20130101; E01D 19/00 20130101; E01D 2101/285 20130101; E01D
19/12 20130101; E01D 21/00 20130101 |
Class at
Publication: |
52/223.7 ;
52/745.13 |
International
Class: |
E04B 1/02 20060101
E04B001/02; E04B 5/02 20060101 E04B005/02; E04B 7/00 20060101
E04B007/00; E01D 19/12 20060101 E01D019/12; E01D 21/00 20060101
E01D021/00 |
Claims
1. A structural system, comprising: a. a plurality of longitudinal
load-carrying members, b. a plurality of prefabricated deck units
spaced longitudinally along a structure, wherein said prefabricated
deck units are supported by said longitudinal load-carrying
members, c. one or more intermediate supports upon which said
longitudinal load-carrying members are partially supported, whereby
a plurality of longitudinal load carrying member spans are defined,
d. one or more anchor assemblies affixed to said longitudinal
load-carrying members in a region in proximity to said intermediate
supports, e. one or more tensioned structural elements installed
into said anchor assemblies to introduce longitudinal axial
compression to a plurality of said prefabricated deck units,
wherein said axial compression is a result of the application of
longitudinal axial tension to said longitudinal load-carrying
members, wherein no separate longitudinal post-tensioning elements
are required in the deck, and wherein no direct jacking of said
prefabricated deck units is required to introduce said longitudinal
axial compression, f. means to allow for relative movement between
a plurality of said longitudinal load-carrying members at a time at
which tensioning is applied to said tensioned structural element or
elements, g. means to transfer said longitudinal axial tension in
said longitudinal load-carrying members to axial compression to a
plurality of said prefabricated deck units.
2. The means to allow for relative movement of claim 1 (f) is
comprised of a physical gap of predetermined width between the
longitudinal load-carrying members of claim 1 that lie along the
same longitudinal line but in different spans, wherein said spans
are as defined in claim 1 (c).
3. The means to transfer axial tension of claim 1 (g) is comprised
of a plurality of mounted elements affixed to the longitudinal
load-carrying members of claim 1 in-between which are located a
plurality of prefabricated deck units of claim 1 that are
non-composite with the longitudinal bad-carrying members of claim 1
at the time of the tensioning of claim 1 (f).
4. The mounted elements of claim 3 are comprised of a plurality of
prefabricated deck units of claim 1 that are composite with the
longitudinal bad-carrying members of claim 1, whereby said
composite prefabricated deck units act as deck connection
units.
5. The structure of cairn 1 is comprised of one or more structural
units, wherein the longitudinal axial compression of claim 1 may be
introduced into the prefabricated deck units of claim 1 in any one
of said structural units independent of any other one or more of
said structural units.
6. The longitudinal load-carrying members of claim 1 are comprised
of any one member or any combination of members selected from the
group consisting of steel, concrete, wood, and composite
materials.
7. The longitudinal load-carrying members of claim 1 are comprised
of any one member or any combination of members selected from the
group consisting of I-girders, I-beams, box girders, and
trusses.
8. The tensioned structural element or elements of claim 1 are
comprised of any one member or any combination of members selected
from the group consisting of high strength bars, post-tensioning
rods, steel plates and post-tensioning tendons.
9. A method for constructing one or more structural units wherein
no separate longitudinal post-tensioning elements are required in
the deck, comprising the steps of: a. constructing a plurality of
prefabricated deck units, a plurality of supports for the
structure, a plurality of longitudinal bad-carrying members, a
plurality of anchor assemblies, wherein said assemblies are affixed
to said longitudinal bad-carrying members in regions to be in
proximity with intermediate instances of said supports, a plurality
of mounted elements, and a plurality of tensioned structural
elements, b. installing said longitudinal load-carrying member or
members, wherein said longitudinal load-carrying members are
supported by said supports, c. installing said tensioned structural
elements into said anchor assemblies d. installing a plurality of
said prefabricated deck units, wherein said prefabricated deck
units are supported by said longitudinal load-carrying members and
rest on devices that permit relative motion between said
prefabricated deck units and said longitudinal load-carrying
members, wherein said prefabricated deck units are non-composite
with said longitudinal load-carrying members, e. installing a
plurality of mounted elements, wherein a plurality of said
prefabricated units are located in-between said mounted elements,
f. stressing said tensioned structural elements to introduce axial
compression in said prefabricated deck units, wherein said axial
compression is a result of the application of longitudinal axial
tension to said longitudinal load-carrying member or members, g.
making said non-composite prefabricated deck units composite with
said longitudinal load-carrying members.
10. The longitudinal load-carrying members of claim 9 are comprised
of any one member or any combination of members selected from the
group consisting of steel, concrete, wood, and composite
materials.
11. The longitudinal load-carrying members of claim 9 are comprised
of any one member or any combination of members selected from the
group consisting of I-girders, I-beams, box girders, and trusses.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/449,713, filed Mar. 6, 2011 by the present
inventor.
FEDERALLY SPONSORED RESEARCH
[0002] Not Applicable
SEQUENCE LISTING OR PROGRAM
[0003] Not Applicable
BACKGROUND OF THE INVENTION
[0004] 1. Field of Invention
[0005] This invention relates to the design and construction of
structures, specifically to structures with prefabricated deck
units.
[0006] 2. Prior Art
[0007] Full-depth precast concrete deck has gained popularity as an
accelerated construction method. Use of full-depth precast concrete
deck allows for the deck concrete and reinforcement to be placed in
a controlled environment, improving the quality of the deck. Since
the units are prefabricated, they can be delivered to a site and
erected quickly.
[0008] Structures using full-depth precast concrete deck typically
consist of a plurality of longitudinally spaced concrete deck units
supported by longitudinal load-carrying members. This member or
members is usually a single girder or multiple girders.
[0009] This member or members can be comprised of various materials
including steel, concrete, wood or fiber-reinforced plastic.
[0010] To improve deck durability, it is important to have a
pre-compression force across deck joints to minimize the propensity
of the deck to crack under loading.
[0011] Currently, such pre-compression force is supplied via
standard post-tensioning systems, which utilize post-tensioning
tendons or bars within ducts. US Federal Highway Administration
technical report (#FHWA-IF-09-010) and Precast/Prestressed Concrete
institute State-of-the-Art Report on Full-Depth Precast Concrete
Bridge Deck Panels (SOA-01-1911) provide a comprehensive summary of
current engineering practice using precast deck units, showing that
all current precast deck systems with longitudinal compression
utilize post-tensioning systems in the deck. Other patent
references, such as U.S. Pat. No. 7,475,446, U.S. Pat. No.
7,461,427, and U.S. Pat. No. 5,457,839, teach various methods of
using post-tensioning systems to provide deck compression. However,
using standard post-tensioning details carries with it the
disadvantage of requiring additional cost and time to construct.
This invention provides a more economical solution.
[0012] U.S. Pat. No. 7,475,446 B1, by the present inventor, teaches
a solution to introduce pre-compression force across deck joints
via post-tensioning external to the deck, using a method to
transfer longitudinal compression to the deck units under the
following conditions: [0013] a. All deck units are non-composite
with the longitudinal load-carrying member when the longitudinal
compression transfer occurs. [0014] b. Longitudinal tensioning
elements are required to be anchored at one more specially designed
deck end units.
[0015] The proposed method discussed herein also provides a
solution to introduce pre-compression force across deck joints via
post-tensioning external to the deck, but 65 applies the following
differing conditions from those presented in U.S. Pat. No.
7,475,446: [0016] a. Composite deck connection units may be used in
the transfer of longitudinal compression to the deck units. [0017]
b. Anchorage of the tensioning elements directly into the deck
units is not required, as the tensioning elements are anchored to
attachments to the longitudinal load-carrying members
themselves.
[0018] Therefore, the method proposed herein eliminates the need
for special end deck units to be fabricated and allows for a
substantially reduced quantity of tensioned structural elements to
be employed versus that presented in U.S. Pat. No. 7,475,446.
[0019] U.S. application Ser. No. 12/857,713, by the present
inventor, teaches a solution to introduce pre-compression force
across deck joints via post-tensioning external to the deck, using
a method to transfer longitudinal compression to the deck units
under the following condition: [0020] a. The longitudinal axial
pre-compression of the deck is reacted by the longitudinal tensile
component of the post-tensioning, wherein the longitudinal axial
tensile component is not transferred via the supporting
girders.
[0021] The proposed method discussed herein also provides a
solution to introduce precompression force across deck joints via
post-tensioning external to the deck, but applies the following
differing condition from those presented in U.S. application Ser.
No. 12/857,713: [0022] a. The longitudinal axial pre-compression of
the deck is reacted by a longitudinal tension component in the
supporting girders, wherein this reaction is facilitated by anchor
assemblies at the supporting girder ends at intermediate supports
that allow for tension to be transferred between girders in the
same line but in different spans.
[0023] Therefore, the method proposed herein does not require
post-tensioning tendons running along or within the majority of the
length of the supporting girders to provide longitudinal
compression to the deck panels, as presented in U.S. application
Ser. No. 12/857,713.
[0024] U.S. application Ser. No. 12/963,233, by the present
inventor, teaches a solution to introduce pre-compression force
across deck joints via tensioning the supporting girders themselves
under the following condition: [0025] a. Tension is induced in the
supporting girders through the use of compression jacks placed
within gaps provided in the deck system to jack against a jacking
frame apparatus or composite deck panel.
[0026] The proposed method discussed herein also provides a
solution to introduce pre-compression force across deck joints via
tensioning the supporting girders themselves, but applies the
following differing condition from those presented in U.S.
application Ser. No. 12/963,233: [0027] a. Tension is induced in
the supporting girders through the stressing of tensioned
structural elements installed in anchor assemblies at the ends of
the girders supported on intermediate supports.
[0028] Therefore, the method proposed herein does not require the
use of jacks placed within gaps in the deck as presented in U.S.
application Ser. No. 12/963,233.
OBJECTS AND ADVANTAGES
[0029] Accordingly, several objects and advantages of the present
invention are to provide a structural system that: [0030] a.
facilitates rapid construction of a structure consisting of
prefabricated deck units, wherein increasingly tight construction
schedules and/or site constraints can be accommodated; [0031] b.
provides compression across joints between deck units to improve
deck durability by tensioning the bridge girder; [0032] c.
typically increases the overall load resistance of the structure by
tensioning the girder, whereby reducing the amount of material
required in the girders; [0033] d. mitigates the need for deck
closure pours, whereby reducing the cost and time of construction
and potential deck durability compromises [0034] e. facilitates the
use of an deck system with post-tensioning external to the deck for
multi-span concrete girder bridges without requiring the use of a
substantial length of post-tensioning tendons, whereby reducing the
amount of materials required for construction and whereby
construction schedules can be further accelerated.
[0035] Further objects and advantages will become apparent from a
consideration of the ensuing description and drawings.
SUMMARY
[0036] In accordance with the present invention a structural
construction system comprises prefabricated deck units spaced along
longitudinal load-carrying members. Axial compression of these
prefabricated deck units is produced by external tensioned elements
anchored in anchor assemblies integrated with the longitudinal load
carrying members at intermediate support locations. The
prefabricated deck panels are fitted with means to react against
the longitudinal load-carrying members.
DRAWINGS
Figures
[0037] FIG. 1 shows the elevation view of an example bridge used to
describe the present invention.
[0038] FIG. 2 shows the plan view of the example bridge.
[0039] FIG. 3 shows the general cross section of the example
bridge.
[0040] FIG. 4 shows the plan view of a typical deck unit.
[0041] FIG. 4A shows the bulkhead view of a typical deck unit.
[0042] FIG. 4B shows the transverse cross-section of a typical deck
unit.
[0043] FIG. 4C shows the section of a shear key at a typical deck
joint.
[0044] FIG. 4D shows the detail of shear connectors and void for
shear connectors.
[0045] FIG. 5 shows mechanism to apply deck compression force.
[0046] FIGS. 6A-6B show examples of girder connections at the
median pier.
[0047] FIG. 7 shows an example girder connection at the median pier
for an alternate embodiment using concrete girders.
REFERENCE NUMERALS
[0048] 11 girder [0049] 12 abutment [0050] 13 pier [0051] 15
approach slab [0052] 18 precast deck unit [0053] 20 deck joint
[0054] 22 gap at pier between girders [0055] 26 shear studs [0056]
28 shear connector voids [0057] 29 shear keys [0058] 30 haunch
[0059] 32 deck connection unit [0060] 33 post-tensioning bar [0061]
34 anchor assembly [0062] 35 stiffeners [0063] 36 bearing plate
[0064] 37 anchor plate [0065] 38 nut [0066] 51 bearing stiffener
[0067] 52 bottom flange connection plate [0068] 54 high strength
filler [0069] 56 anchor blocks
DETAILED DESCRIPTION
FIGS. 1 Through 7--Preferred Embodiment
[0070] A preferred embodiment of the bridge construction system of
the present invention is illustrated in FIGS. 1 through 5 in the
context of a two-span bridge, hereinafter referred to as "example
bridge". The example bridge has two abutments 12 and an
intermediate pier 13 acting as substructure units. The preferred
embodiment of the bridge construction system is comprised of steel
girders 11 acting as longitudinal load-carrying members, precast
concrete deck units 18 acting as prefabricated deck units. The
precast concrete deck units can be constructed using long or short
line match-casting or without match-casting.
[0071] However, those features comprising the structural
construction system mentioned in the preferred embodiment and the
substructure and span arrangement mentioned above can have various
embodiments not mentioned in the preferred embodiment, as discussed
in detail hereinafter and as will become apparent from a
consideration of the ensuing description and drawings.
[0072] Steel girders 11 are placed on and supported by abutments 12
and pier 13. Steel girders 11 are of fabricated plate girders, but
may be of any suitable structural shape, such as tub girders,
rolled beams, trusses, etc. Bearing stiffeners 51 typical to such
support configurations are provided. A gap 22 between the girder
ends at the pier 13 is provided to allow for relative movement
between the steel girders 11 of each span. On top of girders 11, a
plurality of leveling devices is placed to support the precast deck
units 18 that also allows for relative longitudinal motion between
girders 11 and the precast concrete deck units 18. In the preferred
embodiment, the leveling devices are comprised of shims, however
leveling bolts or other devices that can provide support for the
deck and allow for relative longitudinal motion between girders 11
and the precast concrete deck units 18 can be used. As will be
evident from the description hereinafter, this allowance for
relative motion will allow for the precast concrete deck units to
be compressed by reacting to the tensioning of girders 11. Shims
may be of steel, plastic, elastomeric materials, teflon-based or
teflon-impregnated materials, etc.
[0073] A plurality of voids 28, similar to those used in
conventional precast deck placement, are provided in deck units 18
above girders 11 to allow for mechanical connection of deck units
18 to girders 11 while shear connectors voids 28 are grouted.
Haunches 30 will also be grouted at the same time as the shear
connector voids 28. Shear connectors shall be detailed to allow
relative motion between precast concrete deck units 18 and girders
11 during the precast concrete deck unit erection process and prior
to grouting, as hereinafter described. In the preferred embodiment,
shear connectors are shear studs 26 welded to the girders 11.
[0074] Deck joints 20 between adjacent precast concrete deck units
can be of the match-cast type, with or without epoxy, or
cast-in-place using concrete, grout or other suitable jointing
materials. In the preferred embodiment, match-cast epoxy joints are
used.
[0075] In the preferred embodiment, anchor assemblies 34 are
fabricated with the girders at the ends of the girders supported on
the pier 13, as shown in FIG. 5. Post-tensioning bars 33 acting as
tensioned structural elements are placed within the anchor
assemblies 34. The deck connection unit 32 at each end of the
bridge 245 is made composite prior to any stressing of the
post-tensioning bars 33 so that the deck connection unit 34 will
act as a mounted element that can react the deck compression with
girder tension that results from stressing post-tensioning bars 33.
FIG. 6A and FIG. 6B show that the anchor assemblies 34 consist of
stiffeners 35 and anchor plates 37.
[0076] In the preferred embodiment, the girder connection at the
pier location is simply supported for dead load and continuous for
live load. This is achieved by making the girder bottom flange
connection at pier after all dead loads are applied to the
structure. FIG. 6A and FIG. 6B show examples of the girder
connection at the median pier. The tensile transfer connection near
the top of the girder is made through the post-tensioning bars 33.
When only the post-tensioning bar connection is made, the girder
acts as simply supported in bending moment but can transfer axial
tension. The girder becomes continuous in transferring moment when
both bottom flange and the tensile transfer connections are made.
FIG. 6A shows simply-supported connection configuration and FIG.
67B shows an alternate to connect bottom flanges with high strength
filler material 54 placed between bottom flange connection plates
52. By connecting the bottom flanges, the girder system will act as
continuous under subsequently applied loads.
[0077] Alternate embodiments for the present invention are
described hereinafter: [0078] a. The prefabricated deck units can
be comprised of any other material that is suitable for supporting
loads anticipated to be applied to the deck units, such as
composite material, wood, steel-concrete composite units, etc.
[0079] b. The longitudinal load-carrying members can be comprised
of any other material or cross-section suitable to support the
loads applied to these members such as steel i-girders, precast
prestressed concrete beams, composite material I-girders, single or
multiple box girders of steel or concrete, trusses, wood beams,
etc. [0080] c. Though the preferred embodiment of the present
invention is presented with respect to steel longitudinal
load-carrying members, concrete girders, in particular, prestressed
concrete girders can be readily used. The concrete girders may be
cast with typical formwork with appropriate blockouts for the webs
and flanges in order to provide anchor blocks 56 through secondary
pours. Post-tensioning bars 33 can then be installed through holes
provided in the anchor blocks 56. The tensioning bars can then be
anchored via bearing plates 36 and stressed [0081] d. The girder
connection type at intermediate piers can be other types, such as
simple support for both dead load and live load, or continuous for
both dead load and live load. [0082] e. Though the preferred
embodiment of the present invention is presented in the context of
bridges, it is not limited to bridge applications. Any structural
application requiring decking support by longitudinal load-carrying
members can utilize the present invention in alternate embodiments
such as building floor systems and building roof systems. [0083] f.
In the preferred embodiment, the jacking is applied to the entire
structure, from one end to the other. A structure can consist of
more than one structural unit, where a structural unit is defined
as that to which a jacking force can be applied from one end of the
structural unit to the other, without applying force to other
structural units. [0084] g. Though the preferred embodiment of the
present invention is presented with composite deck connection units
32 acting as mounted elements, cast end blocks, brackets or other
elements affixed to the girders may be provided.
Operation
[0085] The preferred embodiment in the context of the example
bridge is illustrated hereinafter.
[0086] Abutments 12 and pier 13 are constructed. Girders 11 are
erected with anchor assemblies 34 pre-installed. A gap 22 between
the girder ends at the pier 13 is provided to allow for relative
movement between the steel girders 11 of each span.
[0087] The girder top elevation is then surveyed and the shim
thickness at each supporting point calculated so as to provide the
correct setting elevations for deck units. Shims are placed on top
of the girders. Post-tensioning bars 33 are installed within the
anchor assemblies 34 in conjunction with bearing plates 36 and nuts
38. Post-tensioning bars 33 are not stressed at this stage.
[0088] Precast deck units 18 are erected, placing one unit adjacent
to the previously erected one and applying epoxy to the adjacent
faces of the two units. Means is employed to provide a certain
amount of compression over the epoxy joint (typically at 40 psi,
similar to segmental bridge construction) to ensure the joint is
properly set. This process is repeated until all deck units 18 are
installed.
[0089] After all deck units are installed, deck connection units 32
are made composite with the supporting girders by grouting the
shear connector voids 28 and the haunches 30 relative to the deck
connection units. The post-tensioning bars 33 are then stressed.
The nuts 38 are tightened against the bearing plates 36 and anchor
plates 37 in conjunction with the stressing operations to lock in
the stress in the post-tensioning bars 33.
[0090] After the stressing of the post-tensioning bars 33, shear
connector voids 28 and haunches of all remaining deck units are
grouted.
[0091] As an option, the girder bottom flange connection at the
median pier 13 may then made so that the girder connection at pier
location will function as continuous under subsequently applied
loads. This is accomplished by placing high strength filler 54
between the bottom flange connection plates 52.
[0092] The operational description above is particular to the
preferred embodiment of the present invention in the context of the
two-span bridge heretofore defined. Alternate materials, member
shapes, connection types at the median piers, means of stressing,
etc. can be used in employing the structural construction system of
the present invention.
Advantages
[0093] The present invention provides a structural system that
eliminates many of the drawbacks found in current precast deck
construction associated with standard longitudinal post-tensioning.
Notably, it offers an alternate to provide pre-compression across
joints of precast deck units without employment of post-tensioning
tendons and associated ducts in the deck. This significantly
reduces the cost and time of construction required.
[0094] Beyond simply providing a system that eliminates the
drawbacks in current precast deck construction, the present
invention can potentially increase the load carrying capacity of
longitudinal load-carrying members by employing appropriate
connection details at the median pier, and correct construction
steps. In the preferred embodiment, the stressing of the
post-tensioning bars introduces a negative moment at the midspan of
the girders, which offsets part of the girder moment under service
load.
CONCLUSION, RAMIFICATIONS, AND SCOPE
[0095] In conclusion, the present invention provides a structural
construction system utilizing prefabricated deck units that is
durable, easy to construct and cost-effective. The present
invention can accommodate a variety of structural configurations
and can be rapidly constructed.
[0096] Although the description above contains many specificities,
these should not be construed as limiting the scope of the
invention but as merely providing illustrations of some of the
presently preferred embodiments of this invention. For example, as
illustrated and described herein, the present invention can
accommodate a variety of jacking methods and details, a variety of
girder connection methods, and a variety of shapes and materials
for longitudinal load-carrying members.
[0097] Thus the scope of the invention should be determined by the
appended claims and their legal equivalents, rather than by the
examples given.
* * * * *