Note: Descriptions are shown in the official language in which they were submitted.
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FLANGE-TO-FLANGE CONNECTION OF
PRECAST CONCRETE MEMBERS
TECHNICAL FIELD
pocril The present disclosure generally relates to the field of construction
and
more particularly to connection of precast concrete members,
BACKGROUND
[0002] A double tee beam is a load-bearing structure that resembles two T-
beams connected to each other side by side. The strong bond of the flange
(horizontal component) and the two vertical components (also known as
stems) creates a structure that is capable of withstanding high loads while
having a long span. Floor systems of modern parking structures, for
example, use precast double tee beams, which are joined flange-to-flange
using connectors anchored in the flange of the double tee beams, to form an
integral multi-beam floor.
[0003] A type of conventional flange-to-flange connector uses a thin twisted
plate pre-embedded in the flange, Two twisted plates aligned with each other
across the gap between double tees are welded together at the jobsite using
a loose steel plate to connect the flanges. This type of flange-to-flange
connector creates a flexible connection, which has been criticized for lack of
fatigue capacity and failure of welds if the welding is not done properly by
certified welders. In addition, this type of flange-to-flange connector
requires
caulking (sealant) to seal the gap between the flange edges, with a life
expectancy of five to ten years, thus requiring significant maintenance
expenses.
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SUMMARY
[0004] An embodiment of the present disclosure is directed to an apparatus.
The apparatus may include a first anchored plate secured to a first set of
anchoring bars and a second anchored plate secured to a second set of
anchoring bars. The apparatus may also include a first alignment plate
configured to mate with the first anchored plate and a second alignment plate
configured to mate with the second anchored plate. The apparatus may
further include at least one shim configured to be positioned between the
first
anchored plate and the second anchored plate. A bolt may be configured to
secure the first and second alignment plates with the first and second
anchored plates, respectively, and when the bolt is tightened, the bolt pulls
the first and second alignment plates and the first and second anchored
plates together to form a rigid connection.
[0005] A further embodiment of the present disclosure is directed to a
structure, The structure may include a first concrete member and a second
concrete member connected to the first concrete member utilizing a plurality
of connectors. Each connector may include a first anchored plate secured to
the first concrete member and a second anchored plate secured to the
second concrete member. Each connector may also include a first alignment
plate configured to mate with the first anchored plate and a second alignment
plate configured to mate with the second anchored plate. At least one shim
may be configured to be positioned between the first anchored plate and the
second anchored plate, and a bolt may be configured to secure the first and
second alignment plates with the first and second anchored plates,
respectively, wherein when the bolt is tightened, the bolt pulls the first and
second alignment plates and the first and second anchored plates together to
form a rigid connection between the first concrete member and the second
concrete member.
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[0006] An additional embodiment of the present disclosure is directed to a
method. The method may include: providing a plurality of connectors for
connecting a first concrete member to a second concrete member, each of
the plurality of connectors comprising a first anchored plate secured to the
first concrete member and a second anchored plate secured to the second
concrete member; bolting each of the plurality of connectors using a bolt,
further comprising: providing a first alignment plate configured to mate with
the first anchored plate; providing a second alignment plate configured to
mate with the second anchored plate; positioning at least one shim between
the first anchored plate and the second anchored plate; and tightening the
bolt to pull the first and second alignment plates and the first and second
anchored plates together to form a rigid connection between the first concrete
member and the second concrete member; and sealing one or more gaps
between the first concrete member and the second concrete member.
[0007] It is to be understood that both the foregoing general description and
the following detailed description are exemplary and explanatory only and are
not necessarily restrictive of the present disclosure. The accompanying
drawings, which are incorporated in and constitute a part of the
specification,
illustrate subject matter of the disclosure. Together, the descriptions and
the
drawings serve to explain the principles of the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[Hos] The numerous advantages of the disclosure may be better understood
by those skilled in the art by reference to the accompanying figures in which:
FIG. 1 is an isometric view of a flange-to-flange connector in
accordance with the present disclosure;
FIG. 2 is an exploded view of a flange-to-flange connector;
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FIG. 3 is an isometric view of the flange-to-flange connector shown in
FIG. 2 in a fully assembled configuration;
FIG. 4 is a cross-sectional top view of a properly aligned flange-to-
flange connector;
FIG. 5 is a cross-sectional top view of a misaligned flange-to-flange
connector due to normal construction tolerances;
FIG. 6 is an exploded view of a flange-to-flange connector similar to
Fig. 2 but for a larger flange and load transfer;
FIG. 7 is an illustration depicting a construction method configured to
securely join two precast concrete members using flange-to-flange
connectors in accordance with the present disclosure; and
FIG. 8 is an illustration depicting shear keys that may be defined in the
gaps between two precast concrete members in accordance with the present
disclosure.
DETAILED DESCRIPTION
[0009] Reference will now be made in detail to the subject matter disclosed,
which is illustrated in the accompanying drawings.
[00101 Embodiments in accordance with the present disclosure are directed to
flange-to-flange connectors for precast concrete members (e.g., double tee
beams) and construction methods using such flange-to-flange connectors.
The flange-to-flange connectors disclosed herein are easy to install, easy to
maintain, and are intended to provide structural performance comparable to
monolithically and continuously placed concrete between the stems of precast
concrete flanged members. The flange-to-flange connectors disclosed herein
also allow for generous construction tolerances and misalignments, which
may be appreciated for various reasons.
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[0011] Referring generally to FIGS. 1 through 6, a flange-to-flange connector
100 configured in accordance with an embodiment of the present disclosure
is shown. The flange-to-flange connectors 100 can be utilized to securely join
two precast concrete members 102 and 104 together using only bolted
connections, effectively eliminating the requirement for certified welders and
issues associated with low fatigue capacity of welded connectors and
excessive deflections and rotations of the flange edges,
[0012] As shown in FIGS. 1 and 2, the flange-to-flange connector 100
configured in accordance with the present disclosure includes a pair of
anchored plates 106 secured to their respective anchoring bars 114, which
are anchored in the precast concrete members 102 and 104. The anchoring
bars 114 may be shop-welded (which is a common practice in the precast
concrete industry) to the anchored plates 106 in some embodiments.
However, if fatigue capacity is a concern, the anchoring bars 114 may be
implemented as headed bars, for example, which can be secured to the
anchored plates 106 without welding at all. It is contemplated that the
anchoring bars 114 may range from approximately 3/8 inches to 1 and 1/4
inches in diameter and approximately 12 inches or greater in length. In some
embodiments, the anchoring bars 114 may extend the full width of the precast
concrete members 102 or 104, and doubly used as the base reinforcement in
the flanges. Alternatively, shorter anchoring bars 114 may be utilized to
serve
similar purposes, as long as the anchoring bars 114 are positioned to create
continuity with the flange base reinforcement to allow the tensile forces to
be
transmitted across the double tee flanges.
[0013] The anchored plates 106 may be formed using ductile steel casting,
but other techniques and/or materials may be utilized to form the anchored
plates 106 without departing from the spirit and scope of the present
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disclosure. The anchored plates 106 may be configured to satisfy certain
structural requirements, so the height, width, and/or the thickness of the
anchored plates 106 may vary without departing from the spirit and scope of
the present disclosure. In a particular implementation where the flange-to-
flange connector 100 is used to connect 4-inch thick flanges for a parking
structure, for example, the height of the anchored plates 106 may be
configured to be approximately 2 inches to allow for concrete cover of
approximately 1 inch on the top and the bottom of the anchored plates 106,
[0014] In some embodiments (e.g., as shown in FIG. 2), the anchored plates
106 may define one or more longitudinal indentations (grooves) 108
extending longitudinally (horizontally with respect to the orientation
presented
in FIG. 2) along at least a portion (e.g., approximately 5 inches along the
width) of the anchored plates 106. The anchored plates 106 may also define
one or more transverse indentations (teeth) 110 extending transversely
(vertically with respect to the orientation presented in FIG. 2) along at
least a
portion of the anchored plates 106.
[0015] The grooves 108 and the teeth 110 may be defined in this manner to
help properly and securely receive a pair of alignment plates 118. In some
embodiments, the alignment plates 118 may define lugs 120 and teeth 122
that are configured to mate with the grooves 108 and the teeth 110 defined on
the anchored plates 106. A bolt 116 and a nut 120 may be utilized to secure
the alignment plates 118 against their corresponding anchored plates 106.
The bolt 116 may range from approximately 3/4 inches in diameter (e.g.,
ASTM A325 grade 120 ksi) to approximately 1 and 3/8 inches in diameter
(e.g., ASTM A490 grade 150 ksi) or greater. The nut 120 may be configured
according to the capacity of the bolt 116.
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[0016] In some embodiments, the anchored plates 106 may define openings
112 that are large enough to accommodate the diameter of the bolt 116. It is
contemplated, however, that the openings 112 may be designed to provide a
longitudinal tolerance (e.g., an extra inch) in certain embodiments. As shown
in FIG. 5, defining the openings 112 with a tolerance effectively allows the
flange-to-flange connector 100 to accommodate anchored plate 106
misalignments up to the tolerance provided by the openings 112, which may
be appreciated in various applications.
[0017] It is also contemplated that the openings 112 may be designed as U-
shaped openings, allowing the bolt 116 to be received directly from the top
(with respect to the orientation presented in FIG. 2) of the anchored plates
106, which is a feature that may be appreciated in certain (e.g., space-
constrained) applications. It is to be understood, however, that the openings
112 are not required to be designed as U-shaped openings. The openings
112 depicted in FIG. 6, for example, do not define U-shaped openings;
instead, the openings 112 depicted in FIG. 6 only allows the bolt 116 to be
received from the side (with respect to the orientation presented in FIG. 6)
of
the anchored plates 106.
[0018] It is further contemplated that the flange-to-flange connector 100 may
be designed to accommodate gaps that may exist between the anchored
plates 106. In some embodiments, one or more shims 124 may be utilized to
fill such a gap 126. The shims 124 may be made of materials such as hard
plastic or the like. As the bolt 116 is tightened, the alignment plates 118,
the
anchored plates 106, and the shims 124 are all pulled together, effectively
forming a rigid connection that provides structural performance comparable to
monolithically and continuously placed concrete between the stems of precast
concrete flanged members. It is noted that the rigid connections formed using
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flange-to-flange connectors 100 configured in accordance with the present
disclosure eliminate the need to form and cure concrete at job sites, allowing
the time, cost, and construction complexity to be reduced significantly
compared to conventional construction methods.
[0019] Referring now to FIG. 7, a construction method 200 configured to
securely join two precast concrete members 102 and 104 using flange-to-
flange connectors 100 in accordance with the present disclosure is shown.
More specifically, the flange-to-flange connectors 100 located along the two
precast concrete members 102 and 104 may be bolt connected in a step 202.
It is noted that the step 202 may be carried out according to a particular
bolting sequence because even though the two precast concrete members
102 and 104 may be substantially identical, there is still a possibility that
the
top surfaces of the precast concrete members 102 and 104 may not be
exactly aligned at the same elevation at each connection location. It may
therefore be appreciated to start the bolting sequence at the opposite ends of
the two precast concrete members 102 and 104 and work toward the center.
Weights may be applied to the member (102 or 104) located at the higher
elevation to force vertical alignment of the two members. The grooves and
the lugs previously described will provide the necessary fine tuning of the
vertical alignment. Once all the bolts are installed and tightened, another
round of tightening may be performed using a technique known as snug
tightening.
[0020] After the bolts are adequately snug-tightened, flowable high strength
low shrinkage grout may be poured into the gap between the precast
concrete members 102 and 104 in a step 204. The bottom of the gap may be
filled with backer rod and sealed with a sealant to prevent grout from
leaking.
In some embodiments, the gap between the precast concrete members 102
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and 104 may form (optional) shear keys as depicted in FIG. 8 (and also in
FIG. 1). It is contemplated that these shear keys may provide resistance to
vertical and longitudinal shear in the plane formed by the precast concrete
members 102 and 104.
[0021] It is to be understood that while the flange-to-flange connectors 100
configured in accordance with the present disclosure may be utilized for
constructing parking structures, the references to parking structures are
merely exemplary and are not meant to be limiting. It is contemplated that the
flange-to-flange connectors 100 configured in accordance with the present
disclosure may be produced in various dimensions, sizes, or shapes for
various purposes without departing from the spirit and scope of the present
disclosure. It is contemplated that dimensions, sizes, shapes, and hardware
implementations of flange-to-flange connectors configured in accordance with
the present disclosure may vary from the descriptions above without
departing from the spirit and scope of the present disclosure.
[0022] The herein described subject matter sometimes illustrates different
components contained within, or connected with, different other components.
It is to be understood that such depicted architectures are merely exemplary,
and that in fact many other architectures can be implemented which achieve
the same functionality. In a conceptual sense, any arrangement of
components to achieve the same functionality is effectively "associated" such
that the desired functionality is achieved. Hence, any two components herein
combined to achieve a particular functionality can be seen as "associated
with" each other such that the desired functionality is achieved, irrespective
of
architectures or intermedial components. Likewise, any two components so
associated can also be viewed as being "operably connected", or "operably
coupled", to each other to achieve the desired functionality, and any two
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components capable of being so associated can also be viewed as being
"operably couplable", to each other to achieve the desired functionality.
[0023] It is believed that the present disclosure and many of its attendant
advantages will be understood by the foregoing description, and it will be
apparent that various changes may be made in the form, construction and
arrangement of the components without departing from the disclosed subject
matter or without sacrificing all of its material advantages.
