U.S. patent application number 13/759591 was filed with the patent office on 2014-01-23 for braced frame force distribution connection.
This patent application is currently assigned to SEISMIC STRUCTURAL DESIGN ASSOCIATES, INC.. The applicant listed for this patent is Clayton J. ALLEN, James E. Partridge, Rudolph E. RADAU, Ralph M. RICHARD. Invention is credited to Clayton J. ALLEN, James E. Partridge, Rudolph E. RADAU, Ralph M. RICHARD.
Application Number | 20140020311 13/759591 |
Document ID | / |
Family ID | 40796452 |
Filed Date | 2014-01-23 |
United States Patent
Application |
20140020311 |
Kind Code |
A1 |
RICHARD; Ralph M. ; et
al. |
January 23, 2014 |
BRACED FRAME FORCE DISTRIBUTION CONNECTION
Abstract
A structural framework that includes a column, a beam, a brace
beam coupled at an angle to the column and the beam, and a gusset
plate to connect the brace beam with the column and the beam. The
framework also includes a shear plate with horizontally slotted
holes to couple to the column to the beam. The structural framework
may also include double framing angles or a flex plate coupled to
the gusset plate and to the beam via spacer plates to provide for a
semi-rigid connection.
Inventors: |
RICHARD; Ralph M.; (Tucson,
AZ) ; Partridge; James E.; (Pasadena, CA) ;
ALLEN; Clayton J.; (Peoria, AZ) ; RADAU; Rudolph
E.; (Tuscon, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
RICHARD; Ralph M.
Partridge; James E.
ALLEN; Clayton J.
RADAU; Rudolph E. |
Tucson
Pasadena
Peoria
Tuscon |
AZ
CA
AZ
AZ |
US
US
US
US |
|
|
Assignee: |
SEISMIC STRUCTURAL DESIGN
ASSOCIATES, INC.
Los Angeles
CA
|
Family ID: |
40796452 |
Appl. No.: |
13/759591 |
Filed: |
February 5, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12342493 |
Dec 23, 2008 |
8365476 |
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13759591 |
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61006188 |
Dec 28, 2007 |
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Current U.S.
Class: |
52/167.3 ;
52/650.2; 52/745.21 |
Current CPC
Class: |
E04H 9/14 20130101; E04H
9/021 20130101; E04B 2001/2442 20130101; E04B 2001/2415 20130101;
E04C 3/09 20130101; E04B 2001/2448 20130101; E04B 2001/2496
20130101; E04C 2003/0404 20130101; E04H 9/0237 20200501; E04C
5/0645 20130101; E04H 9/028 20130101; E04B 1/24 20130101; E04C 3/02
20130101; E04B 2001/2439 20130101 |
Class at
Publication: |
52/167.3 ;
52/650.2; 52/745.21 |
International
Class: |
E04H 9/02 20060101
E04H009/02; E04H 9/14 20060101 E04H009/14 |
Claims
1. A structural framework comprising: a column; a beam coupled at
an angle to the column; a brace beam coupled at an angle to the
column and the beam; a gusset plate connecting the brace beam with
the column and beam, wherein the gusset plate includes a front face
and a back face; a first framing angle that comprises a first leg
and a second leg at an angle to each other, wherein the first leg
is coupled to the front face of the gusset plate and the second leg
is coupled to the beam; and a second framing angle that comprises a
first leg and a second leg at an angle to each other, wherein the
first leg is coupled to the back face of the gusset plate and the
second leg is coupled to the beam.
2. A structural framework according to claim 1, wherein the column
includes a first column flange, a second column flange and a column
web, wherein the column web connects the first column flange to the
second column flange; and wherein the beam includes a first beam
flange, a second beam flange, and a beam web, wherein the beam web
connects the first beam flange to the second beam flange, wherein
the first beam flange is coupled at an angle to the first column
flange; and wherein the gusset plate connects the brace beam with
the first column flange and the first beam flange.
3. A structural framework according to claim 2, further comprising:
a shear plate coupled to the first column flange and coupled to the
beam web, wherein the shear plate comprises one or a plurality of
horizontally slotted recesses to receive a respective bolt such
that the shear plate is bolted to the beam web.
4. A structural framework according to claim 2, further comprising:
a first spacer plate coupled to the second leg of the first framing
angle and coupled to the first beam flange; and a second spacer
plate coupled to the second leg of the second framing angle and
coupled to the first beam flange.
5. A structural framework according to claim 4, wherein the first
spacer plate and the second spacer plate each comprise one or a
plurality of spacer recesses, wherein the first framing angle and
the second framing angle each comprise one or a plurality of
framing recesses, wherein the first framing angle and the second
framing angle are bolted through the respective framing recesses
and the respective spacer recesses to the gusset plate and to. the
first beam flange.
6. A structural framework according to claim 4, wherein the first
spacer plate and the second spacer plate are welded to the
respective first. framing angle or second framing angle and the
first spacer plate and the second spacer plate are welded to the
first beam flange, and wherein the first framing angle and the
second framing angle are welded to the gusset plate.
7. A structural framework according to claim 2, wherein the gusset
plate is coupled to the first column flange. via a column plate,
the column plate including one or a plurality of recesses, wherein
the column plate is welded to the first column flange and the
column plate is bolted to the gusset plate through the recesses of
the column plate.
8. A structural framework according to claim 2, wherein the first
beam flange is coupled approximately orthogonal to the first column
flange.
9. A structural framework according to claim 2, further comprising:
a slot in the beam web adjacent and parallel to the first beam
flange; and a slot in the column web adjacent and parallel to the
first column flange.
10. A method of extending the useful life of a structural frame,
comprising: connecting a column web to a first column flange and a
second column flange to form a column; connecting a beam web to a
first beam flange and a second beam flange to form a beam; coupling
the first beam flange at an angle to the first column flange;
coupling a brace beam at an angle to the column and the beam;
selecting a gusset plate to connect the brace beam with the first
column flange and the first beam flange, wherein the gusset plate
comprises a front face and a back face; coupling a first framing
angle to the front face of the gusset plate, wherein the first
framing angle includes a first leg and a second leg at an angle to
each other; and coupling a second framing angle to the back face of
the gusset plate, wherein the second framing angle includes a first
leg and a second leg at an angle to each other.
11. A method of extending the useful life of a structural frame
according to claim 10, further comprising: coupling a shear plate
to the first column flange and to the beam web, wherein the shear
plate includes one or a plurality of horizontally slotted recesses
such that the shear plate is bolted to the beam web via the
recesses; coupling a first spacer plate to the second leg of the
first framing angle and to the first beam flange, and coupling a
second spacer plate to the second leg of the second framing angle
and to the first beam flange.
12. A method of extending the useful life of a structural frame,
comprising: connecting a column web to a first column flange and a
second column flange to form a column; connecting a beam web to a
first beam flange and a second beam flange to form a beam; coupling
the first beam flange at an angle to the first column flange;
coupling a brace beam at an angle to the column and the beam;
selecting a gusset plate to connect the brace beam with the first
column flange and the first beam flange, wherein the gusset plate
comprises a front face and a back face; and coupling a flex plate
to the first side of the gusset plate and to the beam, wherein the
flex plate comprises a top side and a bottom side.
13. A method of extending the useful life of a structural frame
according to claim 12, further comprising: coupling a shear plate
to the first column flange and to the beam web, wherein the shear
plate is bolted to the beam web via one or a plurality of
horizontally slotted recesses of the shear plate; coupling a first
spacer plate to couple to the bottom side of the flex plate and the
first beam flange; and coupling a second spacer plate to the bottom
side of the flex plate and the first beam flange.
14. A method for reducing the moment and shear forces in columns
and beams of braced frames when the braced frame is subjected to
lateral loads such as wind and seismic loads, comprising utilizing
the structural framework of claim 1.
15. A method for eliminating buckling of a gusset plate in a braced
frame when the braced frame is subjected to lateral loads, limiting
the damage a column and a horizontal beam of a braced frame,
reducing a size of a beam and a column in a braced frame by
reducing a moment frame action in the braced frame, and/or reducing
the cost of repair of braced frames when damaged by lateral loads,
comprising utilizing the structural framework of claim 1.
16. A method for designing braced frames so that columns and
horizontal beam remain elastic under lateral loading and a frame
brace acts plastically so that a plurality of any damage occurs in
the braces, comprising utilizing the structural framework of claim
1.
17. A method for reducing the moment and shear forces in columns
and beams of braced frames when the braced frame is subjected to
lateral loads such as wind and seismic loads, comprising utilizing
a structural framework, comprising: a column; a beam coupled at an
angle to the column; a brace beam coupled diagonally to the column
and the beam; a gusset plate connecting the brace beam with the
column and beam, wherein the gusset plate includes a first side and
a second side; and a flex plate comprising a top side and a bottom
side, wherein the top side of the flex plate is coupled to the
first side of the gusset plate and the bottom side of the flex
plate is coupled to the beam.
18. A method for eliminating buckling of a gusset plate in a braced
frame when the braced frame is subjected to lateral loads, limiting
the damage a column and a horizontal beam of a braced frame,
reducing a size of a beam and a column in a braced frame by
reducing a moment frame action in the braced frame, and/or reducing
the cost of repair of braced frames when damaged by lateral loads,
comprising utilizing a structural framework, comprising: a column;
a beam coupled at an angle to the column; a brace beam coupled
diagonally to the column and the beam; a gusset plate connecting
the brace beam with the column and beam, wherein the gusset plate
includes a first side and a second side; and a flex plate
comprising a top side and a bottom side, wherein the top side of
the flex plate is coupled to the first side of the gusset plate and
the bottom side of the flex plate is coupled to the beam.
19. A method for designing braced frames so that columns and
horizontal beam remain elastic under lateral loading and a frame
brace acts plastically so that a plurality of any damage occurs in
the braces, comprising utilizing a structural framework,
comprising: a column; a beam coupled at an angle to the column; a
brace beam coupled diagonally to the column and the beam; a gusset
plate connecting the brace beam with the column and beam, wherein
the gusset plate includes a first side and a second side; and a
flex plate comprising a top side and a bottom side, wherein the top
side of the flex plate is coupled to the first side of the gusset
plate and the bottom side of the flex plate is coupled to the
beam.
20. A structural framework according to claim 3, wherein the
horizontally slotted recesses comprise a two to one dimension in a
longitudinal direction.
21. A method of extending the useful life of a structural frame
according to claim 12, further comprising: coupling the first edge
of the flex plate to the first column flange wherein the flex plate
has a first edge and a second edge.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional application of and claims
the priority benefit of co-pending U.S. patent application Ser. No.
12/342,493, filed on Dec. 23, 2008, the entire contents of which
are incorporated herein by reference, and also claims the priority
benefit of U.S. Provisional Patent Application No. 61/006,188,
filed on Dec. 28, 2007, which is also incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] Embodiments of the present invention relate broadly to a
method of construction and design of members of load bearing and
braced frames and their connections to enhance and provide for high
resistance and ductile behavior of the frames when subjected to
loading such as gravity, seismic, and wind loading. More
specifically, embodiments of the present invention relate to the
design and construction of structural frame members and their
connections that use gusset plates to join the beams and columns to
the lateral load carrying frame brace members. Embodiments of the
present invention may be used, but not necessarily exclusively
used, in steel frame buildings, in new construction as well as
modification of existing structures.
BACKGROUND OF THE INVENTION
[0003] In the construction of modern structures such as buildings
and bridges, braced frames including beams, columns, and frame
braces are arranged and fastened or joined together, using known
engineering principles and practices to form a skeletal load
resisting framework of the structure. The arrangement of the beams,
also known as girders, columns, and braces and their connections
are designed to ensure the framework can support the gravity and
lateral loads contemplated for the intended use of the bridge,
building or other structure. Making appropriate engineering
assessments of loads and how these loads are resisted represents
current design methodology. These assessments are compounded in
complexity when considering loads for wind and seismic events, and
determining the forces, stresses, and strains. It is well known
that during an earthquake, the dynamic horizontal and vertical
inertia loads and stresses and strains imposed on a structure have
the greatest impact on the connections of the beams, columns, and
braces which constitute the seismic damage resistant frame. Under
high seismic or wind loading or even from repeated exposure to
milder loadings, the connections in the structure may fail,
possibly resulting in the collapse of the structure and the loss of
life.
[0004] The beams and columns are typically, but not limited to,
conventional rolled or built up steel I-beams, also known as W
sections or wide flange sections, or box sections also known as
tube sections. The frame brace members may have similar shapes as
the beams and columns but may also be single or double angles or
channels or tubular or tee shaped members. The beams, columns and
braces are usually joined using what is known in the structural
engineering profession as gusset plates. The presence of these
gusset plates, which may be typically either bolted or welded to
the joined members, causes the structure members to be rigidly
joined so that the structural frame becomes, in essence, a
braced-moment frame which results in unintentional overloading of
the frame members (Richard 1986). Results of full scale tests
conducted by Tsai et al. (2003), Lopez et al (2002, 2004), Gross
(1990), and Roeder et al. (2004) demonstrate that stiff
beam-column-brace connections attract large force and moment
demands, which can lead to high moments and shears in the beams and
columns. These unintentional high moments and shears in the joined
members of the braced frame can result in premature fracture modes
of the structural members when the frame is subjected to the design
gravity, seismic, and wind loadings because these forces are not
considered in the frame design. Evaluation of the full scale tests
by Walters et al (2004) have shown that in conventionally designed
braced frames, the moment frame action caused by the unintentional
and undesirable beam and column moments and shears alone will
provide a large part of the braced frame's resistance to lateral
loads.
[0005] As previously stated, in conventionally braced frame
designs, moment frame action caused by the gusset plates result in
unintentional and undesirable moments and shears in the beams and
columns. This can lead to fractures in the beam and column flanges
and/or webs when the frame is subjected to lateral seismic or wind
loading. Conventionally braced frame designs resist lateral load in
a combination of braced frame action and moment frame action.
[0006] In the current practice of braced frame design, the
beam-to-column connection at the brace gusset is normally a rigid
welded and/or bolted assembly to the beam and column which creates
a stiff moment resisting connection that generates moments and
shears in the braced frame that are not accounted for in the braced
frame design rationale. Both analytical studies and full scale
tests have demonstrated the drift or displacement related joint
rotation can result in the following potentially serious structural
effects on the components of the braced frame: (1) a pinching or an
in-plane crushing effect of the gusset plate which can lead to the
buckling of the gusset plate; (2) overload of the welds and/or
bolts of the gusset plate connections to the beam and column caused
by the buckling of the gusset plate; (3) yielding and/or fracture
of the beam and column flanges and/or webs due to high moments and
shears in these components due to moment frame action that is not
accounted for in conventional braced frame design rationale; and
(4) unintended moment frame action that resists a large portion of
the braced frame lateral loads rather than braces. This moment
frame action is typically not accounted for in the design of the
braced frame so that the force distribution in the braced frame is
significantly different than the assumed design forces.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The object and advantage of the embodiments of the invention
will become more readily apparent to those of ordinary skill in the
art after reviewing the following detailed description and
accompanying documents wherein:
[0008] FIG. 1A is an example of a diagonal frame brace structural
framework and
[0009] FIG. 1B shows an example of a chevron frame brace structural
framework according to embodiments of the invention;
[0010] FIG. 2 is a magnified view of a conventional connection
amongst the beam, brace, column, and gusset plate connection
according to FIG. 1A;
[0011] FIG. 3A is a beam, column, and gusset plate connection with
a beam web slot and a column web slot according to embodiments of
the invention;
[0012] FIG. 3B is a magnified view of a long slotted hole;
[0013] FIG. 4 is a modification of FIG. 3 that uses a reinforcing
plate for the gusset plate to beam connection according to
embodiments of the invention;
[0014] FIG. 5 is a modification of FIG. 3 that uses a reinforced
concrete slab for additional connection reinforcement according to
embodiments of the invention;
[0015] FIG. 6 is a beam, column, and gusset plate connection with
double framing angles according to embodiments of the
invention;
[0016] FIG. 7 is a beam, column, and gusset plate connection with
double framing angles and spacer plates according to embodiments of
the invention;
[0017] FIG. 8 is a cross-section of FIG. 7 according to embodiments
of the invention;
[0018] FIG. 9 is a magnified view of the deformation of double
framing angles and a gusset plate caused by a load according to
embodiments of the invention;
[0019] FIG. 10 is a beam, column, and gusset plate as an all-bolted
connection according to embodiments of the invention;
[0020] FIG. 11 is a cross-section of FIG. 10 according to
embodiments of the invention;
[0021] FIG. 12 is a is a beam, column, and gusset plate connection
utilizing a flex plate and spacer plate connection according to
embodiments of the invention;
[0022] FIG. 13 is a cross-section of FIG. 12 according to
embodiments of the invention;
[0023] FIG. 14 is a cross-section of a beam, column, and gusset
plate connection with a double flex plate and spacer plate bolted
connection according to embodiments of the invention;
[0024] FIG. 15 is a cross-section of a beam, column, and gusset
plate connection with a double flex plate and spacer plate welded
connection according to embodiments of the invention; and
[0025] FIG. 16 is a graph showing the distribution of lateral
forces between the moment frame components and the frame brace in a
single story braced frame as a function of the story drift or
displacement according to embodiments of the invention.
DETAILED DESCRIPTION
[0026] An embodiment of the present invention provides a new and
improved beam-to-column-to-brace connection, which includes a
gusset plate, that reduces the bending moments and shears in the
beams and columns of conventionally joined braced frames when the
structural framework may be subjected to gravity and lateral loads
such as those caused by wind and seismic loadings. The improved
connection may extend the useful life of new braced framed
structures, as well as that of braced frames in existing structures
when incorporated into a retrofit modification for existing
structures
[0027] The moments and shears in the beams and columns may be
reduced by two ways. First, a flexure mechanism may be provided to
transfer the horizontal forces in the gusset plate to the beam.
Second, a shear plate may be provided to bolt the beam web to the
column flange connection such that the shear plate includes
horizontally slotted holes.
[0028] The flexure mechanism may include either (1) a beam web slot
under the gusset plate that separates the beam flange from the beam
web or (2) a flexure plate or double framing angles assembly using
spacer plates that transfers the gusset plate forces to the beam
flange. These flexure mechanisms essentially may eliminate the
pinching frame action that leads to buckling and collapse of the
gusset plate. The flexure mechanisms also may reduce the moments
and shears in the column.
[0029] A shear plate with horizontally slotted holes to connect and
bolt the beam web to the column may eliminate the connection moment
caused by the horizontal bolt forces in the beam web and the
horizontal force in the gusset plate to column connection.
[0030] In one embodiment according to the invention, the structural
frames resist lateral loads in a truss-like action consistent with
braced frame design rationale which differs from conventionally
braced frame designs as explained above. Conventionally braced
frame designs resist lateral load in a combination of braced frame
action and moment frame action.
[0031] Embodiments of the invention may reduce the stresses and
strains in the joined members caused by moment frame action when
the braced frame is subjected to lateral loadings such as wind or
seismic events; may reduce or eliminate the undesirable effects of
the kinematic end rotation of the brace and thereby improve the
performance of the brace in resisting the braced frame lateral
load; and/or may limit the forces in the beams and columns of the
braced frame to primarily axial forces when the braced frame is
subjected to lateral loadings, such as wind or seismic events.
[0032] Additional embodiments of the invention may limit the forces
in the beams and columns of the braced frame to primarily axial
forces to prevent damage to these components when the braced frame
is subjected to lateral loadings such as wind or seismic events;
may allow for joint rotations in the braced frame which reduces the
moments and shears in the members of the braced frame; may either
reduce or eliminate the need for beam web stiffeners in the
proximity of the gusset plate; and/or may eliminate the need for
horizontal and/or vertical stiffeners on the gusset plate.
[0033] Embodiments of the invention may prevent damage to the
braced frame beams and columns when the braced frame is subjected
to seismic loading by keeping the beams and columns essentially
elastic and allowing only the braces to be stressed to their yield
loads; may reduce the residue displacements in the braced frame
after the frame has been subject to seismic forces; may reduce the
size of the gusset plates that are required in conventionally
designed braced systems; and/or may move the working point in
conventionally braced frames from the intersection of the
centerlines of the beam and column to the intersection of the beam
and column flange thereby reducing the size of the gusset
plate.
[0034] The embodiments of the invention may reduce the rigidity of
the welded and/or bolted gusset plate connection assembly. A
reduction in rigidity may eliminate or significantly reduce the
moments and shears in the beam, column, and brace when the braced
frame is subjected to lateral drift or displacement. Such lateral
drift may be due to wind or seismic loading. To this end, the
embodiments of the invention may provide for a hinging or flexure
mechanism in the beam or in the gusset plate to beam
connection.
[0035] The effect of the hinging or flexure mechanism may create a
large reduction in the beam and column moments which essentially
may eliminate the moment frame action in the braced structural
frame. The hinging or flexure mechanism may also reduce the moment
and shears in the brace and also may allow the gusset plate to
rotate with the drift of the frame and thereby may reduce the
tendency for the gusset plate to buckle or collapse. Gusset plate
buckling may result in the fracture of the gusset plate connection
to the beam and/or column. Moreover, the hinging or flexural
mechanism may reduce the possibility of unintentional large moments
and shears in the columns could result in the development of
plastic hinges in the columns of the braced frame.
[0036] Embodiments of the invention may also provide for the braces
to absorb or dissipate substantial amounts of energy when the frame
may be subjected to lateral loads such as seismic and wind loads.
The braces, which may react most effectively in a uniaxial state of
stress, may provide for efficient use of material thereby achieving
a robust structural system. Additionally, the lateral force
resisting elements of the braced frame may be economically and
expeditiously restored by replacing flexural elements and the
braces if damaged by lateral wind or seismic loading.
[0037] Referring to FIG. 1A and FIG. 1B, there is shown examples of
structural assemblies according to the embodiments of the
invention. FIG. 1A depicts columns 1, beams 2, and diagonal frame
brace members 8 to form the skeletal structural framework. Figure
lab shows a structural framework that utilizes chevron bracing with
frame brace members 8'. Gusset plates 3 create the connection among
the columns 1, beams 2, and diagonal frame brace members 8, 8'. The
gusset plates of FIG. 1A and FIG. 1B may be connected to the
columns 1, beams 2, and frame brace members 8, 8' by conventional
techniques such as bolting, welding, pinning, or any combination
thereof. Both the diagonal bracing of FIG. 1A and the chevron
bracing of FIG. 1B may resist loads such as seismic or wind loads
to maintain the structural integrity of the frame.
[0038] FIG. 2 shows an example of a conventional connection with a
column 100, beam 200, brace member 800, and gusset plate 300
connection according to FIG. 1A. The column 100 may include a first
column flange 101, a second column flange 102, and a column web 104
between the first column flange 101 and the second column flange
102. An example of a column 100 used in the structural framework
may include a wide flange or I beam of 14 inches by 176 pounds per
foot [W14.times.176 (360.times.262)] column. The beam 200 may
include a first beam flange 201, a second beam flange 202, and a
beam web 204 between the first beam flange 201 and the second beam
flange 202. An example of a beam 200 used in the structural
framework may include a wide flange or I beam of 27 inches by 94
pounds per foot [W27.times.94 (690.times.140)] beam. A gusset plate
300 may connect the frame brace member 800 to the column 100 and
the beam 200. The gusset plate may be provided with a pin hole
brace attachment detail 306 to join the frame brace member 800 to
the gusset plate 300. Other connections between the gusset plate
300 and the frame brace member 800 may be used such as a bolted
detail attachment.
[0039] The gusset plate 300 may be coupled to the first column
flange 101 of the column 100. The gusset plate 300 and first column
flange 101 may be coupled by a weld connection. The gusset plate
300 may be coupled to the first beam flange 201 of the beam 200 by
a weld connection. Conventional stiffeners 302, 304 may be welded
to the edges of the gusset plate 300 to provide extra strength to
the framework. A vertical beam stiffener 207 may be welded to the
beam web 204 to provide reinforcement.
[0040] The beam 200 may be joined to the column 100 via a shear
plate 400. A space L may be provided between the first column
flange 201 and the beam web 204. The shear plate 400 may connect to
the beam web 204 and to the first column flange 101. The shear
plate 400 may be coupled to the first column flange 101 via a shop
weld connection. The shear plate may also include round holes 412
to receive bolts to make the connection.
[0041] Structural analysis shows that when a structural framework
such as the framework depicted in FIG. 2 is subject to certain
loads, the angle between the column 100 and the beam 200 tends to
close when the force due to the frame brace member 800 is in
tension. The decrease in angle may cause the column 100 and beam
200 to crush and buckle the gusset plate 300. The structural action
results in undesirable and unintended moment and shear forces in
the beam 200 and column 100. Examples of such loads that may cause
the angle to decrease are a lateral seismic load or a wind
load.
[0042] FIG. 3A shows another example of a structural framework. The
beam 200 may include a beam web slot 208 adjacent to the first beam
flange 201. The column 100 may include a column web slot 108
adjacent to the first column flange 101. The slots 108, 208 and
additionally long slotted holes 402 of the shear plate 400, may
reduce the moment and shear forces in the beam 200 and the column
100 when the structural frame may be subject to lateral forces. In
this FIG. 3A, the second beam flange may be stabilized with a
stabilization plate 206 that is attached to the beam 200 and the
column 100. The first beam flange 201 may be connected to the first
column flange 101 via a complete joint penetration (CJP) weld
210.
[0043] FIG. 3B shows a detail of an oblong long slotted hole 402
with a width W and a height H. These holes 402 may be specified by
the American Institute of Steel Construction (AISC). The
longitudinal direction of the long slotted hole may be twice the
dimension as the width. The shear plate 400 may include a long
slotted hole 402. The long slotted hole 402 may receive a bolt so
that the shear plate 400 may be bolted to the beam web 204.
[0044] FIG. 4 shows another exemplary embodiment of the invention.
An additional reinforcement plate 220 may be attached to the gusset
plate 300 and the first beam flange 201 to provide additional
connection strength if necessary.
[0045] FIG. 5 is a modification of the exemplary embodiment of FIG.
4. A concrete deck 230 with a reinforcement bar 232 may be provided
above the stabilization plate 220 to increase the strength of the
connection.
[0046] FIG. 6 shows another exemplary embodiment according to the
invention. The gusset plate 300 may be attached to the first beam
flange 201 via double framing angles 360. The double framing angles
may include long slotted holes 362. The gusset plate 300 may also
include the long slotted holes 362 for the attachment. The long
slotted holes 362 may receive bolts. The bolts are tightened only
snug tight so that when the structural frame may be subject to
lateral loads, the bolts slip and reduce the moment and shear
forces in the column 100 and the beam 200.
[0047] The beam 200 may be connected to the column 100 via a shear
plate 400 connection. The beam web 204 may be bolted to the shear
plate 400 and the shear plate 400 may be welded to the first column
flange 101. The shear plate may have long slotted holes 402 that
are able to receive bolts. The bolts may also have a snug tight fit
to allow for a semi-rigid connection. The long slotted holes with
the snug tight bolts allow the structural frame to have more
elasticity and allow the connections to be less rigid than
conventional connections. The long slotted holes 402 in the shear
plate 400 restrict the bolts to resisting only vertical loads.
[0048] FIGS. 7 and 8 depict a further embodiment according to the
invention. In this embodiment, the structural framework is under a
compressive force 380 due to the frame brace member 800 (not
depicted here). The gusset plate 300 is connected to the beam 200
via double framing angles 360 and spacer plates 366. The double
framing angles 360 may include circular holes 112 but may
alternatively include long slotted holes. The framing angle 360 may
include a vertical plate or leg 364 and a horizontal plate or leg
365. The horizontal plate 365 may rest upon spacer plates 366. The
double framing angles 360 may be connected to the first beam flange
201 by bolts 111 via the spacer plates 366.
[0049] As depicted in FIG. 8, the thickness of the spacer plates
determines the height of a space between the horizontal plate 365
and the first beam flange 201. The spacer plates 366 allow the
double framing angles 360 to flex when the structural frame may be
subjected to lateral loads. The spacer plates 366 with the double
framing angles 360 may reduce the moment and shear forces in the
frame by providing a flexible beam to column connection.
[0050] As in FIG. 6, FIG. 7 shows that the beam web 204 may be
bolted to the shear plate 400. The long slotted holes 402 in the
shear plate 400 restrict the bolts to resisting only vertical
loads.
[0051] FIG. 9 shows the flexible nature of the double framing
angles 360 according to embodiments of the invention. The double
framing angles 360 deflect and deform in the manner shown as the
dotted lines of 360' when the structural frame may be subject to a
load. The deformation 360' may cause the bolts 112 and the gusset
plate 300 to likewise deform as shown in the dotted lines of FIG.
9.
[0052] FIGS. 10 and 11 show another exemplary embodiment of the
invention. FIG. 11 is a cross-section of FIG. 10 along the dotted
lines of FIG. 10. In this embodiment as depicted in FIG. 11, a flex
plate 501 may be provided to complete the gusset plate 300 to the
beam flange 201 connection. The flex plate 501 may be welded to a
vertical plate 500 via welds 600A. The vertical plate 500 may be
connected to the gusset plate 300 by a plate 400'. The plate 400'
may have one or a plurality of holes 402' to receive bolts to
secure the gusset plate 300 to the plate 400'. The flex plate 501
may be connected to the first beam flange 201 by spacer plates 366
and bolts 111. The thickness of the spacer plates 366 may determine
the distance the flex plate 500 is elevated from the first beam
flange 201. The beam web 204 may be connected to the first column
flange 101 by a shear plate 400.
[0053] FIGS. 12 and 13 show yet another exemplary embodiment of the
invention. FIG. 13 is a cross-section of FIG. 12 at the dotted
lines of FIG. 12. In this embodiment, the gusset plate 300 may be
welded via a welds 600 to the flex plate 501. Other connections may
be possible to connect the gusset plate 300 to the flex plate
501.
[0054] FIGS. 14 and 15 are further embodiments of the present
invention. FIGS. 14 and 15 are modifications of FIG. 11. A double
flex plate assembly may be used for the connection of the gusset
plate 300 to the first beam flange 201. The flex plate 501 is
welded to the vertical plate 500 via welds 600A. A second flex
plate 502 is arranged on the first beam flange 201. Spacer plates
367 are sandwiched between the flex plate 501 and the second flex
plate 502. FIGS. 14 and 15 differ in their ways of connecting the
components of the structural framework.
[0055] FIG. 14 utilizes bolts to connect the flex plate 501 to the
second flex plate 502 to the first beam flange 201. The spacer
plates 367 are bolted to both flex plates 501, 502 by bolts 113.
The second flex plate 502 may be bolted to the first beam flange
201 by bolts 114.
[0056] FIG. 15 utilizes bolt and weld connections. As in FIG. 14,
the flex plate 501 is welded to the vertical plate 500 via welds
600A. The flex plate 501 is bolted to the spacer plates 367 by
bolts 113. FIG. 15 differs from FIG. 14 in that the second flex
plate 502 may be welded to the first beam flange 201 via welds 601.
The configurations of FIGS. 14 and 15 may use other connections
practiced in the field. The double flex plates connection may
provide a flexible beam to column connection so that any
deformation in the beam or column may be elastic.
[0057] FIG. 16 depicts a graph of the projected distribution of the
frame brace forces in a structural single story braced frame as a
function of lateral displacement of the frame under loads according
to the flexible connections of embodiments of the invention. An
example of such structural frame is the chevron frame of FIG. 1B.
Examples of the loads to be exerted on the structural frame are
seismic and wind loading.
[0058] The analysis in FIG. 16 depicts the results of a structural
framework tested the structural framework according to the
embodiment shown in FIG. 13 which shows a flex plate design. The
analysis utilized a wide flange or I beam of 21 inches by 93 pounds
per foot (W21.times.93) and a wide flange or I column of 14 inches
by 176 pounds per foot (W14.times.176). The area of the frame brace
is 6.33 inches squared (6.33 in\ For a 2% (0.02) drift or
displacement of the structural framework, the lateral displacement
of the structural frame is calculated as 2.4 inches.
[0059] A total lateral force of 664677 pounds was calculated to
cause the lateral displacement of 2.4 inches. The frame brace
members experience a horizontal force component of 263639 pounds in
tension and -285430 pounds in compression. Therefore, the total
force resisted by the frame brace members is 549069 pounds (263639
lbs.+285430 lbs.=549069 lbs.). The force of 549069 lbs. represents
82.6% of the total lateral force of 664677 pounds calculated for
the 2% drift (549069/664677=0.826). This means that the frame brace
members resist 82.6% of the lateral load. The rest of the load is
exerted on the beams and the columns (664677-549069=115608 lbs).
This represents that merely 17.4% of the total lateral load is
resisted by the beams and the columns (115608/664677=0.174).
[0060] Typically, in braced frames of the type shown in FIGS. 1A
and 1B with a rigid connection such as FIG. 2, only 50% of the
lateral load is resisted by the frame brace members. The rest of
the 50% of the lateral load is resisted by the beams and columns.
With the embodiments of the invention, the frame brace members
resist approximately 32.6% more of the lateral load than the frame
brace members with conventional rigid connections.
[0061] The results of the experiment and graph show that the flex
plate design is a flexible semi-rigid connection. It allows the
gusset plate and the frame brace members to deform plastically
while allowing the beams and the columns to elastically deform
under a given load. Such result may allow the columns and beams to
maintain their structural integrity and allow for easy replacement
of the plastically deformed brace frame members and gusset
plates.
* * * * *