This invention generally concerns a structural joint, and more specifically concerns a gusset connection that allows greater relative movement between connected structural members and simplifies erection in the field.
The addition of the prior art gusset plate, which can be welded to the beam and column, creates fixity where relative motion of the beam Bm and column C is not possible. In practice, this leads to the introduction of large internal forces applied to portions of the beams and columns.
Shear force Vb is proportional to bending moment Mb and beam clear length Lbc (i.e., Vb∝Mb/Lbc). Likewise, shear force Vc is proportional to bending moment Mc and column clear length Lcc (i.e., Vc∝Mc/Lcc). Increasing the width and height of the gusset plates to strengthen the joints directly reduces the beam clear length Lbc and column clear length Lcc, which in turn causes larger shear forces Vb and Vc to occur for otherwise the same bending moments Mb and Mc applied to the structure by external forces (e.g., winds, earthquakes, etc.). In extreme situations these large internal forces can fracture the beam, the beam to column bolted/welded assembly, the column, and/or the gusset welds, if the prior art connection parts are not designed accordingly. However, if all the prior art connection parts are designed to accommodate the large internal forces, then structure weight, material requirements, and cost increase significantly.
One embodiment of the invention provides a structural joint. A vertical column may have a first gusset portion. A horizontal beam may be connected to the vertical column. The horizontal beam may have a second gusset portion which is not directly connected to the first gusset portion. A diagonal brace may be moveably connected to the first gusset portion and the second gusset portion.
In some aspects, the first gusset portion may be fixedly connected to the vertical column at a joint location. A horizontal beam may be fixedly connected to the vertical column at the joint location. The horizontal beam can have a second gusset portion fixedly connected to the horizontal beam. The second gusset portion may be spaced apart from the first gusset portion at the joint location. The diagonal brace can be moveably connected to the first gusset portion and the second gusset portion at the joint location. The diagonal brace can be moveably connected to the first gusset portion via a first moveable connection. The diagonal brace can be moveably connected to the second gusset portion via a second moveable connection. The first and second moveable connections can be separate from each other.
In some aspects, the first gusset portion and second gusset portions may be first and second gusset plates, respectively, separated by a gap.
In some aspects, the diagonal brace may be moveably connected to at least one of the gusset plates by a plurality of bolts.
In some aspects, the plurality of bolts may pass through horizontally, vertically, or angularly oriented slots of the at least one gusset plate and brace.
In some aspects, the diagonal brace may be also rotatably connected within the gap by a pin.
In some aspects, the first gusset portion and second gusset portion may be stubs. The stubs may be moveably connected to a gusset plate, which may be secured to the diagonal brace.
In some aspects, the stubs may be moveably connected to the gusset plate by a plurality of bolts.
In some aspects, the plurality of bolts may pass through horizontally oriented, vertically oriented, angularly oriented, or curved slots of the stubs and/or the gusset plate and/or the brace.
One embodiment of the invention provides a structural joint including a column. A beam can be fixedly connected to the column at a fixed connection. A brace can be moveably connected to beam and column via a gusset assembly. The beam can be fixedly connected to a first portion of the gusset assembly and the column can be fixedly connected to a second portion of the gusset assembly. A means for moveably connecting the brace to the gusset assembly can be provided such that potentially destructive forces applied to the beam are transferred to the column via the fixed connection and not by the first portion of the gusset assembly, and such that the potentially destructive forces applied to the column are transferred to the beam via the fixed connection and not by the second portion of the gusset assembly.
One embodiment of the invention provides a method for assembling a structural joint. In the method, a beam is fixedly connected to a column to create a joint. A gusset is assembled at the joint for attachment of a brace, or the beam and column can include pre-manufactured gusset portions where the joint is made. A brace can be moveably connected to the gusset such that forces applied to the beam that move the beam do not move the column via transfer of force from the gusset, and such that forces applied to the column do not move the beam via transfer of force from the gusset.
These and other embodiments of the invention are described in further detail below with reference to the following figures.
Embodiments of the invention include a gusset that adds minimal stress to all components it is connected to, such as a beam and column. In this case, the beam, column, and brace see minimal increases in their stresses by adding our gusset. Thus, the advantage of the prior art gusset (to enable brace beam coupling to a column and beam joint) is maintained, while the unwanted force transfer attributes of the prior art gusset (due to large earthquake-like forces) are in large part negated. Accordingly, for a structure having a beam/column/brace joint, when external forces (e.g., earthquake forces) are applied, the inventive gusset will not transfer movement of the beam to the column, movement of the column to the beam, and movement of the brace to the beam and/or column—as would a standard gusset connection. Thus, force transfer between the column, beam, and brace will occur as if the inventive gusset was not present, but instead will mimic true dynamic loads around an imaginary work point that connects all three members. In some embodiments, the inventive gusset itself may also have lower stresses than the prior art gusset. All of this is achieved by allowing greater relative movement between connected members via the inventive gusset connection.
Embodiments of the invention provide a gusset for joining a column, beam, and a diagonal support member for a steel-framed building. The gusset allows for the column and beam to hold and support the diagonal support for the triangulating loads, as is typically expected for a standard prior art gusset. In addition, the gusset also allows the column, beam, and diagonal support to independently move relative to each other in reaction to extreme dynamic loads, which may be the result of extreme winds or earthquakes, and which may also cause a prior-art joint to fail.
Accordingly, relative to a prior art gusset, the inventive gusset does not transfer (significant) movement of the beam to the column, and vice-versa, and thus the gusset does not amplify and/or transfer dynamic loads. For example, a swaying moment enacted on a column will expectedly it to move, and to some degree a beam connected thereto, however the inventive gusset will not transfer the swaying moment onto the beam, and thus not amplify the effects of movement caused by a prior art gusset. The inventive gusset can include a first gusset portion moveably or fixedly connected to a column and a second gusset portion moveably or fixedly connected to a beam. These gusset portions are not directly connected to each other, and are moveably, fixedly, and/or rotatably connected to a diagonal support.
As used herein, “moveably connected” or “moveable” or “moving connection” is understood to mean a connection between two or more structural members which allows for horizontal and or/vertical relative movement between the members under extreme dynamic loading. Such a connection typically does not allow movement under static or typical dynamic loads (e.g., as applied from light/medium force winds). Relative to a prior art bolted gusset, “moveably connected” should be understood to allow movement well beyond drill hole tolerances. An example of a moveable connection is a secured bolt within a slot, which is secured to not move under static or typical dynamic loads, but can move within slots under extreme dynamic loads. Accordingly, slotted bolt connections as described herein should be understood to be moveable connections. It should be well understood, that where slotted connections are disclosed, only one connected portion (e.g., gusset plates, brace) is required to include slots to provide the moveable connection. However, in some embodiments, more than one or all connected portions include slots to provide the moveable connection.
As used herein, “fixedly connected” or “fixed connection” or “non-moveably connected” is understood to mean a connection between two or more structural members which is not configured to provide relative movement (beyond what a prior art bolted gusset provides). An example of a fixed connection is a welded joint or a bolted connection, and in some cases a welded and bolted connection. To some degree, bolt hole tolerances can allow limited movement, however, this may or may not occur under high loads and will certainly be well limited, and thus ultimately mimic a welded connection. Accordingly, welded joints and bolted connections (in the absence of slots) as described herein should be assumed to be fixed connections.
As used herein, “rotatably connected” or “rotatable connection” or “rotating connection” is understood to mean a connection between two or more structural members which allows rotational relative movement between the members. An example of a rotatable connection is a pin joint. Accordingly, pin joints as described herein should be assumed to be rotational connections. However, gusset assemblies having pins situated within a gap will allow for rotational, horizontal and/or vertical relative movement.
As used herein, “force” or “earthquake-like force” or “potentially destructive force” is understood to be dynamic forces externally applied to a building structure that far exceed dynamic loads applied by normal winds and shifting internal building loads. Such forces can be applied from earthquakes, hurricanes, tsunamis, and the like.
The plurality of bolts 202 are moveably connected within slotted bolt holes 204 of the gusset plates 200a/200b and diagonal brace Br. As assembled, the slotted bolt holes 204 are perpendicular to the shown centerline of the gap G, and thus angularly oriented with regards to the structure as a whole. In some embodiments, curved slots may be used. The gap and slots 204 allow the gusset plates 200a/200b to move relative to each other. Accordingly, the beam Bm and column C can move relative to each other (since they are fixedly connected to the gusset plates 200a/200b) effectively as if the gusset was not present, and thus rotate around work point WP1, which is where centerlines of the beam Bm and column C intersect. An alternative work point WP2 is placed at where the centerline of the gap G physically intersects the beam Bm and column C joint. This arrangement prevents the transfer of respective dynamic loads applied to the column C and beam Bm to one another via the gusset plates 202a/202b.
In some embodiments, the bolts are secured to the faces of the gusset plates through an overly large hole instead of a slot using large washers. A polymer, rubber, or soft-metal O-ring may be situated within this overly large hole to help center the bolt and/or absorb shock, vibrations, and forces. The bolts within the slots 204 can be tightened to a degree that is performed with a prior art connection, and in some cases less so or more so. It is expected that earthquake-like forces will be so large to make bolt tightness a non-critical factor. When potentially destructive forces are applied to the gusset assembly 200, it does not behave in the manner depicted in
In some embodiments, only the diagonal brace Br or the gusset plates 200a/200b include the slots, while the other includes tapped holes for the bolt to directly secure to.
One advantage of the invention is the ability to weld the gusset plates 202a/202b to the beam Bm and column C in a shop (i.e., off the construction site) and simply assemble the components using the bolts 202 in the field (i.e., field bolting on the construction site). The prior art arrangement in
This arrangement still allows the relative movement of beam Bm and column C that
Embodiments of the invention are not limited to beam Bm and column C joints. For example,
Embodiments of the invention are not limited to building structures, but can be applied to many load bearing structures that typically use beam and column construction. For example,
The above description is illustrative and is not restrictive. Many variations of the invention will become apparent to those skilled in the art upon review of the disclosure. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the pending claims along with their full scope or equivalents.
One or more features from any embodiment may be combined with one or more features of any other embodiment without departing from the scope of the invention.
A recitation of “a”, “an” or “the” is intended to mean “one or more” unless specifically indicated to the contrary.
This application is the National Stage of International Application No. PCT/US12/25122, filed on Feb. 14, 2012, which claims the benefit of U.S. Provisional Application No. 61/442,738, filed Feb. 14, 2011, which is incorporated by reference herein.
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PCT/US2012/025122 | 2/14/2012 | WO | 00 | 7/14/2014 |
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WO2012/112608 | 8/23/2012 | WO | A |
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