Static structures (e.g. – buildings) – Module or panel having discrete edgewise or face-to-face... – With joining means of dissimilar material and separate from...
Reexamination Certificate
1999-06-16
2001-02-13
Kent, Christopher T. (Department: 3635)
Static structures (e.g., buildings)
Module or panel having discrete edgewise or face-to-face...
With joining means of dissimilar material and separate from...
C052S699000, C052S601000, C052S715000, C052S582100
Reexamination Certificate
active
06185897
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a flange connector or metal weldable piece that is cast in the flanged edge of a concrete slab type structure such as a concrete structural tee. The flange connector of the present invention is used to adjoin adjacent concrete structural members by welding a lug or rod to adjacent flange connectors that are embedded in adjoining concrete structural members.
BACKGROUND OF THE INVENTION
Precast concrete structural members are widely used throughout the building industry because of the structural properties, ready availability and low costs of the members. The precast members are typically used to construct decks, such as roofs or floors, in large concrete structural members, such as parking garages. The precast members are manufactured in a facility and then shipped to the job site and erected. The precast members are typically double tee concrete structures, as illustrated in FIG.
6
.
Each double tee member has a slab or load bearing surface and includes two flanged edges and two joists. To form a deck, long span, double tee precast members are laid side-by-side one another so that the flanged edges of members are abutting. These members may move relative to one another due to wind forces, thermal expansion and load changes. To prevent or lessen the relative horizontal and vertical movement between the abutting members and to provide added strength and rigidity to the structure, metal pieces may be embedded into the flanged edges of the members. Opposing metal pieces are then welded together with a lug or rod to provide the joinder. The metal pieces are commonly called weldments, weld plates or flange connectors.
At present, typical flange connectors are formed of one-piece metal members comprising (1) a front central plate having a planar weldable surface along one edge of the central plate member and (2) a pair of outstanding arms extending from the central plate member that are embedded in the concrete slab. The flange connectors are cast into the flanged edges of the double tee concrete structure typically at four to five foot centers, varying upon the size of the double tee structure and the amount of expected loading of the structure. The flanged edges are cast in the concrete structure such that the top edge of the central plate member of the flange connector is exposed. Exposing the top edge is accomplished by blocking out a portion of the flanged edge of the concrete member just above the central plate member. Having the top edge exposed allows two adjacent connectors to be welded to a lug or rod positioned between the two adjacent connectors, thereby developing a diaphragm across the floor or roof to increase the rigidity of such floor or roof. Because the opposing connectors often do not align perfectly with one another, a lug or rod is positioned between the opposing connectors. Rather than being welded directly to one another, the connectors are then welded to the intermediary lug or rod.
Examples of such typical flange connectors can be found in Ehlenbeck, U.S. Pat. No. 3,958,954, Lowndes, III, U.S. Pat. No. 4,724,649 and Klein, U.S. Pat. No. 5,402,616. The main problem with the prior art flange connectors, such as those taught by these patents, is that the flange connectors do not accommodate tension, are very rigid and fail dynamically, meaning that there is little deformation in the steel prior to failure and therefore, the failure is difficult if not impossible to anticipate.
Additionally, because concrete cannot handle tension, the precast concrete members are formed with reinforced mesh in the flanged edges of the members. The reinforced mesh is embedded into the center of the concrete slabs and is typically positioned to extend substantially parallel to the planar surface of the slabs.
To best absorb and transmit the forces on the flange connector, the reinforced mesh should be positioned not only in the middle of the concrete slab, but also in alignment with the center of the central plate of the flange connector. Thus, the location of the flange connector relative to the reinforced mesh is quite critical. Typically, the pair of outstanding arms of a flange connector are secured to the mesh or used to support the mesh and also act to align the flange connector with the mesh.
For example, in the case of Klien, U.S. Pat. No. 5,402,616, the outstanding arms are both positioned underneath the reinforced mesh to support the reinforced mesh and hold it in position while the concrete is being cast. The problem with using both outstanding arms to support the underside of the reinforced mesh is that the flange connector is only able to adequately absorb the shear force exerted in the downward direction. Without any means for absorbing the force in the upward direction, the quick flexure that occurs from the rapid changes in loading on a deck, especially in a parking lot, causes failure on the underside of the concrete structure.
Additionally, none of the prior art flange connectors that have outstanding arms provide for the expansion of the central faceplate during welding. The arms typically extend directly outward from the central plate at an approximately forty-five degree (45°) angle. By having the arms extending directly outward from the central plate at forty-five degree (45°) angles, the angles function to compress the faceplate, thereby making it difficult for the faceplate to expand without cracking the surrounding concrete during welding. Finally, none of the prior art flange connectors have been suitable for withstanding seismic loading conditions and dynamic forces without dynamic failure.
SUMMARY OF THE INVENTION
Accordingly, the principal object of the present invention is to provide a flange connector that absorbs the shear force occurring in both the upward and downward direction and allow the flange connector to flex such that any failure in the connection is a ductile failure that can be detected through an inspection of the joint.
Yet another object of the present invention is to provide a flange connector that can withstand seismic loading conditions and dynamic forces without failure.
Still another object of the present invention is to allow the face or central plate of the flange connector to expand during welding and thereby avoid any cracking of the concrete.
To achieve these objectives, the flange connector
10
of the present invention is a onepiece steel member having a faceplate
18
, opposing faceplate returns
22
, flattening bends
24
, embedded legs
26
and reinforcing tabs
28
. The faceplate
18
is the central plate of the flange connector
10
that is welded to opposing faceplates
18
with a lug or rod. To allow the faceplate
18
to expand during welding, two opposing faceplate returns
22
extend away from the faceplate
18
at approximately ninety-degree (90°) angles. The ninety degree (90°) angles do not function to compress the faceplate
18
as do the more acute angles, and therefore, allow for the expansion of the faceplate
18
without causing fatigue to the concrete.
The embedded legs
26
are then formed from the faceplate returns
22
through flattening bends
24
that span between the embedded legs and the faceplate returns
22
such that the embedded legs
26
can be positioned in a plane substantially parallel to the horizontal surface of the concrete members
12
. One flattening bend
24
extends from the upper portion of the faceplate return
22
while the opposing flattening bend
24
extends from the lower portion of the faceplate return
22
. This is to allow the flange connector
10
to flex in both the upward and downward directions.
The length of the flattening bends
24
are such that one embedded leg
26
can be positioned above the reinforced mesh
30
and the other embedded leg
26
can be positioned below the reinforced mesh
30
. Thus, the mesh
30
is held between the embedded legs
26
. Again, this allows for the flange connector
10
to absorb the shear forces occurring in both the upward and downward direction. Finally, the embedded legs
26
are
Johnson Stephen R.
Magnesio Charles
Hammond Jennifer H.
JVI, Inc.
Kent Christopher T.
Sonneschein Nath & Rosenthal
Thissell Jennifer I.
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