Static structures (e.g. – buildings) – Assembled in situ-type anchor or tie – Sheet or wire tie
Reexamination Certificate
1998-09-14
2001-06-26
Kent, Christopher T. (Department: 3635)
Static structures (e.g., buildings)
Assembled in situ-type anchor or tie
Sheet or wire tie
C052S293300, C052S289000, C052S702000, C403S190000, C403S232100
Reexamination Certificate
active
06250041
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to building construction and more particularly to bracing brackets used to secure building members to one another during the erection of light duty metal frame buildings. The invention was devised primarily for use to brace metal wall frames to bases and has particular but not exclusive application to the bracing of light duty metal wall frames to concrete floors. However, it may also be applied to form prestressed joints between any two building members.
BACKGROUND TO THE INVENTION
Traditional light duty steel wall frames of the kind used in the walls of single storey houses, sheds and other relatively small buildings are generally made from structural members that are roll formed from light gauge sheet metal and comprise a plurality of spaced apart vertical studs, a horizontal top plate affixed to the upper end of the studs, a horizontal bottom plate affixed to the lower end of the studs and bracing straps or noggings affixed to and traversing the studs.
It has been proposed to secure together the base and well frame by a simple angle shaped steel metal bracket, having a horizontal flange fastened to the top face of the base anchored by bolts and a vertical flange fastened to the side of the end portion of the wall stud of the metal frame. Wall frames are designed to bear the weight of the roof truss and the roof covering on the basis that loads will be transferred to the load support members at or near the ends of the wall studs. Customarily, when conventional angle brackets are used to secure the wall studs to the base, undesirable reaction loads and torsional stresses are imposed on the end portions of the wall studs and/or the base anchor bolts at the position of the bracket. When extraneous forces are applied to the structure by means of for example, earthquake, the loads and stresses at these joints are even more pronounced.
In areas subject to earthquake and other extraneous load imposing natural phenomena, high capacity bracing panels have been proposed to resist such loads. These generally comprise a metal wall frame of the above kind clad with sheeting formed of, for example, metal such as for example steel, or wood such as for example plywood.
These bracing panels are generally anchored to concrete footings, floor slabs or other building components by affixture of the bottom plate thereto.
However under earthquake loads, it has been found that anchoring of this kind generally offers insufficient rigidity and strength to prevent damage to the wall and building structure.
A basic requirement of a bracing system to resist earthquake loads is for ultimate strength and resistance to deflection (stiffness). Steel wall frames can fairly easily be designed for strength but it has be proven difficult to design adequate stiffness into light gauge steel wall frames. This is because light gauge steel wall frame members readily exhibit small deflections around fasteners and across the members.
Earthquake forces generally come from horizontal shaking of the roof structure and enter the bracing panel horizontally through the top plate.
These horizontal forces at the top of the panel are resisted by vertical forces holding the bracing panel to the concrete slab or other parts of the structure.
Generally a bracing panel is held down by providing a fixing through the bottom plate, sometimes reinforcing the stud to plate connection with a strap, but all these systems ail the deflection criteria because of local bending between elements.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a bracket for connecting an end portion of a structural member to a building element, the bracket comprising:
an affixture portion adapted to be connected to the structural member;
an anchoring portion connected to the affixture portion and adapted to be anchored to the building element; and
spacer means being adapted to operatively cooperate with the anchoring portion and the building element so that a face of the anchoring portion is temporarily spaced a predetermined distance from the building element and thereafter movement of the spacer means relative to the anchoring portion and securing of the bracket to the building element effects tensioning of the structural member.
Generally the structural member is oriented upright and the building element provides a load bearing base. Preferably the load bearing base is rigid and the structural member is tensionable. In one embodiment the structural member is a metal stud constructed of a relatively light gauge material. In one example the metal stud is formed of a material having a wall thickness of less than about 1 mm.
It is preferred that the spacer means is integral with the anchoring portion to enable the spacer means to be moved from between the anchoring portion and the building element as a result of securing the anchoring portion to the building element.
Preferably the spacer means comprises crushable elements formed in the face of the anchoring portion, the crushable elements adapted to collapse and the face of the anchoring portion to contact the building element upon securing to the building element. Thus, a predetermined amount of tension is provided in the joint formed by the bracket.
It is also preferred that the bracket is formed of a single strip of sheet metal and wherein both the affixture portion and the anchoring portion present a substantially flat face to the structural member and the building element, respectively, the affixture and anchoring portions each defining planes intersecting at right angles, and the spacer means being in the form of a plurality of outwardly protruding teeth projecting from the face of the anchoring portion.
Preferably the affixture portion is at least three times the length of the anchoring portion. Preferably the affixture portion has a thickness of from between two to three times that of the wall thickness of the structural member. This provides a bracket with the affixture portion having the necessary resilience for tensioning of the structural member.
Preferably the anchoring portion is provided with one or more holes each designed to receive an anchoring fastener for securing of the bracket to the building element.
Preferably the affixture portion includes a series of apertures each designed to receive an affixture fastener for connection of the bracket to the structural member. More preferably the affixture portion is elongate and the apertures are arranged as two transversely spaced arrays of apertures. In particular the arrays are parallel and the apertures of each array are offset longitudinally so as to minimise any reduction in the cross-sectional area of the affixture portion of the bracket. Generally in each array the longitudinal spacing between adjacent apertures increases in a direction toward the anchoring portion of the bracket.
Preferably the aperture(s) nearest the anchoring portion are positioned from the junction of the anchoring and affixture portions a distance of at least two times the width of the affixture portion. This allows the bracket to flex under lateral movement of the structural member.
More preferably the anchoring portion is provided with a terminal end flange which extends substantially parallel to and in the same direction as the affixture portion.
It is preferred that the bracket further comprises a stiffening member located on an opposing face of the anchoring portion so as to distribute the force applied through the anchoring portion in securing the bracket to the building element. Generally the stiffening member has a lower profile shape substantially corresponding to an upper surface of the anchoring portion.
Preferably an inner radius of the bracket defined by the adjoining affixture and anchoring portions is shaped complementary to an abutting radius of the stiffening member, both of said radii being relatively large so as to reduce stress concentration when the bracket and structural member are tensioned. It is preferable for the stiffening member to be fixed to the
BHP Steel (JLA) Pty Ltd.
Kent Christopher T.
Kerins John C.
Miles & Stockbridge P.C.
Thissell Jennifer I.
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