Patent Application
20080000177
The present invention relates to floor and wall construction methods and systems using steel floor and wall framing members, and relates in particular to composite floor construction using steel joists supporting concrete-topped decking in conjunction with composite steel beams and wall construction systems using light-gauge steel stud framing members.
Load-Bearing Wall Construction
In conventional construction of multi-storey structures comprising load-bearing walls, platform framing technique is used. As the name suggests, platform framing relies on the floor assembly to provide a platform for subsequent framing construction. The lower floor supporting elements, usually the load-bearing walls, are constructed, then the floor elements installed, directly bearing on the supporting elements below. The follow-up bearing walls are then constructed, followed by the next upper floor assembly. The process repeats itself until the roof elements are installed. All modern floor systems involve the use of concrete as an integral part of the floor assembly. The fact that subsequent floor construction follows the completion of the floor assembly below means a significant delay in waiting for the concrete to cure.
Attempts have been made to eliminate or minimize delays in platform construction. U.S. Pat. No. 4,486,993 (Graham et al.), U.S. Pat. No. 5,881,516 (Luedtke), and U.S. Pat. No. 5,782,047 as well as U.S. Pat. No. 6,298,617 (de Quesada), deal in varying degrees with methods of constructing bearing walls whereby the upper wall assembly can proceed before completion of the floor elements
U.S. Pat. No. 4,486,993 (Graham et al.) employs hot rolled angles attached to a foam-core latticed bearing wall for floor assembly support.
U.S. Pat. No. 5,782,047 (de Quesada) employs hot-rolled ledge angles attached to light-gauge C-shaped channel steel stud bearing walls for bearing support of the concrete-topped floor assemblies. Floor concrete may terminate at the sides of the load-bearing walls, or may be carried continuously between the upper and lower wall assemblies. In the latter case (with concrete running between upper and lower assemblies), the upper wall assembly is supported on equally spaced screw-jack assemblies allowing the upper wall assembly to proceed before the floor concrete.
In U.S. Pat. No. 6,298,417 (de Quesada), a hat section is placed on top of the lower wall panel, with legs projecting horizontally out to support floor joists (instead of hot-rolled ledge angles as in U.S. Pat. No. 5,782,047). In place of screw-jack assemblies, discrete connectors are used. These connectors are shop-welded to the bottom of the upper wall panel, and site welded to the top of the bottom panel.
U.S. Pat. No. 5,881,516 (Luedtke) deals with load-bearing wall systems wherein the axial load does not pass through the floor assembly. Wall systems include both wood and conventional steel stud bearing walls. Floor assemblies include wood joists, light-gauge steel C-joists, and low-profile composite steel decks. The floor assemblies are supported, outside of the plane of the bearing wall, by various metal devices.
Underlying all of the above-referenced U.S. patent documents is the premise of carrying the floor load outside of the plane of the bearing wall. This very premise, however, creates eccentricity in the loading, and significantly reduces the load-carrying capacity of the bearing wall. Both Luedtke (U.S. Pat. No. 5,981,516) and de Quesada (U.S. Pat. No. 5,782,047 and U.S. Pat. No. 6,298,417) deal with shallow floor assemblies, i.e. low-profile floor decks (less than 76 mm in depth) and C-joists. The more common steel floor systems, using open-web steel joists (OWSJs) and medium/deep profile composite floor decks (greater than 76 mm in depth) are not discussed. With significantly increased spans associated with these more common systems, the eccentric bearing details become costly and complicated.
While continuity of the concrete in the floor assembly is maintained within the plane of the load bearing walls to maintain continuous inter-floor fire and acoustic separation across the bearing walls, neither Luedtke (U.S. Pat. No. 5,881,516) nor Graham (U.S. Pat. No. 5,782,047 and U.S. Pat. No. 6,298,417) makes structural use of the concrete. Hence, secondary structural elements are still required over window or door openings in the wall panels.
For the foregoing reasons, there is a need for metal stud load-bearing wall systems that:
In conventional post-and-beam construction with OWSJs, floor joists bear directly on the supporting beams, thus creating a space between the floor concrete and the supporting beams. This bearing detail is the only reason precluding the use of composite beam construction in the steel-joist-on-beam construction.
Rongoe (U.S. Pat. No. 4,741,138) addressed this problem by providing extensions from the beam, through the decking and into the concrete, in an assembly utilizing beams, standard joists bearing on top of the beams, and metal decking onto which concrete is poured. The extensions are located in between OWSJs. The shear headed studs are field welded to the extensions through holes cut in the steel deck.
The limitations of this composite beam include the minimal thickness of cover concrete available for composite action, the expense of the extension, and the amount of welding required for composite action.
For the foregoing reasons, there is a need for a composite beam construction system which provides an intermediate bearing element to support the joists and allows for the floor concrete to be in full contact with the steel beam along the full length of the beam, thus providing a deep concrete section—rather than merely a thin concrete deck—acting compositely with the steel beam.
Perimeter Stud Walls With Improved Impact Resistance
In post-and-beam construction, perimeter walls are often in-filled walls with metal studs. The in-fill walls are normally designed against wind loads only. In load-bearing metal stud wall construction, the perimeter walls are designed for gravity load as well as wind loads. In either case, perimeter stud walls are not designed for errant vehicles running into buildings. This invention will show an economical method of construction perimeter metal stud walls with improved resistance to impact from errant vehicles.
Composite Floor Construction With Concrete-Topped Deck on Open-Web Steel Joists
Concrete-topped steel deck on OWSJs constitutes the most common steel floor system. Many attempts have been made to further the efficiency of this system by integrating the OWSJs with the concrete on the steel deck for composite action.
U.S. Pat. No. 4,189,883 (McManus), and Canadian Patent Applications No. 2,404,535 (Moreau) and 2,441,737 (Moreau) disclose means of integrating the top chord of OWSJs and/or trusses with the concrete deck for improved horizontal shear resistance.
U.S. Pat. No. 5,544,464 (Dutil), U.S. Pat. No. 4,432,178 (Taft), U.S. Pat. No. 4,653,237 (Taft), CA Patent No. 1,186,910 (Gjelsvik et al.) and CA Patent No. 1,251,056 (Gjelsvik et al.) all describe composite open-web steel joist systems working in concert with concrete-topped steel decks for greater gravity-load-carrying capacity.
In Dutil's system, each joist has a top chord forming a shear connector protruding into the concrete deck. Forming part of the top chord are two angles acting as shelves to receive steel decking. The deck acts as a form for pouring the slab, and is a permanent part of the composite floor system. Dutil's system is commercially marketed under the name Hambro® joists by Canam.
Taft introduced a secondary truss-type framing member in which the top chord of the truss is formed in the shape of a modified “I” section having an upper flange, web and lower flange for supporting steel decking. The upper flange and web of the top chord are totally embedded in the concrete to cause the concrete floor and steel truss to function together structurally as a composite system.
Gjelsvik et al. describe OWSJs having tops chord comprising a pair of steel angles, and web members extending between the steel angles to the top of the vertical legs of the steel angles. Decking is supported by the horizontal legs of the top chords of adjacent joists, and a concrete slab is poured on the decking and between the vertical legs of the top chord to provide bonding between the concrete slab, top chord, and web.
All the above systems exhibit the following common features;
The use of shelves (usually in the form of angles) for deck support increases the cost of the composite open-web joist system in several ways:
Accordingly, there is a need for a composite steel-deck-and joist floor construction system that does not require deck-support shelves, and which enables continuous placement of steel deck
Composite Steel Stud Walls
Light-gauge steel stud walls have been used extensively in a number of ways:
In all cases, the steel stud walls are designed as hinged-supported at the top and bottom tracks.
In the construction of tall walls, attempts have been made to set light-gauge steel stud walls on top of concrete walls or masonry block walls, in the hope that the shorter steel stud length allows for lighter gauge steel to be used. However, the proper connections to the free-standing concrete wall or masonry wall require expensive details, in the absence of which a hinge joint forms at the junction of the lower concrete/masonry wall and the light-gauge steel stud wall, often leading to unsatisfactory performance or failure. Today, this practice has been all but abandoned.
A popular construction system with tall wall construction is the “tilt-up” construction method, in accordance with which reinforced concrete wall panels are cast flat on site, and then tilted up into vertical position to be connected to foundation elements. While this method may be advantageous a fast means of providing a building envelope, tilt-up walls typical provide poor insulation qualities an a limited choice of exterior wall finishes. Often an additional interior perimeter stud wall system is installed to provide the desired insulation and building envelope continuity.
For all the foregoing reasons, there is a need for a composite steel stud wall construction system in which at least one end of each stud has a significant degree of structural fixity (i.e., rotational resistance) rather than approximating a hinged connection as in prior art systems. Such a wall construction system would enable the use of lighter, more economical studs than would otherwise be required (in accordance with a “hinged end” stud design model), and would be particularly beneficial in practical applications including:
There is a further need for a composite stud wall building system that is adaptable to tilt-up construction, with advantages provided by conventional tilt-up construction in terms of speed of construction, but with improved insulation properties and adaptability for use with a wider variety of architectural finishes.
Stud Wall on Composite Deck Floor Construction
Fluted structural steel decks come in different depths, with the most commonly-used types having a 38 m (1.5″) depth. Medium-depth decks are 75 mm (3″) in depth, whereas decks with depths greater than 75 mm (3″) are usually referred to as deep profile decks, which may range from 200 mm to 300 mm (8″ to 12″) in depth. Steel deck may be plain (i.e., with all required structural strength being provided by the deck alone), or composite (i.e., with deformations formed into the deck to promote composite structural action with a concrete topping placed over the deck). Medium-depth and deep profile composite decks are often used to provide long spans between major supports (load-bearing walls or structural beams), without the need for intermediate joists.
In typical concrete-topped steel deck floor construction, deck installation and floor concrete placement must be completed before stud walls above the floor elevation may be constructed. This typically delays subsequent wall construction to allow for the curing of the floor concrete.
For the foregoing reasons, there is a need for an economical system way for constructing steel stud walls on top of fluted steel floor deck prior to placement of floor concrete.
In one aspect, the present invention is a composite joist-and-deck floor construction system featuring the use of “shear-connection-ready” open-web steel joists (hereinafter referred to as “SCR-OWSJs”), and in which shear connectors are fastened to the SCR-OWSJs after steel deck has been placed over the SCR-OWSJs. In a preferred embodiment of the system, each SCR-OWSJ is fashioned by attaching an elongate continuous steel cap plate to the top of the top chord of a conventional OWSJ (such as by welding, or other structurally effective fastening means). The field-installed shear connectors may be of any suitable type, spaced as required in accordance with well-known structural design principles. For example, the shear connectors may be conventional headed shear studs (e.g., Nelson studs) resistance welded or manually welded to the SCR-OWSJs through the steel deck, or shear connectors field-applied to the SCR-OWSJs through the steel deck using power-actuated or powder-actuated tools. Since the shear connectors are field installed after the floor deck is in place, the deck can be continuous over the SCR-OWSJs, rather than having to cut at each joist and supported on shelf angles.
Practical benefits available using the SCR-OWSJ floor construction system of the present invention include:
The SCR-OWSJ floor system of the present invention (the “SCR-OWSJ system”) may be used as a floor joist system by itself, or may be readily adapted for use with composite steel beam and load-bearing wall construction systems including but not limited to those described in Canadian Patent No. 2,407,253.
Preferably, the SCR-OWSJs incorporate joist seat extensions to facilitate direct bearings on support beams or walls, without need to interpose joist support elements between the joist seats and their support elements in order to achieve desired floor elevations. This facilitates the erection and positioning of SCR-OWSJs on the support beams or walls, since there are no obstructions (such as joist support elements or shear studs) present on the upper surfaces of these support elements when the SCR-OWSJs are being positioned. Shear connectors may be field-applied to both the SCR-OWSJs and supporting steel beams as required, using power-actuated or powder-actuated tools, after the SCR-OWSJs are in place. The advantages of this composite floor construction system include:
In another aspect, the present invention is a composite steel stud wall construction system in which the conventional bottom and/or top tracks are replaced with tracks with perforations in the web, or with pairs of bent plates or steel angles, to allow reinforcing dowels to project from a concrete support element (such as a concrete foundation wall). Infill concrete is placed within the stud assembly to a desired height above the bottom track (as determined by structural design requirements), such that the lower ends of the studs achieve a significant degree of structural fixity. The result is a composite steel stud wall which can be analysed as an upper segment comprising the portions of the steel studs above the infill concrete, plus a composite segment comprising the infill concrete and the portions of the steel studs embedded therein, with effective structural continuity between the two segments.
The scope of the composite steel walls can be broadened by incorporating the current tilt-up construction or precast methods in their installation. In the tilt-up version, the light gauge steel component of the wall panels are either fabricated in a shop or site fabricated on flat, complete with the exterior cladding and window framing details. The concrete components are site cast into the light gauge steel stud wall panels in locations required by structural design. The wall panels are then tilt-up or otherwise lifted into place after the concrete has acquired the strength necessary to handle the stresses from the lifting operation. In the present version, all of the wall panel components are shop fabricated and delivered to site for installation.
Practical benefits available using the composite steel stud wall construction system of the present invention include:
In a third aspect, the present invention is a wall construction system for use in conjunction with a concrete-slab-on-steel-deck floor system, that enables load-bearing steel stud walls to be framed between floor levels before floor concrete has been poured, while also imparting a significant degree of structural fixity. Practical benefits available from the use of this system include:
In a further aspect, the present invention is a shear-connection-ready open-web steel joist assembly comprising a steel truss having a top chord, a bottom chord, and a triangulated web system; and a steel plate overlying and connected to the top chord.
Embodiments of the invention will now be described with reference to the accompanying figures, in which numerical references denote like parts, and in which:
In the embodiment shown in
It is also to be understood that while cap plate 22 can most conveniently be provided in a single length, this is not essential to the invention. Cap plate 22 can be alternatively comprise two or more discontinuous lengths (i.e., not directly joined to each other) provided that any gaps between the discontinuous lengths are small enough not to impair proper support for any coincident lower flutes 6.1 of steel deck 6 (or provided that any such gaps occur below upper flutes 6.2 of deck 6). As well, each discontinuous length of cap plate 22 must be welded or otherwise connected to the top chord (5.1 or 18.1) with sufficient strength to safely transfer horizontal shear forces from all shear connectors 15 fastened to that discontinuous length, from the discontinuous length to the top chord. Of course, the same basic principle applies in the case of a single-length cap plate 22, and persons skilled in the art can readily design suitable weldments (or other forms of connection) in accordance with well-known structural engineering principles.
As shown in
Spandrel beam 60 also encases the lower ends of studs 42, thus imparting a significant degree of fixity thereto; this allows studs 42 to be lighter for given vertical and lateral loads than would be required for studs having no significant end fixity (i.e., hinge joints).
In the Figures, joist-support elements 3 are shown as pieces of rectangular steel tubing, oriented to allow free passage of concrete (and reinforcing bars 13, if required). However, persons skilled in the art will appreciate that joist-support elements 3 could take various other forms without departing from the basic concepts of the present invention.
In addition to the structural benefits achievable through use of the above-described system, it has a further advantage in that it allows LBWs to be constructed before the floor slab 7 poured, thus providing flexibility with respect to the timing of floor concrete placement operations, and facilitating earlier enclosure of the building (since additional wall construction does not have to wait for the floor slab to be placed and cured). In fact, the system makes it possible to defer floor concrete placement until the building is completely enclosed, thus allowing reducing hoarding and/or temporary heating costs for buildings being built in harsh climatic conditions.
Although Embodiment 3 has been illustrated and described in association with the use of SCR-OWSJs 20, it will be appreciated that the system can be readily adapted for use with conventional OWSJ or other types of floor joists (with or without shear connectors for composite action with floor slab 7). It will also be appreciated that the basic concepts described in connection with Embodiment 3 can be readily adapted for construction of upper LBW 40 on different types of lower LBW (e.g., masonry or wood framed walls) rather than on a steel stud wall 30 as illustrated.
Although Embodiment 4 has been illustrated and described in association with the use of SCR-OWSJs 20, it will be appreciated that the system can be readily adapted for use with conventional OWSJ or other types of floor joists (with or without shear connectors for composite action with floor slab 7). It will also be appreciated that the basic concepts described in conncetion with Embodiment 3 can be readily adapted for construction of upper LBW 40 on different types of lower LBW (e.g., masonry or wood-framed walls) rather than on a steel stud wall 30 as illustrated.
Embodiment 5 of the invention, illustrated in
Although Embodiment 5 has been described with specific reference to an exterior steel stud LBW 40, the exterior wall is not essential. The floor systems described herein work equally well in conjunction with alternative exterior wall systems that lie totally outside of the exterior base track 50 (e.g., curtain walls and precast wall panels).
Embodiment 6, as illustrated in
In conventional steel stud wall construction, the studs are designed as hinge-supported at both the top and the bottom track locations. While this approach has wide applications, situations arise where the walls are too high for economical steel stud use, or where the need for impact resistance rules out steel stud wall construction.
Examples of buildings requiring tall wall construction would include gymnasiums, auditoriums, and warehouses requiring high clearance. Masonry walls have traditionally been the wall assembly of choice for these building types.
Examples of building types requiring walls with high impact resistance would include manufacturing and fabrication shops with forklifts or mobile equipment, as well as buildings with high exposure to vehicle traffic. Concrete or masonry walls have traditionally been the wall assembly of choice for walls requiring high impact resistance.
Reinforcing steel dowels 82 projecting upward from support element 80 extend through dowel openings 75 in base track web 74 at locations and to heights as dictated by structural design criteria. Formwork 16 (either temporary or permanent) is positioned on each side of base track 72 and studs 42 and concrete is placed inside formwork 16 to a desired height above support element 80 (to suit structural design requirements), with web perforations 44 allowing concrete to flow between studs 42. This creates a composite steel stud wall 70 incorporating a reinforced concrete pony wall 84 projecting upward from support element 80. The lower portions of studs 42 are thus embedded within pony wall 84, and thus become substantially “fixed” from a structural analysis standpoint. Composite steel stud wall 70 can thus be structurally analyzed as comprising two segments—(1) an upper segment comprising the upper portions of steel studs 42, and (2) a composite segment comprising concrete pony wall 84 and the portions of studs 42 embedded therein, with no loss of structural continuity between the segments. If desired or require for structural reasons, horizontal reinforcing bars 13 can be inserted through web perforations 44 of studs 42 before placement of concrete for pony wall 84.
Embodiment 8 of the invention, as shown in
Embodiment 9 of the invention, as shown in
The bottom flange 94.1 if interior Z-closure plate 94 is welded or otherwise connected to supporting steel beam 14. The upper flange 94.2 of interior Z-closure plate is connected to the top of steel deck 6 (not shown in
The use of variant SCR-OWSJ 90 with interior Z-closure plates 94 and exterior closure angles 96 enables the system to be constructed using current structural steel erection practices, without overlap between related trades. The structural steel trade erects columns and beams, lifts the SCR-OWSJs in bundles and spreads them along the beams to their correct locations before welding them down to the beams. Then and only then need the light-gauge steel trade be on site for installation of decking, closure tracks and ties, perimeter wall studs and sheathing, and shear connectors to decks and beams.
The advantages of this new composite floor system with field-installed shear connectors to both beams and SCR-OWSJ's include:
The top tracks of panels 71 may be formed by a pair of steel angles 77 complete with anchorage studs. The angles 77 allow for support of the joists by direct welding. The depth of the concrete in-fill and reinforcing details are determined by structural design requirements. Dowels 82 may be installed as part of the precast composite panel for connection to the wall panels above.
Headers 79 over windows or other openings can be formed by box beams framed with light-gauge steel materials, or may be reinforced concrete headers forming integral parts of the precast concrete wall panels 71.
The bottom tracks of the wall panels may comprise interior and exterior closure plates 94 and 96 respectively) as in Embodiment 11. Floor concrete 7 flows into the closure plates to provide a solid inter-panel connection.
The precast composite stud wall system described above offers advantages over current practice including the following:
It will be readily appreciated by those skilled in the art that various modifications of the present invention may be devised without departing from the essential concept of the invention, and all such modifications are intended to be included in the scope of the claims appended hereto. It is to be especially understood that the invention is not intended to be limited to illustrated embodiments, and that the substitution of a variant of a claimed element of feature, without any substantial resultant change in the working of the invention, will not constitute a departure from the scope of the invention.
In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following that word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not excluded the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one such element. WHAT IS CLAIMED IS:
This application is a continuation-in-part, pursuant to 35 U.S.C. 120, of U.S. patent application Ser. No. 11/112,911, filed on Apr. 25,2005, and the specification of said earlier application is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11112911 | Apr 2005 | US |
| Child | 11772177 | Jun 2007 | US |
