Patent Grant
7562500
Not Applicable
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/minimize the delay in platform construction. U.S. Pat. No. 4,486,993 by Graham et al, No. 5,881,516 by Luedtke, and U.S. Pat. No. 5,782,047 as well as U.S. Pat. No. 6,298,617 by 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.
The first one, U.S. Pat. No. 4,486,993 by 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 by 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 refined his earlier invention and discarded the use of hot rolled ledge angles for floor support, and screw-assemblies as spacers to allow continuity of the concrete in the floor. In place of the hot-rolled ledge angles, a hat section is placed on top of the lower wall panel, with legs projecting horizontally out to support floor joists. 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 by 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. Nos. 5,782,047 and 6,298,417) deals 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 with OWSJ and medium/deep (in excess of 76 mm in depth) profile composite-floor-decks 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. Nos. 5,782,047 and 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.
This invention will present metal stud load-bearing wall systems that
Composite Beam Supporting Open Web Steel Joists
In post-and-beam construction with OWSJ's, 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 and Canadian Patent 1,230,495) solved this problem by providing extensions from the girder, through the decking and into the concrete, in an assembly utilizing girders, standard joists bearing on top of the girders, and metal decking onto which concrete is poured. The extensions are located in between open web steel joists. The shear headed studs are field welded to the extensions through holes cut in the steel deck.
The limitations of this composite girder are:
This invention 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. Instead of merely adding a thin concrete deck acting compositely with the steel beam, this invention provides a deep concrete section (T-section for interior beam and L-section for perimeter beam, respectively) to act integrally with the steel beam. This invention allows shop installation of headed studs to the beam for better quality control.
Shear-Connection-Ready Open Web Steel Joists
Concrete-topped steel deck on open web steel joists constitutes the most common steel floor system. Many attempts have been made to further the efficiency of the system by integrating the open web steel joists with the concrete on the steel deck for composite action.
McManus (U.S. Pat. No. 4,189,883), and Moreau (Canadian Patent Documents 2,441,737 and 2,404,535) reveal means of integrating the top chord of open web steel joists and/or trusses with the concrete deck for improved horizontal shear resistance.
Dutil (U.S. Pat. No. 5,544,464), Taft (U.S. Pat. Nos. 4,653,237 and 4,432,178, and Canadian Patent 1,208,030), and Gjelsvik et al (Canadian Patents 1,251,056 and 1,186,910) all present composite open web steel joist systems working in concert with concrete-topped steel decks for greater gravity load-carrying capacity. This invention is mainly concerned with the gravity load-carrying capacity of the composite open web steel joist system.
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 of 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 proposed open web steel joists with the top 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 chord of adjacent joists and a concrete slab 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 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:
This invention will show how the expensive shelves (usually in the form of angles) may be eliminated and the continuity of the steel deck maintained with field-installed discrete shear connectors onto a new type of shear-connection-ready OWSJ.
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 deigned 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 constructing perimeter metal stud walls with improved resistance to impact from errant vehicles.
For multi-storey buildings, this invention introduces three new types of light gauge steel load-bearing wall systems for supporting concrete topped floors, a composite steel beam system supporting concrete topped floors on OWSJ, a new type of Composite Open Web Steel Joists. In addition, this invention introduces a method of constructing vehicle-proof perimeter light gauge steel stud walls.
The LBW systems support the following floor assemblies: concrete-topped floor on Open-Web-Steel-Joists (OWSJ), concrete-topped floor on channel-type light gauge joists with perforated webs, and concrete-filled deep-profile composite floor deck, respectively. Light gauge steel studs in this invention have at least one hole at the bottom at specified locations, and may have perforations along the length of the studs.
Specialized bottom tracks and/or concrete enclosure panels are at the heart of the new LBW systems of this Invention. For LBW systems supporting channel-type light gauge joists with perforated webs, as well as mid- and deep-profile steel decks, the bottom tracks are complete with perforations in the web, and work with enclosure panels as forming for an in-wall concrete beam. For LBW supporting OWSJ, the specialized bottom track is complete with flange cutouts and discrete load-bearing blocks for OWSJ support, and works as forming for an in-wall concrete beam.
The new composite steel beam system incorporates, on the top flange of the beam, a specialized perforated track complete with cutouts and discrete load-bearing blocks for OWSJ support, and evenly spaced holes in the track for the passage of shear connectors shop or site welded to the beam.
The new Composite Open Web Steel Joist system employs a steel cap plate fitted on top of the top chord of conventional open web steel joists and shear connectors are field installed after steel deck is in place. The field-installed shear connectors may be conventional headed shear studs, or shear connectors connected with power-actuated tools. As the shear connectors are field installed after the decking is in place, this new Composite Open Web Steel Joist system maintains the continuity of the steel deck over the joists. The new Composite Open Web Steel Joist system may be used together with the Composite Steel Beam and LBW systems in this Invention, or may be used with conventional beam or LBW supports.
In load-bearing-wall construction, the objectives of the invention are:
With steel beams supporting concrete-topped floor on OWSJ, the objectives of the invention are:
With the new Shear-Connection-Ready Open Web Steel Joists, the objectives of the invention are:
With the new impact-resistant Perimeter Stud Wall System, the objective of the invention is to provide an economical in-wall concrete wheel-stop along the perimeter of the building to provide improved resistance to vehicular impacts.
While the subsequent descriptions of this invention are necessarily given in connection with specific apparatus and embodiments, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of the invention. Specifically, concrete stops and closures, other than those described below and in the Drawing, can be easily developed for other types of joist floor systems.
Load-Bearing Wall (LBW) Systems
The first level of a load-bearing wall structure is the conventional load-bearing wall, with light gauge steel studs placed between top and bottom tracks.
Each wall panel above the lowest level, illustrated in
Embodiment 1 is modified for application in an interior load-bearing wall supporting OWSJ's from both sides. The modification is achieved by having cutouts in both vertical legs of the bottom track (9), and having both vertical legs the same height.
The first level of a load-bearing wall structure is the conventional load-bearing wall, with light gauge steel studs placed between top and bottom tracks.
Each wall panel above the lowest level, illustrated in
The first level of a load-bearing wall structure is the conventional load-bearing wall, with light gauge steel studs placed between top and bottom tracks.
Each wall panel above the lowest level, illustrated in
The first level of a load-bearing wall structure is the conventional load-bearing wall, with light gauge steel studs placed between top and bottom tracks.
Each wall panel above the lowest level, illustrated in
The composite steel beam comprises equally spaced shear connectors (19) shop welded to the top flange of a structural beam (18), normally a wide flange beam. The beam section, and shear connector design are governed by specific project requirements: beam span, OWSJ span, and floor loading. Exterior wall panels, complete with opening framing for windows, are installed on top of the composite beam before concrete pour. Each wall panel comprises:
Embodiment 6 is modified for application in an interior composite beam supporting OWSJ's from both sides. The modification is achieved by having cutouts in both vertical legs of the bottom track (9), and having both vertical legs the same height. The final result is Embodiment 7, and comprises:
The impact-resistant perimeter stud wall is an economical perimeter wall system that protects the building and its occupants from errant vehicles running into the building, comprising:
Perimeter stud walls using web-perforated studs and perforated track are installed on top of the foundation element (21). Plywood or OSB boards (20) are applied on both sides of the stud wall to a height as per project requirement. Horizontal reinforcing bars (13) are installed through the perforated studs, and dowels (13) from the foundation through the perforated bottom track. Concrete is poured to the height of the formwork, producing an in-wall wheel stop.
This new shear-connection-ready open web steel joists comprises:
Conventional open web steel joists are shop-fitted with a cap plate. Steel deck is installed continuously over OWSJ supports. Shear stud connectors are then connected through the steel deck to the cap plate either by welding or with power-actuated connectors.
Alternately, in lieu of a steel cap plate fitted to a regular OWSJ, the top chord may be replaced with a flat-topped element, such as a T-section or a tube section as shown in
For economy and adequate concrete surrounding the shear-connectors, medium profiled and wide-fluted steel decks are recommended to increase joist spacing. Typical applications will have 75 mm deep wide-fluted composite decks spanning 2400 mm or more between the shear-connection-ready OWSJ. The increased joist spacing allows the design to reduce the steel beam capacity requirement by locating the joists away from mid-span and closer to the end supports of the beam.
Fabrication/Construction Procedures
We describe below, by way of examples with a Load-bearing Wall System and a Composite Beam/OWSJ system, ways the invention may be used in the construction of a multi-storey structure.
LBW—OWSJ System
The wall construction is done, either on site or in a shop, in the following sequence:
The upper wall panels are assembled similarly, except for the following modifications:
The complete site construction may proceed as follows:
The steps (b), (c), (d), (e) and (f) are repeated until the roof deck is installed. Concrete topping may be scheduled after the entire building enclosed as one continuous pour. Alternatively, concrete for each floor may be scheduled immediately after the floor deck above is installed.
Composite Beam—OWSJ System
Site construction procedure can be summarized as follows:
Comparison with Prior Art
Load Bearing Wall Systems
Since both Luedtke and de Quesada have patents for load-bearing wall systems which allow upper floor walls to proceed before pouring floor concrete, it is imperative to distinct the load-bearing wall systems in this invention (Embodiments 1 to 5) from their systems protected under their respective US patents. The following section will examine only the parts of their claims relevant to the present application—light gauge steel stud load-bearing walls and the floor assemblies they support.
Specifically, Luedtke in U.S. Pat. No. 5,881,516, “discloses building comprising a plurality of wall members comprising a plurality of metal wall members having track elements secured thereto, a plurality of bearing members having bearing surfaces projecting therefrom, and means connecting the bearing members to the track members. A multi-layer floor extends between the walls, the floor comprising a first layer having a first surface resting on the bearing surfaces such that wall axial loads do not pass through the floor construction.”
The key to Luedtke invention is that metal devices projecting outside the plane of the load-bearing wall support the floor assemblies. This very premise, however, creates eccentricity in the loading, and significantly reduces the load carrying capacity of the bearing wall. In contrast, the load-bearing wall systems in this application support floor assemblies either through a continuous reinforced concrete beam inside the wall assembly (as in the case of floors with OWSJ's or web-perforated C-joists), or through direct bearing of the floor on the load-bearing wall below (as in the case with deep-profile composite decks), with little or no eccentricity.
Though not at all clear from this Claims statement, a careful examination of U.S. Pat. No. 5,881,516 will show that the patent covers load-bearing walls supporting shallow floor assemblies only, i.e. shallow to medium depth (up to 75 mm) metal deck without joist support, and metal decks on C-shaped channel joists. Refer to
Another distinction between this application and Luedtke's invention lies in the use of concrete inside the load-bearing wall space. Luedtke uses conventional C-studs with solid webs. Concrete is compartmentalized in between studs, and there is no possibility of putting longitudinal reinforcing bars running the length of the load-bearing wall. Consequently, concrete in the Luedtke system serves only to improve sound and floor ratings. Structurally, it adds dead load to the wall, and consequently, increases loading to the lintels over window and door openings in the wall below. In contrast, the studs in this application will have perforations at the bottom (and, optionally, along the length of the stud), allowing reinforcing bars to go through. Hence, in the load-bearing walls supporting OWSJ or web-perforated C-joists, a reinforced concrete beam can be properly designed to carry the floor load over any window or door openings, in addition to providing the improved sound and fire rating of the wall assembly. This reinforced beam eliminates the need for secondary lintels, which would still be required in Luedtke's system.
“de Quesada discloses a prefabricated system using wall panels having a combination of cold rolled light gauge sheet metal and hot rolled tubular steel. Panels are stacked one on top of each other to form vertical wall assemblies and may be welded directly with their top and bottom members or include intermediate shear connectors. Shear resistance or resistance to lateral forces is provided by a single continuous metal sheet either flat or corrugated (a deck type sheet) fastened to the steel studs or alternatively diagonal or V-shaped bracing. Connectors between the wall panels provide a gap for a continuous concrete floor.”
Careful examination of U.S. Pat. Nos. 6,298,617 and 5,782,047 shows that metal devices projecting outside the plane of the load-bearing wall support the floor assemblies, and only ‘metal deck on C-shaped channel joists’ floor assemblies are supported. Refer to FIG. 13 and FIG. 32 in U.S. Pat. No. 6,298,617 and FIGS. 8, 9, 11 in U.S. Pat. No. 5,782,047.
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, there is not enough depth of concrete for any structural use. (Refer to FIG. 13 and FIG. 32 in U.S. Pat. No. 6,298,617 and FIGS. 8, 9, 11 in U.S. Pat. No. 5,782,047.)
All the arguments that differentiate this application from Luedtke's invention apply, without modification, to de Quesada's inventions as well.
To sum up, both Luedtke and de Quesada incorporate metal devices projecting beyond the plane of load-bearing walls to carry the floor assemblies, with resulting eccentricity in loading for the load-bearing walls. Both deal with shallow floor assemblies. Luedtke deals with metal deck up to 75 mm without joist support and ‘metal deck on C-shaped channel joists’ floor assemblies, while de Quesada only incorporates ‘metal deck on C-shaped channel joists’ floor assemblies. This application uses a continuous reinforced concrete beam inside the wall assembly to carry the floor loads, with little to zero eccentricity in loading. Whereas both Luedtke and de Quesada limit their floor assemblies to shallow floor assemblies, this application extends the scope of application to deep floor assemblies with concrete topped steel deck on OWSJ and concrete on deep profile composite floor decks.
Composite Beam Systems
Rongoe (U.S. Pat. No. 4,741,138 and Canadian Patent 1,230,495) presented the first patented composite steel beam system supporting OWSJ floors. He achieved this by “providing extensions from the girder, through the decking and into the concrete, in an assembly utilizing girders, standard joists bearing on top of the girders, and metal decking onto which concrete is poured. The extensions are located in between open web steel joists.” The shear headed studs are field welded to the extensions through holes cut in the steel deck.
This method of construction involves field-cutting of holes in the steel deck, and field welding of shear stud connectors to the girder extension. In normal “concrete-topped steel deck on OWSJ” floor construction, the cover concrete thickness (the concrete above the top of the steel deck) is only about 65 mm (2.5 inches), severely limiting the effectiveness of the shear stud connectors. Consequently, a large number of shear connectors on long girder extensions are required for effective composite action, reducing the cost efficiency of the system.
In this invention, an elevated shoe is provided for the joist seats through the use of a load-bearing block, and shear stud connectors can be shop-welded to the steel beam for better quality control. No field cutting is required. The shear stud connectors are fully embedded in concrete for its maximum effectiveness. The steel beam is effectively integrated with a deep concrete beam (a T-section for interior beam, and L-section for an exterior beam) instead of a 65 mm concrete cover thickness.
Impact-Resistant Perimeter Stud Wall System
There appears to be no prior art involving perimeter stud wall system that incorporates an in-wall wheel stop.
Shear-Connection-Ready Open Web Steel Joist System
In patented prior art involving composite open web steel joists for gravity loading, all inventors have used steel shelves outside the vertical plane of the web to carry steel decks between joists. Composite action is achieved by embedding the top chord member(s) in the concrete cover slab. Various prior patents differ in the shape and/or embossment of the top chord to achieve composite action.
As steel deck is cut to fit between composite OWSJ, continuity of the steel deck is not maintained. Two connections per flute per joist location are required whereas only one connection per flute is required for deck on non-composite OWSJ.
In contrast, this invention claims a shear-connection-ready OWSJ, instead of a composite OWSJ. By fitting a cap plate to a conventional open web steel joist, steel deck may be installed continuously over joist supports and with only one connection per flute per joist location. Composite action is then achieved through field-welded shear stud connectors or power-actuated shear connectors.
As the cap plate can be fitted to any kind of top chord, this method is easily adaptable to any kind of OWSJ, and does not require major change in joist manufacturer's equipment or shop practice. The cap plate also ensures that the field-installed shear connectors can be installed centrally in the plane of the web of the joist.
Alternately, in lieu of a steel cap plate fitted to a regular OWSJ, the top chord may be replaced with a flat-topped element, such as a T-section or a tube section as shown in
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