Implementations described herein generally relate to lateral load resisting systems and assemblies, and more specifically to a lateral load resisting system intended for a cold-formed steel building structure and/or construction.
Cold formed steel (CFS) construction is one of the most economical, noncombustible types of construction available for building structures. However, its use is primarily limited to midrise structures thus limiting its extension to buildings of greater height. This is primarily because of the limited lateral load capacity of traditional systems that are compatible with CFS construction. Such traditional systems include shear walls with fiberboard, gypsum board, steel sheets, and oriented strand board (OSB) panels, as well as braced frames with tension only CFS straps also known as strapped walls.
Hence, there is a need for lateral load resisting systems with higher capacities and which are compatible with CFS construction.
The present disclosure features a high-capacity hybrid frame-wall system intended for cold formed steel (CFS) construction. The hybrid frame-wall may be used as a replacement or as an alternative to the traditionally strapped wall system. For example, the hybrid frame-wall system may be used as a replacement of the strapped wall system in cases where the lateral load demand is high and cannot be sustained by the straps. The hybrid frame-wall system may also be used as an alternative to the strapped wall system in midrise construction when the stakeholders wish to reduce the total number of shear walls by using fewer higher capacity lateral load resting systems such as the present disclosure.
In the disclosed hybrid frame-wall system, lateral load capacity may be enhanced by introducing tension only bracing elements that comprise prestressing strands in addition to cold-formed steel straps. The prestressing strands can be installed within the plane of the wall and connect eccentrically to vertical chords. The strands are not prestressed. Therefore, the prestressing strands may be used as passive additional high-capacity bracing elements considering that the steel material used for the strands offers yield and ultimate stresses that are several times higher than that of the cold-formed steel material used for the straps. The prestressing strands can be used in single, double, or triple diagonal configurations, for example, to further enhance capacity. The vertical chords are made with hollow structural steel (HSS) to be able to withstand the shear and bending moment created by the eccentric connection in addition to axial forces generated by gravity and overturning moments. Further, unique hole patterns may be introduced in the CFS columns and HSS chords to install the strands. A steel prism may be welded at the top and bottom of the chords to provide anchorage for the prestressing strands.
According to a first aspect, there is disclosed a hybrid frame-wall system that includes a plurality of vertical load bearing supports; at least one pair of chords; a lateral load resisting assembly including at least one pair of diagonal tension only bracing elements and at least one pair of diagonal reinforcement bracing elements; at least one top track positioned along the top end of the plurality of primary vertical load bearing supports, and at least one bottom track positioned along the bottom end of the plurality of primary vertical load bearing supports.
In some exemplary implementations, at least one pair of diagonal reinforcement bracing elements are installed within the plane of the frame-wall assembly.
In some exemplary implementations the system includes two pairs of diagonal reinforcement bracing elements, which are installed within the plane of the frame-wall assembly.
In some exemplary implementations the system includes three pairs of diagonal reinforcement bracing elements, which are installed within the plane of the frame-wall assembly.
In some exemplary implementations, at least one pair of diagonal reinforcement brace elements are prestressing strand braces.
In some exemplary implementations, at least one pair of diagonal tension only bracing elements are cold formed steel straps.
In some exemplary implementations, at least one pair of chords are hollow structural steel (HSS) elements.
In some exemplary implementations each diagonal reinforcement bracing element is connected eccentrically to a corresponding chord.
In some exemplary implementations each diagonal tension only bracing element is connected concentrically to a corresponding chord.
According to another aspect, there is disclosed a hybrid frame-wall system for increasing lateral force resistance in a structure including a wall assembly and a lateral force resisting assembly (the frame), which is integrated with the wall assembly. The wall assembly is formed by a plurality of primary vertical load bearing supports, a top track and a bottom track. The lateral force resisting assembly (the frame) is configured to increase the lateral load resistance of the building structure and includes one pair of chords, one or more pairs of prestressing strand bracing elements and at least one pair of cold formed steel tension only bracing elements.
According to yet another aspect, there is disclosed a method of constructing a hybrid frame-wall system for a structure. The method includes positioning a plurality of primary vertical load bearing supports between a top track and a bottom track, installing at least one pair of chords at the side ends of a frame-wall assembly, connecting at least one pair of tension only bracing elements diagonally between the chords, and connecting at least one pair of diagonal reinforcement bracing elements diagonally in between the chords.
In some exemplary implementations, the method further includes increasing the lateral load resistance capacity of the system by connecting a plurality of pairs of diagonal reinforcement bracing elements diagonally in between the chords.
In some exemplary implementations, at least one pair of diagonal reinforcement bracing elements are prestressing strands.
In some exemplary implementations the chords are hollow structural steel (HSS) elements.
While the claims are not limited to a specific illustration, an appreciation of various aspects may be gained through a discussion of various examples. The drawings are not necessarily to scale, and certain features may be exaggerated or hidden to better illustrate and explain an innovative aspect of an example. Further, the exemplary illustrations described herein are not exhaustive or otherwise limiting, and embodiments are not restricted to the precise form and configuration shown in the drawings or disclosed in the following detailed description. The various advantages of the implementations of the present disclosure will become apparent to one skilled in the art by reading the following specification and appended claims, and by referencing the following drawing(s), in which:
The disclosure will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary implementations of the disclosure are shown. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the exemplary implementations set forth herein. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made to various implementations without departing from the spirit and scope of the present disclosure. Thus, the breadth and scope of the present disclosure should not be limited by any of the above-described exemplary implementations but should be defined only in accordance with the following claims and their equivalents.
The present disclosure relates to a high-capacity hybrid frame-wall system intended for cold formed steel (CFS) construction. The high-capacity hybrid frame-wall includes a lateral load resisting assembly (LLRA) that provides high lateral load resistance to natural hazards such as windstorms, hurricanes, and earthquakes. The provided lateral load capacity is notably higher than that offered by traditional cold-formed steel systems and is achieved in part due to the system's inclusion of eccentrically connected diagonal tension only bracing elements within the plane of a strapped cold-formed steel wall. These additional bracing elements feature prestressing strands and increase the lateral load resistance of the hybrid frame-wall system considerably by working together with the CFS straps.
The high lateral load resistance is also achieved in part due to the hybrid integration of various materials within the system's construction. This includes incorporating cold-formed steel elements (e.g., CFS studs), hot-rolled steel elements (e.g., hollow structures steel chords), and high-carbon steel elements (e.g., prestressing strands). Each material possesses unique and distinct mechanical properties, the combination of which significantly enhances the overall strength and load-bearing capacity of the hybrid frame-wall system. Further, the integration of the various materials provides a more cost-effective solution that relying on traditional materials like structural steel and reinforced concrete.
The hybrid frame-wall system may be used either as a replacement or as an alternative to a strapped wall system. It can be used as a replacement of the strapped wall system in cases when the lateral load demand is high and cannot be sustained by the straps. The system can also be used as an alternative to the strapped wall system in midrise construction when the stakeholders wish to reduce the total number of shear walls by using fewer higher capacity lateral load resting systems such as the presently disclosed system. The disclosed system enables cold-formed steel structures to reach building heights typically dominated by structural steel and reinforced concrete, thereby facilitating the creation of resilient structures that are economical, easy to construct, and resistant to natural hazards.
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The wall assembly includes a top track 1 (e.g., a top CFS track), a plurality of primary vertical load bearing supports 2 (e.g., cold formed steel studs), at least one pair of chords 3 (e.g., HSS chords) and a bottom track 8 (e.g., a bottom CFS track). The lateral load resisting assembly includes at least one pair of chords (e.g. HSS chords) 3, at least one pair of diagonal reinforcement bracing elements or braces 4 (e.g., prestressing strand braces) and at least one pair of diagonal tension only bracing elements or braces 6 (e.g., CFS straps). The plurality of connection elements or connectors includes a plurality of connection plates 7 (e.g., gusset plates), with eight connection plates 7 show pursuant to the illustrated example, and a reinforcement bracing element connection assembly formed by several connection sleeves 5 (e.g., HSS sleeve(s)), several prisms 9 (e.g., steel prism), and at several chuck and barrel assemblies 10 to anchor the strands.
The top track a runs horizontally along the top of the wall assembly and may be constructed from cold formed steel (CFS). The bottom track 8 runs horizontally along the bottom of the wall assembly and may be constructed from CFS. The plurality of primary vertical load bearing supports 2 are configured to carry vertical loads from a structure above and transfer them to the bottom track. Each primary vertical load bearing support 2 is vertically oriented and connected to both the top 1 and bottom tracks 8. In some implementations, the primary vertical load bearing supports 2 are evenly spaced apart and may be welded to the edges of the top 1 and bottom 8 tracks. Further, in some implementations, the plurality of primary vertical load bearing supports 2 may be configured with CFS studs.
The pair of chords 3 are configured to provide vertical support at the ends of the hybrid frame-wall and to provide anchorage points for the pair of diagonal reinforcement bracing elements 4 and the pair of diagonal tension only bracing elements 6. Each chord 3 is vertically oriented and connected to both the top 1 and bottom 8 tracks at each side end of the frame-wall assembly respectively. Further, the pair of chords 3 may be configured with hot-rolled steel elements, such as, for example, hollow structural steel (HSS) chords.
The pair of diagonal reinforcement bracing elements 4 may be configured with high-carbon steel elements, such as, for example, prestressing strands. In some implementations, the prestressing strands may be seven wire prestressing strands. Prestressing strand braces 4 have self-centering capabilities when loaded within their linear elastic range, which is essential in limiting permanent deformations during a natural hazard. Additionally, prestressing strands 4 can be nominally posttensioned on-site to eliminate any looseness that will result due to the application of the gravitational loads during construction as each structural element assumes its final position.
The prestressing strands 4 can be configured in several ways, such as, for example, straight, bent at the ends, and other configurations. In
The lateral load resisting assembly may be configured with at least one pair of diagonal tension only bracing elements 6 with either a single, double or triple layer of diagonal reinforcement bracing elements 4. Each layer of diagonal reinforcement bracing elements 4 are positioned in the frame-wall assembly in a parallel fashion relative to one another. Further, each additional layer of diagonal reinforcement bracing elements provides additional resistance to lateral forces, which allows the system 25 to support higher lateral loads. Although, the disclosure describes single, double, and triple layer configurations, it should be noted that additional layers may be added as needed.
A single layer configuration may be implemented with one pair of diagonal reinforcement bracing elements 4 where each diagonal reinforcement bracing element 4 may be installed diagonally to the frame-wall assembly, with each end connected to one of the chords 3, forming an X configuration, as shown in
A double layer configuration may be implemented with two pairs of diagonal reinforcement bracing elements (4a, 4b) where each diagonal reinforcement bracing element in each pair may be connected to a corresponding chord 3, forming a double X configuration, as shown in
A triple layer configuration may be implemented with three pairs of diagonal reinforcement bracing elements (4a, 4b, 4c) where each diagonal reinforcement bracing element in each pair may be connected to a corresponding chord 3, forming a triple X configuration, as shown in
When the chords 3 are made with hollow structural steel, the chords 3 are able to better withstand the shear and bending movement created by the eccentric connections with each diagonal reinforcement bracing element 4 in addition to axial forces generated by gravity and overturning moments.
The connection of each diagonal reinforcement bracing elements 4 to a corresponding chord 3 is provided by way of one or more connection sleeves 5, one or more prisms 9 and one or more chuck and barrel assembly 10. In some implementations, the one or more connection sleeves may each be configured with a HSS sleeve. In some implementations, the one or more prisms may each be configured with a steel prism. In some implementations, the one or more chuck and barrel assemblies 10 may each be configured with a prestressing chuck and barrel assembly to anchor the prestressing strands.
Further, in some implementations, the one or more steel prisms 9 may be welded at the top and bottom of each chord 3 to provide anchorage for the attachment of one or more diagonal reinforcement bracing elements 4 in conjunction with the prestressing strand chuck and barrel assembly 10.
The HSS sleeves 5 may be welded to the sides of the HSS chords 3, and the steel prism 9 provides support for the chuck barrel assembly. The prestressing chuck and barrel assembly 10 then secures the prestressing strands in place, providing the necessary tension to the strands. The HSS sleeve 5 transfers uplift and shear forces to the anchor rods, the steel prism 9 distributes the strand force evenly, and the chuck and barrel assembly 10 maintains the tension in the prestressing strands 4. Together, these components enhance the lateral load capacity and resistance to lateral forces in the system 25.
The steel prism may be implemented in different shapes, such as, for example, the steel prism 9, shown in
The design and dimensions of a HSS guide 14 can be adjusted to accommodate the bend radius of the prestressing strand 4 connected to it. So, for example, a bend radius 11 of the prestressing strand 4 at the connection in
The internal diameter, length, configuration, material thickness, and overall geometry of the HSS guide are key factors that influence the bend radius of the prestressing strands. To achieve a larger bend radius, the sleeve should be designed with a similar larger bend radius. Conversely, smaller bend radii in the HSS sleeve 14 will lead to smaller bend radii in the strand, increasing the risk of damaging the prestressing strands.
Further, each diagonal reinforcement bracing element 4 may pass through all (primary) vertical load bearing supports 2 and chords 3. Each vertical load bearing support 2 and chord 3 may include perforations or apertures, having a unique hole pattern, which are fabricated specifically to accommodate one or more diagonal reinforcement bracing elements 4, respectively. The diagonal reinforcement bracing elements 4 may pass through the primary vertical load bearing supports and chords, where perforations are integrated into each respectively.
The at least one pair of diagonal tension only bracing elements 6 are configured to act as braces that resist lateral forces such as wind and seismic loads. The pair of diagonal tension only bracing elements 6 may be configured with cold formed steel (CFS). Each diagonal tension only bracing element may be installed diagonally to the frame-wall assembly, with each end connected to one of the chords 3, and to the top 1 and bottom 8 tracks, forming an X configuration, as shown in
In some implementations, each diagonal tension only bracing element 6 may be connected to a corresponding chord 3, and to the top 1 and bottom 8 tracks by way of connection plates 7 (e.g., gusset plates). In some implementations, each diagonal tension only bracing element 6 may be welded to the connection plates and the connection plates may be welded to corresponding chords 3 and to the top 1 and bottom 8 tracks.
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The method may include increasing the lateral load resistance capacity of the system 25 by connecting a plurality of pairs of diagonal reinforcement bracing elements 4 diagonally in between the chords 3, wherein the at least one pair of diagonal reinforcement bracing elements are prestressing strands and the at least one pair of chords are hollow structural steel (HSS) elements.
The disclosed lateral load resisting assembly, when integrated with the frame-wall assembly, offers 12.8%-55.6% and 44.3%-190% increases in in-plane stiffness and lateral load capacity, respectively, compared to a traditional strapped wall system, while offering comparable system ductility. Moreover, energy dissipation is accomplished by allowing the lateral load resisting assembly to act as inelastic fuse elements while the rest of the hybrid frame-wall system remains essentially clastic, or experiences limited inelastic straining.
From the above, an exemplary wall panel of the disclosure includes CFS top 1 and bottom 8 tracks that connect to the CFS studs 2 and HSS chords 3. The CFS studs 2 support gravitational loads, and the HSS chords 3 serve as vertical chord members to enhance the capacity of the system 25 against the effects of overturning moments in addition to supporting gravitational loads. Cold-formed steel straps 6 concentrically connect to the HSS chords 3 via gusset plates 7, and prestressing steel strands 4 eccentrically connect to the HSS chords 3 via a steel prism 9 and prestressing strand chuck and barrel assembly 10, and hold-down connections that facilitate uplift and shear load transfer using HSS sleeves 5 and anchor rods 19. Steel prisms 9 are used to provide anchorage for the prestressing strands 4. The steel prisms 9 may be welded to the HSS sleeves 5 that receive the hold down anchors 19. The HSS sleeves 5 may in turn be welded to the HSS chords 3 to facilitate load transfer. The system 25 may employ a single, double, or triple layer configuration of diagonal strands in each direction.
The exemplary wall panel may be used to support composite concrete floor systems that feature a cold formed steel deck and cast-in-place concrete.
The disclosed system 25 provides lateral load resistance through three different mechanisms: 1) shear resistance provided by moment frame action through HSS chord-concrete slab interaction, 2) shear resistance provided by the concentrically connected CFS straps, and 3) shear resistance provided by the eccentrically connected prestressing strands.
The prestressing strand braces 4 have self-centering capabilities when loaded within their linear elastic range, which helps facilitate limiting permanent deformations during a natural hazard. The braces 4 can be arranged in single, double, or triple layer configurations to further enhance capacity. The prestressing strand braces 4 may be nominally posttensioned on-site to eliminate any looseness that may result due to the application of the gravitational loads during construction as each structural element assumes its final position (i.e., settles in place). One end of the straps 6 can be left unattached to the gusset plate 7 and can be connected to the gusset plate 7 after the completion of structural framing while prestressing strand braces 4 provide stability during construction, addressing the gravity load induced buckling of the straps 6 during construction. Energy dissipation is accomplished by allowing the straps 6 and strands 4 to act as inelastic fuse elements while the rest of the lateral load resisting system (LLRS) remains essentially elastic or experiences limited inelastic straining.
All components of the hybrid system 25 fit within the dimensions of a typical load bearing wall allowing the CFS studs 2 to resist the gravitation loads while using higher capacity materials and configurations to resist lateral loads without requiring additional architectural space. The disclosed hybrid frame-wall concept lends itself to prefabricated panelized construction without the need for onsite skilled labor, providing advantages with respect to speed of construction and lower cost of a given structural system.
Various examples/implementations are described herein for various apparatuses, systems, and/or methods. Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the examples/implementations as described in the specification and illustrated in the accompanying drawings. It will be understood by those skilled in the art, however, that the examples/implementations may be practiced without such specific details. In other instances, well-known operations, components, and elements have not been described in detail so as not to obscure the examples/implementations described in the specification. Those of ordinary skill in the art will understand that the examples/implementations described and illustrated herein are non-limiting examples, and thus it can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the implementations.
Reference throughout the specification to “examples, “in examples,” “with examples,” “various implementations,” “with implementations,” “in implementations,” or “an implementation,” or the like, means that a particular feature, structure, or characteristic described in connection with the example/implementation is included in at least one implementation. Thus, appearances of the phrases “examples, “in examples,” “with examples,” “in various implementations,” “with implementations,” “in implementations,” or “an implementation.” or the like, in places throughout the specification are not necessarily all referring to the same implementation. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more examples/implementations. Thus, the particular features, structures, or characteristics illustrated or described in connection with one implementation/example may be combined, in whole or in part, with the features, structures, functions, and/or characteristics of one or more other implementations/examples without limitation given that such combination is not illogical or non-functional. Moreover, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the scope thereof.
It should be understood that references to a single element are not necessarily so limited and may include one or more of such elements. Any directional references (e.g., plus, minus, upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader's understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use of examples/implementations.
“One or more” includes a function being performed by one element, a function being performed by more than one element, e.g., in a distributed fashion, several functions being performed by one element, several functions being performed by several elements, or any combination of the above.
It will also be understood that, although the terms first, second, etc. are, in some instances, used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the various described implementations. The first element and the second element are both elements, but they are not the same element.
The terminology used in the description of the various described implementations herein is for the purpose of describing particular implementations only and is not intended to be limiting. As used in the description of the various described implementations and the appended claims, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements, relative movement between elements, direct connections, indirect connections, fixed connections, movable connections, operative connections, indirect contact, and/or direct contact. As such, joinder references do not necessarily imply that two elements are directly connected/coupled and in fixed relation to each other. Uses of “e.g.” and “such as” in the specification are to be construed broadly and are used to provide non-limiting examples of implementations of the disclosure, and the disclosure is not limited to such examples.
While processes, systems, and methods may be described herein in connection with one or more steps in a particular sequence, it should be understood that such methods may be practiced with the steps in a different order, with certain steps performed simultaneously, with additional steps, and/or with certain described steps omitted.
As used herein, the term “if” is, optionally, construed to mean “when” or “upon” or “in response to determining” or “in response to detecting,” depending on the context. Similarly, the phrase “if it is determined” or “if [a stated condition or event] is detected” is, optionally, construed to mean “upon determining” or “in response to determining” or “upon detecting [the stated condition or event]” or “in response to detecting [the stated condition or event],” depending on the context.
All matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the present disclosure.
This application claims the benefit of priority of U.S. Provisional Application No. 63/533,472 filed on Aug. 18, 2023, the disclosure of which are both incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63533472 | Aug 2023 | US |