Patent Grant
12065833
The described embodiments relate to structural members and systems, and more particularly to pre-stressed structural members and systems for the construction of floors and roofs.
Various roof and floor framing systems are commonly utilized to span mid to long distances (e.g., 40 feet or more) encountered in many types of buildings. Currently, the most cost effective of these roof and floor framing systems rely on either predesigned and prefabricated open web steel trusses or custom designed trusses fabricated of steel or timber. Custom designed and fabricated trusses are typically much more expensive than pre-designed, fabricated trusses. Pre-designed, fabricated trusses are typically selected from an existing catalog of available trusses based on specific project loads and span. Pre-designed trusses are typically constructed at fabrication shops with tooling and processes already in place to cost efficiently and repetitively fabricate the predesigned trusses.
Prefabricated trusses are typically manufactured off-site and transported to the construction site in a single span, or in multiple sections. Shipping to the construction site in multiple sections is required in instances when the length of span exceeds permitted shipping lengths. Multiple sections are assembled on-site to realize a full length span by field splicing the top and bottom chords of the truss structure. Unfortunately, on-site assembly of truss sections adds cost and erection time to the project due to relatively expensive field bolting, welding, or both, and associated inspections.
Prefabricated trusses are typically fabricated in one configuration and assembled in a one dimensional array at regular spacing intervals. Typically, the top chord member of each truss of the array is a linear structural member, and the top chord members are erected in position in a horizontal plane (i.e., approximately perpendicular to the direction of gravitational force). Similarly, the bottom chord member of each truss of the array is located in parallel plane below the top plane. In this manner, the array of trusses forms a top level plane upon which a floor or roof structure may be constructed and a bottom level plane upon which a ceiling structure may be constructed. In one example, a roof subassembly is often constructed using a secondary assembly system mounted to the top of the flat subroof plane, attached to the array of trusses to create sufficient roof slope for proper roof drainage.
Custom designed trusses may be constructed with curved or sloping top and bottom chords and intermittent web members that connect the top and bottom chords. The custom designed truss member is repeated across the array, resulting in a two dimensional truss profile across the structural assembly. However, to achieve the two-dimensional profile, the web of each truss connecting the curved or sloping top and bottom chords varies in height along the length of the truss. In addition, each connection of web members to top and bottom chords includes a unique joint configuration, which complicates manufacture and assembly processes. As a result the cost to fabricate such a truss is considerably higher than the cost of repetitively fabricated, linear truss shapes easily manufactured in higher volume.
In some examples, assembled trusses are left fully exposed to view from the space below. In some other examples, assembled trusses are concealed with a separate ceiling subassembly. If left fully exposed, ductwork and other utilities are also left exposed, leaving a more industrial, exposed structural appearance. If a ceiling subassembly is installed, the trusses, ductwork, and other utilities are concealed from view by the separate ceiling assembly. In some examples, a ceiling subassembly includes a structural falsework to support acoustic tile, gypsum board, or other finish ceiling materials placed to create a level ceiling system.
In summary, the typical approach to the construction of buildings today includes multiple components: structural trusses, a sloped roofing subassembly mounted to the structural trusses from above, and optionally, a ceiling subassembly mounted to the structural trusses from below.
Currently, pre-designed truss systems are often selected to save cost compared to traditional custom designed truss systems. However, the implementation of pre-designed truss systems gives rise to a number of disadvantages. For example, the need to separately construct a roof subassembly to achieve roof slope and a separate ceiling assembly adds significant cost and time to a construction project. Moreover, linear trusses are often aesthetically unacceptable or undesirable, requiring construction of separate subassemblies to achieve a desired architectural design.
As spans become longer, traditional timber trusses typically become less economical or impossible to realize due to connection capacity limits and costs. Structural steel is the preferred material for longer spans, but steel is relatively expensive. Furthermore, while reclaimed steel can be used for steel trusses, steel is not a renewable resource and therefore typically carries a larger carbon footprint. In another example, the field assembly of steel trusses requires expensive and inspection intensive site fastening (e.g., welding, bolting, etc.).
In summary, current mid and long span roof and floor framing systems suffer from a number of disadvantages from both a cost and sustainability perspective. The economic cost and environmental issues become particularly acute when the required span exceeds 40 feet in length, complex architectural features are incorporated, or both. A sustainable roof and floor framing system integrating high stiffness support, roof shape, and ceiling shape functions with a high degree of architectural design flexibility is desired. In addition, it is desired that the components of the sustainable roof and floor framing system be light weight, compact, easily fabricated off-site using automated technology available to the mass timber construction market and be assembled on-site with a minimum of costly field fastening operations and inspections.
A sustainable, integrated framing system and methods of assembly thereof are presented herein. In some embodiments, a roof, primary structure and a ceiling or a floor primary structure are structurally defined and supported by pre-fabricated load bearing ribs of the sustainable, integrated framing system. The pre-fabricated load bearing ribs facilitate efficient building erection on-site without expensive and time consuming welding and associated inspections.
In one aspect, a sustainable, integrated framing system includes a number of load bearing ribs. Each rib includes one or more compression chord elements, a web element extending below the compression chord elements, and one or more adjustable tension elements embedded within the web element. In a further aspect, an end support node is attached to each end of a load bearing rib structure, and the one or more tension elements are tensioned against the end support nodes.
In a further aspect, a number of load bearing ribs are arranged in parallel in one direction to form a roof or floor of a building structure. An arrangement of load bearing ribs in a single direction is particularly well suited for minimum cost and moderate span lengths.
In another further aspect, a number of load bearing ribs are arranged in two different directions in a grid configuration to form a roof or floor of a building structure. In this arrangement, the arrangement of load bearing ribs oriented in one direction effectively braces the load bearing ribs arranged in a different direction to stabilize the roof or floor structure under gravity, seismic, and wind loads.
In another further aspect, a number of load bearing ribs arranged in parallel in one direction are laterally braced at the bottom web structure to stabilize each load bearing rib and prevent lateral buckling under gravity loading, seismic loading, and wind loading.
In another further aspect, the depth of a web structure is not uniform along the length of a load bearing rib. In this manner, the bottom profile of a web structure is shaped to meet aesthetic or functional design objectives independent of the load carrying capability of the load bearing rib.
In another further aspect, a load bearing rib includes a top web structure extending above the compression chord member(s). In some embodiments, the height of the top web structure is uniform along the length of the load bearing rib. In some other embodiments, the height of the top web structure is non-uniform along the length of the load bearing rib.
In some embodiments, some or all load bearing ribs of an array of load bearing ribs have different top and/or bottom profiles. In these embodiments, the shape of the overall topography formed by the top and/or bottom profiles of the array of load bearing ribs is unique in three dimensions. In some embodiments, a ceiling is formed using the array of load bearing ribs to support a ceiling or ceiling subassembly having a complex three-dimensional profile visible to the room environment. In some embodiments, a roof is formed using the array of load bearing ribs to support a roofing subassembly having a complex profile to promote three dimensional roof drainage or to create a more complex roofscape.
In another further aspect, the web structure includes one or more transverse penetrations, for example, to pass mechanical, electrical, and plumbing elements through the load bearing rib or for aesthetic purposes.
In another further aspect, load bearing ribs are manufactured off-site in linear sections and assembled and installed together, on-site.
The foregoing is a summary and thus contains, by necessity, simplifications, generalizations and omissions of detail; consequently, those skilled in the art will appreciate that the summary is illustrative only and is not limiting in any way. Other aspects, inventive features, and advantages of the devices and/or processes described herein will become apparent in the non-limiting detailed description set forth herein.
Reference will now be made in detail to background examples and some embodiments of the invention, examples of which are illustrated in the accompanying drawings.
A sustainable, integrated framing system and methods of assembly thereof are presented herein. The sustainable, integrated framing system is suitable for relatively large, unsupported spans found in the floor and roof assemblies of many modern, open concept buildings. As a timber-based framing system, the timber structural elements are renewable and retain the carbon sequestered during tree growth prior to harvest.
In some embodiments, a roof, primary structure, and a ceiling are structurally defined and supported by pre-fabricated load bearing ribs of the sustainable, integrated framing system. Furthermore, the resulting roof and ceiling structures may be constructed with unique, complex three-dimensional topography. The pre-fabricated load bearing ribs are designed and detailed using available software based design tools, such as Computer Aided Design (CAD) software tools, Building Information Modeling (BIM) software tools, other structural analysis software, etc. The resulting Building Information Model (BIM) may be directly communicated to Computer Numerically Controlled (CNC) cutting and gluing equipment for automated fabrication. The pre-fabricated load bearing ribs facilitate efficient building erection on-site without expensive and time consuming welding and associated inspections.
In one aspect, a sustainable, integrated framing system includes a number of load bearing ribs. Each rib includes one or more compression chord elements, a web element extending below the compression chord element, and one or more adjustable tension elements embedded within the web element. Each load bearing rib is fabricated from commercially available, sustainable timber framing components.
As depicted in
In general, one or more chord members may be placed on one or both sides of a web structure or on top of a web structure. In some embodiments, a chord member is bonded to the web structure using adhesive products, mechanically fasteners, etc., either at a manufacturing facility or on-site. For example, a load bearing rib may include one chord element disposed on one side of a web structure 102, two chord elements disposed on either side of web structure 102 as depicted in
In addition, as depicted in
As depicted in
In general, a tunnel may be fabricated within one or more panel laminations by cutting the lamination along the length of the load bearing rib, or otherwise including a vertically spaced gap between upper and lower lamination pieces along the length of the load bearing rib between the end support nodes. Each tunnel is fabricated to a prescribed shape profile prior to placing and gluing panel laminations to form the web structure of each load bearing rib.
Tunnel cuts may be performed using any of a standard gantry, table, or portable CNC cutting machine, saw, or other cutting tools to generate the prescribed curved profile. In general, a tunnel may be cut into a layer to a depth that is only a fraction of the total thickness of one or more layers, through an entire layer, through multiple layers, or any combination thereof.
As depicted in
Importantly, tunnel 105 is fabricated in a curved shape that reaches its highest point (highest vertical elevation or vertical position) at each end of load bearing rib 100. In a preferred embodiment, the curved shape terminates at each end of load bearing rib 100 at a vertical elevation at or near the vertical centroid of chord element 101. In some embodiments, the curved shape slopes downwards and reaches its lowest vertical elevation at or near the mid-span of load bearing rib 100, then slopes upwards to opposite ends of the load bearing rib. In general, the path traced by the tunnel 105 is shaped as a curve having zero slope at a single location between endpoints of the load bearing rib. The location of zero slope is typically located at or near the mid-span of the web structure in the longitudinal direction where a vertical elevation of the tension element reaches its lowest point. In this manner, the load carried by the tension element 104 is evenly distributed along the curved path. In some embodiments the curved shape is a parabolic shape, a catenary shape, or any other suitable shape having zero slope at a single location between the endpoints of the load bearing rib.
In some embodiments, tension element 104 is located in a duct (not shown) located within tunnel 105 along a least a portion of the length of tunnel 105, e.g., near the ends of tunnel 105, or the entirety of tunnel 105. In general, the duct may be any suitable structure, e.g., polymer tube, metal tube, etc. In some embodiments, the duct is installed during fabrication of a load bearing rib in a CNC cut tunnel to facilitate smooth and easy field threading of a tension element. In addition, a duct may be desirable to reduce friction when the tensile element is installed, reducing friction losses during tensile loading, or both.
In a further aspect, an end support node is attached to each end of a load bearing rib structure. An end support node may be fabricated from any of timber, steel, concrete, masonry, or any other building material.
As depicted in
In some embodiments, at each end of the load bearing rib 100, the chord member 101 also rests against a horizontally oriented support structure to position the load bearing rib 100 with respect to the overall building structure and provide support to the load bearing rib before and after any tendon elements are stressed and locked into position.
In a further aspect, the depth of a web structure is not uniform along the length of a load bearing rib. In this manner, the bottom profile of a web structure is shaped to meet aesthetic or functional design objectives independent of the load carrying capability of the load bearing rib.
In general, the one or more tension elements provide a suspension system associated with a load bearing rib as described herein. Thus, the material at the bottom web structure below the tension element does not influence the strength and deflection behavior of the load bearing rib. For this reason, the profile of the bottom web structure below the tension element may be selected to achieve a desired aesthetic effect.
In some embodiments, all load bearing ribs of an array of load bearing ribs have the same bottom profile. In this manner, a two dimensional shape may be extended into the third dimension. In some embodiments, some or all load bearing ribs of an array of load bearing ribs have different bottom profiles. In these embodiments, the shape of the overall topography formed by the bottom profiles of the array of load bearing ribs is unique in three dimensions. In some embodiments, a ceiling is formed by exposure of the array of load bearing ribs to the room environment. In some other embodiments, a ceiling is formed using the array of load bearing ribs to support a ceiling subassembly having a complex three-dimensional profile visible to the room environment.
In some embodiments, the bottom profile of the bottom web structure is formed using the same cutting tools employed to form the tunnel 115 through which tension element 114 is embedded.
In a further aspect, the web structure includes one or more transverse penetrations, for example, to pass mechanical, electrical, and plumbing elements through the load bearing rib or for aesthetic purposes.
In general, the primary purpose of the web structure is to separate each top chord element and each tension element in the vertical direction. The tension elements are not bonded to the web structure and are free to slip within the tunnel, duct, or both. Thus, there is no induced shear force transferred between tension elements and compression chords, limiting the induced stress in the web structure to the relatively small vertical compression load due to the weight of the load bearing rib per unit length above the tension element, and the weight of a floor or roof assembly per unit length along the load bearing rib. Due to the limited loading of the web structure, itself, penetrations of varying size may be cut through the full web thickness or through a portion of the laminations of the web structure at any location of the web structure. Web structure penetrations may be of any shape, configuration, and size to accommodate mechanical, electrical, and plumbing components, aesthetic purposes, or other reasons provided sufficient web material remains above the tension elements and below the compression chord sufficient to support the weight per unit length along the load bearing rib.
In a further aspect, a load bearing rib includes a top web structure extending above the compression chord. In some embodiments, the height of the top web structure is uniform along the length of the load bearing rib as illustrated in
As depicted in
In some embodiments, the top web structure is employed to support a roof subassembly that enables unique, customizable two or three dimensional roof profiles. In the embodiments depicted in
As depicted in
In general, a roof diaphragm or a floor diaphragm is fastened to a load bearing rib in a conventional manner (e.g., adhesives, mechanical fasteners, or both). By way of non-limiting example, suitable diaphragm materials include plywood, tongue and groove decking, cross laminated timber, nail laminated timber, dowel laminated timber, steel decking, a composite concrete slab, and/or other systems suitable to span between load bearing ribs and support the given floor or roof gravity loads at the given spacing between load bearing ribs.
In a further aspect, load bearing ribs are manufactured off-site in linear sections and assembled and installed together, on-site.
In some embodiments, load bearing ribs are shipped and lifted into place on-site as a single continuous length. However, if the required length of a load bearing rib exceeds permitted shipping length or becomes impractical to fabricate, ship, or erect as a single unit, a load bearing rib is fabricated off-site and shipped in multiple sections and field spliced either prior to lifting in place or field spliced in place during field erection. The location of field splices is flexible because the forces born by the web structure are nominal along the entire length of the load bearing rib. In some embodiments, the sections are assembled on-site, the tension element(s) are threaded through the assembled load bearing rib, the assembled load bearing rib is lifted into place, and the tension element(s) are tensioned and locked into place as described hereinbefore.
In some embodiments, vertically oriented splices are generated by staggering outer and inner panel laminations horizontally along each vertical splice to create a tongue and groove joint. In some embodiments, horizontally oriented splices are generated by staggering outer and inner panel laminations vertically along each horizontal splice to create sufficient overlap between laminations for fastening. The laminations are connected by structural gluing, mechanically fastening, or both.
To assure the chord elements are maintained in compression, a splice connection between mating compression chords must fit tight in end-to-end bearing to maintain compression continuity. In some embodiments, a direct connection is employed. In some other embodiments, metal bracketry is employed to ensure the integrity of the field splice and prevent compression buckling. In some embodiments there is no direct connection employed, and the fastened diaphragm is employed to prevent compression buckling.
In some embodiments, each load bearing rib includes a single tension element as depicted by way of non-limiting example in
In a further aspect, a number of load bearing ribs are arranged in parallel in one direction to form a roof or floor of a building structure. In some embodiments, the array of load bearing ribs are arranged at regular spacing interval (e.g., spaced with a distance in a range from two feet to twenty feet). An arrangement of load bearing ribs in a single direction is particularly well suited for minimum cost and moderate span lengths.
In a further aspect, a number of load bearing ribs arranged in parallel in one direction are laterally braced at the bottom web structure to stabilize the roof or floor structure under gravity loading, seismic loading, and wind loading. Gravity loading of a load bearing rib is a vertical load carried by an installed load bearing rib and the dead load portion of this load, due to building material weights, is sustained at all times. However, a slight horizontal offset of the high tension load of the tension element may cause a lateral instability of the rib structure. In addition, seismic or wind events give rise to intermittent lateral forces or uplift forces that may potentially destabilize the load bearing rib structure and cause buckling. To counteract these forces, the load bearing ribs are cross-braced at or near the bottom of the bottom web structure to laterally brace the ribs out of plane of the rib span direction. The bracing is achieved by connecting the bottom web structures of adjacent load bearing ribs in a direction perpendicular to the span of the load bearing rib with a bracing element. By way of non-limiting example, a bracing element includes a pipe, a timber member, a cable connected to the web structure, etc.
In a further aspect, a number of load bearing ribs are arranged in two different directions in a grid configuration to form a roof or floor of a building structure. In this arrangement, the arrangement of load bearing ribs oriented in one direction effectively braces the load bearing ribs arranged in a different direction to stabilize the roof or floor structure under gravity, seismic, and wind loads.
In some embodiments, the two dimensional array of load bearing ribs are arranged at regular spacing intervals in both directions (e.g., evenly spaced with a distance in a range from two feet to twenty feet in both directions). An arrangement of load bearing ribs in two directions is particularly well suited for longer span lengths, reduced rib depth, complex three-dimensional ceiling profiles using the two dimensional array as either an exposed grid system or as a falsework for ceiling finishes, three-dimensional roof structure to support complex roof drainage patterns, a unique aesthetic roof scape, wind break, green roof scape, etc.
As described hereinbefore, each load bearing rib is supported at both ends by an end support node suitable to support the required horizontal and vertical loads including, but not limited to, the live load associated with the proposed floor or roof usage, the dead load associated with the weight of the load bearing ribs, floor or roof assembly, any applicable ceiling assembly, and wind and seismic forces. Depending on the length of the span, end support nodes may include wood, steel, concrete, masonry or any other common building material.
Since the vertical loads are largely supported by the tension elements, each end connection node must be able to perform a number of functions including: serve as a reaction block during tensioning of the tension elements, transfer the vertical load component from the tension elements into the supporting structure below, and transfer the horizontal component of the tensile force in the tension elements to the compression chord member (s) near the top of each load bearing rib. To avoid inducing more flexure into the load bearing ribs and chord members, the point of anchorage of a tension element is generally aligned with the vertical centroid of the chord member (s).
In general, an end support node includes a reaction plate comprising steel angle, channel, or other structural steel shape at which the end of the chord member (s) terminate. The end support node bears against a timber, steel, concrete, or built-up light gauge steel framing column. The framing column may be an isolated column or placed within a framed wall. The end support node includes a locking element to maintain tension in the tensioning element, and optionally a steel wedge structure to align the tensioning element with the reaction plate. In general, a steel wedge structure includes a surface that is perpendicular to the tension element as the tension element exits the load bearing rib and another surface that is aligned with the reaction plate. The wedge structure may be fastened (e.g., screwed, bolted, welded) to the reaction plate of the end support node.
In some embodiments, the end support nodes are integrated with each load bearing rib and tensioned off-site, on-site, or both. In these embodiments, the tensioned load bearing ribs are placed on-site, and the integrated end support nodes are fastened to the building structure.
In some embodiments, an end support node is integrated with a framing post and the load bearing rib is attached to the end support node during placement of the load bearing rib, and tensioned after placement.
In general, the tensioning of the tension element is performed from one end of each load bearing rib or both ends of each load bearing rib if appropriate to minimize frictional drag along the length of the tension element.
In addition, the end of the chord members fits up against the web 182 of the column 181. In this manner, web 182 is the reaction plate of the end support node. Tension element 184 extends through a hole in web 182 at approximately the middle of the depth of the chord members and through wedge 185. A tensioning device pulls on tension element 184 and pushes against web 182 and/or wedge 185 until the desired tension of tension element 184 is reached. A locking element 186 (e.g., clamp, nut, wedge, etc.) locks tension element 184 to an anchorage system that bears against web 182 to maintain the tension after removal of the tensioning device.
In some embodiments, an end support node is connected to either the framing column or the load bearing rib before rib placement and the load bearing rib is tensioned after placement.
The bottom of the chord members of the load bearing rib 193 rests on a horizontally oriented leg of the L-shaped steel member 197 (a.k.a., steel angle). In addition, the end of the chord members fits up against a vertically oriented leg of the L-shaped steel member 197. In this manner, the L-shaped steel member 197 is the reaction plate of the end support node. Tension element 194 extends through a hole in L-shaped steel member 197 and wedge 196 at approximately the middle of the depth of the chord members.
A tensioning device (e.g., a stressing or hydraulic jack) pulls on tension element 194 and pushes against L-shaped steel member 197 via steel wedge element 196 until the desired tension of tension element 194 is reached. The L-shaped steel member acts as an anchorage plate and the steel wedge element 196 includes a surface that is perpendicular to the tension element as the tension element exits the load bearing rib. A locking element 195 (e.g., clamp, nut, wedge, etc.) locks tension element 194 to L-shaped steel member 197 to maintain the tension after removal of the tensioning device.
In some embodiments, an end support node is integrated with a wide flange column segment. In some of these embodiments, the load bearing rib is attached to the wide flange column segment during placement of the load bearing rib, and tensioned after placement. In some of these embodiments, the load bearing rib is attached to the wide flange column segment, and tensioned before and/or after placement of the load bearing rib.
In addition, the end of the chord members fits up against web 202. In this manner, web 202 is the reaction plate of the end support node. Tension element 204 extends through a hole in web 202 at approximately the middle of the depth of the chord members and through wedge 205. A tensioning device pulls on tension element 204 and pushes against web 202 and/or wedge 205 until the desired tension of tension element 204 is reached. A locking element 206 (e.g., clamp, nut, wedge, etc.) locks tension element 204 to an anchorage system that bears against web 202 to maintain the tension after removal of the tensioning device.
In some embodiments, the tension elements are tensioned to the desired stress level after the load bearing ribs are erected. In another embodiment, the tension elements are partially tensioned prior to erection and again tensioned after erection of load bearing ribs. In some examples, the tension elements are slightly over tensioned to account for top chord elastic and creep shortening. In some examples, the tension elements are tensioned multiple times over their lifetime to account for realized top chord elastic and creep shortening.
Commercially available hydraulic jacks may be employed to stress each tension element. The induced stress may be measured directly using a stress gauge or may be inferred based on measured elongation (i.e., a measure of stain) and the known mechanical properties of the tension element.
In block 301, at least two panel layers are laminated together to form a web structure. A continuous tunnel is present within the web structure and aligned with at least one of the panel layers. The continuous tunnel extends from one longitudinal end of the web structure to an opposite longitudinal end of the web structure. A vertical position of the continuous tunnel at or near a midpoint of the web structure in a direction of longitudinal extent is below a vertical position of the continuous tunnel at the longitudinal ends of the web structure.
In block 302, one or more chord members extending in the direction of longitudinal extent are attached to the web structure at one or both sides of the web structure. A dimension of the one or more chord members in the vertical direction is less than a dimension of the web structure in the vertical direction.
In block 303, a tension element is located through the continuous tunnel formed within the web structure. The tension element is free to slide with respect to the continuous tunnel.
Although certain specific embodiments are described above for instructional purposes, the teachings of this patent document have general applicability and are not limited to the specific embodiments described above. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 749987 | Franke | Jan 1904 | A |
| 3079649 | Willatts | Mar 1963 | A |
| 3251162 | Strimple | May 1966 | A |
| 3925938 | Molen | Dec 1975 | A |
| 5175968 | Saucke | Jan 1993 | A |
| 8607528 | Ellen | Dec 2013 | B2 |
| 20110016824 | Thornton | Jan 2011 | A1 |
| 20140259463 | Chandra | Sep 2014 | A1 |
| 20220220740 | Thompson | Jul 2022 | A1 |
| Number | Date | Country |
|---|---|---|
| WO-2012083391 | Jun 2012 | WO |
