Patent Application
20190063056
The present systems, methods, and apparatuses relate generally to space frames and, more particularly, to systems for increasing the structural capacity of space frames.
Three-dimensional trusses (e.g., “space frames”) have proven to be one of the most material efficient solutions for structural systems that are transferring loads across or cantilevered over a span. Generally, space frames may be used in roofs, towers, signs, solar panel racking solutions, and other applications. Within solar panel racking solutions, space frames may support solar canopies, ground mount applications, and even tracking systems. Space frames are generally comprised of various individual members—two or more parallel chords that are connected by multiple struts, which all transfer loads (e.g., forces, etc.) via internal axial stresses. Presently, space frame design is limited by two barriers: 1) heterogeneous member stress magnitude (e.g., varied levels of stress applied to members of the space frames depending on their location within the same); and 2) heterogeneous stress types that include tension and compression (e.g., various members receiving different types of stress—tension or compression—depending on their location within the space frame).
Therefore, there is a long-felt but unresolved need for a system, method, or apparatus that effectively increases the structural capacity of space frames.
Briefly described, and according to one embodiment, aspects of the present disclosure generally relate to systems, methods, and apparatuses for effectively increasing the structural capacity of space frames.
In most applications, the stresses that space frames experience are not of uniform magnitude across each of the members of a space frame. Instead, the stresses may vary by an order of magnitude or more between members due to the location of each member in the space frame and its relative location to the loads on and supports of the space frame. Loads may generally include internal loads, such as gravity, and external loads, such as wind, snow, and live and dead loads. This heterogeneity of member stresses presents a limitation to space frame design that is currently reconciled with two general approaches: 1) use of multiple members with different load capacities by changing size or strength between members depending on the particular member's location (e.g., multiple types of chords and struts with a range of load capacities); or 2) use the required member capacity at the member with the greatest stresses for all of the other members, despite members being oversized in many locations along the space frame. The first approach is generally disadvantageous because it requires careful planning and construction of a space frame to ensure the appropriate members are used in the right locations (e.g., increasing likely error when the space frame is assembled). The second approach is generally disadvantageous because it requires use of more material than is necessary to build the space frame, thereby increasing the cost and weight of the same.
Further, the stresses in space frames on each member are not typically of the same type but rather include both tension and compression at various points along the space frame. For example, chords placed at both top and bottom of a space frame may be in both tension and compression at the same time under a single load case. In contrast, chords in any single location may experience tension or compression under varying load cases (e.g., wind uplift, wind downforce, etc.). Generally, these varied scenarios are not desirable because tension and compression require different design interventions to limit failure, thereby increasing the overall cost of construction of a space frame.
The present disclosure provides a means to address both of the above limitations of space frame designs. Typically, space frames have a uniform structural capacity throughout the length of the space frame when the space frame is constructed from standard parts and materials. Nevertheless, spatial-variation in loads are highly predictable—for example, structural loads are much less at the ends and center of space frame as compared to the loads near the supports of the same. Generally, member stresses may be redistributed between members to provide more uniform stresses, and the stress type may be designed so that all critical stresses generally occur in compression, thereby enabling a single design change to increase space frame structural loading capacity.
In various embodiments, a space frame may be post-tensioned with interior cables that attach to nodes (e.g., the location where a strut is attached to a chord) and form unique load transfer paths, thereby redistributing the member stresses and generally creating uniformity amongst stress types. For example, diagonal struts generally alternate connections between a top chord and a bottom chord at a specified distance over the length of the space frame, whereby a bay is the area within a space frame that is separated by one or multiple of the diagonal struts (in one embodiment, four struts extending from the same node on the bottom chord to four different nodes on the top chords, thereby forming an inverted right regular pyramid). Generally, a post-tensioned cable (e.g., a cable that has been tensioned after the space frame has been constructed) may form a unique connection between bays spanning from a bottom-chord node in one bay to a top-chord node in an adjacent bay and then back to a bottom-chord node in the following bay. In one embodiment, the top-chord node may be located directly above the support of the space frame.
In various embodiments, variable space frame geometry may be employed to match the structural capacity of the space frame with the structural loads on the same (e.g., selective elimination of members based on the distribution of stresses within the space frame so that areas, such as the ends and midspan, with lower structural loads have fewer members). For example, the bays on the end of a space frame may be modified so that one bay supports the end of the space frame instead of two (e.g., the struts of one of the bays may be eliminated to create a “two-dimensional” or “empty” bay) or, in place or in addition to the empty bay, one or more stretch struts may be installed that extend from the node at the bottom of one bay across the space occupied by the empty bay (e.g., a “stretch bay”). Similarly, in the midspan of the space frame, between the supports, one or more bays may be removed and the adjacent bays modified so that those areas are either essentially unsupported or supported with fewer bays (e.g., any combination of empty and stretch bays, etc.). Generally, modification of any combination of the ends and midspan of a space frame may occur according to the desired structural capacity.
In one embodiment, a three-dimensional truss, comprising: a plurality of bays, wherein the plurality of bays are defined by: two parallel top chords affixed by a plurality of top chord struts, wherein the two parallel top chords define a first end and a second end; and at least one bottom chord affixed to each of the two parallel top chords by a plurality of bottom chord struts, wherein the at least one bottom chord is parallel to each of the two parallel top chords and is supported by at least two supports defining a midspan between the at least two supports; a first modified bay at the first end; and a second modified bay in the midspan.
In one embodiment, a method for modifying the structural capacity of a three-dimensional truss, comprising the steps of: assessing one or more anticipated load conditions of the three-dimensional truss; determining, based on the assessed one or more anticipated load conditions, that the three-dimensional truss should comprise a first modified bay at a first end and a second modified bay in a midspan; and installing the three-dimensional truss, wherein the three-dimensional truss comprises: a plurality of bays, wherein the plurality of bays are defined by: two parallel top chords affixed by a plurality of top chord struts, wherein the two parallel top chords define the first end and a second end; and at least one bottom chord affixed to each of the two parallel top chords by a plurality of bottom chord struts, wherein the at least one bottom chord is parallel to each of the two parallel top chords and is supported by at least two supports defining the midspan between the at least two supports; the first modified bay at the first end; and the second modified bay in the midspan.
In one embodiment, a three-dimensional truss, comprising: two parallel top chords affixed by a plurality of top chord struts, wherein the two parallel top chords define a first end and a second end; and at least one bottom chord affixed to each of the two parallel top chords by a plurality of bottom chord struts, wherein the at least one bottom chord is parallel to each of the two parallel top chords and is supported by at least two supports defining a midspan between the at least two supports; a plurality of top chord nodes along the two parallel top chords to which the plurality of top chord struts and the plurality of bottom chord struts are affixed; and a plurality of bottom chord nodes along the at least one bottom chord to which the plurality of bottom chord struts are affixed, wherein the at least one bottom chord terminates at a particular bottom chord node of the plurality of bottom chord nodes and the first end extends past the particular bottom chord node such that the two parallel top chords do not terminate in line with the at least one bottom chord.
According to one aspect of the present disclosure, the three-dimensional truss, wherein the first modified bay at the first end comprises a two-dimensional bay or a stretch bay. Furthermore, the three-dimensional truss, wherein the two-dimensional bay consists of the two parallel top chords, at least one of the plurality of top chord struts, none of the plurality of bottom chord struts, and none of the at least one bottom chord. Moreover, the three-dimensional truss, wherein the stretch bay comprises the two-dimensional bay and at least two stretch struts extending from the at least one bottom chord in an adjacent bay of the plurality of bays across the two-dimensional bay to the two parallel top chords. Further, the three-dimensional truss, further comprising a third modified bay at the first end, wherein the first modified bay at the first end comprises the stretch bay and the third modified bay at the first end comprises the two-dimensional bay. Additionally, the three-dimensional truss, further comprising a fourth modified bay at the first end, wherein the fourth modified bay at the first end comprises another two-dimensional bay. Also, the three-dimensional truss, further comprising at least two modified bays at the second end, wherein the at least two modified bays at the second end comprise a second stretch bay and a second two-dimensional bay.
According to one aspect of the present disclosure, the three-dimensional truss, wherein the at least one modified bay in the midspan comprises a two-dimensional bay or a stretch bay. Furthermore, the three-dimensional truss, wherein the two-dimensional bay consists of the two parallel top chords, at least one of the plurality of top chord struts, none of the plurality of bottom chord struts, and none of the at least one bottom chord. Moreover, the three-dimensional truss, wherein the stretch bay comprises the two-dimensional bay and at least two stretch struts extending from the at least one bottom chord in an adjacent bay of the plurality of bays across the two-dimensional bay to the two parallel top chords. Further, the three-dimensional truss, further comprising a third modified bay in the midspan, wherein the second and third modified bays in the midspan comprise stretch bays. Additionally, the three-dimensional truss, further comprising a third modified bay in the midspan, wherein the second and third modified bays in the midspan comprise two-dimensional bays. Also, the three-dimensional truss, further comprising a third and fourth modified bay in the midspan, wherein the second and third modified bays in the midspan comprise stretch bays and the fourth modified bay in the midspan comprises the two-dimensional bay.
According to one aspect of the present disclosure, the three-dimensional truss, further comprising a tensioned cable affixed to the at least one bottom chord and one of the two parallel top chords, wherein the tensioned cables transfers loads between the at least one bottom chord and the one of the two parallel top chords. Furthermore, the three-dimensional truss, wherein the tensioned cable is affixed to the at least one bottom chord directly above one of the at least two supports. Moreover, the three-dimensional truss, wherein the tensioned cable is affixed to the one of the two parallel top chords in two locations on either side of the one of the at least two supports. Further, the three-dimensional truss, wherein the tensioned cable is affixed to the one of the two parallel top chords directly above one of the at least two supports. Additionally, the three-dimensional truss, wherein the tensioned cable is affixed to the at least one bottom chord in two locations on either side of the one of the at least two supports. Also, the three-dimensional truss, wherein one or more solar panels are affixed to the tops of the two parallel top chords
According to one aspect of the present disclosure, the method, further comprising the steps of: determining, based on the assessed one or more anticipated load conditions, that the three-dimensional truss should comprise a tensioned cable affixed to the at least one bottom chord and one of the two parallel top chords, wherein the tensioned cables transfers loads between the at least one bottom chord and the one of the two parallel top chords; and after installing the three-dimensional truss, installing the tensioned cable.
According to one aspect of the present disclosure, the three-dimensional truss, further comprising: a first stretch strut affixed to the particular bottom chord node that extends to the first end, wherein the first stretch strut is affixed to a first particular top chord node of the plurality of top chord nodes on a first top chord of the two parallel top chords; and a second stretch strut affixed to the particular bottom chord node that extends to the first end, wherein the second stretch strut is affixed to a second particular top chord node of the plurality of top chord nodes on a second top chord of the two parallel top chords.
These and other aspects, features, and benefits of the claimed invention(s) will become apparent from the following detailed written description of the preferred embodiments and aspects taken in conjunction with the following drawings, although variations and modifications thereto may be effected without departing from the spirit and scope of the novel concepts of the disclosure.
The accompanying drawings illustrate one or more embodiments and/or aspects of the disclosure and, together with the written description, serve to explain the principles of the disclosure. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment, and wherein:
For the purpose of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will, nevertheless, be understood that no limitation of the scope of the disclosure is thereby intended; any alterations and further modifications of the described or illustrated embodiments, and any further applications of the principles of the disclosure as illustrated therein are contemplated as would normally occur to one skilled in the art to which the disclosure relates. All limitations of scope should be determined in accordance with and as expressed in the claims.
Whether or not a term is capitalized is not considered definitive or limiting of the meaning of a term. As used in this document, a capitalized term shall have the same meaning as an uncapitalized term, unless the context of the usage specifically indicates that a more restrictive meaning for the capitalized term is intended. However, the capitalization or lack thereof within the remainder of this document is not intended to be necessarily limiting unless the context clearly indicates that such limitation is intended.
Aspects of the present disclosure generally relate to systems, methods, and apparatuses for effectively increasing the structural capacity of space frames.
In most applications, the stresses that space frames experience are not of uniform magnitude across each of the members of a space frame. Instead, the stresses may vary by an order of magnitude or more between members due to the location of each member in the space frame and its relative location to the loads on and supports of the space frame. Loads may generally include internal loads, such as gravity, and external loads, such as wind, snow, and live and dead loads. This heterogeneity of member stresses presents a limitation to space frame design that is currently reconciled with two general approaches: 1) use of multiple members with different load capacities by changing size or strength between members depending on the particular member's location (e.g., multiple types of chords and struts with a range of load capacities); or 2) use the required member capacity at the member with the greatest stresses for all of the other members, despite members being oversized in many locations along the space frame. The first approach is generally disadvantageous because it requires careful planning and construction of a space frame to ensure the appropriate members are used in the right locations (e.g., increasing likely error when the space frame is assembled). The second approach is generally disadvantageous because it requires use of more material than is necessary to build the space frame, thereby increasing the cost and weight of the same.
Further, the stresses in space frames on each member are not typically of the same type but rather include both tension and compression at various points along the space frame. For example, chords placed at both top and bottom of a space frame may be in both tension and compression at the same time under a single load case. In contrast, chords in any single location may experience tension or compression under varying load cases (e.g., wind uplift, wind downforce, etc.). Generally, these varied scenarios are not desirable because tension and compression require different design interventions to limit failure, thereby increasing the overall cost of construction of a space frame.
The present disclosure provides a means to address both of the above limitations of space frame designs. Typically, space frames have a uniform structural capacity throughout the length of the space frame when the space frame is constructed from standard parts and materials. Nevertheless, spatial-variation in loads are highly predictable for example, structural loads are much less at the ends and center of space frame as compared to the loads near the supports of the same. Generally, member stresses may be redistributed between members to provide more uniform stresses, and the stress type may be designed so that all critical stresses generally occur in compression, thereby enabling a single design change to increase space frame structural loading capacity.
In various embodiments, a space frame may be post-tensioned with interior cables that attach to nodes (e.g., the location where a strut is attached to a chord) and form unique load transfer paths, thereby redistributing the member stresses and generally creating uniformity amongst stress types. For example, diagonal struts generally alternate connections between a top chord and a bottom chord at a specified distance over the length of the space frame, whereby a bay is the area within a space frame that is separated by one or multiple of the diagonal struts (in one embodiment, four struts extending from the same node on the bottom chord to four different nodes on the top chords). Generally, a post-tensioned cable (e.g., a cable that has been tensioned after the space frame has been constructed) may form a unique connection between bays spanning from a bottom-chord node in one bay to a top-chord node in an adjacent bay and then back to a bottom-chord node in the following bay. In one embodiment, the top-chord node may be located directly above the support of the space frame.
In various embodiments, variable space frame geometry may be employed to match the structural capacity of the space frame with the structural loads on the same (e.g., selective elimination of members based on the distribution of stresses within the space frame so that areas, such as the ends and midspan, with lower structural loads have fewer members). For example, the bays on the end of a space frame may be modified so that one bay supports the end of the space frame instead of two (e.g., the struts of one of the bays may be eliminated to create a “two-dimensional” or “empty” bay) or, in place or in addition to the empty bay, one or more stretch struts may be installed that extend from the node at the bottom of one bay across the space occupied by the empty bay (e.g., a “stretch bay”). Similarly, in the midspan of the space frame, between the supports, one or more bays may be removed and the adjacent bays modified so that those areas are either essentially unsupported or supported with fewer bays (e.g., any combination of empty and stretch bays, etc.). Generally, modification of any combination of the ends and midspan of a space frame may occur according to the desired structural capacity.
Referring now to the figures, for the purposes of example and explanation of the fundamental processes and components of the disclosed systems, methods, and apparatuses, reference is made to
In one embodiment, a space frame 100 comprises three or more chords 109 (e.g., two top chords and one bottom chord, etc.) that are connected by multiple struts 111 attached between the chords 109 (e.g., between a top chord and a bottom chord, between the two top chords, etc.). Generally, the space frame 100 may be post-tensioned (e.g., after construction and/or installation) with interior cables 101 that attach to nodes 103a and 103b on the chords 109. In various embodiments, the interior cables 101 form unique load transfer paths, thereby increasing the structural capacity of the space frame 100 by redistributing the member stresses between the members (e.g., struts 111 and chords 109) and generally creating uniformity amongst stress types within the space frame 100. This disclosure should be understood to place no limitations on the types, compositions, manners of attachment, lengths, number, and/or placement of the cables 101 within a space frame 100. For example, the cables 101 may comprise galvanized steel, steel-reinforced concrete, etc. Generally, cables 101 may be attached at multiple nodes 103a and 103b via standard attachment hardware including a loop around a bolt, attachment to a bolt with a transverse hole in the head for receiving the cables, or other means.
In various embodiments, a cable 101 may be attached to a bottom-chord node 103a (e.g., a node that is on a bottom chord 109 of a space frame 100) in one bay and to a top-chord node 103b (e.g., a node that is on a top chord 109 of a space frame 100) in an adjacent bay so that the cable 101 spans the two bays. In another embodiment, the cable 101 may be attached (e.g., via pin connections, etc.) on either end at multiple bay nodes 103a on the same bottom chord 109 and pass through a bay node 103b on one or more opposing top chords 109 so that the cable 101 spans multiple bays. In one embodiment, the top-chord node 103b may be located vertically above the support 105 of the space frame 100. In yet another embodiment, (shown in
Generally, by placing tension on the cable 101, the cable 101 will pull up on the bottom-chord nodes 103a and down on the top-chord node 103b. For example, when a downforce is placed on the end 107 of the space frame 100, the load is transferred from the bottom-chord node 103a closest to the end 107 of the space frame 100 to the top-chord node 103b and the bottom-chord node 103a towards the center of the space frame 100, thereby eliminating the additional structural capacity required to resist downforces on and deflection of the end 107 of the space frame 100.
In yet another embodiment, to resist upforce on the ends 107 of the space frame 100, a set of cables 101 (not shown in
Generally, multiple cables 101 may be used in the same bay to affect multiple load cases such as uplift and downforce, and multiple cables 101 may be used in the same space frame 100 to affect multiple support conditions through selective modification of axial stresses between tension and compression. Thus, after installation of the space frame 100 in various embodiments, cables 101 are attached to the space frame 100 and tension placed upon them to reduce the loads felt in certain points along the space frame 100. In various embodiments, the number and location of attachment points for cables 101 will vary between space frames 100 installed in different locations. For example, cables 101 on space frames 100 located in colder climates that experience significant snowfall will be positioned and tensioned to resist the downforce of accumulated snow.
Now referring to
In a conventional space frame 201, each bay is fully populated with members to provide uniform structural capacity throughout the space frame 201 (e.g., “three-dimensional bay” or “full bay”). Generally, the space frame 201 may utilize bays with less structural capacity in specific locations relative to the support conditions (e.g., bays that are not supporting loads as large as they are constructed to support because of their location)—replacing traditional bays with modified bays 207 or 209. In various embodiments, instead of a space frame 201 with two bays, one of the bays 209 may be modified/eliminated such that only one bay remains in the space frame 205 (e.g., “two-dimensional bay” or “empty bay” 209). In one embodiment, the space frame 203 may be further modified to comprise one or more stretch struts 207 that extend from the node at the bottom of one bay across the space occupied by the eliminated bay 209 (e.g., “stretch bay”—although 207 is used herein to refer to a stretch strut, it will also be used to reference the stretch bay created by installation of that stretch strut). Generally, space frame 201 will support more load than space frame 203, which will in turn support more load than space frame 205. Further, space frame 205 can enable a higher clearance of objects beneath it than space frame 203 (e.g., cars, etc.), which in turn has a higher clearance than space frame 201.
Generally, the space frames 203 and 205 have interchangeable parts that can improve performance of the space frames 203 and 205 for specified functions such as, but not limited to weight, aerodynamics, cost, install time, aesthetics and or access. In one embodiment, removal of each bay results in a reduction of the following materials: one length of the lower chord, four struts, one lower-chord bracket, two bolts, and two nuts. These materials reduce the weight and wind-resistance of the space frame 203 and 205, thereby increasing its structural capacity.
In one embodiment, additional supports 211 may be added to a particular bay to increase its structural capacity. For example, four supports 211 may be connected between the struts of a particular bay to increase the buckling capacity of the same. Even though they are shown on the conventional space frame 201, the additional supports 211 are not conventional (conventional here means a space frame with two full, unmodified bays).
Referring now to
Generally, the modular design of each bay enables permutations of the ends 107 of the global space frame configuration, as shown throughout
Now referring to
Although not shown herein, a particular space frame may be modified to comprise multiple different end and midspan conditions (e.g., zero/one/two modified end conditions, zero/one/two/three/etc. modified midspan conditions, etc.).
While various aspects have been described in the context of a preferred embodiment, additional aspects, features, and methodologies of the claimed inventions will be readily discernible from the description herein, by those of ordinary skill in the art. Many embodiments and adaptations of the disclosure and claimed inventions other than those herein described, as well as many variations, modifications, and equivalent arrangements and methodologies, will be apparent from or reasonably suggested by the disclosure and the foregoing description thereof, without departing from the substance or scope of the claims. Furthermore, any sequence(s) and/or temporal order of steps of various processes described and claimed herein are those considered to be the best mode contemplated for carrying out the claimed inventions. It should also be understood that, although steps of various processes may be shown and described as being in a preferred sequence or temporal order, the steps of any such processes are not limited to being carried out in any particular sequence or order, absent a specific indication of such to achieve a particular intended result. In most cases, the steps of such processes may be carried out in a variety of different sequences and orders, while still falling within the scope of the claimed inventions. In addition, some steps may be carried out simultaneously, contemporaneously, or in synchronization with other steps.
The embodiments were chosen and described in order to explain the principles of the claimed inventions and their practical application so as to enable others skilled in the art to utilize the inventions and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the claimed inventions pertain without departing from their spirit and scope. Accordingly, the scope of the claimed inventions is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.
This application claims priority to, the benefit under 35 U.S.C. § 119 of, and incorporates by reference herein in its entirety U.S. Provisional Patent Application No. 62/550,957, filed Aug. 28, 2017, and entitled “Systems, Methods, and Apparatuses for Modification of the Structural Capacity of Space Frames.”
| Number | Date | Country | |
|---|---|---|---|
| 62550957 | Aug 2017 | US |
