Abstract:
An elongated structural ceiling grid member including an open-ended upper portion, an open-ended lower portion, and first and second flanges. The open-ended upper section is formed by a floor and a first set of second parallel and spaced sidewalls extending from and substantially perpendicular to the floor. The open-ended upper portion has an opening opposite the floor and defined by the first and second parallel and spaced sidewalls. The open-ended lower portion is formed by a ceiling and a second set of parallel and spaced sidewalls that extend from and are substantially perpendicular to the ceiling. The open-ended lower portion has a second opening opposite the ceiling and defined by the third and fourth parallel and spaced sidewalls. The first flange is attached to and extends perpendicular to the third parallel and spaced sidewall and the second flange is attached to and extends perpendicular to the fourth parallel and spaced sidewall.

Description:
FIELD OF THE INVENTION 
     This invention relates to ceiling grids, comprised of intersecting and perpendicular rows of elongated struts or members, that are attached to and suspended from ceilings of rooms and other building spaces, such as office spaces, storage areas, and data centers, to function as the framework for directly and/or indirectly supporting other structural members and room or building accessories. In particular, this invention relates to elongated struts or members, both structural and non-structural, that can be used in such a ceiling grid. 
     BACKGROUND OF THE INVENTION 
     Ceiling grids comprised of intersecting and perpendicular rows of elongated struts or members, both structural and non-structural struts or members, have been in use for decades. Those ceiling grids are usually directly attached to and suspended from the structure comprising the ceiling of a room or other building space, such as a concrete slab. The elongated structural struts or members of those ceiling grids directly or indirectly support other structural members and room or building accessories, such as light fixtures, HVAC conduits, sprinkler systems, etc., in the rooms or other building spaces in which they are installed. 
     In certain environments, it is desirable that the ceiling grids include elongated structural struts or members that have (1) the desired load capacity and (2) an architectural or aesthetic finish when viewed from underneath the ceiling grid. In addition, it is often desirable that a variety of other structural members and room or building accessories can be attached to or otherwise supported by the elongated structural struts or members at any location along the elongated structural struts or members. 
     While some elongated structural struts or members for ceiling grids have been developed that have (1) the desired load bearing capacity, (2) an architectural or aesthetic appearance when viewed from underneath the ceiling grid, and (3) the capability that other structural members and room or building accessories can be attached to the elongated structural struts or members at any location along the struts or members, there is always a need for elongated structural struts or members for ceiling grids with improved load bearing capacity and/or aesthetic appearance, and with the capability that other structural struts or members and room or building accessories can be attached to the elongated structural struts or members at any location along the struts or members. 
     In addition, there is always a need for improved elongated non-structural struts or members for ceiling grids that can be readily and securely attached to the elongated structural struts or members of those grids and have an architectural or aesthetic finish when viewed from underneath the grids. 
     This invention addresses those needs, as well as other needs that are readily apparent to those of skill in the art. 
     SUMMARY OF THE INVENTION 
     An elongated structural ceiling grid member according to one embodiment of this invention may include an open-ended upper portion formed by a floor and a first set of parallel and spaced sidewalls extending from and substantially perpendicular to the floor. Each of the first set of parallel and spaced sidewalls may include a lower flat wall section and an upper section that is continuous with the lower flat wall section and extends towards the other of the first set of parallel and spaced sidewalls. The upper-ended upper portion may have a first opening (1) opposite the floor and (2) defined by the upper sections of the first set of parallel and spaced sidewalls. The elongated structural ceiling grid member of this embodiment may also include an open-ended lower portion formed by a ceiling and a second set of parallel and spaced sidewalls extending from and substantially perpendicular to the ceiling. Each of the second set of parallel and spaced sidewalls may include an upper flat wall section and a lower section that is continuous with the upper flat wall section and extends towards the other of the second set of parallel spaced sidewalls. The open-ended lower portion may have a second opening (1) opposite the ceiling and the first opening and (2) defined by the second set of parallel and spaced sidewalls. The elongated structural ceiling grid member of this embodiment may also include first and second flanges. The open-ended upper portion, the open-ended lower portion and the first and second flanges may have longitudinal axes that are substantially parallel to the longitudinal axis of the elongated structural ceiling grid member. The floor and ceiling may be integral. The first flange may be attached to the lower section of one of the second set of parallel and spaced sidewalls and extend substantially perpendicular in the lateral direction to the upper flat wall section of that parallel and spaced sidewall. The second flange may be attached to the lower section of the other of the second set of parallel and spaced sidewalls and extend substantially perpendicular to the upper flat wall section of that parallel and spaced sidewall. 
     In some embodiments of the elongated structural ceiling grid members of this invention, the upper sections of the first set of parallel and spaced sidewalls may be hooks having free ends that are located in vertical planes between the vertical planes of the lower flat wall sections of the first set of parallel and spaced sidewalls. 
     In other embodiments of the elongated structural ceiling grid members of this invention, the lower sections of the second set of parallel and spaced sidewalls may be hooks that have free ends that are located in vertical planes between the vertical planes of the upper flat wall sections of the second set of parallel and spaced sidewalls. 
     In yet other embodiments of the elongated structural ceiling grid members of this invention, the first and second flanges may be elongated bars that extend laterally beyond and outside of the upper flat wall portions of the second set of parallel and spaced sidewalls. 
     In further embodiments of the elongated structural ceiling grid members of this invention, the lower flat wall portions of the first set of parallel and spaced sidewalls are in substantially the same planes as the upper flat wall portions of the second set of parallel and spaced sidewalls. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top perspective view of an elongated structural strut for ceiling grids according to one embodiment of this invention. 
         FIG. 2  is an elevation view of the elongated structural strut for ceiling grids of  FIG. 1 . 
         FIG. 3  is a top perspective view, partially sectionalized and partially in phantom for clarity, of four of the elongated structural strut for ceiling grids illustrated in  FIGS. 1 and 2 , joined by a connector to form intersecting and perpendicular rows of the struts. 
         FIG. 4  is an elevation view of three of the elongated structural strut for ceiling grids illustrated in  FIGS. 1 and 2 , joined by a connector to form a T-intersection of the struts. 
         FIG. 5  is a top perspective view of an elongated non-structural strut for ceiling grids according to one embodiment of this invention. 
         FIG. 6  is an elevation view of the elongated non-structural strut for ceiling grids of  FIG. 5 . 
         FIG. 7  is a top perspective view of two of the elongated non-structural strut of  FIGS. 5 and 6  attached to an elongated structural strut of  FIGS. 1 and 2 , to form an intersection of perpendicular rows of the elongated non-structural struts and the elongated structural struts. 
         FIG. 8  is a top perspective view of a ceiling grid comprised of a plurality of the elongated structural strut for ceiling grids of  FIGS. 1 and 2  and a plurality of the elongated non-structural strut of  FIGS. 5 and 6 . 
         FIGS. 9A, 9B, 9C and 9D  are a series of schematic views illustrating how the connector of  FIG. 3  can be attached to the elongated structural strut for ceiling grids of  FIGS. 1 and 2 . 
         FIG. 10  is a top perspective view, partially in phantom for clarity, of two of the elongated structural strut for ceiling grids illustrated in  FIGS. 1 and 2 , joined by a connector to form a corner of a ceiling grid. 
     
    
    
     DETAILED DESCRIPTION 
     As stated,  FIGS. 1 and 2  illustrate one embodiment of an elongated structural strut for ceiling grids of this invention, elongated structural strut  10 . Elongated structural strut  10  has a longitudinal axis that extends the length of elongated structural strut  10 . 
     Elongated structural strut  10  includes upper portion  12 , lower portion  14  and lower flanges  16  and  18 . In this embodiment of the elongated structural struts of the invention, upper portion  12  and lower portion  14  are integral, and extruded from stock of the same material. In other embodiments of the elongated structural struts of this invention, upper portion  12  and lower portion  14  can be two or more separate components joined together by welding or any other well-known fastening method/mechanism. 
     Upper portion  12  includes floor  20  and sidewalls  22  and  24 , which, in this embodiment of the elongated structural struts of this invention, are integral. In other embodiments of the elongated structural struts of this invention, the floor and sidewalls of the upper portion can be multiple components joined together. 
     In this embodiment of the elongated structural struts of the invention, sidewalls  22  and  24  are parallel, mirror images that are substantially perpendicular to floor  20 . 
     Also, in this embodiment of the elongated structural struts of the invention, sidewall  22  includes flat wall portion  23  and hook  26 . Flat wall portion  23  begins at a longitudinal edge of floor  20  and extends upward. Hook  26  is formed by the upper portion of sidewall  22 , above and continuous with flat wall portion  23 . 
     Similarly, in this embodiment of the elongated structural struts of the invention, sidewall  24  includes flat wall portion  25  and hook  28 . Flat wall portion  25  begins at the other longitudinal edge of floor  20  and extends upward. Hook  28  is formed by the upper portion of sidewall  24 , above and continuous with flat wall portion  25 . 
     Floor  20  and sidewalls  22  and  24  define upper chamber  50  with opening  52  defined by hooks  26  and  28 . 
     The function of hooks  26  and  28  is to provide portions of sidewalls  22  and  24  that extend inwardly from flat wall portions  23  and  25 , respectively, without closing opening  52 . In use, hooks  26  and  28  can engage support members that are used to attach elongated structural strut  10  to a ceiling, as explained below. In other embodiments of the elongated structural struts of the invention, the upper portions of the sidewalls can have any shape that results in those portions extending inwardly, without closing the opening between the sidewalls. One advantage of hooks  26  and  28  over other “shapes” is that hooks  26  and  28  provide a “loop” to firmly engage a rod, flange, etc. that fits into and is received in the “loop.” 
     Also, the sidewalls of the upper portions of other embodiments of the elongated structural struts of this invention do not have to include flat wall portions, such as flat wall portions  23  and  25 . Rather, the sidewalls can have any configuration and/or shape that results in the sidewalls partially defining a chamber between them. 
     Lower portion  14  includes ceiling  30  and sidewalls  32  and  34 , which, in this embodiment are integral. In other embodiments of the elongated structural struts of this invention, the ceiling and sidewalls of the lower portion can be multiple components joined together. 
     In this embodiment of the elongated structural struts of this invention, sidewalls  32  and  34  are parallel, mirror images that are substantially perpendicular to ceiling  30 . 
     Also, in this embodiment of the elongated structural struts of this invention, sidewall  32  includes flat wall portion  33  and hook  36 . Flat wall portion  33  begins at a longitudinal edge of ceiling  30  and extends downward. Hook  36  is formed by the lower portion of sidewall  32 , below and continuous with flat wall portion  33 . 
     Similarly, in this embodiment of the elongated structural struts of the invention, sidewall  34  includes flat wall portion  35  and hook  38 . Flat wall portion  35  begins at the other longitudinal edge of ceiling  30  and extends downward. Hook  38  is formed by the lower portion of sidewall  34 , below and continuous with flat wall portion  35 . 
     Ceiling  30  and sidewalls  32  and  34  define lower chamber  54  with opening  56  defined by hooks  36  and  38  (and the innermost ends of flanges  16  and  18 ). 
     The function of hooks  36  and  38  is to provide portions of sidewalls  32  and  34  that extend inwardly from flat wall portions  33  and  35 , respectively, without closing opening  56 . In use, hooks  36  and  38  can engage or otherwise support other structural members, room and building accessories, apparatus to support room and building accessories, etc. In other embodiments of the elongated structural struts of this invention, the lower portions of the sidewalls can have any shape that results in those portions extending inwardly, without closing the opening between the sidewalls. As stated above, one advantage of hooks  36  and  38  over other “shapes” is that hooks  36  and  38  provide a “loop” to firmly engage a rod, flange, etc. that fits into and is received in the “loop.” 
     Also, the sidewalls of the lower portions of other embodiments of the elongated structural struts of this invention do not have to include flat wall portions, such as flat wall portions  33  and  35 . Rather, the sidewalls can have any configuration and/or shape that results in the sidewalls partially defining a chamber between them. 
     As can be determined from  FIGS. 1 and 2 , in this embodiment of the elongated structural struts of the invention, flat wall portions  23  and  33  of sidewalls  22  and  32  are in substantially the same planes and flat wall portions  25  and  35  of sidewalls  24  and  34  are in substantially the same planes. 
     Flange  16  is attached to hook  36  of sidewall  32  by spot welds, such as spot welds  40 , as shown in  FIG. 2 . Flange  16  is oriented substantially perpendicular to flat wall portion  33  of sidewall  32  in the lateral direction and abuts sidewall  32  at the apex of hook  36 . Flange  16  extends laterally beyond and outside of flat wall portion  33  to provide a surface to support other structural members, room and building accessories, etc. The inner surface of flange  16  is in substantially the same plane as the innermost surface of hook  36 . 
     Similarly, flange  18  is attached to hook  38  of sidewall  34  by spot welds  42 , as shown in  FIGS. 1 and 2 . Flange  18  is oriented substantially perpendicular to flat wall portion  35  of sidewall  34  in the lateral direction and abuts sidewall  34  at the apex of hook  38 . Flange  18  extends laterally beyond and outside of flat wall portion  35  to provide a surface to support other structural members, room and building accessories, etc. The inner surface of flange  18  is in substantially the same plane as the innermost surface of hook  38 . 
     While, in this embodiment of the elongated structural struts of this invention, flanges  16  and  18  are elongated bars attached to lower portion  14 , in other embodiments of the elongated structural struts of this invention, flanges  16  and  18  can be integral with lower portion  14 . Also, in yet other embodiments of the elongated structural struts of this invention, flanges  16  and  18  can have a shape other than an elongated bar, as long as they include a portion that can support other structural members and room and building accessories such as light fixtures, HVAC conduits, piping, etc. 
     As can be determined from  FIGS. 1 and 2 , each of upper portion  12 , lower portion  14  and flanges  16  and  18  has a longitudinal axis that is substantially parallel to the longitudinal axis of elongated structural strut  10 . 
     As stated,  FIG. 3  illustrates four of the elongated structural strut for ceiling grids illustrated in  FIGS. 1 and 2  and described above, elongated structural struts  10   a ,  10   b ,  10   c  and  10   d , connected at one of their ends to form intersecting and perpendicular rows of the struts. Elongated structural struts  10   a ,  10   b ,  10   c  and  10   d  are joined by connector assembly  44 , which includes wing member  46  and U-shaped connector  48 . 
     Wing member  46  is a flat member that includes center portion  59  and integral wings  58   a ,  58   b ,  58   c  and  58   d  that extend outward from center portion  59 . Wings  58   a ,  58   b ,  58   c  and  58   d  are oriented at 90° from each other. Wings  58   a ,  58   b ,  58   c  and  58   d  are affixed to elongated structural struts  10   a ,  10   b ,  10   c  and  10   d , respectively, as described below. 
     U-shaped connector  48  is a continuous member formed of top portion  60 , sidewalls  62  and  64  and mating flanges  66  and  68 . Mating flange  66  mates with wing  58   d  and is affixed to elongated structural strut  10   d  with wing  58   d . Mating flange  68  mates with wing  58   b  and is affixed to elongated structural strut  10   b  with wing  58   b . 
     While, in this embodiment of the invention, wing member  46  and U-shaped connector  48  are separate components, in other embodiments, they can be integral. Also, in other embodiments, the connector assembly can be of any shape or configuration as long as it has surfaces that can be attached to four elongated structural struts that are arranged to form intersecting and perpendicular rows of the struts and a surface that enables it to be connected to a ceiling rod assembly, as described below, or to any other apparatus employed to attach and suspend the connector assembly to and from a ceiling. 
     In this embodiment of the invention, wing  58   a  is attached to elongated structural strut  10   a  by bolt  70   a  and retaining block  72   a , wing  58   b  and mating flange  68  are attached to elongated structural strut  10   b  by bolt  70   b  and retaining block  72   b , wing  58   c  is attached to elongated structural strut  10   c  by bolt  70   c  and retaining block  72   c , and wing  58   d  and mating flange  66  are attached to elongated structural strut  10   d  by bolt  70   d  and retaining block  72   d , respectively. Bolts  70   a ,  70   b ,  70   c  and  70   d  have external threads that threadedly engage internal threads of holes in retaining blocks  72   a ,  72   b ,  72   c  and  72   d , respectively. The shafts of bolts  70   a ,  70   b ,  70   c  and  70   d  are received in holes in wings  58   a ,  58   b ,  58   c  and  58   d , respectively. The shafts of bolts  70   b  and  70   d  are also received in holes in mating flanges  68  and  66 , respectively. Retaining blocks  72   a ,  72   b ,  72   c  and  72   d  have a width less than, but a length greater than, the width of openings  52   a ,  52   b ,  52   c  and  52   d  of upper portions  12   a ,  12   b ,  12   c  and  12   d  of elongated structural struts  10   a ,  10   b ,  10   c  and  10   d , respectively, for reasons described below. 
     Connector assembly  44  can be attached to elongated structural struts  10   a ,  10   b ,  10   c  and  10   d  in at least the following ways. 
     One way is illustrated, in part, by  FIGS. 9A-9D . First, before connector assembly  44  is placed on elongated structural struts  10   a ,  10   b ,  10   c  and  10   d , bolt  70   a  and retaining block  72   a  are loosely connected to wing  58   a , bolt  70   b  and retaining block  72   b  are loosely connected to wing  58   b  and mating flange  68 , bolt  70   c  and retaining block  72   c  are loosely connected to wing  58   c , and bolt  70   d  and retaining block  72   d  are loosely connected to wing  58   d  and mating flange  66  (the loose connection of bolt  70   b  and retaining block  72   b  to wing  58   b  and mating flange  68  is illustrated in  FIG. 9A ). Connector assembly  44  is then positioned above elongated structural struts  10   a ,  10   b ,  10   c  and  10   d , with wing  58   a  located above elongated structural strut  10 , wing  58   b  and mating flange  68  located above elongated structural strut  10   b , wing  58   c  located above elongated structural strut  10   c , and wing  58   d  and mating flange  66  located above elongated structural strut  10   d . Alternatively, if connector assembly  44  is already installed, elongated structural struts  10   a ,  10   b ,  10   c  and  10   d  are positioned below connector assembly  44 , with elongated structural strut  10   a  located below wing  58   a , elongated structural strut  10   b  below wing  58   b  and mating flange  68 , elongated structural strut  10   c  below wing  58   c , and elongated structural strut  10   d  below wing  58   d  and mating flange  66 . 
     Either way, retaining blocks  72   a ,  72   b ,  72   c  and  72   d  are positioned relative to openings  52   a ,  52   b ,  52   c  and  52   d  such that the widths of retaining blocks  72   a ,  72   b ,  72   c  and  72   d  are substantially aligned with openings  52   a ,  52   b ,  52   c  and  52   d , so that retaining blocks  72   a ,  72   b ,  72   c  and  72   d  can fit through openings  52   a ,  52   b ,  52   c  and  52   d , respectively. The alignment of retaining block  72   b  with opening  52   b  is illustrated in  FIG. 9A . 
     Next, connector assembly  44  is lowered, or elongated structural struts  10   a ,  10   b ,  10   c  and  10   d  are raised (if connector assembly  44  is already installed), until retaining blocks  72   a ,  72   b ,  72   c  and  72   d  pass through openings  52   a ,  52   b ,  52   c  and  52   d  and are received in chambers  50   a ,  50   b ,  50   c  and  50   d , respectively. As noted above, the width of retaining blocks  72   a ,  72   b ,  72   c  and  72   d  is less than the widths of openings  52   a ,  52   b ,  52   c  and  52   d , respectively. The passing of retaining block  72   b  through opening  52   b  into chamber  50   b  is illustrated in  FIG. 9B . 
     Once the top surfaces of retaining blocks  72   a ,  72   b ,  72   c  and  72   d  pass below the free end of hooks  26   a  and  28   a , hooks  26   b  and  28   b , hooks  26   c  and  28   c , and hooks  26   d  and  28   d , respectively, retaining blocks  72   a ,  72   b ,  72   c  and  72   d  are rotated such that portions of retaining blocks  72   a ,  72   b ,  72   c  and  72   d  overlap the free ends of those hooks. The rotation of retaining block  72   b  is illustrated in  FIG. 9C . 
     Bolts  70   a ,  70   b ,  70   c  and  70   d  are then tightened until retaining blocks  72   a ,  72   b ,  72   c  and  72   d  firmly engage the free ends of hooks  26   a  and  28   a , hooks  26   b  and  28   b , hooks  26   c  and  28   c , and hooks  26   d  and  28   d , respectively. The tightening of bolt  70   b  and engagement of retaining block  72   b  with the free ends of hooks  26   b  and  28   b  are illustrated in  FIG. 9D . 
     Another way of connecting connector assembly  44  to elongated structural struts  10   a ,  10   b ,  10   c  and  10   d , i.e., connecting wing  58   a  to elongated structural strut  10   a  by bolt  70   a  and retaining block  72   a , wing  58   b  and mating flange  68  to elongated structural strut  10   b  by bolt  70   b  and retaining block  72   b , wing  58   a  to elongated structural strut  10   c  by bolt  70   c  and retaining block  72   c , and wing  58   d  and mating flange  66  to elongated structural strut  10   d  by bolt  70   d  and retaining block  72   d , is as follows. Connector assembly  44  is placed on elongated structural struts  10   a ,  10   b ,  10   c  and  10   d  such that wing  58   a  is above elongated structural strut  10   a , wing  58   b  and mating flange  68  are above elongated structural strut  10   b , wing  58   c  is above elongated structural strut  10   c , and wing  58   d  and mating flange  66  are above elongated structural strut  10   d , but without bolts  70   a ,  70   b ,  70   c  and  70   d  and retaining blocks  72   a ,  72   b ,  72   c  and  72   d  attached thereto. Alternatively, if connector assembly  44  is already installed, elongated structural struts  10   a ,  10   b ,  10   c  and  10   d  are positioned below connector assembly  44  such that elongated structural strut  10   a  is below wing  58   a , elongated structural strut  10   b  is below wing  58   b  and mating flange  68 , elongated structural strut  10   a  is below wing  58   a , and elongated structural strut  10   d  is below wing  58   d  and mating flange  66 , but without bolts  70   a ,  70   b ,  70   c  and  70   d  and retaining blocks  72   a ,  72   b ,  72   c  and  72   d  attached thereto. 
     Once connector assembly  44  and elongated structural struts  10   a ,  10   b ,  10   c  and  10   d  are in the proper relative position, bolts  70   a ,  70   b ,  70   c  and  70   d  are inserted through the holes in wing  58   a , wing  58   b  and mating flange  68 , wing  58   c , and wing  58   d  and mating flange  66 , respectively. The lower ends of bolts  70   a ,  70   b ,  70   c  and  70   d  extend into upper chambers  50   a ,  50   b ,  50   c  and  50   d  through openings  52   a ,  52   b ,  52   c  and  52   d , respectively. Retaining blocks  72   a ,  72   b ,  72   c  and  72   d  are then positioned on the threaded ends of bolts  70   a ,  70   b ,  70   c  and  70   d , respectively, such that areas of retaining blocks  72   a ,  72   b ,  72   c  and  72   d  overlap with hooks  26   a  and  28   a , hooks  26   b  and  28   b , hooks  26   c  and  28   c , and hooks  26   d  and  28   d , respectively. Bolts  70   a ,  70   b ,  70   c  and  70   d  are then tightened until retaining blocks  72   a ,  72   b ,  72   c  and  72   d  firmly engage hooks  26   a  and  28   a , hooks  26   b  and  28   b , hooks  26   c  and  28   c , and hooks  26   d  and  28   d , respectively. 
     Yet another way of connecting connector assembly  44  to elongated structural struts  10   a ,  10   b ,  10   c  and  10   d , i.e., connecting wing  58   a  to elongated structural strut  10   a  by bolt  70   a  and retaining block  72   a , wing  58   b  and mating flange  68  to elongated structural strut  10   b  by bolt  70   b  and retaining block  72   b , wing  58   c  to elongated structural strut  10   c  by bolt  70   c  and retaining block  72   c , and wing  58   d  and mating flange  66  to elongated structural strut  10   d  by bolt  70   d  and retaining block  72   d , is as follows. Retaining blocks  72   a ,  72   b ,  72   c  and  72   d  are positioned in upper chambers  50   a ,  50   b ,  50   c  and  50   d  such that portions of retaining blocks  72   a ,  72   b ,  72   c  and  72   d  overlap with hooks  26   a  and  28   a , hooks  26   b  and  28   b , hooks  26   c  and  28   c  and hooks  26   d  and  28   d , respectively. Springs, such as springs  57   a ,  57   b ,  57   c  and  57   d  in  FIG. 3 , are positioned in upper chambers  50   a ,  50   b ,  50   c  and  50   d  between retaining blocks  72   a ,  72   b ,  72   c  and  72   d  and floors  20   a ,  20   b ,  20   c  and  20   d  of upper portions  12   a ,  12   b ,  12   c  and  12   d , respectively, to “push” retaining blocks  72   a ,  72   b ,  72   c  and  72   d  in fixed positions against the free ends of hooks  26   a  and  28   a , hooks  26   b  and  28   b , hooks  26   c  and  28   c  and hooks  26   d  and  28   d , respectively. Bolts  70   a ,  70   b ,  70   c  and  70   d  are then inserted through the holes in wing  46   a , wing  46   b  and mating portion  68 , wing  46   c  and wing  46   d  and mating portion  66 , and tightened to firmly engage retaining blocks  72   a ,  72   b ,  72   c  and 72 d  against the free ends of hooks  26   a  and  28   a , hooks  26   b  and  28   b , hooks  26   c  and  28   c , and hooks  26   d  and  28   d , respectively. 
     Connector assembly  44  can be attached to and suspended from the structure comprising a ceiling of a room or other building area, such as a concrete slab, as follows. One end of a ceiling rod assembly, such as ceiling rod assembly  61  in  FIG. 3 , is attached to the ceiling structure. The other end of ceiling rod assembly  61  is attached to top portion  60  of U-shaped connector  48 . 
     As stated,  FIG. 4  illustrates three of the elongated structural strut for ceiling grids illustrated in  FIG. 1 and 2  and described above, elongated structural struts  10 ′,  10 ″ and  10 ′″, joined at one of their ends to form a T-intersection of a ceiling grid (elongated structural strut  10 ′″ is not shown in  FIG. 4 , but is behind and axially in line with elongated structural strut  10 ″). Elongated structural struts  10 ′,  10 ″ and  10 ′″ are joined by connector assembly  44 ′, which includes T-shaped member  46 ′ and U-shaped connector  48 ′. 
     T-shaped member  46 ′ is a flat member that includes center portion  59 ′ (not shown) and integral wings  58 ′,  58 ″ and  58 ′″ that (1) extend outward from center portion  59 ′ and (2) are oriented 90° to each other to form a “T” (wing  58 ′″ is not shown in  FIG. 4 , but is behind and in the same planes as wing  58 ″). 
     The same as U-shaped connector  48 , U-shaped connector  48 ′ is a continuous member formed of top portion  60 ′, sidewalls  62 ′ and  64 ′ and mating flanges  66 ′ and  68 ′ (sidewall  64 ′ and mating flange  68 ′ are not shown in  FIG. 4 ). 
     While in this embodiment of the invention, T-shaped member  46 ′ and U-shaped connector  48 ′ are separate components, in other embodiments, they can be integral. Also, in other embodiments, the connector assembly can be of any shape or configuration as long as it has surfaces that can be attached to the three elongated structural struts forming the T-intersection and a surface that enables it to be connected to a ceiling rod assembly, or to any other apparatus employed to attach and suspend the ceiling grid to and from a ceiling. 
     Connector assembly  44 ′ can be attached to elongated structural struts  10 ′,  10 ″ and  10 ′″ in the same ways that connector assembly  44  can be attached to elongated structural struts  10   a ,  10   b ,  10   c  and  10   d . Specifically, wing  58 ′ is attached to elongated structural strut  10 ′ by bolt  70 ′ and retaining block  72 ′, wing  58 ″ and mating flange  66 ′ are attached to elongated structural strut  10 ″ by bolt  70 ″ and retaining block  72 ″, and wing  58 ′″ and mating flange  68 ′ are attached to elongated structural strut  10 ′″ by bolt  70 ′″ and retaining block  72 ′″ (bolt  70 ′″ and retaining block  72 ′″ are not shown in  FIG. 4 ). Like bolts  70   a ,  70   b ,  70   c  and  70   d  and retaining blocks  72   a ,  72   b ,  72   c  and  72   d , bolts  70 ′,  70 ″ and  70 ′″ have external threads that threadedly engage internal threads of holes in retaining blocks  72 ′,  72 ″ and  72 ′″, respectively. Also, like retaining blocks  72   a ,  72   b ,  72   c  and  72   d , retaining blocks  72 ′,  72 ″ and  72 ′″ have a width less than, but a length greater than, the width of openings  52 ′,  52 ″ and  52 ′″ of upper portions  12 ′,  12 ″ and  12 ′″ of elongated structural struts  10 ′,  10 ″ and  10 ′″, respectively. 
     The end result is that retaining blocks  72 ′,  72 ″ and  72 ′″ are received in upper chambers  50 ′,  50 ″ and  50 ′″ of upper portions  12 ′,  12 ″ and  12 ′″ of elongated structural struts  10 ′,  10 ″ and  10 ′″ and firmly engage the free ends of hooks  26 ′ and  28 ′, hooks  26 ″ and  28 ″, and hooks  26 ′″ and  28 ′″, respectively. 
     In this embodiment, when elongated structural struts  10 ′ and  10 ″ are joined by connector assembly  44 ′, flanges  16 ′ (not shown) and  18 ′ abut flange  18 ″, as shown in  FIG. 4 . 
     Connector assembly  44 ′ can be attached to and suspended from ceiling structure by ceiling rod assembly  61 ′ in the same manner that connector assembly  44  can be attached to and suspended from ceiling structure by ceiling rod assembly  61 . 
     In other embodiments, a connector assembly other than connector assembly  44 ′ can be used to join elongated structural struts  10 ′,  10 ″ and  10 ′″ in the configuration of a T-intersection. 
     As stated,  FIG. 10  illustrates two of the elongated structural strut for ceiling grids illustrated in  FIGS. 1 and 2  and described above, elongated structural struts  10   x  and  10   y , joined at one of their ends to form a corner of a ceiling grid. Elongated structural struts  10   x  and  10   y  are joined by L-shaped member  46   x . 
     In this embodiment, L-shaped member  46   x  is a flat member that includes center portion  59   x  and integral wings  58   x  and  58   y  that (1) extend outward from center portion  59   x  and (2) are oriented 90° to each other to form an “L.” In other embodiments, the member that joins the elongated structural struts can be of any shape or configuration as long as it has surfaces that can be attached to the two elongated structural struts forming the grid corner. 
     L-shaped member  46   x  can be attached to elongated structural struts  10   x  and  10   y  in the same ways that connector assembly  44  can be attached to elongated structural struts  10   a ,  10   b ,  10   c  and  10   d . Specifically, wing  58   x  is attached to elongated structural strut  10   x  by bolt  70   x  and retaining block  72   x  and wing  58   y  is attached to elongated structural strut  10   y  by bolt  70   y  and retaining block  72   y . Like bolts  70   a ,  70   b ,  70   c  and  70   d  and retaining blocks  72   a ,  72   b ,  72   c  and  72   d , bolts  70   x  and  70   y  have external threads that threadedly engage internal holes in retaining blocks  72   x  and  72   y , respectively. Also, like retaining blocks  72   a ,  72   b ,  72   c  and  72   d , retaining blocks  72   x  and  72   y  have a width less than, but a length greater than, the width of openings  52   x  and  52   y  of upper portions  12   x  and  12   y  of elongated structural struts  10   x  and  10   y , respectively. 
     The end result is that retaining blocks  72   x  and  72   y  are received in upper chambers  50   x  and  50   y  of upper portions  12   x  and  12   y  of elongated structural struts  10   x  and  10   y  and firmly engage the free ends of hooks  26   x  and  28   x  and hooks  26   y  and  28   y , respectively. 
     As stated,  FIGS. 5 and 6  illustrate one embodiment of a non-structural elongated member, non-structural elongated member  74 , which can be used in a ceiling grid with the elongated structural struts of this invention. 
     Non-structural elongated member  74  includes upper portion  76 , web  78  and flange portion  80 . While, in this embodiment of the invention, upper portion  76 , web  78  and flange portion  80  are integral, in other embodiments, they can be comprised of two or more components, welded or otherwise fastened together. 
     Upper portion  76  includes floor  81  and spaced and parallel sidewalls  82  and  84  that extend upward from the two longitudinal edges of floor  81  to form a U-shape with floor  81 . Sidewall  82  includes threads  86  on its inner surface, and sidewall  84  includes threads  88  on its inner surface. Floor  81  and sidewalls  82  and  84  form or define threaded slot  77 . Threads  86  and  88  are offset one half turn vertically from each other, as shown in  FIG. 6 . That is, each peak of thread  86  is diametrically opposed by a valley of thread  88 , and each valley of thread  86  is diametrically opposed by a peak of thread  88 . 
     Flange portion  80  is oriented substantially perpendicular to web  78 . The bottom surface of flange portion  80  is what is visible to occupants of the room or building space that includes a ceiling grid with one or more non-structural elongated members  74 . 
     As stated,  FIG. 7  illustrates a pair of the non-structural elongated member of  FIGS. 5 and 6 , non-structural elongated members  74 ′ and  74 ″, attached on opposite sides of elongated structural strut  10 , to form intersecting and perpendicular rows of the elongated structural struts and the non-structural elongated members. Specifically, non-structural elongated member  74 ′ is attached to one side of elongated structural strut  10  by connector  90 , and non-structural elongated member  74 ″ is attached to the opposite side of elongated structural strut  10  by connector  92 . 
     In this embodiment, connectors  90  and  92  are L-shaped. The bottom arms of connectors  90  and  92  are attached to non-structural elongated members  74 ′ and  74 ″ by bolts  94  and  96  that threadedly engage threaded slots  77 ′ and  77 ″ of non-structural elongated members  74 ′ and  74 ″, respectively. The upper arms of L-shaped connectors  90  and  92  are attached to sidewalls  22  and  24  of upper portion  12  of elongated structural strut  10  by screws  98  and  100 , respectively. 
     In this embodiment, the ends of flange portions  80 ′ and  80 ″ are recessed from the ends of upper portions  76 ′ and  76 ″ and webs  78 ′ and  78 ″, as shown in  FIGS. 5 and 7 , so that the bottom surfaces of flange portions  80 ′ and  80 ″ of non-structural elongated members  74 ′ and  74 ″ and of flanges  16  and  18  of elongated structural strut  10  form a substantially flat surface. 
       FIG. 7  illustrates one way of connecting the elongated structural struts and the non-structural elongated members of this invention to form intersecting and perpendicular rows of those struts and members. In other embodiments, the elongated structural struts and non-structural elongated members can be attached using different methods/apparatus that are sufficient to maintain the elongated structural struts and the non-structural elongated members in the desired relative positions. 
     As stated,  FIG. 8  discloses a partial ceiling grid comprised of a plurality of elongated structural struts  10  and non-structural elongated members  74 . The grid is attached to and suspended from a ceiling by a plurality of ceiling rod assemblies  61 . 
     What has been described and illustrated herein are preferred embodiments of the invention with some variations. The terms, descriptions and figures herein are intended to be for illustration only and are not meant as limitations. Those skilled in the art will recognize that many variations are possible within the scope of the invention, as defined by the following claims.