Seismic resistant grid ceiling suspension system and method of installation

Abstract

Ceiling suspension system including a plurality of rigid, elongated seismic joists interposed between opposing walls of a room, spaced selected distances apart along a horizontal support plane, and hangers suspended from the respective joists to support a grid from the respective lower ends thereof.

I claim: 
     
         1 . A seismic vertical support suspension system for suspending a ceiling grid from the opposite walls of a room or corridor spaced a predetermined distance apart comprising:
 a suspension system mounted to the walls including a plurality of transversely projecting seismic joists interposed between the walls to maintain them spaced the predetermined distance apart and spaced predetermined distances apart along a longitudinal horizontal plane and including respective opposite ends abutting the walls;   fastener devices anchoring the opposite ends of the joists to the respective walls;   a plurality of substantially rigid lever arms projecting downwardly from the respective joists and connected on their respective lower extremities of the grid to act as hangers; and   the joists and hangers being so constructed and configured as to, upon a seismic event applying forces to the walls tending to shift such walls relative to one another, maintain the walls spaced the predetermined distance apart.   
     
     
         2 . The suspension system of  claim 1  that includes:
 motion-free joints connecting at least some of the hangers to the grid. 
 
     
     
         3 . The suspension system of  claim 1  that includes:
 support joists interposed between the respective seismic joists; and 
 hangers suspended from the respective support joists and connected to the grid. 
 
     
     
         4 . The suspension system as set forth in  claim 1  wherein:
 the hangers include steel angles, flat steel straps, and twisted steel straps. 
 
     
     
         5 . The suspension system as set forth in  claim 1  wherein:
 the hangers include straps. 
 
     
     
         6 . The suspension system as set forth in  claim 5  wherein:
 at least some of the straps are twisted. 
 
     
     
         7 . The suspension system as set forth in  claim 1  wherein:
 the hangers are constructed with a length below the top of the respective seismic joists of between about 5 and 11 inches. 
 
     
     
         8 . The suspension system as set forth in  claim 1  wherein:
 the hangers are spaced apart disposed toward the opposite extremities of the respective joists and cooperate with respective joists and grid to form a relatively unobstructed plenum chamber between such joists and the grid. 
 
     
     
         9 . A system for supporting a ceiling grid from the sidewalls of a longitudinal corridor comprising:
 horizontal C-channels defining tracks mounted along the respective sidewalls and opening toward one another;   tubular seismic joists interposed between the tracks, spaced apart selected distances along the respective tracks and configured with the respective opposite ends nested in the respective tracks;   rigid metal angle straps connected to the respective seismic joists to suspend the grid work therefrom; and   the joists, hangers and grid being configured to form a substantially unobstructed plenum chamber projecting longitudinally over the grid work.   
     
     
         10 . The apparatus of  claim 9  that includes:
 support joists spaced along the tracks, interposed between the seismic joists and formed with respective opposite ends nested in the respective tracks; and 
 hangers connected to the respective support joists to cooperate in supporting the grid. 
 
     
     
         11 . The apparatus of  claim 9  wherein:
 the seismic joists are constructed of metal having a cross-section of at least 3⅝ inches by 3⅝ inches. 
 
     
     
         12 . The apparatus of  claim 9  wherein:
 the hangers are constructed to support the grid work spaced between 6 and 12 inches below the top of their joists. 
 
     
     
         13 . The apparatus of  claim 9 , wherein:
 the hangers are in the form of flat or twisted straps or angles.   
     
     
         14 . The apparatus of  claim 9 , wherein:
 the seismic joists are constructed of box beams.   
     
     
         15 . The apparatus of  claim 9 , wherein:
 the seismic joists are spaced apart a distance of substantially 8 to 16 feet.   
     
     
         16 . The apparatus of  claim 9 , wherein:
 the support joists are spaced apart a distance of 4 feet.   
     
     
         17 . The apparatus of  claim 9 , wherein:
 the tracks are constructed of 3⅝-inch by 1¼-inch, 20-gauge C-channels.   
     
     
         18 . The apparatus of  claim 9 , that includes:
 support joists constructed of C-channels and interposed between the seismic joists; and   hangers suspended from the support channels and connected to the grid.   
     
     
         19 . A method of making and installing a suspension system for supporting a ceiling grid in a horizontal grid plane over a room and including:
 selecting tracks to be positioned in a horizontal support plane spaced above the grid plane mounted to opposite walls of the room;   selecting seismic joists of a length to extend between the tracks when mounted to the respective walls;   selecting rigid lever arms to support the grid and of a length sufficient to, when the joists are positioned in the support plane, position the grid in the grid plane;   configuring and sizing the joists and hangers with a configuration to, when installed, dispose the grid in the grid plane;   at a construction site, mounting the tracks to the respective walls in the support plane;   interposing the joists between the tracks;   fastening the joists to the tracks;   positioning the hanger devices on the respective joists; and   selecting and inserting threaded fasteners through the joists and hangers.   
     
     
         20 . The method of  claim 19  that includes:
 selecting the joists constructed of tubes. 
 
     
     
         21 . The method of  claim 19  that includes:
 selecting the fasteners of self-tapping screws. 
 
     
     
         22 . The method of  claim 19  that includes:
 selecting the joist of a box beam construction.