Variable length beam

Abstract

A beam comprised of sub-components capable of extending or contracting in overall length is provided. The beam consists of a twin-beam structure that provides travel support for two end beam components that are movable with respect to one another to extend or contract the length of the resulting variable length beam. Extension or contraction of the variable length beam can be accomplished manually or, in a preferred embodiment, by means of a screw drive. The variable length beams facilitate the fabrication of reusable, adjustable width deck-forming panels used in the construction of cast-in-place bridge deck slabs supported by parallel structural beams.

1 . In a bridge decking panel comprising a plurality of joists supporting a plurality of stringers, which support a plywood decking, the improvement wherein said bridge decking panel is removable and reusable in its entirety and each of said joists contains a variable length beam comprising twin parallel travel support beams connected to one another, said twin parallel travel support beams supporting two beam components movable longitudinally with respect to one another along said twin parallel travel support beams, to lengthen or shorten said variable length beam. 
     
     
         2 . The bridge decking panel of  claim 1 , wherein said twin parallel travel support beams of said variable length beam are connected to one another at their midpoints through a central stiffener assembly. 
     
     
         3 . The bridge decking panel of  claim 2 , wherein said twin parallel travel support beams of said variable length beam have stop means at each end thereof. 
     
     
         4 . The bridge decking panel of  claim 3 , wherein said two beam components of said variable length beam are modified beam components adapted for longitudinal movement upon said twin parallel travel support beams. 
     
     
         5 . The bridge decking panel of  claim 4 , wherein each of said two beam components of said variable length beam has a pair of oppositely facing side channels which contain said twin parallel travel support beams. 
     
     
         6 . The bridge decking panel of  claim 5 , wherein one end of each pair of said side channels of said variable length beam is closed by an end-plate. 
     
     
         7 . The bridge decking panel of  claim 6 , wherein the opposite end of each pair of said side channels of said variable length beam is open, and wherein modified end-plates close the lateral space between each pair of side channels at said opposite end thereof. 
     
     
         8 . The bridge decking panel of  claim 7 , wherein a side stiffener is attached to each of said side channels of said variable length beam. 
     
     
         9 . The bridge decking panel of  claim 8 , wherein said twin parallel travel support beams of said variable length beam have stop tabs at each end thereof, said stop tabs being adapted to interact with said side stiffeners upon extension of said variable length beam to a predetermined maximum length. 
     
     
         10 . The bridge decking panel of  claim 9 , wherein said central stiffener assembly of said variable length beam contains a horizontally mounted screw drive having a clockwise thread at the proximal end thereof and a counterclockwise thread at the distal end thereof, said proximal end of said screw drive being supported by a modified end-plate having a clockwise-threaded receiving plate and said distal end of said screw drive being supported by a modified end-plate having a counterclockwise-threaded receiving plate, said screw drive having a shaft keeper and a first bevel gear attached thereto, said first bevel gear meshing tangentially with a second bevel gear attached to a vertically mounted shaft. 
     
     
         11 - 13 . (canceled) 
     
     
         14 . A reusable, variable width bridge decking panel comprising a plurality of joists supporting a plurality of stringers, which support a plywood decking, said bridge decking panel being removable and reusable in its entirety, each of said plurality of joists being of variable length. 
     
     
         15 . The bridge decking panel of  claim 14 , wherein each of said plurality of joists contains a variable length beam comprising twin parallel travel support beams connected to one another, said twin parallel travel support beams supporting two beam components movable longitudinally with respect to one another along said twin parallel travel support beams, to lengthen or shorten said plurality of joists. 
     
     
         16 . A variable length beam comprising twin parallel travel support beams connected to one another, said twin parallel travel support beams supporting two beam components movable longitudinally with respect to one another along said twin parallel travel support beams, to lengthen or shorten said variable length beam.