Abstract:
Formwork for erecting a crown on a top end of a structural concrete column of a highway bridge is supported by a pair of vertically positioned elongated jack-screws. Lower ends of these jack-screws are threaded respectively into adjusting nuts seated on outer ends of respective horizontal arms of a pair of brackets. Each bracket includes an upright support member. These members are attached respectively to opposite sides of the column. The vertical location of the formwork attached to an upper end of a jack-screw may be adjusted up or down by selective rotation of the adjusting nut into which that jackscrew is assembled.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of Invention 
   This invention relates generally to support systems for concrete formwork and more particularly to a support system and related bracket for formwork for casing a crown on a top end of a concrete structural column of a highway bridge. 
   2. Prior Art 
   As is well known, use of concrete as a building material concurrently requires formwork to hold and shape just poured concrete until that concrete is sufficiently cured to allow removal of the formwork. Until formwork removal, the curing concrete and formwork must be secured by a formwork support system. 
   One early concrete formwork support system is disclosed in U.S. Pat. No. 3,504,879. This system includes a bracket attachable to a side to a structural column of a building under construction to support the formwork needed for casting an above floor of the building. This bracket has a vertical tubular body formed with internal threading for disposition of a vertically positioned jack screw. An upper end of the jack-screw has an internal bore to rotatably receive a pin attached to a bottom side of a horizontally positioned, channel-shaped support head. Extending horizontally inward from the body is a pair of spaced apart upper and lower projections. These projections include respective passages to receive a pair of mounting bolts that extend outward from the column. Attached to an outer end of the upper projection is a horizontally positioned roller. 
   For use, the bracket is attached to the column using the mounting bolts. A bottom beam of the formwork then is positioned in the support head, and the formwork raised to a desired location by rotating the jack-screw. When the concrete poured onto the formwork has set, the formwork may be lowered by rotating the jack-screw in a reverse direction until the formwork beam rests on the bracket roller. The formwork then may be rolled out from under the now semi- cured concrete floor above. 
   A further bracket for a concrete formwork support system is disclosed in U.S. Pat. No. 3,863,877. This bracket comprises a column-attached support part and a movable jack part. The jack part then includes a base plate that operatively carrying a vertically positioned jack- screw. On an upper end of the jack-screw is a frame that supports a pair of rollers. Each roller has a cylindrical traction section and connecting spool-shaped flange. Attached to respective side edges of the jack part base plate is pair of inward facing channels. Slidably disposed in these channels are respective side edges of a pair of spaced apart shelf arms of the bracket support part. The arms in turn are attached to respective top edges of a pair of triangular shaped gusset plates that then are attached to a vertically positioned backing plate. This backing plate is prepared to be attached to a side of a structural column of a building under construction. 
   A laterally adjustable bracket for shoring concrete formwork is set out in U.S. Pat. No. 3,967,806. This bracket includes a horizontally positioned, angle-shaped arm having an inner end joined to a vertically positioned end plate attachable to a side of a concrete column of a building under construction. This bracket further includes a vertically positioned plate member formed with an inverted L-shaped opening for disposition of the angle-shape arm. Attached to an outer side of the plate are spaced apart, upper and lower projections of a jack-screw unit having a vertical cylindrical portion to operatively receive a jack-screw. A support head is attached to a top end of the jack-screw. On an outer end of the upper projection is a pair of spaced apart lugs to hold ends of a shaft for a horizontally positioned roller. The plate member and attached jack- screw unit may slide laterally along the bracket angle arm until the support head is properly aligned with the formwork above. The location of the plate member and jack-screw unit then are secured in place by inward threading of a fastener carried by one of a pair of spaced apart ears on the plate member. These ears are positioned on respective sides of a vertical leg of the angle arm. 
   Other examples of formwork support systems are disclosed in U.S. Pat. Nos. 3,797,794; 3,815,858; 3,900,179; and 4,768,939. 
   SUMMARY OF THE INVENTION 
   A support system of this invention for supporting formwork needed for forming a crown on a top of a concrete column of a highway bridge includes a pair of brackets attached respectively to opposite sides of the column. Each bracket includes an upright having a pair of upper openings for selective disposition of an end of a threaded rod that extends through a tube embedded in the column. Nuts threaded onto the rod ends then compressively secure the brackets to the column. Each bracket further includes an outward extending arm supported in part by an angularly positioned pair of braces that extends from a lower end of the bracket upright to an outer end of the bracket arm. Carried on the outer end of the arm is an adjusting nut to receive a threaded lower end of a vertically positioned jack-screw. An upper end of each jack-screw operatively connects to the formwork above to hold the crown formwork in place until concrete contained by this formwork is sufficiently cured to permit removal of the formwork and supporting structure. 
   The support system and related brackets of the invention provide several advantages over like support systems known or in use. 
   A first advantage is that system only requires two brackets to support the formwork above. 
   A second advantage is that the lateral location of either bracket as attached to a column may be adjusted depending on which pair of openings is selected for disposition of the threaded rod carried by the column. The lateral position of the point for attaching the jack-screw to the formwork also is considered when selecting the bracket opening pair for insertion. Once selected, then only one nut threaded onto the rod end is required to secure that bracket to that side the column. Note that the threaded rod and brackets are reusable. 
   A last advantage is that the bracket structure may be fabricated using ready available steel structural shapes. By using selective shaped steel members, the brackets may be easily configured to support substantial weight. 

   
     DESCRIPTION OF THE DRAWING FIGURES 
       FIG. 1  is a perspective view of the support system of this invention. 
       FIG. 2  is a side elevation view of a bracket of the system of  FIG. 1 . 
       FIG. 3  is a front elevation view of the bracket of  FIG. 2 . 
       FIG. 4  is a plan view of the bracket of  FIG. 2 . 
       FIG. 5  is a cross sectional view of the bracket as seen generally along the line  5 — 5  of  FIG. 2 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A system for supporting formwork needed to form of a crown on a top end of a concrete column of a highway bridge is shown generally in  FIG. 1  and designated  10 . The system  10  includes a pair of brackets  12 ,  14  attached to opposite sides  16 ,  18  of a concrete column  20 . Since the structure of each bracket  12 ,  14  is the same, only the bracket  12  is described in detail. Like reference numbers are used to identify like structure. 
   The bracket  12  is defined by an upright  22  having an inner and outer wall  24 ,  26  and sidewalls  28 . As best seen in  FIG. 5 , each sidewall  28  is inwardly offset from side edges  30  of the inner and outer walls  24 ,  26 . Additionally, an inner partition  32  positioned parallel to and between the sidewalls  28  connects the inner and outer walls  24 ,  26 . As seen in  FIGS. 2 and 3 , bottom ends  34  of the inner wall  24  and the partition  32  extend below bottom ends  36  of the outer wall  26  and the sidewalls  28 . A pair of horizontally spaced apart oblong-shaped mounting holes is formed in the inner wall  24  on either side of the partition  32  just above the inner wall bottom end  34 . 
   In an upper portion  40  of the inner wall  24  and the outer wall  26  are two pairs of horizontally spaced apart and horizontally aligned openings  42 . Extending between the inner and outer walls  24 ,  26  in alignment with each opening pair is a tube  44 . An inside diameter of each tube  44  is greater than a diameter of the openings  42 . Attached to top ends  46  of the inner and outer walls  24 ,  26  and sidewalls  28  is a top plate  48 . 
   Attached to the upright outer wall  26  is an inner end  49  of an arm  50 . This arm  50  extends horizontally outward and is defined by two spaced apart channel members  52 . Attached to outer ends  54  of the channel members  52  is an end plate  56 . A jack-screw plate  58  then is attached to top surfaces  60  of top flanges  62  of the arm channel members  52  adjacent to the end plate  56 . 
   To enhance the connection between the arm inner end  49  and the upright outer wall  26 , a pair of reinforcing plates  66  is attached respectively to side edges  68  of the channel member top flanges  62  and bottom flanges  70  and to the upright outer wall  26 . Note that top and bottom edges  72  of each reinforcing plate  66  extend respectively above and below the channel member top flange  62  and bottom flange  70 . Additionally, the fixed position of the arm  50  is enhanced by a pair of spaced apart, angularly positioned tubular braces  76 . Upper ends  78  of these braces  76  are attached one each to a bottom surface  80  of each channel member bottom flange  70  while lower ends  82  of the braces  76  are attached to the upright outer wall  26 . Carried between the channel members  52  in alignment with an opening  84  in the jack-screw plate  58  is a vertically positioned jack-screw tube  88 . Note that a bottom end  90  of the tube  88  extends below the bottom surface  80  of the channel member bottom flanges  70 . 
   For use as seen in  FIG. 1 , the brackets  12 ,  14  are positioned on respective sides  16 ,  18  of the column  20 . During forming of the column  20 , a tube  92  has been embedded in the column  20  for disposition of a threaded rod  93 . Outer ends  94  of the rod  93  then extend beyond the column sides  16 ,  18 . One each of the rod ends  94  is inserted into one of the pair of aligned openings  42  in each bracket upright  22 . Selection of which pair of aligned openings  42  to use for rod end insertion depends on the desired location of each bracket  12 ,  14  since the tube  92  may not be centered in the column  20 . Mechanically positioning of the brackets  12 ,  14  is facilitated by operative use of a lifting lug  96  attached to the top plate  48  on each bracket upright  22 . This lifting lug  96  is positioned to vertically align with a center of gravity of each bracket  12 ,  14 . 
   Once in place, the brackets  12 ,  14  are compressively secured to the column  20  by nuts  98  threaded on the respective ends  94  of the rod  93 . Additionally, the bottom end  34  of each bracket inner wall  24  is secured to the column  20  by an anchor bolt (not shown) inserted into the column  20  through one of the openings  38 . Next, a bottom end  100  of a jack-screw  102  is inserted through in each jack-screw plate opening  84  so that this bottom end  100  fits into the respective tube  88  located below the jack-screw plate  58 . Each jack-screw  102  then is held vertically in place by a jack-screw nut  104  assembled on that jack-screw  102  as the nut  104  seats of the bracket jack-screw plate  58 . The vertical location of a top end (not shown) of each jack-screw  102  may be adjusted by rotation of the nut  104  for selective attachment to the column crown formwork above (not shown). Once attached, the system  10  may support the formwork and uncured concrete poured into the formwork for casing the crown. 
   The system  10 , as its use is described above, supports working loads of 200,000 pounds with a safety factor of 500,000 pounds. To meet this requirement the brackets  12 ,  14  are made using selective structural steel shapes. For example, the inner and outer walls  24 ,  26  and the inner partition  32  of each bracket upright  22  are integrally formed as flanges and a web of a 10 in. structural steel H-beam  106  having a weight of 77 pounds/linear foot. The bracket sidewalls  28  then are made from ½ in. thick steel plate. The arm channel member  52  are 6 in. structural steel channels having a weight of 13 pounds/linear foot. Lastly, the braces  76  are made from 2 in.×4 in.× 3/16 in. thick steel tubes. These structural members  106 ,  28 ,  32 , and  76  then are welded together. 
   While an embodiment, uses, and advantages of this invention have been shown and discussed, it should be understood that this invention is limited only by the scope of the claims. Those skilled in the art will appreciate that various modifications and changes may be made without departing from the scope and spirit of the invention, and these modifications and changes may result in farther uses and advantages.