Share |
 
 
 
 
 
Register
 
 
New Blog Posted
Stirrup Bending on Swastik's Latest Automatic Rebar Bending Machine
 
 
 
 

Info

Rebar Fabrication Technical Details

  • Standard Rebar Bend Dimensions :

    To avoid rebar breakage and excessive pressure on the concrete inside a bend, “Building Code Requirements for Reinforced Concrete,” recommends minimum internal bend diameters (measured on the inside of the bar) for various bar sizes:

    Nominal size of bar,
    d
    Minimum radius for
    scheduling, r
    Minimum diameter of
    bending former, M
    Minimum end projection, P
    General (min 5d straight), including links where bend ≥ 150° Links where bend < 150° (min 10d straight)
    mm mm mm mm mm
    6 12 24 110* 110*
    8 16 32 115* 115*
    10 20 40 120* 130
    12 24 48 125* 160
    16 32 64 130 210
    20 70 140 190 290
    25 87 175 240 365
    32 112 224 305 465
    40 140 280 380 580
    50 175 350 475 725
    * The minimum end projections for smaller bars is governed by the practicalities of bending bars.

    Note
    1 : Due to 'spring back' the actual radius of bend will be slightly greater than half the diameter of former.

    Note 2 :
    BS 4449:2005 grade B500A in sizes below 8mm does not conform to BS EN 1992-1.1:2004.








 
Factory bending of rebar is typically performed on computer-controlled equipment programmed to produce bends according to these minimum internal diameters. When rebar is bent on the jobsite, it’s important to use the proper equipment and procedures to avoid damaging the bars. Bending a bar to an internal diameter less than the recommended minimum can produce stresses in the bend zone that can result in bar weakening or failure. Here are a few precautions to take when bending bars in the field.

Don’t use makeshift devices, such as pipes, to bend rebar, It’s difficult to control the internal bend diameter, and a pipe’s sharp edges can notch the bar, weakening it in the bend area.

When using bending equipment, follow recommendations for minimum internal bend diameters for various bar sizes. Don’t try to bend bar sizes or grades that the tool or machine is not designed to handle.

Avoid using impact blows to assist bending. Use of a sledge hammer, for example, can result in over bending of the bar and damage to the rebar surface.

Bending of galvanized rebar can cause flaking of the galvanized coating in the bend area. Repair any damaged coating by applying a zinc-rich paint.

Special precautions are required when bending epoxy-coated bar to prevent coating damage. Bending should only be per formed around a smooth, nonabrasive die to avoid damage to the epoxy coating. If the coating does rub of f in spots, these areas must be repaired. Get approval from the project engineer before attempting to bend epoxy-coated bars.
 
  • Minimum overall depth of various U - bars :
    fy = 500Mpa
    Minimum mandrel diameter:
    For f =16mm Mandrel dia. = 4f
    For f >16mm Mandrel dia. = 7f
 
  • Standard Rebar Bending Shapes (BS 8666:2005) :

    Reinforcing bar technical data
  • Weight (Kg) per m2 in one direction (add both directions for total m2 weight(Kg) :

    *6mm and 50mm are non-preferred sizes
    BAR SIZE SPACING OF BARS (mm)
    (mm) 75 100 125 150 175 200 225 250 275 300
    6* 2.965 2.220 1.776 1.480 1.268 1.110 0.986 0.888 0.807 0.740
    8 5.261 3.946 3.157 2.631 2.255 1.973 1.754 1.578 1.435 1.315
    10 8.220 6.165 4.932 4.110 3.523 3.083 2.740 2.466 2.242 2.055
    12 11.838 8.878 7.103 5.919 5.073 4.439 3.946 3.551 3.228 2.959
    16 21.044 15.783 12.627 10.522 9.019 7.892 7.015 6.313 5.739 5.261
    20 32.882 24.661 19.729 16.441 14.092 12.331 10.961 9.865 8.968 8.220
    25 51.378 38.534 30.827 25.689 22.019 19.267 17.126 15.413 14.012 12.845
    32 84.178 63.133 50.507 42.089 36.076 31.567 28.059 25.253 22.958 21.044
    40 131.528 98.646 78.917 65.764 56.369 49.323 43.843 39.458 35.871 32.882
    50* 205.512 154.134 123.307 102.756 88.077 77.067 68.504 61.654 56.049 51.378
 
  • Sectional area (mm2) of bars per metre width for various c/c (mm)


    *6mm and 50mm are non-preferred sizes
    cc(mm) 6* 8 10 12 16 20 25 32 40 50*
    75 377 671 1050 1510 2680 4190 6550 10700 ------- -------
    100 283 503 785 1130 2010 3140 4910 8040 12600 -------
    125 226 402 628 905 1610 2510 3930 6430 10100 15700
    150 189 35 523 754 1340 2090 3270 5360 8380 13100
    175 162 287 449 646 1150 1800 2810 4600 7180 11200
    200 142 252 393 566 1010 1570 2450 4020 6280 9820
    250 113 201 314 452 804 1260 1960 3220 5030 7850
    300 94.3 168 262 377 670 1050 1640 2680 4190 6540
    350 80.9 144 224 323 575 898 1400 2300 3590 5610
    400 70.8 126 196 283 503 786 1230 2010 3140 4910
    450 62.9 112 174 251 447 698 1090 1790 2790 4360
    500 56.6 101 157 226 402 628 982 1610 2510 3930
 
  • Properties of high yield bars


    *6mm and 50mm are non-preferred sizes
    Size (mm) 6* 8 10 12 16 20 25 32 40 50*
    Dims (max O/A) 7 10 12 14 19 23 29 37 46 58
    Mass(Kg per m) 0.222 0.395 0.616 0.888 1.579 2.466 3.854 6.313 9.864 15.413
    Metres per tonne 4504 2531 1623 1126 633 405 259 158 101 64
 
  • Tolerances on cutting & bending dimensions

    The tolerances for cutting and/or bending dimensions shall be in accordance with the Following table and shall be taken into account when completing the schedule. The end anchorage or the dimension in parentheses in the shape codes specified in the table opposite shall be used to allow for any permissible deviations resulting from cutting and bending.
Cutting and bending tolerances Tolerance (mm)
Cutting of Straight lengths
(incl. reinforcement for subsequent bending)
+25 - 25
Bending   <1000mm +5 -5
  >1000mm to < 2000mm +5 -10
  >2000mm +5 -25
 * Normally all cutting and bending machines provide accuracy for cutting is 0.5 to 1.00 mm    and for bending is 0.5° to 1° degree.
*Normally all cutting & bending machines provide accuracy for cutting is 0.5 to 1.0 mm and for bending is 0.50 to 10 degree
 
Subscribe to the Feed Now
Share |