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13. Beam rebar arrangement
1) Principle of beam rebar arrangement① Calculate the size and depth of beams according to the drawing and arrange them
in a suggested order, that is, exterior beams and big beams(G) & deep beams first
and then binding small beams(B beams) later.
② Supervisor has to check if the bar used at the top span meets the requirement on
the drawing.
Shorter bar than required might be used to save cost when the span is longer than
8,000mm, the bar standard.
③ The bar might deflect from undesirable vibration when placing concrete if the
double reinforcement or top end bar are tied with tying wires.
To prevent this, 3 pieces of stirrups are used to tie the bars at the top and as many
pieces to place double-leg bar & top bar on the bottom bar.
④ Cap tie bar should carry out 1 by 1 at least.
※ The 1st stirrup should be arranged with the space 50mm from the perimeter of
side pillar.
@/2 or under 50mm from side pillar @/2 or under 100mm from side big beam
<The height will be changed by th rebar size>
Stirrup:end support(S.T.)
1st stirruparrangement besideof pillar’s main bar
1st stirruparrangement besideof big beam main bar
big beam
Center support(S.T.)
※ The splice for upper part rebar of beam's end and lower part rebar of beam's center
apply tension splice length.
※ Apply the above except the case of marking separately on beam chart.
※ S1-S4 : stirrup distance
2) Types of stirrup
Ldh
S1 S2 S3
5050
end0.25L1
center0.5L1L1 L2
end0.25L1
end0.25L2
center0.5L2
50
S4
12db
0.3L1 OR 0.3L2 0.3L1 OR 0.3L2
min 15㎝ min 15㎝ or continuance min 15㎝ or continuance0.125L1
0.125L1 0.125L1L1 L2
0.125L2
<Main bar arrangement>
<Distance of stirrup>
- beam without cap tie bar- beam to be arranged by front end without twisting- beam without anti-earthquake plan
① slab on both sides ② slab on one-side ③ no slab on both sides
<a> Open type
<b> Closed type
middle/big value
middle/big value
3) Position of beam tying(splice)
※ Splice location : diagonal line
① Calculation of bender
When bent bars are used to reinforce beams, bending point of the bar is usually
calculated as distance from the center of the pillar.
However, it is formal to divide it into 4 parts from the end of beam reinforcement
to the other end.
- beam with front end and twist- in case of anti-earthquake plan
wall girder
pillar
over
30c
m
over
45c
m
splic
e ag
ains
t tot
aldi
stan
ce o
f mem
ber
② An example for processing
Anchorage(fixed) bars are classified as the top bars and the bottom bars, when the
former have tensile loads and the later have compression loads.
Therefore, the top bars and bottom bars set fixed splice length with same method
because it has difficulty in working separately for processing and
assembling.(criterion of concrete structure plan)
In a real construction, 40d is used for both of them for convenience sake.
③ Cover depth of beams
ⓐ Stirrup with spacer should be tied several times.
ⓑ Pay attention when arranging reinforcements in order to have enough cover depth.
4) Bending position of bender (classification of tension & compression)
※ Using the bent bars in beams is Japanese style, while cutoff bar is now in common.
spacer
Y beam
Y beam X beam
X beam
Ten
sion
fixa
tion
Tensionfixation A class tension splice
A class tension splice
bent bar
penetrationof bent bar
top bar
(Top floor)
(General floor)
bent bar
height 40
coverthickness 40
5) Beam rebar arrangement(CUT TYPE)① In case of beam
② In case of girder
Note
1) * : apply general bars splice length(A class splice) as standard splice length &
fixed length of rebar(22page 6)) for above size
2) ** : fixed as standard hook form about center part bottom bar's 25%
3) splice length according to splice position of rebar arrangement
- tying on upper part rebar(beam) block : apply A class tension rebar splice
tying except upper part rebar(beam) block : apply B class tension rebar splice
- tying on lower part rebar(beam) block : apply A class tension rebar splice
tying except lower part rebar(beam) block : apply B class tension rebar splice
0.3L or 0.3L1 0.3L or 0.3L1
big value big value
0.3L or 0.3L1 0.3L or 0.3L1
big value big valuestandard hookfixed length
6) Beam rebar arrangement by using stepped pulleyThe types of step are classified as planar step, elevated step, step in material
according to their shapes.
In each case, arrangement is in vertical or in horizontal.
If the worker has no choice but to bend the bar, bend it at low grade.
When the mid span of a beam has steps as shown below left, the bar might be
necessarily bent, which is quite undesirable.
The load tends to straightly pass through.
If pulled out, the bar does not straighten as it looks.
Far from straightening, it will break or fracture.
Needless to say, it is recommended that the worker cut the bars and arrange them
separately, as depicted below.
tension fixed lengthtension fixed
length
breakable due to the tension
Wrong method Correct method
7) Hunch beam① Bend the bars at the bottom in a hunch former and anchor them onto the pillar.
② Bend a half of the bars at the bottom to let the anchorage length penetrate the pillar
and anchor near the hunch point.
③ One size bigger stirrup should be used at the hunch point.
8) Pillar-holding rebar (Butterfly stitching rebar/Stirrup closing rebar)① As few drawing gives direction on pillar-holding rebar, it is common to use it at
every third stirrup.
If not, all junctions of pillar-holding rebar should be confined per every stirrup.
S.T. one size bigger stirrup
stirrup
processing
(current) (revised)
<butterfly stitching rebar>
Better if one end hooked 135°
9) Symbol of beam·Continuous end of beam
·Center of beam
·Exterior of beam
·Interior of beam
·Outside of beam
end stirrup:arrange 200mm distance-D10upper part : HD22-3
end top bar : HD22-2
EXT(exterior) CENT(center)
400×500(stirrup process size : 320×420)
300×500(stirrup process size : 220×420)
stirrup : arrange 200mm distance-D10
tension splice(B class splice)
upper part bar : HD22-3EA
END(end)
END(end) CENT(center)
center stirrup-arrange 250mm distance-D10
center top bar : HD22-2
lower part bar :HD22-3
support bar : HD13-2EA
support bar : HD22-3EA
lower part bar : HD22-3EA
10) Detailed drawing of beam rahmen(arrangement)
horizontal rebar : HD10@200(arrange 200mm distance-D10)
vertical rebar : HD10@200(arrange 200mm distance-D10)
400×500(stirrup process size : 320×420)
400×400(hoop process size : 320×320)
tension splice(B class splice)
Each floor bottom structure plane figure symbol & beam chart symbol
END(end) CENT(center)
tension splice
hoop : arrange 250mm distance-D10
main bar : 10-HD19
support big bar : arrange 250mm distance-D10
※ You should check pillar size & rebar Q’ty per each floor, and also arrange after
checking rebar Q’ty & drawing of outer pillar’s front and side.