REINFORCING DETAILING OF R.C.C MEMBERS

1
REINFORCING DETAILING OF R.C.C MEMBERS

• PRESENTED BY
• Er.T.RANGARAJAN,B.E,M.Sc(struct.engg),F.I.E,FACCE,
  LACI,LISSE,LIASE

2
WHO IS AN ENGINEER?

• According to USA President Herbert Hoover, who
  was an engineer before he became a politician,
  said
• The great liability of the engineer compared to
  men of other professionsis that his works are
  out in the open where all can see them.
• His acts ..step by step are in hard substances.
• He cannot bury his mistakes in the grave like the
  DOCTORS.
• He cannot argue them into thin air..or blame the
  judge..like the LAWYERS.
• He cannot, like the ARCHITECT, cover his figures
  with trees and vines.
• He cannot, like the politicians, screen his
  shortcomings by blaming his opponents.and hope
  the people will forget. The ENGINEER simply
  cannot deny he did it.
• If his works do not workhe is damned.

3

• A design engineers responsibility should include
  assuring the structural safety of the design,
  details, checking shop drawing.
• Detailing is as important as design since proper
  detailing of engineering designs is an essential
  link in the planning and engineering process as
  some of the most devasting collapses in history
  have been caused by defective connections or
  DETAILING. There are many examples explained in
  the book" DESIGN AND CONSTRUCTION FAILURES by Dov
  Kaminetzky.
• Detailing is very important not only for the
  proper execution of the structures but for the
  safety of the structures.
• Detailing is necessary not only for the steel
  structures but also for the RCC members as it is
  the translation of all the mathematical
  expressions and equations results.

4

• For the RCC members for most commonly used for
  buildings we can divide the detailing for
• SLABS-WITH OR WITHOUT OPENINGS.(RECTANGULAR,CIRCUL
  AR,NON-RECTANGULAR-PYRAMID SLAB,TRIANGULAR ETC)
• -BALCONY SLAB,LOFT SLAB,CORNER SLAB etc
• BEAMS- WITH OR WITHOUT OPENIGS.(SHALLOW DEEP
  BEAMS)
• COLUMNS.(RECTANGULAR,L-SHAPE,T-SHAPE,
• CIRCULAR,OCTAGONAL,CROSS SHAPE etc)
• 4. FOUNDATIONS.
• Detailing for gravity loads is different from the
  lateral loads specially for the SEISMIC FORCES.
• Apart from the detailing for the above there is a
  different detailing required for the
  Rehabilitation and strengthening of damaged
  structures.
• We will now dwell on the DETAILING OF MEMBERS FOR
  THE GRAVITY AND SOME CODAL DETAILINGS AS PER IS
  CODE IS 13920 AND IS 4326 AS REQUIRED FOR SEISMIC
  FORCES.

5
DOS DONOTS FOR DETAILING

• DOS-GENERAL
• Prepare drawings properly accurately if
  possible label each bar and show its shape for
  clarity.

12
I ¼dia_at_12c/c
1- ¼dia_at_12c/c
Cross section of retaining wall which collapsed
immediately after placing of soil backfill
because ¼ rather than 1-1/4 dia. were used.
Error occurred because Correct rebar dia. Was
covered by a dimension line.
6

• Prepare bar-bending schedule , if necessary.
• 3. Indicate proper cover-clear cover, nominal
  cover or effective cover to reinforcement.
• 4. Decide detailed location of opening/hole
  and supply adequate details for reinforcements
  around the openings.
• 5. Use commonly available size of bars and
  spirals. For a single structural member the
  number of different sizes of bars shall be kept
  minimum.
• 6. The grade of the steel shall be clearly
  stated in the drawing.
• Deformed bars need not have hooks at their
• ends.
• 8. Show enlarged details at corners,
  intersections of walls, beams and column joint
  and at similar situations.

7

• 9. Congestion of bars should be avoided at
  points where members intersect and make certain
  that all rein. Can be properly placed.
• 10. In the case of bundled bars, lapped splice
  of bundled bars shall be made by splicing one bar
  at a time such individual splices within the
  bundle shall be staggered.
• 11. Make sure that hooked and bent up bars can
  be placed and have adequate concrete protection.

8

• Indicate all expansion, construction and
  contraction joints on plans and provide details
  for such joints.
• The location of construction joints shall be at
  the point of minimum shear approximately at mid
  or near the mid points. It shall be formed
  vertically and not in a sloped manner.
• DOS BEAMS SLABS
• Where splices are provided in bars, they shall be
  , as far as possible, away from the sections of
  maximum stresses and shall be staggered.
• Were the depth of beams exceeds 750mm in case of
  beams without torsion and 450mm with torsion
  provide face rein. as per IS456-2000.
• Deflection in slabs/beams may be reduced by
  providing compression reinforcement.
• Only closed stirrups shall be used for transverse
  rein. For members subjected to torsion and for
  members likely to be subjected to reversal of
  stresses as in Seismic forces.

9

• To accommodate bottom bars, it is good practice
  to make secondary beams shallower than main
  beams, at least by 50mm.
• Dos COLUMNS.
• A reinforced column shall have at least six bars
  of longitudinal reinforcement for using in
  transverse helical reinforcement.-for CIRCULAR
  sections.
• A min four bars one at each corner of the column
  in the case of rectangular sections.
• Keep outer dimensions of column constant, as far
  as possible , for reuse of forms.
• Preferably avoid use of 2 grades of vertical bars
  in the same element.
• DONOTS-GENERAL
• Reinforcement shall not extend across an
  expansion joint and the break between the
  sections shall be complete.
• Flexural reinforcement preferably shall not be
  terminated in a tension zone.

10

• Bars larger than 36mm dia. Shall not be bundled.
• Lap splices shall be not be used for bars larger
  than 36mm dia. Except where welded.
• Where dowels are provided, their diameter shall
  not exceed the diameter of the column bars by
  more than 3mm.
• Where bent up bars are provided, their
  contribution towards shear resistance shall not
  be more than 50 of the total shear to be
  resisted. USE OF SINGEL BENT UP BARS(CRANKED) ARE
  NOT ALLOWED IN THE CASE OF EARTHQUAKE RESISTANCE
  STRUCTURES.

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DETAILING OF SLABS WITHOUT ANY CUT OR OPENINGS.

• The building plan DX-3 shows the slabs in
  different levels for the purpose of eliminating
  the inflow of rainwater into the room from the
  open terrace and also the sunken slab for toilet
  in first floor.
• The building plan DX-A3 is one in which the
  client asked the architect to provide opening
  all round.

Refer the 3d elevation
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• Different shapes of slabs used in the buildings.

6depression for OT 9 for sunken slabs.
Portico slab in elevation
19-6
5wide corridor all round
9-6suare opening
Portico slab in plan
Portico and other rooms roof slab in plan
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• Minimum and max.reinforcement in beams, slabs
  and columns as per codal provisions should be
  followed.
• SLABS
• It is better to provide a max spacing of
  200mm(8) for main bars and 250mm(10) in order
  to control the crack width and spacing.
• A min. of 0.24 shall be used for the roof slabs
  since it is subjected to higher temperature.
  Variations than the floor slabs. This is required
  to take care of temp. differences.
• It is advisable to not to use 6mm bars as main
  bars as this size available in the local market
  is of inferior not only with respect to size but
  also the quality since like TATA and SAIL are not
  producing this size of bar.
• BEAMS
• A min. of 0.2 is to be provided for the
  compression bars in order to take care of the
  deflection.

14

• The stirrups shall be min.size of 8mm in the case
  of lateral load resistance .
• The hooks shall be bent to 135 degree .

15
CANTILEVER BEAM
crack
INCORRECT
Ldt
CLOSE STIRRUPS
Ldt/2
Ld/2
Ld/2
CORRECT
Ld
16
NON PRISMATIC BEAM
crack
INCORRECT
Ldt
CLOSE STIRRUPS
Ldt/2
Ld/2
Ld/2
CORRECT
Ld
17
GRID BEAM

• GRID BEAM

INCORRECT
Close rings
1.5d
1.5d
1.5d
300
300
d
Hanger bars
2extra bars
CORRECT
Slope 110
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Details of Main Secondary beams
Secondary beam
Main beam
INCORRECT
Secondary beam
Close rings
1.5d
1.5d
1.5d
300
300
d
60degree
Hanger bars
Main beam
CORRECT
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BEAM
d
INCORRECT
1/4OR 1/5 SPAN
Ld
Ld
LINE OF CRACK
d/2
t
d/2
t
d/2d/2Cot(t)
1.5d
CORRECT
20
Continuous beam

• continuous beam

Span/4
Span/4
Span/4
Span/4
Span/4
incorrect
Span/4
Span/4
1.5d
1.5d
1.5d
correct
21
CONTINUOUS BEAM
SPAN/4
SPAN/4
SPAN/4
100
100
CRACK
.08L1
CRACK
CRACK
L1
.08L1
L2
.08L1
.08L2
INCORRECT
100
L1/4
L2/4
L1/4
20
20
100
100
0.1L1
L1
L2
.15L1
.15L2
CORRECT
22
NONPRISMATIC SECTION OF BEAM
D
CRACK
D
D
INCORRECT
CLOSE RING
D
D
CORRECT
D
CLOSE RING
23
CANTILEVER BEAM PROJECTING FROM COLUMN
COLUMN
INCORRECT
NOT LESS THAN 0.5Ast
NOT LESS THAN GREATER OF 0.5L OR Ld
50mm
Ld
0.25Ast
COLUMN
CORRECT
Ld/3
24
SLOPING BEAM
CRACK
Ld
Ld
CORRECT
25
HAUNCH BEAMS
CRACK
CRACK
L
INCORRECT
Ld
Ld
CORRECT
L/8 TO L/10
Ld
Ld
L/8 TO L/10
L
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STRESSES AT CORNERS
C-COMPRESSION T-TENSION
C
t
C
CRACK
t
RESULTANT TENSILE STRESS FOR ACROSS CORNER(ONE
PLANE)
RESULTANT TENSILE STRESS FOR ACROSS
CORNER(DIFFERENT PLANE)
t
CRACK
c
t
c
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SHEAR AND TORSION REIN. IN BEAMS
Stirrups taken round outermost bars spacingltx1
lt(x1y1)/4 lt300mm
Min 0.2bd to control deflection as well as for
seismic requ.
INCORRECT
n
d
y1
Skin rein.10dia is required when depth exceeds
450mm(0.1 of web area distributed equally on two
faces)
D
100 to 200mm
D-ngt500mm
D-ngt500mm
D/5
x1
CORRECT
b
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CANTILEVER BEAM WITH POINT LOAD
Shear rein.
INCORRECT
2/3d
d
Ld
CORRECT
Ld
Extra ties
29
INCORRECT
opening
crack
crack
OPENING IN WEB OF BEAM
opening
d/2
d/2
Closed stps for d/2
Closed stps for d/2
Ld
OPENING IN WEB OF BEAM
CORRECT
30
BEAM COLUMN JUNCTION-EXTERIOR COLUMN
INCORRECT
CLOSED STPS
2max
U TYPE BARS
Ld
IN TENSION-Ld
CORRECT
31
SPLICE DETAIL FOR COLUMN
COVER
CLOSE TIES _at_S/2
SLOPE 16
S-SPACING
CORRECT
INCORRECT
32
REDUCTION COLUMN BOTH SIDES
INCORRECT
SPLICE
SLOPE 18 FROM BEAM BOTTOM
3NO.CLOSE TIES
CLOSE STPS SPACIN lt75mm
3NO.CLOSE TIES
CORRECT
33
TERMINATION OF COLUMN BARS INSIDE BEAM
INCORRECT
Ld
CORRECT
34
COL.CORE HAS TO BE CONFINED BY CIRCULAR OR
RECTANGULAR TIES IN ACCORDANCE WITH END REGION
EQ REGION-BEAM-COL JN-EXTERIOR
SPACING OF LATERAL TIES ltd/2
COL. CORE
END REGION
SPACING OF LATERAL TIES lt100mm
END REGION
BEAM COL. JUNCTION-EQ REGION
CORRECT
INCORRECT
SPACING OF LATERAL TIES ltd/2
SPACING OF LATERAL TIES ltd/2
BEAM COL. JUNCTION-EQ REGION
35
COLUMN DETAILS IN EQ REGIONS
incorrect
First stirrups 50mm from beam face
correct
END REGION
END REGION-h/6 or D or 450MM whichever is greater
h
d
b
D
END REGION
END REGION
Spacing of shear rein. In columns
Spacing of shear rein. In columns
36
EQ-REGION-CONTINUOUS BEAM
INCORRECT
50mmmax
CONTINUOUS BARS NOT LESS THAN ¼ AREA OF BARS AT
COL.FACE
CORRECT
AL1/3
AL1/3
AL1/3
Ld
2d
2d
2d
stp_at_maxd/2
stp_at_maxd/2
2d
Stirrup spacingd/4 or 100mm or 8dia which ever
is the least
37
FOOTING-DETAILS(INDEPENDENT)
INCORRECT
COLUMN BARS
STARTER BARS
NATURAL G.L
COVER TO STARTER
Lb
3 SIDE COVER
Ldt
Min.300
COVER50mm IF p.c.c below or 75mm
Ldt
CORRECT
38
TYPICAL REIN DETAILS OF HAMMER FOUNDATION BLOCK
INCORRECT
CORRECT
Ld
Ld
39
SECTION OF TRENCH
INCORRECT
INCORRECT
CRACK
CORRECT
Ld
Ld
Ld
40
STAIRCASE-WITH WAIST SLAB
INCORRECT
Extra bar
Ld(min)
Ld(min)
Ld(min)
CORRECT
41
SLABLESS STAIRCASE
Dist.
Alternate 1
Main bar
Main bar
42
SLABLESS STAIRCASE
Main bar
Lhorizontal span
Alternate 2
A0.25L
43
DEVELOPMENT LENGTH OF BARS
FOR A CONCRETE GRADE M20 STEEL STRENGTH Fy415
SLNO BAR DIA. TENSIONmm COMPRESSION REMARKS
1 8 376.0 301.0
2 10 470.0 376.0
3 12 564.0 451.0
4 16 752.0 602.0
5 20 940.0 752.0
6 22 1034.0 827.0
7 25 1175.0 940.0
8 28 1316.0 1053.0
9 32 1504.0 1203.0
APPROXIMATELY USE 50Xdia FOR TENSION
44

• CONCLUSION
• Before concluding I will show some more details
  drawn in autocad exported in wwf format
• As there is no time to elaborately explaining
  ,the following topics are not covered
• Flat slabs, Folded plates, shell
  structures-cylindrical shells, silos,
• Staircases- helical staircase, central beam type,
  cantilever type etc.
• Different types of foundations-raft, pile
  foundation, strap foundation etc.
• Retaining wall structures,
• Liquid retaining structures.
• Deep beams.
• Shear wall, walls.
• Hope that I have enlighten some of
  the detailing technique for the most commonly
  encountered RCC members in buildings.
• In the above statements if my senior
  colleagues and ACCE members can find different
  method or any new detailing system it will be of
  immense help not only for me but to other young
  engineers who should learn in wright ways and
  not wrong lessons.

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REFERENCES

• HANDBOOK ON CONCRETE REINFORCEMENT AND
  DETAILING-SP34(ST)-1987.
• MANUAL OF ENGINEERING PLACING DRAWINGS FOR
  REINFORCED CONCRETE STRUCTURES-
• (ACI 315-80
• MANUAL OF STANDARD PRACTICE CONCRETE
  REINFORCING STEEL INSTITUTE.
• TWARD BOARD MANUAL FOR RURAL WATER SUPPLY
  SCHEMES.
• DESIGN PRINCIPLES AND DETAILING OF CONCRETE
  STRUCTURES. By D.S.PRAKASH RAO.
• SIMPLIFIED DESIGN-RC BUILDINGS OF MODERATE SIZE
  AND HEIGHT-BY PORTLAND CEMENT ASSOCIATION,USA.
• DESIGN AND CONSTRUCTION FAILURES BY DOV
  KAMINETZKY.

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1. IS2502-1963 CODE OF PRACTICE FOR BENDING AND
   FIXING OF BARS FOR CONCRETE REINFORCEMENT.
2. IS18932000.
3. IS4326.
4. IS4562000
5. REINFORCED HAND BOOK BY REYNOLD.

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THANK YOU.