Re Rein Detailing

7/31/2019 Re Rein Detailing

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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

www.engineeringcivil.com


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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 menof other professionsis that his works are out inthe open where all can see them.His acts ..step by step are in hard substances.

He cannot bury his mistakes in the grave like theDOCTORS.He cannot argue them into thin air..or blame thejudge..like the LAWYERS.He cannot, like the ARCHITECT, cover his figures

with trees and vines.He cannot, like the politicians, screen hisshortcomings by blaming his opponents.and hopethe people will forget. The ENGINEER simply cannotdeny he did it.

If his works do not workhe is damned.


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A design engineers responsibility should includeassuring the structural safety of the design,details, checking shop drawing.

Detailing is as important as design since properdetailing of engineering designs is an essentiallink in the planning and engineering process assome of the most devasting collapses in historyhave been caused by defective connections or

DETAILING. There are many examples explainedin the book" DESIGN AND CONSTRUCTIONFAILURES by Dov Kaminetzky.

Detailing is very important not only for theproper execution of the structures but for the

safety of the structures.Detailing is necessary not only for the steelstructures but also for the RCC members as it isthe translation of all the mathematicalexpressions and equations results.


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For the RCC members for most commonly used for buildings we candivide the detailing for

1. SLABS-WITH OR WITHOUT OPENINGS.(RECTANGULAR,CIRCULAR,NON-RECTANGULAR-PYRAMID SLAB,TRIANGULAR ETC)

-BALCONY SLAB,LOFT SLAB,CORNER SLAB etc

2. BEAMS- WITH OR WITHOUT OPENIGS.(SHALLOW & DEEP BEAMS)

3. COLUMNS.(RECTANGULAR,L-SHAPE,T-SHAPE,CIRCULAR,OCTAGONAL,CROSS SHAPE etc)

4. FOUNDATIONS.

Detailing for gravity loads is different from the lateral loads specially forthe SEISMIC FORCES.

Apart from the detailing for the above there is a different detailingrequired for the Rehabilitation and strengthening of damaged structures.

We will now dwell on the DETAILING OF MEMBERS FOR THE GRAVITYAND SOME CODAL DETAILINGS AS PER IS CODE IS 13920 AND IS 4326AS REQUIRED FOR SEISMIC FORCES.


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DOS & DONOTS FOR DETAILING

DOS-GENERAL

1. Prepare drawings properly & accurately if possible label each bar

and show its shape for clarity.

12

I dia@12c/c

Cross section of retaining wall which collapsed immediately after placing of soilbackfill because rather than 1-1/4 dia. were used. Error occurred because

Correct rebar dia. Was covered by a dimension line.

1- dia@12c/c


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2. 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 andsupply adequate details for reinforcementsaround the openings.

5. Use commonly available size of bars and spirals.

For a single structural member the number ofdifferent sizes of bars shall be kept minimum.6. The grade of the steel shall be clearly stated in

the drawing.7. Deformed bars need not have hooks at their

ends.8. Show enlarged details at corners, intersections

of walls, beams and column joint and at similarsituations.


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9. Congestion of bars should be avoided at points wheremembers intersect and make certain that all rein. Can beproperly placed.

10. In the case of bundled bars, lapped splice of bundled barsshall be made by splicing one bar at a time; suchindividual splices within the bundle shall be staggered.

11. Make sure that hooked and bent up bars can be placedand have adequate concrete protection.


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12. Indicate all expansion, construction and contraction jointson plans and provide details for such joints.

13. The location of construction joints shall be at the point ofminimum shear approximately at mid or near the mid points.It shall be formed vertically and not in a sloped manner.

DOS BEAMS & SLABS:

1. Where splices are provided in bars, they shall be , as far aspossible, away from the sections of maximum stresses andshall be staggered.

2. Were the depth of beams exceeds 750mm in case of beamswithout torsion and 450mm with torsion provide face rein.as per IS456-2000.

3. Deflection in slabs/beams may be reduced by providingcompression reinforcement.

4. Only closed stirrups shall be used for transverse rein. Formembers subjected to torsion and for members likely to besubjected to reversal of stresses as in Seismic forces.


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5. To accommodate bottom bars, it is good practice to makesecondary beams shallower than main beams, at least by50mm.

Dos COLUMNS.1. A reinforced column shall have at least six bars of

longitudinal reinforcement for using in transverse helicalreinforcement.-for CIRCULAR sections.

2. A min four bars one at each corner of the column in thecase of rectangular sections.

3. Keep outer dimensions of column constant, as far aspossible , for reuse of forms.

4. Preferably avoid use of 2 grades of vertical bars in thesame element.

DONOTS-GENERAL:

1. Reinforcement shall not extend across an expansion jointand the break between the sections shall be complete.

2. Flexural reinforcement preferably shall not be terminatedin a tension zone.


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3. Bars larger than 36mm dia. Shall not be bundled.

4. Lap splices shall be not be used for bars larger than36mm dia. Except where welded.

5. Where dowels are provided, their diameter shall notexceed the diameter of the column bars by more than3mm.

6. Where bent up bars are provided, their contributiontowards shear resistance shall not be more than 50% of

the total shear to be resisted. USE OF SINGEL BENT UPBARS(CRANKED) ARE NOT ALLOWED IN THE CASEOF EARTHQUAKE RESISTANCE STRUCTURES.


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DETAILING OF SLABS WITHOUT ANY CUTOR OPENINGS.

The building plan DX-3 shows theslabs in different levels for thepurpose of eliminating the inflow of

rainwater into the room from the openterrace and also the sunken slab fortoilet in first floor.

The building plan DX-A3 is one inwhich the client asked the architect toprovide opening all round.

Refer the 3d

elevation


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Different shapes of slabs used in thebuildings. 6depression for OT &

9 for sunken slabs.

Portico slab in elevation

19-6

9-6suareopening

5wide corridor all

round

Portico and other roomsroof slab in plan

Portico slab in plan


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Minimum and max.reinforcement % in beams, slabs andcolumns 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 issubjected to higher temperature. Variations than the floorslabs. This is required to take care of temp. differences.

It is advisable to not to use 6mm bars as main bars as thissize available in the local market is of inferior not only withrespect to size but also the quality since like TATA and SAILare not producing this size of bar.

BEAMS:

A min. of 0.2% is to be provided for the compression bars inorder to take care of the deflection.


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The stirrups shall be min.size of8mm in the case of lateral load

resistance .The hooks shall be bent to 135degree .


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Ld/2Ld/2

Ld

crack

INCORRECT

CORRECT

CLOSESTIRRUPS

Ldt

Ldt/2

CANTILEVER BEAM


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NON PRISMATIC BEAM

Ld/2 Ld/2Ld

INCORRECT

CORRECT

CLOSESTIRRUPS

crack

Ldt/2

Ldt

GRID BEAM


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GRID BEAMGRID BEAM

INCORRECT

1.5d1.5d1.5d

Close rings

Hanger bars

Slope 1:10

2#extra bars

300300

d

CORRECT


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Details of Main & Secondary beams

INCORRECT

1.5d1.5d1.5d

Close rings

Hanger bars

300300

d

CORRECT

Secondary beam

Main beam

Secondary beam

60degree

Main beam


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d

1/4OR1/5 SPAN

1.5d

CORRECT

INCORRECT

d/2+d/2Cot(t)

tt

Ld

d/2

d/2

LdLINE OF CRACK

BEAM


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Continuous beam

continuous beamSpan/4

Span/4Span/4

Span/4

incorrect

Span/4

Span/4

1.5d1.5d

Span/4

correct

1.5d


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100%

L1

100% CRACKCRACK

.08L2.08L1 L2

SPAN/4 SPAN/4

CONTINUOUS BEAM

INCORRECT

.08L1

.08L1

SPAN/4

CRACK

100%

L1

100%

.15L2 L2

L1/4 L2/4

CORRECT

0.1L1

.15L1

L1/4100%

20%20%


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D

D

CRACK

INCORRECT

NONPRISMATICSECTION OF BEAM

D

D

DCORRECT

D

CLOSE RING

CLOSE RING


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COLUMN

INCORRECT

CANTILEVER BEAM PROJECTINGFROM COLUMN

CORRECT

NOT LESS THAN GREATER OF 0.5L OR Ld50mm

0.25Ast

NOT LESSTHAN 0.5Ast

COLUMN

Ld

Ld/3


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CRACK

SLOPING BEAM

CORRECT

Ld

Ld


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CRACKCRACK

INCORRECT

HAUNCH BEAMS

CORRECTL/8 TOL/10 L/8 TO

L/10

L

L

Ld Ld

Ld Ld


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STRESSES AT CORNERS

C

C-COMPRESSION

T-TENSION

t

t

C

RESULTANT TENSILE STRESS FORACROSS CORNER(ONE PLANE)

t

c

RESULTANT TENSILE STRESS FORACROSS CORNER(DIFFERENT PLANE)t

c

CRACK

CRACK


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SHEAR AND TORSION REIN. IN

BEAMS

INCORRECT

Min 0.2%bd to control deflection aswell as for seismic requ.

b

D100 to

200mm

d

D-n>500mm

D/5

Skin rein.10dia isrequired when depth

exceeds 450mm(0.1%of web area distributedequally on two faces)

Stirrups taken round outermostbars spacing


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CANTILEVER BEAM WITH

POINT LOAD

CORRECT

INCORRECT

2/3dd

Shear rein.

Extra ties

Ld

Ld


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opening

CORRECT

OPENING IN WEB OF BEAM

crackcrack

opening

INCORRECT

OPENING IN WEB OF BEAM

Ld

d/2 d/2

Closed stpsfor d/2

Closed stps

for d/2


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BEAM COLUMN JUNCTION-EXTERIOR COLUMN

CORRECT

INCORRECT

CLOSED STPS2max

IN TENSION-Ld

U TYPE BARS

Ld


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CORRECT

SPLICE DETAIL FOR COLUMN

INCORRECT

COVER

CLOSETIES @S/2

S-SPACING

SLOPE 1:6


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REDUCTIONCOLUMN BOTHSIDES

INCORRECT

CORRECT

3NO.CLOSE TIES

SPLICE

CLOSE STPS SPACIN


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TERMINATION OF COLUMN BARS INSIDE BEAM

INCORRECT

CORRECT

Ld


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BEAM COL. JUNCTION-EQREGION

EQREGION-BEAM-COL JN-EXTERIOR

CORRECT

BEAM COL. JUNCTION-EQREGION

INCORRECT

END REGION

END REGION

COL.

CORE*

SPACING OFLATERALTIES


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COLUMN DETAILS IN EQ REGIONS

ENDREGION

ENDREGION

First stirrups50mm from beam

face

Spacing of shear rein. In

columns

incorrect

Spacing of shear rein. Incolumns

correct

END REGION-h/6 or D or450MM whichever isgreater

ENDREGION

hd

D

b

EQ REGION CONTINUOUS BEAM


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EQ-REGION-CONTINUOUS BEAM

INCORRECT

Ld

A=L1/3

CONTINUOUS BARS NOT LESS THAN AREA OF BARS AT COL.FACE

A=L1/3 A=L1/3

2d

50mmmax

Stirrup spacing=d/4 or

100mm or 8dia whichever is the least

2d2d 2dstp@maxd/2 stp@maxd/2

CORRECT


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INCORRECT

FOOTING-DETAILS(INDEPENDENT)

CORRECT

COVER TOSTARTER

STARTERBARS

COLUMNBARS

NATURALG.L

Ldt

Lb3 SIDE COVER

LdtCOVER50mmIF p.c.c below

or 75mm

Min.300

TYPICAL REIN DETAILS OF


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TYPICAL REIN DETAILS OFHAMMER FOUNDATION BLOCKINCORRECT

CORRECT

Ld

Ld


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SECTION OF TRENCH

CRACK

INCORRECTINCORRECT

CORRECT

LdLd

Ld


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STAIRCASE-WITH WAIST SLAB

INCORRECT

CORRECT

Ld(min)Extra bar

Ld(min)

Ld(min)

SLABLESS STAIRCASE


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Main bar

Dist.

Main bar

Alternate 1

SLABLESS STAIRCASE

SLABLESS STAIRCASE


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Main bar

Alternate 2

A=0.25L

L=horizontal span

SLABLESS STAIRCASE


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DEVELOPMENT LENGTH OF BARS

SLNO BARDIA.

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

FOR A CONCRETE GRADE M20 &STEEL STRENGTH Fy=415

APPROXIMATELY USE 50Xdia FOR TENSION


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CONCLUSION:Before concluding I will show some more details drawnin autocad exported in wwf format

As there is no time to elaborately explaining ,the following topics are notcovered :

1. Flat slabs, Folded plates, shell structures-cylindrical shells, silos,2. Staircases- helical staircase, central beam type, cantilever type etc.3. Different types of foundations-raft, pile foundation, strap foundation etc.4. Retaining wall structures,5. Liquid retaining structures.6. Deep beams.7. Shear wall, walls.

Hope that I have enlighten some of the detailing technique for the mostcommonly encountered RCC members in buildings.

In the above statements if my senior colleagues and ACCE memberscan find different method or any new detailing system it will be of immensehelp not only for me but to other young engineers who should learn in wrightways and not wrong lessons.

REFERENCES


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REFERENCES:

1. HANDBOOK ON CONCRETE REINFORCEMENT ANDDETAILING-SP:34(S&T)-1987.

2. MANUAL OF ENGINEERING & PLACING DRAWINGSFOR REINFORCED CONCRETE STRUCTURES-

(ACI 315-80

3. MANUAL OF STANDARD PRACTICECONCRETEREINFORCING STEEL INSTITUTE.

4. TWARD BOARD MANUAL FOR RURAL WATERSUPPLY SCHEMES.

5. DESIGN PRINCIPLES AND DETAILING OF CONCRETESTRUCTURES. By D.S.PRAKASH RAO.

6. SIMPLIFIED DESIGN-RC BUILDINGS OF MODERATESIZE AND HEIGHT-BY PORTLAND CEMENTASSOCIATION,USA.

7. DESIGN AND CONSTRUCTION FAILURES BY DOVKAMINETZKY.


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8. IS:2502-1963 CODE OF PRACTICE FOR BENDING ANDFIXING OF BARS FOR CONCRETE REINFORCEMENT.

9. IS:1893:2000.

10. IS:4326.11. IS:456:2000

12. REINFORCED HAND BOOK BY REYNOLD.


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THANK YOU.

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Re Rein Detailing