8/16/2019 Anchorage of beam bars at external joints.

1/1

IS 456: 2000

16.2.1.1 Design bond stress in limit state method for plain bars in tension shall be as below:

rade of concrete

esign bond streSf hd, N/mm

2

M 20

1.2

M2 5

1.4

M30

1.5

M 35

1.7

M 40 and above

1.9

For deformed bars conforming to IS 1786thesevaluesshall be increased by 60 percent.

For bars in compression. the values of bond stress forbars in tension shall be increased by 25 percent.

The values of bond stress in working stress design,are given in B-2.1.

26.2.1.2 Bars bundled contact

The development length of each bar of undled barsshall be that for the individual bar, increased by 0percent for two bars in contact, 20 percent for three

bars ·in contact and 33 percent for four bars in contact.26.2.2 Anchoring ReinforcingBars

26.2.2.1 Anchoring bars in tension

a) Deformed bars may be used without endanchorages provided development lengthrequirement is satisfied. Hooks should normallyhe provided for plain bars in tension.

b) Bends an d hooks - Bends and hooks shallconform to IS 25 02

J) Bends The anchorage value of bend shallbe taken as 4 times the diameter of the barfor each 45 t bendsubject to a maximum of16times the diameter of the bar.

2) ooks The anchorage value of a standardU-type hook shall be equ l to J6 times thediamet.er of the bar.

26.2.2.2 Anchoringbars in compression

The anchorage length of straight bar in compressionshall be equal to the development length of bars incompression as specified in 26.2..1. The projectedlength of hooks, bends and straight lengths eyond

bends if provided for a bar in compression, shall onlybe considered for development length.

16.2.2.3 Mechanical devices [or anchorage

Any mechanical or other devicecapable of developingthestrengthof the barwithout damage to concrete maybe usedas anchorage with the approvalof theengineerin-charge.

26.2.2.4 Anchoring shear reinforcement

a) Inclined bars - The development length shanbe as for bars in tension; this length shall be

measured as under:1) In tension zone, from the end of the sloping

Of inclined portion of the bar, and

2) In the compression zone, front themid depthof the beam.

b) St i r rups No twi ths t and ing any of theprovisions of this standard, in case of secondaryreintorcement, such as stirrups and transverseties complete development lengths andanchorage shall be deemed to have beenprovided when the bar is bent through an angleof at least 90 round a bar of at least its owndiameter and is continued beyond the end of thecurve for a lengthof at least eight diameters, orwhen the bar is bent through an angle of 135 0

and is continued beyond the end of the curvefor a length of at least six bardiameters or whenthe bar is bent throughan angle of 1 O° and iscontinued beyond the end of the curve for alength of at least four bar diameters.

26.2.2.5 Bearing stresses at bends

The hearing stress in concrete for bends and hooksdescribedinIS2502 neednotbechecked. The bearingstress inside a bend in any other bendshallbecalculatedas given below:

FhtBearing stress =r i

where

} ol =: tensile force due to design loads in a baror group of hal s,

,. = internal radius of the bend, and

¢ = size of the bar or, inbundle. the size of harof equivalent area.

For limit stale method of design, this stress shall not

I .5~

t h h . .exceed W iere r. k IS t e c aractensuc cube1 2 ~ a C·strength of concrete and a for a particular buror groupof hars in contact shall he taken as the centre to centredistance between bars or groups of bars perpendicularto the plane of the bend; for a bar O f group ofbars adjacent to the face of the member a shall hetaken as the cover plus size of ba r q» For working

stress method of design the b earing s tr es s shall

not exceed ~J+2c/J/a

26.2.2.6 If a change in direction of tension orcompression reinforcement induces a resultant forceacting outward tending to split theconcrete, such force