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[picajol]

Hi all!
Please see the sketch attached.
This is an canteliver retaining wall 3m high with an wall thats 20cm thick.
It will be 60m long.

How much of the horizontal reinfrocement on the front face of the wall would you apply to control the vertical cracking due to restrain of the foundation to wall connection?
Also at what distances wozld you provide contraction joints and how horizontal reinforcement would you provide in that front face?

There seems to be a lot of debate on this and also people seems to get confused on wich reinforcement controls what.
Im interested to hear your thoughts.


Thank you

[vikram.jeet]

Dear Er

Please see any text book on structural design Retsining wall desin is covered in all str design booksin much details,,

Still some points :
An rcc cantilever retaining wall derives itd stability from its base ,, which on heel side hass backfill weight over it preventing it from overturning, sliding,,

The very backfill which exert earth pressures,, is also a stabilizing item,,

The wall and base slab shall be monolithic,,

In design
check overturning,, ( FOS > 2.0 normal and 1.5 wind /eq)
Check Sliding ( FOS >1.5 normal and1. 25 wind/eq)
Check Base pressures (max within SBC,, minimum preferably +ve)
If min base pr is negative ,, carry out redistribution as per given jn text books, but see upliftment area is less than20% for normal case and 33% in wind/eq)

Other finer points :
Provide weep holes in wall to dissipate water pressures due to backfill charged conditions

In case water table of area is high (during monsoon) ,, take effect of uplift along with hydrostatic pressure on wall

Kindly see a text book to get design philosophy

[vikram.jeet]

Expansion joint - yr wall is 60m ,, provide one expansion joint
Construction joint : Max casting length ,, if 7.5m ,, minimum horz reinf will suffice,,
If casting length is higher,, horz reinf can be increased as per
But if wall is not a water retaining structure,, this csn be relaxed,,
Reinforcement :
Main reinforcement in wall : Vertical reinf on earth side, on front side minimum reinf

Horz reinf is distribution reinf

[picajol]

Dreak Virkam "horizontal" reinforcement is fot temeparature and shrinkage, and this is the subject thats very interesting and I also think that amount of it deppends on the distance between the expansions joints.
Can you comment

[vikram.jeet]

Horizontal reinforcement :

For water retaining walls of reservoirs,, provision of horizontal reinforcement needs special attention and latest IS3370 part 1 &2 have given% horz reinf depending on const joint (also contraction jt) spacing,
You can also refer Fintel Handbook,, providing a curve giving distance between contraction joints vs% horz reinf,,


But for Retaining wall s not water retaining,, Minimum reinforcement as per IS 456 suffice ,,

For Rcc ret walls expansion joints can be taken max 30m ,,

[picajol]

Just to be 100% certain.
Expansion joint are not same as control joint.
Control joint are to control the effect due to shrikage

[vikram.jeet]

Just to elaborate :
Expansion joints at 30 m spacings are for thermal effects.
Reinforcement and concrete - complete discontinuity,, with a gap to be treated as per specs.

Control joint - Also csn be construction joints as well ad contraction joints ,, where construction can be stopped but casting Length affects horz reinf provision,,
These are for shrinkage effects of conc,,
Full reinf continuity,, but casting of adjacent lengths can ne staggered,

For water ret structures, crack control as per IS 3370 must ,,

For others min horz reinf as per IS 456 ,, ok

[picajol]

As previously said, construction joints are to allow shrinkage cracks at the joint location. I understand. But this 7,5m distance that you mentioned is a very short distance. I must say Im a bit suprissed

One question, if you provide an control/contraction joint, you basicaly cut every other horizontal bar/reinforcement in the wall at that joint location, correct?

For expansion joint, that are placed every 30m, you need to provide somekind of "dowel bars" (full discontinuity in concrete and rebar section) as on slabs on grade, correct?

[vikram.jeet]

[picajol]

Dear Virkam.jeet, I thank you VERY VERY much for the info you gave here. I will look for the FINTEL book and get back here soon
One more time, thank you very much!