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kawshik9 General Sponsor
Joined: 28 Oct 2009 Posts: 16
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Posted: Wed Apr 27, 2022 7:29 am Post subject: Crack width calculation- ε2 is calculated to be more ε1 |
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Dear all,
I am designing water conveying underground Box and I have following query regarding crack width calculation.
" Strain due to stiffening effect of concrete between cracks ε2 is calculated to be more ε1, leading to negative value of Avg strain εm. What does it mean? should we consider it to be uncracked or neglect ε2 and calculate crack width with εm = ε1".
Please clarify my doubt. Thanking you
Kawshik
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vikram.jeet General Sponsor
Joined: 26 Jan 2003 Posts: 3839
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Posted: Thu Apr 28, 2022 11:50 am Post subject: |
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Just a thought on this issue :
Pl check that SI units being used for all inputs of formula
Verify the tensile stress in conc at tension face , for M25 , if stress donot exceed , then section is deemed to be uncracked. Permitted stress for uncracked condition is 1.3 Mpa for direct tension and 1.8 Mpa for bending tension . For combined tendion and bending pl see unity check.
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kawshik9 General Sponsor
Joined: 28 Oct 2009 Posts: 16
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Posted: Thu Apr 28, 2022 1:09 pm Post subject: |
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Dear sir,
I have checked tensile stress in concrete for uncracked section and it is only 0.34 MPa which is less than Permitted stress. Thankyou for suggestion.
I have checked the issue in RC Design by Pillai & Menon text book. There it is mentioned if εm <0, the section is uncracked.
Thankyou once again.
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vikram.jeet General Sponsor
Joined: 26 Jan 2003 Posts: 3839
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Posted: Fri Apr 29, 2022 4:06 am Post subject: |
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As per spirit of IS 3370 p2 , if tensile stresses are within permissible limits , crack control is achieved automatically. This is as per WSM .
In case LSM is followed , there is need to check crack width .
A stress of 3.4 kg/cm2 as against 12 kg/cm2 / 18 kg/cm2 is well within and hence rest assured yr section is uncracked as per IS stipulations.
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