Crack_width of Flexural RC Members-ICJ-Nov05

2005 * The Indian Concrete Journal 1

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N. Subramanian

The Indian Concrete Journal * 20052

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Table 1: Tolerable crack widths according to ACI 224R-80, CEB-FIP model code and IS code

Sl.No. Exposure condition Tolerable crack widths, mm

ACI 224 R-80 CEB – FIP IS 456 : 2000

1 Low humidity, dry air or 0.40 0.4 – 0.6 0.30

protective environment

2 High humidity, moist, 0.30 0.2– 0.3 0.20

air, soil

3 Deicing chemicals 0.2 0.10 – 0.15 0.10

4 Sea water and sea water 0.15 0.10 – 0.15 0.10

spray

5 Water-retaining structures 0.10 – –

* Lower crack width limit is for cases with minimum cover; upper limit = 1.5 × minimumcover.


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Table 3: Spacing and bar size for skin reinforcement

Depth, d, mm Maximum spacing, Minimum bar area, Ab , at maximum

Ssk, mm spacing, mm2

900 150 22.5

1050 175 52.5

1200 200 90.0

1500 250 187.50

1800 300 315.0

2100 300 405.0

Table 2: Comparison of spacing of reinforcement, mm

Stress, As per Clear cover, mmMPa equation no 20 25 30 35 40 45 50 75

fst = 250 5 300 300 300 292 280 267 255 1926 300 300 300 287 275 262 250 187

fst = 275 5 273 275 270 258 245 233 220 1586 273 273 265 253 241 228 216 153


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Crack_width of Flexural RC Members-ICJ-Nov05

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