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Stress in concrete

Strain

Stress in concrete

Figure 5.2 Conditions in section for Example 2

The technique adopted for the calculation of Narl and M0rl is to calculate the nQ,C nQ,C

effect of the stress block on a depth of 600 mm and then deduct the influence of the part lying outside the section.

5.2.3.2 Concrete forces and moments

The equations for the full stress block are: = °'5667(1 -

Note:

It will be found that, if eu = 0.0035, these equations give the values used in the first example.

The equations for the force and moment produced by the part of the stress block lying outside the section are

where

eb = strain at bottom of section From the strain diagram, eb = 0.00051 Hence a = 0.255 and 0 = 0.645

/V'Rdc = 0.5667(1 - 0.645/3) x 350 x 600 x 30/1000 = 2802 kN

600(0.6452 - 4 x 0.645 + 6) c = 250 ----' = 5.67 mm

Hence

AA/Rdc = 0.5667 x 0.255(1-0.255/3)(600 -500)350 x 30/1000 = 139 kN

0 0

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