DURABILITY

MINUMUM CONCRETE COVER (EXPOSURE CONDITION)

MINIMUM MEMBER DIMENSIONS AND COVER

(FIRE RESISTANCE)

Example 6.1

Simply supported R.C beam designed with C25/30 concrete. It is estimated that the beam will have overall thickness of 200 mm and 10 mm diameter reinforcing bars will be used as the main reinforcement.

Check the cover requirements for durability, bond and fire resistance if the required fire resistance is 90 minutes. Also determine the effective depth that would be used in the design of the beam.

Exposure Class

The beam is part of an internal structure therefore in a dry state. From Table 5.5: Exposure Class = XC1

a) Durability

From Table 4.4N : cnom = cmin + cdev; cnom = 15+10 = 25 mm

b) Bond

The nominal cover to ensure adequate bond conditions

= bar diameter + 10 = 10 + 10 = 20 mm (