Example

Calculate the moment that the section can sustain when combined with an axial load of 2750 kN.

5.2.2.1 Basic method

If the neutral axis is within the section, the compressive force generated by the 4.2.1.3.3 concrete at ultimate limit state is given by Figure 4.2

Rd,c ck and the moment by

The strain at the more compressed face is taken as 0.0035 The procedure adopted is as follows:

(1) Assume a value for x

(2) Calculate/VRdc

(3) Calculate the strain at each steel level

(4) Calculate force generated by reinforcement (A/Rds)

(6) If NR6 is not close enough to 2750 kN, modify the value of x and return to step (2)

(7) If /VRd is approximately 2750 kN, calculate /WRdo and iWRds

The design yield strain for the reinforcement 460

1.15 x 200000

5.2.2.2 First iteration

Assumed value for x is 250 mm

Rd,c

s,top

Rd,s1

s.mid Rd,s2

Rd,s3

Hence

This is considerably less than 2750 kN, hence x must be increased.

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