If the span/effective depth ratio is modified using the service stress in the reinforcement as calculated in Section but adjusted for the frequent load combination a = 188.5 x 31.4/25.6 = 231 N/mm2

^ (allowable) = 28 x 0.8 x = 21.6 > 18.0 (actual)

It can be seen from this example that whilst the span/effective depth ratio based on the calculated steel service stress suggests that the deflection should be well within the prescribed limits, the deflection from the rigorous and simplified analysis proves to be much nearer to the limit of span/250.

This is due to the contribution to the deflection from shrinkage, which in this example is approximately a third of the total deflection.

The values of shrinkage strain given in EC2 Table 3.4 relate to concrete having a plastic consistence of classes S2 and S3 as specified in ENV 206<6). For concrete of class S1 and class S4 the values given in the Table should be multiplied by 0.7 and 1.2 respectively.

Table 4 of ENV 206 categorises the class in relation to slump as given in Table 10.3.

Table 10.3 Slump classes


Slump (mm)

0 0

Post a comment