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4.1.2.1.6 Serviceability - deflection

Control by limiting span/effective depth ratio based on the shorter span for a 4.4.3.2 two-way spanning slab.

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NAD Table 7 gives basic span/effective depth ratios which are assumed to be 4.4.3.2(4) based on f. = 400 N/mm2.

Note 2 to NAD Table 7 states that modification to the tabulated values for nominal reinforced concrete should not be carried out to take into account service stresses in the steel (refer to EC2 Clause 4.4.3.2(4)). However, it is assumed that the correction ought to be made for concrete with 0.15% < p< 0.5% but that the resulting values should not exceed those tabulated in the NAD for nominally reinforced concrete.

Basic limiting span/effective depth ratios are:

Concrete lightly stressed (p = 0.5%): 25

Concrete nominally reinforced (p = 0.15%): 34 By interpolation at p = 0.33%: 29.4

The actual service steel stress modification factor is

250 a

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