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The CIRIA Guide Simple Rules apply where the intensity of any load is less CIRIA than 0.2fcu and the load is applied over a length which exceeds 0.21. More Guide 2 intense loads and those applied over shorter lengths are considered to be CI.2.3.1(5) 'concentrated', in which case reference should be made to the Supplementary Rules in the Guide.

To allow for design to EC2 where different values and concrete strength classes are used, the check for load intensity might reasonably be made against

r CU CK CK

Ultimate concentrated top load = 1.35 x 475 = 641 kN Allowing for 45° spread of load through thickness of slab Load intensity = 641 x 103/(800 x 300) = 2.67 N/mm2

This loading is well below 0.23f,k but, because the length of the loaded area is less than 0.2/ = 0.2 x 5750 = 1150 mm, some additional reinforcement may be required and must be calculated using the Supplementary Rules in the CIRIA Guide.

11.2.6 Moment and shears

11.2.6.1 Reactions due to loads on clear span

The arrangement of loading and supports assumed for calculating the bending moments is shown in Figure 11.4. These loads are for the fully loaded system.

CIRIA Guide 2 CI.2.3.2

1 35X 475 kN

1 35X 309 kN/m

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