Ids

surface is at the top of the Figure 10.9. Pad footing on dry sand footing, i.e. the base of the footing is 0.5m below ground level.

The loading is applied centrally to the footing and therefore eccentricity can be ignored. Ground water is also not considered. The example concentrates on the application of the partial factors under the simplest of conditions. In reality, the assessment of a footing would need to consider a number of other situations before a design may be finalized.

Notes on Example 10.1

O In order to concentrate on the EC7 rather than the geotechnical related issues a relatively simple problem has been selected which excludes the effects of groundwater.

© The formulas for bearing capacity factors and shape factors are those given in Annex D. Other formulas could be used where they are thought to give a better theoretical/practical model for the design situation being considered.

© The suggested method in Annex D does not include depth factors which are present in other formulations of the extended bearing capacity formula (e.g. Brinch-Hansen or Vesic). There has been concern in using these depth factors as their influence can be significant and the reliance on the additional capacity provided by its inclusion is not conservative.

© For Design Approach 1, DA1-2 is critical with a utilization factor of 97% implying that the requirements of the code are only just met.

© For Design Approach 2 the uncertainty in the calculation is covered through partial factors on the actions and an overall factor on the calculated resistance.

Example 10.1 Pad footing on dry sand Verification of strength (limit state GEO)

Design situation

Consider a rectangular pad footing of length L = 2.5m, breadth B = 1.5m, and depth d = 0.5m, which is required to carry an imposed permanent action Vfik = 800kN and an imposed variable action Vq^ = 450kN, both of which are applied at the centre of the foundation. The footing is founded on dry sand© with characteristic angle of shearing resistance ^ = 35°, effective kN

cohesion c'k = 0kPa, and weight density Yk = 18-. The weight density of m kN

the reinforced concrete is Yck = 25-(as per EN 1991-1-1 Table A.1).

Design Approach 1

Actions and effects

Characteristic self-weight of footing is Wgk = Yck x L x B x d = 46.9 kN

Actions and effects

Characteristic self-weight of footing is Wgk = Yck x L x B x d = 46.9 kN

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