Footings subject to vertical actions

For a spread foundation subject to vertical actions, Eurocode 7 requires the design vertical action Vd acting on the foundation to be less than or equal to the design bearing resistance Rd of the ground beneath it:

Vd should include the self-weight of the foundation and any backfill on it. This equation is merely a re-statement of the inequality:

Ed < Rd discussed at length in Chapter 6. Rather than work in terms of forces, engineers more commonly consider pressures and stresses, so we will rewrite this equation as:

fwhich also appear in BS 8004.

qEd - qRd where qEd is the design bearing pressure on the ground (an action effect), and qRd is the corresponding design resistance.

Figure 10.4 shows a footing carrying characteristic vertical actions VGk (permanent) and VQk (variable) imposed on it by the super-structure. The characteristic self-weights of the footing and of the backfill upon it are both permanent actions (WGk). The following sub-sections explain how qEd and qRd are obtained from VGk, VQk, WGk, and ground properties.

Figure 10.4. Vertical actions on a spread foundation

10.4.1 Effects of actions

The characteristic bearing pressure qEk shown in Figure 10.4 is given by:

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