Bearing Capacity and Shallow Foundations - Elements of Soil Mechanics - page 269

Fig. 9.9 Strip foundation with inclined load.

where

P = magnitude of the eccentric load
W = self-weight of the foundation
e p = eccentricity of P.

Inclined loads

The usual method of dealing with an inclined line load, such as P in Fig. 9.9, is to first determine its hori-
zontal and vertical components P H and P V and then, by taking moments, determine its eccentricity, e, in
order that the effective width of the foundation B ′ can be determined from the formula B ′ = B − 2e.
The ultimate bearing capacity of the strip foundation (of width B) is then taken to be equal to that of
a strip foundation of width B ′ subjected to a concentric load, P, inclined at α to the vertical.
Various methods of solution have been proposed for this problem, e.g. Janbu ( 1957) , Hansen ( 1957) ,
but possibly the simplest approach is that proposed by Meyerhof ( 1953 ) in which the bearing capacity
coefficients N c , N q and N y are reduced by multiplying them by the factors i c , i q and i γ in his general equa-
tion (10). Meyerhof's expressions for these factors are:

i

= = −

i ( 1 α / 90 ° )

2

c

i γ = − ( 1 α φ / )

2

9.7 Designing spread foundations to Eurocode 7

The design of spread foundations is covered in Section 6 of Eurocode 7, Part 1. The limit states to be
checked and the partial factors to be used in the design are the same as we saw when we looked at the
design of retaining walls in Section 8.5.

9.7.1 Design by calculation

In terms of establishing the bearing resistance, the code states that a commonly recognised method should
be used, and Annex D of the Standard gives a sample calculation. Depth factors are excluded in Eurocode
7 and for this reason they are excluded too from the solutions to Examples 9.5 and 9.6 in this chapter.
Spreadsheets Example 9.5. xls and Example 9.6. xls , however, offer the choice whether to include the depth
factors or not.