A schematic illustration of the internal variation of these stresses on the
basis of gravity method analysis is provided in Figs 3.7(a)–3.7(e). The com-
parison between Figs 3.7(a) and 3.7(f ) will be noted.
Uplift load is excluded from the equations for stress determination
set out in this section. It can, if necessary, be accounted for by superposi-
tion of local uplift pressures onto calculated stresses (Zienkiewicz, 1963;
Moffat, 1976). In practice the influence of internal uplift upon stress pat-
terns is generally disregarded other than in relation to possible horizontal
cracking (Section 3.2.5).
(a) Vertical normal stresses
Vertical normal stresses on any horizontal plane are determined by appli-
cation of the equation for cantilever action under combined axial and
bending load with suitable modifications, i.e.
z
∑
A
V
h
∑M
I
*y
(3.31)
144 CONCRETE DAM ENGINEERING
Fig. 3.7 Internal stress distribution: gravity method analysis (after USBR,
1976)
