Hydraulic Structures: Fourth Edition

WAVE FORCES ON COASTAL STRUCTURES 639

With the trough of the clapotis at the wall, the force per unit width is

Fmin (dh 0 H)d. (15.14)

The maximum and the minimum bending moments about the base per
unit width of the wall are

Mmax (dh 0 H)^2  d (15.15)

and

Mmin (dh 0 H)^2 d. (15.16)

In equations (15.13)–(15.16) the effects of the hydrostatic pressure distri-
bution due to the still water have been included. In designing the struc-
ture, account must be taken of any still water behind the structure.
Significant pressures may be developed by the breaking waves on the
wall. The Shore Protection Manual(US Army, 1984) recommends the
method of Minikin (1963); it results in the pressure distribution shown in
Fig. 15.6. It consists of a dynamic pressure peaking at the still-water level
and a hydrostatic pressure due to the wave amplitude. The pressures are in
addition to the hydrostatic pressures of the still water.
The peak dynamic pressure at the still-water level is

pmpb

1

2

^ gH. (15.17)

H



cosh(kd)

g



6

H



cosh(kd)

g



6

H



cosh(kd)

g



2

Fig. 15.6 Pressure distribution on vertical wall due to breaking wave