Worked Example 3.3
The profile of the major monolith of a buttress dam is illustrated in Fig.
3.24. The stability of the dam is to be reviewed in relation to updated
design criteria.
Normal load combination (NLC).Water load (to design flood level
(DFL))self-weightuplift (no pressure relief drains).
Static stability.Overturning,FO1.5; sliding (shear friction factor),
FSF2.4.
Concrete characteristics: core samples.Unit weight, (^) c23 kN m^3 ;
unit shear resistance, c500 kN m^2 ; angle of shearing resistance (internal
friction),c35°.
WORKED EXAMPLES 185
Fig. 3.24 Worked example 3.3
- Analyse the static stability of the buttress unit with respect to plane
X–X under NLC and in relation to the defined criteria for FOandFSF. - Concern is felt with regard to stability under possible seismic
loading. Dynamic stability criteria are specified as FO2.0;FSF3.2,
and will be met by prestressing as shown. Determine the prestress
load required in each inclined tendon.
Solutions
- All calculations relating to stability refer to the monolith as a com-
plete unit. Uplift is considered to act only under the buttress head,
and the profile is subdivided into the elements A, B and C, identified
in Fig. 3.24, for convenience. The load–moment table (all moments
are relative to toe) is as follows: