Load Moment Vertical (kN) Horizontal Moments
arm (m) (kN) (kN m)
←↑ ↑ ↓
→
Water:
horizontal – 6.66 – – 20 000 133 330 –
vertical 18.33 – – 02 000 – – 036 660
Uplift 18.00 – 3000 – – 54 000 –
A 15.50 – – 01 380 – – 021 390
Self-weightB 16.50 – – 13 800 – – 227 700
C 10.00 – – 11 040 – – 110 400
∑ 3000 28 220 20 000 187 330 396 150
Equation (3.19):
FO 2.11 (satisfactory).
Equation (3.25):
FSF 2.83 (satisfactory).
- Seismic criteria, FSF2.83 unsatisfactory (3.2); prestress load/but-
tressPps; inclination to vertical, tan u0.10;u5.7°. From equa-
tion (3.41),
FSF3.20
FSF3.20
givesPps7230 kN per buttress3615 kN per tendon.
Worked Example 3.4
A constant-radius cylindrical arch dam with a vertical upstream face is to
be constructed in a symmetrical valley. The idealized valley profile consists
of a trapezoid with a base 50 m wide and sides at 45°. The base is at 100 m
AOD, the spillway crest at 140 m AOD. Design flood level (DFL) will be
1.0 m above the full length crest spillway, which has a structural thickness
of 1.5 m. The maximum permitted horizontal arch stress, assumed uniform
through the arch thickness, is 2.5 MN m^2.
- Select a suitable geometry in plan and determine the crest level arch
stress under DFL conditions.
500 78 (25 220Pps0.99)0.70
20 000 Pps0.10
cAh(∑VPpscosu)tan
∑H Ppssinu
500 78 25 2200.70
20 000
cAh∑Vtanc
∑H
396 150
187 330
∑M
∑M
186 CONCRETE DAM ENGINEERING
