Assoc. Prof. Dr. Tarkan Erdik Arch Dams (Kemer Barajlar) Assoc. Prof. Dr. Tarkan Erdik Department of Civil Engineering, I.T.U

Arch Dams An arch dam may be defined as a solid and curved wall standing across the entire width of the river valley. Materials used: Concrete (mostly) Rubble and stone masonary (in the past). Features: Thinner and requires less material than any other type of dam. Used only in narrow canyons

Arch dams are constructed as a system of monolithic blocks separated by vertical joints. The joints are later grouted under high pressure to form a complete monolithic structure in compression (USBR 1977).

Arch Dams Curved in plan and carry most of the water thrust horizontally to the side abutments by arch action. A certain percentage of water load is vertically transmitted to the foundation by cantilever action.

The arch load will, thus be transferred to the side walls of the canyon, which must be strong, stable and rocky.

a) Series of horizantal arches b) Series of vertical cartilevers. G F E D C B H 1 2 3 4 5 6 7 a) b) a) Series of horizantal arches b) Series of vertical cartilevers.

Oymapınar dam (Manavgat)

Deriner dam (Çoruh)

Constant Radius Arch Dam (variable angle) Good for U-shaped valleys Easy construction Vertical upstream face Appropriate for middle-high dams

In simplest term, the upstream face is vertical so that at all elevations its radius is constant but thickness is proportinal to the height.

Variable Radius Arch Dams (constant angle) Good for V-shaped valleys Limited to the ratio of B/H=5 Best center angle: 133034´ To obtain arch action at the bottom parts r1 r2 r3 r4

V shaped valley

Variable Center –Variable Angle Arch Dams Combination of the two above. Its calculation based on shell theory applied toarch dams

We have to determine forces acting vertically on a projected area of the arc 1st boundary:/2-a/2 Referance axis 2st boundary:/2 Equilibrium of forces in the flow direction (y): Ry: reaction force at the sides in y direction [= R sin (θa/2)]

Arch Dams (design principles) The volume of concrete for a single arch: L V = Ltk k t The volume of concrete for unit height for a single arch V = L t

L: arch length (L = r θa) (note that θa is in radians)

L