Consideration of the work of elastic and inertial forces of the foundation when determining seismic loads for the dam of the Kurpsai hydroelectric station

Conclusions

• 1. To take into account the work of elastic and inertial forces it is necessary to include in the calculation scheme a region of the foundation of considerable size (the depth of the calculated region of the foundation should be equal to about (2–3)H, where H is the height of the dam).

• 2. With such consideration of the effect of the foundation it is necessary to examine about 100 modes of free oscillations lying in the frequency range of the first four or five modes of oscillation of a cantilever beam.

• 3. The coefficients η_ik of the mode should be determined by Eq. (25) instead of (2).

• 4. In the presence of modes very close in frequencies (similar to one another within the structure) summation by Eq. (3) leads to a substantial underestimation of the inertial load. In this case the load obtained decreases with increase of the calculated region of the foundation.

• 5. For summation of loads over the modes of oscillations we can recommend Eq. (26), which provides convergence of the solution when the dimensions of the calculated region of the foundation change.

• 6. Correct consideration of the work of elastic and inertial forces of the foundation permits reducing the inertial load. With respect to calculation of the Kurpsai dam this decrease was about 20–30% compared to the load determined by the beam scheme with consideration of elasticity of the foundation by Vogt's method.