The Simplified Linear Dynamic Analysis Method is used for the estimation of earthquake induced stresses in the dam monolith based on Equivalent Static Force, also known as Simplified Response Spectrum Method (Fenves & Chopra 1987) or Pseudo-Dynamic Method (Leclerc, Leger and Tinawai, 2003).

The procedure involves the calculation of the equivalent static lateral forces due to the fundamental mode, to be applied on the upstream face of the dam monotonically to incorporate the earthquake effects. Further, the higher mode effects are incorporated through static correction factor. The resulting stresses in the dam monolith under the influence of the applied equivalent forces are computed using the traditional beam theory.

Salient Features of the Simplified Linear Dynamic Analysis Method

1. Idealisation: Equivalent Single-Degree-of-Freedom idealization of the dam–water–foundation (rock) system (i.e. Generalised coordinate approach).
2. Effective Period: Period elongation due to water and foundation rock interactions.
3. Effective Damping: Added damping due to water and foundation interactions.
4. Higher Mode Effects: Correction factors from rigorous frequency domain analysis using substructure approach.
5. Modal Combination Rule: The Square Root of Sum of Squares (SRSS) is used.
6. Peak Response: Estimation of peak response is in terms of earthquake induced stresses in the dam monolith based on Equivalent Static Force, from Response (or Design) Spectra and traditional beam formula.
7. Total Response: The total response includes the static responses due to, effect of self-weight, hydrostatic pressure etc. be computed by standard method, and shall be combined with earthquake response.
8. Suitability: Preliminary Design and Initial Level Safety Evaluation.