Page - 1120 - in Book of Full Papers - Symposium Hydro Engineering

Fig. 3 Liquefaction potential evaluation based on SPT tests at Ruppoldingen HPP [after 8,9] Computation procedures for water-retaining structures The Guidelines require to setup a 3D FE model which includes one pier and a left and right half field of the weir structure and the extended sub-soil. The actions of non-modelled elements such as bridges and gates are implemented in order to consider a realistic dynamic behavior for the SSA. The water-structure inertial interaction is modelled by introducing additional incompressible masses on the structure according to Westergaard’s method (Fig. 4). The bedrock mass is neglected, therefore only the soil-structure kinematic interaction is considered in the model. The powerhouse for both HPPs, as a water-retaining structure, is modelled also with a 3D FE model. The radial gates of the weir were manually back-calculated with the updated load cases, thanks to the available steel- structural analyses reports from the original design phase. Material parameters The Enforcement Guideline requires as a minimum the static characterization of the structural and geotechnical materials based on laboratory or in-situ tests. These are also accepted if available from the construction time. Required parameters for example would be concrete compression strength, reinforcement density and sub-soil seismic wave velocities. Structural dynamic characterization of the materials is obtained either from specific dynamic laboratory tests or derived from the static values, e.g. for concrete based on following empirical relationships for the elastic modulus Ed = 1,25 Es, compressive strength fcd = 1.5 fcs and tensile strength ftd = 1,5 fts ≤ 4 MPa. In general, the weir body and the sub-soil are modelled as linear-elastic, isotropic with viscous damping (e.g. 7% for reinforced concrete). 1120