A two-stage procedure was proposed in 1978 for the analysis phase of elastic design and safety evaluation of concrete gravity dams: (I) a simplified analysis procedure in which the response due only to the fundamental vibration mode is estimated directly from the earthquake design spectrum; and (2) a refined response history analysis procedure for finite element idealizations of the dam monolith. The former was recommended for the preliminary design and safety evaluation of dams, and the latter for accurately computing the dynamic response and checking the adequacy of the preliminary evaluation. In this report, the simplified analysis procedure has been extended to include the effects of dam-foundation rock interaction and of reservoir bottom sediments, in addition to the effects of dam-water interaction and water compressibility included in the earlier procedure. Also included now in the simplified procedure is a \"static correction\" method to consider the response contributions of the higher vibration modes. Thus, the design procedure proposed in 1978, which is still conceptually valid, should utilize the new simplified analysis procedure.

Simplified analysis for earthquake resistant design of concrete gravity dams.

A hybrid model formed by partitioning a soil~structure system into a near-field and a far-field has been successfully exploited in the analysis of three dimensional soil-structure interaction problems. The near field which consists of the structure and a finite region of soil around it is modelled by the finite element method. The far-field which accounts for the loss of energy due to stress waves travelling away from the foundation is modelled through continuous impedance functions. The main purpose of this investigation is to complement the previous research on three-dimensional hybrid modelling by employing the same tecp~ique to the two-dimensional case. To determine the two-dimensional frequency dependent impedance functions, a method of system identification is used to insure that the resulting hybrid model reproduces the known compliances of an infinite rigid strip on an elastic halfspace. These impedance functions have been employed to calculate the compliances of the strip for different Ria ratios. Good agreement between the computed and known compliances is shown.

S. W. Zagajeski

Papers

Optimum inelastic design of seismic-resistant reinforced concrete frame structures