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2 2023

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Impact of material nonlinearity of dam-foundation rock system on seismic performance of concrete gravity dams

Ouzandja Djamel, Messaad Mokhtar, Berrabah Amina Tahar, Belhrizi Mohamed

Journal of Theoretical and Applied Mechanics

2023

Vol. 61 nr 1

49--63

This paper shows the impact of material nonlinearity of a dam-foundation rock system on seismic performance of Oued Fodda concrete gravity dam, located at northwestern side of Algeria. For the purpose, a three-dimensional dam-foundation rock system finite element model is employed in analyses. The hydrodynamic interaction between reservoir water and dam-foundation system is implicitly taken into consideration by the Westergaard approach using surface finite elements added to dam-fluid and foundation-fluid interfaces. The concrete material model is used to present the cracking of dam concrete under a seismic load the using smeared crack approach based on the Willam and Warnke failure criterion. The materially nonlinear analysis for both dam concrete and foundation rock is performed using Drucker- -Prager model. According to numerical results, tensile stresses and maximum strains reduce significantly in the materially nonlinear model. In addition, the cracking areas in the dam decrease also when material nonlinearity characteristics of the dam-foundation rock system is considered in analyses.

Seismic analysis of Fractured Koyna Concrete Gravity Dam

Ouzandja Djamel, Messaad Mokhtar, Berrabah Amina T., Belharizi Mohamed

Archives of Hydro-Engineering and Environmental Mechanics

2023

Vol. 70, nr 1

29--47

Seismic analysis of a fractured dam is a generally complex problem. This paper presents an earthquake behavior investigation of a fractured concrete gravity dam considering dam-reservoir-foundation rock interaction. The Koyna dam profile, located in India, is adopted in this study. The nonlinear finite element analyses are conducted taking into account empty and full reservoir cases, to exhibit the hydrodynamic effect of reservoir water on the dam earthquake response. The hydrodynamic pressure is modeled by fluid finite elements based on a Lagrangian approach. Transient analyses take into account material and connection nonlinearity. Drucker-Prager model is employed in nonlinear analyses for the dam concrete and foundation rock. The structural crack between the top and bottom blocks of the dam is presented by surface-to-surface contact elements based on Coulomb’s friction law in order to simulate the behavior of contact joints and deformation of blocks. The distribution of horizontal displacements and principal stresses along the dam height is investigated for empty and full reservoir cases.The failure processes of two potential failure modes of cracked dam, i.e, the separation and sliding of top block during an earthquake, are examined.