ABSTRACT
An overview of the typical problems concerning buttress, hollow gravity and multiple arch/slab dams is presented, emphasizing the support that advanced numerical modeling can provide for the evaluation of their safety and for the definition of the most effective interventions to guarantee long-term safety conditions.
Even if the construction of this type of dams is nowadays practically abandoned, the problem of assessing their safety remains an important and challenging issue considering the obsolescence of most existing structures of this type and the peculiarities connected with their structural behavior, in particular referring to the effects of aging and seismic loadings.
In the Italian context there are numerous cases of this type of works built between the two World Wars and immediately after the II World War. A total of 37 dams are in operation (40% buttress, 30% hollow gravity, 30% multiple arch/slab dams). The problems connected with these structures are well-known: cracks (e.g., caused by phenomena of thermal origin, differences of the buttresses height, expansive chemical reactions, etc.), degradation associated with environmental conditions (e.g., due to corrosion of reinforcement bars when present), and aging. Other criticalities are related to compliance with current legislation which requires the verification of more stringent conditions not foreseen in the design phase (for instance higher seismic loads).
Some of the above-mentioned problems have been investigated in the frame of Benchmark Workshops proposed by the ICOLD Technical Committee A “Computational Aspects of Analysis and Design of Dams”, and are analyzed by an Italian Working Group, established by ITCOLD, the Italian National Committee on Large Dams.
Above all, in this paper the application of the eXtended Finite Element Method to evaluate the propagation of cracks in concrete dams and the seismic reassessment of an Italian multiple arch dam are discussed.
