Concrete gravity dams, forming a quarter of the ICOLD database with over 61,000 dams, often surpass 50 years of service, necessitating increased maintenance and safety scrutiny. Given the aging and advancing seismic safety methods, reevaluating their seismic resilience, considering material degradation and concrete heterogeneity, is imperative. This study conducts a comprehensive seismic fragility assessment of the Pine Flat Dam at lifecycle stages of 1, 50 and 100 years, accounting for material degradation due to aging and uncertainties from concrete heterogeneity. It develops a 2D dam-foundation-reservoir model with fluid-structure-soil interaction and material nonlinearity using the concrete damage plasticity model. The assessment includes 55 ground motions, selected via the conditional mean spectrum method, representing five return periods from 475 to 10,000 years. Fragility curves are developed by fitting a lognormal distribution to failure probabilities at varying intensities. These curves are compared using damage indices like crest displacement and stress at the dam's neck and heel. Aging increases failure probability, correlating with age and return period, as shown by the leftward shift of fragility curves, while concrete heterogeneity adds uncertainty. The results emphasize the critical need for ongoing seismic fragility reassessments, accounting for aging, environmental exposure, and seismic demands on dam safety.
Assessing the potential damage to unreinforced masonry (URM) buildings under soil subsidence is a complex task, due to several factors associated with URM mechanical behaviour and soil-structure interaction. The remarkable variability in material properties of masonry may be further exacerbated by degradation processes, with repercussions on the overall structural response. Furthermore, both in-situ surveys and laboratory tests point out a major role being played by bond pattern effects and strength ratios between masonry constituents on crack formation, distribution and progression. Advanced numerical methods such as those based on masonry micro-modelling might be employed to realistically account for such factors, explicitly incorporating material discontinuities, fragmentation, and collision. In this paper, the Applied Element Method (AEM) is used to simulate the nonlinear structural response and damage of two tuff stone masonry walls with opening, which were experimentally tested under soil settlement in intact and deteriorated conditions. A satisfactory numerical-experimental agreement is found, allowing damage propagation phenomena as well as load redistributions between structural elements to be captured. Such results can then be used as a basis to perform further investigation considering more complex scenarios at structural scale.