Abstract

Gravity dams are critical infrastructure for hydropower generation, water supply, irrigation, and flood control. However, their large mass and rigid geometry make them particularly vulnerable to seismic loading. The failure of such dams during earthquakes can result in catastrophic consequences, including loss of life, downstream infrastructure damage, and long-term environmental disruption. In regions of moderate seismicity like Eastern Canada, the risk is often underestimated due to limited historical damage records. This study addresses that gap by evaluating the seismic behavior of two concrete gravity dams using nonlinear finite element modeling techniques, with a specific focus on tensile cracking and structural degradation.
The investigation employed ABAQUS software to simulate the seismic response of concrete gravity dams under combined hydrostatic and earthquake loads. The Concrete Damaged Plasticity (CDP) model was used to represent the nonlinear behavior of concrete, including cracking, crushing, and stiffness degradation. Model validation was performed using the well-documented Koyna Dam in India, which experienced significant damage during the 1967 Mw 6.5 earthquake. The validation process involved modal analysis, crest displacement comparison, and tensile damage correlation to ensure the model's reliability before applying it to Canadian Dams.
Following validation, the same modeling approach was applied to two dams in Eastern Canada, Dam D1 (35 meters high) and Dam D2 (90 meters high) with consistent material properties. Both dams were assumed to have fixed bases, and soil-structure interaction effects were not explicitly included. A total of 22 ground motion records from the 1988 Mw 5.9 Saguenay Earthquake, collected from 11 recording stations, were used as seismic loading. Each record included both longitudinal and transverse components and was scaled to the design-level spectrum to simulate high-magnitude scenarios and observe potential damage thresholds.
The results revealed distinct differences in seismic response between the two dams. Dam D1, being shorter and stiffer, exhibited limited crest displacements and minor, localized tensile cracking, mostly at the upstream heel. In contrast, Dam D2 experienced significantly higher crest displacements exceeding 100 mm in several simulations. And widespread tensile damage at both the crest and the base, especially under scaled acceleration records. The spatial and temporal patterns of damage indicated classic flexural behavior, with tension developing at the crest and heel due to cantilever action and stress wave reflection
These findings underscore the critical influence of dam geometry, mass, and natural frequency characteristics on seismic performance. The results emphasize the need for modal analysis in preliminary seismic safety assessments and demonstrate the value of nonlinear modeling techniques in capturing progressive damage. By applying realistic earthquake inputs from within the region, this study contributes to a better understanding of dam vulnerability in Eastern Canada and provides a framework for future seismic assessments and retrofit prioritization.