A 9 year field program was undertaken from 19911992 to 19992000 to (i) measure the loads in the ice sheet near a dam, (ii) measure the load distribution between a gate and a pier, and (iii) compare the loads on wooden and steel stoplogs. Parallel work was conducted to develop analytical predictors for ice loads. Much progress has been made. One of the most significant findings has been to identify the importance of water level changes on the resulting ice loads. Ice loads are much higher and more variable (compared to purely thermal loads) when significant, but not excessive, water level changes occur. Methods have been developed to predict the ice load. The algorithms predict thermal loads well. They are less accurate for loads produced by a combination of water level and ice temperature changes. An environmental model was developed, and the predictions using the model compare well with the measured data. Hindcast analyses were carried out to evaluate the distribution of expected ice temperature changes and thermal events. With respect to the loads on gates and stoplogs, an analytical method was developed to extend the results obtained in this project to other stoplog or gate configurations (i.e., spans, flexural rigidities, etc.) and pier lengths.Key words: ice loads, dam(s).
It is important to anticipate potential maximum ice loads to ensure the structural stability of dams in cold climates. Finite element modeling (FEM) can provide some insights into process mechanisms. Four important ice-loading events on dams are presented and simulated. The measured loads were caused by the thermal expansion of ice together with intermediate water level fluctuations. Only the thermal expansion is modeled by the FEM, but the impact of water level fluctuations can increase lateral confinement that increases the predicted load by 36% to 106%, particularly when the cover contains mostly columnar ice. It is demonstrated that the presence of snow ice in the cover can decrease the predicted load by 35% to 53%. The study also demonstrates how initial stresses in the ice can affect the ultimate load and show that the very-difficult-to-manage delayed-elastic strain term need not be included in the material model where preliminary results suffice.
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