FEM vs CADAM3D

Finite Element Model

Finite Element model
  • Stress, stability and behavior analysis;
  • Better estimation of the stress distribution;
  • Inclusion of non linearity;
  • Modeling of arbitrary sections;
  • State of the art;
  • Level of expertise required: High;
  • Method that requires a lot of time and resources.
  • Post-processor needed to compute key results.

CADAM3D

CADAM3D model
  • Stress and stability analysis;
  • Stresses based on beam theory;
  • Material is homogeneous, isotropic and linear. Cracking of lift joints can however be calculated;
  • More suitable for "regular" sections;
  • Level of expertise required: Medium;
  • Very fast method;
  • Emphasis on the performance indicators along lift joints;
  • Automated processing of many load combinations;
  • Interpretation of results using advanced visualization tools.

Comparison

Sliding safety factors for the seismic case:

This graph presents the sliding safety factors for the seismic case as a function of the elevation of the structure for the two types of modeling presented above. Both methods give similar results while CADAM3D offers more conservative values except for the upper part of the structure. In addition, CADAM3D calculations required about 10 times less engineering time than the finite element method.

What are the disadvantages of finite elements:
  • Finite element analyses require significant resources, expertise, time and a comprehensive validation process;
  • By using finite elements, it is difficult to model:
    (1) the effect of cracking on uplift pressures;
    (2) the reduction of resistance at the level of lift joints;
    (3) the inclusion of fluid elements.
  • The number of cases of loads and load combinations is generally high;
  • Assumptions to simplify the analysis (uncertainties about the loads and the resistances) can be in contradiction with the level of sophistication;
  • Parametric analyzes are frequently required:
    (1) to account for uncertainties about loads and resistances;
    (2) to identify which parameters further influence the results.
  • The analysis times and the processing of the results to obtain the stability indicators are very important and often require in-house post-processors.
Beneficial impacts of CADAM3D:
  • In the majority of cases, the gravity method and pseudodynamic seismic analysis are suitable for stability analyzes;
  • Normalizes assumptions, ensures continuity and robustness of results;
  • Eliminate the use of personal sheets of calculations;
  • Develop a database of dam models;
  • Allows evaluation and rapid response to various questions;
  • Consideration of complex aspects for a better evaluation of the safety of gravity structures (e.g. cracking);
  • Allows standardization from a single software for stability studies;
  • Engineering training and awareness of modeling parameters that can influence the stability of dams.