Dam stability downloaded17 September 2001
A computer program has been developed to provide support for learning the principles of structural stability evaluation of gravity dams
The research group on dam safety at École Polytechnique, University of Montreal, Canada, has developed a computer program for static and seismic stability analysis of concrete gravity dams. Named CADAM (computer analysis of dams), the programme is based on the gravity method using rigid body equilibrium and beam theory to perform a stress analysis, compute crack lengths, and sliding safety factors. Seismic analysis can be performed using either the pseudostatic or a simplified response spectra method.
The development of CADAM, which runs under Windows 95, 98, NT4, 2000 and ME, started in February 1999. A first release of the software was made one year later to the academic community, engineering consulting firms and dam owners located in the province of Quebec, Canada. This release was a beta version (for comments and validation purposes). Since then, further developments have been made to CADAM to improve its capabilities.
The programme has been designed to provide support for learning the principles of structural stability evaluation of gravity dams. It can be used for industrial applications and research and development on the stability of gravity dams. CADAM also provides a fully integrated computing environment with complete output reports and graphic support to visualise input parameters and output performance indicators.
Within the context of training engineering students, CADAM, allows the user to:
•Corroborate hand calculations with computer calculations to develop the understanding of the computational procedure.
•Conduct parametric analysis on the effects of geometry, strength of material and load magnitude on the structural response.
•Compare uplift pressures, crack propagation, and shear strength (peak, residual) assumptions from different dam safety guidelines.
•Study different strengthening scenarios (post-tensioning, earthbacking, buttressing).
CADAM provides an interactive environment for inputting data from the keyboard and the mouse. The output consists of an interactive tabular data and plots that could be quickly reviewed to evaluate the analysis results, together with output file reports that display in tabular and graphical form a synthesis of all results. It also consists of exchange data files that are exported to the spreadsheet program Microsoft Excel to allow further processing of the data and to produce further plots that could be included in other documents.
An incremental load analysis tool has recently been added to enable users to increase a load condition (excluding upstream reservoir elevation) by small increments, and plot the corresponding evolution in related crack lengths, stresses and sliding safety factor.
According to École Polytechnique, there are several possibilities for further developments of a computer program like CADAM for structural safety assessment of gravity dams. Currently, it is planning to add the following features:
•Calculation of seismic sliding displacements and rocking response of cracked dam components using transient dynamic analysis of rigid body.
•Definition of more complex 2D geometry, spillway and water intake sections, eventually 3D sections.
• Arbitrary user defined uplift pressure distributions.
•Link with finite element programs: automatic transfer of model data to finite element programs for detailed static, thermal, seepage and transient seismic analysis of flexible dam-foundation systems.
•Computation of static and thermal displacements using beam theory for the dams and Boussinesq coefficients for the semi-infinite elastic foundation. Thermal analysis will be performed along lift joints using finite differences to evaluate the thermal fields.
The development of CADAM was funded by the National Sciences and Engineering Research Council of Canada, Hydro-Québec and Alcan.
CADAM is freeware and can be downloaded from http://www.struc.polymtl.ca/cadam/. To date more than 300 copies have been downloaded.