21 November, 2013

EXERCISE # 1Evaluation of the structural stability of a concrete gravity dam

Scope: To evaluate the effects of uplift control provisions on the structural behavior of a concrete gravity dam.The exercise will be performed individually. The main dimensions of the dam structure are presented in table 1.1. Two cases have to be analyzed:(1) Current static loads, no drainage;(2) Current static loads, drainage drillings;The problem is solved by using the gravity method (rigid body equilibrium and beam theory). The computations are performed by the computer code CADAM version 1.4.3, developed by Department of Civil Eng. at the Ecole Polytechnique de Montreal. By running the CADAM/setup.exe (application) the program CADAM and the pdf file CADAM User Manual become available. The manual may be used for any additional information.Basic data:Launch the CADAM program. From the file menu select New and then the main commend Parameters.Fill up the general information box. Project may be Exercice#l, Dam name may be your free choice, the engineer name has to be your own name and the analysis performer the same.The Parameters options require data concerning Model (the section geometry and material properties), static loads and seismic loads. In the order of the input sequence the basic data are:

I. Section geometry:The notations are the one defined in the interactive screen of the program. The dimensions are listed in table 1.1.

Fig. 1 Section geometry & basic data input window Table 1.1 Section geometryDistanceElevation

L180.00 mElev. point A0

L210.00 mElev. point B3.1

L310.00 mElev. point C0

L48.00 mElev. point D6.1

Elev. point E45.1

Elev. point F85.1

Elev. point G100.1

Elev. point H0

Elev. point I6.1

II. Lift joint material:Create material #1 for lift joint. Use option 2 (without strength drop) to describe the shear strength parameters for concrete (lift joint) and concrete - rock interface (base joint).Table 1.2 Shear strength parametersParameterLift jointBase joint

Peak shearstrengthResidual shearstrengthPeak shearstrengthResidual shearstrength

Cohesion (c)10000

Friction angle ()55455048

Normal compressionstress to mobilize n0000

II. Lift joint generation:In order to simplify the analysis of the output use single lift joint creation as input for the lift joint generation step. Elevation of the selected joint is Elev. point E and Angle = 0. Do not forget to confirm by pushing button "Create'" before OK. Lift joint material is 1 - that means concrete.IV.Static loadsThe static analysis will include only the reservoir water loads. Consequently, provide the reservoir level and the downstream level as follows:Reservoir operating level - upstream =Elev G - 10m;- downstream = 6.1 m (elev I);Reservoir flood level - upstream =Elev G -5m;- downstream = 11.1 m.The second main load is uplift. In order to evaluate the significant effect of the drainage system on the dam stability the analyses (1) and (2) have to be performed.For the first analysis - Case (1)In the dialog window dedicated to uplift specify "NO drainage". No other value has to be provided.For the second analysis - Case (2)In the dialog window dedicated to uplift specify "FES' drainage". The following data have to be added:Drain position from the heel of the dam = 5m.Gallery elevation = 5m.Alternative 2 for the uplift pressure distribution and k2 = 0.25.For the first case follow the steps V, VI and VII as described below. For the second case perform the steps VI and VII as in the case (1). No other modifications are required except the one specified above for the uplift load.V.Load combinationsSelect Load combination from Parameters command bar. In the dialog box select Usual and specify 1 for the Dead load, Hydrostatic (U/S), Hydrostatic (D/S) and Uplift pressure. Do not modify the other options and confirm by pushing OK.VI.AnalysisPerform the analysis by using option Analysis from the command bar followed by Done.

VII. Plot of the results

Select the option Results from the command bar and then Reports. First select Model parameters and print the three pages that describe entirely your model. (For the second case plot only the third page since the first two are not changed as compared to the case 1). Second, select Stability drawings and print the two pages (drawings) that present the stress distribution along the selected joint and along the base joint and the stability factors for the same sections.Case 1 No Drainage

Case 2 Drainage