Practical risk assessment for embankments, dams, and slopes - Risk and Reliability in Geotechnical Engineering - page 448

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 1 2 3

Factor of safety

Figure 11.12 Factor of safety-failure probability for a sliding failure mode of a concrete gravity dam. (From
Altarejos-García, L. et al., 2012. Structural Safety , 36-37, 1-13.)

Step 1. Identify the existing state functions and calculation models
suitable for the failure mechanism and the dam to be analyzed

Step 2. Estimate a physically plausible loading range causing the failure

Step 3. Select a state function, a calculation model, and define which
variables are going to be treated as aleatoric (random)

Step 4. Estimate a statistical distribution of each of the random
variables computing natural and epistemic uncertainties (separately)

Step 5. Select reliability/simulation method to select values of the
random variables

Step 6. Build the “average” fragility curve: select values of random
variables using the natural uncertainty distribution and estimate the
conditional probability of failure for the full range of loading

Step 7. Build the full family of fragility cuerves: select values of
random variables using the epistemic uncertainty distribution and
repeat step 6 maintaining the standard deviation of the natural
uncertainty probability functions

Step 8. Check results and reevaluate all the previous decissions

Figure 11.13 The process to build fragility curves.