Chapter 6 

 DAMAGE AND ERODED PROFILE PREDICTION 



6.1 Damage Variability 



Figures 5.10-5.12 indicated that the standard deviation of damage S 

 varying along the structure increases with mean damage S. Figure 6. 1 shows the 

 relationship between o^ and 5 for all data in the three series plotted in Figures 5.10 - 

 5.12. The scattered data points for the three series may be represented by the relation 



(6.1) 



which is the solid curve shown in Figure 6. 1. This relation implies that damage 

 variability along the structure increases with the mean damage. On the other hand, 

 relative variability defined as the coefficient of variation V^ = a^/^ decreases with 

 increasing S. This implies that higher damage levels may be estimated with smaller 

 relative errors. The correlation coefficients for the three series for Equation 6. 1 were all 

 r = 0.99. An example of the use of Equation 6. 1 is illustrated for 5^ == 1 3 at failure of 

 Series A'. Substituting S= 13 into Equation 6.1 yields a^ = 2.65. The approximate 

 range of -2.7 < 5* < 3 in Equation 5.10 corresponds to 6 < 5 < 21, indicating damage 

 variability of a factor of 3.5 along the structure. 



110 



