Are properties of the structure independent in each part?

Dear all,

I am doing some research on modeling of uncertainty in computational mechanics.

My question is: Are properties of the structure independent in each part of the structure?

I check some examples and discover that sensitivity in some structures is quite big.

Example 1 In this truss structure if we change the forces in 5% then the results chance in 100 %.

Example 2 In this truss structure if you change the forces in 5% then the results chance in 60 %.

Example 3

In these examples I calculated the worst case (i.e. I did not apply any probabilistic assumptions). Only force were uncertain however in reality also other parameters may be diffrent from bar to bar.

Let us assume that we have some truss structure. In reality properties of each particular bar (Young modulus and cross-section ect.) may be in each bar different.

My question is: How realistic is the assumption that the properties in each bar (for example Young modulus and cross-section) may be different?

Maybe in realistic structures it is better to assume that, there is some kind of correlation between properties of different bars?

In other words: How realistic are the results of worst case analysis in this case?

As far as I know, there is no publicly available probabilistic data (I should rather say no data at all) which corresponds to this problem. In this situation calculation of the worst case is in may opinion quite reasonable solution.

Maybe some member of this group has some opinion about that problem.

Regards,

Andrzej Pownuk

--------------------------------- Ph.D., research associate at: Chair of Theoretical Mechanics Faculty of Civil Engineering Silesian University of Technology URL:

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