Nonlinear analysis. Reserve Factor definition

[Trajano]

Hello,

Lets say that I have a F.E. model of my structure. the structure is made of a material whose ultimate tension allowable stress is Ftu.
I perform an analysis for an ultimate load case and I read the maximum stress Smax.

- If the analysis is LINEAR I would define the reserve factor like this:

RF = Ftu / Smax

if RF is 2, for instance, it means that if I duplicate the applied load I will get a RF = 1.

- If the analysis is NONLINEAR would you still define the RF as Ftu / Smax?
In this case if RF = 2 and I duplicate the applied load I cannot know the new RF unless I perform a new analysis.

My question is: does it still makes sense to define a RF like this? What would be the meaning of such a RF?

 

[ishvaaag]

Limit states design is a complex set of rules the purpose of which is to warrant some devised target of reliable safety and sound service behaviour, of which particular safety factors, material, on loads, overstrength etc are just components of the system. For a simple system, say, a cable in tension, just a simple parameter can be used to state the ratio of the limit load to some applied; for ordinary structures however such simplicity is lost and the aforementioned complexities (a code in itself) need to be addressed to ensure the wanted behaviour, and so it is unlkely any single parameter can properly express the situation.