Methods of First order analysis

[matt1989]

Hey guys,

I'm currently studying at university in Australia as a civil engineer and having some confusions with AS4100. For those that are familiar with the standards, my supervisor has told me that there are three methods for determining second order effects using first order methods (that is, moment amplification). Are those three methods the following?

Effective length by idealised end restraints (4.6.3.2)
Effective length by alignment charts (4.6.3.3)
Frame buckling analysis (4.7)

Reason I'm confused is because the equations cross over between the methods, such as determining the elastic buckling load.

Any help would be great as I ma required to explore all 3 methods and then compare them to notional loads and MEP.

 

[csd72]

Msquared48,

Just follow the yellow brick road!

The term supervisor can also apply to the person put in charge of you while you are doing your thesis, so could go either way.

Matt1989,

Its been a while since I have used AS4100 and it appears that it has moved on a bit.

I would suggest you get your hands on a copy of the code commentary as this should explain the rationale behingd the options.

I wouuld be surprised if the three items mentioned are the three ways to do second order analysis as these appear to be all effective axial buckling length estimation. Second order effects are mainly about the additional bending moments induced by the deflections rather than the buckling length (although this is related).

 

[csd72]

It is standards Australia copyrighted material, I suggest you look in your university library, otherwise I would suggest you try you local branch of Engineers Australia if you are a member.