EN1993 & EN1998 2nd order effects for seismic

[mohamed abdel aziz]

hello everyone,
in EN1993 5.2.2 structural stability of frames we are allowed to run first order analysis and amplify the horizontal loads if
alpha_cr is <10 and >3 my question is do we also amplify seismic forces in that case or not
considering that there is another condition for amplifying seismic forces in EN1998 4.4.1(2)
where theta is between 0.1 and 0.2
my understanding is we only amplify only wind and equivalent loads based in the alpha_cr condition and amplify seismic forces only based on the second condition so there will be cases where for instance seismic forces are amplified but not wind and EHF and vice versa.Can someone confirm this ? thanks in advance

 

[HTURKAK]

I want to respond with explicit wording;

θ= sensitivity factor to relative displacement between storeys ( equation 4.28)

IF ;
- θ ≤ 0.1 ; It is not necessary to consider P-Δ effects.

- 0.1 < θ ≤ 0.2 ; P-Δ effects could be taken into account approximately by amplifying the effects of the seismic actions by 1/(1 – i).

- 0.2 < θ ≤ 0.3 P-Δ effects must be taken into account by an analysis including second order effects explicitly.

- θ > 0.3 Not permitted. Change the sizes of SFR elements .

There is a worked example at the following doc.

I hope my respond answers your question .





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Make it do, or do without.

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[mohamed abdel aziz]

many thanks HTURKAK it is very clear now