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# Equivalent Horizontal Force and P-Delta effects

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## Equivalent Horizontal Force and P-Delta effects

(OP)
Hello.

I am trying to understand the principles of sway of a column. The column is a fixed base cantilever with a heavy axial load and a wind-action as a point-load at the top of the column. No lateral UDL.

I have been doing the maths for the second-order analysis to calculate the sway manually and checking my results against a SkyCiv model, and my results are very close to the Computer Analysis. I have been using the method to calculate the P-delta and P-Delta as described in Appendix 8 of the American Code for steel (B1 and B2 method).

In the Eurocodes, I have to apply an Equivalent Horizontal Force (EQH) to the top of the column which I have also calculated.

My question is on how to deal with the EQH with the sway analysis. Should I include the force ΦNEd into the P-Delta B2 factor or should I calculate the moment created by the force seperately and add it to sum of the moments created by the first and second-order analysis?

Many thanks. Dan

### RE: Equivalent Horizontal Force and P-Delta effects

The RISA manual has a good description of how they use secondary shears (equal and opposite) to create the destabilizing P-Delta moment while maintaining equilibrium.

https://risa.com/risahelp/risa3d/Content/3D_2D_Onl...

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