The deformation of the structure
Second analysis results: The displacement of the crossbar at the 3^{rd} level, due to horizontal force H=100.0 kN, is δ_{3,2}=1.399 mm, therefore its stiffness yields K_{3,1}=H/δ_{3,1}=100.0·10^{3}N/(1.399·10^{-3}m)=71.5·10^{6} N/m.
The following elastic displacements δ_{i,1} and stiffnesses K_{i,1}_{ }are obtained from similar analyses applying force H=100 kN separately on each floor i.
4^{th} level: H=100 kN, δ_{4,2}=2.783 mm, K_{4,2}=35.9·10^{6} N/m
3^{rd} level: H=100 kN, δ_{3,2}=1.399 mm, K_{3,2}=71.5·10^{6} N/m
2^{nd} level: H=100 kN δ_{2,2}=0.543 mm, K_{2,2}=184.0·10^{6} N/m
1^{st} level: H=100 kN, δ_{1,2}=0.117 mm, K_{1,2}=855.0·10^{6} N/m
In the example considered, at the 3^{rd} level, the stiffness obtained using finite element modelling is (71.5-64.4)/64.4=11% higher, while at the 4^{th}, 2^{nd} and 1^{st} level 9%, 16% and 25% higher, respectively.
Conclusion: The frame stiffness slightly differs when walls are modelled with two-dimensional finite elements.