How to simulate bifurcation due to buckling for a simply supported beam using ABAQUS?

I want to capture bifurcation phenomenon observed during buckling for a simply supported beam using ABAQUS simulations.

I have performed linear perturbation analysis to extract mode shapes and critical buckling load. Model consisted of 100, B21 elements.

Then I have modelled a similar beam with imperfection equal to 1st mode shape with amplitude of 1e-8.

After performing multiple static analysis with load varying from 95 N to 105 N with step of 0.5 N (critical buckling load of the beam being 100 N for 1st mode shape), the deformation produced in the beam was proportional to the load applied.

It is expected that there should be a substantial increase in deformation once the load applied crosses buckling load. But this is not happening!

Could someone please suggest an analysis procedure to capture bifurcation phenomenon?

How to simulate bifurcation due to buckling for a in simply supported beam using ABAQUS? - ResearchGate. Available from: https://www.researchgate.net/post/How_to_simulate_bifurcation_due_to_buckling_for_a_in_simply_supported_beam_using_ABAQUS [accessed Aug 20, 2015].