A finite-element analysis is made of the stability and supercritical behavior of a steel I-beam with a thin flexible web. The evolution of the stress-strain state of the beam is analyzed with allowance for the joint work of the web and ribs. A method is proposed for obtaining solutions after branching occurs. The qualitative change in the stress state in the web during instability is studied in detail, it being found that one-way supercritical bifurcation occurs, i.e. the branched solutions are stable. Numerical analysis showed that the beam moves to the branch of the equilibrium path when the load exceeds the critical value. However, the beam can still sustain some increase in load after this point.
Translated from Problemy Prochnosti, No. 11, pp. 79–88, November, 1994.