The dual variational principle and equilibria for a beam resting on a discontinuous nonlinear elastic foundation

The dual variational principle and equilibria for a beam resting on a discontinuous nonlinear elastic foundation M.R. Grossinho a;b;∗;1, St.A. Tersian c;2 a Departamento de Matem atica, ISEG, Universidade T ecnica de Lisboa, Rua do Quelhas, 6, 1200 Lisboa, Portugal b CMAF, Universidade de Lisboa, Av. Prof. Gama Pinto, 2, 1699 Lisboa Codex, Portugal c Center of Applied Mathematics and Informatics, University of Rousse, 8 Studentska str., 7017 Rousse, Bulgaria