“…For classical results obtained on elastic beam equations we refer to [6,12,14,15,38,44], in particular [44] is one of the pioneering works on extensible beams), while [12] settles the existence and multiplicity question for (P f ) in the physical situation p = 2, ρ = 0 and M of the form M (s) = as + b. Recently, the existence of solutions to fourth-order boundary value problems have been studied in many papers and we refer the reader to the papers [8,9,20,22,26,28,29,30,31,36] and the references therein. For example, Candito and Livrea in [9] by using critical point theory, established the existence of infinitely many weak solutions for a class of elliptic Navier boundary value problems depending on two parameters and involving the p-biharmonic operator.…”