  In this paper, we study a class of generalized extensible beam equations with
a superlinear nonlinearity \begin{equation*} \left\{ \begin{array}{ll} \Delta
^{2}u-M\left( \Vert \nabla u\Vert _{L^{2}}^{2}\right) \Delta u+\lambda V(x)
u=f( x,u) & \text{ in }\mathbb{R}^{N}, \\ u\in H^{2}(\mathbb{R}^{N}), &
\end{array}% \right. \end{equation*}% where $N\geq 3$, $M(t) =at^{\delta }+b$
with $a,\delta >0$ and $b\in \mathbb{% R}$, $\lambda >0$ is a parameter, $V\in
C(\mathbb{R}^{N},\mathbb{R})$ and $% f\in C(\mathbb{R}^{N}\times
\mathbb{R},\mathbb{R}).$ Unlike most other papers on this problem, we allow the
constant $b$ to be nonpositive, which has the physical significance. Under some
suitable assumptions on $V(x)$ and $f(x,u)$, when $a$ is small and $\lambda$ is
large enough, we prove the existence of two nontrivial solutions $u_{a,\lambda
}^{(1)}$ and $% u_{a,\lambda }^{(2)}$, one of which will blow up as the
nonlocal term vanishes. Moreover, $u_{a,\lambda }^{(1)}\rightarrow
u_{\infty}^{(1)}$ and $% u_{a,\lambda }^{(2)}\rightarrow u_{\infty}^{(2)}$
strongly in $H^{2}(\mathbb{% R}^{N})$ as $\lambda\rightarrow\infty$, where
$u_{\infty}^{(1)}\neq u_{\infty}^{(2)}\in H_{0}^{2}(\Omega )$ are two
nontrivial solutions of Dirichlet BVPs on the bounded domain $\Omega$. It is
worth noting that the regularity of weak solutions $u_{\infty}^{(i)}(i=1,2)$
here is explored. Finally, the nonexistence of nontrivial solutions is also
obtained for $a$ large enough.
