  Pure N-body high-resolution re-simulations of 13 massive dark matter halos in
a Lambda-CDM cosmology are presented. The resulting sample is used to
investigate the physical origin of the Fundamental Plane, ``Faber-Jackson'',
and ``Kormendy'' relations observed for nearby galaxy clusters. In particular,
we focus on the role of dissipationless hierarchical merging in establishing or
modifying these relations. Contrarily to what found in the case of the
Faber-Jackson and Kormendy relations for galaxies (see Londrillo, Nipoti and
Ciotti, this conference), dissipationless merging on cluster scales produces
scaling relations remarkably similar to the observed ones. This suggests that
gas dissipation plays a minor role in the formation of galaxy clusters, and the
hierarchical merger scenario is not at odd with the observed regularity of
these systems.
