  We suggest a new model for the dynamics of a suspension bridge through a
system of nonlinear nonlocal hyperbolic differential equations. The equations
are of second and fourth order in space and describe the behavior of the main
components of the bridge: the deck, the sustaining cables and the connecting
hangers. We perform a careful energy balance and we derive the equations from a
variational principle. We then prove existence and uniqueness for the resulting
problem.
