Abstract We deal with hyperbolic variational inequalities modeling vibrations of two-dimensional structures with an obstacle. We focus on the plates with moderately large deflections. The nonlinear strain-displacements relations imply nonlinear elliptic parts of differential operators in considered problems.We distinguish two types of problems. In the first case only the deflections are considered with accelerations and the plane displacements are expressed using the Airy stress function. In the case of plane accelerations the full von K´arm´an system consisting of two equations and one variational inequality is considered. The existence of solutions is derived using the penalization method.