This paper deals with the nonlinear seismic response characteristics of tall and flexible structures without anchorage system. It is very important for designing the tall and flexible structure to estimate the slipping displacement and the rocking characteristics of the tall structure more precisely due to the earthquake excitation. Reaction and friction forces caused in the supports of the structure are not uniform due to the overturning moment by the horizontal seismic force. Then contact problem should be taken into account. From this point of view, we developed a model for simulating the nonlinear seismic response of the tall and flexible structure including multi contact problem as the unilateral contact problem. The linear complimentarity between contact forces and the relative displacement of supports against the ground was focused and formulated. Numerical simulations on the seismic response of a container crane were carried out as the example of a tall and flexible structure. As the result, it was demonstrated that the seismic response of the container crane is affected by the slip and rocking coupled motion, and the transition between the static friction and kinetic friction.