This paper discusses dynamic characteristics of large area ceiling subjected to non-uniformly distributed acceleration due to floor or roof in-plane flexibility in steel structures. Horizontal displacement in the ceiling is separated into static and dynamic components based on multi input problem. It is shown that the ratio of horizontal stiffness of the ceiling to in-plane shear stiffness in the ceiling board governs seismic behavior. Two types of the ceiling brace force corresponding to the static and dynamic displacement is analyzed and its practical evaluation method is proposed. Finally, the method is validated in comparison with finite element analysis.
