Collapse Analysis of Ceilings Suspended in Concert Halls


Japan, which is an earthquake-prone country, has been suffering from earthquakes many times in the past and present. In recent years, the damage to nonstructural members, not only structural frameworks, is regarded as a major problem. Among them, the collapse of the suspended ceiling in large-scale spatial facilities such as gymnasiums and concert halls has become a serious problem, because it causes not only some direct human injuries but also a loss of function of the facilities as refuge bases.

As the ceilings of concert halls are acoustically designed, they have characteristics of large weight and complex structures compared to the conventional ceilings used for gymnasiums. Since such a ceiling is expected to exhibit specific falling behaviors under seismic excitations, it is necessary to investigate the behaviors beforehand and take appropriate anti-seismic measures. For that purpose, it is effective to conduct numerical analyses that can change parameters easily.

In this presentation, a collapse analysis of box-type suspended ceilings containing level gaps introduced in concert halls is described. A numerical model of a concert hall with suspended ceilings, constructed with linear Timoshenko beam elements, was simulated by applying seismic waves. We used the adaptively shifted integration (ASI)-Gauss code which can stably simulate those phenomena with strong nonlinearities such as fracture and contact. Furthermore, it was reported in the previous study that the fall of the ceiling was caused by the detachment of metal fittings. Therefore, detachment phenomena of the ceilings was expressed by introducing some criteria, based on the preliminary experimental results, into the simulations.

According to the numerical results, the collapse of the ceiling was caused by the detachment of clips. In addition, the detachment of clips was caused by the propagation of impact force occurred when the suspended ceiling collided with the wall, and it was confirmed that the detachment progressed as the load distribution supported by the clips had changed from the initial state. The results also showed that the locations of the detached clips caused by the collisions were strongly affected by the geometrical shape of the ceilings.

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