Abstract
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.