Numerical Analysis of Suspended Ceiling Collapse Using ASI-Gauss Technique

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. In order to investigate the dynamic mechanism of suspended ceiling collapse, some experimental studies have been introduced such as the ceiling collapse experiment conducted at the E-Defense shaking table facility. These studies have provided insights into the collapse mechanism of the conventional suspended ceilings. However, since the suspended ceilings have various types of shapes and specifications which often affect the collapse behaviors, it is necessary to investigate each ceiling according to their types. Furthermore, in order to accurately evaluate the collapse behaviors of the suspended ceilings, a largescale specimen is required because the vibration characteristic of structural framework must be taken into consideration. For the above reasons, it is desirable to substitute high-cost experiments by numerical analyses as an alternative. Therefore, a numerical code to consider the ceiling collapse phenomenon was constructed by using the finite element method based on the ASI-Gauss technique. In this presentation, the reproducibility of the ceiling collapse analysis was improved by adding three modifications to the numerical model of the suspended ceiling. First, the eccentricity of the hanger was considered more precisely to evaluate the buckling of hanging bolt and the vertical vibration of the finishing material. Second, the displacement that occurred when the ceiling joist joint detached was considered by changing the axial stiffness of the element. Finally, the internal force reduction due to slip motion of clips was considered by introducing a safety factor to the detachment load of the clips. In addition, a reproduction analysis of the experiment and the ceiling collapse simulation of a concert hall, as an example, were performed. From the result of the analyses, it was confirmed that the area and scale of ceiling collapse were in good agreement with the experimental result. Furthermore, it was suggested from the numerical result of the concert hall that the shape of the ceiling surface tended to influence the collapse mode.