# Virtual Scene Construction for Seismic Damage of Building Ceilings and Furniture
## 1 Introduction  
With the development of earthquake engineering, the earthquake-induced collapse of building structures has been effectively controlled in recent years [1; 2; 3; 4; 5; 6]. However, seismic damage of indoor nonstructural components remains a serious issue, leading to possible occupant casualties. For example, in the 2017 Jiuzhaigou Earthquake (Ms 7.0), most buildings did not suffer serious damage or collapse [7], and indoor nonstructural damage (e.g., fallen ceilings and overturned furniture) caused the majority of casualties [8]. Construction of a virtual seismic damage scene for indoor nonstructural components can be used to conduct virtual earthquake safety drills for occupants [9]. For instance, [PERSON] et al. [10] used virtual earthquake scene to teach special populations how to cope in emergency. [PERSON] et al. [11; 12] proposed a virtual reality (VR) based drill tool for building earthquake preparedness, by which the indoor earthquake scene of the Auckland City Hospital, New Zealand was built and thus the virtual earthquake evacuation drill was performed. Such virtual drills can help occupants avoid physical injuries induced by nonstructural damage and thus decrease the number of casualties. The validity of the virtual seismic damage scene for indoor nonstructural components is critical for virtual earthquake drills, because the unreasonable seismic damage scene may mislead occupants into making poor safety decisions in drills. However, the existing research has focused on realistic representation of indoor seismic damage rather than the validity of the seismic damage [10; 11; 12; 13; 14; 15]. For instance, [PERSON] et al. [16] created realistic virtual scenes of the indoor seismic damage to nonstructural components. However, the ground motion was directly used to calculate the damage of nonstructural components, while the dynamic seismic response of the building structure was not considered, which will lead to a significant error in determining the damage of nonstructural components. To construct a valid virtual seismic damage scene for indoor nonstructural components, three important problems must be resolved:  
1. How will the required structural seismic dynamic responses of nonstructural components be obtained? The seismic damage to nonstructural components depends on the structural seismic dynamic responses (e.g., floor drifts and accelerations), and thus obtaining these results is essential for constructing a seismic damage scene. 2. How will the damage states (DSs) of nonstructural components be determined? A criterion is necessary to determine the DSs of nonstructural components based on specific values of the structural seismic response. 3. How will the subsequent movements of the damaged nonstructural components be simulated? After a nonstructural component is damaged, it will undergo a complex subsequent movement, e.g., a ceiling tile will fall when it breaks away from the suspended ceiling. Therefore, the subsequent movements of damaged nonstructural components need to be simulated to create a valid virtual scene of indoor seismic damage. To resolve problem 1, a time-history analysis (THA) of the building structure can provide a detailed structural seismic response. However, the structural analysis model of the THA must be consistent with the VR model to ensure correspondence between the seismic response and the indoor scene. Consistent models for THAs and virtual scenes can be created based on building information modeling (BIM) technology [17]. A detailed three-dimensional (3D) model can be created rapidly using BIM tools--e.g., Revit [18] and Tekla [19]--and much research has been conducted on BIM-based model conversion, e.g., industry foundation classes (IFC) [20]. Therefore, a BIM-based model can be transformed to a structural analysis model and a VR model, respectively. In this way, a THA can be efficiently performed using the transformed structural analysis model, which will provide the exact corresponding seismic responses for the VR model.