Aizhu Ren

Simulation of Emergency Evacuation in Virtual Reality

A virtual reality system was developed to simulate emergency evacuations during fires. The spreading of the flame and smoke in the virtual fire was modeled based on numerical fire simulations, so that the conditions are similar to real life. A multi-grid, multi-base-state database model was used to overcome the disadvantages of traditional smoke spreading simulations. Textured images and particle systems provide visualization of the flame and smoke. The system immerses the user in a virtual environment with detailed interactions between the users and the virtual environment. The system can show which evacuation methods are effective for building safety evaluations.

A virtual reality based fire training simulator with smoke hazard assessment capacity

Smoke is a leading cause of death in fire. To minimize the potential harm from the smoke hazards in the course of a fire, a rational virtual reality (VR)-based fire training simulator taking full account of the various aspects of smoke hazards has been developed and is described herein. In this simulator, a visualization technique based on volume rendering and fire dynamics data has been especially designed to create a realistic and accurate smoke environment for the purposes of effective virtual training, which allows the trainees to experience a realistic and yet non-threatening fire scenario. In addition, an integrated assessment model of smoke hazards is also established in order to assess the safety of different paths for evacuation or rescue in virtual training, which allows the trainees to learn to identify the safest path. Two case studies of a subway station and a primary school demonstrated a high level of accuracy and smooth interactive performance of the proposed simulator, which is thus shown to be valuable for the training of both people who might become trapped in fire and firefighters engaged in learning the proper rescue procedures.

Seismic damage simulation in urban areas based on a high-fidelity structural model and a physics engine

Effective seismic damage simulation is an important task in improving earthquake resistance and safety of dense urban areas. There exist two significant technical challenges for realizing such a simulation: accurate prediction and realistic display. A high-fidelity structural model is proposed herein to accurately predict the seismic damage that was inflicted on a large number of buildings in an urban area via time-history analysis, with which the local damage to different building stories is also explicitly obtained. The accuracy and efficiency of the proposed model are validated by a refined finite element analysis of a typical building. A physics engine-based algorithm is also proposed that realistically displays building collapse, thus overcoming the limitations of the high-fidelity structural model. Furthermore, a visualization system integrating the proposed model and collapse simulation is developed so as to completely display the seismic damage in detail. Finally, the simulated seismic damage of a real medium-sized Chinese city is evaluated to demonstrate the advantages of the proposed techniques, which can provide critically important reference information for urban disaster prevention and mitigation.

Progressive-Collapse Simulation and Critical Region Identification of a Stone Arch Bridge

AbstractProgressive collapses of arch bridges have repeatedly occurred in recent years, resulting in many casualties and significant property losses. Based on an actual recent and serious progressive collapse of a stone arch bridge, this paper simulated the complete progressive-collapse process using the general-purpose finite-element (FE) program, MSC.Marc. The simulation adopted a three-dimensional (3D) FE model and performed a nonlinear analysis using the contact algorithm in conjunction with the element-deactivation technique. The potential causes of the progressive collapse of the stone arch bridge were also evaluated. Furthermore, the importance of different components of the stone arch bridge was determined with the conception of generalized structural stiffness; thus, the most critical and vulnerable regions of the bridge were identified. The results of the simulated progressive-collapse process agreed well with the actual process, and the predicted critical regions were both correct and realistic...

Earthquake disaster simulation for an urban area, with GIS, CAD, FEA, and VR integration

For a disaster whose scale includes an urban area, it is difficult to be studied with physical experiments. Numerical simulation is found a very efficient tool for such problem. This paper aims at developing an integrated urban earthquake simulation system (UESS) that uses GIS as the model source, CAD as the model generating tools, FEA as damage prediction, and virtual reality (VR) as the post-process platform. An automatic procedure was developed to buildup the 3D structural model of buildings in an urban area, as well as to simulate their earthquake performances, from the digital map of GIS. And the simulation results were presented in an integrated interface with a GIS view-port for position finding, a CAD view-port for 3D structural damage identification, and a VR view-port for 3D dynamic structural vibration display. An urban example with more than 7000 buildings was select to demonstrate the feasibility of proposed system.

Urban Fire Risk Clustering Method Based on Fire Statistics

Fire statistics and fire analysis have become important ways for us to understand the law of fire, prevent the occurrence of fire, and improve the ability to control fire. According to existing fire statistics, the weighted fire risk calculating method characterized by the number of fire occurrence, direct economic losses, and fire casualties was put forward. On the basis of this method, meanwhile having improved K-mean clustering arithmetic, this paper established fire risk K-mean clustering model, which could better resolve the automatic classifying problems towards fire risk. Fire risk cluster should be classified by the absolute distance of the target instead of the relative distance in the traditional cluster arithmetic. Finally, for applying the established model, this paper carried out fire risk clustering on fire statistics from January 2000 to December 2004 of Shenyang in China. This research would provide technical support for urban fire management.

An Integrated Model for the Fire Safety Analysis of Large Space Buildings

It is now widely recognized that performance-based design provides great advantages over prescriptive codes in that designers are allowed to use fire engineering methods to assess the fire safety of buildings. However, traditionally, performance-based fire safety design is still widely performed separately in specified individual study domains, such as fire engineering and structural engineering etc‥ Although the effects of a real fire have been considered in some structural fire resistant designs and in evacuation simulations, as well as in the mechanical analysis of load-bearing structures, the overall integrated assessment of a whole spatial structure performance is seldom performed. Based on middle-layer structure and component structure technology, this paper presents a new multi-dimensional integrated model and methodology for structural fire safety analysis. The effects of a real fire on structures and evacuation can be simulated through a close coupling of fire dynamics, structural analysis, and evacuation simulation. Based on the model, an integrated system FireSAS, was developed. One gymnasium, a competition venue of the 2008 Beijing Olympic Games, was selected as a study case. The results show that the mechanical responses and behaviours of large space steel structures have complex integrity characteristics as a whole under real fire conditions, and do not suffer merely a local effect. The case demonstrates that the FireSAS system is a useful engineering tool for cost-saving and safe structure design.

Fiber Beam Element Model for the Collapse Simulation of Concrete Structures under Fire

In order to analyze and simulate the collapse of reinforced concrete elements under fire, a novel numerical model based on the fiber beam model is proposed in this paper. By dividing the cross section of beam element into many small concrete and steel fibers and assigning different materials to each fiber, this model can consider the non-uniform temperature distribution across the section and simulate the behavior of cracking or crushing for concrete and yielding for steel. The explicit tangential stiffness matrix is deduced for proposed fiber beam with Total Lagrange description, and the incremental equilibrium equations are also established. Finally, the fiber model proposed in this paper is validated by comparing with various experimental results.

Regional Seismic Damage Prediction Based on High-performance GPU Computing: A case study of Tsinghua University campus

The prediction of seismic damage to buildings in urban areas is an important technique for the mitigation and prevention of earthquake-induced destruction. A methodology is proposed for such predictions, based on high-performance graphics processing unit (GPU) computing, which is applied to a case study of a real university campus. Specifically, an overall framework is designed based on cooperation between the GPU and CPU. A high-fidelity structural model suitable for GPU computing is built and the thread structure of the GPU-based seismic damage prediction is discussed. Taking Tsinghua University campus as an example, the seismic damage to the entire campus is predicted efficiently by the proposed method and the detail of local damage on different stories is obtained explicitly. Furthermore, an increase in speed of approximately 21 times is achieved in comparison with a traditional CPU approach. The outcome of this study provides a critically important reference for the prevention and mitigation of urban disaster.