Presentation at Coupled Problems Conference 2015 Venice

1. CREATE MAINTAIN PUBLISH
Combining semantic 3D GIS with
numerical Simulation for assessing the
impact of Blasts in urban Environments
Coupled Problems 2015
Venice
Arne Schilling Stefan Trometer
virtualcitySYSTEMS GmbH CADFEM GmbH
Berlin, Germany Grafing, Germany

2. Arne Schilling, Stefan Trometer2
 What is Urban Simulation?
 Challenge
 Use Case: Simulating Explosions in Urban Environments
 Discussion
 What‘s Next?
Outline

3. 3 Arne Schilling, Stefan Trometer
What is Urban Simulation?
Simulation of physical phenomena in urban environments
using virtual mockups / 3D city models

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What is Urban Simulation?
 Mechanical simulations of building
structures
 Acoustic studies / blast simulations
 Wind field simulations
 Simulation of flood events
 …

5. 5 Arne Schilling, Stefan Trometer
 GIS is not designed for performing complex physical computations
• Strengths of GIS are data management, spatial analysis and visualization
• 3D city models are created using remote sensing and automatic feature
extraction methods, not using CAD software
Challenge

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Challenge
 GIS is not designed for performing complex physical computations
• Strengths of GIS are data management, spatial analysis and visualization
• 3D city models are created using remote sensing and automatic feature
extraction methods, not using CAD software
 Physical simulations are frequently done in product design
• Using Cumputer Aided Design (CAD) and Computer Aided Engineering (CAE)
software such as ANSYS
• Based on the Finite Element approach -> Numerical Simulation

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Challenge
 GIS is not designed for performing complex physical computations
• Strengths of GIS are data management, spatial analysis and visualization
• 3D city models are created using remote sensing and automatic feature
extraction methods, not using CAD software
 Physical simulations are frequently done in product design
• Using Computer Aided Design (CAD) and Computer Aided Engineering (CAE)
software such as ANSYS
• Based on the Finite Element approach -> Numerical Simulation
 Technological gap between GIS and CAE Worlds
• CityGML cannot be loaded by CAE software (e.g. ANSYS). Geometrical
representations are very different -> we need conversion tools
• Requirements on data quality are different
• Simulation results are mostly stored in proprietary formats

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Challenge
 Create a workflow from 3D Geographic Information Systems to
Simulation frameworks and back

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Use Case: Simulating Explosions in Urban
Environments
Safety perimeters (red: evacuation, blue: curfew)
 Unexploded Bombs from WW2
 Frankfurt a.M. 2013 (150 kg)
Recovery of defused bomb
Disposal of defused bomb

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Use Case: Simulating Explosions in Urban
Environments
First assessment in 3D city model using damage zones and perimeters based on lookup tables

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 Simulation of shockwave propagations in ANSYS
• Extracting 3D city model from a CityGML database
• Geometry processing, geometry healing for creating solid models
Use Case: Simulating Explosions in Urban
Environments
Geometry healing, e.g. removing inner surfaces (top) and
resolving self-intersections (bottom)

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 Simulation of shockwave propagations in ANSYS
• Importing 3D city model using STEP (AP 214)
• Setting up rigid volumetric objects (for buildings and for the ground) as
Finite Elements
Use Case: Simulating Explosions in Urban
Environments
3D city model in ANSYS Finite Elements generated from 3D city model

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 Simulation of shockwave propagations in ANSYS
• Setting up air space as Euler grid (grid space 0,5m – 1,0m)
• Setting up spherical explosive charge and physical properties (e.g. air
density, materials)
• Using explicit solvers (AUTODYN, LS-DYNA and APOLLO from Fraunhofer
EMI) to run the physical simulation
Use Case: Simulating Explosions in Urban
Environments
Air space as Euler grid shockwave propagation in ANSYS

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 Simulation of shockwave propagations in ANSYS
• 1D simplification to speed up computations within the first meters until
the shockwave hits a building
• Computation time hours - days
• Analysis within ANSYS
Use Case: Simulating Explosions in Urban
Environments
Time stamp in APOLLO Reading points, grid refinement

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 Simulation of shockwave propagations in ANSYS
• Export simulation results as 3D grid data sets for several result types:
 Single time stamps
 Peak overpressure
 Impulse values
 Damage indicators for glass, masonry, injuries based on pressure and impulse values
• Create 3D models that can be used in online portals
 -> important for decision makers
Use Case: Simulating Explosions in Urban
Environments
Triangulated model for visualizations Results in online portal

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Scenario 2: 34 ms

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Scenario 2: 84 ms

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Scenario 2: 168 ms

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Scenario 2: 335 ms

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Scenario 2: 503 ms

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Scenario 2: 670 ms

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Scenario 2:
Peak Overpressure

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Scenario 2:
maximum Impulse

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Scenario 2: Damage
Categories

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Scenario 2: Quick
Assessment

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GefahrenkarteSzenario 2
Scenario 2:
Indicator Glass

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GefahrenkarteSzenario 2
Scenario 2:
Indicator Masonry

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GefahrenkarteSzenario 2
Scenario 2:
Indicator Eardrum

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Discussion
 Model Quality
• CityGML LOD 2 city models (no windows, balconies etc, roof
information)
• Simulated area limited to 1x1km (limitation in ANSYS)
LOD2 model of Berlin Simulation with LOD3 model
Super-detailed
simulation

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Discussion
 Comparison of AUTODYN, APOLLO and LS-DYNA solvers
• Computations in AUTYDYN and LS-DYNA took 3 days
• Computations in APOLLO took 3 hours

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Discussion
 Sensitivity analysis
• Increasing the robustness of results
• finding a reasonable grid size for modelling the air space
 -> ca. 1m

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What‘s Next?
GefahrenkarteSzenario 2 Simulation of pedestrian comfort levels
• CFD Methods for simulating
• Exchange of 3D city models using STEP
• Output: velocity plots at pedestrian level (wind comfort analysis)

33. Thank You
Arne Schilling Stefan Trometer
virtualcitySYSTEMS GmbH CADFEM GmbH
aschilling@virtualcitysystems.de strometer@cadfem.de
http://www.virtualcitysystems.de http://www.cadfem.de