Modelling of Beirut explosion

Executive summary : Key military leaders can be confident in the use of simulation for damage assessment.

  • The analysis on the Beirut explosion that occurred on 4 August 2020 allows us to easily compare the results in the field to simulation.
  • The JCBRND COE, through the RFI process, is able to provide such simulations if requested.
Aim:
The aim of this study is to validate the outputs of the simplified model and compare it with the real-world case. Alsoto verify and show how modern simulations are accurate and could be used for planning, targetting and ,even taking into account the reality thatit could take few hours to get useable results, for conducting operations through military decision process.

Disclaimer:
This product reflects the policies and/or positions of the JCBRN Defence COE and/or its author(s) as an independent opinion. This product is not NATO endorsed or approved and does not reflect NATO's policies or positions.

  1. Introduction
    2.

Explosion Consequence Modelling techniques were some of the missing capabilities within JCBRN Defence COE Modelling and Simulation Section´s portfolio. The Defence Against Terrorism Program of Work (DAT PoW) project – Modelling & Simulation Enhancements - covered this capability gap by supplying new software called Breeze Explosion Damage Assessment Model (Breeze ExDAM) developed by Trinity Consultants Inc.

BREEZE ExDAM is a sophisticated modelling program that enables the JCBRN Defence COE to assess the structural damage and personnel injury from high explosives and vapor cloud explosions at all scales (including at micro-level such as a room).

BREEZE ExDAM can also be used for large scale explosion consequence analyses, which includes the effects on many surrounding structures in an urban area.

Fig. 1 - Example of a BREEZE ExDAM assessment
Fig. 1 - Example of a BREEZE ExDAM assessment

Recent incident in Beirut, Lebanon dated 4 August 2020 initiated in-house capability testing with the comparison of simulation calculated results vs real results.

  1. Real-world incident as “test case”
    2.
    1. Incident facts
      2.
On 4 August 2020, a large amount of ammonium nitrate stored at the port of the city of Beirut, the capital of Lebanon, exploded, causing at least 200 deaths, 3 reported missing and 6,500 injuries. Around 2,750 tonnes of this substance (equivalent to around 1.1 kilotons of TNT) had been stored in a warehouse without proper safety measures for the previous six years. The explosion was preceded by a fire in the same warehouse1.
Fig. 2 - Beirut explosion
Fig. 2 - Beirut explosion

    1. ExDAM model development
      2.

To calculate explosion damage there is a requirement to provide Breeze ExDAM with a model of structures within the study area. The study area for this case was considered to be a circle up to 1 km from the explosion location. This study area included up to 950 buildings or structures.

Fig. 3 - 3D model of a study area
Fig. 3 - 3D model of a study area

The extension module of Breeze ExDAM, named “3D Extend“, automates the process of creating and positioning structure blocks. Nevertheless, it requires to be supplied by Esri 3D building files containing footprint and height attributes of each individual structure. Such files aren´t always publicly available from open sources. Open street map (OSM) project has proven to be a valuable source of vector data, but it does not cover structure´s height attributes. Due to the lack of sufficient data, it was decided to assign each structure the same height (10m).

ExDAM includes over 100 pre-existing structure materials to select from, as well as the option to add new structure materials. Each material is assigned its own vulnerability parameter based upon empirical pressure-impulse (P-I) vulnerability data. As the use of materials are not readily available, it was decided to use non-reinforced concrete and cinder-block wall panels for all structures within the study area.

    1. Calculation and results
      2.

Short calculation times (a few minutes) was significantly influenced by the simplicity of the model. Higher fidelity models require longer computer processing time (up to a few hours).

Fig. 4 – Breeze ExDAM output – Block Damage (%)
Fig. 4 – Breeze ExDAM output – Block Damage (%)
Fig. 5 – Breeze ExDAM output - Grid Dynamic Pressure
Fig. 5 – Breeze ExDAM output - Grid Dynamic Pressure

The predicted/calculated results were overlayed on actual aftermath pictures to find the precision and fidelity of the model. The results of the simulation calculation (block damage outputs) matched the actual aftermath pictures in some areas. In addition, there is recognisable shielding effect of building structures. This fact supports the utility of a simplified model. It is to be noted that the whole process, including the model preparation and obtaining initial geographical data, is a time consuming process (in this case 2 working days). The model used for those calculations was developed using blocks of concreate with no windows or doors, and all same height attributes. This shows that there is a clear use for modelling calculation such as this.

Fig. 6 Aerial images and Breeze ExDAM results
Fig. 6 Aerial images and Breeze ExDAM results

Fig. 7 Explosion centre - near view
Fig. 7 Explosion centre - near view

  1. Conclusion
    2.

The main effort of this internal capability testing project was to validate outputs, compare the results with the real-world case and to find out whether the calculation and use of a simplified model can provide usable results. These results could be used for the decision-making process or at least situational awareness, taking into account the limitations related to the simplicity of the model as demonstrated.

It has been repeatedly proven that each type of model is appropriate for certain circumstances. For instance, a simple hazard assessment of a chemical stockpile could be conservatively performed using several simple models and does not require the refinement of a Computational Fluid dynamics (CFD) analysis.

Alternatively, in the case of a requirement for planning purposes or other similar reasons, a more precise model should be utilized. This would then require not only knowledge about structure`s dimensions but also materials, design etc. Open-source available data might not be able to cover these enhanced requirements. Also, higher fidelity calculations require more CPU processing time and hardware resources than the simplified model.

Note that knowledge of Breeze ExDAM software is required. Also, other tools and techniques (i.e. Geographical information system) are required to prepare data for the development of the explosion model. It is crucial to input into the Breeze ExDAM with structure´s data at a level that correlates to the required outputs.

Authors/Photos:
Major Robert Schnirch, CBRN Defence M&S IT Specialist and Deputy M&S Section Chief, CZE - A
Warrant Officer Kamil Šesták, CSM Acting, JCBRN Defence COE, CZE – AF


1Wikipedia - https://en.wikipedia.org/wiki/2020_Beirut_explosion