Prototyping the Golden Thread of Information for Fire Evacuation in BIM
By: Nazim YAKHOU, Jensen Hughes, Belgium
This article presents the key findings of a master thesis, undertaken by the author, in fulfilment of the International Master of Fire Safety Engineering (IMFSE) at Lund University. This work was presented at the FEMTC 2022 conference and was also the subject of a joint publication.
Nazim Yakhou, Peter Thompson, Asim Siddiqui, Jimmy Abualdenien, Enrico Ronchi,The integration of building information modelling and fire evacuation models, Journal of Building Engineering, Volume 63, Part B,2023, 105557,ISSN 2352-7102, https://doi.org/10.1016/j.jobe.2022.105557.
Introduction
Building Information Modelling (BIM) has become a useful methodology in the Architectural, Engineering and Construction field and is seeing a rapid expansion in uptake across the globe. In fact, it has become a standard platform for integrated digital design, centralizing a lot of the knowledge about a building [1]. However, Fire Safety Engineering (FSE) is lagging behind other AEC sectors in terms of integration and synergy with the BIM workflow [1], which prevents Fire Safety Engineers from leveraging many of its benefits and can result in complications.
For example, when fire engineers perform simulations (such as CFD or crowd evacuation simulations), they often use BIM models to define their basic geometry. But this is usually a one-way process where much of the rich data found in BIM models is lost. Moreover, few, if any, parameters related to fire safety can be specified in the BIM model itself, and this prevents calculations from being easily re-iterated [2].
The Hackitt Report - a document in response to the Grenfell Tower fire - unveiled a series of failings of the construction sector. In particular, the fire safety compliance assessment process was described as "weak and complex” and characterized by “poor record keeping and change control" [3]. Some of the issues resulting from the lack of integration of FSE into BIM include:
· Increased efforts and delays for design evaluation (especially keeping track of design changes).
· Fragmentation of design and review processes, since stakeholders do not always have access to the simulation input and results (either because files are not/cannot be provided in a practical way, or because they do not have the necessary software to read the files).
· Inconsistent documentation and ambiguity in roles and responsibilities.
· Difficulty in archiving results for future reference (auditing, forensics) e.g., if the software used originally is not maintained anymore.
· Lack of data transfer protocols which can be source of conflict, data loss and frustration (for e.g., asset managers trying to consolidate data from several BIM models).
Ideally, BIM could be used to keep all the knowledge related to a project, including fire strategy and its supporting documents. For this reason, the Hackitt report insisted on the need for better sharing of information related to fire safety through BIM. This is seen as a means to prevent life and property loss by keeping in a same place, the design and maintenance data of a building, throughout its life cycle.
This digital record of safety information was conceptualized as the “Golden Thread of Information” [3] and was upheld by the IFSS coalition in its "Decade of Action" where it called for this principle to be enacted [4].
Research objectives
This work aimed at solving the current disconnect between BIM and FSE (with a focus on fire evacuation), by developing a framework for smoothly integrating these two disciplines into a joint, consistent workflow and achieve the “Golden Thread of Information”. The joint BIM/FSE model would serve as a digital trail for asset management, auditing, and forensics and enable stakeholders to review building design models coupled with analysis results.
It should be noted that this research focused on Fire evacuation, but the same could be said about fire simulations (CFD, zone models, etc.).
Implementation
The focus of this study was to establish a “round trip” data loop connecting the BIM software to evacuation simulation tools, resulting in an effective two-way data exchange, comprising not only geometry but also input properties necessary to conduct these simulations. The results from the simulations can also be captured and sent back to the BIM model to be stored along with geometrical information. This data loop is illustrated in Figure 1 below.
Figure 1 - Data loop linking Revit to the evacuation simulator (Pathfinder)
For prototyping purposes, Revit [5] was selected as a BIM platform and Pathfinder [6] was retained as a ‘model’ evacuation simulator. The steps leading to the implementation of this data loop are described below.
Step 1: Defining the data exchange protocol.
The first step was to implement a suitable protocol to enable data exchange. The .ifc file format was selected because it is open source and vendor neutral. It is an industry standard for describing building data and ensures BIM information can be accessed by all stakeholders regardless of the software they are using [7]. A list of data properties was compiled from multiple sources, such as Pathfinder’s user manual which lists properties of the evacuation model and output results and from the literature [9] [10]. The key findings are presented in Figure 2 below.
Figure 2: List of properties used for evacuation modelling.
Then, the properties identified previously were mapped into the IFC model. In total, 87 properties were defined and the complete list of IFC properties can be found in a dedicated publication [11].
Step 02: Implementing the data exchange protocol in Revit BIM and Pathfinder
The next step was to enhance Revit BIM to support the proposed framework. An add-in was developed by the author in order to extend the current capabilities of Revit. It supports importing, exporting, storing, and processing data points for fire evacuation (through IFC) and enables interoperability between the BIM package and evacuation simulators. The add-in program runs within the Revit environment and can access, read, display, edit and save any information available in the Revit model, (Figure 3 below).
Figure 3: Illustration of the add-in integration in Revit’s main interface
The add-in was developed using the Revit Application Programming Interface (API) [12] and can be used to generate input files for the evacuation simulator (in this case, Pathfinder). In addition to the geometry, the add-in allows the user to specify additional semantic information (for instance, occupant profiles, number of occupants, room function/usage, etc.) using different commands.
This data can then be exported into a combined .ifc file which can then be parsed within Pathfinder. A version of the software (number 2022-1-0404) was provided by Thunderhead Engineering (the developers of Pathfinder), which can read and process the newly proposed IFC schema.
After running the evacuation simulation (in Pathfinder), the results can be loaded into Revit using a dedicated command. The results are saved and can be displayed to the user, as shown in Figure 4. The add-in can also animate some of the results directly within Revit including, at various time steps: door flow rates, number of occupants remaining in a room and the density of a room.
Figure 4 – Evacuation simulation results imported into Revit by the add-in.
This feedback helps visualize the level of performance achieved by the building design, in terms of fire evacuation, for informed decision making. Additionally, this partially eliminates the need for sharing and storing large contour files (generated by Pathfinder) and prevents the fragmentation of assessment results, since they are stored in the BIM model itself. Moreover, stakeholders who need to evaluate fire evacuation performance but are not familiar with simulation software can access this useful information directly from the BIM model.
Results
An important outcome of this work was the definition of an IFC schema covering the data requirements for fire evacuation. The proposed IFC schema will contribute to the drafting of a new standard for Fire Safety Engineering which is in development by buildingSMART [13]. It also offers a broad definition which allows future developments to add support for alternative software packages.
Another contribution of this research is that it demonstrated the feasibility of two-way data exchange between a BIM platform (Revit) and fire safety assessment tools (evacuation simulator). Moreover, it enabled prototyping the golden thread of information by embedding fire evacuation information in the BIM model.
Finally, it was demonstrated that the fire safety engineering workflow can effectively be implemented in a BIM environment (in this case Revit). This offers a better insight of evacuation performance and enables informed decision making by recording assessment results and enabling access to all stakeholders.
Conclusion
This work presented a framework for the two-way integration of BIM and fire evacuation modelling tools. The framework has been implemented and tested through an open-source Revit add-in prototype called Evac4BIM that was coupled with a widely used evacuation simulator called Pathfinder.
This research is deemed to stimulate further developments in the area of automation of building design including FSE through open-source software using open data standards.
The source code and the assemblies were released in a public online repository [14] which is accessible to all interested parties.
References
[1] Chevin, D. (2020, November 17). The new fire safety digital framework explained. BIM+. https://www.bimplus.co.uk/new-fire-safety-digital-framework-explained/
[2] Siddiqui, A. A., Ewer, J. A., Lawrence, P. J., Galea, E. R., & Frost, I. R. (2021). Building Information Modelling for performance-based Fire Safety Engineering analysis – A strategy for data sharing. Journal of Building Engineering, 42, 102794. https://doi.org/10.1016/j.jobe.2021.102794
[3] Hackitt, J. (2018). Building a safer future. Independent Review of Building Regulations and Fire Safety: Final Report.
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/707785/Building_a_Safer_Future_-_web.pdf
[4] IFSS. (2021). IFSS Global Plan for a Decade of Action for Fire Safety. International Fire Safety Standards Coalition (IFSSC).
https://www.rics.org/globalassets/rics-website/media/knowledge/decade-of-action-for-fire-safety_oct2021.pdf
[5] Autodesk. Revit Overview (BIM package). https://knowledge.autodesk.com/support/revit
[6] Thunderhead Engineering. (2022). Pathfinder (Agent based evacuation simulator). https://www.thunderheadeng.com/pathfinder/
[7] buildingSMART. (2022). Industry Foundation Classes (IFC). BuildingSMART International. https://www.buildingsmart.org/standards/bsi-standards/industry-foundation-classes/
[9] Abualdenien, J., Kneidl, A., Lawrence, P., Lehtoviita, L., Siddiqui, S., & Thompson, P. (2021). Use Case: Evacuation Analysis—RIBA | Use Case Management. buildingSMART International. https://ucm.buildingsmart.org/use-case-details/2436/en
[10] Siddiqui, A. A. (2019). An investigation into data sharing between building information modelling and fire safety engineering, with potential applications to smart buildings [PhD, University of Greenwich]. https://gala.gre.ac.uk/id/eprint/32642/
[11] Nazim Yakhou, Peter Thompson, Asim Siddiqui, Jimmy Abualdenien, Enrico Ronchi,The integration of building information modelling and fire evacuation models, Journal of Building Engineering, Volume 63, Part B,2023, 105557,ISSN 2352-7102, https://doi.org/10.1016/j.jobe.2022.105557 .
[12] Autodesk. (2022b). Revit Overview (BIM package). https://knowledge.autodesk.com/support/revit
[13] buildingSMART. (2020). Fire Safety Engineering & Occupant Movement openBIM Standards. BuildingSMART International. https://www.buildingsmart.org/standards/calls-for-participation/fire-safety/
[14] Evac4Bim source code and binaries. https://github.com/YakNazim/Evac4Bim