Verification and Validation of Viswalk for Building Evacuation Modelling

Abstract

This thesis is evaluating the pedestrian modelling software Viswalk for the use as a building evacuation model, by verifying and validating the model. In the verification, a procedure from the National Institute of Standards and Technology (NIST) is used as a basis to assess Viswalk’s ability to represent pre-evacuation time, movement and navigation, exit usage, route availability and flow constraints. Seven tests are excluded due to delimitations of the thesis or limitations of the current version of the model. The verification tests show that Viswalk is able to represent the main core components of evacuation models that are under consideration. The model yields results that correspond with the expected results for all 10 verification tests that are performed. However, non-conservative flow rates can be obtained if the default input settings are used. In the validation, results from Viswalk are compared to four real life experiments including a corridor, a classroom, a theatre lobby and a stair, followed by an uncertainty analysis. With adjusted input settings the movement times deviate with 2-16 % from the experiments and with default input settings the movement times deviate with 12-95 %. The walking speed is an important parameter in the validation tests, even with substantial congestion, with up to 46 % increased movement times when the walking speeds are decreased with 25 %. In the validation it is also noted that the occupant densities in front of openings can differ with up to 45 % between the simulations and the experiments. Despite the aspects described above, results that are close to experimental results can be obtained if the user has a good estimation of the occupant demographics and is aware of the limitations of the model.

Popular Abstract

The computer program Viswalk is a known simulation tool in traffic planning, but is a rather new addition when it comes to building evacuation modelling. The program is therefore evaluated by basic tests and compared to previous evacuation experiments to see how well it predicts pedestrian movement.

As our cities increase in population density, more and more high and complex buildings get built, which places high demands on fire safety. In 2013, 104 people died in Sweden due to fires and to prevent these deaths, the fire protection designs of buildings have to keep up with the development of complex buildings. There are currently computer programs and hand calculations that can be used to estimate how long it will take for people in a particular building or area to walk from point A to point B. A computer program that can be used for this purpose is Viswalk. Viswalk is mainly used in traffic planning when deciding how buildings, arenas, train stations, intersections and so on should be designed. Since the program can be used in several different areas, it can be a good tool when assessing the fire safety in large and complex scenarios. Few studies have however been performed that focus on Viswalk’s use for building evacuation modelling.

The thesis focused on evaluating Viswalk as a building evacuation model, and the program has been assessed both according to guidelines from the National Institution of Standards and Technology (NIST) and by comparisons to previously performed real life evacuation experiments. This is very important from a fire safety perspective since it is essential when using these types of programs that the results correspond with reality.

The program was verified, which means that the fundamental assumptions used by the program were tested and evaluated with simple tests. This included for example to test if the walking speeds that were specified by the program user matched the walking speeds that were obtained when running the program. The real life experiments that were used included a corridor, a classroom, a theatre lobby and a stair to evaluate the program for realistic everyday situations. In the evaluation, the pedestrians’ movement times from the experiment were compared to those from the program to see if they matched.

The results from the evaluation showed that results that are close to experimental results can be obtained if the input parameters are adjusted to correspond with the populations from the experiments. The program yielded movement times that deviated with 2-16 % from the four experiments and the results from the verification tests corresponded with the expected results. However, non-conservative flow rates can be obtained if the default input settings are used. It was also noted that the walking speed was an important parameter, even with substantial congestion, with up to 46 % increased movement times when the walking speeds were decreased with 25 %. Another finding was that occupant densities in front of openings can differ with up to 45 % between the simulations and the experiments.

• author: Henningsson, Johan and Blomstrand Martén, Johan
• supervisor: Enrico Ronchi
• organization: Division of Fire Safety Engineering
• course: VBRM10 20142
• year: 2015
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Viswalk, evacuation model, egress model, verification, validation
• publication/series: LUTVDG/TVBB
• report number: 5481
• ISSN: 1402-3504
• language: English
• id: 5337197
• date added to LUP: 2015-05-05 14:28:26
• date last changed: 2015-06-04 11:17:01