Evacuation Safety Evaluation in the Event of a Fire in a Shopping Center with a Connected Passageway in Korea

In this study, scenarios were developed to evaluate evacuation safety in the event of a fire in a shopping center with a connected passageway and to reduce Required Safe Egress Time (RSET). The RSET for all occupants by scenario is as follows: The first scenario which used the general evacuation route took 20 minutes and 7 seconds. The second scenario which used the third floor’s connected passageway for third and fourth floor, and using first floor entrance for first and second floor to evacuate took 14 minutes and 11 seconds. The evacuation time was 36 minutes and 52 seconds for scenario 3, which only used the fire escape stairs. The fourth scenario took 4 minutes and 19 seconds and used a connected passageway on every floor. Overall, this study shows that RSET for all occupants is reduced when a connected passageway is installed on every floor in shopping centers. Henceforth, more research is needed to determine whether connected passageway is a single firefighting object or a separate structure.


Introduction
Large-scale buildings such as shopping centers with connected passageways are currently on the rise. Especially shopping centers are densely populated and visitors are not familiar with the layout of the building. Therefore, the number of casualties tends to increase in the event of a fire. For example, the fire at 00 bus terminal [1] in 00 province in South Korea on May 26, 2014 and the fire at Korea 00 Metapolis [2] on February 4, 2017 both had complicated building layouts because of the large size of the buildings and concentration of various facilities. In addition, there are a lot of inflammable products, so the progress of the fire is extremely fast in the event of a fire. In this situation, there will be panic and confusion in the rapid movement, so the RSET for all occupants will be increased along with the increasing risk of casualties.

Object Selection and Outline of Evacuation Simulation 1) Object Selection of Evacuation Simulation
This study supposed that there was a fire in Building B in a shopping center consisting of buildings A and B and which is located in 00 city, 00 province in South Korea. The population density is high due to people and visitors moving between building A and B. Also, there are lots of people and the majority are unidentified people who are there to shop. Building B consists of parking lots from the second basement level to the first basement level, shopping malls on the first to fourth floor, a cinema on the fifth floor, and the sixth floor is used as a rooftop garden. As seen in Figure 1, the first floor to the fourth floor will be the focus of this study. conducted by applying the input values

Calculation Standard for Occupant Load
The shopping center is a sales facility, and the occupant load was calculated based on the calculation standard according to the area per person for each floor. There are two sections; the first floor, which is a safety floor, and the second to fourth floors, which are considered as over second floors. The average daily visitor ratio was 21.5 percent for men, 60.3 percent for women, 10.2 percent for children, and 8 percent for elderly [14]. There were 1,630 people on the third floor, where the concentration was the highest. Table 2 shows the number of people [15] and the area per person on each floor.

Evacuation Scenario Composition
Scenarios were organized into Scenario 1, Scenario 2, Scenario 3, and Scenario 4 to reduce the Required Safe Egress Time (RSET) for all occupants, as shown in Table 3. All scenarios assumed that no evacuation lifts were installed and that escalators were not used for fire routes. In addition, bottlenecks caused by dense population were considered in the evacuations, but delays caused by accidents were excluded. Scenario 1 consisted of evacuating via the general evacuation route from the actual drawing sheet used in this study to compare the general evacuation route with different conditions in the other scenarios. Scenario 2 consisted of using the third floor's connected passageway for the third and fourth floor, and using the first floor entrance for the first and second floor, assuming there is a fire on the second floor and it is therefore not possible to use the stairs connecting the second and third floor due to smoke. Scenario 3 consisted of evacuating using only enclosed stairways, assuming that the passageway on the third floor was used as an event hall and can therefore not be used to evacuate through. Scenario 4 is designed to allow evacuation from each floor by having a connecting passage installed on every floor to reduce the RSET for all occupants. The standard for measuring the evacuation time for each scenario was measuring when all the inhabitants have completed evacuated. The maximum exit distance for each scenario are as follows: Scenario 1: 253.3m, Scenario 2: 244.5m, Scenario 3: 418.1m and Scenario 4: 143.7m. Scenario 4 has the shortest maximum evacuation distance, so it is assumed that the RSET is the shortest as well.

Evaluation Basis
In evacuation facilities, most of the residents are always awake, but most of them are not familiar with the building's interior layout or escape route. In the event of an emergency, the facility broadcasts guidance from control rooms equipped with CCTV facilities. It was also confirmed by a trained fire protection manager that there is emergency broadcast equipment that can be recognized by all inhabitants in the building. The target site is a retail sales facility where food, clothing, and miscellaneous goods are sold, and the total floor area is over 1,000 square meters [17], so the evacuation time, as shown in Table 4, is set at less than two minutes [18].

Available evacuation time
Store (Inhabitant is always awake but unfamiliar with the interior of the building and the escape route) Under 2 min

Conclusion and Consideration
The selected elapsed time intervals for recording the number of evacuees are 1 minute and 59 seconds, 5 minutes, 6 minutes and RSET for all occupants. The reason for having 1 minutes 59 seconds as one of the intervals is to check how many people have completed evacuation within the available evacuation time, where the available evacuation time is under 2 minutes at Table 4. Rescue workers normally arrive within 5 minutes of the fire alarm and begin rescuing people in the building [19]. It is required to check the number of people who evacuated in 6 minutes in the event of a fire since residents are estimated to have an evacuation time of approximately 6 minutes in the event of a fire in the USA.  Figure 4 shows the number of successful evacuees by elapsed time when connected passageways, which were only on the third floor, are installed on all floors to decrease RSET. 3,255 people (55.72%) evacuated in 1 minute and 59 seconds, and the RSET for all 5,841 people was 4 minutes and 19 seconds. Even though this exceeds the evacuation time of 2 minutes, rescue workers normally arrive within 5 minutes of the fire alarm and immediately provide first aid and transport to the evacuated personnel, which can reduce casualties. It is also believed that all inhabitants will be evacuated within 6 minutes to avoid the life-threatening risk of fire. Analysis of scenario-specific RSETs, as shown in Table 5, showed that Scenario 4, which had a connected passageway on every floor, was 948.3 seconds less than Scenario 1, 591.8 seconds less than Scenario 2, and 1952.8 seconds less than Scenario 3. The result of Scenario 4 was an 88.4% decrease in RSET compared to Scenario 3, which was the longest. As a result, the RSET will be dramatically shortened if there is a connected passageway installed on every floor in a shopping center rather than having just one in the whole shopping center. As a result of analyzing the RSET for all occupants by scenario, the fourth scenario which had connected passageways installed on every floor showed a result 88.4% lower than scenario 3, which has the longest RSET for all occupants. As a result, the RSET for all occupants will be dramatically shortened if there is a connected passageway installed on every floor in a shopping center. Henceforth, more research is needed to determine whether a connected passageway is a single firefighting object or a separate structure.