The use of elevators in the evacuation of high-rise buildings

The paper substantiates the possibility of using the elevators as the main evacuation path from high-rise multi-storey buildings. The analysis of the reasons preventing effective evacuation of people from high-rise buildings is carried out. A tall multi-storey office building was modeled in the Pathfinder software package. Several scenarios of the human flow are presented, and the influence of time parameters (the beginning of evacuation and delay of signal delivery), the composition of the flow (different ratios of people of different mobility groups), and the level at which the evacuation of each group begins are reflected on the time of evacuation using elevators. The time of evacuation by a staircase is compared with the time of evacuation using elevators. It is shown that it is effective to use evacuation elevators in 60-storey buildings, but it is not rational to use them for a 20storey building.


Introduction
Every year the number of high-rise buildings and structures increases.In such buildings, evacuation ways are too long so even healthy people will suffer from fatigue when they are moving to such long distances, For orderly people and people with reduced mobility (PRM) this evacuation method becomes especially difficult, dangerous, and at times physically impossible [1].In article [2] it is noted that the stairs do not provide sufficient capacity to organize the evacuation of people from a high-rise building.
A number of reasons are presented that prevent the introduction of evacuation lifts: • Smoke of the lift shaft and elevator cabins; • Power outage; • stopping the elevator on a floor covered by fire; • deformation and jamming of elevator doors on the floor of the fire; • getting water from extinguishing a fire in the elevator shaft; • possible overflow of elevator cabins by evacuating people; • Creation of an elevator shaft for the spread of smoke and poisonous combustion products.Investigations of people's behavior during a fire [3,4] revealed that when the lifts function during a fire, some people use them during evacuation.In five-story houses this value reaches 15%, and in twenty-storey buildings of hotels 67%.It is worth mentioning separately that evacuation from the Twin Towers after the terrorist act with the help of elevators saved up to 3000 lives [5].

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In the PC Pathfinder model, the most accurate algorithm is realized, which presupposes the intellectual movement of people (maneuvering, avoidance of collision, acceleration in the presence of free space) [6].However, the authors of [7] draw attention to the results of the evolution of evacuation obtained in software complexes, should be approached with caution, since this process is highly dependent on the algorithm of the program, and, for example, the results of modeling in Pathfinder are understated because of the high traffic intensity human flow through places of local narrowing.One example of successful evacuation modeling in the Pathfinder program is the calculation of the fire safety of the university library in Nanjing [8].
The article [9] emphasizes that a person spends part of the time investigating an emergency situation, trying to collect things, and this delay, in the opinion of [10], is the main cause of trauma and death of people.A lot of time is spent on people's reaction to tools of warning and evacuation [11,12].
The purpose of the article is to justify the possibility of using elevators in the evacuation of people from high-rise buildings and structures.To achieve this goal, the following tasks were accomplished: 1) A high-rise multistorey office building was modeled in the Pathfinder software package.The following dependencies of the evacuation time on the parameters of the movement of people of different health categories were considered: • Estimated time using an exceptionally staircase (except M4); • Time of evacuation during the movement of persons of categories M2, M3 and M4 through elevators; • Flow control M1.Partial evacuation of persons of this category through elevators.
2) Comparison of the evacuation time through a staircase and using elevators.

Methods
A tall multi-storey building was modeled in the Pathfinder program.The evacuation time was calculated using both ladders exclusively and with partial use of vertical elevator units.Dependences of the most optimal percentage of people using the first and second versions of evacuation routes are obtained.The calculations were carried out taking into account the presence of an immobile population group.Parameters of a high-rise multi-storey building:  Number of floors -60 pcs.The building is divided into 3 sections of 20 floors; In each twenty-storey section:  Height of the floor is 3 meters;  Useful floor area 600 m2;  100 people per floor (at the rate of 1 person per 6m 2 usable area).The ratio of people in the health groups M1, M2, M3, M4 is taken to be 90, 4, 4, 2; In the calculation, an excessive number of individuals of PRM (10%) was accepted because of the demographic trend of maintaining the working capacity of the population of retirement age and in conditions of environmental accessibility [13];  Two U-shaped stairs H3 type, a march is 1350 mm;  6 elevators for 13 people (a = 1.2 m/s^2, v (max) = 2.5 m/s) inside the block for 20 floors.These elevators move inside the section; https://doi.org/10.1051/matecconf/201819303030ESCI 2018  4 lift-shuttles for 26 people (a = 1.2 m/s 2 , v (max) = 4 m/s) are vertical connections of the 1st floor of the building and the 1st floor of sections 2 and 3 (20th and 40th respectively).There are two lifts per section;  The project provides for two safety zones -20 and 40 floors [14];   .= 2.8 minutes (Time of start evacuation is a time after alert and before beginning human movement.It should be added to the estimated time to obtain the most reliable result) [15].
In Figure 1 there is the 3D plan of the typical floor and in Figure 2 3D section view of the modeled building with the notation of safety zones, lifts which move inside the section and lift shutters.

Results and Discussion
After analyze the dependence of the number of people evacuated from the time, it was noted that the completion of evacuation by stairs and elevators was not simultaneous.After the end of the use of elevators (M2, M3 and M4), for some time people of category M1 continue to descend the stairs.This leads to an increase in the final period of evacuation.Consider a situation where some people in the M1 category also use an elevator to descend to the base floor and find the most effective percentage of the persons M1 category.Results are in the table 1.As a level from which the evacuation of citizens of PRM M2 and M3 we took the 7th floor.The fastest partial evacuation of people in the ratio of 30% M1 was sent to evacuation via elevator from 7th to 14th floor, 40% of M1 was sent for evacuation via elevator from the 15th to the 19th floor.The results were obtained with allowance for the delay (0-120-0-240-0-360), which turned out to be the most effective according to the calculation results.When using measures regulating the human flow, there is a consistent decrease in the total evacuation time.The final comparison of the evacuation time for the entire building and for the section through a staircase and using elevators is summarized in Table 3.The use of elevators on average reduces the evacuation time by 30%.For a twenty-story building, the use of elevators and the management of the human flow reduces the duration of the evacuation by only 6 minutes, which calls into question the need for the use of this technical equipment as the main evacuation path.However, in a high-rise 60-storey office building with a high density of people, the improvement of the result exceeds 15 minutes.This result is a fairly large indicator, significantly reducing the time people stay in the building with a fire.

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The diagram in Figure 3 shows the movement of human flows during the evacuation of the entire building.The unevenness at the end of the graph is due to the lack of human flow settings regarding the shuttles connecting the base floor of the section and the first floor of the building.If the schedule is extended to the ideal case of linear dependence, then the time is reached when the lifts-shuttles and stairs bring the evacuated to the first floor simultaneously.Thus, it is possible to obtain a minimum evacuation time with simultaneous use of elevators and shuttles, equal to 1770 seconds.The value is obtained by sequential interpolation of the graph values.

Conclusions
An analysis of the reasons preventing effective evacuation from high-rise buildings has shown that it is difficult even for fully healthy people to overcome long distances of the evacuation path.However, this problem is especially persons with reduced mobility, including elderly people, in whom greater physical exertion can cause additional difficulties.
1. Several scenarios of the flow of human flow are presented and the influence on the evacuation time of the parameters as the beginning of evacuation and delay of signal delivery, the composition of the flow (people of different mobility groups), and the level at which the evacuation of each group begins is shown on the time of evacuation using elevators.
2. Comparison of the evacuation time through the staircase and using elevators showed that for a 20-storey building it is not rational to use the elevator system as one of the main evacuation routes, but for a 60-storey building it is very effective.In the future, it is necessary to consider the organization evacuation with the use of elevators.

Fig. 1 .
Fig. 1.Typical floor plan of the simulated office building.

Fig. 2 .
Fig. 2. Section of a simulated office building: a) Movement of the elevator-shuttle from the first floor to the 20 th ; b) Movement of the elevator-shuttle from the first floor to the 40 th .

Fig. 3 .
Fig. 3.The diagram of human flows during the evacuation.

Table 1
Influence on the total evacuation time of the partial movement of the flow M1 through elevators in a separate section 1-19 floor.

Table 2 .
Summary table of variations in evacuation parameters of section 1-19 floor

Table 3 .
Summary table of evacuation parameters of the section and the whole building