Theory and practice of building safety evacuation design?

1. 1 safety exits and evacuation exits

Many architects do not have a clear understanding of this, and often say "the safe exit of rooms", "the safe exit of walkways" and "the safe exit of buildings". It seems that as long as it is a door, it is a safe exit, which is not strict for fire fighting. The specific distinction is as follows: safety exit: the specification defines it as the entrance and exit of stairwells and outdoor stairs for safe evacuation of people or the exit leading to indoor and outdoor safety areas. Evacuation exits: including safety exits and evacuation doors.

In architectural design, it mainly refers to the evacuation door, that is, the door that each room in the building directly leads to the evacuation aisle. From this point of view, in general design, the room door should be an evacuation door, and the door on the aisle should be an evacuation door in addition to the safety exit. That is, the emergency exit is for each fire zone or each floor of a fire zone, while the evacuation exit (mainly refers to the evacuation door) is for the room.

1.2 safe area

Safety areas are divided into indoor safety areas and outdoor safety areas. Indoor safety area: including the refuge floor and the refuge walkway that meet the requirements of the code. Outdoor safety area: including outdoor ground, roof, platform, overpass, corridor, etc. It meets the evacuation requirements and can reach the ground directly. After understanding the above contents, the theory and actual situation of building safety evacuation design are analyzed through concrete examples.

2 engineering examples and analysis

2. 1 example 1

The second-floor commercial building along the street has a fire zone on each floor, covering an area of 720m2( 12m×60m), and is divided into five small shops (each floor 12m× 12m). Each shop is connected with the upper and lower floors, so it is required to design safe evacuation. In the engineering practice in previous years, many designers adopted the way of opening a door in front of and behind the first floor of each shop, connecting the upper and lower floors through a closed staircase, and borrowing evacuation by opening the door in the partition wall of the adjacent shops on the second floor, which is wrong. The key is on the second floor, which is a separate room. There is only one stairwell leading to the first floor, and an evacuation exit is needed. Many designers use standardized borrowing evacuation here, which is wrong from theory to practice.

First of all, in theory, borrowing evacuation refers to borrowing between fire zones under certain conditions, which is aimed at safety exits, not room evacuation doors. In this case, as independent rooms in the fire zone, the two evacuation doors should be set directly on the evacuation walkway or stairs, not in the nearby shops. Secondly, this method is not desirable in practice. In real life, no matter in management or use, two adjacent shops are not allowed to have such a door leading to the next room. Even if the door is installed, it must be locked in order to prevent theft, and it can't be opened in an emergency. The existence of doors also directly affects the utilization rate of shop walls, which is also inappropriate from the perspective of architectural functional design. The current design method is: each store opens its doors at the front and back of the first floor, and the corridor along the second floor is used as an evacuation walkway (the corridor has two safety exits leading to the outside of the first floor), connecting the stores and opening the doors leading to the corridor on the second floor. This safe evacuation method meets the requirements of specifications and design from theory to practice. The unreasonable fire evacuation in this case stems from the designer's unfamiliarity with the specification requirements and the neglect of various situations in actual use. They should learn from practice and improve their professional level.

2.2 Example 2

A 30-story high-rise residential building, with two units and two households on each floor, requires safe evacuation. This is a standard one-staircase two-family apartment design. At present, the more mature design method is: the stairs are scissors ladders, and all the doors (evacuation doors) of the two households open to a front room shared by the stairs and the fire elevator, and the balcony of the other stairs is adjacent to the residents (the balcony also serves as the front room), and the other safety exit of the residents is opened on the balcony. Theoretically, this design method still meets the requirements of the specification. Each unit (each fire zone) has two safety exits on each floor, which meets the conditions for setting safety exits, but it also causes some objections, mainly from emergency evacuation under certain circumstances.

In practice, although every household has two safety exits directly to the outside, the hidden danger lies in that these two safety exits are connected through the interior of the house, that is, the residents who come out of any safety exit, whether going upstairs or downstairs, arrive at the shared front room or independent front room, are all in the safety system of the same staircase. If they want to enter another staircase, they must go through the interior of a house. Suppose: a resident neglects management and places long-term useless items in the scissors stairwell of a high-rise residential building. A staircase accidentally caught fire, the elevator stopped and the residents began to evacuate. On the way downstairs, someone found that the selected escape staircase caught fire due to unknown circumstances, and when they hurried into another staircase, the design hidden danger was exposed: either knocking on the doors of residents on other floors and going through other people's homes to another staircase; Either run back to your home and escape through another evacuation door.

Either way, it will delay precious time. The dispute in this case lies in the reliability of fire protection design in practice. No matter from theory to practice, the above-mentioned safety evacuation design should be feasible and reliable, but the previous assumption does not exist, that is to say, the designer ignores a reality: at present, the level of property management enterprises is uneven, and a large number of neglected communities, because residents do not have more storage space, are temporarily convenient, and items that are not used at home are placed in the stairwell or the front room. Some users leave their shoes outside the house, including many combustibles, in order to keep their homes clean and tidy. The front room and stairwell should be escape routes, and smoke prevention measures have been taken to prevent smoke from entering. It is meaningless to put flammable substances in it, and the originally relatively safe area directly becomes a dangerous area. Some designers will say: that's a management problem, not a design problem. Admittedly, as a basic design document, the specification has considered various design conditions and requirements, but it cannot cover all examples. In this case, the safety evacuation design theoretically meets the requirements of the code, but it does not mean that it can cope with all kinds of fire evacuation situations under realistic conditions. Moreover, the two safety exits are not suitable for passing through residential rooms when switching, which will highlight the danger under certain conditions. Therefore, designers should be alert and further improve the fire evacuation design, instead of shifting the responsibility to daily management.

2.3 Example 3

A 30-story high-rise residential building, with one unit and four families on each floor. The safety evacuation design is that every two households lead to a traffic core composed of smoke-proof stairwells and fire elevators, all doors lead to the shared front room, and the two traffic cores connect the front room through an open corridor. This example is given because there are many forms of this design recently, but it is also the most controversial type. Theoretically, the design should meet the specification requirements, and each unit should have no less than two safety exits on each floor. However, the controversy also comes from the actual evacuation. Because in life, every resident who has a traffic check must go through the shared front room and corridor in his own area before going to another traffic core (emergency exit) to reach the other side.

The hidden danger is that the shared front room is a safe area in the building because of fire doors and smoke exhaust measures. Under the condition that all equipment and environmental factors are normal, there is no problem in safe evacuation. However, if an accident happens, this safe area will be in danger. For an inexperienced ordinary resident, it is impossible to go to another safety exit through here. Some designers believe that it is no problem to meet the requirements of the code, take measures in place and ensure the safety of the shared front room. However, there are many uncontrollable factors in real life. The original intention of the specification is that every household can have two safety exits. When one of them is unavailable, you can go to the other one through other channels to escape in time. In this case, its own safety zone is invalid, and it is impossible to leave in most cases when there is internal danger.

3 Conclusion

Through the analysis of the above three examples, it can be seen that the safety evacuation design of buildings should not only meet the requirements of relevant codes in theory, but also combine various social and life factors to fully consider the safety, reliability and feasibility of the design. As an architectural designer, we should improve our own ability, consider possible potential factors, look at our own scheme drawings from the actual perspective of living environment, and minimize the adverse effects brought by various emergencies. This is the quality and responsibility that a qualified designer should have.

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