introduction
With the rapid development of urban architecture and the increasing demand for convenient living, elevators have become an indispensable building equipment in high-rise buildings and public places in cities.
1、 The Development History of Elevators
In the mid-19th century, during the deepening of the Industrial Revolution, the demand for vertical transportation of goods and personnel was already so urgent, and various conditions were already in place. However, at that time, steam elevators could not solve a key safety problem - as long as the lifting rope suddenly broke, the elevator would quickly fall to the bottom layer. This inherent safety problem greatly limited its use. In 1852, Otis invented a device to solve the safety problem of elevators. He fixed a serrated iron bar on the guide rail, set a spring plate on the upper part of the car, and connected it to the mechanical linkage device and brake pawl. The traction rope is fixed at the center of the spring plate. When the traction rope breaks, the spring plate returns to its original shape, forcing the mechanical linkage device to act. Then, the brake claw extends into the serrated iron bar to prevent the elevator from falling.
Thus, the world's first "safety elevator" was invented. From then on, elevators ushered in the beginning of true development in history. However, Otis Company's business did not immediately explode as a result. The records of Otis Company indicate that in 1854, they only sold a few elevators, and in 1855, they only sold 15 elevators. By 1856, a total of 27 elevators were sold, and at that time, all elevators were still limited to freight use. In March 1857, the world's first safe passenger elevator was installed in a shop specializing in French porcelain and glassware on Broadway, New York. The store has five floors, and even though it was a relatively tall building at the time, the power of the elevator was driven by a series of shafts and belts from the steam power station inside the building. This ladder can carry 500 kilograms and has a speed of approximately 12 meters per minute.
Because the elevator offers a beautiful view, it is highly welcomed by many people in the upper class. Although Otis is known as the "father of elevators", in fact, Otis himself has never built a real elevator because in his era, machines were commonly powered by steam burned from coal. It was not until December 1889 that Otis Elevator Company installed the first truly named elevator in the Demerest Building in New York - it was powered by a DC motor, driven by a turbine reducer to suspend and lift the car by winding ropes around the drum.
This ancient elevator can only walk about 10 meters per minute. In 1900, elevators driven by AC motors were introduced. In 1902, Swiss company Schindler successfully developed the world's first button type automatic elevator, which adopted a fully automatic control method, improving the elevator's conveying capacity and safety. Subsequently, elevators entered a stage of rapid development.
2、 According to the different properties of elevators,
The main classification of elevators is as follows
From a spatial perspective, it mainly includes: the computer room section, the shaft and pit section, the elevator car section, and the floor station section.
From a system perspective, it mainly includes the following major systems:
● Traction system: The main function of the traction system is to output and transmit power to operate the elevator. The traction system mainly consists of a traction machine, traction steel wire rope, guide wheel, and reverse rope wheel.
● Guidance system: The main function of the guidance system is to limit the freedom of movement of the elevator car and counterweight, so that the elevator car and counterweight can only move up and down along the guide rail. The guidance system mainly consists of guide rails, guide shoes, and guide frames.
● Car: The car is an elevator component that transports passengers and goods, and is the working part of the elevator. The car is composed of a car frame and a car body.
Door system: The main function of the door system is to seal the entrance of the landing station and the entrance of the elevator car. The door system consists of a car door, a landing door, a door opener, and a door lock device.
● Weight balance system: The main function of the system is to relatively balance the weight of the elevator car. During elevator operation, it can keep the weight difference between the car and the counterweight within the limit, ensuring the normal traction transmission of the elevator. The system mainly consists of counterweight and weight compensation devices.
Electric drive system: The function of electric drive system is to provide power and implement elevator speed control. The electric drive system consists of a traction motor, power supply system, speed feedback device, motor speed control device, etc.
Electrical control system: The main function of the electrical control system is to operate and control the operation of the elevator. The electrical control system mainly consists of control devices, position display devices, control screens (cabinets), leveling devices, layer selectors, etc.
● Safety protection system: Ensure the safe use of elevators and prevent all accidents that endanger personal safety from occurring. It is composed of elevator speed limiter, safety pliers, rope gripper, buffer, safety touch plate, landing door lock, elevator safety window, elevator overload limit device, and limit switch device.
The system classification of elevators is detailed in Figure 1
Figure 1: Schematic diagram of elevator system classification
The schematic diagram of the internal structure of the elevator is detailed in Figure 2
Figure 2: Schematic diagram of the internal structure of the elevator
As a special equipment for mechatronics integration, elevator products are a concentrated embodiment of mechanical devices, electric drives, and computer control. The core technology of the entire elevator system is focused on driving technology and control technology. At present, the main driving technology used in elevators is permanent magnet synchronous toothless traction technology, and the control technology is mainly VVVF (variable frequency variable voltage speed regulation).
4、 Basic calculation configuration for elevator selection
With the acceleration of national urbanization and the opening of the registered residence system in large and medium-sized cities, the market demand for residential products will rise slightly. How to configure elevator products in the development process of residential buildings poses a challenge to designers. We mainly divide the residential product line in the current market into three categories: super high-rise residential, high-rise residential, and multi story and villa products. How should we configure elevators for the above residential products, and what are the different focus points for different product categories when configuring elevators.
Before studying elevator configuration, let's first understand the two key indicators of elevator evaluation. 5-minute capacity (HC5) and average waiting time for elevators (WT). Five minute capacity refers to the percentage of all passengers that can be transported by all elevators within five minutes under full load operation compared to the total number of passengers that need to be transported. The average waiting time for elevators is the average waiting time. For senior management, the configuration of vertical transportation is directly related to the development cost and customer satisfaction. How to balance development costs and vertical transportation capacity has become the key in the design phase. In the design phase, the configuration and selection of elevators mainly involve three main aspects: first, the number of elevators; second, the load capacity of elevators; third, the speed of elevators. Let's first explain the basic principles for determining these three elements.
The basic principle for the number of elevators is as follows:
Number of elevators=total number of people in the building/number of people served by each elevator or number of elevators=total number of floors/number of floors served by each elevator
Note: The number of people served by each elevator is generally determined based on 200-250 people (for office use);
The number of service floors per elevator is generally determined based on 4-5 floors (for office use)
The basic principle of elevator speed is the following formula:
Elevator speed=lifting height/travel time
Note: The travel time is the time from the base station to the highest level, without considering acceleration and deceleration.
The basic principle of elevator load capacity is the following formula:
CL=P*75KG P=Ar*INT Ar= BP*HC5/300s
Note: CL=Car load [Elevator load];
P=Passenger per car (car load with 80%);
Ar=Arrival Rate;
BP=building population [total number of people in the building];
INT=interpretation of interval [interval time];
HC=Handling capacity
After determining the basic principles, we will analyze residential products. According to China's Residential Design Code, for high-rise residential buildings with twelve floors or more, the number of elevators installed in each building should not be less than two. It is advisable to install an elevator that can accommodate stretchers. According to the international elevator standard CIBSE Guide D-1010, the recommended values are shown in the table below:
Note: INT=interpretation of interval [interval time];
HC=Handling capacity;
WT=Waiting time
As shown in the table above, the five minute transportation capacity for residential buildings should be between 6% and 8%. The average Houti time should be between 40S and 60S. For high-rise residential buildings, we can determine the number of elevators based on the positioning of residential products. Please refer to the following table (experience values) for details:
The elevator travel time can be calculated based on the lifting height by determining the elevator speed. The travel time can be determined based on the level of residence. Please refer to the following table (experience values) for details:
According to the international elevator standard CIBSE Guide D-1010, it is known that HC5 and INT can calculate the elevator load capacity according to the formula.
5、 Selection of configuration and key points of attention for super high-rise residential buildings
Firstly, we will analyze super high-rise buildings. Super high-rise buildings generally refer to buildings with a height exceeding 100 meters.
In addition to the basic configuration mentioned above, the design phase of super high-rise residential buildings should also focus on the following two points: the chimney effect and piston effect of elevators. The chimney effect is the difference in air density caused by the temperature difference between the inside and outside of a building, resulting in a pressure difference that promotes the flow of indoor and outdoor air. Indoor air with high temperature rises due to its low density and is discharged from the upper air outlet of the building. At this time, a negative pressure zone is formed in the original location of low-density air. Therefore, fresh air with lower outdoor temperature and higher density is sucked in from the bottom of the building, and the indoor and outdoor air sources continuously flow. This natural ventilation caused by thermal pressure is called the chimney effect. The chimney effect inside the shaft is directly proportional to factors such as lifting height, temperature difference inside and outside the shaft, and environmental pressure. The chimney effect is the result of the combined action of thermal pressure caused by indoor and outdoor temperature differences and outdoor wind pressure, usually the former being the main factor, and the thermal pressure value is directly proportional to the air density difference caused by indoor and outdoor temperature differences and the height difference of air inlet and exhaust outlets. This indicates that the higher the indoor temperature is compared to the outdoor temperature, the higher the building and the more pronounced the chimney effect. In theory, for a building, half of its height is considered as the neutral plane, and rooms below the neutral plane are considered to have air seeping in from outside, while rooms above the neutral plane are considered to have air seeping out from inside. The impact of different seasons is shown in Figure 3:
Figure 3: Performance of Chimney Effect in Different Seasons
The impact caused by the chimney effect in elevator shafts can be roughly divided into the following aspects:
(1) The flowing shaft air will squeeze out from the crack of the landing door, causing noise;
(2) Severe wind pressure can affect the opening and closing of elevators;
(3) When a fire occurs, the chimney effect can draw thick smoke or flames into the shaft, causing danger;
(4) The loss of energy is significant;
The national standard requires that the closing force to prevent the opening and closing of elevator doors should not exceed 150N. After consulting with the five major manufacturers of Hitachi, Otis, Mitsubishi, Thyssen, and Xunda, the design standard for the impact of chimney effect on opening and closing doors is based on a pressure of less than 100Pa on both sides of the elevator door.
How to reduce the impact of chimney effect during the design phase mainly includes the following points:
According to the table above, setting up a front chamber or partition in Houti Hall is the most economical and effective measure to reduce the chimney effect. This requires architects to give full consideration in the design of architectural schemes.
Secondly, for elevators in super high-rise buildings, attention should be paid to the piston effect. The speed at which high-speed elevators can transfer the surrounding air is usually faster than the speed at which the surrounding environment can transfer the displaced air. Air has the characteristics of viscosity and compressibility. When an elevator runs at high speed in a shaft, it will suck in air in the opposite direction of the elevator's movement, while compressing the air in the direction of the elevator's movement. When any possible gap (including the hall door gap) is found, this compressed air will be squeezed out, producing disturbing noise and vibration. This is the piston effect of elevator operation. Through research on various elevator manufacturers, the piston wind effect generally occurs in 5m/s high-speed single shaft elevators. The reasonable range of elevator blockage ratio is as follows:
To reduce the piston effect, we can take the following measures:
(1) Try to avoid the design of a single shaft and adopt a through shaft design, and control the elevator operation mode to avoid simultaneous descent or ascent of all elevators in the through shaft. The compressed air in a single shaft elevator has another space for diffusion in addition to its shaft, in order to reduce the pressure of the air inside the shaft and fundamentally reduce the adverse effects of the piston effect.
(2) There are large holes on the top and bottom pits of a single or double shaft that lead to the outside, and the area of the holes should preferably be equal to 1.5 times the area of the elevator car platform. Therefore, when the elevator car approaches the top and bottom floors, compressed air can diffuse outside the shaft.
Once again, attention should be paid to the impact of building sway on the elevator system in super tall buildings, which is generally considered only after the building height exceeds 250 meters. At present, the height of super high-rise residential buildings generally does not exceed this height, so this article will not discuss it.
6、 Selection of configuration for high-rise residential buildings and key points of attention
High rise residential buildings should also focus on issues such as shaft size, top flushing height, and foundation pit depth during the design phase. The height of the elevator's top and the depth of the foundation pit are directly proportional to the speed of the elevator. We compared the mainstream elevator models of five major manufacturers for high-rise residential buildings (using only 1000KG and 1050KG as examples). Please refer to the table below for details:
According to the analysis in the table above, it can be seen that there is little change in the size inside the car. The shaft sizes of the five major manufacturers are significantly different. The minimum width of the shaft is Xunda 2000mm and the maximum is Thyssen 2200mm. For depth, the minimum force is only 1820, while Mitsubishi's shaft depth reaches 2250mm. However, for the net area of the shaft, the minimum clearance is 3.95m2, while Mitsubishi's maximum is 4.83 m2. This requires architectural designers to determine the elevator brand and the corresponding shaft size during the scheme design. Otherwise, in the later construction project, the following situations may occur: if the size of the shaft is too small, it will cause the installation of the bidding brand elevator car to be impossible in the later stage. The cost of later engineering renovation will increase. However, excessive elevator shaft area can increase the shared area, leading to a decrease in the usable area of residential units. Secondly, the national standard "Urban Residential Area Planning and Design Standard" GB50180-2018 has been officially implemented this year. The height of the residence is limited to 80 meters. In cases where the roof construction area is small and the height limit is high, it is important to pay attention to the height of the roof. If the area of the elevator machine room is greater than 1/4 of the roof area, the height of the machine room should be recorded in the building height. It may exceed the height limit. For the top punching height, we can see that at the same speed (2.00m/s), Thyssen's minimum top punching height is 4050mm, while Hitachi's maximum top punching height is 4700mm. The installation of fire elevators is often involved in high-rise residential buildings. The "Code for Fire Protection Design of Buildings" GB 50016-2018 edition requires residential buildings with a height greater than 33 meters to be equipped with fire elevators, and the load capacity of fire elevators must not be less than 800KG. The time from the first floor to the top floor of elevators must not exceed 60S, and each floor must stop. So there are clear requirements for the speed and load selection of fire elevators.
7、 Selection and Key Points of Attention for Multi story Residential and Villa Configuration
For multi story residential buildings equipped with elevators, garden villas and villas generally consider quality when choosing elevators. Therefore, for elevators, secondary decoration is generally carried out. This requires special attention to the reserved weight and weak current function of elevators during elevator design and selection. We will still use mainstream models from the five major manufacturers as examples. Please refer to the table below for details:
As shown in the table above, the maximum reserved weight for decoration of 1000 (1050) KG by the five major manufacturers is generally 250-400 KG without system upgrade. Due to the low height of multi story residential buildings, the weight of accompanying cables and steel wire ropes is relatively light, so they can generally reach the maximum reserved weight for decoration. The next thing to pay attention to is the integration of elevators and weak current information systems in residential communities. High end garden villas have product types for elevator entry, which requires setting up elevator permissions. Owners must swipe their cards to select floors. For visitors and owners, they can confirm with the elevator through the walkie talkie system and connect with it. Authorize visitors to the destination layer. It involves the integration of visual intercom systems and elevator control systems.
The subdivision of villa products is generally divided into standalone buildings, townhouses, stacked units, etc. Developers can divide the development process of villa products into two situations: configuring elevators and reserving conditions. Regardless of the situation, according to the characteristics of the product, inorganic room, low load, and low-speed elevator products will be used. For products with reserved conditions, developers usually reserve elevator shafts, and the elevators are purchased by the owners themselves during the secondary decoration. When reserving a shaft, the structure usually opens an opening at the floor slab, and beams are installed around the opening for reinforcement. If the size of the shaft is too small, it will cause the owner to dismantle the beam and then reinforce it, leaving a safety hazard. Therefore, when reserving a shaft, it must be reserved according to the maximum size. Due to the low load capacity and low speed of villa elevators. There will be no additional cost when owners choose elevators.
To provide readers with an intuitive direction for configuration selection, we conducted a comprehensive comparative analysis of super high-rise, high-rise, multi story, and villa buildings. Taking Xunda as an example, please refer to the following table for details:
As can be seen from the above table, the basic trend of elevators in super high-rise buildings is high speed, large load capacity, and large machine rooms. This is also determined by the characteristics of super high-rise buildings, which have high building height and high lifting height, and the corresponding traction system requirements are high. So the overall parameter configuration needs to be improved to meet the capacity requirements. For super high-rise buildings, we usually set up zones. For ordinary mid to high rise buildings, the elevator configuration tends towards small machine rooms, commonly used speeds, and basic load capacity. For multi story and villa buildings, the basic trend is towards no machine rooms, low load capacity, and low speed. The height of the top and the size of the foundation pit will increase with the increase of the load.
From the user's perspective, the safety of the elevator is the most important concern for users, and the most intuitive feeling for users is the experience of riding the elevator. The safety of elevators involves product quality, brand influence, operation and maintenance status, and emergency plans. From a development perspective, the elevators chosen by mainstream real estate developers are all mainstream brands in the market, and customers have a high recognition of their quality and brand. So operation, maintenance, and emergency plans have become the main factors determining safety. At present, mainstream brand manufacturers have operation and maintenance centers in various cities, and each elevator has functions such as real-time monitoring and automatic accident alarm. And the experience involves several other aspects of the elevator: the speed of the elevator, the selection of the Houti Hall entrance, and the interior decoration effect of the elevator. Choosing too fast a speed can cause discomfort such as tinnitus to passengers, the selection of the entrance of Houti Hall can directly affect the decoration effect of the lobby, and the internal decoration of the elevator is a determining factor in the visual experience of passengers.
8、 The future development trend of elevators
At present, from the development of elevators, there have been double car elevators to improve single capacity and automatic elevator dispatch systems to achieve better personnel diversion. And currently, the cordless elevator developed by ThyssenKrupp has been applied. The cordless elevator breaks the constraints of the shaft and can move vertically and horizontally. A huge breakthrough has been achieved in the transportation form of traditional elevators. Please refer to Figure 4 for details:
Figure 4: Schematic diagram of cordless elevator
But with the continuous development of the Internet of Things and cloud technology, the real-time operation information and key indicator parameters of each elevator are uploaded to the cloud platform through the establishment of an elevator information exchange network, which is managed by elevator manufacturers or other responsible organizations to achieve information sharing and exchange. The elevator Internet of Things achieves intelligent supervision of elevator safety by configuring a data system with operational parameter collection function.
