阅读说明：本技术 一种基于公共楼层安全用消防系统的施工方法 (Construction method based on public floor safety fire fighting system ) 是由 李振东 卢娟 于 2019-11-29 设计创作，主要内容包括：本发明公开了一种基于公共楼层安全用消防系统的施工方法,可以实现在施工过程中加强与公共楼层其它现有系统的联系,采用消防系统集中控制的方式,调用公共楼层已有的一切资源协助消防系统的展开运行,同时在火灾发生时可以及时迅速的构建火灾信息收集网和人群疏散逃生网,通过灭火和自救的双重展开掌握消防主动权,一方面可以统筹规划消防资源进行合理高效的灭火救援,另一方面可以快速安全的引导广大人民群众以正确的方式逃生,在降低火灾带来的损失和危害的同时,尽可能的减少人身财产损失,另外还可以配合消防中心进行消防工作,提供消防资源的协助包括火灾信息、被困人群信息等,将火灾损失程度控制到最低。(The invention discloses a construction method of a fire-fighting system based on public floor safety, which can strengthen the connection with other existing systems of the public floor in the construction process, adopts a fire-fighting system centralized control mode to call all resources existing in the public floor to assist the expansion operation of the fire-fighting system, can timely and quickly construct a fire information collection network and a crowd evacuation escape network when a fire occurs, and grasps the fire-fighting initiative through the double expansion of fire fighting and self-rescue, on one hand, can comprehensively plan the fire-fighting resources to carry out reasonable and efficient fire-fighting rescue, on the other hand, can quickly and safely guide the masses to escape in a correct mode, reduces the loss and harm caused by the fire, and simultaneously reduces the personal and property loss as much as possible, and can also cooperate with a fire-fighting center to carry out fire-fighting work to provide the assistance of the fire-fighting resources, including fire information, fire information and, Information of trapped people and the like, and the fire loss degree is controlled to be the lowest.)

1. A construction method based on a fire fighting system for public floor safety is characterized in that: the method comprises the following steps:

s1, actually inspecting the characteristics of the public floors on site, and calculating and determining the pipe diameter of the fire-fighting system and the parameters of the water pump under the guidance of fire-fighting regulations according to the construction drawing; selecting diameters of a main pipe and a branch pipe, selecting specifications of spray heads, arranging a pipeline plane, arranging a fire box and arranging a fire pump station plane, and reporting the authorization approval of related departments;

s2, fire-fighting equipment and materials are put into the field and stacked according to the standard, and spot constructors complete sampling inspection under the supervision of third-party detectors, so that the equipment and the materials are qualified and can be put into use;

s3, synchronously burying a fire-fighting main pipe during the concrete pouring construction of the raft foundation, and simultaneously completing the connection between a horizontal branch pipe and a vertical branch pipe between different floors in the same floor, wherein an electric gate valve is installed at the position, 800mm, of the vertical branch pipe, which extends out of the concrete raft foundation, and the horizontal branch pipe is provided with the electric gate valve, a three-way pipe and a fire-fighting box at proper positions;

s4, leading out a spray pipeline from the horizontal branch pipe at the top of each floor, and installing a spray head, a spray water pump, a fire-fighting starter and a fire-fighting special camera;

s5, sampling after each batch of pipes and nozzles are installed, performing a hydraulic test, performing a leakage test on the electric gate valves one by one, replacing the electric gate valves if the electric gate valves are unqualified, and entering the next procedure if the electric gate valves are qualified;

s6, constructing a linkage type control network, networking a fire fighting system with the existing system of a public floor, and arranging a fire fighting control room to be controlled by the fire fighting control room in a centralized manner;

s7, a fire-fighting indication projection lamp and a voice broadcast device are further mounted at the top of each floor, the fire-fighting indication projection lamp points to a nearby fire-fighting emergency channel, and the voice broadcast device broadcasts voice prompts in a circulating mode;

s8, installing and connecting the fire pump station with a fire main pipe, and monitoring the basic capacity of a water tank of the fire pump station in real time through a water level sensor to ensure that the fire pump is always in an emergency state;

s9, a remote data transmission platform is constructed by the fire control room and the fire control center, and public floor fire control information is shared in real time.

2. A construction method of a fire fighting system for public floor security according to claim 1, characterized in that: the fire control starter includes at least one of smoke transducer and infrared inductor, and fire control starter and shower nozzle, spray pump and the equal electric connection of special camera of fire control.

3. A construction method of a fire fighting system for public floor security according to claim 1, characterized in that: the special camera for fire fighting comprises an infrared imaging module and a data transmission module, wherein the data transmission module is connected with a fire fighting control room, and the data transmission module adopts a GSM module.

4. A construction method of a fire fighting system for public floor security according to claim 1, characterized in that: a fire-fighting priority control system is installed in the fire-fighting control room and is connected with a ventilation system, an elevator system, a lighting system and a public power supply system through a wireless connection module.

5. The construction method of the fire fighting system for public floor security according to claim 4, wherein: the wireless connection module adopts an NRF24L01 chip working at a 2.4GHz frequency band.

6. A construction method of a fire fighting system for public floor security according to claim 1, characterized in that: the fire emergency passage entrance is provided with an escape number estimating unit, the escape number estimating unit is connected with a fire indication projection lamp and a voice broadcast device on the same floor, the fire indication projection lamp comprises at least one projection image, and the voice broadcast device comprises at least one voice recorded in advance.

7. A construction method of a fire fighting system for public floor security according to claim 1, characterized in that: the elevator system comprises at least one elevator, and a fire-fighting indication projection lamp and a voice broadcast device are installed beside each elevator.

8. A construction method of a fire fighting system for public floor security according to claim 6, characterized in that: the number of people of fleing estimates unit includes gravity sensor and microprocessor, the pre-buried first floor ladder of installing at fire emergency passageway entrance of gravity sensor is connected with time-recorder and wireless signal transmitter on the microprocessor, microprocessor controls wireless signal transmitter and sends crowded signal after 5s detects setting for the weight through gravity sensor and time-recorder in succession, microprocessor controls wireless signal transmitter and sends evacuation signal after 3s detects not reach setting for the weight through gravity sensor and time-recorder in succession.

9. A construction method of a fire fighting system for public floor security according to claim 1, characterized in that: the pipeline of fire control person in charge, horizontal branch pipe and vertical branch pipe all connects in parallel and is provided with two at least booster pumps, be connected with public power supply system and self-contained power simultaneously on the delivery pump, and switch over to self-contained power after public power supply system outage by oneself.

10. A construction method of a fire fighting system for public floor security according to claim 1, characterized in that: fire control starter, fire control instruction projection lamp and voice broadcast ware all are equipped with two at least independent emergency power supply of way.

Technical Field

The invention relates to the technical field of electromechanical equipment engineering construction, in particular to a construction method of a fire protection system for public floor safety.

Background

The electromechanical equipment generally refers to machinery, electrical equipment and electrical automation equipment, and in a building, the electromechanical equipment is generally called machinery and pipeline equipment except for earthwork, carpentry, reinforcing steel bars and muddy water. With the continuous improvement of the living standard of people, people have more and more demands on electromechanical equipment in daily life, and the electromechanical equipment from vehicles to various household appliances, computers, printers and the like becomes indispensable electromechanical products in the life of people. The advanced electromechanical equipment not only can greatly improve the labor productivity, reduce the labor intensity, improve the production environment and finish the work which can not be finished by manpower, but also has direct and important influence on the development of the whole national economy, the improvement of the science and technology and the national defense strength as one of the national industrial foundations, and is also an important mark for measuring the national science and technology level and the comprehensive national strength.

Electromechanical equipment installation engineering is an indispensable important component in constructional engineering, is a large concept, and involves more subjects and professions. The method comprises the installation of various devices, water supply and drainage, electric, heating, ventilation, fire protection, communication and automatic control systems in industrial, civil and public works. The device has the inherent characteristics, but has strong universality. The construction activities of the building construction method are from equipment purchase, to installation, debugging, production operation and completion acceptance stages, and finally the use functions of the building are met. In the electromechanical installation construction process, the novel technology, the novel process, the novel material, the novel equipment and other emerging technologies are adopted in the construction process. The requirements of large-scale T-range on hoisting, assembling and detecting technologies are higher and higher, so that the construction technology and construction equipment need to be continuously updated. The acceptance of the electromechanical installation through construction quality is obviously different from that of a building structure, and the method is mainly characterized by differences of a quality evaluation method, engineering acceptance and after-sale service means. However, due to the construction and installation technology of building mechanics and electricity, the diversity of materials and the complexity of the process, a large amount of manpower and material resources are required to be invested in the actual construction process, and each construction unit and related engineering units are required to have abundant construction experience and experience. The electromechanical installation project runs through the whole project construction process, the main part starts construction after the structural project is finished, and basically finishes before the decorative project is started, so that the electromechanical installation project has important influence on the whole construction period; the quality of electromechanical installation engineering plays a key role in using functions after completion of the project, and construction units are required to strictly control the construction process.

The fire-fighting system belongs to one type of electromechanical equipment engineering, plays a role in lifting weight in the life of people, and plays a role in keeping people away from fire threats and guaranteeing personal and property safety, in modern society, as the living standard of people is improved and land resources are effectively utilized, more and more high-rise buildings are pulled out of the ground, wherein the construction of the fire-fighting system is an important part, the fire-fighting accidents are particularly easy to happen under the emergency condition due to the existence of various electric power equipment and other fire hidden dangers of large commercial buildings, and a large number of people are gathered continuously, once the accident loss is not imaginable due to the fact that the existing fire-fighting system facilities of the public floors are relatively complete, but are relatively self-closed during installation and construction, namely, the fire-fighting system facilities are relatively few in contact with other electromechanical equipment and only play a fire-fighting function, therefore, a fire-fighting system project which can be linked with other electromechanical equipment is urgently needed, loss is reduced to the maximum extent when a fire comes, and personal and property injuries of the masses of people are reduced to the minimum as possible.

Disclosure of Invention

1. Technical problem to be solved

Aiming at the problems in the prior art, the invention aims to provide a construction method of a fire-fighting system based on public floor safety, which can strengthen the connection with other existing systems of a public floor in the construction process, adopts a fire-fighting system centralized control mode to call all the existing resources of the public floor to assist the expansion operation of the fire-fighting system, can construct a fire information collection network and a crowd evacuation escape network in time and rapidly when a fire occurs, masters the fire-fighting initiative through the double expansion of fire fighting and self-rescue, can comprehensively plan the fire-fighting resources to carry out reasonable and efficient fire-fighting rescue on the one hand, can rapidly and safely guide the masses of people to escape in a correct mode on the other hand, reduces the loss and the harm caused by the fire, reduces the personal and property loss as much as possible, and can also cooperate with a fire-fighting center to carry out fire-fighting work, the assistance of providing the fire fighting resources comprises fire information, information of trapped people and the like, and the degree of fire loss is controlled to be minimum.

2. Technical scheme

In order to solve the above problems, the present invention adopts the following technical solutions.

A construction method of a fire fighting system based on public floor safety comprises the following steps:

s1, actually inspecting the characteristics of the public floors on site, and calculating and determining the pipe diameter of the fire-fighting system and the parameters of the water pump under the guidance of fire-fighting regulations according to the construction drawing; selecting diameters of a main pipe and a branch pipe, selecting specifications of spray heads, arranging a pipeline plane, arranging a fire box and arranging a fire pump station plane, and reporting the authorization approval of related departments;

s2, fire-fighting equipment and materials are put into the field and stacked according to the standard, and spot constructors complete sampling inspection under the supervision of third-party detectors, so that the equipment and the materials are qualified and can be put into use;

s3, synchronously burying a fire-fighting main pipe during the concrete pouring construction of the raft foundation, and simultaneously completing the connection between a horizontal branch pipe and a vertical branch pipe between different floors in the same floor, wherein an electric gate valve is installed at the position, 800mm, of the vertical branch pipe, which extends out of the concrete raft foundation, and the horizontal branch pipe is provided with the electric gate valve, a three-way pipe and a fire-fighting box at proper positions;

s4, leading out a spray pipeline from the horizontal branch pipe at the top of each floor, and installing a spray head, a spray water pump, a fire-fighting starter and a fire-fighting special camera;

s5, sampling after each batch of pipes and nozzles are installed, performing a hydraulic test, performing a leakage test on the electric gate valves one by one, replacing the electric gate valves if the electric gate valves are unqualified, and entering the next procedure if the electric gate valves are qualified;

s6, constructing a linkage type control network, networking a fire fighting system with the existing system of a public floor, and arranging a fire fighting control room to be controlled by the fire fighting control room in a centralized manner;

s7, a fire-fighting indication projection lamp and a voice broadcast device are further mounted at the top of each floor, the fire-fighting indication projection lamp points to a nearby fire-fighting emergency channel, and the voice broadcast device broadcasts voice prompts in a circulating mode;

s8, installing and connecting the fire pump station with a fire main pipe, and monitoring the basic capacity of a water tank of the fire pump station in real time through a water level sensor to ensure that the fire pump is always in an emergency state;

s9, a remote data transmission platform is constructed by the fire control room and the fire control center, and public floor fire control information is shared in real time.

Further, the fire control starter includes at least one in smoke transducer and the infrared inductor, and the fire control starter and shower nozzle, spray pump and the equal electric connection of special camera of fire control, and the fire control starter adopts multiple starting mode can ensure that fire extinguishing system can in time start, and the time is taken for the rescue and relief work minutes.

Furthermore, the camera special for fire fighting comprises an infrared imaging module and a data transmission module, the data transmission module is connected with a fire control room, the data transmission module adopts a GSM module, the infrared imaging function can avoid that an ordinary camera cannot acquire images with effective information under the dense smoke environment of fire, meanwhile, the heat distribution of the infrared imaging function can well judge the fire conditions such as fire behavior and the like, the fire control room can conveniently carry out overall planning and the most reasonable utilization on fire fighting resources according to the fire severity of different positions, so that the fire fighting and rescue work can be efficiently and qualitatively completed, even the specific positions of trapped people can be analyzed, the fire fighting resources can be allocated in a targeted manner when fire fighting is carried out, the fire fighting efficiency is improved, and fire fighters can plan rescue routes by means of the specific positions provided by the infrared images when rescuing the trapped people, the trapped people can be rescued in the shortest time, and a route guarantee and a time guarantee are provided for rescue.

Furthermore, install fire control priority control system in the fire control room, fire control priority control system is connected with ventilation system, elevator system, lighting system and public power supply system through wireless connection module, wireless connection carries out the wiring that the advantage of remote control lies in that on the one hand can avoid wired connection, practice thrift time limit for a project, cost and construction process, on the other hand wired connection inefficacy hidden danger when the conflagration takes place is great, in case the coordinated control of the back fire control priority control system that loses efficacy sinks into the paralysis back, be unfavorable for fire control system's comprehensive expansion, can't in time carry out the assistance of other systems through fire control priority control system, can improve conflagration loss and casualties greatly in probably invisibly, and wireless connection then can be fine avoid this problem, it has still stably realizes remote data transmission's function under the conflagration.

Further, the wireless connection module adopts an NRF24L01 chip operating in a 2.4GHz band.

Furthermore, fire emergency passageway entrance is provided with the number of fleing unit of estimating, and flees the number of estimating the unit and is connected with the fire control of same floor and instructs projection lamp and voice broadcast ware, the fire control instructs the projection lamp to include at least a kind of projection image, the voice broadcast ware includes at least one kind of pronunciation of recording in advance, and the number of fleing estimates the unit and can estimate the number of fleing in this fire emergency passageway, then indicates projection lamp and voice broadcast ware feedback crowd or evacuation signal to fire control because the biggest effect of the performance that just can be safe of fire emergency passageway of preventing under the prerequisite of reasonable number of people.

Furthermore, the elevator system comprises at least one elevator, a fire-fighting indication projection lamp and a voice broadcast device are installed beside each elevator, people always escape from the elevator in a strange environment under the first reaction, the elevator is stopped to ensure that the people cannot get in danger in the elevator taking process, and the fire-fighting indication projection lamp and the voice broadcast device can rapidly guide the people to escape.

Further, the number of people escaping from the fire emergency channel is estimated by the number estimating unit comprising a gravity sensor and a microprocessor, the gravity sensor is pre-embedded and installed on a first step at the entrance of the fire emergency channel, a timer and a wireless signal transmitter are connected to the microprocessor, the microprocessor controls the wireless signal transmitter to send a congestion signal after detecting the set weight for 5 consecutive times through the gravity sensor and the timer, the microprocessor controls the wireless signal transmitter to send an evacuation signal after detecting the weight for 3 consecutive times through the gravity sensor and the timer, specifically, the gravity sensor detects the weight once every 1s and sends data to the microprocessor, the number of people escaping from the fire emergency channel can be judged to be large after 5 consecutive times of exceeding the set weight, the increasing of people affects the escaping speed or even possibly steps on accidents, and the situation that the fire emergency channel still has surplus space for people to escape from the groups can be judged if 3 consecutive times of not exceeding the set Wherein the set quantity is calculated according to the step width of the fire emergency passage, and the calculation formula of the set weight is the step width (m) × 75kg/0.5 m.

Further, all parallelly connected two at least booster pumps that are provided with on the pipeline of fire control person in charge, horizontal branch pipe and vertical branch pipe, be connected with public power supply system and self-contained power supply on the delivery pump simultaneously, and switch over to self-contained power supply by oneself after public power supply system cuts off the power supply, ensure to come temporarily at the conflagration, the booster pump plays the effect of having prepared without suffering on fire control person in charge, horizontal branch pipe and the vertical branch pipe, provides the guarantee of putting out a fire under emergency.

Further, fire control starter, fire control instruction projection lamp and voice broadcast ware all are equipped with two at least independent emergency power supply of way, even under the unable condition of using of public power supply system, fire control starter, fire control instruction projection lamp and voice broadcast ware also can rely on independent emergency power supply to accomplish work, guarantee fire extinguishing system's normal start and the normal guide of crowd of taking refuge.

3. Advantageous effects

Compared with the prior art, the invention has the advantages that:

(1) the scheme can strengthen the connection with other existing systems of the public floor in the construction process, adopts the centralized control mode of the fire-fighting system, calls all the existing resources of the public floor to assist the expansion and the operation of the fire-fighting system, meanwhile, a fire information collecting net and a crowd evacuation and escape net can be constructed rapidly and timely when a fire occurs, the initiative right of fire fighting is mastered through the double expansion of fire fighting and self-rescue, on one hand, the fire fighting resources can be planned comprehensively for reasonable and efficient fire fighting and rescue, on the other hand, the fire fighting and rescue device can rapidly and safely guide the masses to escape in a correct way, the loss and the harm that reduce the conflagration and bring, reduce personal and property loss as far as, can also cooperate the fire control center to carry out fire control work in addition, provide the assistance of fire control resource and include conflagration information, stranded crowd information etc. with conflagration loss degree control to minimumly.

(2) The fire control starter includes at least one in smoke transducer and the infrared inductor, and the equal electric connection of fire control starter and shower nozzle, spray pump and the special camera of fire control, and the fire control starter adopts multiple starting mode can ensure that fire extinguishing system can in time start, and the time is taken for the minute of fighting a rescue and relief work.

(3) The camera special for fire fighting comprises an infrared imaging module and a data transmission module, the data transmission module is connected with a fire control room, the data transmission module adopts a GSM module, the infrared imaging function can avoid that a common camera cannot acquire images with effective information under the dense smoke environment of fire, meanwhile, the heat distribution of the infrared imaging function can well judge the fire situations such as fire behavior and the like, the fire control room can conveniently carry out overall planning and the most reasonable utilization on fire fighting resources according to the fire severity degrees of different positions, so that the fire fighting and rescue work can be efficiently and qualitatively completed, even the specific position of trapped people can be analyzed, the fire fighting resources can be allocated pertinently when fire fighting is carried out, the fire fighting efficiency is improved, and fire fighters can plan rescue routes by depending on the specific position provided by the infrared images when rescuing the trapped people, the trapped people can be rescued in the shortest time, and a route guarantee and a time guarantee are provided for rescue.

(4) Install fire control priority control system in the fire control room, fire control priority control system is connected with ventilation system through wireless connection module, elevator system, lighting system and public power supply system, wireless connection carries out the wiring that wired connection can be avoided on the one hand to the advantage that the remote control was carried out to wireless connection, practice thrift the time limit for a project, cost and construction process, on the other hand wired connection inefficacy hidden danger when the conflagration takes place is great, in case the coordinated control of the back fire control priority control system that loses efficacy sinks into paralysed back, be unfavorable for the comprehensive expansion of fire control system, can't in time carry out the assistance of other systems through fire control priority control system, can improve conflagration loss and casualties greatly in probably intangible, and this problem of avoiding that wireless connection then can be fine, it has.

(5) The wireless connection module adopts an NRF24L01 chip working at a 2.4GHz frequency band.

(6) The fire emergency passageway entrance is provided with the number of fleing and estimates a number unit, and the number of fleing estimates a number unit and is connected with the fire indication projection lamp and the voice broadcast ware of same floor, the fire indication projection lamp includes an at least projection image, the voice broadcast ware includes at least one pronunciation of recording in advance, the number of fleing estimates a number unit can estimate the number of fleing in this fire emergency passageway, then to fire indication projection lamp and voice broadcast ware feedback crowd or evacuation signal, because only the biggest effect of performance that emergency passageway could be safe is prevented in the extinction under the prerequisite of reasonable number.

(7) The elevator system comprises at least one elevator, a fire-fighting indication projection lamp and a voice broadcast device are installed beside each elevator, people always escape from the elevator from the top in a strange environment due to a first reaction, the elevator stops running to ensure that the people cannot take the elevator to cause danger, and the fire-fighting indication projection lamp and the voice broadcast device can rapidly guide the people to escape.

(8) The escape people number estimating unit comprises a gravity sensor and a microprocessor, the gravity sensor is pre-embedded and installed on a first-layer ladder at the entrance of the fire-fighting emergency channel, the microprocessor is connected with a timer and a wireless signal transmitter, the microprocessor controls the wireless signal transmitter to send a congestion signal after detecting the set weight for 5 consecutive seconds through the gravity sensor and the timer, the microprocessor controls the wireless signal transmitter to send an evacuation signal after detecting the weight which is not reached to the set weight for 3 consecutive seconds through the gravity sensor and the timer, specifically, the gravity sensor detects the weight once every 1 second and sends data to the microprocessor, the escape people number of the fire-fighting emergency channel can be judged to be more after 5 consecutive times of exceeding the set weight, the escape speed is influenced or even a treading accident can be caused if the escape speed is continuously increased, and the fire-fighting emergency channel can be judged to have surplus space for people, the set quantity is calculated according to the step width of the fire emergency passage, and the calculation formula of the set weight is the step width (m) × 75kg/0.5 m.

(9) The pipeline of the fire-fighting main pipe, the pipeline of the horizontal branch pipe and the pipeline of the vertical branch pipe are all provided with at least two booster pumps in parallel, the delivery pump is simultaneously connected with a public power supply system and a self-contained power supply, and the public power supply system is automatically switched to the self-contained power supply after being powered off, so that the effect that the booster pumps have a standby effect or no trouble on the fire-fighting main pipe, the horizontal branch pipe and the vertical branch pipe is ensured when a fire disaster comes, and the fire-fighting guarantee is provided under emergency conditions.

(10) Fire control starter, fire control instruction projection lamp and voice broadcast ware all are equipped with two at least independent emergency power supply, even under the unable circumstances of using of public power supply system, fire control starter, fire control instruction projection lamp and voice broadcast ware also can rely on independent emergency power supply to accomplish work, guarantee fire extinguishing system's normal start and the normal guide of crowd of taking refuge.

Drawings

FIG. 1 is a block diagram of the main flow of the present invention;

fig. 2 is a schematic structural diagram of an escape people number estimation unit according to the present invention.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention; it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by those skilled in the art without any inventive work are within the scope of the present invention.

In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "top/bottom", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise specifically stated or limited, the terms "mounted," "disposed," "sleeved/connected," "connected," and the like are used in a broad sense, and for example, "connected" may be a fixed connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection, a direct connection, an indirect connection through an intermediate medium, and a communication between two elements.