CN113158300A - BIM-based building fire easy ignition point determination method - Google Patents
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Abstract
The invention relates to a building fire easy ignition point determination method based on BIM, which comprises the following specific steps: (1) building model construction and optimization; (2) building exterior ambient light environment simulation based on BIM; (3) building periphery wind environment simulation based on BIM; (4) building indoor wind environment simulation based on BIM; (5) BIM-based building fire susceptibility determination strategies. The invention has the advantages that: 1) a method for simulating the peripheral wind environment and the solar radiation of a building is provided; 2) the fire numerical simulation is carried out on the building, so that the rule of smoke spreading in the building and the determination of the critical value which has harmful influence on human bodies are disclosed; 3) the position of the easy ignition point of the building when the fire occurs is scientifically determined, and the disaster is effectively reduced; 4) providing scientific theoretical basis and technical support for preventing fire of buildings.
Description
Technical Field
The invention discloses a BIM-based method for determining a fire point of a building, which belongs to the technical field of resources and environments.
Background
In the twentieth century, most of Chinese people live in flat houses, low-rise residential buildings, shopping malls and other public buildings rarely have high floors, and in the twenty-first century, high-rise buildings and even super high-rise buildings are all the same. The change of buildings brings a series of problems, the requirements of people on various aspects such as water, electricity, fire protection, traffic and the like are increased, along with the improvement of national quality, people pay more attention to personal safety and the aspects of fire prevention, ventilation, lighting and the like of houses, however, in the current society, along with the improvement of technological level, the fire occurrence frequency is higher and higher, and the occurrence of fire has great influence on various aspects such as personal property, ecological environment and the like, so that the occurrence of the fire can be effectively prevented and becomes a hot topic of the current society.
The increase of the population of China increases the demand for housing, and the price of land is continuously increased, so that various high-rise buildings, even super high-rise buildings, such as houses, markets, libraries, teaching buildings and the like are generated, and the fire occurrence rate of the high-rise buildings, even the super high-rise buildings, is higher and higher. Therefore, the fire disaster is still one of the most common and frequent disasters in the current society, and the life health, ecological environment and social development of people are seriously threatened and hindered.
The fire hazard is sudden and strong, the produced hazard is big, and is not easy to control, once a fire hazard occurs, the produced smoke and heat can be rapidly diffused in the building, and the life safety of personnel in the building is seriously threatened. Therefore, the flowing rule of smoke in a fire scene is mastered, research and analysis are carried out according to data, and the ignition point position where the fire easily occurs in the building can be determined, so that the fire can be controlled timely, personnel can be safely evacuated, casualties are reduced, and the possibility of fire occurrence can be reduced to a great extent even. The invention analyzes the fire hazard of the building, comprehensively identifies various factors influencing the fire hazard, explores the development and change of the fire hazard factors under different conditions, utilizes fire hazard numerical simulation software to carry out numerical simulation on the fire hazard smoke spreading process of the library under the hazard factors, grasps the smoke flow rule of the library, provides great help for decision of fire fighters, enables the work of prevention, fire extinguishment, self-rescue and safety management to be better carried out, and provides guidance suggestions for prevention of building fire and rescue of the staff in future.
The main factor of light environment simulation is solar radiation, which is an energy source and basic power of the physical process and biological process of the earth ecosystem, the wind environment simulation is mainly carried out according to the local climatic conditions and the actual conditions, and the solar radiation and wind are one of the important factors considered for protecting and reconstructing the urban ecosystem. In the process of developing urbanization construction, interaction with solar radiation and wind environment needs to be considered in many aspects of building design, so that utilization and development intensity of solar radiation energy and wind energy are improved. In the research of the method for determining the easy ignition point of the building fire, light environment simulation and wind environment simulation are two indispensable parts, supplement each other, and are combined with factors such as the self material of the building, so that the easy ignition point of the building can be effectively determined, the probability of the fire occurrence is reduced, and all losses brought after the fire occurrence are reduced.
Building of Building Information Modeling (BIM) is a revolution in the Building field, and has undergone the stages of germination, generation and development from the proposal of BIM technical idea to the present. The building information model is established on the basis of taking various relevant information data of the building engineering project as a model, and simulates the real information of a building through digital information, and has the characteristics of completeness, information consistency, visualization, harmony, simulation, optimization and drawing property. The BIM information model is established by means of multi-software collaborative design of a unified information interaction platform, and forms a plurality of pieces of software capable of supporting information exchange under the BIM concept, wherein the software comprises various types of software such as modeling software, green analysis software, structural analysis software, equipment design software, deepening design software and the like. The BIM provides a large amount of data information for deep processing and recycling for the production and management of projects, effectively manages and utilizes the massive information and big data, and needs the support of a data management system. Meanwhile, each BIM system processes large models and large data generated by complex services, and higher requirements are put forward on computing capacity and low-cost mass data storage capacity. With the development of technology, the BIM technology will eventually enter the mobile application era.
Disclosure of Invention
The invention provides a BIM-based method for determining a building fire easy ignition point, which aims to research the method for determining the ignition point of the building easily causing fire, fully combine a BIM model, a solar radiation model and a flow field model, rely on model data, combine the material characteristics of the building and the actual conditions of local climate, construct a building outdoor luminous environment and wind environment simulation prediction model and an indoor wind environment simulation prediction model, combine a numerical simulation analysis method, summarize and analyze factors influencing the building fire development trend, solve the problem of determining the existing building easy fire position, effectively determine the position of the easy ignition point when the building fire occurs, and provide scientific theoretical basis and technical support for preventing the fire of the building.
The technical solution of the invention is as follows: a BIM-based building fire easy ignition point determination method comprises the following steps:
(1) building model construction and optimization
(2) BIM-based building external ambient light environment simulation
(3) Building peripheral wind environment simulation based on BIM
(4) BIM-based building indoor wind environment simulation
(5) BIM-based building fire easy ignition point determination strategy
Building and optimizing a building model in the step (1): a Building Information Model (BIM) component is carried out by using a three-dimensional modeling technology, a planar graph of a building drawn by using a two-dimensional modeling technology is established by using the three-dimensional modeling technology, and the building model is established and optimized by drawing the building and the structural engineering of the building and setting various parameters.
Building external ambient light environment simulation based on BIM in the step (2): the method comprises the steps of applying a sustainable building design and an analysis tool under the BIM technology, conducting information interoperability on a model obtained by applying the three-dimensional modeling technology by deriving a required format, conducting research on the model by applying a related sustainable building design and the analysis tool, conducting simulation analysis on data such as local actual conditions and horizontal plane radiation intensity, conducting effect rendering by using an effect renderer of the related building light environment simulation technology during light environment simulation and analysis, enabling the actual conditions to be presented in a most intuitive form, and outputting corresponding data through building light environment simulation analysis, so that building external light environment simulation based on the BIM is achieved.
Building peripheral wind environment simulation based on BIM in the step (3): the model obtained by the three-dimensional modeling technology is mutually used by deriving the required format, the model is simulated and analyzed according to the local actual conditions and the weather conditions by using the sustainable building design and analysis tool under the BIM technology and combining the weather data of all places in the weather tool, and the peripheral flow field analysis diagram received by the building under different environments in four seasons is derived by combining the material of the building, so that the building peripheral wind environment simulation based on the BIM is realized.
Building indoor wind environment simulation based on BIM in the step (4): the method comprises the steps of conducting information interoperability on a model obtained by applying three-dimensional modeling through deriving a required format, conducting indoor wind environment simulation on a building through wind speed and temperature data of a city in a meteorological tool in four seasons by applying a CFD (Computational Fluid Dynamics) technology, obtaining wind speed and pressure change inside the building through analysis, and realizing building indoor wind environment simulation based on BIM through data comparison.
The building fire easy ignition point determination strategy based on BIM in the step (5) comprises the following steps: the method is characterized in that the ignition point of the building where the fire easily occurs is judged by combining building peripheral light environment simulation based on the BIM, building peripheral wind environment simulation based on the BIM, building indoor wind environment simulation based on the BIM and combining various factors such as the structure of the building, the characteristics of the building and the materials of the building, so that the building fire easily ignition point determining strategy based on the BIM is realized.
The invention has the beneficial effects that: a complete, scientific and effective BIM-based method for determining a building fire easy ignition point is provided, under the support of a building information technology, a building is taken as a research object, a building information model is established with the aim of determining the building fire easy ignition point, fine expression and planning of building information are completed, a prediction model for simulating an outdoor light environment and an indoor wind environment of the building is established by combining a solar radiation model and a flow field model, quantitative evaluation on building fire is carried out, and finally strategies and measures for determining the building easy ignition point are provided according to local actual seasonal conditions of the building and material characteristics of the building. The invention further expands the application of the building information technology in building fire fighting, and enriches the theory and method of cross fusion of multiple subjects such as geography, aerology and architecture in the research of the easy ignition point of the fire of the building.
Drawings
FIG. 1 is a basic procedure and technical idea of a BIM-based method for determining a fire point of a building.
In the figure, step (1) is denoted by 101, step (2) is denoted by 102, step (3) is denoted by 103, step (4) is denoted by 104, and step (5) is denoted by 105.
Detailed Description
The present invention is further illustrated by the following figures and detailed description of the drawings, it is to be understood that these examples are given solely for the purpose of illustration and are not intended as a definition of the limits of the invention, since various equivalent modifications will become apparent to those skilled in the art upon reading the present disclosure, and are intended to be included within the scope of the appended claims.
As shown in fig. 1, the building fire easy ignition point determining method based on BIM includes the following steps:
(1) building model construction and optimization (101)
(2) BIM-based building peripheral light environment simulation (102)
(3) BIM-based building peripheral wind environment simulation (103)
(4) BIM-based building indoor wind environment simulation (104)
(5) BIM-based building fire easy ignition point determination strategy (105)
The building model construction and optimization (101) comprises the following steps: the three-dimensional digitization of the building becomes a research hotspot due to the proposal of the digital city, the three-dimensional digitization is three-dimensional modeling, in other words, the building is expanded from a plane graph to a three-dimensional graph, so that people can experience a vivid scene, and the first task of the three-dimensional digitization of the building is to seek a high-precision and high-efficiency modeling method. The BIM building information technology can achieve complete description of engineering projects which cannot be achieved by two-dimensional modeling software through three-dimensional digital modeling, and displays geometric information, physical information and topological information to owners. The building modeling method uses the concept of freely designing the building without being bound by software under the BIM technology to model the building, mainly comprises a structural system, a water supply and drainage system, a ventilation system and the like of the building, and the building of the BIM model is not single model building and needs a plurality of specialties to be coordinated and matched with one another according to a certain sequence to complete the building modeling. Before the three-dimensional model is built, basic information on a drawing of a building needs to be familiar, the integrity and the correctness of the drawing are determined, the drawing is used as the basis, and the whole building model is built on the basis of the drawing. The project template is the basis of project modeling and generally comprises an attempt template, a loaded family library, a well-defined unit geometric figure, a figure filling style, a line style and the like, and the family library carried by the three-dimensional modeling technology can greatly improve the modeling efficiency. And 3D models are established by using a three-dimensional modeling technology, and the modeling is completed by modifying parameters of corresponding components, so that the building model is constructed and optimized.
The building peripheral light environment simulation (102) based on BIM is as follows: at present, the lighting mode of buildings mainly takes side lighting and top lighting, while the determination of the easy ignition point of a building fire mainly depends on the influence of solar radiation, and the standards mainly depend on the design standard of building lighting (GB 50033-. The invention uses three-dimensional modeling technology to obtain a layer of model of the building, changes the parameters of the model and combines with CFD technology, and because the sustainable building design and the precision of an analysis tool are lower, the model needs to be simultaneously analyzed by combining with the building light environment simulation technology. The building luminous environment analysis defines its corresponding standard sky model using different mathematical algorithms with the international commission on illumination (CIE) and calculates the lighting coefficient using the sharing method (Split Flux) approved by the current british building research center (BRE), and the building thermal environment analysis is mainly in accordance with the admission method approved by the british society of registration engineers (CIBSE). Solar energy is continuously transmitted to the earth in the form of electromagnetic wave radiation, and the total radiation energy reaching the earth is 1.3 multiplied by 1021kcal/a, the outer surface of the outer wall of a building on the earth is provided with a roof and vertical wall surfaces in different directions, the total solar radiation obtained by the method is composed of direct radiation and scattered (sky scattering and ground reflection) radiation, and according to a calculation model of Hay and Klein, the equation is as follows:
Ht＝HbRb+HdRd+Hdg，
Hdg＝ρ[(Hb+Hd)Fg].
in the formula, HtThe wall surface is the daily average total solar radiation energy; hbThe direct solar radiation energy received by the sun on the horizontal plane; hdAtmospheric scattered radiant energy received on the horizontal plane on a daily basis; hdgThe surface reflected radiant energy received by the sun is the average day; rb、RdIs a correction factor; ρ is the ground reflectivity (0.2), which is related to the ground conditions.
The total solar irradiance in spring and summer is the sum of direct irradiance, sky scattered irradiance, ground reflected irradiance and atmospheric long-wave irradiance, the actual weather conditions in autumn and winter are not much the same as those in spring and summer, the indoor and outdoor temperature difference in autumn and winter is large, and only the direct solar irradiance which can directly influence the room temperature is generated. Therefore, the calculation formula of the time-by-time solar irradiance in autumn and winter of the building is as follows:
in the formula IOIs the solar constant, P is the atmospheric transparency coefficient, m is the atmospheric optical quality,
is the solar altitude, α is the solar azimuth, and i is the solar incident angle.
The four season average daily radiation extrema obtained from the analysis are shown in the following table:
according to the analysis, the four-season solar radiation simulation diagram of the building is obtained after the light environment of the building is analyzed, and therefore the BIM-based simulation of the ambient light environment outside the building is achieved.
The building peripheral wind environment simulation (103) based on BIM is as follows: the research on the fire points of buildings, which are easy to cause fire, has an important part, namely the research on indoor and outdoor wind environments, besides the light environment, namely the simulation on solar radiation. The invention applies a layer of model of the three-dimensional model obtained by the three-dimensional modeling technology, and carries out the simulation research of the outdoor wind environment by carrying out information interaction and applying a sustainable building design and analysis tool. The research on outdoor wind environment considers the requirements of various aspects aiming at different wind direction flows, the speed, the stability and the precision are calculated through various discrete formats and numerical value formats, and an optimal combination scheme is obtained through multiple times of simulation analysis and comparison, so that the research on determining the fire points of the building, which are easy to cause fire, is achieved. The invention relates to a weather tool, which mainly comprises two weather data sources, wherein one weather data source is data provided by an official platform Square one, the data provided by the platform is mostly foreign cities, and the national data is relatively less, so the weather data source is not adopted in the invention, and the other weather data source is data provided by a special weather data set for Chinese building thermal environment analysis, which is developed by Qinghua university and Chinese weather bureau in a combined manner, the platform contains the weather data of all cities in China, and has higher accuracy and authority, the invention carries out simulation analysis by using local actual conditions and weather conditions in outdoor wind environment simulation to obtain the average wind speed, temperature and wind direction of a certain city in four seasons as shown in the following table:
| spring season | (Summer) | Autumn | Winter season | |
| Average maximum temperature (. degree. C.) | 19.7 | 30.7 | 21.8 | 8.6 |
| Average maximum wind speed (m/s) | 4.4 | 6 | 4.7 | 5 |
| Wind direction | Southeast China | Southeast China | Northwest of China | Northwest of China |
The invention adopts a standard k-epsilon model and other turbulence model equations to solve the surrounding environment because the outdoor wind environment of the building is simulated and the flow around the building is usually turbulent, the related control equations mainly comprise a continuity equation, a momentum equation and an energy equation, and the general equation for simulating the outdoor wind environment of the building is as follows:
phi in the formula can be velocity, turbulence kinetic energy, turbulence dissipation rate and temperature. The specific expression form of the calculation equation for different working condition simulation analysis is shown in the following table:
the usual parameters in the table are as follows:
Gk＝μtS2，
Cμ＝0.0845，C1ε＝1.42，＝1.68，
σT＝0.85，σC＝0.7， αk＝αεby
Is calculated in which01.0. If μ < μeff，
Then
Where eta is SK/epsilon, eta0＝4.38，β＝0.012。
According to the analysis, the outdoor four-season wind flow field diagram of the building is obtained, the wind speed of the external environment is analyzed through the research on the flow field diagram of the outdoor wind environment simulation, and the ignition point which is easy to cause the building fire is researched and determined, so that the building external wind environment simulation based on BIM is realized.
The BIM-based building indoor wind environment simulation (104) comprises the following steps: the method is characterized in that a model obtained by using a three-dimensional modeling technology is subjected to derivation of a required format and mutual information utilization, and combined with a CFD technology, an indoor ventilation effect cloud picture and a vector map are simulated through software to reflect the indoor flow field condition according to the requirement of a green building evaluation standard (GB/T50378-2014) on indoor ventilation evaluation by referring to a simulation method related to numerical analysis in the building ventilation effect test and evaluation standard (JGJ/T309-2013), so that the easy ignition point of a building is determined. The method is characterized in that an RNG k-epsilon turbulence model is selected for flow field calculation according to standards in building indoor wind environment simulation, and the model is suitable for fast-strain complex shear flow, medium swirl flow, local transition flow such as boundary layer separation, bluff body wake vortex, large-angle stall, room ventilation and outdoor air flow. For the evaluation standard of indoor natural ventilation, the method is determined according to the area ratio RR, and when RR is more than or equal to 60% and less than 70%, 7 points are obtained; when RR is more than or equal to 70% and less than 75%, 8 points are obtained; when RR is more than or equal to 75% and less than 80%, 9 points are obtained; when RR is more than or equal to 80% and less than 85%, 10 points are obtained; when RR is more than or equal to 85% and less than 90%, 11 points are obtained; when RR is more than or equal to 90% and less than 95%, 12 points are obtained; when RR was 95% or more, 13 points were obtained.
In the combustion process of the fire source, the heat release rate of the fire source is unstable, and the invention adopts t with wide application2The fire model, the formula is as follows:
Q＝αt2
wherein Q is the heat release rate in kW; alpha is the fire growth coefficient and has the unit of kW/s2(ii) a t is the time of fire development in units of s.
The optimal mesh size is determined by the characteristic diameter of the fire source, which is given by the equation:
where rho∞Is the air density in kg/m3；cpThe specific heat capacity of air is expressed in kJ/(kg. K); t is∞Is the indoor temperature during ignition, and the unit is K; g is the acceleration of gravity in m/s2。
According to the analysis, the four-season average wind speed, temperature and wind direction values in a certain city in the weather tool in the step (3) are combined for simulation to obtain an indoor wind environment simulation diagram of the four-season building, so that the building indoor wind environment simulation based on the BIM is realized.
The BIM-based building fire easy ignition point determination strategy (105) comprises the following steps: in the research process of determining a fire point which is easy to cause fire for a building, factors such as the outdoor light environment of the building, the outdoor wind environment of the building, the indoor wind environment of the building, the materials of the building, the layout of the building and the like are important contents to be considered.
In the building peripheral light environment simulation research based on BIM in the step (2), solar radiation is used as an energy source of geographic environment and ecological environment, and is particularly critical in building indoor light environment simulation. For the thermal environment of buildings, the interference of solar radiation is large, especially the radiation quantity directly entering the room through the glass window has special influence on the room temperature condition, and the influence on the easy ignition point of the building caused by research is large. In the building peripheral wind environment simulation based on the BIM in the step (3), along with the continuous increase of urban high-rise buildings and the continuous increase of building density, the wind environment becomes an important factor influencing the living quality of people, and the outdoor wind environment is related to the comfort problem of people living and even the safety problem. In the building indoor wind environment simulation based on the BIM in the step (4), the ventilation between the building and the building or the building group is complicated due to the combined action of wind pressure and hot pressing. In addition, improper building layout, fire prevention interval do not accord with fire control safety requirement, do not consider wind direction, topography etc. factor can cause the condition that the conflagration spreads to form large tracts of land conflagration, lead to the possibility that indoor conflagration takes place to increase constantly. In addition, in the research on the influence of building materials on building fires, the influence of building materials mainly has four aspects, namely, the influence on the ignition and flashover speed, the continuous spread of flame, the heat temperature promoting the fire and the generation of dense smoke and toxic gas. The building materials are different, the selected design basis is different, the mechanical properties of the building materials are different, the selected calculation formula and software are different during analysis, and the factors can be the influence of the building materials on the building fire, so that the building materials are an indispensable part when the building fire-prone point is researched.
The invention develops a building fire easy ignition point determining method based on BIM around factors influencing fire occurrence, starts from factors such as solar radiation, indoor and outdoor wind environments, materials of the building and the like, and innovatively provides a method for searching the position of an ignition point of the building when the fire easily occurs from external factors, so that the disaster can be effectively reduced, and scientific theoretical basis and technical support are provided for preventing the fire of the building.
Claims (10)
1. A BIM-based method for determining a building fire easy ignition point is characterized by comprising the following steps:
(1) building model construction and optimization;
(2) building exterior ambient light environment simulation based on BIM;
(3) building periphery wind environment simulation based on BIM;
(4) building indoor wind environment simulation based on BIM;
(5) BIM-based building fire susceptibility determination strategies.
2. The BIM-based building fire prone spot determination method according to claim 1, wherein the building model is constructed and optimized in the step (1): building information model BIM components are carried out by using a three-dimensional modeling technology, a building plane graph drawn by using a two-dimensional modeling technology is subjected to 3D model establishment by using the three-dimensional modeling technology, and building model construction and optimization are realized by drawing buildings and structural engineering of the building and setting various parameters.
3. The BIM-based building fire incident point determination method as claimed in claim 2, wherein the building construction and structural construction includes a structural system, a water supply and drainage system and a ventilation system.
4. The BIM-based building fire prone spot determination method according to claim 1, wherein the step (2) is based on BIM-based building ambient light environment simulation: the method comprises the steps of utilizing a sustainable building design and analysis tool under the BIM technology, mutually utilizing format information required by the derivation of a building model obtained by utilizing the three-dimensional modeling technology, utilizing the sustainable building design and analysis tool to the model, combining meteorological data of all places in the meteorological tool, carrying out simulation analysis according to local actual conditions and climatic conditions, and deriving a peripheral flow field analysis diagram received by the building under different environments in four seasons by combining building materials, thereby realizing building peripheral wind environment simulation based on the BIM.
5. The BIM-based building fire prone spot determination method according to claim 4, wherein the step (2) is based on BIM-based building ambient light environment simulation: at present, the lighting mode of a building mainly takes side lighting and top lighting, while the easy ignition point of a fire disaster of the building is determined by the influence of solar radiation according to the standard of building lighting design standard and green building evaluation standard; building light environment analysis defines a corresponding standard sky model by a mathematical algorithm of the international commission on illumination, and calculates a lighting coefficient by using a sharing method approved by the british building research center, wherein the building thermal environment analysis is according to an admission method approved by the british registration engineer association; solar energy is continuously transmitted to the earth in the form of electromagnetic wave radiation, and the total radiation energy reaching the earth is 1.3 multiplied by 1021kcal/a, the outer surface of the outer wall of a building on the earth is provided with a roof and vertical wall surfaces in different directions, the total solar radiation obtained by the method is composed of direct radiation and scattered radiation, and the equation is as follows according to a calculation model of Hay and Klein:
Ht＝HbRb+HdRd+Hdg，
Hdg＝ρ[(Hb+Hd)Fg].
in the formula, HtThe wall surface is the daily average total solar radiation energy; hbThe direct solar radiation energy received by the sun on the horizontal plane; hdAtmospheric scattered radiant energy received on the horizontal plane on a daily basis; hdgThe surface reflected radiant energy received by the sun is the average day; rb、RdIs a correction factor; rho is the ground reflectivity, is marked as 0.2 and is related to the ground condition;
the total solar irradiance in spring and summer is the sum of direct irradiation, sky scattering irradiation, ground reflection irradiation and atmosphere long-wave irradiation illuminance, and the indoor and outdoor temperature difference in autumn and winter is large, only the direct solar irradiation illuminance can directly influence the room temperature, so the calculation formula of the time-by-time solar irradiation illuminance in autumn and winter of the building is as follows:
in the formula IOIs the solar constant, P is the atmospheric transparency coefficient, m is the atmospheric optical quality,
is the solar altitude, alpha is the solar azimuth, i is the solar incident angle;
according to the analysis, the four-season solar radiation simulation diagram of the building is obtained after the light environment of the building is analyzed, and therefore the BIM-based simulation of the ambient light environment outside the building is achieved.
6. The BIM-based building fire prone spot determination method according to claim 1, wherein the BIM-based building exterior wind environment simulation in the step (3): the method comprises the steps of applying a sustainable building design and analysis tool under the BIM technology, conducting information interoperability on a format required by model derivation obtained by applying the three-dimensional modeling technology, applying the model to the sustainable building design and analysis tool, combining meteorological data of all places in the meteorological tool, conducting simulation analysis according to local actual conditions and climatic conditions, combining building materials, deriving a peripheral flow field analysis diagram received by the building under different environments at all seasons, and accordingly achieving building peripheral wind environment simulation based on the BIM.
7. The BIM-based building fire vulnerability determination method according to claim 6, wherein said (3) BIM-based building peripheral wind environment simulation (103): the research on outdoor wind environment considers the requirements of various aspects aiming at different wind direction flows, the speed, the stability and the precision are calculated through various discrete formats and numerical value formats, and an optimal combination scheme is obtained through multiple times of simulation analysis and comparison, so that the research on determining the fire points of the building, which are easy to cause fire, is achieved; the meteorological data source adopted in the meteorological tool is data provided by a meteorological data set special for Chinese building thermal environment analysis, which is developed by Qinghua university and China meteorological office in a combined manner, and the meteorological data source is used for carrying out simulation analysis according to local actual conditions and climatic conditions in outdoor wind environment simulation to obtain the local four-season average wind speed, temperature and wind direction of the building;
because the outdoor wind environment of the building is simulated, the flow simulation of the periphery of the building is turbulent flow, the standard k-epsilon model and other turbulent flow model equations are adopted to solve the periphery environment, the involved control equations comprise a continuity equation, a momentum equation and an energy equation, and the general equation for the outdoor wind environment simulation of the building is as follows:
phi in the formula is velocity, turbulent kinetic energy or turbulent dissipation rate and temperature; the specific expression form of the calculation equation for different working condition simulation analysis is shown in the following table:
the usual parameters in the table are as follows:
Gk＝μt52，
Cμ＝0.0845,C1ε＝1.42,＝1.68,
σT＝0.85，σC＝0.7，αk＝αεby
Is calculated in which01.0. If μ<<μeff，
Then alpha isk＝αε≈1.393，
Where eta is SK/epsilon, eta0＝4.38，β＝0.012。
According to the outdoor four-season wind flow field diagram of the building obtained through the analysis, the wind speed of the external environment is analyzed through the research on the flow field diagram of the outdoor wind environment simulation, and the ignition point which is easy to cause the building fire is researched and determined, so that the building peripheral wind environment simulation based on the BIM is realized.
8. The BIM-based building fire prone spot determination method according to claim 1, wherein the BIM-based building indoor wind environment simulation in the step (4): the method comprises the steps of leading out a required format of a model obtained by applying three-dimensional modeling, mutually using information, applying computational fluid dynamics technology, simulating indoor wind environment of a building through wind speed and temperature data of the building in a meteorological tool in local four seasons, obtaining wind speed and pressure change inside the building through analysis, and realizing BIM-based simulation of the indoor wind environment of the building through data comparison.
9. The BIM-based building fire vulnerability determination method according to claim 8, wherein said (4) BIM-based building indoor wind environment simulation: in the building indoor wind environment simulation, an RNG k-epsilon turbulence model is selected according to the standard to calculate the flow field, wherein the related formula and equation are the same as the step (3); for the evaluation standard of indoor natural ventilation, the method is determined according to the area ratio RR, and when RR is more than or equal to 60% and less than 70%, 7 points are obtained; when RR is more than or equal to 70% and less than 75%, 8 points are obtained; when RR is more than or equal to 75% and less than 80%, 9 points are obtained; when RR is more than or equal to 80% and less than 85%, 10 points are obtained; when RR is more than or equal to 85% and less than 90%, 11 points are obtained; when RR is more than or equal to 90% and less than 95%, 12 points are obtained; when RR is more than or equal to 95%, 13 points are obtained;
in the combustion process of the fire source, the heat release rate of the fire source is unstable, and the invention adopts t with wide application2The fire model, the formula is as follows:
Q＝αt2
wherein Q is the heat release rate in kW; alpha is the fire growth coefficient and has the unit of kW/s2(ii) a t is the time of fire development in units of s;
the optimal mesh size is determined by the characteristic diameter of the fire source, which is given by the equation:
where rho∞Is the air density in kg/m3；cpThe specific heat capacity of air is expressed in kJ/(kg. K); t is∞Is the indoor temperature in the case of fire, and has the unit of K; g is the acceleration of gravity in m/s2；
According to the analysis, the local four-season average wind speed, temperature and wind direction values of the building in the weather tool in the step (3) are combined for simulation to obtain an indoor wind environment simulation diagram of the four-season building, so that the building indoor wind environment simulation based on the BIM is realized.
10. The BIM based building fire prone spot determination method according to claim 1, wherein the BIM based building fire prone spot determination strategy in step (5): the building peripheral light environment simulation based on the BIM, the building peripheral wind environment simulation based on the BIM and the building indoor wind environment simulation based on the BIM are combined, and then the structure of the building, the characteristics of the building and the material of the building are combined, so that the ignition point of the building where the fire easily occurs is judged, and the building fire easy ignition point determining strategy based on the BIM is realized.
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