Wood structure building group fire spreading risk assessment and prevention and control strategy making method

Abstract

The invention relates to the technical field of building group fire prevention and control, in particular to a wood structure building group fire spreading risk assessment and prevention and control strategy making method, which comprises the following steps: obtaining a potential fire risk index expectation of a building group through building group fire spreading risk analysis; building group fire-extinguishing rescue capability index expectation is obtained through building group fire-extinguishing rescue conditions; building a building group fire safety feature grading and classifying lattice diagram, and performing risk grade evaluation and division; and making a building group fire spreading prevention and control strategy of the fire safety features based on the building group fire safety feature classification lattice diagram. Diversified building groups are adapted by adopting a mode of unmanned aerial vehicle surveying and mapping and field investigation, risk levels of different building groups are quantitatively distinguished by establishing a two-dimensional model of a potential fire spreading index and a fire extinguishing and rescuing capability index, fire safety problems of the different building groups are diagnosed according to positions of the different building groups in a lattice diagram, and the safety of the different building groups is improved. And a suitable and low-intervention fire spreading prevention and control strategy or a transformation direction is given.

Description

Technical Field

[0001] This invention relates to the field of fire prevention and control technology for building complexes, specifically to a method for assessing the risk of fire spread in timber-framed building complexes and formulating prevention and control strategies. Background Technology

[0002] Currently, according to the management requirements of emergency management departments, historical and cultural protection strategies, and the needs of modern protection technologies, the fire protection renovation of traditional villages and towns should be done in a way that preserves the original appearance and avoids large-scale renovations. Domestic research institutions and fire departments have conducted extensive research and successfully formulated a series of local standards for fire prevention and control in traditional village and town buildings, and have accumulated rich management experience. Existing research mainly focuses on two levels: individual buildings and building complexes. At the level of individual buildings, fire detection, flame retardant technology, fire extinguishing technology, personnel evacuation technology, fire Internet of Things and GIS are introduced to improve fire extinguishing and rescue capabilities and fire safety management levels, thereby reducing the fire risk of individual buildings. At the level of building complexes, based on the renovation of each individual building, measures such as setting up fire isolation belts and dividing fire zones are used to control the spread of fire. In addition, fire management departments at all levels have also summarized fire prevention technical measures and management experience through fire accident investigation, fire test and fire spread theory research. However, whether at the level of individual buildings or building complexes, there are two key problems when applied to traditional wooden building complexes such as ancient towns and villages: (1) The scope of renovation is large and affects the traditional style. (1) Fire protection renovation of individual buildings is carried out one by one. Excessive intervention not only destroys the traditional appearance of the building complex, but may also lead to inefficient or ineffective protection measures, and increases renovation investment and later maintenance costs; (2) The differences in fire spread risk and fire safety characteristics of different wooden building complexes are not taken into account, and the problems of insufficient protection and excessive protection coexist.

[0003] The aforementioned traditional timber-framed building complexes are existing structures built in the absence of unified fire safety technical standards. Different building complexes within the same region exhibit significant differences in fire spread risk and fire safety characteristics. Traditional village and town building complexes with different architectural styles exhibit substantial differences in potential fire spread risk due to variations in building form, fire resistance rating, facade opening ratio, and fire separation distances. Furthermore, the fire-fighting and rescue capabilities of different traditional villages and towns vary considerably due to differences in fire alarm systems, fire extinguishing systems, village and town fire water supply, fire rescue response capabilities, as well as their natural conditions and infrastructure. Therefore, when formulating fire prevention and control strategies for traditional village and town building complexes, it is essential to adopt fire safety renovation strategies adapted to the specific fire safety characteristics of each complex to achieve effective and low-intervention-response prevention and control.

[0004] The differences in potential fire spread risk and fire fighting and rescue capabilities among traditional village and town building complexes lead to varying fire safety characteristics, requiring different fire safety renovation strategies. Renovation directions may focus on controlling potential fire spread risk, improving fire fighting and rescue capabilities, or both. The specific content and extent of renovations will also differ, making it difficult to establish unified prevention and control technical standards. This is a major reason why inadequate and over-protection coexist in engineering practice. Therefore, when renovating or formulating fire prevention and control strategies for traditional villages and towns, it is necessary to establish a fire safety characteristic classification model for different village and town building complexes from the perspective of potential fire spread losses and fire fighting and rescue capabilities, providing a classification matrix diagram to categorize the fire safety characteristics of different villages and towns. By analyzing the location of different traditional villages and towns in the matrix diagram, problems in the fire safety of building complexes can be diagnosed. Based on this, corresponding prevention and control strategies can be proposed according to the actual situation of traditional villages and towns. Numerous fire cases show that fire spread between buildings is the main cause of large-scale fire losses in contiguous wooden building complexes, making fire spread prevention and control in traditional villages and towns an urgent and important issue that needs to be addressed. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for assessing the risk of fire spread in timber-framed building complexes and formulating prevention and control strategies.

[0006] To achieve the above technical solution, the steps include: S1. Obtain fire spread risk factors for the target building complex, including: Using drone oblique photography technology, macroscopic information of each individual building in the complex is obtained, including: the location, geometric dimensions, scale, terrain features, and fire access roads of the target village. On-site surveys were used to obtain micro-level information about each individual building in the complex, including: building attributes, business type attributes, structural measures, fire water sources, fire protection facilities, and fire hazard sources.

[0007] S2. Based on the elements obtained in S1, the expected potential fire risk index of the building complex is obtained and the potential fire spread risk of the building complex is classified. S2.1 Construct a calculation expression for the potential spread risk index of a fire spread scenario; The potential fire spread risk index of building complexes in fire spread scenarios Defined as: fire spread scenario The ratio of fire spread loss to the allowable fire spread loss of traditional village and town building complexes is expressed as: In the formula, Scene of fire spreading The potential fire spread risk index; To mitigate the permissible fire spread damage to traditional village and town building complexes, according to the "Rural Fire Prevention Code" and the "Technical Guidelines for Fire Prevention and Control in Ancient Towns and Villages," the area of ​​densely built-up areas with high fire resistance ratings should not exceed 5000 m². 2 For densely built-up areas with low fire resistance ratings, the floor area should not exceed 3000m². 2 When the area exceeds the specified requirements, a fire-resistant isolation zone must be installed for separation. Therefore, the fire-resistant zone can be optionally eliminated, as it occupies an area of ​​3000m². 2 5000m 2 As the allowable value for fire spread loss in densely built areas with low and high fire resistance ratings; Scene of fire spreading Potential fire spread and losses; Fire spread scene Potential fire spread losses The maximum value is obtained as follows: S2.1.1 Analyze the fire spread process of the building complex, including three stages: the development of fire inside the building, the spread of fire in different rooms within the building, and the spread of fire between buildings; S2.1.2 Based on the fire spread process of the building complex, construct a directed graph of fire spread in the building complex; Treating individual buildings as nodes in a directed graph, and based on the fire spread analysis process described above, the spread relationships and spread times between adjacent buildings are determined, and an adjacency matrix is ​​established. The data stores the connection relationships between network nodes, corresponding to the direct ignition relationships (edges) between different nodes in the building complex. Let the adjoining vector of the directed graph be denoted as When there are nodes in a directed graph Pointing to neighbor nodes When the edge is, then ( For nodes Ignite neighboring nodes (Time), to obtain the adjacency matrix considering time weights. ; Based on the adjacency matrix considering time weights The fire spread matrix is ​​calculated using a directed graph path search algorithm. Used to describe the direct or indirect connections between network nodes, the fire spread vector is denoted as... When node with neighboring nodes If there are directly or indirectly connected edges, then , representing a node In the shortest time Ignite neighboring nodes ; Fire spread matrix and shortest time The solution method is as follows: From nodes in a directed graph network Start from the directed edge and reach the neighbor node The path with the minimum sum of edge weights is the building. i Spread to buildings j To find the shortest path in time, various shortest path algorithms have been developed, among which the more common ones include Dijksra's algorithm, A* algorithm, Bellman-Ford algorithm, and Floyd-Warshall algorithm. Dijksra's algorithm is a typical single-source shortest path method, used to calculate the shortest path from one node to all other nodes. Its main characteristic is that it expands outwards layer by layer from the starting point until it reaches the destination. This algorithm uses a breadth-first search algorithm to determine the nodes. and neighboring nodes The shortest path between nodes, when considering the weights of directed edges, reflects the relationship between nodes. The fire spread from its origin to neighboring nodes. The time required; without considering the weights of directed edges, this shortest path reflects the nodes The fire spread from its origin to neighboring nodes. The required number of intermediate nodes, and the algorithm steps are as follows: ① Let set S store the visited nodes, where S∈V, and V represents the set of all nodes (i.e., all individual buildings) in the building cluster network; define For nodes Ignite neighboring nodes Time, if and If there are connected edges, then Equal to the weight of its edge ( =0), if and If there are no connected edges, then = inf; sets one M×M Auxiliary matrix T ,make =0, and the initial value of the remaining elements is inf; ②Let set From the set VS Selecting nodes The node with the smallest edge weight connected to its adjacent nodes If it exists, then Add to collection S Update auxiliary matrix T If the first step is not found, the algorithm proceeds to the next step; otherwise, the algorithm terminates and outputs set S. Update auxiliary matrixT The expression is as follows: In the formula, Represents a node The node with the smallest edge weight connected to its adjacent nodes The minimum direct ignition time; Represents a node The node with the smallest edge weight connected to its adjacent nodes The direct ignition time; ③ Find the node with the smallest edge weight connecting its adjacent nodes. As the intermediary point, continue from the set VS Select with node The neighboring node with the smallest edge weight connected to its adjacent node. If it exists, then Add to collection S In the middle, update the auxiliary matrix T If the first step is not found, the algorithm proceeds to the next step; otherwise, the algorithm terminates and outputs a set. S ; Update the auxiliary matrix using neighbor nodes. T The expression is as follows: In the formula, This represents the node with the smallest edge weight connecting adjacent nodes. to neighboring nodes The direct ignition time; ④ Repeat step ③ until all nodes have been traversed, i.e., the set is complete. VS =Φ, the algorithm ends, output set S and auxiliary matrix. T The resulting auxiliary matrix T This is the fire spread matrix that takes time weight into account. ; matrix The column number and value corresponding to the non-inf elements represent the node. After the fire starts, the node number that is directly or indirectly ignited and its shortest time; S2.1.3 Calculate fire spread losses based on the directed graph of fire spread in the building complex; The loss in a fire spread scenario is defined as the number or area of ​​buildings ignited by the burning building, which can be expressed as the sum of the areas or numbers of each ignited building; it can be calculated using a fire spread matrix for a building complex. The matrix is ​​set up... For the spread matrix that does not consider time weights, the matrix's _____ Row elements are calculated as follows: Spread matrix without considering time weights The first in The column number corresponding to the element with a value of 1 in a row indicates the node. After the fire starts, the node numbers that can be ignited and the maximum fire spread losses caused by the fire. The expression is as follows: In the formula, Fire spread matrix The OK; S =[s1...s a ...s M ] T Let s be a vector composed of the areas of the individual buildings in the complex, where s a Let be the area of ​​building a. If the area weights of individual buildings are not considered... S =[1,1,…,1] T It is a column vector with M rows and each element having a value of 1; S2.2 Based on the calculation expression of the potential fire spread risk index in multiple fire spread scenarios, construct the expected value of the potential fire spread risk index of building clusters in multiple fire spread scenarios; The construction method involves treating each building in the complex as the ignition point and calculating the fire spread scenarios. The potential fire risk index, taking into account the probability of different fire spread scenarios; The expression for the expected value of the potential fire spread risk index for building complexes with multiple fire spread scenarios is as follows: In the formula, Describing the spread of a fire The probability of occurrence, and the spread scenario in the event of a fire. The probability is directly proportional to the building area, expressed as: In the formula, Indicates the first The area of ​​each building; This indicates the number of buildings in the complex, where... An index representing the number of buildings; if the influence of the area weight of each individual building is not considered, then the probability of fire in each individual building is the same, 1 / M ; S2.3. Based on the expected value of the potential fire spread risk index of the building complex under the constructed multiple fire spread scenarios, the potential fire spread risk of the building complex is divided by the preset boundary value. Potential fire risk index of building complex I LThe larger the value, the greater the damage caused by the spread of fire within the building complex. I L When the value is greater than 1, the potential fire spread risk index of the building complex exceeds the permissible loss, indicating a high risk of fire spread. To differentiate the fire spread risk levels of different building complexes, a potential fire spread risk index for the building complex is selected. I L A value of 0.5 is used as the dividing line between low and medium fire spread risk. I L A value of 1 is used as the dividing line between medium and high fire spread risk. (Building complex fire spread risk level) L FR It can be divided according to the following formula: .

[0008] S3. Calculate the fire fighting and rescue capability of the building complex and obtain the expected fire fighting and rescue capability index. Fire spread scene x Firefighting and rescue capability index It can be calculated using the following formula: In the formula, Time taken for firefighters to intervene (min); Scenes of fire spread when firefighters intervene. x Firefighting water consumption (L / s); Firefighting water supply for village and town building complexes (L / s); Obviously, the time it takes for firefighters to intervene. The smaller the fire, the smaller the fire spread and the lower the water demand for firefighting. The lower, The smaller the building complex, the stronger its fire fighting and rescue capabilities; the town's water supply capacity... The larger, The smaller the building complex, the stronger its fire fighting and rescue capabilities. This is based on obtaining all fire spread scenarios. x After determining the fire fighting and rescue capability index, considering the probability of different fire spread scenarios, the expected fire fighting and rescue capability index of building complexes under multiple fire spread scenarios can be obtained. : Firefighting capability index of building complex It is a function of the time it takes for firefighters to intervene. The larger the value, the higher the demand for firefighting water during fire rescue, assuming the firefighting force intervention time. When known, it can be simply written as ; Firefighter intervention time Scenes of fire spread when firefighters intervene. xFirefighting water volume Fire water supply for village and town building complexes The calculation method is as follows: Determine the time for fire and rescue intervention. The time it takes for firefighters to intervene after a fire breaks out often determines the size of the fire and thus affects the water demand for firefighting. Therefore, the intervention time of firefighters must be considered when calculating firefighting water demand. The fire department's intervention time is the time from the start of the fire to the deployment of equipment and commencement of firefighting efforts. It consists of the time taken for a series of consecutive events and is calculated as follows: In the formula, This refers to the alarm time; For scheduling time; For preparation time; This refers to the travel time. Time to deploy firefighting equipment; Determining the reliability of fire-fighting water supply: The fire-fighting and rescue capability index of a building complex is the ratio of the water required to control a fire when fire-fighting forces intervene to the traditional fire-fighting water supply capacity of villages and towns. Without considering the impact of residents' daily water use, the fire-fighting water supply capacity of the building complex remains constant; however, the fire-fighting water demand is affected by the scale of the fire in the building complex when fire-fighting forces intervene. Its calculation needs to be determined by combining the changing pattern of the fire scale over time and the probability distribution of the fire-fighting intervention time. The specific steps are as follows: (1) The fire development process of a single building and the fire spread relationship between buildings are analyzed using S2.1.1 to determine the fire spread adjacency matrix that takes time weight into account. (2) The S2.1.2 path search algorithm is used to calculate the spread matrix considering time weights. To determine the building ignition time sequence under specific fire spread scenarios; (3) Based on the ignition time of different buildings under a specific fire spread scenario, the fire heat release rate curves of individual buildings in different combustion states are superimposed to obtain the specific fire scenario. x The fire heat release rate is determined to identify the fire water demand in different fire scenarios. ; (4) Determine the fire water supply capacity by combining the water supply network hydraulic model or on-site fire hydrant water discharge test, so as to determine the fire water supply and demand relationship; (5) Taking into account the time of fire rescue intervention, the fire-fighting water demand during fire rescue is determined as the basis for fire water supply design; Firefighting water requirements are determined using the formula given by the NZFESG method. The calculation method is as follows: In the formula, Scene of fire spreading At the moment of fire intervention The rate of heat release from the fire, depending on the specific fire spread scenario. The ignition time of different buildings was used to superimpose the fire heat release rate curves of individual buildings under different combustion states. The fire extinguishing efficiency of water, that is, the efficiency of water in absorbing fire energy, is generally between 0.1 and 0.3. In this invention, it is taken as 0.2. The water absorption extinguishing capacity rate is taken as 2.26 MW / L / s; Fire water supply for village and town building complexes The fire water supply capacity is determined by combining on-site fire hydrant water discharge tests and simulation methods to calculate the fire water supply volume, thereby establishing the relationship between fire water supply and demand. The steps include: Calculation of fire water supply using the on-site fire hydrant water discharge test method: Based on the test results of the on-site fire hydrant water discharge test, the fire water supply capacity assessment values ​​recommended by NFPA 291 are adopted. It can be calculated using the following formula: In the formula, The total flow rate of water discharged from the fire hydrants (L / s) was measured during the test. The pressure loss when the pressure drops to the desired residual pressure, i.e., the fire flow rate is... Pipeline head loss (m); The pressure loss measured during the test, i.e., the fire flow rate, is equal to... Pipeline head loss (m); where, and The expression is as follows: In the formula, The measured pressure value (mH2O) is when the water flow rate of the fire hydrant is zero. The minimum allowable pressure (mH2O) at the reference point is taken as 10m according to the specification. The test value (mH2O) is for fire hydrants. Simulation method for calculating fire water supply: Based on the calculation of fire water supply using on-site fire hydrant water discharge tests, an iterative algorithm is used. Through a network sequential search process, an improved flow estimate is obtained in each iteration. This method is relatively easy to implement in existing network solution algorithms, and its expression is as follows: In the formula, This represents the normal water demand under static conditions. When the value is zero, the calculation expression for fire water supply using the on-site fire hydrant water discharge test method is consistent with the calculation expression for fire water supply using the simulation method. This means that the calculation expression for fire water supply using the on-site fire hydrant water discharge test method is a special case of the calculation expression for fire water supply using the simulation method. As shown in the above formula, when... constantly approaching At that time, = ; Update using the following steps : (1) Construct a hydraulic model of the pipe network, perform operational analysis, and record the node flow rates. Pressure measurement value when the water flow rate of the fire hydrant is zero ,when < At that time, It is zero; when = At that time, = ;when > At that time, then order = +△, where △ is an arbitrary increment; (2) Run the pipeline hydraulic model and calculate the nodal flow rates. = When +△, the corresponding nodal water pressure value; (3) Calculate the fire water supply volume using the simulation method. Output the analysis results; (4) Check convergence; if relative flow accuracy is... ε When less than the small tolerance (take 10) -4 If the condition is met, terminate the calculation; otherwise, replace the original value. , for , ,make = Repeat steps (2) to (4) until the relative flow accuracy is achieved. ε The requirements are met; during the convergence check, the relative flow accuracy is [not specified]. ε The expression is as follows: .

[0009] S4. Construct a hierarchical classification matrix of fire safety characteristics of building complexes and conduct risk level assessment and classification. The method for constructing a hierarchical classification dot matrix map of fire safety characteristics of building complexes is as follows: based on the fire fighting and rescue capability index. The horizontal axis represents the potential fire spread risk index of the building complex. The vertical axis represents the potential fire spread risk index of the building complex. Based on the expression and the table of water supply and demand for fire rescue, a two-dimensional dot matrix diagram of the fire safety characteristics of traditional village and town building complexes is established.

[0010] S5. Based on the hierarchical classification matrix of fire safety characteristics of building complexes, formulate fire spread prevention and control strategies for building complexes with fire safety characteristics; By using the fire safety characteristics classification matrix of building complexes and the location of different building complexes in the matrix, the fire safety problems of building complexes are diagnosed, and three situations are encountered: (1) the fire spread is too large; (2) the fire fighting and rescue capabilities are insufficient due to the fire fighting action starting too late or insufficient water supply; (3) both of the above situations occur at the same time. By analyzing the location of different building complexes in the dot matrix map and diagnosing fire safety issues, a fire safety characteristic-based dot matrix prevention and control strategy is formulated based on the two objectives of controlling the spread of fire damage and improving the fire fighting and rescue capabilities of different building complexes. This strategy is tailored to the fire safety characteristics of each building complex. When the fire is relatively large, by cutting off the spread path of important nodes, the passive fire resistance of the building or building complex as a whole is gradually improved, reducing the risk of fire spread in the building complex; when the fire fighting and rescue capability index is high... When the fire is large, the rescue capacity of the building complex may have three problems: (1) untimely fire fighting and rescue; (2) insufficient water supply; (3) the above two problems occur at the same time. Therefore, it is necessary to implement prevention and control measures from the perspectives of early intervention of fire rescue forces and improving the water supply capacity of village and town building complexes. Based on the different positions of different building complexes in the classification matrix, their corresponding prevention and control priorities or improvement strategies are formulated according to the following principles: ① For building complexes with both low potential fire risk index and low fire fighting and rescue capability index, the focus of prevention and control should be on controlling the fire risk of individual buildings and strengthening fire safety education to prevent small fires from causing fatalities; ② For building complexes with a potential fire risk index between [0.5, 1), the focus should be on controlling the fire spread risk of the building complex, identifying important buildings, and cutting off the spread path; ③ For building complexes with a potential fire risk index between [1, +∞), the focus should be on controlling the fire spread risk of the building complex, identifying important buildings, cutting off the spread path, improving the fire resistance of buildings, and strengthening fire source control and the early intervention capability of fire fighting forces. ④ For building complexes with a fire fighting and rescue capability index between [0.5, 1), it indicates that the existing fire fighting and rescue capability can basically meet the fire fighting and fire protection needs; ⑤ For building complexes with a fire fighting and rescue capability index between [1, +∞), the main focus should be on adding alarm systems and setting up different types of fire rescue to improve the ability to intervene in fire rescue early and enhance fire water supply capacity.

[0011] Based on the prevention and control strategies of the fire safety feature classification matrix and the fire safety features of the above cases, corresponding transformation directions are given, and the scheme design is completed.

[0012] Beneficial effects of the present invention This invention establishes a two-dimensional model of potential fire spread index and fire fighting and rescue capability index to quantitatively distinguish the risk levels of different building groups and avoid subjective judgment.

[0013] This invention combines directed graphs and shortest path algorithms to dynamically simulate the fire spread process, accurately predict the spread path, and identify key risk nodes.

[0014] This invention establishes a dot matrix map, distinguishes between high, medium, and low-risk areas, and implements differentiated prevention and control measures to balance protection and safety.

[0015] This invention solves the problem of insufficient water supply in traditional villages and towns by dynamically assessing water supply capacity through real-time calculation of fire-fighting water supply and matching of water demand. This invention employs drone mapping and on-site surveying, resulting in efficient data acquisition, reduced costs for large-scale renovations, and adaptability to diverse building complexes. Attached Figure Description

[0016] Figure 1 This is a flowchart of the steps of the present invention; Figure 2 This is a schematic diagram of Case 1 in the embodiments of the present invention; Figure 2 (a) Mapping of the UAV in Case 1, Figure 2 (b) is the architectural layout plan for Case 1. Figure 2 (c) is the fire protection pipe network diagram for Case 1; Figure 3 This is a schematic diagram of Case 2 in the embodiments of the present invention; Figure 3 (a) Mapping of the UAV in Case 2. Figure 3 (b) is the architectural layout plan for Case 2. Figure 3 (c) is the fire protection pipe network diagram for Case 2; Figure 4 This is a schematic diagram of the fire heat release rate curve of the present invention; Figure 4 (a) is a diagram showing the development of an indoor fire; Figure 4 (b) The fire spread process inside the building; Figure 4 (c) The fire spread and developed within the building complex; Figure 5 This is a schematic diagram of the fire plume propagation of the present invention; Figure 6 This is a schematic diagram simulating the fire spread process in a building complex according to the present invention; Figure 7 This is a flowchart illustrating the simulation of fire spread in a building complex according to the present invention. Figure 8 This is a fire scene spread diagram according to an embodiment of the present invention; Figure 8 (a) is a diagram showing the spread of all fire scenarios in Case 1. Figure 8 (b) A diagram showing the spread of all fire scenarios in Case 2; Figure 9 This invention relates to different fire spread scenarios and potential fire risk indices. Figure 9 (a) shows the losses and potential fire risk index for different fire spread scenarios in Case 1. Figure 9 (b) Losses and potential fire risk indices for different fire spread scenarios in Case 2; Figure 10 This is a schematic diagram of the fire brigade intervention model of the present invention; Figure 11 This invention provides a schematic diagram of the workflow for determining the reliability of fire-fighting water supply. Figure 12 This is a schematic diagram of fire intervention time according to an embodiment of the present invention; Figure 12 (a) is a timeline of fire department intervention in Case 1. Figure 12 (b) is a timeline of fire department intervention in Case 2; Figure 13 This is a schematic diagram illustrating the fire-fighting water demand of the present invention; Figure 13 (a) represents the fire water demand in Case 1. Figure 13 (b) Firefighting water demand in Case 2; Figure 14 This is a schematic diagram of the water supply network hydraulic model in Example 1 of the present invention; Figure 14 (a) is the official modeling diagram for Case 1. Figure 14 (b) is a diagram showing the node elevation and pipe segment length in Case 1; Figure 15 This is a schematic diagram of the hydraulic model of the water supply network in Example 2 of the present invention; Figure 15 (a) is the official website modeling diagram for Case 2. Figure 15 (b) is a diagram showing the node elevation and pipe segment length in Case 2; Figure 16 This is a schematic diagram of the fire fighting and rescue capability index for different fire spread scenarios in Examples 1 and 2 of the present invention. Figure 16 (a) represents the firefighting and rescue capability index for different fire spread scenarios in Case 1. Figure 16 (b) Firefighting and rescue capability index for different fire spread scenarios in Case 2; Figure 17 This is a dot matrix diagram for classifying fire safety features according to the present invention; Figure 18 This is a dot matrix diagram classifying fire safety features for different fire spread scenarios in embodiments of the present invention; Figure 18 (a) A dot matrix diagram classifying fire safety characteristics for different fire spread scenarios in Case 1; Figure 18 (b) A dot matrix diagram classifying fire safety characteristics for different fire spread scenarios in Case 2; Figure 19 This is a diagram illustrating the fire safety feature classification matrix control strategy of the present invention. Figure 20 This is a dot matrix diagram for classifying the fire safety features of building complexes according to the present invention. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to specific embodiments.

[0018] The three southwestern provinces of Yunnan Province possess a large number of historical and cultural cities (towns, villages, and streets) and traditional villages in urgent need of protection. These are mostly contiguous clusters of traditional wooden structures with diverse architectural styles, representing a treasure trove of traditional Chinese residential architecture and possessing significant conservation value. Currently, Yunnan Province alone has 14 historical and cultural cities, 25 historical and cultural towns, 37 historical and cultural villages, 19 historical and cultural streets, and 778 traditional villages. These traditional towns and villages are mostly constructed of earth and wood, brick and wood, or entirely of wood, with low fire resistance and a high risk of fire. Since 1949, 148 fires have occurred in various villages within the province, resulting in losses to more than 10 households, such as the fires in Dukezong and Wengding villages, which have had a significant negative impact on Yunnan Province's tourism industry and the protection of traditional villages.

[0019] like Figure 1 As shown, a method for assessing the risk of fire spread in a wooden building complex and formulating prevention and control strategies includes the following steps: S1. Obtain fire spread risk factors for the target building complex, including: Using drone oblique photography technology, macroscopic information on individual buildings in the complex was obtained, including: the location, geometric dimensions, scale, terrain features, and fire access roads of the target village. Micro-level information on each individual building in the complex was obtained through on-site surveys, including: building attributes, business type attributes, structural measures, fire water sources, fire protection facilities, and fire hazard sources. In this embodiment, drone photography or open-source map data is used to collect information on the location, area, scale, and geographical distribution characteristics of each individual building in the complex. Further, through on-site surveys, precise parameters related to individual building dimensions, architectural style, building opening ratio, amount of combustible materials, and fire spread are obtained. See the case study for details. Figure 2 and Figure 3 ,in, Figure 2 (a) Mapping of the UAV in Case 1, Figure 2 (b) is the architectural layout plan for Case 1. Figure 2 (c) is the fire protection pipe network diagram for Case 1; Figure 3 (a) Mapping of the UAV in Case 2. Figure 3 (b) is the architectural layout plan for Case 2. Figure 3 (c) is the fire protection network diagram for Case 2. There are 215 buildings in the area of ​​Case 1, of which 142 are fire-resistant buildings of level III or IV, accounting for approximately 66.05%; there are 145 buildings in the area of ​​Case 2, of which 59 are fire-resistant buildings of level III or IV, accounting for approximately 40.69%.

[0020] S2. Based on the elements obtained in S1, the expected potential fire risk index of the building complex is obtained and the potential fire spread risk of the building complex is classified. S2.1 Construct a calculation expression for the potential spread risk index of a fire spread scenario; Potential fire spread loss refers to the maximum potential spread loss of a building complex without fire fighting and rescue intervention (including the activation of automatic fire extinguishing systems). It can be quantitatively described by the building complex potential fire spread risk index. The higher the potential fire spread risk index, the stronger the building complex's ability to spread fire and the greater the spread loss. When defining the potential fire spread risk index of a building complex, the permissible fire spread loss of the building complex can be used as the critical value to distinguish the fire spread risk level of different traditional village and town building complexes. The potential fire spread risk index of building complexes in fire spread scenarios Defined as: fire spread scenario The ratio of fire spread loss to the allowable fire spread loss of traditional village and town building complexes is expressed as: In the formula, Scene of fire spreading The potential fire spread risk index; To mitigate the permissible fire spread damage to traditional village and town building complexes, according to the "Rural Fire Prevention Code" and the "Technical Guidelines for Fire Prevention and Control in Ancient Towns and Villages," the area of ​​densely built-up areas with high fire resistance ratings should not exceed 5000 m². 2 For densely built-up areas with low fire resistance ratings, the floor area should not exceed 3000m². 2 When the area exceeds the prescribed requirements, a fire-resistant isolation zone must be installed for separation; therefore, this invention selects a fire-fighting zone with a floor area of ​​3000m². 2 5000m 2 This serves as the critical value for the permissible fire spread loss in densely built areas with both low and high fire resistance ratings. Scene of fire spreading Potential fire spread and losses; Among them, the fire spread scene Potential fire spread losses The maximum value is obtained as follows: S2.1.1 Analyze the fire spread process of the building complex, including three stages: the development of fire inside the building, the spread of fire in different rooms within the building, and the spread of fire between buildings; Without intervention, a building fire typically progresses through several stages: smoldering, the emergence of open flames, fire growth, flashover, fire spreading from the originating room to other rooms, fire spreading from the originating building to other buildings, and eventual extinguishing. It can be broadly categorized into three stages: indoor fire development, fire spreading between different rooms within the building, and fire spreading between buildings. The fire intensity over time can be analyzed using the heat release rate-time formula. Q ( t The curve is used for description, see Figure 4 As shown; See the process of fire spread and development in a single building Figure 4 (a) Figure 4 As shown in (b), when the combustibles indoors are ignited, the fire enters the initial growth stage, at which point the fire can be considered to be in the initial growth stage according to t. 2 As the fire model grows, the fire intensity increases relatively slowly at this stage, gradually accelerating. When the fire develops to a certain extent, a sudden explosion occurs indoors, igniting most of the combustibles. The rate of heat release continues to increase, and the fire temperature rapidly rises to its peak, marking the start of the fully developed fire phase. At this point, when the wooden doors, windows, walls, and floors exceed their fire resistance limits, the fire spreads horizontally along wooden doors, windows, partitions, and corridors, and vertically along wooden floors, exterior windows, and stairwells. The fire development process of a single building can be analyzed through field simulation or area simulation. Field simulation divides the single building into several micro-elements and uses fluid dynamics theory to analyze the spatial distribution and temporal variation characteristics of the velocity, temperature, and concentration fields of the indoor gases using the Navier-Stokes equations to determine the building's combustion time under different conditions. Q a Such as the common FDS simulation; zone simulation divides a single building into zones consisting of several rooms, and determines the zone's governing equations by conserving mass and energy in each zone. Q a ; The spread of a fire within a building complex is primarily a process in which the fire breaks through the limitations of the existing buildings and spreads to neighboring buildings. (See...) Figure 4 As shown in (c), the fire spread paths between buildings are mainly thermal radiation and fire plume. In fire spread analysis, the ignition point is considered an independent ignition source, while non-ignition points are excluded. j Receives thermal radiation flux from nearby combustible materials Greater than the critical heat flux for wood ignition At that time, it is considered that there was no fire ignition point. j It was ignited, among which Take 12.5kW / m 2 The expression is as follows: In the formula, The wall emissivity is set to 0.8; The Stefan-Boltsman constant is taken as 5.67 × 10⁻⁶. -8 W / (m 2 .K); Points where no fire has occurred j The wall surface temperature (K); This represents the number of fire ignition points, among which... Index of the number of fire nodes; For the first i The fire ignition point relative to the non-fire point j The radiation angle coefficient of the wooden exterior wall; The convective heat transfer coefficient of the wall can be calculated using the correlation equation from large-space natural convection heat transfer experiments. In this paper, it is approximated as 7.6 W / (m²). 2 .K); Fire ignition point i The thermal radiation power is calculated by referring to the ignition source calculation method of NFPA92B; for The equivalent superposition temperature of the fire plumes at each ignition point; The expression is as follows: In the formula, The percentage of openings in the exterior walls of a building; This refers to the proportion of heat energy released in the form of thermal radiation during a fire, which is generally taken as 1 / 3. This represents the heat release rate-time curve for the a-th building; The expression is as follows: In the formula, Fire ignition point i Fire plumes caused at unignited nodes j The temperature increase at the wall surface causes the resulting heat plume to be tilted by the ambient wind, raising the temperature downwind. Figure 5 As shown, the temperature change along the plume smoke axis is related to the heat release rate and height of the fire, as expressed in the following expression: In the formula, z represents the node that has not yet ignited. j From the point of origin of the fire to the point of ignition i The height (m) of the projection of the fire plume axis of the building; The inclination of the plume is mainly controlled by environmental conditions such as wind force and direction, and temperature. The angle between its axis and the horizontal plane can be calculated by the following formula: In the formula, Fire ignition point i The angle between the plume axis of the building and the horizontal plane; Let g be the ambient wind speed (m / s); g is the acceleration due to gravity, taken as 9.81 m / s². 2 ; Specific heat of hot flue gas (kJ / kg·k); air density (kg / m³) 3 ); The ambient temperature (K); Fire ignition point i The building's floor area (m²) 2 ); Ignition point i Unignition points caused by plumes generated by buildings j Temperature rise at the building's exterior walls It can be calculated using the following formula: In the formula, Points where no fire has occurred j From the point of origin of the fire to the point of ignition i Distance (m) between the fire plume axis of the building; Furthermore, field-network or zone-network composite simulation technology is a numerical calculation method widely used in the analysis of fires in building complexes. When simulating the spread of fires in building complexes, a similar "network" concept is adopted, where individual buildings are modeled as nodes in a network. The physical quantities of each node, such as temperature and heat release rate, are represented by a set of uniform parameters. Based on this, the ignition process between different nodes is analyzed to determine the arcs connecting the nodes. (See...) Figure 6 As shown; Each individual building in the complex is considered a node. t At any given moment, the physical quantities such as temperature and heat release rate of each node are represented by a set of state parameters. It means that among them Let i be the time when the ignition node is ignited. For the initial ignition point, =0, when the node is not ignited. >0, can take an infinite value; Fire ignition point i The average temperature (T) is . t and The function, when t < At that time, it indicates the point at which the fire started.i If not ignited, both are 0, when t≥ At that time, the point of ignition i Both are in a state of combustion, and both refer to the combustion time. ( = t - The function ) can be used to check and update the state of each node at time t during fire spread simulation analysis. Simulates the spread of fire within a building complex; the simulation process for fire spread between buildings is described below. Figure 7 As shown; The specific simulation process can be carried out according to the following steps: (1) Simulation of fire in a single building: Based on the building characteristics, analyze the fire development process of a single building and determine the status of the building at different time points. ; (2) Determine the initial conditions for fire spread simulation, mainly including environmental conditions such as ambient wind speed and ambient temperature, the number of building cluster nodes, and the simulation time step d. t and total number of simulation steps N t The simulation conditions, initial node conditions, and ignition time for the initial ignition node. =0, initial state is set to For nodes that have not yet ignited, the ignition time is taken as an infinite value, which can be used in the calculation. =( N t +1)dt, whose initial state is set to ; (3) Update different simulation times = k dt, k =1,2,…,N t The node status at that time is used to determine the ignition status of different nodes; node status updates can be performed as follows: ① By using the HRR and temperature interpolation curves of individual buildings, all fire-initiated nodes are determined through interpolation (meeting the requirements). ≤ )exist Moment and ; ② Calculate the relationship between fire spread between buildings and each non-fired node according to the method for determining the fire spread between buildings. j (satisfy =( N t +1)dt) in Total heat flux generated at time ; ③ Determine the point where no fire has started jWhether it was ignited, if not, the point of origin. j If ignited, No fire started j The status was updated to ; ④ Set a 1× M The row vector g serves as the ignition time vector in the simulation process, recording the spread of the building fire over time. The corresponding row vector g contains the ignition time vector. i Each element records the fire ignition point. i The time it took to be ignited; S2.1.2 Based on the fire spread process of the building complex, construct a directed graph of fire spread in the building complex; Treating individual buildings as nodes in a directed graph, and based on the fire spread analysis process described above, the spread relationships and spread times between adjacent buildings are determined, and an adjacency matrix is ​​established. The data stores the connection relationships between network nodes, corresponding to the direct ignition relationships (edges) between different nodes in the building complex. Let the adjoining vector of the directed graph be denoted as When there are nodes in a directed graph Pointing to neighbor nodes When the edge is, then ( For nodes Ignite neighboring nodes (Time), to obtain the adjacency matrix considering time weights. ; Based on the adjacency matrix considering time weights The fire spread matrix is ​​calculated using a directed graph path search algorithm. Used to describe the direct or indirect connections between network nodes, the fire spread vector is denoted as... When node with neighboring nodes If there are directly or indirectly connected edges, then , representing a node In the shortest time Ignite neighboring nodes ; Fire spread matrix and shortest time The solution method is as follows: From nodes in a directed graph network Start from the directed edge and reach the neighbor node The path with the minimum sum of edge weights is the building. i Spread to buildings jTo find the shortest path in time, various shortest path algorithms have been developed, among which the more common ones include Dijksra's algorithm, A* algorithm, Bellman-Ford algorithm, and Floyd-Warshall algorithm. Dijksra's algorithm is a typical single-source shortest path method, used to calculate the shortest path from one node to all other nodes. Its main characteristic is that it expands outwards layer by layer from the starting point until it reaches the destination. This algorithm uses a breadth-first search algorithm to determine the nodes. and neighboring nodes The shortest path between nodes, when considering the weights of directed edges, reflects the relationship between nodes. The fire spread from its origin to neighboring nodes. The time required; without considering the weights of directed edges, this shortest path reflects the nodes The fire spread from its origin to neighboring nodes. The required number of intermediate nodes, and the algorithm steps are as follows: ① Let set S store the visited nodes, where S∈V, and V represents the set of all nodes (i.e., all individual buildings) in the building cluster network; define For nodes Ignite neighboring nodes Time, if and If there are connected edges, then Equal to the weight of its edge ( =0), if and If there are no connected edges, then = inf; sets one M×M Auxiliary matrix T ,make =0, and the initial value of the remaining elements is inf; ②Let set From the set VS Selecting nodes The node with the smallest edge weight connected to its adjacent nodes If it exists, then Add to collection S Update auxiliary matrix T If the first step is not found, the algorithm proceeds to the next step; otherwise, the algorithm terminates and outputs set S. Update auxiliary matrix T The expression is as follows: In the formula, Represents a node The node with the smallest edge weight connected to its adjacent nodes The minimum direct ignition time; Represents a node The node with the smallest edge weight connected to its adjacent nodes The direct ignition time; ③ Find the node with the smallest edge weight connecting its adjacent nodes. As the intermediary point, continue from the set VS Select with node The neighboring node with the smallest edge weight connected to its adjacent node. If it exists, then Add to collection S In the middle, update the auxiliary matrix T If the first step is not found, the algorithm proceeds to the next step; otherwise, the algorithm terminates and outputs a set. S ; Update the auxiliary matrix using neighbor nodes. T The expression is as follows: In the formula, This represents the node with the smallest edge weight connecting adjacent nodes. to neighboring nodes The direct ignition time; ④ Repeat step ③ until all nodes have been traversed, i.e., the set is complete. VS =Φ, the algorithm ends, output set S and auxiliary matrix. T The resulting auxiliary matrix T This is the fire spread matrix that takes time weight into account. ; matrix The column number and value corresponding to the non-inf elements represent the node. After the fire starts, the node number that is directly or indirectly ignited and its shortest time; S2.1.3 Calculate fire spread losses based on the directed graph of fire spread in the building complex; The loss in a fire spread scenario is defined as the number or area of ​​buildings ignited by the burning building, which can be expressed as the sum of the areas or numbers of each ignited building; it can be calculated using a fire spread matrix for a building complex. The matrix is ​​set up... For the spread matrix that does not consider time weights, the matrix's _____ Row elements are calculated as follows: Spread matrix without considering time weights The first in The column number corresponding to the element with a value of 1 in a row indicates the node. After the fire starts, the node numbers that can be ignited and the maximum fire spread losses caused by the fire. The expression is as follows: In the formula, Fire spread matrix The OK; S =[s1...s a ...s M ] T Let s be a vector composed of the areas of the individual buildings in the complex, where s a Let be the area of ​​building a. If the area weights of individual buildings are not considered... S =[1,1,…,1] T It is a column vector with M rows and each element having a value of 1; S2.2 Based on the calculation expression of the potential fire spread risk index in multiple fire spread scenarios, construct the expected value of the potential fire spread risk index of building clusters in multiple fire spread scenarios; The construction method involves treating each building in the complex as the ignition point and calculating the fire spread scenarios. The potential fire risk index, taking into account the probability of different fire spread scenarios; The expression for the expected value of the potential fire spread risk index for building complexes with multiple fire spread scenarios is as follows: In the formula, Describing the spread of a fire The probability of occurrence, and the spread scenario in the event of a fire. The probability is directly proportional to the building area, expressed as: In the formula, Indicates the first The area of ​​each building; This indicates the number of buildings in the complex, where... An index representing the number of buildings; if the influence of the area weight of each individual building is not considered, then the probability of fire in each individual building is the same, 1 / M ; S2.3. Based on the expected value of the potential fire spread risk index of the building complex under the constructed multiple fire spread scenarios, the potential fire spread risk of the building complex is divided by the preset boundary value. Potential fire risk index of building complex I L The larger the value, the greater the damage caused by the spread of fire within the building complex. I L When the value is greater than 1, the potential fire spread risk index of the building complex exceeds the permissible loss, indicating a high risk of fire spread. To differentiate the fire spread risk levels of different building complexes, a potential fire spread risk index for the building complex is selected. I L A value of 0.5 is used as the dividing line between low and medium fire spread risk.I L A value of 1 is used as the dividing line between medium and high fire spread risk. (Building complex fire spread risk level) L FR It can be divided according to the following formula: ; In this embodiment, fire spread simulation technology is used to simulate the fire spread process between buildings, determine the ignition relationship and ignition time between each node, draw the spread path between each node, and construct a directed fire spread graph of the village building complex. Figure 8 , Figure 8 (a) is a diagram showing the spread of all fire scenarios in Case 1. Figure 8 (b) is a diagram showing the fire spread of all fire scenarios in Case 2. The arrows in the diagram indicate the ignition direction between nodes. The gray nodes in the diagram are brick-concrete structures with high fire resistance ratings and large spacing between buildings. No fire spread between buildings occurred during the fire spread simulation. The fire spread areas in Case 1 and Case 2 were mainly concentrated in densely populated areas dominated by contiguous wooden structures. In Case 1, 129 scenarios involving fire spread occurred among the 142 wooden structures, accounting for 90.85%. In Case 2, 50 scenarios involving fire spread occurred among the 59 wooden structures, accounting for 84.75%.

[0021] By obtaining the spread losses for different fire scenarios from S2.1.1 to S2.1.3, and further combining this with the calculation method of the potential fire risk index, the potential fire spread risk index for the above cases under different fire spread scenarios is calculated respectively, such as... Figure 9 As shown, Figure 9 (a) shows the losses and potential fire risk index for different fire spread scenarios in Case 1. Figure 9 (b) shows the losses and potential fire risk index for different fire spread scenarios in Case 2.

[0022] Depend on Figure 9 It can be seen that the spread losses and potential fire risk indices differ significantly across different fire spread scenarios within the building complex. Table 1 shows the statistical analysis of the potential fire risk indices for different fire spread scenarios in the above cases. Table 1: Statistics of Potential Fire Risk Index As can be seen, in Case 1, the potential fire risk index of each individual building is mainly between 0 and 1, accounting for approximately 89.77% of the fire spread scenarios in the building complex. The expected potential fire spread risk index of the entire building complex is 0.414, which belongs to the low fire spread risk level area. In Case 2, the potential fire risk index of each individual building is less than 0.5, and the expected potential fire spread risk index of the entire building complex is 0.061, which also belongs to the low fire spread risk level area, and its fire spread risk is much lower than that of Case 1.

[0023] S3. Calculate the fire fighting and rescue capability of the building complex and obtain the expected fire fighting and rescue capability index. The fire fighting and rescue capability index needs to comprehensively consider factors such as fire fighting and rescue response time, automatic fire extinguishing system action time, fire spread speed of building complex and maximum water supply capacity of building complex; during the fire, fire fighting is a key factor in preventing the spread of fire. The intervention time of different fire fighting forces determines the fire situation and the size of the fire, which directly affects the fire brigade's fire fighting strategy and water demand during fire fighting. Therefore, the calculation of the fire fighting and rescue capability index in this paper considers two aspects: (1) the amount of water needed to control the fire when fire fighting forces intervene; (2) the water supply capacity that traditional villages and towns can provide. Fire spread scene x Firefighting and rescue capability index It can be calculated using the following formula: In the formula, Time taken for firefighters to intervene (min); Scenes of fire spread when firefighters intervene. x Firefighting water consumption (L / s); Firefighting water supply for village and town building complexes (L / s); Obviously, the time it takes for firefighters to intervene. The smaller the fire, the smaller the fire spread and the lower the water demand for firefighting. The lower, The smaller the building complex, the stronger its fire fighting and rescue capabilities; the town's water supply capacity... The larger, The smaller the building complex, the stronger its fire fighting and rescue capabilities. This is based on obtaining all fire spread scenarios. x After determining the fire fighting and rescue capability index, considering the probability of different fire spread scenarios, the expected fire fighting and rescue capability index of building complexes under multiple fire spread scenarios can be obtained. : Firefighting capability index of building complex It is a function of the time it takes for firefighters to intervene. The larger the value, the higher the demand for firefighting water during fire rescue, assuming the firefighting force intervention time. When known, it can be simply written as To refine the supply and demand relationship of water for fire and rescue, refer to Table 2. The values ​​of are used to classify the fire water supply situation of the building complex into three levels: sufficient water supply, basically meeting the fire water demand, and insufficient fire water supply. The table below shows the supply and demand relationship of fire rescue water. Table 2: Supply and Demand Relationship of Water for Firefighting and Rescue Firefighter intervention time Scenes of fire spread when firefighters intervene. x Firefighting water volume Fire water supply for village and town building complexes The calculation method is as follows: Determine the time for fire and rescue intervention. The time it takes for firefighters to intervene after a fire breaks out often determines the size of the fire and thus affects the water demand for firefighting. Therefore, the intervention time of firefighters must be considered when calculating firefighting water demand. The fire department's intervention time is mainly the time from the onset of the fire to the deployment of equipment and commencement of firefighting efforts. It consists of the time taken for a series of consecutive events, as detailed below. Figure 10 As shown, the calculation method is as follows: In the formula, Alarm time refers to the time required from the occurrence of a fire to the alarm notification reaching the alarm center, which mainly depends on the alarm type and the type of automatic alarm device. Dispatch time refers to the time required from the alarm center receiving a fire alarm to completing the dispatch task allocation for the fire brigade. It includes the alarm information reception time and allocation time, and is related to the dispatch system used and the system's operating mode. Preparation time is the time from when the fire station receives the emergency call notification until the firefighters and firefighting equipment leave the fire station. It is related to the type of fire brigade and the level of training; Travel time refers to the time required for a fire brigade to travel from the fire station to the fire scene with firefighting equipment. It depends on the distance between the fire station and the fire scene and the speed of the fire truck. The time required to deploy firefighting equipment refers to the total time it takes for firefighters to put on breathing apparatus, retrieve firefighting equipment, and set up and connect water hoses after arriving at the fire scene. It is related to the quantity and type of equipment required for the fire, as well as the experience and training level of the firefighters. The intervention time of the fire brigade can be obtained through historical fire rescue data statistics or the FireBrigade Intervention Model (FBIM). Statistical analysis is conducted by combining daily training data and fire rescue data from active-duty fire brigades, volunteer fire brigades, and other fire rescue forces to obtain statistical data on key times during the firefighting and rescue process, including firefighting force deployment, preparation, vehicle movement, on-site reconnaissance and questioning, donning of breathing masks, connection of hoses and fire hydrants, and arrival at the designated location to extinguish the fire. Based on this, an FBIM model is established using Monte Carlo simulation technology to analyze and calculate the intervention time of firefighting and rescue forces when a building fire occurs. The alarm time, dispatch time, preparation time, vehicle movement time, and deployment time of firefighting equipment can be determined according to Table 3 based on literature. Table 3: Values ​​of Fire Intervention Time at Different Stages Determining the reliability of fire-fighting water supply: The fire-fighting and rescue capability index of a building complex is the ratio of the water required to control a fire when fire-fighting forces intervene to the traditional fire-fighting water supply capacity of villages and towns. Without considering the impact on residents' daily water consumption, the fire-fighting water supply capacity of the building complex remains constant; however, the fire-fighting water demand is affected by the scale of the fire in the building complex when fire-fighting forces intervene. Its calculation needs to be determined by combining the changing pattern of the fire scale over time and the probability distribution analysis of the fire-fighting intervention time. For detailed workflow, see [link to documentation]. Figure 11 As shown. The specific steps are as follows: (1) The fire development process of a single building and the fire spread relationship between buildings are analyzed using S2.1.1 to determine the fire spread adjacency matrix that takes time weight into account. (2) The S2.1.2 path search algorithm is used to calculate the spread matrix considering time weights. To determine the building ignition time sequence under specific fire spread scenarios; (3) Based on the ignition time of different buildings under a specific fire spread scenario, the fire heat release rate curves of individual buildings in different combustion states are superimposed to obtain the specific fire scenario. x The fire heat release rate is determined to identify the fire water demand in different fire scenarios. ; (4) Determine the fire water supply capacity by combining the water supply network hydraulic model or on-site fire hydrant water discharge test, so as to determine the fire water supply and demand relationship; (5) Taking into account the time of fire rescue intervention, the fire-fighting water demand during fire rescue is determined as the basis for fire water supply design; Firefighting water requirements are determined using the formula given by the NZFESG method. The calculation method is as follows: In the formula, Scene of fire spreading At the moment of fire intervention The rate of heat release from the fire, depending on the specific fire spread scenario. The ignition time of different buildings was used to superimpose the fire heat release rate curves of individual buildings under different combustion states. The fire extinguishing efficiency of water, that is, the efficiency of water in absorbing fire energy, is generally between 0.1 and 0.3. In this invention, it is taken as 0.2. The water absorption extinguishing capacity rate is taken as 2.26 MW / L / s; Fire water supply for village and town building complexes The fire water supply capacity is determined by combining on-site fire hydrant water discharge tests and simulation methods to calculate the fire water supply volume, thereby establishing the relationship between fire water supply and demand. The steps include: Calculation of fire water supply using the on-site fire hydrant water discharge test method: Based on the test results of the on-site fire hydrant water discharge test, the fire water supply capacity assessment values ​​recommended by NFPA 291 are adopted. It can be calculated using the following formula: In the formula, The total flow rate of water discharged from the fire hydrants (L / s) was measured during the test. The pressure loss when the pressure drops to the desired residual pressure, i.e., the fire flow rate is... Pipeline head loss (m); The pressure loss measured during the test, i.e., the fire flow rate, is equal to... Pipeline head loss (m); where, and The expression is as follows: In the formula, The measured pressure value (mH2O) is when the water flow rate of the fire hydrant is zero. The minimum allowable pressure (mH2O) at the reference point is taken as 10m according to the specification. The test value (mH2O) is for fire hydrants. Simulation method for calculating fire water supply: Based on the calculation of fire water supply using on-site fire hydrant water discharge tests, an iterative algorithm is used. Through a network sequential search process, an improved flow estimate is obtained in each iteration. This method is relatively easy to implement in existing network solution algorithms, and its expression is as follows: In the formula, This represents the normal water demand under static conditions. When the value is zero, the calculation expression for fire water supply using the on-site fire hydrant water discharge test method is consistent with the calculation expression for fire water supply using the simulation method. This means that the calculation expression for fire water supply using the on-site fire hydrant water discharge test method is a special case of the calculation expression for fire water supply using the simulation method. As shown in the above formula, when... constantly approaching At that time, = ; Update using the following steps : (1) Construct a hydraulic model of the pipe network, perform operational analysis, and record the node flow rates. Pressure measurement value when the water flow rate of the fire hydrant is zero ,when < At that time, It is zero; when = At that time, = ;when > At that time, then order = +△, where △ is an arbitrary increment; (2) Run the pipeline hydraulic model and calculate the nodal flow rates. = When +△, the corresponding nodal water pressure value; (3) Calculate the fire water supply volume using the simulation method. Output the analysis results; (4) Check convergence; if relative flow accuracy is... ε When less than the small tolerance (take 10) -4 If the condition is met, terminate the calculation; otherwise, replace the original value. , for , ,make = Repeat steps (2) to (4) until the relative flow accuracy is achieved. ε The requirements are met; during the convergence check, the relative flow accuracy is [not specified]. ε The expression is as follows: The Boulos algorithm steps described above can be implemented using EPANET 2, an open-source software developed by the U.S. Environmental Protection Agency. EPANET 2 provides functions such as water supply network model construction, hydraulic simulation, water quality simulation, and result presentation. First, the water supply network is simulated as nodes and pipe segments between nodes. Nodes mainly include connecting nodes, water tanks, and reservoirs, while pipe segments mainly include pipes, pumps, and valves. The nodes and pipe segments are drawn and input to complete the construction of the hydraulic model of the water supply network. Then, combining the above algorithm steps, the secondary development function of the EPANET 2 toolkit is used to realize the fire-fighting water supply capacity assessment of the water supply network. In this embodiment, the fire intervention time for the locations of Case 1 and Case 2 is given based on the FBIM model, such as... Figure 12 As shown, Figure 12 (a) is a timeline of fire department intervention in Case 1. Figure 12 (b) is the fire intervention time diagram for Case 2. The selected area for Case 1 is located in the center of Guzhen Town, about 1.5km from the active fire station. The roads in the area are narrow, with many slopes and stairs, making movement relatively slow. At the 90th percentile, its fire intervention time is 10.67 minutes. Therefore, 11 minutes can be taken as the fire intervention time for Case 1. The selected area for Case 2 is located in the outer area of ​​Guzhen Town, about 2km from the active fire station. The road conditions in the area are better. At the 90th percentile, its fire intervention time is 9.26 minutes. Therefore, 9 minutes can be taken as the fire intervention time for Case 2.

[0024] The propagation matrix considering time weights is calculated using a path search algorithm. The ignition time series of buildings under a specific fire spread scenario was determined. Then, the fire heat release rate curves of individual buildings in different combustion states were superimposed based on the ignition time of different buildings under the specific fire spread scenario to obtain the fire heat release rate under the specific fire scenario. Determine the fire water demand for different fire scenarios Considering the fire intervention time in the above cases, provide the fire water demand taking into account the fire intervention time, such as... Figure 13 As shown, Figure 13 (a) represents the fire water demand in Case 1. Figure 13 (b) is the fire water demand in Case 2.

[0025] In this embodiment, based on the distribution of fire pipe networks and fire hydrant locations in Case 1 and Case 2, hydraulic models of the pipe networks in Case 1 and Case 2 are constructed using EPANET2, such as... Figure 14 , Figure 15 As shown, where Figure 14 (a) is the official modeling diagram for Case 1. Figure 14 (b) is a diagram showing the node elevation and pipe segment length in Case 1; Figure 15(a) is the official website modeling diagram for Case 2. Figure 15 (b) shows the node elevation and pipe segment length diagram for Case 2; Case 1 includes 32 nodes and 33 pipe segments with a diameter of 200 mm. Case 2 includes 25 nodes and 25 pipe segments with a diameter of 100 mm. The friction head loss was calculated using the Hazen-Williams formula, and the Boulos algorithm was used to assess the fire-fighting water supply capacity of the pipe network. The assessment results are shown in Tables 4 and 5. Table 4: Water Supply Network Node Pressure and Fire Water Supply Volume in Case 1 Table 5: Water Supply Network Node Pressure and Fire Water Supply Volume in Case 2 Based on the calculation method of the building complex fire fighting and rescue capability index, and taking into account the fire intervention time in different cases, combined with the fire water demand in different fire spread scenarios and the assessment results of the building complex's fire water supply capacity, the fire fighting and rescue capability indices for different fire spread scenarios of each case building complex are given as follows: Figure 16 As shown, Figure 16 (a) represents the firefighting and rescue capability index for different fire spread scenarios in Case 1. Figure 16 (b) is the fire fighting and rescue capability index for different fire spread scenarios in Case 2.

[0026] Figure 16 It can be seen that the fire fighting and rescue capability indices differ significantly under different fire spread scenarios in the building complex. Table 6 shows the statistical analysis of the fire fighting and rescue capability indices for different fire spread scenarios in each case. Table 6: Statistics on Firefighting and Rescue Capability Index Table 6 shows that in Case 1, the fire-fighting and rescue capability index for different fire spread scenarios was mainly between 0 and 1, accounting for approximately 94.42% of the fire spread scenarios in the building complex, with only 12 scenarios having an index greater than 1. In Case 2, only two scenarios had a fire-fighting and rescue capability index greater than 1, and the number of scenarios with an index less than 0.5 accounted for approximately 81.38%. These results indicate that the municipal water supply network in the areas where Cases 1 and 2 are located has good capacity and sufficient water supply, which can meet the fire-fighting water requirements under fire intervention conditions.

[0027] S4. Construct a hierarchical classification matrix of fire safety characteristics of building complexes and conduct risk level assessment and classification. The method for constructing a hierarchical classification dot matrix map of fire safety characteristics of building complexes is as follows: based on the fire fighting and rescue capability index. The horizontal axis represents the potential fire spread risk index of the building complex. The vertical axis represents the potential fire spread risk index of the building complex. Based on the expression and the table of water supply and demand for fire rescue, a two-dimensional dot matrix diagram of the fire safety characteristics of traditional village and town building complexes is established; Based on the obtained building complex and The distribution of points corresponding to the values ​​in the dot matrix diagram allows us to obtain the fire safety characteristic classification and risk level of the building complex. (See...) Figure 17 As shown; based on the location of the wooden building complex in the dot matrix diagram, the fire safety characteristics of the building complex are divided into 9 categories, and the fire spread risk level is divided into four risk levels: low, medium, high and extremely high according to different categories; In this embodiment, as Figure 18 As shown, Figure 18 (a) A dot matrix diagram classifying fire safety characteristics for different fire spread scenarios in Case 1; Figure 18 (b) A fire safety feature classification matrix for different fire spread scenarios in Case 2; using the fire extinguishing and rescue capability index and the potential fire spread risk index of the building complex as the horizontal and vertical axes, two-dimensional matrix maps of the fire safety features of each fire spread scenario in each case building complex are established. Combined with the fire safety feature classification matrix maps, it can be seen that in Case 1, the fire safety feature points of each fire spread scenario are mostly located in low-risk and medium-risk areas, with only a small portion located in high-risk and extremely high-risk areas. There are three extremely high-risk scenarios, indicating that there are some areas with a high risk of fire spread in this building complex, and the fire water supply capacity basically meets the needs of fire rescue and extinguishing. In Case 2, the fire safety feature points of each fire spread scenario are mostly located in low-risk and medium-risk areas, with only three buildings located in high-risk areas. The fire spread loss of each individual building is relatively low, and the fire extinguishing and rescue capability index is mainly in low-risk and medium-risk areas, indicating that the fire spread risk of this building complex is low, and the fire water supply capacity basically meets the needs of fire rescue and extinguishing.

[0028] Based on the potential spread losses and fire fighting and rescue capabilities of different fire spread scenarios in the building complex, the probability Pr of different fire spread scenarios occurring in the building complex is considered. x The expected values ​​of the potential fire spread risk index and the expected value of the fire fighting and rescue capability index of the building complex considering multiple fire spread scenarios are calculated according to the formula, as shown in Table 7. Table 7: Fire Safety Characteristics of Building Complexes S5. Based on the hierarchical classification matrix of fire safety characteristics of building complexes, formulate fire spread prevention and control strategies for building complexes with fire safety characteristics; By using a hierarchical classification matrix of building cluster fire safety characteristics and the location of different building clusters within the matrix, fire safety problems within the building clusters can be diagnosed. (See...) Figure 19As shown, there are three main situations: (1) the fire spreads too far; (2) the fire fighting and rescue capabilities are insufficient due to the fire fighting action starting too late or insufficient water supply; and (3) both of the above situations occur at the same time. Based on the diagnosis of fire safety problems, fire spread prevention and control strategies for different building groups can be formulated from the perspectives of controlling the fire spread loss of building groups and improving the fire fighting and rescue capabilities of building groups, based on the fire safety characteristics of different building groups. By analyzing the location of different building complexes in the dot matrix map and diagnosing fire safety issues, a fire safety characteristic-based dot matrix prevention and control strategy is formulated based on the two objectives of controlling the spread of fire damage and improving the fire fighting and rescue capabilities of different building complexes. This strategy is tailored to the fire safety characteristics of each building complex. When the fire is relatively large, by cutting off the spread path of important nodes, the passive fire resistance of the building or building complex as a whole is gradually improved, reducing the risk of fire spread in the building complex; when the fire fighting and rescue capability index is high... When the fire is large, the rescue capacity of the building complex may have three problems: (1) untimely fire fighting and rescue; (2) insufficient water supply; (3) the above two problems occur at the same time. Therefore, it is necessary to implement prevention and control measures from the perspectives of early intervention of fire rescue forces and improving the water supply capacity of village and town building complexes. Based on the different positions of different building complexes in the classification matrix, their corresponding prevention and control priorities or improvement strategies are formulated according to the following principles: ① For building complexes with both low potential fire risk index and low fire fighting and rescue capability index, the focus of prevention and control should be on controlling the fire risk of individual buildings and strengthening fire safety education to prevent small fires from causing fatalities; ② For building complexes with a potential fire risk index between [0.5, 1), the focus should be on controlling the fire spread risk of the building complex, identifying important buildings, and cutting off the spread path; ③ For building complexes with a potential fire risk index between [1, +∞), the focus should be on controlling the fire spread risk of the building complex, identifying important buildings, cutting off the spread path, improving the fire resistance of buildings, and strengthening fire source control and the early intervention capability of fire fighting forces. ④ For building complexes with a fire fighting and rescue capability index between [0.5, 1), it indicates that the existing fire fighting and rescue capability can basically meet the fire fighting and fire protection needs; ⑤ For building complexes with a fire fighting and rescue capability index between [1, +∞), the main focus should be on adding alarm systems and setting up different types of fire rescue to improve the ability to intervene in fire rescue early and enhance fire water supply capacity.

[0029] Different building complexes should formulate fire spread prevention and control strategies or improvement directions according to their zoning locations in the dot matrix diagram, in conjunction with the five prevention and control strategies, as shown in Table 3. The prevention and control priorities and strategy implementation processes in Table 8 should be implemented sequentially.

[0030] Table 8: Fire Prevention Directions for Different Risk Zones In this embodiment, fire safety characteristic classification dot matrix diagrams of different case building complexes are drawn, see... Figure 20 As shown.

[0031] Table 7 Figure 20 It can be seen that the fire safety characteristics of the building complexes in each case are significantly different. Cases 1 and 2 are both located in low-risk areas, and the potential fire spread risk of the building complexes is less than 0.5. However, Case 1 has a relatively high fire spread risk, and the potential spread loss is close to the medium fire spread risk level. The fire water supply at the time of fire intervention can meet the fire fighting water needs.

[0032] Based on the prevention and control strategies of the fire safety feature classification matrix and the fire safety features of the above cases, corresponding transformation directions are given, as shown in Table 9; Table 10: Directions for Renovation The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for assessing the risk of fire spread in a wooden building complex and formulating prevention and control strategies, characterized in that, Includes the following steps: S1. Obtain fire spread risk factors for the target building complex; The methods of obtaining include: Using drone oblique photography technology, macroscopic information on individual buildings in the complex was obtained, including: the location, geometric dimensions, scale, terrain features, and fire access roads of the target village. Micro-level information on each individual building in the complex was obtained through on-site surveys, including: building attributes, business type attributes, structural measures, fire water sources, fire protection facilities, and fire hazard sources. S2. Based on the elements obtained in S1, the expected potential fire risk index of the building complex is obtained and the potential fire spread risk of the building complex is classified. S3. Calculate the fire fighting and rescue capability of the building complex and obtain the expected fire fighting and rescue capability index. S4. Construct a hierarchical classification matrix of fire safety characteristics of building complexes and conduct risk level assessment and classification. The method for constructing a hierarchical classification dot matrix map of fire safety characteristics of building complexes is as follows: a two-dimensional dot matrix map is established with the expected fire fighting and rescue capability index as the horizontal axis and the expected potential fire spread risk index of the building complex as the vertical axis. S5. Based on the hierarchical classification matrix of fire safety characteristics of building complexes, formulate fire spread prevention and control strategies for building complexes with fire safety characteristics, and complete the methodology development.

2. The method for assessing the risk of fire spread and formulating prevention and control strategies for wooden building complexes according to claim 1, characterized in that, The steps for obtaining the expected potential fire risk index of the building complex and classifying the potential fire spread risk of the building complex based on the elements obtained in S1 include: S2.1 Construct a calculation expression for the potential spread risk index of a fire spread scenario; The potential fire spread risk index of a building complex in a fire spread scenario is defined as the ratio of the fire spread loss in a fire spread scenario to the allowable fire spread loss of a traditional village and town building complex, expressed as: In the formula, The potential fire spread risk index for fire spread scenarios; The permissible fire spread damage to traditional village and town building complexes; Potential fire spread losses in fire-prone scenarios; S2.2 Based on the calculation expression of the potential fire spread risk index in multiple fire spread scenarios, construct the expected value of the potential fire spread risk index of building clusters in multiple fire spread scenarios; The construction method is as follows: each building in the building complex is taken as the ignition point, the potential fire risk index of each fire spread scenario is calculated, and the probability of different fire spread scenarios occurring is considered. The expression for the expected value of the potential fire spread risk index for building complexes with multiple fire spread scenarios is as follows: In the formula, Describing the spread of a fire The probability of occurrence; The potential fire spread risk index for fire spread scenarios; The expected value of the potential fire spread risk index for building complexes in multiple fire spread scenarios includes three stages: [0, 0.5), [0.5, 1), and [1, +∞). S2.

3. Based on the expected value of the potential fire spread risk index of the building complex under the constructed multiple fire spread scenarios, the potential fire spread risk of the building complex is divided by the preset boundary value. Take the potential fire spread risk index of the building complex I L A value of 0.5 is used as the dividing line between low and medium fire spread risk. I L A value of 1 is used as the dividing line between medium and high fire spread risk levels in building complexes. L FR It can be divided according to the following formula: 。 3. The method for assessing the risk of fire spread in a wooden building complex and formulating prevention and control strategies according to claim 2, characterized in that, In the expression for calculating the potential spread risk index of the constructed fire spread scenario, the potential fire spread loss of the fire spread scenario is described. The maximum value is obtained as follows: S2.1.1 Analyze the fire spread process of the building complex, including three stages: the development of fire inside the building, the spread of fire in different rooms within the building, and the spread of fire between buildings; S2.1.2 Based on the fire spread process of the building complex, construct a directed graph of fire spread in the building complex; In a directed graph, nodes are defined as individual buildings, edges are defined as the direction of spread between buildings, and weights are defined as the weights of the edges, which represent the time required for spread. The ignition time of directly adjacent buildings is represented using a directed graph adjacency matrix; A spread matrix is ​​constructed based on the adjacency matrix of the directed graph to record the shortest spread time for all node pairs; S2.1.3 Calculate fire spread losses based on the directed graph of fire spread in the building complex; The loss in a fire spread scenario is defined as the number or area of ​​buildings ignited by the burning building, expressed as the sum of the areas or numbers of each ignited building; it can be calculated using a fire spread matrix for a building complex. The matrix is ​​set up... For the spread matrix that does not consider time weights, the matrix's _____ Row elements are calculated as follows: In the formula, The vector represents the fire spread; inf indicates that there are no connected edges between nodes in a directed graph. Spread matrix without considering time weights The first in The column number corresponding to the element with a value of 1 in a row indicates the node. After the fire starts, the node numbers that can be ignited and the maximum fire spread losses caused by the fire. The expression is as follows: In the formula, Fire spread matrix The OK; S =[s1...s a ...s M ] T Let s be a vector composed of the areas of the individual buildings in the complex, where s a Let M represent the area of ​​building a, and M represent the number of buildings in the building complex.

4. The method for assessing the risk of fire spread and formulating prevention and control strategies for wooden building complexes according to claim 1, characterized in that, The calculation of the fire fighting and rescue capability of the building complex yields the following expression for the expected fire fighting and rescue capability index: In the formula, Describing the spread of a fire The probability of occurrence; Describing the spread of a fire x The fire fighting and rescue capability index is expressed as follows: In the formula, For the time required for firefighters to intervene; Scenes of fire spread when firefighters intervene. x The amount of water used for firefighting; Water supply for fire protection in village and town building complexes; The expected values ​​for the fire fighting and rescue capability index include three stages: [0, 0.5), [0.5, 1), and [1, +∞). Based on the expected fire fighting and rescue capability index, the fire water supply situation of building complexes is divided into three levels: sufficient water supply, basically meeting the fire water demand, and insufficient fire water supply.

5. The method for assessing the risk of fire spread and formulating prevention and control strategies for wooden building complexes according to claim 1, characterized in that, The method for formulating fire spread prevention and control strategies for building clusters based on the hierarchical classification matrix of fire safety characteristics is as follows: By using a hierarchical classification map of building cluster fire safety characteristics and the location of the building cluster within the map, fire safety problems within the building cluster can be diagnosed. These problems include: The fire spread too widely; Insufficient firefighting and rescue capabilities due to starting firefighting operations too late or insufficient water supply; Both situations occur simultaneously; Based on the location of building clusters in the dot matrix map and the diagnostic results of existing fire safety problems within the building clusters, a fire safety characteristic classification dot matrix prevention and control strategy is formulated. The classification method of the prevention and control strategy includes: Building complexes with a potential fire risk index and fire fighting and rescue capability index of 0; Building complexes with a potential fire risk index between [0.5, 1); Building complexes with a potential fire risk index between [1, +∞); Building complexes with a fire fighting and rescue capability index between [0.5, 1); Building complexes with a fire fighting and rescue capability index between [1, +∞).

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