Fire intensity quantification method, damage assessment method, safety design method, and device

Abstract

The application discloses a fire intensity quantification method, a damage evaluation method, a safety design method and equipment based on energy equivalence, and relates to the field of performance-based fire protection design of wood structures. The method first obtains a temperature-time curve under an actual fire scene according to an actual fire temperature field model in a space of a wood structure building. Then, the heat introduced into the interior of a wood component under exposure to two types of fires is calculated in combination of the temperature-time curves of the actual fire and the standard fire. Based on the principle of energy conservation, the exposure time of the standard fire required for the same heat conducted into the interior of the wood component as the actual fire, i.e. the equivalent time, is derived. Finally, the fire intensity of the actual fire is quantified by using the calculated equivalent time, and the damage degree of the wood component under exposure to the actual fire is evaluated. The method disclosed by the application can formulate a practical rating method for the preliminary fire risk evaluation of wood structures, and promote the development of the performance-based fire protection design method of modern wood structure buildings.

Description

Technical Field

[0001] This invention relates to the field of building fire safety, specifically proposing a method for quantifying fire intensity based on the principle of energy equivalence. This method aims to transform the fire safety design of wooden structures under real fire conditions into a safety design under standard fire conditions by quantitatively evaluating the fire resistance performance of wooden structures under actual fire conditions. This approach can promote the transformation of fire protection design from traditional code-based methods to performance-oriented fire protection design methods, thus driving the modernization of fire protection design. Background Technology

[0002] The application and development of modern timber-framed buildings are based on providing adequate fire safety. Currently, traditional design methods, using standard fire standards as a benchmark, are only suitable for timber-framed buildings with fewer stories and lower heights. In recent years, with in-depth research on modern timber-framed buildings and the introduction of performance-based fire-resistant design concepts, heavy timber-framed buildings, especially those represented by new engineered wood, have rapidly developed and been applied in multi-story, high-rise, super high-rise, large-space, and long-span structures. Performance-based fire-resistant design has become the most advanced design method in the field of building fire protection. It breaks free from the limitations of traditional methods, giving building structures greater flexibility and creativity, and better balancing building functions and fire safety requirements. However, due to insufficient research on the thermal response and disaster mechanisms of timber structures under actual fire conditions, the lagging development of advanced calculation models, and the imperfection of related fire resistance assessment methods, the application of performance-based fire-resistant design methods for timber-framed buildings is currently limited. This also largely restricts the possibility of further development and widespread application of modern timber-framed buildings. Therefore, promoting the development of performance-based fire safety design for modern timber-framed buildings is of extremely important practical significance. By conducting in-depth research on the behavior of timber structures under fire conditions and developing more accurate calculation models and evaluation methods, we can provide more reliable fire-resistant design guidance for timber-framed buildings, thereby promoting their widespread application in buildings of different types and sizes and driving innovation and development in the field of timber-framed buildings.

[0003] For the past 10-15 years, designers have been dedicated to performance-based fire safety design while meeting design objectives. This requires a performance-based approach to assess the fire resistance of timber components under actual design fire scenarios. However, the thermal and structural models of timber components provided in current standards are based on standard fire conditions and are not applicable to fire assessments under actual design fire conditions. Currently, methods for assessing the response of components under actual design fire conditions mainly include experimental studies, numerical simulations, and equivalent assessments. However, conducting actual fire tests on all design fire scenarios is impractical, and the test results are limited by the specified fire scenarios, making widespread application difficult. The finite element method requires a large amount of parameter data input to build a complete fire structural model, posing a significant challenge for designers. Therefore, there is an urgent need to develop more reasonable methods to assess the fire resistance of structures or components under actual design fire conditions to further promote the development of performance-based fire safety design for timber structures. This could include more accurate performance prediction models, more effective numerical simulation methods, and exploration of equivalent assessment methods for actual fire conditions. The development of these methods will help provide more reliable fire protection design guidance, promote the development of performance-based fire protection design methods in the field of timber construction, and facilitate the widespread application of timber structures in various types of buildings. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a fire intensity quantification method, damage assessment method, safety design method and equipment based on energy equivalence, which can quantify the fire intensity of wooden structures under actual fire exposure into standard fire intensity, and on this basis, fire safety design can be equivalently transformed into standard fire safety design.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0006] This invention first provides a method for quantifying fire intensity based on energy equivalence, comprising the following steps:

[0007] Establish a model of the actual fire temperature field within the space of a timber-structured building;

[0008] Based on the established actual fire temperature field model, the temperature-time curves under actual fire scenarios are obtained;

[0009] Based on the temperature-time curve obtained in the actual fire scenario, calculate the actual total fire heat Q1 of the imported wooden components in the actual fire scenario.

[0010] Calculate the total standard fire heat Q2 introduced into the wooden components under different fire exposure times under standard fire conditions;

[0011] Based on the actual total heat of the fire Q1 and the standard total heat of the fire Q2, the standard fire exposure time value equivalent to the actual fire intensity is obtained.

[0012] The actual fire intensity is determined based on the obtained standard fire exposure time value.

[0013] Based on the temperature-time curve obtained in the actual fire scenario, the actual total fire heat Q1 of the imported wooden components in the actual fire scenario is calculated as follows:

[0014]

[0015] In the formula, A is the surface area exposed to fire, and h conv σ is the convection coefficient, σ is the Boltzmann constant, ε is the emissivity, and T is the emissivity. f.actual T represents the actual fire temperature. s.actual t represents the surface temperature of the wood boundary under the actual fire, t0 represents the initial time, and t represents the actual duration of the fire.

[0016] The surface temperature T of wood boundary under actual fire conditions s.acture for:

[0017]

[0018] In the formula, T0 is the ambient temperature, ρ is the wood density, k is the thermal conductivity of the wood, c is the specific heat of the wood, and h is the density of the wood. R Let q be the radiative heat transfer coefficient. ext.acture This represents the external radiative heat flux density under actual fire conditions.

[0019] The total heat generated by a standard fire, Q2, is calculated for different fire exposure times under standard fire conditions.

[0020]

[0021] In the formula, A is the surface area exposed to fire, and h conv σ is the convection coefficient, σ is the Boltzmann constant, ε is the emissivity, and T is the emissivity. f.atandard For standard fire temperature, T s.stamdard t represents the boundary surface temperature of wood under standard fire conditions. i This refers to the standard fire duration.

[0022] Wood boundary surface temperature T under standard fire conditions s.standard for:

[0023]

[0024] In the formula, T0 is the ambient temperature, ρ is the wood density, k is the thermal conductivity of the wood, c is the specific heat of the wood, and h is the density of the wood. R Let q be the radiative heat transfer coefficient.ext.standard This represents the external radiative heat flux density under standard fire conditions.

[0025] The method for obtaining the standard fire exposure time value equivalent to the actual fire intensity based on the actual total fire heat Q1 and the standard total fire heat Q2 is to obtain the standard fire exposure time value equivalent to the actual fire intensity by making the actual total fire heat Q1 equal to the standard total fire heat Q2.

[0026] Methods for obtaining standard fire exposure time values ​​equivalent to actual fire intensity based on the actual total fire heat Q1 and the standard total fire heat Q2 include:

[0027] Based on the actual total heat of the fire Q1, calculate the total area A1 enclosed by the design fire net heat flow curve and the time axis, A1 = Q1 / A;

[0028] Divide the time axis into several time points of unit length, and calculate the total area A2 enclosed by the standard fire net heat flow curve and the time axis at these time points based on the standard fire total heat Q2. A2 = Q2 / A.

[0029] During the calculation process, the time point is continuously adjusted until the total area A2 enclosed by the standard fire net heat flow curve is equal to the total area A1 enclosed by the design fire net heat flow curve. This time point is the standard fire exposure time value.

[0030] The present invention also provides a method for assessing the degree of damage to wooden components, which assesses the degree of damage to wooden components caused by an actual fire based on the standard fire exposure time value obtained by the fire intensity quantification method based on energy equivalence.

[0031] The present invention also provides a fire safety design method for wooden components, which uses the standard fire exposure time value obtained by the fire intensity quantification method based on energy equivalence to carry out fire safety design of wooden structures under actual fire action.

[0032] The present invention also provides an electronic device, including a processor and a memory, wherein the memory stores a computer program, and the processor is used to run the computer program in the memory to execute the energy equivalence-based fire intensity quantification method, the wood component damage assessment method, or the component fire safety design method.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] The energy equivalence-based fire intensity quantification method provided by this invention is of great significance. It overcomes the shortcomings of existing fire protection design methods, offering new possibilities for the development of modern timber structures. This method fills the gaps in current standards for assessing the fire resistance performance of timber structures under actual fire conditions, achieving standardization of fire resistance design under real fire conditions. It is expected to break through the development limitations of traditional design methods, thereby promoting the development of green buildings, especially building types represented by modern timber structures, and providing strong support for sustainable social development. The innovation of this invention lies in the first-time combination of energy equivalence with the fire resistance performance of structures, proposing a completely new method for assessing the fire resistance performance of timber structures under actual fire conditions. Within the basic fire safety design framework, this method utilizes the energy equivalence principle to transform various real-world fire designs into standard fire designs. Simultaneously, in terms of prescriptive fire protection design and performance-based fire protection design, it helps to advance fire protection design methods and promote the development of timber structures towards higher levels and larger spaces. In summary, the contribution of this invention lies not only in solving existing problems in the fire resistance performance assessment of timber structures but also in providing a leading method for the future development of timber structures. Through innovative concepts and methods, it will play an important role in the field of modern architecture and make a positive contribution to the goal of green building. Attached Figure Description

[0035] Figure 1 Mathematical descriptions of four types of actual fire models: (a) EN fire model, (b) iBMB fire model, (c) iTFM fire model, and (d) LTFM fire model.

[0036] Figure 2 Temperature-time curves for four types of real-world fire scenarios: (a) EN fire model, (b) iBMB fire model, (c) iTFM fire model, and (d) LTFM fire model.

[0037] Figure 3 This is a schematic diagram of wood pyrolysis.

[0038] Figure 4 Conceptual diagrams of energy equivalence for design fires and standard fires;

[0039] Figure 5 For structural space layout and dimensions;

[0040] Figure 6 The relationship between equivalent time and location under different fire scales;

[0041] Figure 7 Box plots comparing equivalent times for different fire scales. Detailed Implementation

[0042] The present invention will be further described below with reference to specific embodiments.

[0043] Example 1

[0044] This embodiment provides a method for quantifying fire intensity based on energy equivalence, including the following steps:

[0045] Step 1: Establish a model of the actual fire temperature field within the space of a wooden building;

[0046] Step 2: Determine the temperature-time curve under the actual fire scenario using the actual fire temperature field model from Step 1;

[0047] Step 3: Calculate the total heat Q1 introduced into the wooden components using the actual fire temperature-time curve from Step 2;

[0048] Step 4: Calculate the total heat Q2 introduced into the wooden components under different fire exposure times under standard fire conditions;

[0049] Step 5: By setting Q1 = Q2, calculate the standard fire exposure time value that is equivalent to the actual fire intensity, i.e., the equivalent time value;

[0050] Step 6: Use the equivalent time value obtained in Step 5 to assess the extent of damage to the wooden components caused by the actual fire.

[0051] Step 1 is as follows:

[0052] A series of empirical models have been proposed to describe the temperature field within a compartment under real fire conditions. Typical fire models include: the European standard EN 1991-1-2 parametric fire model (referred to as the EN parametric fire model), the German standard DIN EN1991-1-2 parametric fire model (referred to as the iBMB parametric fire model), the iTFM fire spread model, and the LTFM fire spread model for tall, open-air buildings. Figure 1 As shown, the four types of fire models basically cover the description of the actual fire temperature field of medium, large, and tall structures, and can realistically reflect the temperature field distribution characteristics of various spatial structures under actual fire conditions.

[0053] Step 2 is as follows:

[0054] The temperature-time curve of an EN (Enhanced Environment) fire is defined by the following key parameters: fire load density q. d Opening factor O, wall thermal inertia b, fire growth rate t lim The time t corresponding to the highest temperature max Total time t total By changing the above parameter values, temperature-time curves for different fire scenarios can be obtained, such as... Figure 2 As shown in (a).

[0055] The temperature-time curve of an iBMB fire is defined by the following factors: fire load density q. d Opening factor O, wall thermal inertia b, termination time / temperature t1 / θ1 of the growth stage, termination time / temperature t2 / θ2 of the fully developed stage, total time t total By changing the above parameter values, temperature-time curves for different fire scenarios can be obtained, such as... Figure 2 As shown in (b).

[0056] iTFM (In-Fluid Tolerancing) fire scenarios are primarily influenced by fire size, which in turn is controlled by the fire spread rate. Therefore, the design of these scenarios mainly considers two key factors: fire spread rate and fire size. Temperature-time curves for different fire scenarios are obtained by varying the heating rate and isothermal time, as shown below. Figure 2 As shown in (c).

[0057] The LTFM (Long-Terminal Fire Response) fire scenario is primarily influenced by both fire scale and structural height. The design of LTFM fire scenarios mainly considers the impact of fire scale and structural height on the effectiveness of the energy equivalence method. Temperature-time curves for different fire scenarios are obtained by varying the fire scale and height, such as... Figure 2 As shown in (d).

[0058] Step 3 specifically involves:

[0059] External heat transfers heat to the wood surface through convection and radiation, and then heat from the wood surface is transferred to the interior of the wood through thermal conduction, such as... Figure 3 As shown, the relationship between the net heat flux, convective heat flux, and radiative heat flux of wood is as follows:

[0060] q net =q conv +q radi (1)

[0061] In the formula, q net Net heat flux density (W / m 2 ), q conv Convection heat flux density (W / m³) 2 ), q radi Radiative heat flux density (W / m 2 ).

[0062] The convective heat flux density and radiative heat flux density of wooden components can be described by the following two formulas:

[0063] q conv =h conv (T f -T s (2)

[0064]

[0065] In the formula, h conv Convection coefficient (W / m) 2 K), σ is the Boltzmann constant (W / m) 2 K 4 ), ε is the emissivity, T f T represents the flame temperature (K). s The temperature of the wood boundary surface (K).

[0066] Therefore, the net heat transferred into the interior of a wooden component under fire exposure can be expressed by the following formula:

[0067]

[0068] Substituting equations (2) and (3) into equation (4), we can obtain the total heat Q1 introduced into the wooden component under actual fire temperature-time exposure:

[0069]

[0070] In the formula, A is the surface area exposed to fire, and h conv σ is the convection coefficient, σ is the Boltzmann constant, ε is the emissivity, and T is the emissivity. f.actual T represents the actual fire temperature. s.actual t represents the surface temperature of the wood boundary under the actual fire, t0 represents the initial time, and t represents the actual duration of the fire.

[0071] Therefore, the total net heat transferred into the wood through heat conduction over a period of time can be measured by the actual flame temperature T. f.actual and the surface temperature T of the side of the wood exposed to fire s,actual Calculated.

[0072] The surface temperature T of the wood on the side exposed to fire under actual fire conditions s,actual The calculation method is as follows:

[0073] Assuming the wood is a one-dimensional, impermeable, semi-infinite board, its surface absorbs all non-reflective incident heat, and heat is transferred into the wood solely through thermal conduction. The evolution of the temperature gradient across the wood cross-section can be described by the following energy conservation equation:

[0074]

[0075] In the formula, T is the cross-sectional temperature (K), t is the time (s), and ρ is the density (kg / m³). 3 ), k is the thermal conductivity (W / m·K), c is the specific heat (J / kg K), Q" gene Energy generated by pyrolysis (kW / m³) 3), where x is the cross-sectional position (mm).

[0076] Ignoring volume changes, the effect of moisture content on density is described as follows:

[0077] ρ=(1+0.01MC)ρ0 (7)

[0078] Referring to the relationship between temperature and thermal conductivity given by Wenzl and Alves:

[0079]

[0080] Referring to the relationship between temperature and specific heat given by Wenzl and Perry:

[0081]

[0082] Relative temperature is expressed as:

[0083] θ=T-T0 (10)

[0084] Therefore, the energy conservation equation can be written as:

[0085]

[0086] Considering the radiative and convective heat loss from the fire-affected surface to the environment, the initial and boundary conditions are as follows:

[0087]

[0088] In equation (12), the radiation heat transfer coefficient h R The relation is described as:

[0089]

[0090] Due to the surface temperature T on the side exposed to fire s Approximate flame temperature T f Therefore, the radiation heat transfer coefficient can be approximately described as:

[0091]

[0092] In h R In the approximate case, the analytical solutions to equations (11) and (12) are obtained by Laplace transform:

[0093]

[0094] In the formula, τ is the heat loss coefficient of the wood surface.

[0095] Therefore, when x = 0, the formula for calculating the surface temperature of the side of the wood exposed to fire can be obtained:

[0096]

[0097] Here, erfc(τ) is an error compensation function. As τ approaches 0, The approximate expansion can be expressed as:

[0098]

[0099] Substituting equation (17) into equation (16), we can obtain the surface temperature function relationship considering the influence of surface heat loss:

[0100]

[0101] Combining equations (12), (16), and (18), the surface temperature of the wood on the fire-exposed side under actual fire conditions can be written as:

[0102]

[0103] In the formula, T0 is the ambient temperature, ρ is the wood density, k is the thermal conductivity of the wood, c is the specific heat of the wood, and h is the density of the wood. R Let q be the radiative heat transfer coefficient. ext.acture This represents the external radiative heat flux density under actual fire conditions.

[0104] Step 4 specifically involves:

[0105] The total heat Q2 introduced into a wooden component under exposure to a standard fire temperature-time curve can be expressed by the following formula:

[0106]

[0107] In the formula, A is the surface area exposed to fire, and h conv σ is the convection coefficient, σ is the Boltzmann constant, ε is the emissivity, and T is the emissivity. f.atandard For standard fire temperature, T s.stamdard t represents the boundary surface temperature of wood under standard fire conditions. i This refers to the standard fire duration.

[0108] Therefore, the total net heat transferred into the wood through heat conduction over a period of time can be measured by the standard flame temperature T. f.standard and the surface temperature T of the side of the wood exposed to fire s,standard Calculated.

[0109] Surface temperature T on the fire-exposed side under standard fire conditions s,standard The calculation method is as follows:

[0110]

[0111] In the formula, T0 is the ambient temperature, ρ is the wood density, k is the thermal conductivity of the wood, c is the specific heat of the wood, and h is the density of the wood. R Let q be the radiative heat transfer coefficient. ext.standard This represents the external radiative heat flux density.

[0112] Step 5 specifically involves:

[0113] The calculation of equivalent time follows the energy equivalence method, and its steps are as follows: According to this method, the areas enclosed by the net heat flux curves of the design fire and the standard fire and the time axis are equal, thus obtaining the standard fire exposure time that transfers the same amount of heat into the wood as the design fire exposure, i.e., the equivalent time. Figure 4 As shown.

[0114] 1) First, calculate the total area enclosed by the design fire net heat flow curve and the time axis, and label it A1.

[0115] 2) Divide the time axis into several time points of unit length, and calculate the total area enclosed by the standard fire net heat flux curve and the time axis at each of these time points, and mark it as A2.

[0116] 3) During the calculation process, the time points are continuously adjusted until the total area A2 enclosed by the standard fire net heat flux curve and the design fire net heat flux curve equals A1. At this point, the corresponding standard fire time is the equivalent time.

[0117] Example 2

[0118] This embodiment provides a method for assessing the degree of damage to wooden components. Based on the standard fire exposure time value obtained by the fire intensity quantification method based on energy equivalence provided in Embodiment 1, the method assesses the degree of damage to wooden components caused by an actual fire.

[0119] The specific steps of the damage assessment method are as follows:

[0120] The fire resistance performance assessment of a TCC beam-slab structure under iTFM fire conditions will be used as an example. First, sampling points are set at 1m intervals along the ceiling of the intermediate floor of a 3-story TCC frame, such as... Figure 5As shown in the figure. Based on the iTFM fire model, temperature-time curves for each sampling point under all fire scenarios were calculated, and the equivalent exposure time value of each sampling point under standard fire conditions was calculated using a simplified energy equivalence method. Existing experimental studies have shown that the temperature distribution of the wood pyrolysis layer under iTFM fire and standard fire exposure is approximately equivalent. This means that the magnitude of the equivalent time value of each spatial sampling point can indirectly reflect the carbonization depth at that point, and further reflect the degree of damage at that point under iTFM fire. Therefore, the damage degree of iTFM fire to wooden beams at different locations in TCC beam-slab structures is mainly illustrated by comparing the magnitude of the equivalent time values ​​of each sampling point. By comparing the equivalent time values, the carbonization depth and damage degree of wooden beams at different locations can be obtained, providing a deeper understanding of the impact of fire on the structure and offering important references for improving and optimizing fire protection design, thereby promoting the safety performance and sustainable development of wooden structures.

[0121] Using the simplified energy equivalence method, the standard fire exposure equivalent time values ​​of each sampling point at the fire floor ceiling of the TCC frame are calculated for all fire scenarios. Figure 6 This demonstrates the relationship between the equivalent time values ​​and spatial locations of each sampling point at the fire-prone ceiling of the TCC frame under all fire scenarios. Through analysis of... Figure 6 Analysis reveals that under iTFM fire conditions, despite the mere 1m interval between sampling points on the ceiling, their equivalent time values ​​exhibit significant differences. This is particularly evident in small fires with a scale of 10%–30%, where the difference in equivalent time values ​​between the ends and the middle of the structure is even more pronounced. This indicates that under iTFM fire conditions, the fire intensity varies among sampling points on the TCC frame ceiling, meaning the degree of damage differs at each sampling point. Specifically, as the fire scale decreases (e.g., 10%–30%), the differences in damage degree (or char depth) at various points on the structural ceiling become more pronounced. Conversely, as the fire scale increases (e.g., 35%–70%), the consistency of damage degree gradually strengthens. This comparative result strongly suggests that the assumption of uniformity of the temperature field within a large spatial structure susceptible to iTFM fires is unsound. The differences in fire intensity observed at sampling points at different locations further underscore the necessity of using the energy equivalence method for fire resistance performance assessment. This assessment will help to understand more accurately the structural response in different locations under fire conditions, providing an important reference for targeted fire protection design.

[0122] Example 3

[0123] This embodiment provides a fire safety design method for timber components. Based on the standard fire exposure time value obtained from the fire intensity quantification method based on energy equivalence in Embodiment 1, the fire safety design of timber structures under actual fire action is performed. The specific steps of the fire safety design method for timber components are as follows:

[0124] Standard fire design and performance-based fire protection design differ significantly in the fire protection design of timber-framed buildings. Standard fire design is based on the temperature-time curve of a standard fire and assumes uniform temperature distribution within compartments; performance-based design, on the other hand, considers real-world fire scenarios, including the impact of non-uniform temperature distribution on the structure. A key difference between standard fire design and iTFM fire design lies in the variation of fire intensity at different locations within the structure. Under iTFM fire conditions, the fire intensity varies at different locations. Existing research has also found that iTFM fires cause more severe structural damage than standard fires because the variation in fire intensity at different locations can lead to a more severe structural response. Furthermore, standard fire designs lack a cooling phase, thus failing to adequately account for the most unfavorable fire conditions. Based on existing experimental data, fire case studies, and the aforementioned analysis, it can be concluded that relying solely on standard fire design is insufficient, especially for large-span structures susceptible to iTFM fires. Therefore, performance-based fire protection design must comprehensively consider real-world fire conditions, including factors such as non-uniform temperature distribution, to ensure that the fire resistance of timber-framed buildings is adequately guaranteed in actual fire conditions.

[0125] Figure 7 Box plots comparing the equivalent time values ​​of all sampling points under different fire scales are presented. Figure 7 The analysis leads to the following conclusions: Under fire scales of 10% and 45%–70%, the equivalent time values ​​at each sampling point on the ceiling exhibit relatively small dispersion and a concentrated distribution. However, under moderate fire scales of 15%–40%, the equivalent time values ​​at each sampling point show greater dispersion and a more dispersed distribution. This result indicates that when the fire scale is 10% and 45%–70%, except for a few points, the fire intensity at each sampling point on the structural ceiling is basically consistent, and the temperature field distribution is relatively uniform. Therefore, under these fire scales, the temperature field of the structural space can be approximated as uniform, thus allowing for standard fire design. In this case, iTFM fire design can serve as an auxiliary design to verify the structural safety. Conversely, under moderate fire scales of 15%–40%, the equivalent time values ​​at each sampling point differ significantly, indicating a substantial difference in fire intensity at the structural ceiling. Therefore, in this situation, the structure needs to primarily employ iTFM fire design to more accurately consider the fire impact at different locations. Standard fire design can serve as a supplement to provide additional safety assurance.

[0126] In summary, the scale of a fire affects the distribution of fire intensity at various sampling points on the structural ceiling. For smaller and larger fires, standard fire design can be used, while for medium-sized fires, iTFM fire design should be the primary approach, supplemented by standard fire design, to ensure the structure's fire resistance under different fire conditions.

[0127] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

[0128] Example 4

[0129] This embodiment provides an electronic device, including a processor and a memory. The memory stores a computer program, and the processor is used to run the computer program in the memory to execute the fire intensity quantification method based on energy equivalence provided in Embodiment 1, the damage assessment method for wooden components provided in Embodiment 2, or the fire safety design method for components provided in Embodiment 3.

Claims

1. A method for quantifying fire intensity based on energy equivalence, characterized in that, Includes the following steps: Establish a model of the actual fire temperature field within the space of a timber-structured building; Based on the established actual fire temperature field model, the temperature-time curves under actual fire scenarios are obtained; Based on the temperature-time curves obtained from actual fire scenarios, calculate the actual total heat generated by introducing wooden components in the actual fire scenario. Q 1; Calculate the total standard fire heat transferred to wooden components under different fire exposure times under standard fire conditions. Q 2; Based on the actual total heat of the fire Q 1. Total heat capacity of a standard fire Q 2. Obtain the standard fire exposure time value that is equivalent to the actual fire intensity; The actual fire intensity is determined based on the obtained standard fire exposure time value; Based on the temperature-time curves obtained in the actual fire scenario, the actual total heat generated by introducing wooden components in the actual fire scenario was calculated. Q 1 is: In the formula, A For the surface area exposed to fire, h conv The convection coefficient, σ Boltzmann's constant, ε For emission rate, T f.actual This represents the actual fire temperature. T s.actual This refers to the surface temperature of the wood boundary under actual fire conditions. t 0 The initial time, t This refers to the actual duration of the fire. Wood boundary surface temperature under actual fire T s.actual for: In the formula, T 0 For ambient temperature, ρ For wood density, k The thermal conductivity of wood, c For the specific heat of wood, h R The radiative heat transfer coefficient is... q " ext.acture This represents the external radiative heat flux density under actual fire conditions. Calculate the total standard fire heat transferred to wooden components under different fire exposure times under standard fire conditions. Q 2 is: In the formula, A For the surface area exposed to fire, h conv For convection coefficient, σ Boltzmann's constant, ε For emission rate, T f.atandard Standard fire temperature T s.stamdard The boundary surface temperature of wood under standard fire conditions. t i Standard fire duration; Wood boundary surface temperature under standard fire conditions T s.standard for: In the formula, T 0 For ambient temperature, ρ For wood density, k The thermal conductivity of wood, c For the specific heat of wood, h R The radiative heat transfer coefficient is... q " ext.standard This represents the external radiative heat flux density under standard fire conditions.

2. The fire intensity quantification method based on energy equivalence according to claim 1, characterized in that, Based on the actual total heat of the fire Q 1. Total heat capacity of a standard fire Q 2. The method for obtaining a standard fire exposure time value equivalent to the actual fire intensity is through the actual total heat of the fire. Q 1. Total heat capacity of a standard fire Q 2. Equal to obtain the standard fire exposure time value that is equivalent to the actual fire intensity.

3. The fire intensity quantification method based on energy equivalence according to claim 2, characterized in that, Based on the actual total heat of the fire Q 1. Total heat capacity of a standard fire Q 2. Methods for obtaining standard fire exposure time values ​​equivalent to actual fire intensity, including: Based on the actual total heat of the fire Q 1. Calculate the total area A1 enclosed by the net heat flux curve of the design fire and the time axis, A1 = Q 1 / A; Divide the time axis into several time points of unit length, based on the standard total heat of a fire. Q 2. Calculate the total area A2 enclosed by the standard fire net heat flux curves and the time axis at these time points, where A2 = Q 2 / A; During the calculation process, the time point is continuously adjusted until the total area A2 enclosed by the standard fire net heat flow curve is equal to the total area A1 enclosed by the design fire net heat flow curve. This time point is the standard fire exposure time value.

4. A method for assessing the degree of damage to wooden components, characterized in that, The degree of damage to wooden components caused by an actual fire is assessed based on the standard fire exposure time value obtained by the fire intensity quantification method based on energy equivalence as described in any one of claims 1-3.

5. A fire safety design method for wooden components, characterized in that, Based on the standard fire exposure time value obtained by the fire intensity quantification method based on energy equivalence as described in any one of claims 1-3, fire safety design of wooden structures under actual fire action is carried out.

6. An electronic device, characterized in that, The device includes a processor and a memory, the memory storing a computer program, and the processor running the computer program in the memory to execute the fire intensity quantification method based on energy equivalence as described in any one of claims 1 to 3, the method for assessing the degree of damage to wooden components as described in claim 4, or the fire safety design method for wooden components as described in claim 5.

Images