Fireproof design method of fireproof and decorative integrated steel beam and steel beam

Abstract

This invention relates to the field of fire protection technology for building steel structures, specifically providing a fire-resistant design method and steel beam for integrated fireproof and decorative steel beams, including the following steps: obtaining the fire-resistant design parameters of the steel beam; calculating the critical temperature T of the steel beam. c And in designing the fire resistance limit t m The highest temperature inside T s,max Determine whether the steel beam meets the fire protection design requirements; if not, design an integrated fire-resistant and decorative structure; calculate the maximum temperature T of the steel beam. ps,max And in designing the fire resistance limit t m The highest temperature inside T ps,max The method determines whether the integrated fire-resistant and decorative structure in the steel beam meets the fire protection design requirements. If not, the thickness and / or material of the integrated fire-resistant and decorative structure are changed until it meets the fire protection design requirements. The integrated fire-resistant and decorative steel beam includes both the steel beam and the integrated fire-resistant and decorative structure. This invention is based on the critical temperature method and offers higher accuracy and simpler, faster calculations.

Description

Technical Field

[0001] This invention belongs to the field of fire protection technology for building steel structures, specifically relating to a fireproof design method for integrated fireproof and decorative steel beams and the steel beams themselves. Background Technology

[0002] Steel structures have gained industry attention due to their excellent seismic performance, rapid construction, and environmental sustainability, and their proportion in my country's modern building structure system is increasing daily. However, steel structures also have a significant drawback: poor fire resistance. At high temperatures, the internal crystal structure of steel changes, causing a decrease in its yield strength and elastic modulus, leading to a substantial reduction in the load-bearing capacity and stability of the components. The critical temperature of commonly used building steel is around 540℃, while the temperature in building fires is mostly between 800-1200℃. Under such high-temperature conditions, steel components without any protective measures will quickly undergo plastic deformation. According to the test results of the standard time temperature rise curve, the fire resistance limit of exposed steel components is only 0.25 hours.

[0003] To provide reliable fire protection for steel structures and extend their fire resistance time, the "Technical Specification for Fire Protection of Steel Structures" GB51249-2017 (hereinafter referred to as the "Specification") has provided some fire-resistant construction methods, such as protection with non-intumescent fire-retardant coatings, protection with fire-resistant boards, protection with external concrete, and composite protection with fire-retardant coatings and fire-resistant boards. However, some of these measures for steel beams still have many problems and drawbacks. For example, the construction of external concrete is cumbersome and requires curing; fire-resistant board cladding cannot solve the problem of filling the internal space of the flange of H-shaped steel beams; intumescent fire-retardant coatings have insufficient durability; and non-intumescent fire-retardant coatings are rough and loose, and cannot meet the decorative requirements.

[0004] To address the shortcomings of the aforementioned fire-resistant construction methods, a fire-resistant and decorative integrated construction method has emerged, which involves encasing steel beams with materials such as aerated concrete blocks and adding fire-retardant coatings and finishing mortar. A series of experimental studies and numerical simulations have proven its effectiveness. However, the fire-resistant design methods currently provided in the relevant codes are not applicable to steel beams using this fire-resistant and decorative integrated construction method. The code's design method assumes a uniform temperature distribution across the entire component cross-section. In reality, because the web of the steel beam in the fire-resistant and decorative integrated construction method is filled with blocks on both sides, and steel beams are often exposed to fire on three sides in a fire, the temperature distribution should gradually decrease from bottom to top, contradicting the assumption in the code. Furthermore, the code does not provide corresponding formulas for calculating or correcting the temperature of steel components. Under limited conditions, accurately obtaining the maximum temperature of the steel beam can only be achieved through numerical simulation, which is cumbersome, inefficient, and requires significant learning and time investment, making it inconvenient for designers. In conclusion, the lack of research in related fields and the absence of relevant standards have brought certain difficulties to the fireproof design of steel beams with integrated fireproof and decorative structures. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a fireproof design method for fireproof and decorative integrated steel beams and the steel beam itself.

[0006] In a first aspect, the present invention proposes a fireproof design method for an integrated fireproof and decorative steel beam, comprising the following steps:

[0007] Step 1: Obtain the fire protection design parameters for the steel beams;

[0008] Step 2: Obtain the design fire resistance rating t of the steel beam without any fire protection measures. m The highest temperature inside T s,max ;

[0009] Step 3: Based on the fire protection design parameters of the steel beam, determine the critical temperature T of the steel beam without fire protection measures. c ;

[0010] Step 4: Based on the highest temperature T of the steel beam under conditions where no fire protection measures are installed. s,max and critical temperature T c Determine whether the steel beam meets the fire protection design requirements. If it does, the steel beam will not be equipped with an integrated fire protection and decoration structure. If it does not meet the fire protection design requirements, an integrated fire protection and decoration structure will be designed according to the fire resistance rating of the steel beam that requires fire protection design.

[0011] Step 5: Based on the performance parameters of the integrated fireproof and decorative structure, obtain the design fire resistance limit t of the steel beam when fire protection measures are in place. m The highest temperature inside T ps,max ;

[0012] Step 6: Based on the highest temperature T of the steel beam under fire protection measures, ps,max and critical temperature T c To determine whether the integrated fireproof and decorative structure in the steel beam meets the fire protection design requirements, if it does not meet the fire protection design requirements, the thickness and / or material of the integrated fireproof and decorative structure is changed, and the process returns to step 5 until the integrated fireproof and decorative structure meets the fire protection design requirements.

[0013] Furthermore, in step 5, if fire protection measures are in place, the steel beam will meet the design fire resistance limit t. m The highest temperature inside T ps,max Obtained through iterative processing, the iterative processing steps include:

[0014] Step 5.1: Use the steel beam temperature T at time t ps The temperature rise ΔT of the steel beam within a time step Δt is obtained. ps ;

[0015] Step 5.2: Calculate the temperature T of the steel beam at time t+Δt. ps Updated to the steel beam temperature T at time t. ps With temperature rise ΔT ps sum;

[0016] Step 5.3: Repeat steps 5.1 and 5.2 above to check the temperature T of the steel beam. ps Iterative processing was performed to obtain the steel beam temperature T at different times. ps And will design fire resistance limit t m The highest temperature of the steel beam inside is T ps As a steel beam, its fire resistance rating is designed to be [t]. m The highest temperature inside T ps,max .

[0017] Furthermore, in step 5, if fire protection measures are in place, the steel beam will meet the design fire resistance limit t. m The highest temperature inside T ps,max The following formula is used for iterative processing to obtain:

[0018]

[0019]

[0020] Where, ΔT psThis represents the temperature rise of the steel beam within (t, t+Δt) under fire protection conditions; Δt represents the time step; α i F represents the overall heat transfer coefficient of the steel beam. i ρ represents the fire-exposed surface area per unit length of the steel beam; V represents the volume per unit length of the steel beam; k represents the parameter indicating the delaying effect of the web filling material of the steel beam on the temperature rise of the lower flange; s and c s T represents the density and specific heat of steel, respectively; g T represents the average temperature of the hot flue gas at time t; ps This indicates the temperature of the lower flange of the steel beam at time t, assuming fire protection measures are in place.

[0021] In the above formula, t f α1, α2, and α3 represent the thickness and width of the steel beam flange, respectively; α1, α2, and α3 represent the combined heat transfer coefficients of the lower, left, and right sides of the steel beam flange, respectively; λ1, λ2, and λ3 represent the equivalent heat transfer coefficients of the materials used in the fireproof and decorative integrated structure of the lower, left, and right sides of the steel beam flange, respectively; and d1, d2, and d3 represent the thickness of the fireproof and decorative integrated structure of the lower, left, and right sides of the steel beam flange, respectively.

[0022] Furthermore, in step 2, without fire protection measures, the steel beam meets the design fire resistance limit t. m The highest temperature inside T s,max Obtained through iterative processing, the iterative processing steps include:

[0023] Step 2.1: Use the steel beam temperature T at time t s The temperature rise ΔT of the steel beam within a time step Δt is obtained. s ;

[0024] Step 2.2: Calculate the temperature T of the steel beam at time t+Δt. s Updated to the steel beam temperature T at time t. s With temperature rise ΔT s sum;

[0025] Step 2.3: Repeat steps 2.1 and 2.2 above to check the temperature T of the steel beam. s Iterative processing was performed to obtain the steel beam temperature T at different times. s And will design fire resistance limit t m The highest temperature of the steel beam inside is T s As a steel beam, its fire resistance rating is designed to be [t]. m The highest temperature inside T s,max .

[0026] Furthermore, in step 2, without fire protection measures, the steel beam's design fire resistance rating t...m The highest temperature inside T s,max The following formula is used for iterative processing to obtain:

[0027]

[0028] α=α c +α r

[0029]

[0030] In the formula, ΔT s This represents the temperature rise of the steel beam within (t, t+Δt) without fire protection measures; Δt represents the time step; α represents the overall heat transfer coefficient of the steel beam; α c α represents the heat transfer coefficient by heat convection; r ρ represents the thermal radiation heat transfer coefficient; s and c s These represent the density and specific heat of steel, respectively; F represents the surface area of ​​the steel beam exposed to fire per unit length; V represents the volume of the steel beam per unit length; T g T represents the average temperature of the hot flue gas at time t; s ε represents the internal temperature of the steel beam at time t without any fire protection measures; r σ represents the overall emissivity; σ represents the Stefan-Boltzmann constant.

[0031] Furthermore, in step 4, based on the highest temperature T of the steel beam under the condition of no fire protection measures, s,max and critical temperature T c The steps for determining whether the steel beam meets the fire protection design requirements include:

[0032] If the critical temperature T of the steel beam c ≥ The highest temperature of the steel beam T s,max This indicates that the steel beam meets the fire protection design requirements, and the steel beam no longer needs to be equipped with an integrated fireproof and decorative structure;

[0033] If the critical temperature T of the steel beam c The highest temperature of the steel beam T s,max If the result is negative, it indicates that the steel beam does not meet the fire protection design requirements.

[0034] Furthermore, in step 6, based on the highest temperature T of the steel beam under the condition of fire protection measures, ps,max and critical temperature T c The steps to determine whether the integrated fireproof and decorative structure in the steel beam meets the fire protection design requirements include:

[0035] If the critical temperature T of the steel beam c ≥ The highest temperature of the steel beam T ps,maxThis indicates that the steel beam meets the fire protection design requirements;

[0036] If the critical temperature T of the steel beam c The highest temperature of the steel beam T ps,max If the result is negative, it indicates that the steel beam does not meet the fire protection design requirements.

[0037] Furthermore, the fire protection design parameters of the steel beam in step 1 include the design fire resistance rating and the design fire resistance limit t. m Section strength load ratio R, component stability load ratio R', and stability coefficient of steel beam at room temperature. And the air temperature rise curve.

[0038] Furthermore,

[0039] The section strength load ratio R is obtained according to the following formula:

[0040] M u =γW n f

[0041] In the formula, R represents the cross-sectional strength load ratio of the steel beam under fire conditions; M represents the maximum design bending moment of the steel beam under fire conditions; M u γ represents the flexural capacity of the steel beam at room temperature; γ represents the plastic development coefficient of the steel beam section; W n represents the net section modulus of the most unfavorable section of the steel beam; f represents the yield strength of the steel at room temperature;

[0042] The component stability load ratio R' of the steel beam is obtained according to the following formula:

[0043]

[0044] In the formula, R' represents the component stability load ratio of the steel beam under fire conditions; M su This indicates the overall stable bearing capacity of the steel beam at room temperature; β represents the stability coefficient of the steel beam at room temperature; W represents the gross section modulus of the steel beam; b The equivalent bending moment coefficient representing the overall stability of the steel beam; λ y η represents the slenderness ratio of the steel beam about the weak axis yy between the lateral support points; A represents the gross cross-sectional area of ​​the steel beam; h represents the total height of the steel beam cross-section; t1 represents the thickness of the compression flange of the steel beam; η b ε represents the influence coefficient of asymmetry in the steel beam section; k Indicates the steel grade correction factor; l1 represents the distance between the lateral support points of the compression flange of the steel beam; i y This represents the radius of gyration of the gross section of the steel beam about the weak axis, y-axis.

[0045] The expression for the air temperature rise curve of the steel beam is as follows:

[0046] T g =345lots 10 (8t+1)+T0

[0047] In the formula, T g T represents the average temperature of the hot smoke at time t; t represents the duration of the fire; T0 represents the temperature of the indoor environment before the fire.

[0048] Secondly, the present invention also proposes a fireproof and decorative integrated steel beam, designed using the above-mentioned method. The fireproof and decorative integrated steel beam includes a steel beam and a fireproof and decorative integrated structure. The fireproof and decorative integrated structure includes aerated concrete blocks and / or fine stone concrete filled on both sides of the steel beam. The fireproof and decorative integrated structure also includes plastering mortar and / or non-expansive fireproof coating applied to the bottom of the beam.

[0049] The beneficial effects of this invention are:

[0050] 1. A simplified calculation method is provided for the cross-sectional temperature field of a fire-resistant and decorative integrated steel beam when it is exposed to fire on three sides. Currently, the relevant temperature calculation formula is not provided in the standard. To accurately obtain the temperature of the steel beam after the fire-resistant structure is installed, the only way is through a cumbersome and inefficient numerical simulation method, which requires a large investment of learning and time and is inconvenient to use.

[0051] 2. The non-uniformity of temperature distribution in the steel beam section after adopting the integrated fireproof and decorative structure is taken into account, making the calculation results more realistic and accurate. In contrast, the design method in the "Code" assumes that the temperature of the entire component section is uniformly distributed.

[0052] 3. The calculation method proposed in this invention takes into account the fire protection effect of various lightweight and non-lightweight materials at the same time. Compared with the "Specification" which requires separate consideration of lightweight and non-lightweight materials when calculating the temperature of steel components, this method has a more diversified range of materials and a wider range of applications.

[0053] 4. Compared with other protection measures such as non-intumescent fire-retardant coatings, fire-retardant board coverings, concrete cladding, and composite protection of fire-retardant coatings and fire-retardant boards, the integrated fire-retardant and decorative structure solves some of the pain points. While ensuring good fire protection, it also meets the requirements of building decoration, and is convenient to construct, cost-effective, and environmentally friendly.

[0054] 5. This invention can be widely applied to the fire protection design of various steel structure buildings using fire-resistant and decorative integrated steel beams, and provides technical support and reliable assurance for the promotion of this structure in engineering. This invention first provides a simplified calculation formula for the maximum temperature of the cross-section of the fire-resistant and decorative integrated steel beam. Then, based on the critical temperature method, it proposes a fire protection design and fire resistance verification method for the fire-resistant and decorative integrated steel beam. This method is basically consistent with the numerical analysis results and has strong applicability. Attached Figure Description

[0055] Figure 1 This is a schematic flowchart of the method of the present invention;

[0056] Figure 2 This is a structural schematic diagram of one embodiment of the fireproof and decorative integrated steel beam of the present invention;

[0057] Figure 3 This is a schematic diagram of another embodiment of the fireproof and decorative integrated steel beam of the present invention;

[0058] Figure 4 This is a structural schematic diagram of another embodiment of the fireproof and decorative integrated steel beam of the present invention;

[0059] Figure 5 This is a structural schematic diagram of another embodiment of the fireproof and decorative integrated steel beam of the present invention;

[0060] Figure 6 This is a structural schematic diagram of another embodiment of the fireproof and decorative integrated steel beam of the present invention.

[0061] In the diagram: 1-Surface mortar; 2-Non-expansive fireproof coating; 3-H-beam; 4-Masonry mortar; 5-Aerated concrete block; 6-Saddle nail; 7-C-type hot-dip galvanized steel wire mesh; 8-Fine aggregate concrete; 9-Reinforcing steel. Detailed Implementation

[0062] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0063] Example 1

[0064] like Figure 2 As shown, the fireproof and decorative integrated steel beam proposed in this invention includes an H-beam 3 with a cross-sectional shape of H300×100×6×10, and an integrated fireproof and decorative structure composed of fireproof filling material. The overall beam width is 200mm, and the bottom of the beam is coated with a non-expansive fireproof coating 2 with a coating thickness of 20mm. Both sides of the H-beam 3 are filled with aerated concrete blocks 5 and coated with finishing mortar 1.

[0065] like Figure 1 As shown, the design method for fireproof and decorative integrated steel beams includes the following steps:

[0066] Step 1: Obtain the fire protection design parameters of the integrated fireproof and decorative steel beam; the fire protection design parameters of the steel beam include the design fire resistance rating and the design fire resistance limit t. m Section strength load ratio R, component stability load ratio R', and stability coefficient of steel beam at room temperature. The air temperature rise curve can also include steel performance parameters.

[0067] The section strength load ratio R is obtained according to the following formula:

[0068]

[0069] M u =γW n f

[0070] In the formula, R represents the cross-sectional strength load ratio of the steel beam under fire conditions; M represents the maximum design bending moment of the steel beam under fire conditions, in N·mm; M u γ represents the flexural capacity of the steel beam at room temperature, in N·mm; γ represents the plastic development coefficient of the steel beam section; W n This represents the net section modulus of the steel beam at its most unfavorable section, in mm. 3 ); f represents the yield strength of steel at room temperature, in N / mm². 2 );

[0071] The component stability load ratio R' of the steel beam is obtained according to the following formula:

[0072]

[0073] In the formula, R' represents the component stability load ratio of the steel beam under fire conditions; M su This indicates the overall stable bearing capacity of a steel beam at room temperature, expressed in N·mm. W represents the stability coefficient of the steel beam at room temperature; W represents the gross section modulus of the steel beam, in mm. 3 ); β b The equivalent bending moment coefficient representing the overall stability of the steel beam; λ y The slenderness ratio of the steel beam about the weak axis yy between the lateral support points is represented by A; A represents the gross cross-sectional area of ​​the steel beam, in mm². 2 h represents the total height of the steel beam section; t1 represents the thickness of the compression flange of the steel beam, in mm; η b η represents the influence coefficient of asymmetry in the steel beam section. For a doubly symmetric section, η b =0; ε k Indicates the steel grade correction factor; l1 represents the distance between the lateral support points of the compression flange of the steel beam, in mm; i y Represents the radius of gyration of the gross section of the steel beam about the weak axis y-axis, in mm.

[0074] The expression for the air temperature rise curve of the steel beam is as follows:

[0075] T g =345log 10 (8t+1)+T0

[0076] In the formula, T g T represents the average temperature of the hot smoke at time t, in °C; t represents the duration of the fire, in seconds; T0 represents the temperature of the indoor environment before the fire, in °C.

[0077] For common building indoor fires, the temperature rise can be calculated based on the above temperature rise curve. When there is reliable evidence to accurately determine the temperature change under actual fire conditions, the temperature rise can also be calculated based on the actual fire temperature rise curve.

[0078] In this embodiment, the section strength load ratio of the steel beam is R = 0.6, and the stability coefficient of the steel beam at room temperature is... The component's stability load ratio R' = 0.788.

[0079] Furthermore, according to the "Code for Fire Protection Design of Buildings" GB50016-2014, the fire resistance rating of the steel beam is determined to be Class 1, and the fire resistance limit is 2 hours; according to the "Technical Code for Fire Protection of Steel Structures" GB51249-2017, the various performance parameters of the steel are determined.

[0080] Step 2: Calculate the design fire resistance limit t of the steel beam without fire protection measures using the following formula. m The highest temperature inside T s,max :

[0081]

[0082] α=α c +α r

[0083]

[0084] In the formula, ΔT s α represents the temperature rise of the steel beam within (t, t+Δt) without fire protection measures, in °C; Δt represents the time step, in seconds, and should not exceed 5 seconds; α represents the overall heat transfer coefficient, in W / (m³). 2 ·℃)];α c This represents the heat transfer coefficient via convection, taken as 25 W / (m²). 2 ·℃); α r ρ represents the thermal radiation heat transfer coefficient, with units of [W / (m²·℃)]; s and c sThese represent the density and specific heat of steel, respectively; F represents the surface area of ​​the steel beam exposed to fire per unit length, in meters. 2 V represents the volume of a steel beam per unit length, in meters. 3 F / V represents the cross-sectional shape factor of the steel beam; T g T represents the average temperature of the hot flue gas at time t, in degrees Celsius (°C). s ε represents the internal temperature of the steel beam at time t without fire protection measures, in °C. r σ represents the overall emissivity, typically taken as 0.7; σ represents the Stefan-Boltzmann constant, typically taken as 5.67 × 10⁻⁸ W / (m²). 2 ·℃ 4 ).

[0085] The highest steel beam temperature T, calculated using the above formula, is obtained after 2 hours without fire protection measures. s It is 1048℃, or T s,max =1048℃;

[0086] Step 3: Based on the section strength load ratio R and the component stability load ratio R', calculate the critical temperature T of the steel beam without fire protection measures using the following formula. c .

[0087] T c =min(T) c1 ,T c2 )

[0088] Calculate T according to the section strength load ratio R using the following formula. c1 :

[0089] T c1 =755-390R 1.2

[0090] Calculate T according to the component's stability load ratio R' using the following formula. c2 :

[0091]

[0092] In the formula, Indicates the critical strength temperature; R represents the cross-sectional strength load ratio of the steel beam under fire conditions; R' represents the critical temperature for stability; R' represents the component stability load ratio of the steel beam under fire conditions. Indicates stable parameters; This represents the stability coefficient of a steel beam at room temperature, when φ b <0.6, take φ b =0.6, min() represents the minimum value function.

[0093] Based on the above calculation results, the critical temperature T of the steel beam without fire protection measures is determined. c The temperature is 457℃.

[0094] T s,max With T c By comparing, we obtain T. c ≤T s,max This indicates that steel beams without protective measures do not meet fire protection design requirements and that an integrated fireproof and decorative structure is needed for the steel beams.

[0095] Step 4: Determine the performance parameters of the fireproof coating, masonry mortar, plastering mortar, and autoclaved aerated concrete blocks for the integrated fireproof and decorative structure based on the type test report and instructions provided by the manufacturer.

[0096] Step 5: Based on the performance parameters of the integrated fireproof and decorative structure, such as... Figure 2 The diagram shows the addition of an integrated fire-resistant and decorative structure to the steel beam. Calculations and analyses of the steel beam are performed, and the design fire resistance limit t of the steel beam is obtained from the following formula. m The highest temperature inside T ps,max ;

[0097]

[0098] Where Δt represents the temperature rise of the steel beam within (t, t+Δt) under fire protection measures, in °C; Δt represents the time step; α i F represents the overall heat transfer coefficient of the steel beam. i ρ represents the fire-exposed surface area per unit length of the steel beam; V represents the volume per unit length of the steel beam; k represents the parameter indicating the delaying effect of the web filling material of the steel beam on the temperature rise of the lower flange; s and c s T represents the density and specific heat of steel, respectively; g T represents the average temperature of the hot flue gas at time t; ps This indicates the temperature of the lower flange of the steel beam at time t, with fire protection measures in place, in °C.

[0099] In the above formula, t f and b represent the thickness and width of the steel beam flange, respectively; F1 / V, F2 / V, and F3 / V represent the cross-sectional shape coefficients of the lower, left, and right sides of the lower flange, respectively; α1, α2, and α3 represent the comprehensive heat transfer coefficients of the lower, left, and right sides of the steel beam lower flange, respectively; λ1, λ2, and λ3 represent the equivalent heat transfer coefficients of the materials used in the fireproof and decorative integrated structure of the lower, left, and right sides of the steel beam lower flange, respectively; d1, d2, and d3 represent the thickness of the fireproof and decorative integrated structure of the lower, left, and right sides of the steel beam lower flange, respectively.

[0100] k = A'(b-200)2 +[0.0105(d1-30) 2 +2.55](t f -15) 2 +0.4(d1-30) 2 +85

[0101] A'=(20t f +4d1+930)×10 -5

[0102] In the formula, A' represents the delay coefficient.

[0103] The highest temperature T of the steel beam with integrated fireproof and decorative structure at 2 hours was calculated using the above formula. ps It is 428℃, that is, T ps,max =428℃;

[0104] The critical temperature T of the steel beam related to the load ratio R of the steel beam pc =T c =457℃.

[0105] Step 6: Place T ps,max With T pc By comparing, we obtain T. pc >T ps,max This indicates that the integrated fireproof and decorative structure meets the fireproof design requirements, and therefore the integrated fireproof and decorative structure can be used for fireproof design of steel beams.

[0106] Example 2

[0107] The fireproof and decorative integrated steel beam proposed in this invention includes an H-shaped steel beam 3 with a cross-sectional shape of H400×120×6×8, and an integrated fireproof and decorative structure composed of fireproof filling material. The overall beam width is 200mm, and the bottom of the beam is coated with a non-intumescent fireproof coating 2 with a coating thickness of 15mm.

[0108] The design method for the fireproof and decorative integrated steel beam in this embodiment includes the following steps:

[0109] Step 1: Obtain the fire protection design parameters of the integrated fireproof and decorative steel beam; the fire protection design parameters of the steel beam include the design fire resistance rating and the design fire resistance limit t. m Section strength load ratio R, component stability load ratio R', and stability coefficient of steel beam at room temperature. Steel performance parameters and air temperature rise curve; cross-sectional strength-to-load ratio R = 0.7 for the steel beam, and the stability coefficient φ of the steel beam at room temperature. b =0.75, component stability load ratio R' =0.98.

[0110] According to the "Code for Fire Protection Design of Buildings" GB50016-2014, the fire resistance rating of the steel beam is determined to be Class 2, and the fire resistance limit is 1.5h; according to the "Technical Code for Fire Protection of Steel Structures" GB51249-2017, the various performance parameters of the steel are determined; and the ISO standard temperature rise curve is obtained according to the following formula.

[0111] T g =345log 10 (8t+1)+T0

[0112] Step 2: Calculate the design fire resistance limit t of the steel beam without fire protection measures using the following formula. m The highest temperature inside T s,max :

[0113]

[0114] α=α c +α r

[0115]

[0116] The highest temperature T of the steel beam after 1.5 hours without fire protection measures is calculated using the above formula. s It is 1005℃, or T s,max =1005℃.

[0117] Step 3: Based on the section strength load ratio R and the component stability load ratio R', calculate the critical temperature T of the steel beam without fire protection measures using the following formula. c .

[0118] Calculate T according to the section strength load ratio R using the following formula. c1 :

[0119] T c1 =755-390R 1.2

[0120] Calculate T according to the component's stability load ratio R' using the following formula. c2 :

[0121]

[0122] Based on the above calculation results, the critical temperature T of the steel beam without fire protection measures is determined. c The temperature is 335℃.

[0123] T s,max With T c By comparing, we obtain T. c ≤T s,maxThis indicates that steel beams without protective measures do not meet fire protection design requirements and that an integrated fireproof and decorative structure is needed for the steel beams.

[0124] Step 4: Determine the performance parameters of the non-intumescent fireproof coating, masonry mortar, plastering mortar, and autoclaved aerated concrete blocks for the integrated fireproof and decorative structure based on the type test report and instructions provided by the manufacturer.

[0125] Step 5: Based on the performance parameters of the integrated fireproof and decorative structure, such as... Figure 2 The diagram shows the addition of an integrated fire-resistant and decorative structure to the steel beam. Calculations and analyses of the steel beam are performed, and the design fire resistance limit t of the steel beam is obtained from the following formula. m The highest temperature inside T ps,max ;

[0126]

[0127] The highest temperature T of the steel beam with integrated fireproof and decorative structure at 1.5 hours is calculated using the above formula. ps It is 367℃, or T ps,max =367℃;

[0128] The critical temperature T of the steel beam related to the load ratio R of the steel beam pc =T c =335℃.

[0129] Step 6: Place T ps,max With T pc By comparing, we obtain T. pc ≤T ps,max This indicates that the integrated fireproof and decorative structure does not meet the fire protection design requirements and needs to be improved.

[0130] Returning to step 4, increase the fire-retardant coating thickness to 20mm, and repeat the steps in step 5 to obtain the highest temperature T of the steel beam with the integrated fire-retardant and decorative structure after 1.5 hours. ps,max It is 306℃;

[0131] Re-t ps,max With T pc By comparing, we obtain T. pc >T ps,max This indicates that the integrated fireproof and decorative structure meets the fireproof design requirements, and therefore the integrated fireproof and decorative structure can be used for fireproof design of steel beams.

[0132] Based on the same inventive concept, the present invention also proposes a fireproof and decorative integrated steel beam, designed using the above method. The fireproof and decorative integrated steel beam includes a steel beam and a fireproof and decorative integrated structure. The fireproof and decorative integrated structure includes aerated concrete blocks and / or fine stone concrete filled on both sides of the steel beam. The fireproof and decorative integrated structure also includes plastering mortar and / or non-expanding fireproof coating applied to the bottom of the beam.

[0133] The fireproof and decorative integrated structure of the present invention includes a variety of construction methods.

[0134] Figure 2 The construction method of filling both sides of the steel beam (i.e. H-beam 3) with aerated concrete blocks 5 and applying plastering mortar 1, and applying non-expansive fireproof coating 2 to the bottom of the beam;

[0135] Figure 3 The construction method is to fill the two sides of the steel beam with aerated concrete blocks 5 and apply plastering mortar 1, and also apply plastering mortar 1 to the bottom of the beam;

[0136] Figure 4 The construction method is to fill one side of the steel beam with aerated concrete blocks 5, fill the other side with fine stone concrete 8, and apply plastering mortar 1 to both sides and the bottom of the beam.

[0137] Figure 5 A fireproof structural model of a steel beam with aerated concrete blocks 5 filled on both sides and coated with plastering mortar 1, and plastering mortar 1 or non-expansive fireproof coating 2 applied to the bottom of the beam.

[0138] Figure 6 A fireproof structural model of a steel beam is constructed by filling one side of the steel beam with aerated concrete blocks 5, filling the other side with fine stone concrete 8, and applying finishing mortar 1 to both sides and the bottom of the beam.

[0139] like Figure 2 , Figure 3 and Figure 5 As shown, aerated concrete blocks 5 are installed on both sides of the web of the steel beam. Mortar is filled between the aerated concrete blocks 5 and the web. Finishing mortar 1 is applied to the outer surface of the aerated concrete blocks 5. The bottom end of the lower flange of the steel beam can be coated with non-expanding fireproof paint 2 or finishing mortar 1. Figure 4 and Figure 6 As shown, an aerated concrete block 5 is provided on one side of the web of the steel beam, and mortar is filled between the aerated concrete block 5 and the web. The outer surface of the aerated concrete block 5 is coated with finishing mortar 1. Fine stone concrete 8 is poured on the other side of the web of the steel beam, and steel bars 9 can be installed inside the fine stone concrete 8. The outer surface of the fine stone concrete 8 is coated with finishing mortar 1.

[0140] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A fireproof design method for an integrated fireproof and decorative steel beam, characterized in that, Includes the following steps: Step 1: Obtain the fire protection design parameters for the steel beams; Step 2: Obtain the design fire resistance rating t of the steel beam without any fire protection measures. m The highest temperature inside T s,max ; Step 3: Based on the fire protection design parameters of the steel beam, determine the critical temperature T of the steel beam without fire protection measures. c ; Step 4: Based on the highest temperature T of the steel beam under conditions where no fire protection measures are installed. s,max and critical temperature T c Determine whether the steel beam meets the fire protection design requirements. If it does, the steel beam will no longer be equipped with an integrated fireproof and decorative structure. If the fire protection design requirements are not met, a fire-resistant and decorative integrated structure shall be designed according to the fire resistance rating of the steel beams that require fire protection design. Step 5: Based on the performance parameters of the integrated fireproof and decorative structure, obtain the design fire resistance limit t of the steel beam when fire protection measures are in place. m The highest temperature inside T ps,max ; Step 6: Based on the highest temperature T of the steel beam under fire protection measures, ps,max and critical temperature T c To determine whether the fireproof and decorative integrated structure in the steel beam meets the fire protection design requirements, if it does not meet the fire protection design requirements, the thickness and / or material of the fireproof and decorative integrated structure is changed, and the process returns to step 5 until the fireproof and decorative integrated structure meets the fire protection design requirements. In step 5, with fire protection measures in place, the steel beam meets the design fire resistance limit t. m The highest temperature inside T ps,max The following formula is used for iterative processing to obtain: ; ; ; ; in, This indicates that with fire protection measures in place, the steel beam is in the condition of (t, t+). Temperature rise within ) Indicates the time step; This represents the overall heat transfer coefficient of the steel beam; V represents the fire-exposed surface area per unit length of the steel beam; V represents the volume per unit length of the steel beam; k represents the parameter that the filling material in the web of the steel beam has a delaying effect on the temperature rise of the lower flange. and These represent the density and specific heat of steel, respectively. This represents the average temperature of the hot flue gas at time t; This indicates the temperature of the lower flange of the steel beam at time t, assuming fire protection measures are in place. In the above formula, and These represent the thickness and width of the steel beam flange, respectively. λ1, λ2, and λ3 represent the combined heat transfer coefficients of the lower, left, and right sides of the steel beam's lower flange, respectively; λ1, λ2, and λ3 represent the equivalent heat transfer coefficients of the materials used in the integrated fireproof and decorative structure of the lower, left, and right sides of the steel beam's lower flange, respectively; d1, d2, and d3 represent the thicknesses of the integrated fireproof and decorative structure of the lower, left, and right sides of the steel beam's lower flange, respectively.

2. The fireproof design method for an integrated fireproof and decorative steel beam according to claim 1, characterized in that, In step 5, with fire protection measures in place, the steel beam meets the design fire resistance limit t. m The highest temperature inside T ps,max Obtained through iterative processing, the iterative processing steps include: Step 5.1: Utilize the steel beam temperature at time t The steel beam is obtained at a time step internal temperature rise ; Step 5.2: Calculate the temperature of the steel beam at time t+Δt. Updated to the steel beam temperature at time t With temperature rise sum; Step 5.3: Repeat steps 5.1 and 5.2 above to check the temperature of the steel beam. Iterative processing was performed to obtain the steel beam temperature at different times. And will design fire resistance limit t m The highest temperature of the steel beams inside As a steel beam, its fire resistance rating is designed to be [t]. m The highest temperature inside T ps,max .

3. The fireproof design method for an integrated fireproof and decorative steel beam according to claim 1, characterized in that, In step 2, without fire protection measures, the steel beam meets the design fire resistance limit t. m The highest temperature inside T s,max Obtained through iterative processing, the iterative processing steps include: Step 2.1: Use the steel beam temperature T at time t s The steel beam is obtained at a time step internal temperature rise ; Step 2.2: Calculate the temperature T of the steel beam at time t+Δt. s Updated to the steel beam temperature T at time t. s With temperature rise sum; Step 2.3: Repeat steps 2.1 and 2.2 above to check the temperature T of the steel beam. s Iterative processing was performed to obtain the steel beam temperature T at different times. s And will design fire resistance limit t m The highest temperature of the steel beam inside is T s As a steel beam, its fire resistance rating is designed to be [t]. m The highest temperature inside T s,max .

4. The fireproof design method for an integrated fireproof and decorative steel beam according to claim 3, characterized in that, In step 2, without fire protection measures, the steel beam meets the design fire resistance limit t. m The highest temperature inside T s,max The following formula is used for iterative processing to obtain: ; ; ; In the formula, This indicates that without fire protection measures, the steel beam is in the condition of (t, t+). Temperature rise within ) Indicates the time step; This represents the overall heat transfer coefficient of the steel beam; Indicates the heat transfer coefficient by heat convection; Indicates the coefficient of thermal radiation heat transfer; and These represent the density and specific heat of steel, respectively; F represents the surface area of ​​the steel beam exposed to fire per unit length; V represents the volume of the steel beam per unit length. This represents the average temperature of the hot flue gas at time t; This indicates the internal temperature of the steel beam at time t without any fire protection measures in place. Indicates the overall emissivity; This represents the Stefan-Boltzmann constant.

5. The fireproof design method for an integrated fireproof and decorative steel beam according to claim 1, characterized in that, In step 4, based on the highest temperature T of the steel beam under the condition that no fire protection measures are set up... s,max and critical temperature T c The steps for determining whether the steel beam meets the fire protection design requirements include: If the critical temperature T of the steel beam c ≥ The highest temperature of the steel beam T s,max This indicates that the steel beam meets the fire protection design requirements, and the steel beam no longer needs to be equipped with an integrated fireproof and decorative structure; If the critical temperature T of the steel beam c The highest temperature of the steel beam T s,max If the result is negative, it indicates that the steel beam does not meet the fire protection design requirements.

6. The fireproof design method for an integrated fireproof and decorative steel beam according to claim 1, characterized in that, In step 6, based on the highest temperature T of the steel beam under fire protection measures, ps,max and critical temperature T c The steps to determine whether the integrated fireproof and decorative structure in the steel beam meets the fire protection design requirements include: If the critical temperature T of the steel beam c ≥ The highest temperature of the steel beam T ps,max This indicates that the steel beam meets the fire protection design requirements; If the critical temperature T of the steel beam c The highest temperature of the steel beam T ps,max If the result is negative, it indicates that the steel beam does not meet the fire protection design requirements.

7. The fireproof design method for an integrated fireproof and decorative steel beam according to claim 1, characterized in that, The fire protection design parameters of the steel beam in step 1 include the design fire resistance rating and the design fire resistance limit t. m Section strength load ratio R, component stability load ratio R', and stability coefficient of steel beam at room temperature. And the air temperature rise curve.

8. The fireproof design method for an integrated fireproof and decorative steel beam according to claim 7, characterized in that, The section strength load ratio R is obtained according to the following formula: ; ; In the formula, R represents the cross-sectional strength load ratio of the steel beam under fire; M represents the maximum design value of the bending moment of the steel beam under fire. γ represents the flexural bearing capacity of the steel beam at room temperature; γ represents the plastic development coefficient of the steel beam section. represents the net section modulus of the most unfavorable section of the steel beam; f represents the yield strength of the steel at room temperature; The component stability load ratio R' of the steel beam is obtained according to the following formula: ; ; ； ; In the formula, R' represents the component stability load ratio of the steel beam under fire conditions; This indicates the overall stable bearing capacity of the steel beam at room temperature; The value represents the stability coefficient of the steel beam at room temperature; W represents the gross section modulus of the steel beam. The equivalent bending moment coefficient represents the overall stability of the steel beam; This represents the slenderness ratio of the steel beam about the weak axis yy of the cross section between the lateral support points; This represents the gross cross-sectional area of ​​the steel beam; Indicates the total height of the steel beam section; This indicates the thickness of the compression flange of the steel beam; Indicates the influence coefficient of asymmetry in the steel beam section; Indicates the steel grade correction factor; This indicates the distance between the lateral support points of the compression flange of the steel beam; This represents the radius of gyration of the gross section of the steel beam about the weak axis, y-axis. The expression for the air temperature rise curve of the steel beam is as follows: ; In the formula, The value represents the average temperature of the hot smoke at time t; t represents the duration of the fire. This indicates the temperature of the indoor environment before the fire.

9. A fireproof and decorative integrated steel beam, designed according to the method described in claim 1, characterized in that, The fireproof and decorative integrated steel beam includes a steel beam and a fireproof and decorative integrated structure; the fireproof and decorative integrated structure includes aerated concrete blocks and / or fine stone concrete filled on both sides of the steel beam, and the fireproof and decorative integrated structure also includes plastering mortar and / or non-expansive fireproof coating applied to the bottom of the beam.

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