Fire-retardant coating modified high-ductility fabricated composite wood beam

Abstract

This invention discloses a high-ductility prefabricated composite timber beam modified with fire-retardant coating, belonging to the field of prefabricated timber structure building and timber structure fire protection technology. It includes a glued laminated timber beam and a composite fireproof layer. Limiting grooves are spaced apart on both sides and the bottom of the glued laminated timber beam. Limiting clips with diamond-shaped fastening mechanisms are installed in the limiting grooves. The cavities of the limiting clips are filled with a heat-insulating and sealing agent. The composite fireproof layer, from the inside out, consists of an anchoring base layer, a foamed flame-retardant layer, a fire-resistant lining, a fire-resistant mesh fabric, and a top coating. The elastic clips on the side of the fire-resistant lining facing the glued laminated timber beam match the limiting clips. This allows for quick prefabricated installation of the fireproof layer, completely eliminating the risk of thermal bridging from metal fasteners, effectively preventing cracking and failure of the fireproof layer due to timber beam deflection, and significantly improving the fire resistance limit, assembly efficiency, and structural stability of the glued laminated timber beam, making it suitable for the application needs of large-span prefabricated timber structure buildings.

Description

Technical Field

[0001] This invention relates to the field of prefabricated timber structure building technology, specifically to a fire-retardant modified high-ductility prefabricated composite timber beam. Background Technology

[0002] In prefabricated timber structures, glued laminated timber beams are the core load-bearing components, and their fire resistance directly determines the building's fire resistance limit and safety. Currently, the mainstream fire protection methods for glued laminated timber beams are on-site application of intumescent fire-retardant coatings and bonding of fire-resistant gypsum boards. Some existing technologies combine fire-resistant components with timber beams to form composite timber beams, which are then used as prefabricated beams in engineering applications.

[0003] Existing prefabricated composite timber beams still have many shortcomings that fail to meet the high-efficiency and safety requirements of prefabricated buildings. On-site coating and plasterboard bonding methods result in long construction cycles and poor quality control, failing to meet the requirements of factory-produced prefabricated components. In existing prefabricated composite timber beams, the connection between fire-resistant components and the timber beams often uses metal staples, which can easily create thermal bridges, leading to premature localized carbonization and failure of the timber beams during a fire. Furthermore, the fire-resistant structures of existing prefabricated composite timber beams are designed with uniform length throughout, failing to consider the large deflection characteristics of high-ductility timber beams in the mid-span tension zone. This makes them prone to cracking and detachment of the fire-resistant layer and flame penetration into the timber beams during a fire, resulting in substandard fire resistance. Moreover, the design of the fire-resistant layer thickness only considers fire resistance time and does not couple with the deformation of the timber beam structure, indicating insufficient design rationality.

[0004] Therefore, there is an urgent need for a fire-resistant modified prefabricated composite wood beam that can be tightly integrated with the wood beam without the risk of thermal bridging, can adapt to the deformation characteristics of highly ductile wood beams, and can be prefabricated in the factory and quickly assembled on site. Summary of the Invention

[0005] This invention aims to solve the problems of complex construction, easy formation of thermal bridges, inability to adapt to the flexural deformation and cracking failure of high-ductility timber beams, and the disconnect between fire protection design and structural characteristics in existing fire-resistant timber beam fire-resistant structures. It provides a high-ductility prefabricated composite timber beam modified with fire-retardant coating.

[0006] A fire-retardant modified high-ductility prefabricated composite timber beam includes a glued laminated timber beam and a composite fireproof layer.

[0007] The glued laminated timber beam has spaced-apart limiting grooves on both sides and the bottom surface. Limiting fasteners are installed in the limiting grooves, and the cavities of the limiting fasteners are filled with heat-insulating sealant.

[0008] The composite fireproof layer comprises, from the inside out, an anchoring underlayer, a foamed flame-retardant layer, a fire-resistant lining, a fire-resistant mesh, and a topcoat. The anchoring underlayer is bonded to the outer surface of the glued laminated timber beam. This underlayer contains penetrating anchoring monomers with phosphate ester groups, which penetrate into the pores of the glued laminated timber beam surface, forming a penetrating anchoring structure with the cellulose hydroxyl groups of the timber beam. The topcoat slurry penetrates the mesh of the fire-resistant mesh, filling the area between the fire-resistant mesh and the fire-resistant lining and covering the outer surface. After curing, the topcoat forms an integrated anchoring structure with the fire-resistant lining and the foamed flame-retardant layer.

[0009] The fire-resistant lining is equipped with an elastic clip on the side facing the glued laminated timber beam. The elastic clip corresponds one-to-one with the limiting slot. The elastic clip is pressed into the limiting slot and locked in place. The limiting platform of the elastic clip presses against the surface of the mesh reinforcement of the fire-resistant mesh. After the elastic clip is inserted into the limiting slot, it squeezes the heat insulation sealant, so that the heat insulation sealant wraps the end of the elastic clip and isolates the elastic clip from direct thermal contact with the glued laminated timber beam.

[0010] Furthermore, the limiting slot has a depth of 30-50mm and a slot diameter of 8-10mm. Adjacent limiting slots are arranged equidistantly along the length of the glued laminated timber beam, with a spacing of 200-300mm.

[0011] Furthermore, the minimum design total thickness of the composite fireproof layer satisfies the formula: ,in This refers to the minimum total design thickness of the composite fireproof layer. To achieve the target fire resistance limit, This represents the maximum permissible flexural deformation value of the glued laminated timber beam. This is the conversion factor for the ultimate fire-resistant thickness. Thickness conversion factor for deformation adaptation.

[0012] Furthermore, ,in This is the conversion factor for the standard fire resistance test reference. The thermal conductivity of the reference fireproof material; The overall thermal conductivity of the composite fireproof layer is determined by actual measurement. This represents the measured maximum foaming ratio of the foamed flame-retardant layer. Wherein is the correction factor for the deformation adaptation of the wooden structure, the measured ultimate tensile strain of the composite fireproof layer, and the correction factor for the elastic modulus of the fire-resistant mesh.

[0013] Furthermore, the anchoring substrate includes a first film-forming monomer and a penetrating anchoring monomer. The first film-forming monomer includes styrene, n-butyl acrylate, and glycidyl tert-carbonate acrylate. The mass of the n-butyl acrylate is less than the mass of the styrene. The penetrating anchoring monomer is an acrylate monomer containing a phosphate ester group.

[0014] Furthermore, the root of the limiting clip is provided with a diamond-shaped fastening mechanism, which uses the rotation of a micro screw to press the diamond-shaped tip against the glued laminated timber beam.

[0015] Furthermore, the foamed flame-retardant layer includes a second film-forming monomer, an internal crosslinking monomer, an intumescent flame-retardant system, inorganic fillers, deionized water, and environmentally friendly additives. The second film-forming monomer is methyl methacrylate, n-butyl acrylate, and acrylic acid. The internal crosslinking monomer is ethylene glycol dimethacrylate. The intumescent flame-retardant system is an acid source ammonium polyphosphate, a carbon source pentaerythritol, microcrystalline cellulose, and a gas source melamine.

[0016] Furthermore, the topcoat includes a third film-forming monomer, a vinyl silane coupling agent, and a self-crosslinking monomer. The third film-forming monomer is methyl methacrylate, n-butyl acrylate, and acrylic acid. The vinyl silane coupling agent is vinyltrimethoxysilane, and the self-crosslinking monomer is ethyl acetoacetate methacrylate.

[0017] Furthermore, the glued laminated timber beam has cantilevered ends at both ends, and a compression-resistant steel plate is provided under the cantilevered ends. A vertical shear-resistant steel plate is provided inside the cantilevered ends, and the shear-resistant steel plate and the compression-resistant steel plate are welded together.

[0018] Furthermore, the fire-resistant lining plate at the corresponding position of the tension zone at the mid-span of the glued laminated timber beam is a segmented structure, with a deformation gap reserved between adjacent segments. The deformation gap is filled with an elastic fireproof sealant, and the arrangement density of the elastic clips is higher than that of the beam end area.

[0019] Compared with existing technologies, the present invention has the following significant advantages:

[0020] 1. Enables factory prefabrication and on-site quick installation of fireproof layers, eliminating the need for wet construction and metal fasteners, completely eliminating the risk of thermal bridging, and significantly improving the efficiency of prefabricated construction and the controllability of fireproof quality.

[0021] 2. Differentiated fireproofing design is applied to the tension zone at the mid-span of high-ductility timber beams to effectively prevent cracking and detachment of the fireproof layer caused by flexural deformation during a fire, and significantly improve the fire resistance limit of the timber beams. The fireproof layer thickness is coupled with the deformation of the timber beam structure to adapt to different working conditions and fire resistance requirements, ensuring the long-term stability and effectiveness of the fireproof structure. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall cross-sectional structure of an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the end structure of a glued laminated timber beam according to an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of the limiting card structure according to an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of the fire-resistant mesh fabric structure according to an embodiment of the present invention;

[0027] Figure 5 This is an exploded view of the end structure of the glued laminated timber beam according to an embodiment of the present invention;

[0028] Figure 6 This is a schematic diagram of the structure of the compression-resistant steel plate and the shear-resistant steel plate after welding according to an embodiment of the present invention;

[0029] Figure 7 This is a schematic diagram showing the location of the elastic fireproof seal in an embodiment of the present invention;

[0030] Figure 8 for Figure 7 A magnified view of part M.

[0031] In the diagram: 1. Glulam beam; 2. Composite fireproof layer; 21. Anchoring base layer; 22. Foamed flame-retardant layer; 23. Fire-resistant lining board; 24. Fire-resistant mesh fabric; 25. Topcoat; 3. Limiting slot; 31. Limiting clip; 311. Diamond fastening mechanism; 312. Micro screw; 4. Thermal insulation sealant; 5. Elastic clip; 51. Limiting platform; 6. Cantilever support head; 7. Compression-resistant steel plate; 8. Shear-resistant steel plate; 9. Elastic fireproof sealant. Detailed Implementation

[0033] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0034] See Figures 1 to 8According to the present invention, a fire-retardant modified high-ductility prefabricated composite timber beam includes a glued laminated timber beam 1 and a composite fireproof layer 2. Limiting grooves 3 are spaced apart on both sides and the bottom of the glued laminated timber beam 1. Limiting fasteners 31 are installed within the limiting grooves 3, and the cavities of the limiting fasteners 31 are filled with a heat-insulating and sealing agent 4. The composite fireproof layer 2 consists of, from the inside out, an anchoring underlayer 21, a foamed flame-retardant layer 22, a fire-resistant lining board 23, a fire-resistant mesh fabric 24, and a topcoat 25. The anchoring underlayer 21 is attached to the outer surface of the glued laminated timber beam 1 and contains a penetrating anchoring monomer with phosphate ester groups, which penetrates into the pores of the glued laminated timber beam 1 surface and forms a penetrating anchoring structure with the cellulose hydroxyl groups of the timber beam. The topcoat 25 slurry penetrates the mesh of the refractory mesh 24, fills the area between the refractory mesh 24 and the refractory lining 23, and covers the outer surface. After curing, the topcoat 25 forms an integrated anchoring structure with the refractory lining 23 and the foamed flame-retardant layer 22. The refractory lining 23 is equipped with an elastic clip 5 on the side facing the glued laminated timber beam 1. The elastic clip 5 corresponds one-to-one with the limiting groove 3. The elastic clip 5 is pressed into the limiting groove 3 and locked in place. The limiting platform 51 of the elastic clip 5 is pressed against the surface of the refractory lining 23. After the elastic clip 5 is inserted into the limiting groove 3, the heat insulation sealant 4 is squeezed, so that the heat insulation sealant 4 wraps around the end of the elastic clip 5, preventing the elastic clip 5 from direct thermal contact with the glued laminated timber beam 1.

[0035] The glued laminated timber beam 1 is the core load-bearing component of the composite timber beam, providing an installation foundation for the fireproof structure, while meeting the load-bearing requirements of large-span prefabricated buildings through its high ductility design.

[0036] The composite fireproof layer 2 provides full-coverage fire protection for the glued laminated timber beam 1, blocking heat transfer in a fire, delaying the carbonization of the timber beam, and ensuring the load-bearing capacity of the timber beam in a fire.

[0037] Limiting slots 3 are provided on both sides and the bottom of the glued laminated timber beam 1. The limiting clips 31 provide a positioning and locking structure for the installation of the composite fireproof layer 2, preventing the composite fireproof layer 2 from falling off.

[0038] The heat insulation sealant 4 is pre-filled into the limiting slot 3. On the one hand, it fills all the gaps, isolates the elastic clip 5 from direct contact with the glued laminated timber beam 1, and eliminates thermal bridges. On the other hand, it can foam and expand in a fire, further blocking the heat transfer path.

[0039] The anchoring base layer 21 is attached to the outer surface of the glued laminated timber beam 1. The anchoring monomer containing phosphate ester groups penetrates into the pores of the timber beam surface and forms a chemical bond with the cellulose hydroxyl groups of the timber beam, thereby achieving a strong interfacial bond between the composite fireproof layer 2 and the glued laminated timber beam 1, and preventing the composite fireproof layer 2 from delaminating and falling off in the event of a fire.

[0040] The foamed flame-retardant layer 22 is the core heat insulation component of the composite fireproof layer 2. In a fire, it can foam and expand to form a dense heat-insulating carbon layer, which greatly reduces the heat transfer rate and improves the fire resistance limit of the wooden beam.

[0041] The fire-resistant lining 23 provides rigid support for the composite fireproof layer 2, while also providing fireproof and heat insulation properties. It provides an installation base for the elastic clip 5 and ensures the structural integrity of the composite fireproof layer 2.

[0042] The fire-resistant mesh 24 is attached to the outside of the fire-resistant lining 23, which can improve the crack resistance and tensile strength of the composite fireproof layer 2, and prevent the fireproof layer from cracking due to the bending and deformation of the wooden beams during a fire. At the same time, it is wrapped and anchored by the surface coating 25 to further prevent the mesh from slipping off.

[0043] The topcoat 25 provides an outer layer of protection for the composite fireproof layer 2. Its slurry penetrates the mesh of the fire-resistant mesh 24 to achieve full interface anchoring between the layers, while also providing weather protection and extending the service life of the fireproof layer.

[0044] The elastic clip 5 is installed on the side of the fire-resistant lining plate 23 facing the glued laminated timber beam 1, corresponding one-to-one with the limiting clip 3. The composite fireproof layer 2 can be quickly installed by pressing and snapping it in, without the need for on-site drilling and nailing. It is suitable for the needs of prefabricated quick installation and quick disassembly. Its limiting platform 51 presses against the mesh ribs of the fire-resistant mesh cloth 24, and at the same time squeezes the heat insulation sealant 4 to isolate heat conduction, which has the triple functions of fixing, limiting and heat insulation.

[0045] According to the present invention, a fire-retardant coating modified high-ductility prefabricated composite wood beam has a limiting groove 3 with a groove depth of 30~50mm and a groove diameter of 8~10mm. Adjacent limiting grooves 3 are arranged at equal intervals along the length direction of the glued laminated wood beam 1 with a spacing of 200~300mm.

[0046] The connection between the limiting slot 3 and the glued laminated timber beam 1 adopts a prefabricated embedding method. The specific installation process is as follows: First, according to the design dimensions, installation holes matching the size of the limiting slot 3 are pre-cut at predetermined positions on both sides and the bottom of the glued laminated timber beam 1 using specialized grooving equipment. Then, the prefabricated limiting slot 3 is embedded into the installation holes. Fire-retardant structural adhesive is used to fill and bond the slot with the inner wall of the hole. The structural adhesive penetrates into the pores of the timber beam surface, forming a firm bond with the timber cellulose, achieving an integrated connection between the limiting slot 3 and the glued laminated timber beam 1. The size limitation of the limiting slot 3 ensures the fitting accuracy with the elastic locking head 5. The slot depth matches the locking depth of the elastic locking head 5, and the slot diameter and closing width match the diamond-shaped expansion locking structure of the elastic locking head 5, achieving stable locking. The equidistant arrangement of adjacent limiting slots 3 ensures a uniform distribution of the fixing force of the composite fireproof layer 2, avoiding local fixing failure. A slot depth less than 30mm will result in insufficient locking depth, insufficient fixing force, and easy detachment. A groove depth greater than 50mm will weaken the cross-sectional load-bearing capacity of the glued laminated timber beam 1. A spacing less than 200mm will excessively weaken the beam cross-section, while a spacing greater than 300mm will result in insufficient fixing points, making the composite fireproof layer 2 prone to warping and detachment. The preferred groove depth is 40mm, the groove diameter is 10mm, and the spacing is 250mm, balancing fixing stability and the load-bearing capacity of the timber beam.

[0047] According to the fire-retardant coating modified high-ductility prefabricated composite wood beam provided by the present invention, the minimum design total thickness of the composite fireproof layer 2 satisfies the formula: ,in The minimum total design thickness for composite fireproof layer 2, To achieve the target fire resistance limit, The maximum allowable flexural deformation value for glued laminated timber beam 1 is given. This is the conversion factor for the ultimate fire-resistant thickness. Thickness conversion factor for deformation adaptation.

[0048] This formula is derived based on the building fire resistance limit state design method and the coating crack resistance theory. For the first time, it couples the bending deformation of the wooden beam structure with the design of the fireproof layer thickness, solving the problem that the fireproof layer is prone to cracking and failure due to existing technologies that only consider the fire resistance time.

[0049] This is the minimum total design thickness of the composite fireproof layer 2, to avoid insufficient thickness leading to fireproof failure, or excessive thickness causing material waste.

[0050] The target fire resistance limit is a core indicator of fire protection design, determining the basic insulation thickness required for the fireproof layer.

[0051] The maximum allowable flexural deformation value for glued laminated timber beam 1 is determined according to the timber structure design code and the load-bearing design of timber beams, reflecting the deformation characteristics of high ductility timber beams.

[0052] The fire resistance limit thickness conversion factor reflects the thermal insulation performance of the composite fireproof layer 2. It is determined by the material properties and structural form of the composite fireproof layer. The better the thermal insulation performance, the smaller the α value, and the thinner the required basic fireproof thickness.

[0053] The thickness conversion factor for deformation adaptation reflects the deformation and crack resistance of the composite fireproof layer 2. The better the crack resistance, the smaller the β value, and the smaller the thickness increment required to adapt to the deformation of the wooden beam.

[0054] A fire-retardant coating-modified high-ductility prefabricated composite wood beam is provided according to the present invention. ,in This is the conversion factor for the standard fire resistance test reference. The thermal conductivity of the reference fireproof material; The overall thermal conductivity of composite fireproof layer 2 is determined by actual measurement; The measured maximum foaming ratio of the foamed flame-retardant layer 22. ,in A reference correction factor is used to adapt to deformation of the wooden structure; The measured ultimate tensile strain of composite fireproof layer 2; This is the modulus of elasticity correction factor for refractory mesh 24.

[0055] The formula for calculating α is derived from the one-dimensional steady-state heat transfer theory, integrating the material insulation performance of the composite fireproof layer with the active insulation effect of the foamed flame-retardant layer, thus achieving precise design of the fire-resistant thickness. It is a standard fire resistance test reference conversion factor, determined by GB / T9978.1 Fire Resistance Test Method for Building Components. It is a fixed reference value to ensure the consistency between design values ​​and test results. The thermal conductivity of the benchmark fireproof material is used, and the standard value of the benchmark fireproof material specified in the specification is adopted to provide a unified reference for the design. The comprehensive thermal conductivity of composite fireproof layer 2 is determined by the measured thermal insulation performance of the multi-layer structure, reflecting the actual fireproof and thermal insulation capabilities. The measured maximum foaming ratio of the foamed flame-retardant layer 22 is the highest foaming ratio. The higher the foaming ratio, the thicker the heat-insulating carbon layer formed in a fire, the better the heat insulation performance, and the thinner the required basic fireproof thickness.

[0056] The formula for calculating β is derived from the theory of crack resistance in mechanics of materials. It integrates the ductility of the composite fireproof layer 2 with the reinforcing effect of the mesh cloth, and achieves precise design of deformation-adaptive thickness. The reference correction coefficient for timber structure deformation adaptation is determined by the GB50005 timber structure design standard. It is a fixed reference value to ensure that the design meets the requirements for timber structure deformation control. The measured ultimate tensile strain of composite fireproof layer 2 is the larger the ultimate tensile strain. The greater the ultimate tensile strain, the stronger the resistance to deformation and cracking of composite fireproof layer 2, and the smaller the thickness increment required to adapt to the deformation of the wooden beam. E is the elastic modulus correction factor of the fire-resistant mesh 24, which reflects the enhancement effect of the mesh on the crack resistance of the composite fireproof layer 2. The higher the elastic modulus matching degree, the better the enhancement effect and the smaller the E value.

[0057] Formula Design Example: This example demonstrates the design of a high-ductility glued laminated timber beam (beam 1) commonly used in prefabricated buildings. The target fire resistance rating T is taken as 0.5 hours. The maximum allowable flexural deformation value for glued laminated timber beam 1 is... Taking L / 300 and the beam span as 8m, therefore We take 26.67mm, but 27mm is chosen based on the actual engineering requirements.

[0058] Standard fire resistance test reference conversion factor Take 1.0 mm / h as the reference thermal conductivity of fireproof material Taking 0.10 W / (m・K), the overall thermal conductivity of composite fireproof layer 2 is... The measured value is taken as 0.12 W / (m·K), and the measured maximum foaming ratio N of the foamed flame-retardant layer 22 is taken as 20 times. Substituting into the calculation formula for α, .

[0059] Timber Structure Deformation Adaptation Reference Correction Coefficient Taking 0.06, the measured ultimate tensile strain of composite fireproof layer 2 Take 2.5% (to improve the deformation resistance of the composite fireproof layer 2), and take the elastic modulus correction factor E of the fire-resistant mesh fabric as 1.5. Substitute these values ​​into the calculation formula for β. .

[0060] α, β, T, Substitute into the general formula, Based on the actual engineering situation and manufacturing specifications, 45mm is taken as the minimum total design thickness of composite fireproof layer 2.

[0061] According to the present invention, a fire-retardant coating modified high-ductility prefabricated composite timber beam has an anchoring substrate 21 composed of a first film-forming monomer, a penetrating anchoring monomer, and auxiliary additives. The materials are proportioned by weight as follows: 38-42 parts styrene, 22-26 parts n-butyl acrylate, 6-8 parts glycidyl tert-carbonate acrylate, 18-22 parts acrylate penetrating anchoring monomer containing phosphate groups, 0.8-1.2 parts initiator, 0.5-0.8 parts dispersant, and 8-12 parts deionized water, for a total weight of 100 parts. The first film-forming monomer constitutes the basic film-forming system of the anchoring substrate 21. The penetrating anchoring monomer achieves interfacial bonding with the glued laminated timber beam 1 and also provides flame retardant functionality. The auxiliary additives ensure the coating's workability and film-forming quality. Styrene, as the core hard monomer of the film-forming system, accounts for the largest proportion. Its main function is to improve the rigidity, hardness, and adhesion of the anchoring substrate 21 to the wooden beam surface, prevent the coating from softening and flowing under high temperature conditions, and ensure the structural stability of the anchoring substrate 21. Butyl acrylate, as a flexibility modifier monomer, is used in a lower amount than styrene. It can improve the flexibility of the anchoring substrate 21, prevent the coating from cracking due to excessive rigidity, and improve the film-forming continuity of the coating. Glycidyl tert-acrylate, as a functional modifying monomer, can significantly improve the weather resistance and crosslinking density of the coating, enhancing the long-term performance of the anchoring substrate 21. Stability is ensured to prevent powdering and delamination after long-term exposure. Acrylic ester-based penetrating anchoring monomers containing phosphate groups can penetrate into the pores of the glued laminated timber beam 1 surface and form stable covalent bonds with the cellulose hydroxyl groups of the timber beam, achieving a strong interfacial bond between the composite fireproof layer 2 and the glued laminated timber beam 1. On the other hand, the phosphate groups have a flame-retardant synergistic effect, which can delay the carbonization of the timber beam surface and further improve the interfacial fireproof performance. Auxiliary additives and initiators promote the full polymerization reaction of each monomer, and dispersants ensure uniform mixing of each material, avoiding precipitation and stratification, and ensuring that the anchoring bottom layer 21 coating is uniform and consistent.

[0062] Four sets of comparative experiments were designed using the controlled variable method. Experimental conditions included: one identical glued laminated timber beam specimen, identical construction techniques, and identical curing environment (25℃, 60% relative humidity, 7 days curing). Only the presence or amount of a single material was varied. Test indicators included coating adhesion (GB / T5210-2006), weather resistance (GB / T1865-2009, artificial accelerated aging for 1000 hours), interfacial bond strength (tensile shear strength), and flame retardant properties (oxygen index, GB / T2406-2008). Specific experimental schemes and results are as follows:

[0063] Experimental group 1 (blank control group) used the following optimal formulation: 40 parts styrene, 23 parts n-butyl acrylate, 7 parts glycidyl tert-carbonate acrylate, 20 parts acrylate penetrating anchoring monomers containing phosphate groups, 1.0 part initiator, 0.6 parts dispersant, and 8.4 parts deionized water, for a total mass of 100 parts. The test results were: adhesion grade 1, no powdering or cracking in weather resistance, interfacial bond strength of 1.8 MPa, and oxygen index of 28%.

[0064] Experimental Group 2 (without styrene): The proportions of other materials remained unchanged, but styrene was removed. The test results were: adhesion level 3 (significantly decreased), insufficient coating rigidity, softening and flowing at high temperature (200℃), interfacial bonding strength 0.9MPa, and oxygen index 26%. This indicates that styrene is the core material to ensure the rigidity and adhesion of the anchoring substrate 21.

[0065] Experimental Group 3 (without n-butyl acrylate): The proportions of other materials remained unchanged, but n-butyl acrylate was removed. The test results were as follows: the coating was too rigid, and after curing, it developed fine cracks, decreased weather resistance (powdering after aging), interfacial bonding strength of 1.2 MPa, and oxygen index of 27%. This indicates that n-butyl acrylate can effectively improve the flexibility and weather resistance of the coating and prevent cracking.

[0066] Experimental Group 4 (without glycidyl acrylate): The proportions of other materials remained unchanged, but this monomer was removed. The test results were: adhesion grade 1, poor weather resistance (cracking and powdering occurred after aging), interfacial bonding strength 1.7 MPa, and oxygen index 27.5%, indicating that the main function of this monomer is to improve the weather resistance and long-term stability of the coating.

[0067] Experimental Group 5 (without penetrating anchoring monomer): The proportions of other materials remained unchanged, but this monomer was removed. The test results were: adhesion level 2, no obvious abnormality in weather resistance, interface bonding strength 0.7MPa (significantly decreased), and oxygen index 24%, indicating that the penetrating anchoring monomer is the key material for achieving strong interface bonding with wooden beams and improving flame retardant performance.

[0068] Experimental results show that the material ratio of the anchoring base layer 21 of the present invention is scientific and reasonable, and each material works synergistically and is indispensable. By controlling the amount of each material, the design goal of the anchoring base layer 21 can be achieved: "balancing rigidity and flexibility, meeting the standards for adhesion and weather resistance, and achieving excellent interface bonding and flame retardant performance", which is suitable for the fireproof and prefabricated use requirements of composite wood beams.

[0069] According to the present invention, a fire-retardant modified high-ductility assembled composite wood beam has a diamond-shaped fastening mechanism 311 at the root of the limiting clip 31. The diamond-shaped tip is pressed against the glued laminated wood beam 1 by rotating a micro-screw 312. The diamond-shaped fastening mechanism 311 at the end and the limiting clip groove 3 achieve a locking effect. A heat-insulating sealant 4 fills all gaps and wraps the end of the elastic clip 5, isolating the elastic clip 5 from direct thermal contact with the wood beam and eliminating the risk of thermal bridging.

[0070] According to the present invention, a fire-retardant coating modified high-ductility prefabricated composite wood beam has a foamed flame-retardant layer 22 composed of a second film-forming monomer, an internal crosslinking monomer, an intumescent flame-retardant system, inorganic fillers, deionized water, and environmentally friendly additives. The materials are formulated in the following proportions by mass: 25-29 parts methyl methacrylate, 18-22 parts n-butyl acrylate, 4-6 parts acrylic acid, 3-5 parts ethylene glycol dimethacrylate, 20-24 parts ammonium polyphosphate, 8-12 parts pentaerythritol, 3-5 parts microcrystalline cellulose, 4-6 parts melamine, 3-5 parts talc, 4-6 parts deionized water, 0.5-0.8 parts defoamer, and 0.5-1.2 parts thickener, for a total of 100 parts by mass. This design achieves the functions of foaming for heat insulation and high-temperature crack resistance in fire. The second film-forming monomer constitutes the basic film-forming skeleton of the foamed flame-retardant layer 22. Among them, methyl methacrylate hard monomer mainly improves the rigidity and high-temperature resistance of the coating, preventing softening and collapse at high temperatures; n-butyl acrylate soft monomer adjusts the flexibility of the coating, and works with internal crosslinking monomers to relieve high-temperature stress and prevent the coating from cracking; acrylic acid improves the interfacial adhesion between the coating and the adjacent anchoring substrate 21 and fire-resistant lining 23, ensuring tight interlayer bonding. Ethylene glycol dimethacrylate forms a three-dimensional crosslinked network that runs through the foamed flame-retardant layer 22 through a polymerization reaction, which greatly improves the ductility, high-temperature resistance and structural integrity of the coating, preventing the coating from cracking and falling off due to high-temperature softening and deformation of wooden beams during a fire. The intumescent flame-retardant system comprises an acid source, a char source, and a gas source. The acid source, ammonium polyphosphate, decomposes in a fire to produce phosphoric acid, catalyzing the carbonization of the char source. The char source, pentaerythritol, dehydrates and carbonizes under acid catalysis, forming a char layer framework. Microcrystalline cellulose assists in char layer formation and improves its density. The gas source, melamine, decomposes to produce inert gases such as ammonia and nitrogen, driving the expansion of the char layer to form a thick, dense, heat-insulating char layer that blocks heat and oxygen transfer. The inorganic filler, talc, enhances the coating's rigidity and heat resistance, reduces shrinkage, and simultaneously improves insulation, minimizing melting and flow during a fire. Environmentally friendly defoamers eliminate air bubbles generated during coating preparation, preventing porosity after curing and ensuring fire resistance. Thickeners adjust coating viscosity to suit pre-fabrication spraying and scraping applications, ensuring uniform coating thickness. Deionized water serves as the dispersion medium, ensuring uniform mixing of all materials and guaranteeing coating stability.

[0071] Five sets of comparative experiments were designed using the controlled variable method. Experimental conditions included the same substrate, same construction thickness (20mm), and same curing environment (25℃, 60% relative humidity, 7 days curing). The only variation was the presence or absence of a single core material. Test indicators included foaming ratio, charcoal layer density (simulated fire temperature of 300℃ for 1 hour), high-temperature resistance (no cracking or flow at 300℃), and flame retardant performance (oxygen index, GB / T2406-2008). Specific experimental schemes and results are as follows:

[0072] Experimental group 1 (blank control group) used the following optimal formulation: 26 parts methyl methacrylate, 19 parts n-butyl acrylate, 5 parts acrylic acid, 4 parts ethylene glycol dimethacrylate, 21 parts ammonium polyphosphate, 8 parts pentaerythritol, 3 parts microcrystalline cellulose, 4 parts melamine, 3 parts talc, 5.5 parts deionized water, 0.6 parts defoamer, and 0.9 parts thickener, for a total mass of 100 parts. The test results were: foaming ratio 18-22 times, dense and non-porous carbon layer, no cracking or flow after 1 hour at 300℃, and an oxygen index of 32%.

[0073] Experimental Group 2 (without internal crosslinking monomer): The proportions of other materials remained unchanged, but ethylene glycol dimethacrylate was removed. The test results were: foaming ratio of 17~20 times, loose carbon layer that was easy to fall off, cracking occurred after 300℃ constant temperature for 30 min, and oxygen index of 30%. This indicates that the internal crosslinking monomer is the core material to ensure the coating's high temperature resistance and crack resistance and to improve the stability of the carbon layer.

[0074] Experimental Group 3 (without ammonium polyphosphate): The proportions of other materials remained unchanged, but ammonium polyphosphate was removed. The test results were: foaming ratio of 5 to 8 times, no obvious carbon layer formation, flow occurred after 10 minutes of constant temperature at 300℃, and oxygen index of 23%. This indicates that ammonium polyphosphate, as an acid source, is the key to initiating the expansion flame retardant reaction and forming a heat-insulating carbon layer.

[0075] Experimental Group 4 (without pentaerythritol): The proportions of other materials remained unchanged, but pentaerythritol was removed. The test results were: foaming ratio of 8 to 12 times, thin and loose carbon layer, cracking occurred after 20 minutes of constant temperature at 300℃, and oxygen index of 26%. This indicates that pentaerythritol, as a carbon source, is the core component that supports the carbon layer skeleton and improves the density of the carbon layer.

[0076] Experimental Group 5 (without methyl methacrylate): The proportions of other materials remained unchanged, but methyl methacrylate was removed and replaced with an equal mass of n-butyl acrylate. The test results were: foaming ratio of 16~19 times, easy collapse of carbon layer, softening and flowing at 300℃ for 25 min, and oxygen index of 30%. This indicates that methyl methacrylate is the key to ensuring the high temperature resistance and rigidity of the coating and preventing softening and flowing.

[0077] Experimental results show that the material ratio of the foamed flame retardant layer 22 is reasonable. By controlling the amount of each material, the design goal of "meeting the foaming ratio standard, dense and stable char layer, high temperature resistance and crack resistance, and excellent flame retardant performance" can be achieved, providing reliable core heat insulation and flame retardant protection for composite wood beams.

[0078] According to the present invention, a fire-retardant coating modified with high ductility for prefabricated composite wood beams is provided. The topcoat 25 is composed of a third film-forming monomer, a vinyl silane coupling agent, a self-crosslinking monomer, and auxiliary agents. The materials are proportioned by weight as follows: methyl methacrylate 30-34 parts, n-butyl acrylate 20-24 parts, acrylic acid 5-7 parts, vinyltrimethoxysilane 4-6 parts, ethyl acetoacetate methacrylate 8-12 parts, initiator 0.8-1.2 parts, dispersant 0.5-0.8 parts, deionized water 15-19 parts, and UV stabilizer 0.3-0.5 parts, for a total weight of 100 parts. This provides the outer layer of the composite fireproof layer 2 with weather resistance, interlayer interface anchoring, and rapid curing at room temperature, making it suitable for factory prefabrication requirements. Methyl methacrylate (MMA) hard monomers enhance the coating's hardness and abrasion resistance, preventing scratches and damage during construction and transportation. n-Butyl acrylate (n-butyl acrylate) soft monomers adjust the coating's flexibility, preventing cracking due to excessive rigidity or changes in ambient temperature. Acrylic acid improves the interfacial adhesion between the coating and the refractory mesh 24, ensuring the topcoat slurry 25 can penetrate the mesh, achieving full interfacial anchoring between the topcoat 25 and the refractory mesh and refractory lining 23. Vinyltrimethoxysilane polymerizes at one end with the film-forming monomer of the topcoat 25 and forms chemical bonds at the other end with the hydroxyl groups on the surfaces of the refractory mesh 24 and refractory lining 23, significantly improving the interfacial bonding between the topcoat 25 and adjacent layers, preventing interlayer debonding, and ensuring the overall integrity of the composite fireproof layer 2. Ethyl acetoacetate (Acetoacetic acid methyl methacrylate) can achieve self-crosslinking polymerization at room temperature, eliminating the need for high-temperature curing, significantly shortening the factory prefabrication cycle, while also improving the density of the topcoat 25, enhancing its water resistance and UV resistance, and extending the service life of the composite fireproof layer 2. Auxiliary agents and initiators promote the full polymerization reaction of each monomer, ensuring rapid curing and shaping of the coating; dispersants ensure uniform mixing of all materials, avoiding sedimentation and stratification, and ensuring a uniform and dense topcoat; UV stabilizers enhance the coating's anti-aging properties, preventing chalking and cracking from prolonged exposure to sunlight; deionized water serves as the dispersion medium, ensuring the coating's application fluidity and storage stability.

[0079] Four sets of comparative experiments were designed using the controlled variable method. Experimental conditions included: identical substrate (refractory mesh 24 bonded to refractory lining board 23), identical construction thickness (5mm), and identical curing environment (25℃, 60% relative humidity, 7 days curing). Only the presence or absence of a single core material was varied. Test indicators included interfacial bonding strength (tensile shear strength), weather resistance (GB / T1865-2009, artificial accelerated aging for 1000h), coating density (water absorption rate), and water resistance (no blistering or peeling after 24h immersion). Specific experimental procedures and results are as follows:

[0080] Experimental group 1 (blank control group) used the following optimal formulation: 34 parts methyl methacrylate, 24 parts n-butyl acrylate, 6 parts acrylic acid, 5 parts vinyltrimethoxysilane, 10 parts ethyl acetoacetate methacrylate, 1.0 part initiator, 0.6 parts dispersant, 19 parts deionized water, and 0.4 parts UV stabilizer, for a total mass of 100 parts. The test results were: interfacial bonding strength 1.5 MPa, weather resistance with no powdering or cracking, water absorption 2.1%, and no blistering or peeling after 24 hours of immersion.

[0081] Experimental Group 2 (without vinyl silane coupling agent): The proportions of other materials remained unchanged, but the coupling agent was removed. The test results were as follows: the interfacial bonding strength was 0.6 MPa (significantly decreased), the weather resistance was not significantly abnormal, the water absorption rate was 2.3%, and local blistering occurred after soaking for 24 hours. This indicates that the coupling agent is the key to improving the interfacial bonding force between the topcoat 25 and the adjacent layers.

[0082] Experimental Group 3 (without self-crosslinking monomer): The proportions of other materials remained unchanged, but this monomer was removed. The test results were: interfacial bonding strength 1.4 MPa, poor weather resistance (powdering and cracking after aging), water absorption rate 3.8%, and slight peeling after soaking for 24 hours. This indicates that the self-crosslinking monomer is the core of improving the density, weather resistance and water resistance of the coating.

[0083] Experimental Group 4 (without methyl methacrylate): The proportions of other materials remained unchanged, but methyl methacrylate was removed and replaced with an equal mass of n-butyl acrylate. The test results were as follows: interfacial bonding strength 1.3 MPa, no obvious abnormalities in weather resistance, water absorption rate 2.5%, insufficient coating hardness, and easy to scratch. This indicates that methyl methacrylate is the key to ensuring the hardness and wear resistance of the topcoat at 25.

[0084] Experimental results show that the material ratio of the topcoat 25 is reasonable. By controlling the amount of each material, the goals of strong interface bonding, excellent weather and water resistance, rapid curing at room temperature, and wear-resistant and dense surface can be achieved, providing reliable outer protection for the composite fireproof layer 2 and extending the overall service life.

[0085] According to the present invention, a fire-retardant modified high-ductility prefabricated composite timber beam is provided, wherein the lower sides of both ends of the glued laminated timber beam 1 are provided with cantilever heads 6, and the lower side of the cantilever heads 6 is provided with compression steel plates 7. The cantilever heads 6 are provided with vertical shear steel plates 8, and the shear steel plates 8 and the compression steel plates 7 are welded together.

[0086] The cantilevered end 6 provides an installation support structure for the glued laminated timber beam 1, adapting to the rapid installation requirements of prefabricated buildings. The compression steel plate 7 can disperse the support reaction force at the beam end, preventing localized pressure failure at the timber beam end. The vertical shear steel plate 8 can significantly improve the shear bearing capacity at the beam end, preventing shear failure at the timber beam end during a fire. The shear steel plate 8 and the compression steel plate 7 are welded together to form a steel-timber composite end structure with overall load-bearing capacity, ensuring the strong node-weak component design at the beam end during a fire.

[0087] According to the present invention, a fire-retardant modified high-ductility prefabricated composite timber beam has a fire-resistant lining plate 23 at the corresponding position of the tension zone in the mid-span of the glued laminated timber beam 1. The fire-resistant lining plate 23 is a segmented structure with a pre-reserved deformation gap between adjacent segments. The deformation gap is filled with an elastic fireproof sealant 9, and the arrangement density of the elastic clips 5 is higher than that of the beam end area.

[0088] The mid-span tension zone is the area with the greatest flexural deformation in the glued laminated timber beam 1 during a fire, and it is also the part where the fireproof layer is most prone to cracking and failure. The segmented fire-resistant lining 23 can release the tensile stress caused by the flexural deformation of the timber beam, preventing the rigid lining from being torn apart. The elastic fireproof sealant 9 between adjacent segments can fill the deformation gaps, and can foam and expand during a fire, always maintaining the integrity of the fire barrier and preventing flames from spreading. The arrangement density of the elastic clips 5 is higher than that in the beam end area, which can improve the fixing force in the large deformation area, prevent the composite fireproof layer 2 from delaminating and falling off during repeated deformation, and further ensure the stability of the fireproof structure.

[0089] The composite timber beam adopts a factory prefabrication + on-site assembly mode. The production steps are as follows: High-strength glued laminated timber (GLLT) substrate GLLT beam 1 is selected, cut and spliced, and then high-pressure glued together. Installation holes are made according to the positions of the limiting slots 3, keeping the surface of GLLT beam 1 rough. The limiting slots 3 are embedded into the holes and fixed with fire-retardant structural adhesive. Heat-insulating sealant 4 is pre-filled into the slots. Anchoring underlayer 21 and foamed flame-retardant layer 22 are sequentially constructed on the rough surface of GLLT beam 1. A fire-resistant lining plate 23 with elastic clips 5 is assembled and fixed by engaging the elastic clips 5 with the limiting slots 3. Fire-resistant mesh fabric 24 is then installed on the outside of the fire-resistant lining plate 23. Finally, a surface coating 25 is applied, completing the prefabrication of the composite fireproof layer 2. Shear-resistant steel plates 8 and compression-resistant steel plates 7 are installed at the ends of GLLT beam 1. Check the engagement strength between the elastic clip 5 and the limiting groove 3, ensuring that the heat insulation sealant 4 tightly wraps around the end of the elastic clip 5 to isolate thermal bridges, achieving a double and firm bond between the composite fireproof layer 2 and the glued laminated timber beam 1. Test the interface bonding strength, fire resistance limit, and other properties to ensure compliance with the requirements for prefabricated building use.

[0090] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A fire-retardant coated, high-ductility prefabricated composite timber beam, characterized in that, Includes glued laminated timber beams and composite fireproof layer; Limiting slots are provided at intervals on both sides and the bottom of the glued laminated timber beam. Limiting fasteners are installed in the limiting slots, and the cavities of the limiting fasteners are filled with heat-insulating sealant. The composite fireproof layer consists of, from the inside out, an anchoring underlayer, a foamed flame-retardant layer, a fire-resistant lining, a fire-resistant mesh, and a topcoat. The anchoring underlayer is bonded to the outer surface of the glued laminated timber beam. The anchoring underlayer contains penetrating anchoring monomers with phosphate ester groups, which penetrate into the pores of the glued laminated timber beam surface and form a penetrating anchoring structure with the cellulose hydroxyl groups of the timber beam. The topcoat slurry penetrates the mesh of the fire-resistant mesh, fills the area of ​​the fire-resistant mesh and the fire-resistant lining, and covers the outer surface. After the topcoat cures, it forms an integrated anchoring structure with the fire-resistant lining and the foamed flame-retardant layer. The fire-resistant lining is equipped with an elastic clip on the side facing the glued laminated timber beam. Each elastic clip corresponds to a limiting clip. The elastic clip is pressed into the limiting clip and locked in place. The limiting platform of the elastic clip presses against the surface of the mesh reinforcement of the fire-resistant mesh. After the elastic clip is inserted into the limiting clip, it squeezes the heat insulation sealant, causing the heat insulation sealant to wrap around the end of the elastic clip and prevent the elastic clip from direct thermal contact with the glued laminated timber beam.

2. The fire-retardant coating-modified high-ductility prefabricated composite timber beam according to claim 1, characterized in that, The limiting slot has a depth of 30-50mm and a diameter of 8-10mm. Adjacent limiting slots are arranged at equal intervals along the length of the glued laminated timber beam, with a spacing of 200-300mm.

3. The fire-retardant coating-modified high-ductility prefabricated composite timber beam according to claim 1, characterized in that, The minimum total design thickness of the composite fireproof layer satisfies the formula: ,in This refers to the minimum total design thickness of the composite fireproof layer. To achieve the target fire resistance limit, This refers to the maximum permissible flexural deformation value of the glued laminated timber beam. This is the conversion factor for the ultimate fire-resistant thickness. Thickness conversion factor for deformation adaptation.

4. The fire-retardant coating-modified high-ductility prefabricated composite timber beam according to claim 3, characterized in that, The conversion factor for the fire-resistant ultimate thickness satisfies the following formula: ,in This is a conversion factor for the standard fire resistance test reference. The thermal conductivity of the reference fireproof material The overall thermal conductivity of the composite fireproof layer is determined by actual measurement. This represents the measured maximum foaming ratio of the foamed flame-retardant layer. The deformation adaptation thickness conversion factor satisfies the formula: ,in To adapt the reference correction factor to the deformation of the wooden structure, The measured ultimate tensile strain of the composite fireproof layer; This is the modulus of elasticity correction factor for the refractory mesh.

5. A fire-retardant coated, modified, high-ductility prefabricated composite timber beam according to claim 1, characterized in that, The anchoring substrate includes a first film-forming monomer and a penetrating anchoring monomer. The first film-forming monomer includes styrene, n-butyl acrylate, and glycidyl acrylate, wherein the mass of n-butyl acrylate is less than the mass of styrene, and the penetrating anchoring monomer is an acrylate monomer containing a phosphate ester group.

6. A fire-retardant coated, modified, high-ductility prefabricated composite timber beam according to claim 1, characterized in that, The limiting clip has a diamond-shaped fastening mechanism at its root, which uses a micro screw to rotate so that the diamond tip presses against the glued laminated timber beam.

7. A fire-retardant coated, modified, high-ductility prefabricated composite timber beam according to claim 1, characterized in that, The foamed flame-retardant layer includes a second film-forming monomer, an internal crosslinking monomer, an intumescent flame-retardant system, inorganic fillers, deionized water, and environmentally friendly additives. The second film-forming monomer is methyl methacrylate, n-butyl acrylate, and acrylic acid. The internal crosslinking monomer is ethylene glycol dimethacrylate. The intumescent flame-retardant system is an acid source ammonium polyphosphate, a carbon source pentaerythritol, microcrystalline cellulose, and a gas source melamine.

8. A fire-retardant coated, modified, high-ductility prefabricated composite timber beam according to claim 1, characterized in that, The topcoat includes a third film-forming monomer, a vinyl silane coupling agent, and a self-crosslinking monomer. The third film-forming monomer is methyl methacrylate, n-butyl acrylate, and acrylic acid. The vinyl silane coupling agent is vinyltrimethoxysilane, and the self-crosslinking monomer is ethyl acetoacetate methacrylate.

9. A fire-retardant coated, modified, high-ductility prefabricated composite timber beam according to claim 1, characterized in that, The glued laminated timber beam has cantilevered ends at both ends, and a compression steel plate is provided under the cantilevered ends. A vertical shear steel plate is provided inside the cantilevered ends, and the shear steel plate and the compression steel plate are welded together.

10. A fire-retardant coated, modified, high-ductility prefabricated composite timber beam according to claim 1, characterized in that, The fire-resistant lining plate at the corresponding position of the tension zone at the mid-span of the glued laminated timber beam is a segmented structure with a pre-reserved deformation gap between adjacent segments. The deformation gap is filled with an elastic fireproof sealant, and the arrangement density of the elastic clips is higher than that of the beam end area.

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