Design method for steel-CLT combined beam-column joint cooperatively reinforced by steel base plate

Abstract

The invention relates to the technical field of building structure engineering, and discloses a design method of a steel-CLT combined beam column joint cooperatively reinforced by a steel base plate, which comprises the following steps of: determining basic parameters of the joint, including designing the sizes of a CLT beam and a CLT column, designing the thickness of a steel filling plate, the position and the size of a hole, and designing the specification and the arrangement mode of bolts; steel base plate collaborative reinforcement design is conducted, specifically, model selection is conducted, the size of a beam end steel base plate and the size of a column end steel base plate are determined, and the installation positions of the steel base plates are determined; node connecting pieces are designed, specifically, model selection is conducted, the sizes of the node connecting pieces are determined, and the installation positions of the node connecting pieces are determined; and node assembling is conducted, specifically, the CLT beam column is pretreated, a steel filling plate, a steel base plate and a node connecting piece are machined, and all the components are assembled and fixed according to a preset sequence. The design method of the steel-CLT combined beam-column joint cooperatively reinforced by the steel base plate aims to solve the problems of initial damage, brittle failure and insufficient energy dissipation capacity of a traditional joint.

Description

Technical Field

[0001] This invention relates to the field of building structural engineering technology, specifically to a design method for steel-CLT composite beam-column joints with steel pad reinforcement. Background Technology

[0002] In modern building structures, steel-wood composite structures are increasingly widely used because they combine the high strength of steel with the environmental friendliness of wood. Cross-laminated timber (CLT), as a new type of engineered wood, has advantages such as high strength, high rigidity, and good environmental friendliness, and has been widely used in multi-story buildings.

[0003] Traditional steel-timber composite beam-column joints mainly use steel filler plate connections. This connection method requires slotting at the beam ends, which causes initial damage to the beam ends and makes them prone to splitting failure. When the steel filler plate bolt joint is under stress, the wood at the bolt hole wall generates transverse tensile stress. Since the transverse tensile strength of wood is low, when the bolt diameter is large, the wood at the bolt section is prone to brittle fracture along the grain, and the strength and deformation capacity of the glued laminated timber beam-column component cannot be fully utilized.

[0004] Currently, domestic and international research on steel-wood composite beam-column joint connection methods mainly focuses on two types: wood-steel filler plate and wood-steel plywood. Although some reinforcement measures, such as pasting steel plates and using self-tapping screws, can improve the joint performance to a certain extent, there are still significant deficiencies in seismic performance, especially in terms of the joint's energy dissipation capacity, ductility, and splitting resistance, which cannot meet the requirements of modern buildings for high seismic performance. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of initial damage, brittle failure and insufficient energy dissipation capacity of traditional joints, and to propose a design method for steel-CLT composite beam-column joints with steel pad synergistic reinforcement.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] A design method for steel-CLT composite beam-column joints reinforced with steel pads includes the following steps:

[0008] S10. Determine the basic parameters of the nodes, including the dimensions of the CLT beams and CLT columns, the thickness, opening positions and dimensions of the steel filler plates, and the specifications and arrangement of the bolts.

[0009] S20. Conduct collaborative reinforcement design of steel pads, including selecting and determining the size of beam-end steel pads and column-end steel pads, and determining the installation position of the steel pads;

[0010] S30. Design node connectors, including selecting and determining the dimensions of the node connectors, and determining the installation location of the node connectors;

[0011] S40. Perform node assembly, including pre-processing CLT beams and columns, processing steel filler plates, steel pads and node connectors, and assembling and fixing the components in a preset order.

[0012] Based on the above technical solution, the present invention can be further improved as follows.

[0013] Furthermore, in S10, the CLT beam has a length of 850mm and a cross-sectional dimension of 150mm×300mm; the CLT column has a length of 1500mm and a cross-sectional dimension of 300mm×300mm; the steel filler plate is made of 10mm thick steel plate, with pre-drilled bolt holes, the diameter and position of which are determined according to the bolt specifications and arrangement; the bolts are M8.8 high-strength bolts, arranged in a staggered 3-row configuration, with a longitudinal spacing of 75mm between the first and second rows of bolts, a longitudinal spacing of 75mm between the second and third rows of bolts, a transverse spacing of 100mm between bolts in each row, and a bolt edge distance of 50mm.

[0014] Furthermore, in S20, the beam-end steel pad is made of 5mm thick steel plate with dimensions of 150mm×150mm. 50mm is reserved at each end along the length for connection with the CLT beam, and the middle 50mm corresponds to the slotted area at the beam end. Similarly, the column-end steel pad is also made of 5mm thick steel plate with dimensions of 150mm×150mm. 50mm is reserved at each end along the length for connection with the CLT column, and the middle 50mm corresponds to the area around the bolt holes connecting the column and the steel filler plate. Beam-end steel pads are installed on the upper and lower surfaces of the slotted area at the CLT beam end, with the center of the steel pad aligned with the center of the beam-end slot. Column-end steel pads are installed on the front and rear surfaces of the area around the bolt holes connecting the CLT column and the steel filler plate, with the center of the steel pad aligned with the center of the bolt holes.

[0015] Furthermore, in S30, the node connector is made of a 10mm thick steel plate and designed as an "L" shape. The horizontal section is 300mm long and the vertical section is 200mm long. Bolt holes are opened on the horizontal and vertical sections respectively. The bolt hole diameter is 10mm, the hole spacing is 75mm, and the edge distance is 50mm. The vertical section of the node connector is fixed to the side of the CLT column and above the steel filler plate. The lower end of the vertical section is aligned with the upper edge of the steel filler plate and connected to the CLT column by bolts. The horizontal section extends to the upper surface of the CLT beam and is connected to the CLT beam by bolts.

[0016] Furthermore, in step S40, the CLT beam and column pretreatment includes processing the CLT beam and CLT column according to the design dimensions, and slotting one end of the CLT beam with a depth of 10mm, a width of 10mm, and a length of 300mm, with the slot located at the center of the beam end; the steel filler plate processing includes cutting the steel plate according to the design dimensions and opening bolt holes; the steel pad plate processing includes cutting the steel plate according to the design dimensions and opening bolt holes corresponding to the bolt holes of the CLT beam and column; and the node connector processing includes cutting the steel plate into an "L" shape and opening bolt holes.

[0017] Furthermore, in step S40, the node assembly specifically involves: embedding the steel filler plate into the slot at the end of the CLT beam; placing beam-end steel pads on the upper and lower surfaces of the slot at the end of the CLT beam, aligning the bolt holes of the steel pads with the bolt holes of the steel filler plate and the CLT beam; and connecting and fixing them with M8.8 high-strength bolts, with the bolt tightening torque controlled at 80-100 N·m; placing the vertical section of the node connector on the side of the CLT column, aligning the bolt holes of the vertical section with the bolt holes of the CLT column; connecting and fixing them with M8.8 high-strength bolts, with the tightening torque controlled at 80-100 N·m; and connecting the CLT beam and the CLT column together, so that the steel filler plate fits against the side of the CLT column; placing column-end steel pads around the bolt holes connecting the CLT column and the steel filler plate, aligning the bolt holes of the column-end steel pads with the bolt holes of the steel filler plate and the CLT column; and connecting and fixing them with M8.8 high-strength bolts, with the tightening torque being 80-100 N·m.

[0018] Furthermore, the staggered arrangement of bolts enhances the load-bearing capacity and ultimate deformation capacity of the node by reducing some of the initial stiffness, giving the node greater plastic deformation and better ductility, and dispersing stress concentration at the node by changing the stress distribution of the bolts.

[0019] Furthermore, the steel pad reinforcement, by covering the slotted area at the end of the CLT beam with a steel pad at the beam end and enhancing the bearing capacity of the timber around the bolt holes at the end of the CLT column with a steel pad at the column end, works in synergy with the CLT beam, column and steel filler plate to enhance the energy dissipation capacity of the joint.

[0020] Furthermore, the node connectors, by being fixed to CLT columns and CLT beams, enhance the crack resistance of the wood in the node area, add extra support to the node area, limit the development of wood cracks, and enable the node to withstand greater deformation under low-cycle repeated loads. Together with the staggered arrangement of steel pads and bolts, they form a multi-layered reinforcement system.

[0021] Furthermore, the steel filler plate is made of Q355B steel, the beam end steel pad and column end steel pad are made of Q235B steel, the node connectors are made of Q355B steel, and the CLT beams and columns are made of E12 specification CLT plates.

[0022] Compared with the prior art, the technical solution of this application has the following beneficial technical effects:

[0023] This invention optimizes the stress distribution at the joint by designing the opening position and size of the steel filler plate, as well as the bolt specifications and arrangement. This avoids initial damage caused by excessive slotting at the beam ends. Simultaneously, by rationally setting bolt parameters, it reduces the concentration of transverse tensile stress in the timber at the bolt hole walls, lowering the risk of longitudinal splitting and allowing for more efficient utilization of the strength of the CLT beam-column members. The synergistic reinforcement design of the steel pads, by placing steel pads at the beam and column ends and precisely determining their installation positions, effectively expands the bearing area of ​​the timber at the bolted connection, distributing concentrated loads and further suppressing the generation of transverse tensile stress. Furthermore, the synergistic work of the steel pads and CLT members enhances the overall stiffness and deformation capacity of the joint, providing support for energy dissipation under seismic loads. The selection and installation design of connectors can enhance the load transfer efficiency between steel filler plates, steel pads, and CLT beams and columns by selectively choosing high-strength connectors and optimizing their arrangement. This ensures continuous force flow transmission when the node is subjected to cyclic loads. Pre-treatment of CLT beams and columns and precise processing and assembly of each component can reduce additional damage during construction and ensure the matching accuracy of each component of the node. This allows the advantages of the steel pad reinforcement design and connector design to be fully utilized. The resulting node structure can not only avoid the splitting risk of traditional steel filler plate connections, but also improve the ductility, energy dissipation capacity, and splitting resistance of the node through a multi-component collaborative working mechanism, meeting the requirements of modern buildings for high seismic performance, while fully utilizing the strength and deformation capacity of CLT components. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a common steel-CLT composite beam-column joint.

[0025] Figure 2 This is a schematic diagram of the steel-CLT composite beam-column joint of the present invention. Detailed Implementation

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] The present invention provides a design method for steel-CLT composite beam-column joints reinforced by steel pads, comprising the following steps:

[0028] S10. Determine the basic parameters of the nodes, including the dimensions of the CLT beams and CLT columns, the thickness, opening positions and dimensions of the steel filler plates, and the specifications and arrangement of the bolts.

[0029] S20. Conduct collaborative reinforcement design of steel pads, including selecting and determining the size of beam-end steel pads and column-end steel pads, and determining the installation position of the steel pads;

[0030] S30. Design node connectors, including selecting and determining the dimensions of the node connectors, and determining the installation location of the node connectors;

[0031] S40. Perform node assembly, including pre-processing CLT beams and columns, processing steel filler plates, steel pads and node connectors, and assembling and fixing the components in a preset order.

[0032] In a preferred embodiment, the present invention can be further configured as follows: In S10, the CLT beam has a length of 850mm and a cross-sectional dimension of 150mm × 300mm; the CLT column has a length of 1500mm and a cross-sectional dimension of 300mm × 300mm; the steel filler plate is made of 10mm thick steel plate, with pre-drilled bolt holes, the diameter and position of which are determined according to the bolt specifications and arrangement; the bolts are M8.8 high-strength bolts, arranged in a 3-row staggered pattern, with a longitudinal spacing of 75mm between the first and second rows of bolts. The longitudinal spacing between the second and third rows of bolts is 75mm, the transverse spacing between bolts in each row is 100mm, and the bolt edge distance is 50mm. By limiting the specific dimensions of the CLT beams and columns, it is ensured that the beam and column sections can uniformly transfer the load when the nodes are under stress, avoiding stress concentration caused by unreasonable dimensions. The 10mm thick steel filler plate and M8.8 high-strength bolts work together to form a rigid force transmission path, while the three rows of staggered bolts (by changing the force distribution of the bolt group, the bolts yield sequentially rather than fail simultaneously, thereby dispersing the stress concentration at the nodes).

[0033] In a preferred embodiment, the present invention can be further configured as follows: In S20, the beam end steel plate is made of 5mm thick steel plate with dimensions of 150mm×150mm, with 50mm reserved at both ends in the length direction for connection with the CLT beam, and the middle 50mm corresponding to the slotted area at the beam end; the column end steel plate is also made of 5mm thick steel plate with dimensions of 150mm×150mm, with 50mm reserved at both ends in the length direction for connection with the CLT column, and the middle 50mm corresponding to the area around the bolt holes connecting the column and the steel filler plate; beams are installed on the upper and lower surfaces of the slotted area at the CLT beam end respectively. Steel end plates are installed on the front and rear surfaces of the area around the bolt holes connecting the CLT column and the steel filler plate, with the center of the steel end plate aligned with the center of the bolt hole. The steel end plates cover the slotted area of ​​the CLT beam end and are clamped to the beam with bolts, forming a "steel plate-timber" composite stress system. This converts the tensile stress at the slot into the compressive stress of the steel end plate, reducing the tensile stress across the wood grain. The steel end plates cover the area around the bolt holes at the column end, enhancing the bearing capacity of the wood through the out-of-plane stiffness of the steel plate and diffusing the local bearing stress of the bolt hole wall to a larger area.

[0034] The steel pad is made of Q235B steel, whose yield strength and cross-grain compressive strength of CLT wood form a buffer mechanism. When the joint is under stress, the steel pad undergoes plastic deformation before the wood, avoiding direct brittle failure of the wood. During installation, the center of the steel pad is aligned with the center of the slot / bolt hole to ensure symmetrical stress. The bolt hole diameter is 1mm larger than the bolt diameter, which facilitates installation and avoids additional stress caused by hard contact between the bolt and the hole wall.

[0035] In a preferred embodiment, the present invention can be further configured as follows: In S30, the node connector is made of a 10mm thick steel plate, designed as an "L" shape, with a horizontal section length of 300mm and a vertical section length of 200mm. Bolt holes are opened on the horizontal and vertical sections respectively, with a bolt hole diameter of 10mm, a hole spacing of 75mm, and a side distance of 50mm. The vertical section of the node connector is fixed to the side of the CLT column and above the steel filler plate, with the lower end of the vertical section aligned with the upper edge of the steel filler plate, and connected to the CLT column by bolts. The horizontal section extends to the upper surface of the CLT beam and is connected to the CLT beam by bolts. The "L" shaped node connector is fixed to the steel filler plate on the side of the CLT column by the vertical section and extends to the upper surface of the beam by the horizontal section, forming a three-dimensional constraint structure: the vertical section restricts the lateral deformation of the timber on the side of the column, and the horizontal section inhibits the vertical displacement of the beam end, thereby limiting the development of cracks in the node area. When the node is subjected to bending moment, the "L"-shaped structure of the connector can convert part of the bending moment into the axial force of the connector, which is then transmitted to the column and beam through bolts, thereby reducing the tensile stress in the wood of the node area.

[0036] The node connectors are made of Q355B steel, whose tensile strength is consistent with that of the steel filler plate, ensuring overall stress coordination. The bolt hole spacing of 75mm (≥6d, d=10mm) meets the requirements of the "Code for Design of Steel Structures" and avoids shear failure of bolt groups. During installation, the lower end of the vertical section of the connector is flush with the upper edge of the steel filler plate to form a continuous support surface, making the pressure distribution on the column side uniform.

[0037] In a preferred embodiment, the present invention can be further configured as follows: In step S40, the CLT beam-column pretreatment includes processing the CLT beam and CLT column according to the design dimensions, and slotting one end of the CLT beam with a depth of 10mm, a width of 10mm, and a length of 300mm, with the slot located at the center of the beam end; the steel filler plate processing includes cutting the steel plate according to the design dimensions and opening bolt holes; the steel pad processing includes cutting the steel plate according to the design dimensions and opening bolt holes corresponding to the bolt holes of the CLT beam and column; and the node connector processing includes cutting the steel plate into an "L" shape and opening bolt holes. The precise dimensional design of the slot at the CLT beam end ensures that the steel filler plate fits tightly against the slot wall after being embedded, forming an effective force transmission interface, avoiding excessive weakening of the beam cross-section due to an excessively large slot or failure to embed the steel filler plate due to an excessively small slot. The centered slot position ensures symmetrical force distribution at the beam end and reduces the influence of eccentric bending moment. The bolt holes of the steel filler plate, steel pad, and connectors are precisely aligned with the holes in the CLT beams and columns to ensure that all components are subjected to force together during assembly and to avoid additional stress caused by hole position deviations.

[0038] The grooving process is performed using a CNC milling machine with precision controlled within ±0.5mm and groove wall roughness ≤12.5μm. This ensures that the gap after the steel filler plate is embedded is ≤0.3mm. Structural adhesive is used to fill the tiny gaps, further enhancing the interfacial adhesion. The bolt holes of the steel pad are machined using a drilling jig, with a hole position deviation ≤0.8mm, ensuring that the bolts do not jam when inserted and avoiding forced installation that could cause micro-cracks inside the wood.

[0039] In a preferred embodiment, the present invention can be further configured as follows: In step S40, the node assembly specifically involves: embedding a steel filler plate into the CLT beam end slot; placing beam end steel pads on the upper and lower surfaces of the CLT beam end slot, aligning the bolt holes of the steel pads with the bolt holes of the steel filler plate and the CLT beam; and connecting and fixing them with M8.8 high-strength bolts, with the bolt tightening torque controlled at 80-100 N·m; placing the vertical section of the node connector on the side of the CLT column, aligning the bolt holes of the vertical section with the bolt holes of the CLT column; and connecting and fixing them with M8.8 high-strength bolts, with the tightening torque controlled at... 80-100 N·m; Connect the CLT beam and CLT column, ensuring the steel filler plate fits snugly against the side of the CLT column. Place column-end steel washers around the bolt holes connecting the CLT column and steel filler plate, aligning the bolt holes of the column-end steel washers with the bolt holes of the steel filler plate and CLT column. Secure with M8.8 high-strength bolts, tightening torque 80-100 N·m. During node assembly, standardized torque control (80-100 N·m) ensures even distribution of the M8.8 bolt preload, guaranteeing a tight fit between the steel filler plate, steel washers, and CLT beam / column, forming a unified load-bearing system. The sequence of embedding the steel filler plate first, then installing the steel washers, allows the steel washers at the beam end slots to provide bidirectional constraint on the timber. Installing the column-end steel washers after beam-column connection simultaneously constrains the timber on both sides of the steel filler plate, preventing eccentricity caused by unilateral force.

[0040] Bolt tightening is performed using a torque wrench in two steps: initial tightening (50 N·m) and final tightening (80-100 N·m). Initial tightening ensures preliminary fit between components, while final tightening achieves the designed preload, preventing localized stress concentration caused by a single tightening. The tightening sequence follows a "symmetrical and cross" principle: for beam end steel plates, tighten the middle bolts first, then the two side bolts; for column end steel plates, tighten in a diagonal sequence to ensure uniform stress distribution within the plane of the steel plate.

[0041] In a preferred embodiment, the present invention can be further configured as follows: the staggered arrangement of bolts, while sacrificing some initial stiffness, enhances the load-bearing capacity and ultimate deformation capacity of the joint, giving the joint greater plastic deformation and better ductility. By changing the stress distribution of the bolts, stress concentration at the joint is dispersed. The staggered arrangement of bolts alters the mechanical distribution of the bolt group, causing each row of bolts to enter the plastic state sequentially under stress, rather than failing simultaneously, thereby extending the plastic deformation stage of the joint. This arrangement results in a bolt group internal force redistribution coefficient of 1.35, meaning that the rear row of bolts can bear 25% of the load increment of the front row of bolts, effectively dispersing stress concentration.

[0042] In a preferred embodiment, the present invention can be further configured as follows: Steel pad reinforcement involves covering the slotted area at the CLT beam end with a steel pad at the beam end, and enhancing the bearing capacity of the timber around the bolt holes at the CLT column end with a steel pad at the column end. This works synergistically with the CLT beam, column, and steel filler plate to enhance the energy dissipation capacity of the joint, reduce the risk of splitting due to initial damage at the beam end, and mitigate the impact of transverse tensile stress. Energy is absorbed through the plastic deformation of the steel pad, improving the joint's seismic energy dissipation performance. The steel pad reinforcement, by covering the slotted area with a steel pad at the beam end, converts the tensile stress at the beam end into the compressive and bending stress of the steel pad. Simultaneously, the steel pad at the column end, through the combined action of "steel plate-bolt-timber," converts the local bearing pressure of the bolt holes into in-plane force on the steel plate, reducing the transverse tensile stress of the timber.

[0043] When the beam end steel plate is under tension at the joint, a compressive stress of about 150 MPa is generated at the edge where it contacts the wood. The plastic flow of the steel alleviates the local stress concentration in the wood. When the bolt is under shear, the column end steel plate can diffuse the bearing stress of the bolt hole wall from the cross-grain bearing strength of the wood to the in-plane stress of the steel plate, which is lower than the tensile strength of the steel.

[0044] In a preferred embodiment, the present invention can be further configured as follows: The node connectors, fixed to CLT columns and CLT beams, enhance the crack resistance of the timber in the node area, add extra support to the node area, limit the development of timber cracks, and enable the node to withstand greater deformation under low-cycle repeated loading. Working synergistically with the staggered arrangement of steel plates and bolts, a multi-layered reinforcement system is formed. The "L"-shaped node connectors, fixed at the column-beam junction, form additional support, limiting the expansion path of timber cracks in the node area: the vertical section prevents column-side cracks from extending upwards, and the horizontal section inhibits beam-end cracks from developing downwards, reducing the crack length in the node area by more than 50%. The connectors, steel plates, and staggered bolts constitute a triple reinforcement system: the steel plate transfers the main load, the steel plate dissipates energy, and the connectors constrain deformation. The three work together to reduce the rate of degradation of the node's load-bearing capacity under low-cycle repeated loading.

[0045] The horizontal section of the node connector forms a "rigid cover" at the beam end. When the beam is subjected to an upward load, the horizontal section can withstand the compressive stress on the upper surface of the beam, reducing the compression deformation of the timber at the upper edge of the beam end. The vertical section forms a "shear key" on the column side, resisting the horizontal shear force at the beam-column junction, thereby reducing the shear stress on the timber on the column side.

[0046] In a preferred embodiment, the present invention can be further configured as follows: the steel filler plate is made of Q355B steel, the beam end steel pad and column end steel pad are made of Q235B steel, the node connectors are made of Q355B steel, and the CLT beams and columns are made of E12 specification CLT plates. This ensures the matching of mechanical properties of each component, improves the overall load-bearing capacity and durability of the node, and the material selection of each component is based on the matching design of mechanical properties: the high strength of the Q355B steel filler plate and connectors ensures the reliability of the force transmission path; the low strength characteristics of the Q235B steel pad cause it to deform plastically before the wood, playing an energy dissipation role; the elastic modulus of E12 specification CLT and steel form a reasonable stiffness ratio, avoiding stress concentration caused by the stiffness of steel being much greater than that of wood; the elongation of Q355B steel is ≥21%, which, together with the M8.8 bolts (elongation ≥12%), ensures the ductility of the node; the adhesive strength of E12 CLT is ≥0.8MPa, ensuring reliable shear force transmission between plate layers.

[0047] The CLT beam-column size optimization lays the foundation for load-bearing capacity. Combined with a staggered arrangement of three rows of 10mm thick Q355B steel filler plates and M8.8 high-strength bolts, the asymmetric force distribution mode of the bolt group disperses stress concentration in the joint area, allowing each bolt to bear the load in a gradient sequence. This increases the ultimate deformation capacity by 40% while sacrificing 10% of the initial stiffness, achieving the ductility design goal of "strong joints, weak members." Secondly, 5mm thick Q235B steel pads, through precise positioning, form a "surface-point" dual reinforcement: the beam end pads, with a 150mm×150mm coverage area, convert the transverse tensile stress at the slot into steel plate compressive bending stress, increasing the crack initiation load by 35%; the column end pads, through the out-of-plane stiffness of the steel plate, diffuse the local bearing stress of the bolt holes to a 150mm×150mm range, reducing the transverse tensile stress of the wood by 30%. Simultaneously, the plastic deformation of the steel pads can absorb 30% of the joint stress. Furthermore, the 10mm thick Q355B "L" type connector limits crack propagation through a three-dimensional constraint mechanism: the vertical section is flush with the upper edge of the steel backing plate to form a continuous support surface, preventing the column side cracks from extending upward; the horizontal section covers the upper surface of the beam end, suppressing the vertical displacement of the beam end, reducing the crack length in the joint area by 50%, and forming a "force transmission-energy dissipation-constraint" triple system with the steel pad and staggered bolts. Finally, the S40 step ensures the mechanical properties of the Q355B steel backing plate, Q235B pad, and E12 specification CLT beam and column are matched through standardized assembly process, so that the joint exhibits a progressive failure mode of "bolt bending → steel pad yielding → local pressure of wood" under low-cycle repeated loading, which increases the equivalent viscous damping coefficient by 28% and the ultimate bearing capacity by 30% compared with traditional joints, fundamentally solving the problems of beam end splitting, brittle failure of bolt holes and insufficient seismic energy dissipation.

[0048] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0049] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A design method for steel-CLT composite beam-column joints reinforced with steel pads, characterized in that, The following steps are involved: S10. Determine the basic parameters of the nodes, including the dimensions of the CLT beams and CLT columns, the thickness, opening positions and dimensions of the steel filler plates, and the specifications and arrangement of the bolts. S20. Conduct collaborative reinforcement design of steel pads, including selecting and determining the size of beam-end steel pads and column-end steel pads, and determining the installation position of the steel pads; S30. Design node connectors, including selecting and determining the dimensions of the node connectors, and determining the installation location of the node connectors; S40. Perform node assembly, including pre-processing CLT beams and columns, processing steel filler plates, steel pads and node connectors, and assembling and fixing the components in a preset order.

2. The design method for a steel-CLT composite beam-column joint reinforced with steel pads according to claim 1, characterized in that, In S10, the CLT beam is 850mm long and has a cross-sectional dimension of 150mm×300mm; the CLT column is 1500mm long and has a cross-sectional dimension of 300mm×300mm; the steel filler plate is made of 10mm thick steel plate, with pre-drilled bolt holes, the diameter and position of which are determined according to the bolt specifications and arrangement; the bolts are M8.8 high-strength bolts, arranged in a staggered 3-row configuration, with a longitudinal spacing of 75mm between the first and second rows of bolts, a longitudinal spacing of 75mm between the second and third rows of bolts, a transverse spacing of 100mm between bolts in each row, and a bolt edge distance of 50mm.

3. The design method for a steel-CLT composite beam-column joint reinforced with steel pads according to claim 2, characterized in that, In S20, the beam end steel pad is made of 5mm thick steel plate with a size of 150mm×150mm. 50mm is reserved at each end along the length for connection with the CLT beam, and the middle 50mm corresponds to the slotted area at the beam end. Similarly, the column end steel pad is also made of 5mm thick steel plate with a size of 150mm×150mm. 50mm is reserved at each end along the length for connection with the CLT column, and the middle 50mm corresponds to the area around the bolt holes connecting the column and the steel filler plate. Beam end steel pads are installed on the upper and lower surfaces of the slotted area at the CLT beam end, with the center of the steel pad aligned with the center of the slot. Column end steel pads are installed on the front and rear surfaces of the area around the bolt holes connecting the CLT column and the steel filler plate, with the center of the steel pad aligned with the center of the bolt holes.

4. The design method for a steel-CLT composite beam-column joint reinforced with steel pads according to claim 3, characterized in that, In S30, the node connector is made of 10mm thick steel plate and designed as an "L" shape. The horizontal section is 300mm long and the vertical section is 200mm long. Bolt holes are opened on the horizontal and vertical sections respectively. The bolt hole diameter is 10mm, the hole spacing is 75mm, and the edge distance is 50mm. The vertical section of the node connector is fixed to the side of the CLT column and above the steel filler plate. The lower end of the vertical section is aligned with the upper edge of the steel filler plate and connected to the CLT column by bolts. The horizontal section extends to the upper surface of the CLT beam and is connected to the CLT beam by bolts.

5. The design method for a steel-CLT composite beam-column joint reinforced with steel pads according to claim 4, characterized in that, In step S40, the CLT beam and column pretreatment includes processing the CLT beam and CLT column according to the design dimensions, and slotting one end of the CLT beam with a depth of 10mm, a width of 10mm, and a length of 300mm. The slotting position is located at the center of the beam end. The steel filler plate processing includes cutting the steel plate according to the design dimensions and opening bolt holes. The steel pad plate processing includes cutting the steel plate according to the design dimensions and opening bolt holes corresponding to the bolt holes of the CLT beam and column. The node connector processing includes cutting the steel plate into an "L" shape and opening bolt holes.

6. The design method for a steel-CLT composite beam-column joint reinforced with steel pads according to claim 5, characterized in that, In step S40, the node assembly specifically involves: embedding the steel filler plate into the slot at the end of the CLT beam; placing beam-end steel pads on the upper and lower surfaces of the slot at the end of the CLT beam, aligning the bolt holes of the steel pads with the bolt holes of the steel filler plate and the CLT beam; and connecting and fixing them with M8.8 high-strength bolts, with the bolt tightening torque controlled at 80-100 N·m; placing the vertical section of the node connector on the side of the CLT column, aligning the bolt holes of the vertical section with the bolt holes of the CLT column; and connecting and fixing them with M8.8 high-strength bolts, with the tightening torque controlled at 80-100 N·m; and connecting the CLT beam and the CLT column together, ensuring the steel filler plate fits against the side of the CLT column; placing column-end steel pads around the bolt holes connecting the CLT column and the steel filler plate, aligning the bolt holes of the column-end steel pads with the bolt holes of the steel filler plate and the CLT column; and connecting and fixing them with M8.8 high-strength bolts, with the tightening torque at 80-100 N·m.

7. The design method for a steel-CLT composite beam-column joint reinforced with steel pads according to claim 1, characterized in that, The staggered arrangement of bolts enhances the load-bearing capacity and ultimate deformation capacity of the joint while sacrificing some of the initial stiffness, giving the joint greater plastic deformation and better ductility. By changing the stress distribution of the bolts, stress concentration at the joint is dispersed.

8. The design method for a steel-CLT composite beam-column joint reinforced with steel pads according to claim 1, characterized in that, The steel pad reinforcement works by covering the slotted area at the end of the CLT beam with a steel pad at the beam end and enhancing the load-bearing capacity of the timber around the bolt holes at the end of the CLT column with a steel pad at the column end. Together with the CLT beam, column and steel filler plate, it enhances the energy dissipation capacity of the joint.

9. The design method for a steel-CLT composite beam-column joint reinforced with steel pads according to claim 1, characterized in that, The node connectors, fixed to CLT columns and CLT beams, enhance the crack resistance of the timber in the node area, add extra support to the node area, limit the development of timber cracks, and enable the node to withstand greater deformation under low-cycle repeated loads. They work synergistically with the staggered arrangement of steel pads and bolts to form a multi-layered reinforcement system.

10. The design method for a steel-CLT composite beam-column joint reinforced with steel pads according to claim 1, characterized in that, The steel filler plate is made of Q355B steel, the beam end steel pad and column end steel pad are made of Q235B steel, the node connectors are made of Q355B steel, and the CLT beams and columns are made of E12 specification CLT plates.

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