A post-added steel structure cantilever platform node structure and a construction method thereof

Abstract

The application relates to the technical field of steel structure construction engineering, in particular to a post-added steel structure cantilever platform node structure and a construction method, which takes the original column of a building as a connecting base and comprises an expansion anchor plate, a steel plate connecting piece, a cantilever steel beam, a base anchor bolt assembly and a tension anchor bolt assembly; the expansion anchor plate is fixedly attached to the connecting side surface of the original column of the building; the steel plate connecting piece is vertically arranged on the side of the expansion anchor plate far from the original column of the building; the connecting end of the cantilever steel beam is fixedly connected with the steel plate connecting piece; the base anchor bolt assembly comprises a plurality of anchor bolts which are vertically arranged and anchored in the original column of the building, and the screw rod ends of the anchor bolts pass through the expansion anchor plate and are locked by nuts; the tension anchor bolt assembly comprises a plurality of tension anchor bolts which are vertically arranged and anchored in the original column of the building and located above the base anchor bolt assembly, and the screw rod ends of the tension anchor bolts pass through the expansion anchor plate and are locked by nuts.

Description

Technical Field

[0001] This invention belongs to the field of steel structure addition and renovation technology in building engineering, specifically involving a post-added steel structure cantilever platform node structure, which is particularly suitable for the node connection and reinforcement of post-added steel structure cantilever platforms on existing reinforced concrete columns or steel columns of buildings. It can be applied to the addition projects of cantilever platforms, cantilever walkways, cantilever viewing facilities and other addition projects on the facades of residential, commercial and public buildings. Background Technology

[0002] With the increasing demand for building function upgrades and renovations, adding steel structure cantilever platforms to existing buildings has become a common engineering practice. Steel structures are widely used in the construction of cantilever platforms due to their light weight, ease of construction, and high load-bearing capacity. The node connection structure of the cantilever platform is the core load-bearing component of the entire cantilever system; its load-bearing capacity, stability, and resistance to damage directly determine the safety of the cantilever platform in use.

[0003] The traditional construction method for adding a cantilevered platform node to a steel structure mainly includes the following steps: First, drill holes in the existing columns of the building and insert chemical anchors to achieve foundation anchoring; then, fit the steel plate connectors into the chemical anchors and fix them as transitional components connecting the cantilevered steel beam and the column; next, hoist the cantilevered steel beam to the steel plate connector and fix the web of the steel beam to the steel plate connector with high-strength bolts; finally, weld the flange of the steel beam to the steel plate connector using equal-strength penetration welding to form a complete node connection structure.

[0004] This traditional joint structure has a core structural design flaw in practical use: During operation, the cantilever platform is subjected to live loads, wind loads, and its own weight, resulting in significant bending stress at the joint. Under combined bending and torsional stress, the tensile force at the joint is highly concentrated on the upper chemical bolts / high-strength bolts, while the lower bolts bear only minor pressure or almost no stress, creating a "single-row bolt primary tensile bearing" stress pattern. Furthermore, the bond strength between the chemical bolts and the original column, as well as the tensile strength of the bolts themselves, have limits. When the load on the cantilever platform exceeds the design value, or when bolt fatigue or aging of the chemical bond layer occurs after long-term use, the upper tensile bolts are highly susceptible to pull-out failure. This failure is sudden and complete, without any prior warning. Once bolt pull-out occurs, the entire cantilever beam will instantly detach from the column, directly causing the cantilever platform to fall, posing an extremely high safety risk.

[0005] To address this issue, some existing engineering practices simply increase the number of upper bolts or enlarge their specifications. However, this approach only improves the tensile strength to a certain extent and does not fundamentally change the stress pattern of "tension concentration." The bolt group is still under overall tension, and if one bolt fails, it will trigger a chain reaction of failures in the remaining bolts, still failing to avoid the risk of overall instability. Other practices involve adding welded ribs between the steel beam and the column to try to improve the bending resistance of the beam end. However, the ribs can only disperse the local stress of the steel beam and cannot solve the core problem of tension concentration in the anchor bolts. Furthermore, the additional welding will increase stress concentration at the joint, easily causing welding cracks, and after long-term use, secondary safety hazards such as weld cracking are likely to occur.

[0006] In summary, the existing post-added steel cantilever platform node structure has the following technical problems: The stress distribution mode is unreasonable; under bending, the tensile force is highly concentrated on the upper bolts, making them prone to pull-out failure, which is sudden and systemic, resulting in poor safety protection; local optimization is achieved only by increasing the number / specification of bolts and adding welded ribs, without optimizing the stress distribution from multiple dimensions such as node anchoring, steel beam end bearing, and column bonding, thus failing to fundamentally solve the problems of tensile force concentration and overall instability; the connection between the node and the original building columns relies solely on bolt anchoring without additional bonding and tightening measures, easily leading to gaps between the anchor plate and the column surface, resulting in discontinuous stress transmission and anchor bolt loosening after long-term use; the steel beam ends lack targeted bending reinforcement structures, making stress concentration prone to occur at the connection between the beam end and the anchor plate, causing localized deformation of the steel beam or weld cracking.

[0007] Therefore, there is an urgent need to develop a new type of post-added steel structure cantilever platform node structure. The system should be designed systematically from aspects such as stress mode optimization, multiple anchoring protection, steel beam end bearing reinforcement, and integrated fixing of anchor plates and columns to solve the problems of tensile concentration, easy pull-out, and poor overall stability of traditional nodes, thereby improving the safety and durability of post-added steel structure cantilever platforms. Summary of the Invention

[0008] The purpose of this invention is to overcome the defects of the prior art and provide a post-added steel structure cantilever platform node structure. Through multiple stress optimizations and dual safety guarantees, it solves the technical problem that when traditional nodes are subjected to bending, the tensile force is concentrated on the upper bolts, which is prone to being pulled out and causing overall failure.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0010] As one aspect of the present invention, a post-added steel structure cantilever platform node structure is provided, using the original building columns as the connection foundation, including an extended anchor plate, a steel plate connector, a cantilever steel beam, a foundation anchor bolt assembly, and a tension anchor bolt assembly; the extended anchor plate is fitted and fixed to the connection side of the original building columns; the steel plate connector is vertically arranged on the side of the extended anchor plate away from the original building columns; the connection end of the cantilever steel beam is fixedly connected to the steel plate connector; the foundation anchor bolt assembly includes multiple anchor bolts, which are arranged vertically and anchored in the original building columns, and the screw end of the anchor bolt passes through the extended anchor plate and is locked with a nut; the tension anchor bolt assembly includes multiple tension anchor bolts, which are arranged vertically and anchored in the original building columns, and are located above the foundation anchor bolt assembly, and the screw end of the tension anchor bolt passes through the extended anchor plate and is locked with a nut.

[0011] In this technical solution, the extended anchor plate is fitted and fixed to the connecting side of the original column of the building, serving as the load-bearing base of the entire node structure. This increases the contact area with the column, allowing the node stress to be transferred to the column more evenly. Steel plate connectors are vertically welded to the extended anchor plate, providing a foundation for the installation and connection of the cantilevered steel beam. The foundation anchor bolt assembly is vertically arranged and anchored into the column, and the extended anchor plate is locked with nuts, achieving foundation anchoring between the node and the column. To address the technical problem of traditional nodes where tensile force is highly concentrated in the upper single row of bolts under bending, leading to easy pull-out failure, this invention adds a tension anchor bolt assembly above the foundation anchor bolt assembly, forming a two-row tension anchor bolt structure. When the node is subjected to bending and tensile force, the tensile force is shared by the upper and lower rows of anchor bolts, achieving uniform distribution of tensile stress. This avoids the defect of concentrated tension in a single row of bolts, significantly reducing the probability of anchor bolt pull-out failure. Even if some anchor bolts experience fatigue, the remaining anchor bolts can continue to bear tension, eliminating the risk of cascading failure and improving the pull-out safety of the node.

[0012] In some embodiments, the technical solution of this application further includes a haunch structure, which is composed of a triangular stiffening plate and a trapezoidal stiffening plate. One end of the trapezoidal stiffening plate of the haunch structure is disposed at the top of the cantilever steel beam, and the other end of the trapezoidal stiffening plate of the haunch structure is connected to the extended anchor plate. The first side of the triangular stiffening plate of the haunch structure is welded and fixed to the upper flange of the cantilever steel beam, the second side of the triangular stiffening plate of the haunch structure is connected to the extended anchor plate, and the third side of the triangular stiffening plate of the haunch structure is connected to the hypotenuse of the trapezoidal stiffening plate.

[0013] In this technical solution, the haunch structure is composed of a triangular stiffening plate and a trapezoidal stiffening plate, and its shape conforms to the law of force transmission. To address the technical problem of stress concentration at the connection between the cantilever steel beam end and the steel plate connector, leading to localized deformation of the steel beam or weld cracking, this invention provides a haunch structure at the top of the connection end of the cantilever steel beam. This haunch structure is simultaneously welded and fixed to the upper flange and extended anchor plate of the cantilever steel beam, as well as to the triangular and trapezoidal stiffening plates; forming an integrated bending reinforcement system. This effectively improves the bending stiffness and load-bearing capacity of the steel beam end, allowing bending stress to be evenly transferred along the stiffening plate to the steel plate connector and extended anchor plate, dispersing stress concentration at the beam end connection, preventing localized deformation of the steel beam or weld cracking, and improving the overall load-bearing performance of the joint.

[0014] In some embodiments, the technical solution of this application further includes an angle steel enclosure, which is set around the outer perimeter of the original column of the building, and one end of the angle steel enclosure is welded and fixed to the edge of the extended anchor plate to form a closed enclosure structure.

[0015] In this technical solution, an angle steel sleeve is set around the outer perimeter of the column and welded to the edge of the extended anchor plate to form a closed enclosure structure. To address the technical problem of relying solely on bolt anchoring for the connection between the node and the column, and the potential for gaps between the anchor plate and the column surface leading to discontinuous stress transmission, this invention incorporates an angle steel sleeve, expanding the connection between the extended anchor plate and the column from a unidirectional fit to a circumferential enclosure. This structure allows the stress at the node to be evenly transmitted to the entire cross-section of the original column through the extended anchor plate and the angle steel sleeve, rather than concentrating at the anchor bolt anchoring point. This avoids excessive local stress in the column, preventing concrete cracking or loosening, and achieving integrated stress transmission.

[0016] In some embodiments, a clamping anchor is provided on the angle steel sleeve, the screw end of the clamping anchor passes through the angle steel sleeve and abuts against the surface of the original column of the building, and is locked by a nut.

[0017] In this technical solution, the screw end of the clamping anchor bolt passes through the angle steel sleeve and directly abuts against the column surface. To further ensure a tight fit between the angle steel sleeve and the column surface and prevent anchor plate loosening due to gaps, the present invention provides clamping anchor bolts on the angle steel sleeve. By tightening the nut of the clamping anchor bolt, mechanical clamping is formed between the angle steel sleeve and the column surface, eliminating the initial gap between the angle steel sleeve and the column, ensuring the continuity of stress transmission, and providing good sealing conditions for subsequent structural adhesive grouting.

[0018] In some embodiments, structural adhesive is injected into the gaps between the extended anchor plate and the original building columns, as well as the gaps between the angle steel sleeve and the original building columns.

[0019] In this technical solution, structural adhesive is injected into all gaps between the extended anchor plate and the column, as well as between the angle steel sleeve and the column. To address the technical problems of anchor bolts loosening easily after long-term use and poor overall joint stability, this invention adds structural adhesive bonding to the mechanical anchoring of the anchor bolts. The adhesive layer formed after the structural adhesive cures can bear part of the tensile and shear stresses, forming a dual force-bearing system with the anchor bolt anchoring, significantly improving the overall stability of the joint. Even if the anchor bolts loosen slightly, the adhesive layer and the angle steel sleeve can still ensure the reliability of the joint connection, providing time for safety warnings and maintenance, and achieving dual safety protection.

[0020] In some embodiments, the web of the connecting end of the cantilever steel beam is fixedly connected to the steel plate connector by multiple high-strength bolts, and the flange of the connecting end of the cantilever steel beam is fixedly welded to the steel plate connector by equal-strength penetration welding.

[0021] In this technical solution, the cantilever steel beam and steel plate connector employ a dual fixing method: web plate bolt connection and flange welding connection. To address the technical problem of insufficient connection strength and susceptibility to connection failure between the cantilever steel beam and steel plate connector, this invention uses a combination of bolted and welded connections. The web is connected with high-strength bolts, facilitating on-site installation and adjustment, and the bolted connection offers good shear and fatigue resistance. The flanges are welded using equal-strength penetration welding, achieving a connection with the base material of equal strength and ensuring the continuity of flange stress under bending moment. These two connection methods complement each other, jointly ensuring the reliability of the connection between the cantilever steel beam and the core of the node.

[0022] In some embodiments, the anchors of the base anchor assembly are chemical bolts, numbering 4 to 6, with specifications of M20 to M24, and an effective anchoring depth of not less than 15d, where d is the diameter of the chemical bolt thread; the number of tension anchors in the tension anchor assembly is the same as the number of chemical bolts, with the same specifications, and the vertical spacing between the tension anchors and the base anchor assembly is 100 to 150 mm.

[0023] In this technical solution, the number, specifications, anchoring depth, and spacing of the anchors are optimally defined. To ensure sufficient load-bearing capacity of the anchor group and to ensure that the upper and lower rows of anchors can work together and evenly distribute the tensile force, the present invention sets the number of both foundation anchors and tension anchors to 4-6, using high-strength anchors of M20-M24 specifications to ensure sufficient tensile load-bearing capacity. The effective anchoring depth is not less than 15d, ensuring the anchoring reliability of the anchors in the concrete. A vertical spacing of 100-150mm is set between the upper and lower rows of anchors, which not only ensures sufficient distance between the two rows of anchors to distribute the tensile force, but also avoids the problem of excessively large extended anchor plate size caused by excessive spacing, making the stress distribution more reasonable.

[0024] In some embodiments, the thickness of the triangular stiffening plate and trapezoidal stiffening plate of the haunch structure is 16~20mm, and the welding of the haunch structure to the extended anchor plate and the cantilever steel beam is done by fillet weld with a weld leg size of 8-12mm.

[0025] In this technical solution, the plate thickness and weld dimensions of the haunch structure are optimally defined. To ensure sufficient rigidity and load-bearing capacity of the haunch structure, while also ensuring the connection strength with surrounding components, the thickness of the triangular and trapezoidal stiffening plates is set to 16-20 mm, guaranteeing the stiffening plates' own bending and shear resistance. Fillet welds are used with a weld leg size of 8-12 mm, ensuring sufficient load-bearing capacity and effectively transferring stress between the haunch structure and the steel plate connectors and cantilever beams, preventing weld cracking.

[0026] In some embodiments, the angle steel enclosure is made of equilateral angle steel with specifications of L100×10~L125×12 and material of Q355B low alloy high strength structural steel; when the original column of the building is a rectangular column, the angle steel enclosure is made of four angle steels spliced ​​together, and the adjacent angle steels are fixed by bevel welding; when the original column of the building is a circular column, the angle steel enclosure is made of curved angle steel spliced ​​together.

[0027] In this technical solution, the selection of materials, specifications, and splicing methods for the angle steel enclosure are optimized and limited. To ensure that the angle steel enclosure has sufficient strength and rigidity, while also being adaptable to existing columns with different cross-sectional shapes, this invention uses equilateral angle steel made of Q355B low-alloy high-strength structural steel, with specifications ranging from L100×10 to L125×12, ensuring the load-bearing capacity of the angle steel enclosure itself. For rectangular columns, four angle steels are spliced ​​together and fixed by bevel welding to form an enclosure structure that matches the rectangular column; for circular columns, curved angle steels are spliced ​​together, allowing the angle steel enclosure to fit tightly against the outer curved surface of the circular column. This adaptable design allows the node structure of this invention to be applied to columns with various cross-sectional shapes, exhibiting strong versatility.

[0028] As another aspect of the present invention, a construction method for a post-added steel structure cantilever platform node structure is provided, comprising the following steps:

[0029] a. Base treatment: Clean the connecting sides and outer surfaces of the original building columns, remove impurities and roughen the surface;

[0030] b. Drilling and anchoring: Mark the drilling positions on the existing columns of the building, clean the dust in the holes after drilling, and plant the anchors of the foundation anchor bolt assembly and the tension anchors respectively. The anchoring is completed after the adhesive has cured.

[0031] c. Install the extension anchor plate and steel plate connector: fit the integrated welded part of the extension anchor plate and steel plate connector into the bolt end of the anchor bolt and tension anchor bolt of the foundation anchor bolt assembly, adjust the position and initially tighten the nut;

[0032] d. Hoisting and connecting the cantilever steel beam: Hoist the cantilever steel beam so that the web of the connecting end of the cantilever steel beam fits into the steel plate connector. Insert high-strength bolts for initial tightening. Weld the flange of the connecting end of the cantilever steel beam to the steel plate connector to form an equal-strength penetration weld. After the weld is inspected and qualified, tighten the high-strength bolts for the final tightening.

[0033] e. Welding of the haunch structure: Install the haunch structure by welding and fixing the triangular stiffening plate and trapezoidal stiffening plate of the haunch structure to the cantilever steel beam, the extended anchor plate, and the triangular stiffening plate and trapezoidal stiffening plate, respectively;

[0034] f. Angle steel sleeve fabrication and installation: Prefabricate and install angle steel sleeves, weld the angle steel sleeves to the extended anchor plates to form a closed enclosure structure, install and tighten the clamping anchor bolts so that the screw end of the clamping anchor bolts abuts against the surface of the original column of the building.

[0035] g. Structural adhesive injection: Low-pressure grouting equipment is used to inject structural adhesive into the gap between the extended anchor plate and the original building column, as well as the gap between the angle steel sleeve and the original building column, to ensure that the structural adhesive is fully injected;

[0036] h. Curing and tightening: After the structural adhesive has cured to the design strength, all nuts of the anchor bolts, tension anchor bolts, compression anchor bolts and high-strength bolts of the foundation anchor bolt assembly shall be tightened again.

[0037] i. Corrosion protection: Apply anti-corrosion coating to the welded joints, bolted connections, and exposed steel surfaces of the node structure.

[0038] In this technical solution, to ensure the accurate construction of the node structure according to design requirements and to achieve the expected load-bearing performance and safety assurance, this invention provides a complete construction method. This method first ensures the column surface meets the structural adhesive bonding requirements through base treatment; then, it drills and anchors to complete the installation of anchor bolts; next, it installs the integrated structure of the extended anchor plate and steel plate connector; subsequently, it hoists the cantilevered steel beam and completes bolt connections and flange welding; then, it installs a haunch structure to enhance the beam end's bending resistance; next, it installs an angle steel sleeve and tightens the anchor bolts to form a closed enclosure structure; then, it injects structural adhesive to achieve bonding and fixation; after the structural adhesive cures, all fasteners are retightened a second time to eliminate loosening that may be caused by the curing shrinkage of the structural adhesive; finally, it performs anti-corrosion treatment to ensure the durability of the node structure. The entire construction method has a reasonable procedure, is easy to operate, can guarantee the construction quality of the node structure, and achieves the various technical effects of this invention.

[0039] This invention provides a post-added steel structure cantilever platform node structure and construction method, which has the following beneficial effects:

[0040] 1. The stress distribution mode of the node is optimized, fundamentally solving the problem of tensile force concentration: This invention adds a row of tension anchors to the traditional foundation anchors, forming a two-row tension anchor structure. When the node is subjected to bending and tensile force, the tensile force is borne by the two rows of anchors, realizing the uniform distribution of tensile stress. This avoids the defect of concentrated tension in a single row of bolts, greatly reducing the probability of anchor pull-out failure. Even if some anchors become fatigued, the remaining anchors can still continue to bear tension, without the risk of chain failure, thus improving the pull-out safety of the node.

[0041] 2. Enhanced bending resistance of steel beam ends and reduced local stress concentration: This invention features a haunch structure composed of triangular and trapezoidal stiffening plates at the top of the cantilever steel beam connection ends. The haunch structure, together with the upper flange of the steel beam and the extended anchor plate connector, forms an integrated bending reinforcement system, effectively improving the bending stiffness and load-bearing capacity of the steel beam ends, dispersing the stress at the connection between the beam ends and the steel plate connectors, and preventing local deformation or weld cracking of the steel beam. At the same time, the design of the haunch structure conforms to the law of force transmission, so that the bending stress is evenly transmitted to the extended anchor plate along the stiffening plate, improving the overall stress performance of the joint.

[0042] 3. A dual safety guarantee is set up, realizing the combination of anchor bolt anchoring and adhesive fixation: The connection between the node and the original column of the building in this invention not only relies on the mechanical anchoring of the foundation anchor bolt assembly and the tension anchor bolt assembly, but also achieves the adhesive fixation of the steel and the column by injecting structural adhesive into the gap between the extended anchor plate, the angle steel sleeve and the column. The adhesive layer formed after the structural adhesive cures can bear part of the tensile stress and shear stress, forming a dual force system with the anchor bolt anchoring; at the same time, the angle steel sleeve is pressed tightly against the column surface by pressing the anchor bolt, further ensuring the fit between the extended anchor plate and the column, and avoiding the anchor plate loosening. The dual safety guarantee greatly improves the overall stability of the node. Even if the anchor bolt loosens slightly, the adhesive layer and the angle steel sleeve can still ensure the connection reliability of the node, providing time for safety warning and maintenance.

[0043] 4. The integrated connection between the node and the column is achieved, improving the continuity of stress transmission: The extended anchor plate of this invention increases the contact area with the column. Combined with the closed enclosure structure formed by the angle steel sleeve, the stress of the node can be evenly transmitted to the entire cross section of the original column through the extended anchor plate and the angle steel sleeve, rather than being concentrated at the anchor bolt anchor point. This avoids concrete cracking or loosening caused by excessive local stress in the column. At the same time, the filling of structural adhesive eliminates the gap between the anchor plate, angle steel and column, ensuring the continuity of stress transmission and improving the collaborative working ability of the node and the column.

[0044] 5. Convenient construction and strong adaptability, meeting the engineering needs of adding to existing buildings: All components of the node structure of this invention can be prefabricated in the factory. On-site installation only requires hoisting, welding, anchor bolt installation and structural adhesive injection. The construction process is simple and does not require large-scale excavation or reinforcement of the original building columns, resulting in minimal damage to the original building structure. At the same time, the angle steel sleeve can be customized according to the cross-sectional shape (rectangular, circular, etc.) of the original building columns, and the size of the extended anchor plate can be flexibly adjusted according to the load-bearing capacity. It is suitable for different types of columns such as reinforced concrete columns and steel columns, and is applicable to the post-construction steel structure cantilever platform project of various buildings.

[0045] 6. Excellent durability and corrosion resistance, extending the service life of the joint structure: All steel components of this invention are made of Q355B low-alloy high-strength structural steel, which has good tensile and bending resistance. Bolts and clamping anchors are made of high-strength bolts or stainless steel anchors, avoiding corrosion after long-term use. At the same time, after the joint construction is completed, all welded joints and exposed surfaces are professionally treated with anti-corrosion coating. The structural adhesive is epoxy anti-corrosion structural adhesive, which can effectively isolate air and moisture from contact with steel, prevent steel corrosion and concrete carbonization, extend the service life of the joint structure, and reduce the later maintenance cost. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a schematic diagram of the main structure of the cantilevered platform node structure with added steel structure in this invention; Figure 2 This is a detailed schematic diagram of the cantilevered steel structure node structure added to the present invention; Figure 3 This is a schematic diagram showing the connection between the extended anchor plate and the haunch structure of the present invention.

[0048] In the diagram: 1. Existing building columns; 2. Steel plate connectors; 3. Cantilevered steel beams; 31. Connecting end; 32. Cantilever end; 4. Extended anchor plate; 5. Foundation anchor bolt assembly; 51. Chemical anchor bolt; 6. Tension anchor bolt assembly; 61. Tension anchor bolt; 7. Haunch structure; 8. Angle steel sleeve; 9. High-strength bolt; 10. Compression anchor bolt; 11. Anti-slip pad; 12. Structural adhesive. Detailed Implementation

[0049] The technical solution of the present invention will be clearly and completely described below with reference to embodiments thereof. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0050] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the embodiments of this invention, all technical features can be flexibly combined according to actual engineering needs, as long as the combined technical solution can achieve the inventive purpose of this invention.

[0051] Example: Rectangular reinforced concrete column with steel structure cantilever platform joint structure

[0052] like Figure 1-3 As shown, this embodiment uses the construction of a steel-structured cantilevered viewing platform added to the facade of a commercial building as its application background. The original columns of the building are C40 reinforced concrete rectangular columns with a cross-sectional dimension of 600mm × 600mm. The design live load of the cantilever platform is 3.5kN / ㎡, and the cantilever length of the cantilevered steel beam is 2.5m. The following will describe in detail the specific composition of the node structure, the connection relationship between the components, the construction method, and the test verification results in this embodiment.

[0053] I. The composition of the node structure and the connection relationship of each component

[0054] The post-added steel structure cantilever platform node structure in this embodiment uses the original building column 1 as the connection foundation. Its core components include extended anchor plate 4, steel plate connector 2, cantilever steel beam 3, foundation anchor bolt assembly 5, tension anchor bolt assembly 6, haunch structure 7, angle steel sleeve 8, high-strength bolt 9, clamping anchor bolt 10, and structural adhesive 12.

[0055] The extended anchor plate 4 is a rectangular steel plate adapted to the surface of the existing column 1, tightly fitted to the connecting side of the existing column 1. Made of Q355B low-alloy high-strength structural steel, the extended anchor plate 4 is 25mm thick and has a planar dimension of 800mm × 800mm. Its coverage area is 1.78 times the area of ​​the column's connecting side. This design increases the contact area between the extended anchor plate 4 and the column, providing a wider path for subsequent stress transfer. The gap between the extended anchor plate 4 and the column surface is controlled within 1.5mm, creating favorable conditions for subsequent injection of structural adhesive.

[0056] On the side of the extended anchor plate 4 away from the original building column 1, a steel plate connector 2 is vertically welded. The steel plate connector 2 is also made of Q355B low alloy high-strength structural steel, in the shape of a rectangular plate with dimensions of 500mm×300mm and a thickness of 20mm. Its height reaches 0.9 times the height of the web of the cantilever steel beam 3, ensuring full fit with the web of the cantilever steel beam 3.

[0057] The extended anchor plate 4 is fixedly connected to the existing building column 1 via two rows of anchor bolts. The first row is the basic anchor bolt assembly 5, consisting of six M22 chemical anchor bolts 51. These chemical anchor bolts 51 are arranged vertically at equal intervals and inserted vertically into the existing building column 1, achieving an effective anchoring depth of 330mm (i.e., 15 times the bolt diameter). The adhesive used for the chemical anchor bolts 51 is epoxy-based anchoring adhesive, ensuring reliable bonding between the anchor bolts and the concrete. The second row is the tension anchor bolt assembly 6, located above the basic anchor bolt assembly 5, consisting of six M22 tension anchor bolts 61. In this embodiment, the tension anchor bolts 61 are also chemical anchor bolts, with specifications identical to the chemical anchor bolts 51 in the basic anchor bolt assembly 5, and a vertical spacing of 120mm. The bolt ends of both rows of anchor bolts pass through the extended anchor plate 4 and are locked with nuts, forming an upper and lower two-row tension anchor bolt structure. When the node is subjected to bending moment, the resulting tensile force is borne by both the upper and lower rows of anchor bolts, thus changing the unfavorable stress mode in traditional structures where the tensile force is highly concentrated in the upper single row of bolts.

[0058] The cantilevered steel beam 3 is an H-beam made of Q355B low-alloy high-strength structural steel, with a model number of H300×150×10×16, a flange thickness of 16mm, and a web thickness of 10mm. One end of the cantilevered steel beam 3 is the connecting end 31, and the other end is the cantilever end 32, which cantilevers outward by 2.5m. The connecting end 31 of the cantilevered steel beam 3 is connected to the steel plate connector 2 using a dual connection method: the web of the connecting end 31 is fixed to the steel plate connector 2 by eight high-strength bolts 9. These high-strength bolts 9 are 10.9 grade M20 large hexagonal head high-strength bolts, arranged symmetrically in two rows, with a final tightening torque of 400N·m, which meets the relevant specifications; the flange of the connecting end 31 is fixed to the steel plate connector 2 by equal-strength penetration welding, and the weld has been ultrasonically tested to meet the requirements of a Class II weld. This combination of bolted and welded connections facilitates on-site installation and adjustment while ensuring the reliability of the connection parts under stress.

[0059] To further enhance the bending resistance of the connecting end 31 of the cantilever steel beam 3, a haunch structure 7 is provided at the top of the connecting end 31. This haunch structure 7 is composed of a triangular stiffening plate and a trapezoidal stiffening plate, made of Q355B low-alloy high-strength structural steel, with a thickness of 18mm and right-angled side lengths of 300mm and 400mm respectively, with a right-angled side length ratio of 1:1.33. One end of the trapezoidal stiffening plate of the haunch structure 7 is located at the top of the cantilever steel beam 3, and the other end is connected to the extended anchor plate 4. The first side of the triangular stiffening plate of the haunch structure 7 is welded and fixed to the upper flange of the cantilever steel beam 3, the second side of the triangular stiffening plate of the haunch structure 7 is connected to the extended anchor plate 4, and the third side of the triangular stiffening plate of the haunch structure 7 is connected to the hypotenuse of the trapezoidal stiffening plate. All welds are fillet welds with a weld leg size of 10mm and a weld length of not less than 210mm. This triangular stiffening plate and trapezoidal stiffening plate connect the upper flange of the cantilever steel beam 3 and the extended anchor plate 4 into one, forming a complete bending strengthening system. This allows the bending moment at the beam end to be evenly transferred to the extended anchor plate 4 along the stiffening plate, effectively avoiding stress concentration at the beam end.

[0060] An angle steel sleeve 8 is installed around the outer perimeter of the existing column 1. In this embodiment, the existing column 1 is a rectangular column, and the angle steel sleeve 8 is composed of four equilateral angle steels spliced ​​together. The angle steel specifications are L110×10, and the material is Q355B low alloy high-strength structural steel. The four angle steels are set around the outer perimeter of the column, and their inner sidewalls are tightly fitted to the surface of the column. One end of the angle steel sleeve 8 is welded to the edge of the extended anchor plate 4, and adjacent angle steels are welded together by bevel welding to form a closed enclosure structure. This closed enclosure structure expands the connection between the extended anchor plate 4 and the column from a unidirectional fit to a circumferential enclosure, so that the nodal stress can be evenly transferred to the entire cross section of the column through the extended anchor plate 4 and the angle steel sleeve 8, avoiding stress concentration at the anchor bolt anchoring point.

[0061] To further ensure a tight fit between the angle steel sleeve 8 and the column surface, a clamping anchor 10 is installed in the middle of each angle steel member of the sleeve 8. The clamping anchor 10 is an M20 stainless steel mechanical anchor, with its threaded end passing through the angle steel sleeve 8 and directly abutting against the surface of the existing column 1, and then locked in place by a nut. An anti-slip pad 11, made of 5mm thick rubber, is also installed at the threaded end of the clamping anchor 10, fitting between the outer wall of the angle steel sleeve 8 and the nut to provide anti-slip and cushioning effects. By tightening the clamping anchor 10, the angle steel sleeve 8 and the column surface are mechanically pressed together, eliminating the initial gap between them.

[0062] Structural adhesive 12 is injected into the gaps between the extended anchor plate 4 and the original building column 1, as well as the gaps between the angle steel sleeve 8 and the original building column 1. In this embodiment, epoxy-based structural adhesive is used, with a bonding strength of 35 MPa and a compressive strength of 90 MPa. The structural adhesive 12 is injected using a low-pressure grouting method at a pressure of 0.2 MPa, ensuring that the adhesive in the gaps is full and free of air bubbles. The curing time is 72 hours, and the ambient temperature is controlled at 20°C during the curing process. The adhesive layer formed after the structural adhesive 12 has cured can bear some tensile and shear stresses, forming a dual-stress system together with the mechanical anchoring of the anchor bolts. Even if the anchor bolts loosen slightly, the adhesive layer and the angle steel sleeve 8 can still ensure the reliability of the connection at the joint.

[0063] All exposed steel surfaces of the node structure have been treated with anti-corrosion measures: first, two coats of epoxy zinc-rich primer with a dry film thickness of 80μm are applied, followed by two coats of fluorocarbon topcoat with a dry film thickness of 70μm, for a total anti-corrosion layer thickness of 150μm. This effectively isolates the steel from air and moisture, ensuring the long-term durability of the node structure.

[0064] II. Construction Methods for Node Structures

[0065] The post-added steel structure cantilever platform node structure in this embodiment is constructed according to the following steps:

[0066] First, the base layer is prepared. The construction workers clean the connecting sides and outer surfaces of the original column 1 of the building, removing impurities such as laitance, oil stains, and rust. They then use an angle grinder to roughen the surface of the column so that the surface roughness meets the bonding requirements of the structural adhesive 12.

[0067] Subsequently, drilling and anchoring were carried out. According to the design drawings, the drilling positions of the foundation anchor bolt assembly 5 and the tension anchor bolt assembly 6 were accurately marked on the existing column 1 of the building. The holes were drilled using a water drill. After drilling, the dust inside the holes was cleaned, and the chemical anchor bolts 51 of the foundation anchor bolt assembly 5 and the tension anchor bolts 61 of the tension anchor bolt assembly 6 were inserted respectively to ensure the verticality of the anchor bolts. After the adhesive of the chemical anchor bolts 51 cured, the foundation anchoring of the anchor bolts was completed.

[0068] Next, install the extended anchor plate and the steel plate connector. Insert the integrated welded joint of the extended anchor plate 4 and the steel plate connector 2 into the threaded end of each anchor bolt. Adjust the position of the extended anchor plate 4 to ensure it fits tightly against the column surface. Then, use nuts to initially tighten all anchor bolts, controlling the gap between the extended anchor plate 4 and the column surface to be no more than 2mm.

[0069] Then, the cantilever steel beams are hoisted and connected. The prefabricated cantilever steel beam 3 is hoisted to the designated position, so that the web of the connecting end 31 of the cantilever steel beam 3 is fitted with the steel plate connector 2, and high-strength bolts 9 are inserted and initially tightened. After the initial tightening is completed, the flange of the connecting end 31 of the cantilever steel beam 3 is welded to the steel plate connector 2 with equal strength penetration welding. After the welding is completed, the weld is subjected to non-destructive testing. After the test is qualified, the high-strength bolts 9 are finally tightened, and the final tightening torque value meets the design requirements.

[0070] After the cantilever steel beams are connected, the haunch structure is welded. Prefabricated triangular stiffening plates and trapezoidal stiffening plates are installed on the top of the connection end 31 of the cantilever steel beam 3. These triangular stiffening plates and trapezoidal stiffening plates connect the upper flange of the cantilever steel beam 3 and the extended anchor plate 4 into one piece, ensuring that the weld is full, free of slag inclusions and cracks.

[0071] Next, the angle steel sleeves are fabricated and installed. Based on the rectangular cross-sectional dimensions of the existing column 1, four angle steels are prefabricated. The angle steel sleeves 8 are then placed around the outer perimeter of the column, and their positions are adjusted so that one end is welded to the edge of the extended anchor plate 4. Adjacent angle steels are welded together using bevel welding to form a closed enclosure structure. Subsequently, clamping anchor bolts 10 are installed in the middle of each angle steel in the angle steel sleeves 8. The nuts of the clamping anchor bolts 10 are tightened, so that the threaded end of the clamping anchor bolt 10 presses against the surface of the existing column 1, and the angle steel sleeves 8 are pressed tightly against the column surface.

[0072] Then, structural adhesive is injected. Using low-pressure grouting equipment, the prepared epoxy structural adhesive 12 is injected into the gap between the extended anchor plate 4 and the column, as well as the gap between the angle steel sleeve 8 and the column. During the injection process, the structural adhesive 12 is kept full until it overflows evenly from both ends of the gap. After the injection is completed, the injection port is sealed.

[0073] After the structural adhesive 12 has cured to the design strength (curing time 72 hours), all nuts are retightened a second time, including the chemical anchor bolts 51 of the foundation anchor bolt assembly 5, the tension anchor bolts 61 of the tension anchor bolt assembly 6, the nuts of the compression anchor bolts 10 and the high-strength bolts 9, to ensure that the tightening force of all fasteners meets the design requirements.

[0074] Finally, anti-corrosion treatment is carried out. All welded joints, bolted connections, and exposed steel surfaces of the node structure are coated with anti-corrosion paint. First, two coats of epoxy zinc-rich primer are applied, followed by two coats of fluorocarbon topcoat, ensuring that the total thickness of the anti-corrosion layer is not less than 150μm, thus completing the construction of the entire node structure.

[0075] III. Experimental Verification of Node Structure

[0076] After the construction of the node structure in this embodiment was completed, a static load test was conducted in accordance with the requirements of the "Standard for Acceptance of Construction Quality of Steel Structures" GB 50205 and related specifications to verify its stress performance.

[0077] The load-bearing capacity test results show that the ultimate tensile bearing capacity of the node reaches 2.3 times the design value and the ultimate bending bearing capacity reaches 2.1 times the design value, which is far higher than the 1.5 times safety factor required by the code. This indicates that the node structure has sufficient safety reserves and can effectively resist the risk of failure under overload conditions.

[0078] The stress distribution test results show that under the design load, the tensile stress distribution of the upper and lower rows of anchor bolts is uniform, with the maximum tensile stress being only 120 MPa, approximately 60% of the design value of the bolt tensile strength. This result verifies that the upper and lower rows of tension anchor bolts structure does indeed achieve uniform distribution of tensile stress, avoiding the drawback of high tensile force concentration in the upper single row of bolts in traditional structures, and significantly reducing the probability of anchor bolt pull-out failure.

[0079] The test results show that the maximum deflection at the end of the cantilever steel beam 3 is only 3mm, which meets the specification requirements. The haunch structure 7 effectively improves the bending stiffness at the end of the steel beam and avoids excessive deformation at the end of the beam.

[0080] The bonding performance test results show that the bonding between the structural adhesive 12 and the original building column 1 and the extended anchor plate 4 did not fall off, and the angle steel sleeve 8 was not loosened in the fit with the column. This verifies that the dual force system formed by the structural adhesive bonding and the mechanical anchoring of the anchor bolts has good synergistic working ability. Even if the anchor bolts are slightly loose, the bonding layer and the angle steel sleeve 8 can still ensure the reliability of the connection of the node.

[0081] Based on the above test results, the node structure of this embodiment exhibits excellent overall stability, and all test indicators meet the design and specification requirements, fully verifying the effectiveness and reliability of the technical solution of this invention.

[0082] IV. Summary

[0083] This embodiment achieves uniform distribution of tensile stress at the joint by setting up upper and lower rows of tension anchor bolts, fundamentally solving the technical problem of tensile force concentration at the upper bolts in traditional joints. The addition of a haunch structure strengthens the bending resistance of the cantilevered steel beam ends, avoiding localized stress concentration and weld cracking. The use of angle steel sleeves and clamping anchor bolts forms a closed enclosure structure and achieves mechanical clamping. By injecting structural adhesive into the gaps between the extended anchor plate and the column, and between the angle steel sleeve and the column, dual safety guarantees of adhesive bonding and anchor bolt anchoring are achieved. The connection relationships between the components are clear and explicit, the construction method is complete and feasible, and the test results fully demonstrate the technical effectiveness of this invention, providing a safe and reliable joint structure solution for post-construction steel structure cantilever platform projects.

[0084] The parameters of each component of the post-added steel structure cantilever platform node structure of the present invention can be flexibly adjusted according to the load requirements of the actual project, the cantilever length, the cross-sectional dimensions and materials of the original columns of the building. The core design concept is "dispersing tensile stress, strengthening bending resistance, double fixing protection, and integrated stress transfer". Any structural improvements based on this design concept are within the protection scope of the present invention.

[0085] In the actual construction process, it is necessary to strictly follow the current national standards and specifications, and to carry out quality control on key processes such as anchor bolt anchoring, welding construction, high-strength bolt connection, and structural adhesive grouting to ensure that the construction quality of the node structure meets the design and specification requirements.

[0086] The node structure of this invention is not only applicable to the addition of cantilevered platforms on building facades, but can also be extended to various post-construction steel structure cantilever projects such as steel structure cantilevered corridors, cantilevered staircases, cantilevered billboards, and cantilevered viewing platforms, and has wide industrial applicability.

[0087] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A post-added steel cantilever platform node structure, using the original building columns (1) as the connection foundation, characterized in that, It includes an extended anchor plate (4), a steel plate connector (2), a cantilever steel beam (3), a foundation anchor bolt assembly (5), and a tension anchor bolt assembly (6); The extended anchor plate (4) is attached and fixed to the connecting side of the original column (1) of the building; The steel plate connector (2) is vertically positioned on the side of the extended anchor plate (4) away from the original building column (1); The connecting end (31) of the cantilever steel beam (3) is fixedly connected to the steel plate connector (2); The basic anchor bolt assembly (5) includes multiple anchor bolts, which are arranged vertically and anchored in the original column (1) of the building. The screw end of the anchor bolt passes through the extended anchor plate (4) and is locked by a nut. The tension anchor assembly (6) includes a plurality of tension anchors (61), which are arranged vertically and anchored within the original building column (1) and located above the foundation anchor assembly (5). The screw end of the tension anchor (61) passes through the extended anchor plate (4) and is locked with a nut.

2. The post-added steel structure cantilever platform node structure according to claim 1, characterized in that, It also includes a haunch structure (7), which is composed of a triangular stiffening plate and a trapezoidal stiffening plate. One end of the trapezoidal stiffening plate of the haunch structure (7) is set at the top of the cantilever steel beam (3), and the other end of the trapezoidal stiffening plate of the haunch structure (7) is connected to the extended anchor plate (4). The first side of the triangular stiffening plate of the haunch structure (7) is welded and fixed to the upper flange of the cantilever steel beam (3). The second side of the triangular stiffening plate of the haunch structure (7) is connected to the extended anchor plate (4), and the third side of the triangular stiffening plate of the haunch structure (7) is connected to the hypotenuse of the trapezoidal stiffening plate.

3. The post-added steel structure cantilever platform node structure according to claim 1, characterized in that, It also includes an angle steel enclosure (8), which is set around the outer perimeter of the original column (1) of the building, and one end of the angle steel enclosure (8) is welded and fixed to the edge of the extended anchor plate (4) to form a closed enclosure structure.

4. The post-added steel structure cantilever platform node structure according to claim 3, characterized in that, An anchor bolt (10) is provided on the angle steel sleeve (8). The screw end of the anchor bolt (10) passes through the angle steel sleeve (8) and abuts against the surface of the original column (1) of the building, and is locked by a nut.

5. The post-added steel structure cantilever platform node structure according to claim 3, characterized in that, The gap between the extended anchor plate (4) and the original building column (1), as well as the gap between the angle steel sleeve (8) and the original building column (1), are filled with structural adhesive (12).

6. The post-added steel structure cantilever platform node structure according to claim 1, characterized in that, The web of the connecting end (31) of the cantilever steel beam (3) is fixedly connected to the steel plate connector (2) by multiple high-strength bolts (9), and the flange of the connecting end (31) of the cantilever steel beam (3) is fixedly welded to the steel plate connector (2) by equal-strength penetration welding.

7. The post-added steel structure cantilever platform node structure according to claim 1, characterized in that, The anchor bolts of the basic anchor bolt assembly (5) are chemical bolts (51), with a quantity of 4 to 6, and an effective anchoring depth of not less than 15d, where d is the diameter of the thread of the chemical bolt (51); the number of tension anchor bolts (61) in the tension anchor bolt assembly (6) is the same as the number of chemical bolts (51), and the specifications are the same as those of the chemical bolts (51), and the vertical distance between the tension anchor bolts (61) and the basic anchor bolt assembly (5) is 100 to 150 mm.

8. The post-added steel structure cantilever platform node structure according to claim 2, characterized in that, The thickness of the triangular stiffening plate and trapezoidal stiffening plate of the haunch structure (7) is 16~20mm. The welding of the haunch structure (7) with the extended anchor plate (4) and the cantilever steel beam (3) is done by fillet weld with a weld leg size of 8~12mm.

9. The post-added steel structure cantilever platform node structure according to claim 3, characterized in that, The angle steel enclosure (8) is made of equilateral angle steel. When the original column (1) of the building is a rectangular column, the angle steel enclosure (8) is made of four angle steels spliced ​​together, and the adjacent angle steels are fixed by bevel welding. When the original column (1) of the building is a circular column, the angle steel enclosure (8) is made of curved angle steels spliced ​​together.

10. A construction method for a post-added steel structure cantilever platform node structure as described in any one of claims 1 to 9, characterized in that, Includes the following steps: a. Base treatment: Clean the connecting sides and outer surfaces of the original columns (1) of the building, remove impurities and roughen the surface; b. Drilling and anchoring: Mark the drilling positions on the existing column (1) of the building, clean the dust in the hole after drilling, and plant the anchors of the foundation anchor assembly (5) and the tension anchors (61) respectively. The anchoring is completed after the adhesive has cured. c. Install the extended anchor plate and steel plate connector: fit the integrated welded part of the extended anchor plate (4) and the steel plate connector (2) into the anchor bolt of the foundation anchor bolt assembly (5) and the screw end of the tension anchor bolt (61), adjust the position and then initially tighten the nut; d. Hoisting and connecting the cantilever steel beam: Hoist the cantilever steel beam (3) so that the web of the connecting end (31) of the cantilever steel beam (3) fits against the steel plate connector (2), insert high-strength bolts (9) for initial tightening, weld the flange of the connecting end (31) of the cantilever steel beam (3) to the steel plate connector (2) to form an equal-strength penetration weld, and after the weld is qualified, finally tighten the high-strength bolts (9); e. Welding of the haunch structure: Install the haunch structure (7), and weld and fix the triangular stiffening plate and trapezoidal stiffening plate of the haunch structure (7) to the cantilever steel beam (3), the extended anchor plate (4), and the triangular stiffening plate and trapezoidal stiffening plate respectively; f. Angle steel enclosure fabrication and installation: Prefabricate and install the angle steel enclosure (8), weld the angle steel enclosure (8) to the extended anchor plate (4) to form a closed enclosure structure, install and tighten the clamping anchor bolt (10) so that the screw end of the clamping anchor bolt (10) abuts against the surface of the original column (1) of the building. g. Structural adhesive injection: Using low-pressure grouting equipment, structural adhesive (12) is injected into the gap between the extended anchor plate (4) and the original building column (1), and the gap between the angle steel sleeve (8) and the original building column (1), to ensure that the structural adhesive (12) is full; h. Curing and tightening: After the structural adhesive (12) has cured to the design strength, all nuts of the anchor bolts of the basic anchor bolt assembly (5), the tension anchor bolt (61), the compression anchor bolt (10) and the high-strength bolt (9) are tightened a second time. i. Corrosion protection: Apply anti-corrosion coating to the welded joints, bolted connections, and exposed steel surfaces of the node structure.

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