Anti-fatigue cast steel bifurcated node externally attached with CFRP (carbon fiber reinforced plastic) strip

Abstract

The utility model discloses an anti-fatigue cast steel bifurcated node externally attached with CFRP (carbon fiber reinforced plastic) strips, which relates to the technical field of tree-shaped column steel structures and aims to solve the technical problem of poor stress performance of tree-shaped column nodes. The anti-fatigue cast steel bifurcated node comprises a main pipe and branch pipes, the main pipe and the branch pipes are circular, and the number of the branch pipes and the number of the bifurcated nodes are multiple. The externally-pasted CFRP strips are made of carbon fiber reinforced composites, the CFRP strips are pasted in the longitudinal direction of the junction of the node main pipe and the node branch pipes according to the types of the nodes, the number of the layers of the CFRP strips is one, then the number of circles wound and pasted on the surfaces of the pasted longitudinal CFRP strips in the annular direction of the junction of the node main pipe and the node branch pipes is one, and the number of circles wound and pasted on the surfaces of the pasted longitudinal CFRP strips in the annular direction is one. According to the cast steel bifurcated joint, the CFRP strips can be fully utilized to reduce the stress amplitude of the cast steel bifurcated joint, the fatigue strength of the joint is improved, the fatigue damage of the joint is relieved, and the cast steel bifurcated joint has the advantages of being reasonable in structural design, convenient and rapid to construct and good in using effect.

Description

Technical Field

[0001] The utility model relates to the technical field of tree-shaped column steel structures, and more specifically, to an anti-fatigue cast steel bifurcated joint with externally bonded CFRP strips. Background Technique

[0002] The tree-shaped column structure, with its beautiful appearance and good mechanical properties, conforms to the development trend of large-span spatial structures today, which pursue larger spans and more beautiful shapes. Therefore, it is increasingly favored by people. The cast steel bifurcated joint is prone to stress concentration in the main and branch pipe intersection core area, which is the weak link of the entire tree-shaped column. The mechanical properties of the joint are poor, and it is prone to fatigue failure under the action of repeated alternating loads such as earthquakes and winds, even when the stress is lower than the ultimate tensile strength or even the yield point. This kind of failure is often brittle failure. Almost no plastic deformation process of the component can be observed during failure, and it occurs suddenly without any signs, and its consequences are also catastrophic. Therefore, this kind of fatigue failure should be avoided in engineering design. In view of this, we propose an anti-fatigue cast steel bifurcated joint with externally bonded CFRP strips. Content of the Utility Model

[0003] The purpose of the utility model is to overcome the deficiencies of the prior art, meet the actual needs, and provide an anti-fatigue cast steel bifurcated joint with externally bonded CFRP strips to solve the technical problem of poor mechanical properties of the current tree-shaped column joints.

[0004] To solve the above technical problems, the utility model provides the following technical solutions: an anti-fatigue cast steel bifurcated joint with externally bonded CFRP strips, including a tree-shaped column steel structure, the tree-shaped column steel structure is composed of a main pipe and multiple branch pipes, there are several joints on the tree-shaped column steel structure, the joint is formed by smooth transition after the confluence of a main pipe and multiple branch pipes with different pipe diameters, circumferential CFRP strips and longitudinal CFRP strips are pasted along the longitudinal and circumferential directions at the confluence of the main pipe and the branch pipes, the longitudinal CFRP strips are bonded and fixed to the outer walls of the main pipe and the branch pipes through an adhesive, the circumferential CFRP strips are on the surface of the longitudinal CFRP strips, and the circumferential CFRP strips are also pasted and fixed to the longitudinal CFRP strips and the pipe wall through an adhesive, and the adhesives are all epoxy adhesives.

[0005] Preferably, the main pipe and the branch pipes are circular rings, and the joints are divided into bifurcated joints, trifurcated joints, and quadrifurcated joints according to the number of branch pipes.

[0006] Preferably, the circumferential CFRP strips and the longitudinal CFRP strips are carbon fiber reinforced composites. When pasting the CFRP strips, first along the longitudinal direction at the confluence of the main pipe and the branch pipes of the joint, the corresponding number of longitudinal CFRP strips are pasted according to the type of the joint, and the number of layers of the longitudinal CFRP strips is one layer.

[0007] Preferably, the circumferential CFRP strip is located at the circumferential position of the intersection of the main and branch pipes of the node. The circumferential CFRP strip is on the surface of the longitudinally pasted CFRP strip. The circumferential CFRP strip is pasted at fixed equal intervals and wound around in a circle along the circumferential direction. The circumferential CFRP strip and the longitudinal CFRP strip are tightly wound together.

[0008] Preferably, a restraint sleeve is provided between the main pipe and the multiple branch pipes. The restraint sleeve is provided with a plurality of cavities adapted to the branch pipes. The restraint sleeve is divided into four equal parts and connected by bolts.

[0009] Preferably, longitudinal grooves and transverse grooves are provided on the outer periphery of the bottom end of the restraint sleeve. The longitudinal grooves and transverse grooves are respectively used for pasting longitudinal CFRP strips and circumferential CFRP strips.

[0010] Preferably, a groove is provided in the intersection area of the longitudinal CFRP strip and the circumferential CFRP strip. A clamping sleeve is provided on the inner circumference of the groove. A glue injection port is provided at the top of the clamping sleeve.

[0011] The externally pasted CFRP strip anti-fatigue cast steel bifurcated node of the present invention has a bifurcated node (attached Figure 1 ), a trifurcated node (attached Figure 2 ), and a quadrifurcated node (attached Figure 3 ). The node is formed by a smooth transition after the confluence of a main pipe and multiple branch pipes with different pipe diameters. Both the main pipe and the branch pipes are circular rings. The externally pasted CFRP strip is a carbon fiber reinforced composite material. When pasting the CFRP strip, first, different numbers of CFRP strips are pasted longitudinally along the main and branch pipes of the node according to the type of the node, and then along the circumferential direction of the intersection of the main and branch pipes of the node, on the surface of the longitudinally pasted CFRP strip, CFRP strips are pasted at fixed equal intervals and wound around in a circle along the circumferential direction. When winding and pasting along the circumferential direction, the CFRP strips should be made dense and compact. Epoxy adhesives are used to bond and fix the outer walls of the main pipe, branch pipes and the longitudinal CFRP strips, as well as between the longitudinal and circumferential CFRP strips.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] In the present invention, the CFRP strip is longitudinally pasted on the outer wall of the intersection of the main and branch pipes of the node by using an adhesive. On the tension side of the cast steel bifurcated node, the CFRP strip can share a part of the tension, thereby reducing the tensile stress amplitude on this side of the node, and can reduce the stress amplitude of the node under alternating loads. The circumferentially wound CFRP strip can not only fix the longitudinal CFRP strip densely, but also slow down the bending moment at the root of the branch pipe, improve the stress performance of the node, and improve the anti-fatigue strength of the node, so that the service life of the node is longer.

[0014] In the epoxy adhesive of the present utility model, its bonding performance is particularly strong, with high strength and elastic modulus, high chemical stability, basically no shrinkage and no residual stress during curing, and can maintain stability and durability under various sizes. The externally pasted CFRP strip has high tensile strength and excellent fatigue resistance. Using the epoxy adhesive to paste the CFRP strip on the outer wall of the node makes the steel, adhesive, and CFRP form a common whole, and the toughness and durability have been greatly improved compared with the previous cast steel bifurcated node. When resisting alternating loads, it can overcome the defects of steel, thereby improving the fatigue performance of the node.

[0015] The CFRP strip in the present utility model is easy to cut and form. Especially for the bifurcated node with a complex structural form, it only needs to be pasted at the most unfavorable position of the node. At the same time, the number of CFRP strips pasted can be appropriately increased or decreased according to different types of nodes, avoiding problems such as bulging and complex construction caused by too large a laying area when pasting the whole CFRP cloth. The construction is convenient, easy to master, and has high construction efficiency.

[0016] The design of the four-equal-part of the restraint sleeve in the present utility model, combined with the fixation of bolts, is convenient for transportation and on-site installation. The cavity opening of the restraint sleeve surrounds the node, which can further increase the stress performance of the node and improve safety. Then, combined with the connection of the CFRP strip to the restraint sleeve, the restraint sleeve and the CFRP strip form a whole, with higher stability and stronger resistance of the restraint sleeve, playing a greater protective role for the node. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of the bifurcated cast steel node of the present utility model;

[0018] Figure 2 is a schematic structural diagram of the trifurcated cast steel node of the present utility model;

[0019] Figure 3 is a schematic structural diagram of the quadrifurcated cast steel node of the present utility model;

[0020] Figure 4 is a schematic cross-sectional view of the main pipe of the quadrifurcated cast steel node of the present utility model;

[0021] Figure 5 is a schematic structural diagram of the restraint sleeve in the fixed state of the present utility model;

[0022] Figure 6 is a schematic structural diagram of the restraint sleeve when the CFRP strip is removed of the present utility model;

[0023] Figure 7 is a schematic structural diagram of the ferrule of the present utility model.

[0024] Description of reference numerals in the figure: 1. Main pipe; 2. Branch pipe; 3. Longitudinal CFRP strip; 4. Circumferential CFRP strip; 5. Constraint sleeve;

[0025] 501. Longitudinal groove; 502. Transverse groove; 503. Groove; 504. Clamping sleeve; 505. Glue injection port. Detailed implementation mode

[0026] As Figures 1 to 7 shown, a fatigue-resistant cast steel bifurcated joint with externally bonded CFRP strips according to the present utility model includes a tree-shaped column steel structure with a plurality of joints thereon. The tree-shaped column steel structure is composed of a main pipe 1 and a plurality of branch pipes 2. The main pipe 1 and the branch pipes 2 are circular rings. The joints are divided into bifurcated joints, trifurcated joints and quadrifurcated joints according to the number of branch pipes 2. The joint is formed by the smooth transition after the confluence of a main pipe 1 and a plurality of branch pipes 2 with different pipe diameters. The circumferential CFRP strip 4 and the longitudinal CFRP strip 3 are pasted along the longitudinal and circumferential directions at the confluence of the main pipe 1 and the branch pipes 2. The circumferential CFRP strip 4 and the longitudinal CFRP strip 3 are carbon fiber reinforced composites. The longitudinal CFRP strip 3 is bonded and fixed to the outer walls of the main pipe 1 and the branch pipes 2 through an adhesive. The circumferential CFRP strip 4 is on the surface of the longitudinal CFRP strip 3. The circumferential CFRP strip 4 is also pasted and fixed to the longitudinal CFRP strip 3 and the pipe wall through an adhesive. The adhesives are all epoxy adhesives. The pasting of the CFRP strips first follows the longitudinal direction at the confluence of the main pipe 1 and the branch pipes 2 of the joint, and the corresponding number of longitudinal CFRP strips 3 are pasted according to the type of the joint. The number of layers of the longitudinal CFRP strips 3 is one layer. The circumferential CFRP strip 4 is at the circumferential position of the confluence of the main and branch pipes 2 of the joint. The circumferential CFRP strip 4 is on the surface of the longitudinally pasted CFRP strips 3. The circumferential CFRP strip 4 is pasted at fixed equal intervals and wound and pasted in a circle along the circumferential direction. The circumferential CFRP strip 4 and the longitudinal CFRP strip 3 are tightly wound.

[0027] In a further embodiment, in order to further improve the mechanical properties of the joint, a constraint sleeve 5 is provided between the main pipe 1 and the plurality of branch pipes 2. The constraint sleeve 5 is provided with a plurality of cavity openings adapted to the branch pipes 2. The constraint sleeve 5 is divided into four equal parts and connected by bolts. The outer periphery of the bottom end of the constraint sleeve 5 is provided with a longitudinal groove 501 and a transverse groove 502. The longitudinal groove 501 and the transverse groove 502 are respectively used for pasting the longitudinal CFRP strip 3 and the circumferential CFRP strip 4. A groove 503 is provided in the intersection area of the longitudinal CFRP strip 3 and the circumferential CFRP strip 4. A clamping sleeve 504 is provided on the inner periphery of the groove 503. The clamping sleeve 504 has an interference fit with the groove 503. A glue injection port 505 is provided at the top of the clamping sleeve 504. After the clamping sleeve 504 has an interference fit with the groove 503, glue can be input through the glue injection port 505 to further enhance the connection stability of the intersection of the longitudinal CFRP strip 3 and the circumferential CFRP strip 4.

[0028] Working principle: This embodiment provides a fatigue-resistant cast steel bifurcated joint with externally bonded CFRP strips. First, the main pipe 1 has a cross-section of 500*40 mm and a length of 800 mm, the branch pipe 2 has a cross-section of 350*30 mm and a length of 500 mm. The chamfer radius between the main pipe 1 and the branch pipe 2 is 1000 mm, the outer chamfer radius between the branch pipes 2 is 100 mm, and the inner chamfer radius is 20 mm. The CFRP strip has a width of 60 mm and a thickness of 1.4 mm.

[0029] During use, during engineering construction, the cast steel bifurcated joint needs to be integrally cast in the steel structure factory and then transported to the site for installation. On the installed joint, along the weak areas where the main pipe 1 and the branch pipe 2 converge, first use gauze to polish the pipe wall smoothly and clean the surface of the CFRP strip. Then, evenly apply adhesive on the polished outer wall, and immediately stick on the longitudinal CFRP strip 3 with a single layer. Try to keep the longitudinal CFRP strip 3 straight to avoid wrinkles. Apply adhesive on the outer surface of the pasted longitudinal CFRP strip 3 and the pipe wall along the circumferential direction, and also quickly stick on the circumferential CFRP strip 4 with one turn of circumferential winding. At the same time, keep the circumferential CFRP strip 4 dense and compact to fix the longitudinal CFRP strip 3. The circumferential spacing of the circumferential CFRP strip 4 along the longitudinal direction is 200 mm.

[0030] After the adhesive dries, the construction is completed.

[0031] Furthermore, the upper longitudinal CFRP strip 3 and circumferential CFRP strip 4 can be bonded with the longitudinal groove 501 and transverse groove 502 using glue, and then the ferrule 504 is in an interference fit with the groove 503, and glue is input through the injection port 505 to further enhance the connection stability at the intersection of the longitudinal CFRP strip 3 and the circumferential CFRP strip 4, realizing the tight fitting of the restraint sleeve 5 and further strengthening the mechanical properties of the joint.

[0032] The embodiments disclosed in this utility model are preferred embodiments, but not limited thereto. Those of ordinary skill in the art can easily understand the spirit of this utility model based on the above embodiments and make different extensions and changes. However, as long as they do not depart from the spirit of this utility model, they are within the protection scope of this utility model.

Claims

1. A fatigue-resistant cast steel bifurcation node with CFRP strips attached externally, characterized in that: The invention comprises a tree-like column steel structure, wherein the tree-like column steel structure is composed of a main pipe (1) and a plurality of branch pipes (2). The tree-like column steel structure is provided with a plurality of nodes, wherein the nodes are formed by a smooth transition after a main pipe (1) and a plurality of branch pipes (2) of different pipe diameters meet. The meeting point of the main pipe (1) and the branch pipes (2) is provided with annular CFRP strips (4) and longitudinal CFRP strips (3) in the longitudinal and annular directions. The longitudinal CFRP strips (3) are bonded and fixed to the outer walls of the main pipe (1) and the branch pipes (2) by adhesive. The annular CFRP strips (4) are on the surface of the longitudinal CFRP strips (3). The annular CFRP strips (4) are also bonded and fixed to the longitudinal CFRP strips (3) and the pipe wall by adhesive. The adhesives are all epoxy adhesives.

2. The fatigue-resistant cast steel bifurcation node with externally bonded CFRP strips according to claim 1, characterized in that: The main pipe (1) and the branch pipe (2) are in the shape of a ring, and the node is divided into a two-fork node, a three-fork node and a four-fork node according to the number of branch pipes (2).

3. The fatigue-resistant cast steel bifurcation node with externally bonded CFRP strips according to claim 2, characterized in that: The circumferential CFRP strips (4) and the longitudinal CFRP strips (3) are carbon fiber reinforced composite materials. The CFRP strips are first pasted along the longitudinal direction of the intersection of the node main pipe (1) and the branch pipe (2), and a corresponding number of longitudinal CFRP strips (3) are pasted according to the type of the node. The number of layers of the longitudinal CFRP strips (3) is one layer.

4. The fatigue-resistant cast steel bifurcation node with externally bonded CFRP strips according to claim 3, characterized in that: The annular CFRP strip (4) is located at an annular position at the intersection of the node main branch pipe (2), and the annular CFRP strip (4) is on the surface of the longitudinal CFRP strip (3) that has been pasted. The annular CFRP strip (4) is pasted at a fixed equal interval and pasted in a circle along the annular direction. The annular CFRP strip (4) and the longitudinal CFRP strip (3) are tightly and compactly wound.

5. The fatigue-resistant cast steel bifurcation node with externally bonded CFRP strips according to claim 4, characterized in that: A restraining sleeve (5) is arranged between the main pipe (1) and the plurality of branch pipes (2), the restraining sleeve (5) being provided with a plurality of cavities adapted to the branch pipes (2), the restraining sleeve (5) being divided into four equal parts and connected by bolts.

6. The fatigue-resistant cast steel bifurcation node with externally bonded CFRP strips according to claim 5, characterized in that: The outer periphery of the bottom end of the restraining sleeve (5) is provided with a longitudinal groove (501) and a transverse groove (502), and the longitudinal groove (501) and the transverse groove (502) are used for pasting the longitudinal CFRP strip (3) and the annular CFRP strip (4) respectively.

7. The fatigue-resistant cast steel bifurcation node with externally bonded CFRP strips according to claim 6, characterized in that: A groove (503) is provided at the intersection area of ​​the longitudinal CFRP strip (3) and the annular CFRP strip (4), a sleeve (504) is provided on the inner periphery of the groove (503), and a glue injection port (505) is provided on the top of the sleeve (504).

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