External prestressing reinforcing method for existing grid structure

Abstract

The invention discloses an external prestressing reinforcing system of an existing net rack structure. Bolt-sphere connection nodes are adopted between adjacent steel pipes in an existing net rack; the lower ends of the partial bolt-sphere joints are connected with vertical supporting rods; the bolt-sphere joint is connected with the vertical supporting rod by forming a through hole in the bottom of the side wall. The lower ends of part of the vertical supporting rods are connected with endless cables, and the distribution positions of the endless cables are determined according to the span of the grid structure. In the connection mode of the ring cable and the vertical supporting rod lower chord, the supporting rod lower chord is connected with the ball cable clamp in a welded mode, and the ring cable body penetrates through a middle hole of the ball cable clamp to be fixedly connected. Displacement of the grid structure is controlled through the endless cable, the overall stability of the grid structure is improved, and local stress concentration is reduced; the existing grid structure is reinforced through the inhaul cables by utilizing the vertical supporting rods, the prestressed steel inhaul cables and the ring cables, tension stress formed by tensioning the prestressed steel cables can be converted into prestress, upward bearing force is generated on the vertical supporting rods, deformation of the grid structure is reduced, and the structural strength and stability are improved.

Description

Technical Field

[0001] The invention relates to the technical field of grid structures, and in particular to an external prestressed reinforcement method for an existing grid structure. Background Art

[0002] The space grid structure is a three-dimensional truss structure, which is composed of multiple rods connected in a certain geometric form and mainly bears the overall bending internal force. Due to the advantages of light weight, high rigidity and beautiful appearance, the space grid structure has been widely used in modern construction projects, especially in large public buildings such as stadiums, exhibition halls, and airport terminals. However, with the increase of service life, the grid structure will be eroded and affected by various environmental factors, causing the load or deflection of the structure to increase. When the strength, rigidity and stability of the structure cannot meet the original design requirements, there is a great safety hazard, and it is necessary to reinforce or repair the original grid structure.

[0003] At present, there are many reinforcement methods for space grid structures in the field of construction, which can extend their service life and improve their safety performance. These methods are divided into two categories: direct reinforcement method and indirect reinforcement method. The direct reinforcement method mainly enhances the bearing capacity and stiffness of the structure by adding or replacing structural components, such as adding rods to the original structure or replacing damaged rods. However, the direct reinforcement method often increases the deadweight of the structure, changes the stress state of the structure, increases the construction period and material costs, and may affect the appearance and use function of the building. In contrast, the indirect reinforcement method improves its performance by changing the stress mode of the grid structure, among which the prestressed reinforcement method is the most common and effective one. In this method, during the reinforcement process, the prestressed components that are pre-tensioned are stressed in advance. After the load is applied, the prestressed components can be stressed in coordination with the original components, reducing stress differences and material deformation, thereby improving their bearing capacity and stiffness, and reducing deformation and cracks. Among the prestressed reinforcement methods, the external prestressed reinforcement technology has been widely used due to its advantages such as simple construction, little impact on the original structure, and significant effect.

[0004] External prestressing corresponds to the internal prestressing of the traditional prestressed tendons arranged in the structure. It refers to the prestressed structural system formed by applying prestress to the steel cables arranged outside the main body of the load-bearing structure. At present, the external prestressing reinforcement method for grid structures usually arranges strip cables in a single direction or two vertical directions at the bottom of the grid, and adopts the external prestressed cable support anti-arch technology for the structure that needs to be reinforced, using prestress to digest the internal load of the structure and reduce the peak stress and strain of the structure. Although this form of reinforcement has improved the structural performance to a certain extent, it also has some shortcomings. First, this method requires the use of a large number of cables and struts, resulting in large material consumption and poor economy. Secondly, due to the relatively simple arrangement of cables and struts, the role of prestress cannot be fully exerted, and the effect of improving structural performance is limited. In addition, traditional reinforcement methods may cause certain disturbances to the existing structure during construction, increasing the difficulty and risk of construction.

[0005] In summary, in order to better improve the overall performance of the grid structure, the present invention proposes an external prestressed reinforcement method for an existing grid structure. By arranging a ring-shaped cable bearing system on the lower chord of the grid structure, the structural performance can be more effectively improved. This method significantly improves the stability and bearing capacity of the structure while reducing the amount of material used, and has good economy and applicability. By reasonably arranging the ring-shaped cable bearing system and the prestressing method, the displacement of the structure can be effectively reduced, the maximum stress can be reduced, and the local stress concentration phenomenon can be reduced, thereby extending the service life of the structure and ensuring its safety and reliability. Summary of the invention

[0006] The present invention proposes an external prestressed reinforcement method for an existing grid structure, which can more effectively improve the structural performance by arranging a ring-shaped cable bearing system on the lower chord of the existing grid structure. Compared with the traditional reinforcement method, the present invention significantly improves the stability and bearing capacity of the structure while reducing the amount of material used.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] An external prestressed reinforcement system for an existing grid structure, wherein the existing grid is composed of steel pipes, and bolt balls are used to connect nodes between adjacent steel pipes.

[0009] The lower ends of some of the bolt ball nodes are connected to vertical braces;

[0010] The bolt ball node is connected to the vertical support rod by opening a through hole at the bottom of the side wall;

[0011] Furthermore, the lower ends of some of the vertical struts are connected with hoop cables, and the hoop cables are distributed according to the span of the grid structure;

[0012] Furthermore, the connection method between the hoop cable and the lower chord of the vertical support rod is as follows: Figure 4 The lower chord of the support rod is connected to the ball cable clamp by welding, and the ring cable body passes through the middle hole of the ball cable clamp for fixed connection. The ear plate is connected to the ball cable clamp by welding. The cable is anchored through the ear plate hole.

[0013] The cable is connected to the upper chord anchor point and the corresponding strut lower chord;

[0014] Furthermore, the upper chord anchor point is as follows: Figure 4 The cable end is fixed to the cable anchor, and the anchor is connected to the support plate.

[0015] By adopting the above technical solution, the hoop cable can effectively control the overall displacement of the grid structure, improve the overall stability of the grid structure, and reduce the local stress concentration phenomenon. Through the cable, the existing grid structure is reinforced by using vertical struts, prestressed steel cables and hoop cables, and the tensile stress formed by the tensioning of the prestressed steel cables can be converted into prestress, and an upward supporting force is generated on the vertical struts, effectively reducing the deformation of the grid structure and improving the strength and stability of the structure. At the same time, this method does not require the disassembly of the existing structure, which effectively improves the efficiency of reinforcement.

[0016] Ring cable arrangement: The ring cable is connected to the vertical struts and prestressed steel cables. Through this surrounding arrangement, the ring cable can effectively control the overall displacement of the grid structure under the action of external forces, and prevent the structure from tilting or excessive displacement due to uneven force.

[0017] Vertical support rod arrangement: The vertical support rods are evenly distributed at the key nodes of the grid structure and are connected to the ring cables and prestressed steel cables. The vertical support rods are set up to improve the overall rigidity of the grid. Through the linkage with the prestressed steel cables, the prestress can be converted into an upward supporting force for the grid, reducing the vertical deformation of the grid structure.

[0018] Prestressed steel cable tensioning: Prestressed steel cables are pre-tensioned through precise tension control, so that the grid structure is in a pre-stressed state. This tension stress is converted into prestress through vertical struts and ring cables, which constrains the grid structure, further reduces local stress concentration, and improves the overall compressive resistance of the structure.

[0019] Comprehensive effect: The combination of ring cables, vertical struts and prestressed steel cables not only provides effective displacement control for the grid structure, but also enhances the integrity and deformation resistance of the structure through reasonable mechanical transmission. Especially under the action of external loads, the tension of the prestressed steel cables can be transmitted to the grid structure through the vertical struts, providing upward support, effectively reducing local stress concentration, and improving the strength and stability of the overall structure.

[0020] A method for reinforcing an existing grid structure with external prestressing, comprising the following steps:

[0021] (a) Determine the specific parameters of the grid structure;

[0022] (b) Determine the position of the hoop according to the span of the grid structure and arrange the vertical braces at the corresponding bolt ball nodes;

[0023] (c) Select the location of the cable anchoring node according to the location of the loop cable;

[0024] (d) arranging the prestressed cables according to the positions of the hoop cables, the positions of the vertical struts, and the positions of the anchor nodes determined in steps (b) and (c);

[0025] (e) The cable body is tensioned as a whole.

[0026] The present invention adopts a prestressed structural system composed of hoop cables, vertical struts and cables, so that the strength and stability of the existing grid structure are improved. Since the existing space structure will be subject to various erosion effects of the environment, the cross-sectional area of ​​the components will be severely weakened and the structural performance will be seriously reduced. Therefore, the present invention provides an external prestressed reinforcement method for the existing grid structure, providing a new idea for improving the performance of the existing space grid structure.

[0027] Compared with the existing grid structure reinforcement technology, the beneficial effects of the present invention are as follows:

[0028] 1. By arranging a ring-shaped cable bearing system, the overall displacement of the structure can be significantly reduced and the stability of the structure can be improved.

[0029] 2. By setting up a ring-shaped cable bearing system at the bottom of the vertical support rod, the maximum stress at the center of the grid structure can be effectively reduced, the local stress concentration phenomenon can be reduced, the structural deflection can be reduced, and the structural bearing capacity can be improved.

[0030] 3. The reinforcement method adopted by the present invention uses less materials, can avoid welding, and can effectively reduce the overall cost while simplifying the construction, which is more economical and practical.

[0031] 4. The reinforcement method proposed in the present invention has strong adaptability. When the structural performance decreases with the increase of the service life of the grid structure, reinforcement can be performed under different usage conditions of the grid structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic flow chart of the method of the present invention.

[0033] Figure 2 This is the layout diagram of the ring rope and the support pole position.

[0034] Figure 3 It is the layout diagram of the cables and anchor points.

[0035] Figure 4 It is a node connection diagram.

[0036] Figure 5 It is the stress ratio diagram of the rod before and after reinforcement.

[0037] Figure 6 It is a schematic diagram of the displacement of the unreinforced structure.

[0038] Figure 7 It is a schematic diagram of the structure after reinforcement using a common cable system.

[0039] Figure 8 It is a schematic diagram of the structure after reinforcement with a ring cable support system. DETAILED DESCRIPTION

[0040] The present invention is further described below in conjunction with an embodiment. It can be seen that this embodiment only uses an upright quadrangular pyramid grid to explain the present invention and is not intended to limit the present invention.

[0041] like Figure 1 As shown, a new method for external prestressing reinforcement of an existing upright tetrahedral pyramid grid comprises the following steps:

[0042] S1. Determine the structural parameters, specifically, the number of spans in the short direction is K1, the number of spans in the long direction is K2, the side length of a single quadrangular pyramid is L, and the height of a single quadrangular pyramid is H.

[0043] S2. According to the result obtained in step S1, determine the position of the hoop and arrange the struts. The suggestion for the position and size of the hoop is 3 / 18 in the long span direction and 4 / 9 in the short span direction.

[0044] S3. Determine the cable anchoring node position based on the result obtained in step S2.

[0045] S4. Based on the results obtained in S2 and S3, the ring cable is connected to the lower chord of the corresponding strut, and the cable is connected to the upper chord anchor point and the lower chord of the corresponding strut.

[0046] S5. Tension the cable body to complete the reinforcement.

[0047] This embodiment applies the above technical solution to the external prestressed reinforcement of an existing upright tetrahedral grid. The main process includes:

[0048] The first step is to determine the specific parameters of the structure. In this embodiment, the number of spans in the long direction of the upright tetrahedral pyramid grid is 18, and the number of spans in the short direction is 9, that is, K1=18, K2=9.

[0049] The second step is to place the ring rope and the support rod Figure 2 Location.

[0050] The third step is to arrange the anchor points and cables. Figure 3 Location.

[0051] The fourth step is to establish a finite element model for analysis and verification.

[0052] The present invention was verified using the ABAQUS finite element program. In the embodiment, K1 in the long direction is 18, the span is 57.6m, K2 in the short direction is 9, the span is 28.8m, the side length L of a single tetrahedron is 3.2m, and the height H is 2.4m. The specifications of the truss members and struts are Φ89×5, the cable specifications are Φ5×13, the prestressing force of the ring cable is 160kN, the height of the strut is 2.0m, the nodes are simplified to rigid connections using cast steel nodes, and the supports are simplified to fixed hinge supports. Node loads are applied to the upper and lower chords of the structure, and the load combination value is 1.3 dead load + 1.5 live load, where the dead load on the upper chord of the structure (excluding the dead weight of the truss) is 3.00kN / m 2 , the bottom chord dead load is 0.5kN / m 2 , live load is 0.5kN / m 2 , upper chord live load is 0.5kN / m 2 , the lower chord live load is taken as 0.5kN / m 2 . The grid is simulated by beam unit B31, the struts are simulated by truss unit T3D2, and the cables are simulated by truss unit T3D2. At the same time, the cable material is set to be tension-only. Static analysis is performed on this model. The results of static analysis show that for the original unreinforced structure, the mid-span of the upper chord of the structure is the position of maximum displacement, and the displacement is greater than 1 / 250 of the shortest span. It does not meet the "Technical Standards for Spatial Grid Structures". The rods at the maximum stress point reach yield, 4.78% of the rods have a stress ratio of more than 0.8, and 2.44% of the rods have a stress ratio of more than 1.0. With the structure reinforced by the present invention, the maximum displacement is reduced by 68.3%, which meets the requirements of the specification. Only 0.5% of the rods have a stress ratio of more than 0.8, and no rod stress exceeds 0.9. Compared with the existing reinforcement form of the cable system, the number of struts is reduced by 83%, and the length of the cable is reduced by 55%, which is obviously more economical.

[0053] The stress of the rod before and after reinforcement is as follows Figure 5 The structural diagram before reinforcement is shown in Figure 6 The schematic diagram of the ordinary cable system after reinforcement is shown in Figure 7 As shown, the structural schematic diagram of the present invention after reinforcement is as follows Figure 8 shown.

[0054] Although the preferred examples of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific implementation method. The above-mentioned specific implementation method is merely an illustrative description and is not restrictive. Under the guidance of the present invention, ordinary technicians in this field can make more forms without departing from the scope of protection of the present invention, the purpose and claims, all of which belong to the protection scope of the present invention.

Claims

1. An external prestressed reinforcement system for an existing grid structure, wherein the existing grid is composed of steel pipes, and bolt-ball connection nodes are used between adjacent steel pipes; the lower ends of some of the bolt-ball nodes are connected to vertical struts; characterized in that: The bolt ball node is connected to the vertical support rod by opening a through hole at the bottom of the side wall.

2. According to claim 1, an external prestressed reinforcement system for an existing grid structure is characterized by: The lower ends of some of the vertical support rods are connected with ring ropes, and the distribution positions of the ring ropes are determined according to the span of the grid structure.

3. The external prestressed reinforcement system of an existing grid structure according to claim 2, characterized in that: In the connection method between the ring cable and the lower chord of the vertical strut, the lower chord of the strut is connected to the ball cable clamp by welding, the ring cable body passes through the middle hole of the ball cable clamp and is fixedly connected; the ear plate is connected to the ball cable clamp by welding; and the cable is anchored through the ear plate hole.

4. The external prestressed reinforcement system of an existing grid structure according to claim 3, characterized in that: The cable is connected to the upper chord anchor point and the corresponding strut lower chord.

5. The external prestressed reinforcement system of an existing grid structure according to claim 4, characterized in that: In the upper chord anchor point, the cable end is fixed to the cable anchor, and the anchor is connected to the support plate.

6. The external prestressed reinforcement system of an existing grid structure according to claim 1, characterized in that: The ring cable can be used to control the overall displacement of the grid structure, improve the overall stability of the grid structure, and reduce local stress concentration. The existing grid structure can be reinforced by using the cable and vertical struts, prestressed steel cables and ring cables. The tension stress formed by the tensioning of the prestressed steel cables can be converted into prestress, and an upward supporting force can be generated on the vertical struts to reduce the deformation of the grid structure and improve the structural strength and stability. There is no need to dismantle the existing structure, thereby improving the reinforcement efficiency.

7. The external prestressed reinforcement system of an existing grid structure according to claim 6, characterized in that: Ring cable arrangement: The ring cables are connected to the vertical struts and prestressed steel cables; through the surrounding arrangement, the ring cables can effectively control the overall displacement of the grid structure under the action of external forces, and prevent the structure from tilting or excessive displacement due to uneven force.

8. The external prestressed reinforcement system of an existing grid structure according to claim 6, characterized in that: Vertical strut arrangement: Vertical struts are evenly distributed at key nodes of the grid structure and are connected to the ring cables and prestressed steel cables. The arrangement of vertical struts can improve the overall stiffness of the grid and, through linkage with the prestressed steel cables, can convert the prestress into an upward supporting force on the grid, thereby reducing the vertical deformation of the grid structure.

9. The external prestressed reinforcement system of an existing grid structure according to claim 6, characterized in that: Prestressed steel cable tensioning: Prestressed steel cables are pre-tensioned by precise tensioning force control, so that the grid structure is in a pre-stressed state; the tensioning stress is converted into prestressing through vertical struts and ring cables, which constrains the grid structure, reduces local stress concentration and improves the overall compressive resistance of the structure; The combination of ring cables, vertical struts and prestressed steel cables provides effective displacement control for the grid structure, and enhances the integrity and deformation resistance of the structure through mechanical transmission. Under the action of external loads, the tension of the prestressed steel cables is transmitted to the grid structure through the vertical struts, providing upward support, effectively reducing local stress concentration, and improving the strength and stability of the overall structure.

10. A method for reinforcing an existing grid structure by external prestressing using the system according to any one of claims 1 to 9, characterized in that: The following steps are involved: (a) Determine the specific parameters of the grid structure; (b) Determine the position of the hoop according to the span of the grid structure and arrange the vertical braces at the corresponding bolt ball nodes; (c) Select the location of the cable anchoring node according to the location of the loop cable; (d) arranging the prestressed cables according to the positions of the hoop cables, the positions of the vertical struts, and the positions of the anchor nodes determined in steps (b) and (c); (e) tensioning the cable body as a whole; The prestressed structural system combining ring cables, vertical struts and cables is adopted to improve the strength and stability of the existing grid structure.

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