Construction method of large-span asymmetric horseshoe multilayer truss

Abstract

This invention discloses a construction method for a large-span, asymmetric, horseshoe-shaped multi-layer truss. The truss and core tube are connected by cantilevered brackets, which are box-shaped structures. The web thickness of the inner cantilevered brackets of the truss and the outer cantilevered brackets of the core tube differs. The truss is assembled on the ground using a positioning jig with multiple distributed support units. Multiple lifting devices installed on the top of the steel pipe columns of the core tube are used to lift the truss as a whole. This invention facilitates local fine-tuning during truss assembly, achieving precise positioning and improving assembly accuracy. The pre-installed inner cantilevered brackets are connected to the outer cantilevered brackets on the core tube, and effective measures are taken to prevent interference, reducing on-site welding work after lifting, facilitating construction, and improving installation quality. By employing a multi-point overall lifting method and effective measures to prevent truss deformation and compensate for docking errors, the installation positioning efficiency and installation quality are greatly improved.

Description

Technical Field

[0001] This invention relates to a method for installing horseshoe-shaped trusses, and more particularly to a construction method for large-span asymmetric horseshoe-shaped multi-layer trusses. Background Technology

[0002] Large-span spatial structures are an important indicator of a country's or region's architectural technology level. With the rapid development of my country's urban economy, large-span steel structures have fully demonstrated their architectural charm and unlimited development potential. Their advantages, such as large span, diverse forms, and beautiful shapes, have led to their widespread application and made them a vibrant area of ​​current architectural structural research. Large-span spatial structures generally utilize steel structures, and as the span increases, the construction difficulty of steel structures also increases. Traditional steel structure installation methods include high-altitude assembly, overall hoisting, and overall lifting. High-altitude assembly requires the erection of numerous temporary support structures, resulting in large quantities of materials and high costs for machinery and labor. Overall hoisting involves assembling the main structure on the ground and then using multiple cranes to simultaneously lift the structure to the designated position. This method demands extremely high synchronization of machinery operation during the construction of large-span structures, and the multi-crane lifting requires significant site space. The overall lifting method utilizes the existing structure as a support point to lift the main structure into place, but it is mostly used for symmetrical structures and requires high precision in the ground assembly of the structure.

[0003] A certain engineering project has a maximum lateral span of 28m, with a concrete substructure and a steel superstructure. The structural form is a barrel-shaped supported, ultra-long, multi-layered, horseshoe-shaped curved spatial steel structure. Its appearance is horseshoe-shaped, with an overall semi-circular plan. The building height is 24m, the outer ring length is 372m, and the inner ring length is 294m; the minimum distance between the inner and outer rings is 15m; the maximum span between the steel columns of the foundation is 48m. This project uses a barrel-shaped core tube to support a large-span, asymmetrical, multi-layered horseshoe-shaped truss. The truss has three layers of web members, with the curvature changing every 6 meters in the projected direction. The truss has large cantilever sections on both sides, with the radius of curvature increasing continuously from the sides towards the center. The truss has 1998 curved box-shaped web members, each with different dimensions and irreplaceable. The truss as a whole is not closed and is asymmetrical. After assembly on the ground, it was lifted to a height of 23.5m in one go using a whole-body lifting process. Traditional large-span steel structure assembly jigs are mostly integral ground jigs made of structural steel, fully laid under the structure. During steel structure assembly, they fit snugly against the underlying integral steel jig to control the elevation and horizontal position of the steel structure. This type of integral steel jig uses a large amount of steel, has a long processing cycle, and is costly; it also occupies a large area, is constrained by the site environment, and is inconvenient to manufacture; and it is not convenient for fine-tuning the local elevation during steel structure assembly. The truss and core tube are connected by cantilevered brackets, which are distributed in four layers circumferentially along the truss, with 28 brackets per layer, totaling 112. The large number of high-altitude joints is challenging. The multi-layered, circumferential arrangement of the joint members makes it easy for the truss to collide with the core tube during lifting, and the accuracy of the bracket joints is difficult to control after lifting and positioning. Summary of the Invention

[0004] This invention provides a construction method for large-span asymmetric horseshoe-shaped multi-layer trusses to solve the technical problems existing in the prior art. This method is easy to install, has high precision, good installation quality, and low cost.

[0005] The technical solution adopted by this invention to solve the technical problems existing in the prior art is as follows: a construction method for a large-span asymmetric horseshoe-shaped multi-layer truss, wherein the truss is supported by multiple barrel-shaped core tubes, each core tube is provided with four large-angle giant steel pipe columns, the truss is provided with inner and outer ring oblique trusses, and the inner and outer ring oblique trusses are provided with multiple layers of web members between the upper chord and the lower chord, and the web members of each layer of the inner and outer ring oblique trusses and the upper and lower chords are connected by platform beams; multiple cantilevered brackets are welded to each steel pipe column, arranged sequentially from top to bottom, the length of the cantilevered brackets decreasing from top to bottom, and inner cantilevered brackets are set on the web members of the truss to connect one-to-one with the cantilevered brackets. Both the cantilevered brackets and the inner cantilevered brackets are box-shaped structures with different web plate thicknesses and a ratio of 0.7 to 0.8; the installation method of the truss is as follows:

[0006] 1) A truss structure model is established using BIM technology. Each member is numbered and its information is loaded. A QR code is generated and marked on the member. The construction process is tracked in real time by recognizing the QR code. The structural stress analysis is performed using Midas software. Based on the analysis results, a lifting point is determined on the top of each column of the core tube. Hydraulic lifters are configured at each lifting point according to the standard value of the reaction force obtained from the stress analysis. 2) Ground assembly is performed using the following steps: 2.1) A positioning jig is set up on the ground directly below the truss installation position. The positioning jig includes multiple support units distributed according to the horizontal arrangement curve of the lower chord of the inner and outer oblique trusses. Each support unit is equipped with two four-legged table structures. The two four-legged table structures are arranged leg-to-leg, with a lifting cavity at the joint of the table legs. An operating opening is provided on one side of the lifting cavity, and a hydraulic jack is installed inside the lifting cavity. The upper four-legged table structure is provided with a support panel; 2.2) The upper surface of the support panel of the super-flat positioning jig; 2.3) Assemble the lower chords of the inner and outer ring oblique trusses on the support panel of the positioning jig. After the horizontal position of the lower chords of the inner and outer ring oblique trusses is adjusted to the correct position, left and right limiting components are used for limiting; 2.4) The bottom surface of the lower chords of the inner and outer ring oblique trusses is super-flattened by adjusting the hydraulic jacks of the positioning jig; 2.5) The two table legs of the positioning jig are fixed together by connecting components; 2.6) The web members of the truss and the corresponding platform beams and upper... are installed layer by layer. Before installation, the upper chords of the inner and outer ring skew trusses on both sides of each core tube are arched downwards. During the installation of the truss web members and platform beams, the cantilevered corbels are welded inwards. 2.7) Four lower lifting points are set around one core tube on the upper chord of the inner and outer ring skew trusses. These four lower lifting points correspond one-to-one with the upper lifting points on the core tube. A lifting device is installed at each lower lifting point. A temporary reinforcement structure is set at the bottom of the fixed end of the truss cantilever section. A permanent reinforcement structure is set inside the upper chord of the inner and outer ring skew trusses below the lifting device. 3) Lifting and installation are carried out using the following steps: 3.1) Mark the positioning points on the lifting platform, set up a total station on the ground, and calculate the horizontal distance based on the theoretical horizontal distance and the measured horizontal distance through coordinate transformation. The difference is used to position and fix the lifting platform at the top of the steel pipe column based on the marked positioning point; 3.2) Install the lifting system, which includes a hydraulic lifting device, a synchronous control system and a hydraulic pump source system. Install the hydraulic lifting device at the upper lifting point position on the lifting platform and install the lifting device at the lower lifting point position of the upper chord of the truss. Then, use bottom anchors and steel strands to connect the hydraulic lifting device and the lifting device together; 3.3) Based on the standard value of the reaction force at each lifting upper lifting point, perform graded loading on the truss to ensure that the truss rises synchronously as a whole; 3.4) After the truss is lifted into place, complete the high-altitude docking of the truss and the core tube, and connect the inner cantilever corbels and outer cantilever corbels that are reserved for movement space and distributed in a stepped staggered manner one by one; 3.5) Unloading in groups and stages: After the installation of the post-installed rods between every two adjacent core tubes is completed, the hydraulic lifters on the upper part of those two adjacent core tubes are unloaded in stages; 3.6) After the hydraulic lifters are unloaded, the temporary supports are removed.

[0007] The lifting platform is provided with a lifting cantilever extending outward along the length of the outward cantilever bracket, and the hydraulic lifter is fixed on the cantilever end of the lifting cantilever.

[0008] The difference in length between two adjacent outwardly extending cantilevered corbels is the same, and can be any value between 80 and 120 mm.

[0009] The design interval between the outward and inward cantilever corbels is the same, which is any value between 10 and 15 mm.

[0010] The temporary reinforcement structure adopts a transverse truss, which is connected between the inner and outer ring diagonal trusses.

[0011] The permanent reinforcement structure is provided with four vertical stiffening plates with the same cross-section as the lifting device, arranged in a "well" shape.

[0012] The legs and frame of the four-legged table structure are made of square tubing. A horizontal support plate is provided on the inner bottom of the legs, and the lifting cavity is located between two opposing horizontal support plates.

[0013] The connector is made of steel plate.

[0014] The advantages and positive effects of this invention are:

[0015] 1) Applying BIM technology enables real-time dynamic tracking of the construction process, achieving visualized process management. BIM software is used to convert the originally planar, fixed steel structure design drawings into a three-dimensional model. Each member in the BIM 3D solid structure model is then individually numbered, and its material, dimensions, center of gravity, and weight are edited in the attached information. Progress information is also loaded for each member to record its status during material preparation, fabrication, shot blasting, painting, transportation, and on-site installation. In the model, each member is marked with a corresponding color according to its different process status, allowing for dynamic control of the component's production and processing progress. Each member is affixed with a unique QR code upon leaving the factory; workers can scan this code to obtain the member's attached information, ensuring strong traceability of construction quality.

[0016] 2) The truss is assembled on a jig, allowing for fine-tuning and high precision. By assembling the truss on the ground using a positioning jig formed by multiple distributed, adjustable support units, local fine-tuning is facilitated, enabling precise positioning and improving assembly accuracy.

[0017] 3) Enhanced reinforcement ensures safety and reliability. A combination of temporary and permanent reinforcement is used to strengthen the lifting unit, ensuring the structural safety and stability during truss lifting. This approach is cost-effective and economical.

[0018] 4) Smooth lifting of large-span, asymmetrical, multi-layered horseshoe-shaped trusses. Structural stress analysis was performed using Midas software. Based on the analysis results, the specific locations of the lifting points on the top of the core tube columns were determined, and a lifting platform was constructed. The lifting platform was made of welded steel sections, with a U-shaped groove in the cantilever, and a hydraulic lifting device was installed on top. Steel strands passed through the U-shaped groove. Different types of lifting equipment were configured at each lifting point according to the different standard reaction values ​​obtained from the stress analysis. During lifting, a lifting force was applied according to the standard reaction value, thus ensuring the smooth lifting of the large-span, asymmetrical, multi-layered horseshoe-shaped truss.

[0019] 5) The use of a prism-free installation process for the lifting equipment ensures the safety of surveyors working at heights. Positioning points are marked on the lifting platform, and a total station is set up on the ground. Through coordinate conversion, the difference in horizontal distance is calculated based on the theoretical and measured horizontal distances. Using the marked positioning points as a reference, the lifting platform is positioned. This eliminates the need for high-altitude prism installation for layout, avoiding the need for surveyors to work near edges at heights and ensuring construction safety.

[0020] 6) The use of hydraulic synchronous lifting technology for the overall lifting of the truss significantly reduces installation difficulty. The steel structure truss is assembled as a whole on the ground directly below its projection plane. Upper lifting points are set on the tops of the core tube steel columns, and lower lifting points are set at corresponding positions on the truss. The upper and lower lifting points are connected by bottom anchors and steel strands. The hydraulic synchronous lifting system is used to lift the entire truss to the designed installation position. The hydraulic lifting system consists of three parts: a hydraulic lifter, a synchronous control system, and a hydraulic pump source system. The overall weight of the hydraulic lifting system is relatively light, facilitating transportation and installation. The anchors of the hydraulic lifter have reverse movement self-locking properties, allowing the components to be reliably locked at any position during the lifting process, ensuring safety.

[0021] 7) Graded loading ensures lifting safety. Based on the standard value of reaction force, the truss is subjected to graded loading to ensure the synchronicity of the rise of each lifting point and the overall stability of the truss structure.

[0022] 8) Anti-interference measures are adopted to avoid collisions between members during the lifting process. Pre-installed inner cantilever brackets are connected to outer cantilever brackets on the core tube. The inner and outer cantilever brackets are provided with a space for movement and are distributed in a stepped, staggered manner. At the same time, the upper chord of the truss is arched in the opposite direction, which can avoid collisions during the lifting process and reduce the amount of high-altitude welding work on site after lifting, thus facilitating the improvement of installation quality.

[0023] 9) Adopting multi-bracket high-altitude docking anti-misalignment measures to improve docking accuracy. The web plates of the inner and outer cantilever brackets are designed with different thicknesses. When the truss is lifted into place and docked with the core tube at high altitude, the difference in thickness of the two web plates provides a misalignment margin for high-altitude docking, improving the docking accuracy of the circumferentially distributed, multi-layered, one-to-one-corresponding brackets.

[0024] 10) Group and staged unloading accelerates the unloading process and ensures unloading safety. After the installation of the post-installed rods between every two adjacent core tubes is completed, the lifting devices on the upper part of the two adjacent core tubes can be unloaded. During the group unloading process, the hydraulic lifting device cylinder pressure is gradually reduced, and unloading is carried out in stages. The pressure and displacement values ​​in the computer control system are closely monitored. If any data is abnormal, the process is stopped immediately to prevent load transfer during the unloading process and ensure the safety of unloading. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process of the present invention;

[0026] Figure 2 A schematic diagram of a steel structure for applying this invention;

[0027] Figure 3 A schematic diagram of the truss structure for applying the present invention;

[0028] Figure 4 A schematic diagram illustrating the structure of the truss assembled on the ground using a positioning jig for applying this invention;

[0029] Figure 5 This is a schematic diagram of the support unit used in this invention;

[0030] Figure 6 This is a schematic diagram of the upper four-legged table structure of the support unit used in this invention;

[0031] Figure 7 This is a schematic diagram of the lower four-legged table structure of the support unit used in this invention;

[0032] Figure 8 This is a schematic diagram of the temporary reinforcement structure used in this invention;

[0033] Figure 9 This is a schematic diagram of the cantilever end of the truss;

[0034] Figure 10 This is a schematic diagram illustrating the improvement of the present invention;

[0035] Figure 11 This is a schematic diagram of the lifting and positioning of the present invention;

[0036] Figure 12 This is a schematic diagram of the installation of the lifting device used in this invention;

[0037] Figure 13 This is a schematic diagram of the permanent reinforcement structure used in this invention;

[0038] Figure 14 This is a schematic diagram illustrating the high-altitude connection between the outward and inward cantilevered brackets of the present invention.

[0039] In the diagram: 1. Truss; 1-1. Inner ring oblique truss; 1-2. Outer ring oblique truss; 1-1-1. Top chord; 1-1-2. Bottom chord; 1-1-3. Web member; 1-1-4. Platform beam; 1-1-5. Inward cantilever corbel; 2. Core tube; 2-1. Steel pipe column; 2-1-1. Outward cantilever corbel; 3. Support unit; 3-1. Four-legged table structure; 3-1-1. Table leg; 3-1-2. Horizontal support plate; 3-2. Hydraulic jack; 3-3. Connector; 3-4. Support panel; 4. Lifting device; 5. Hydraulic lifter; 6. Lifting platform; 6-1. Lifting cantilever; 7. Horizontal truss; 8. Vertical stiffening plate; 9. Outward cantilever corbel web plate; 10. Inward cantilever corbel web plate. Detailed Implementation

[0040] To further understand the invention's content, features, and effects, the following embodiments are provided, along with detailed descriptions in conjunction with the accompanying drawings:

[0041] Please refer to the attached drawings. A construction method for a large-span asymmetric horseshoe-shaped multi-layer truss is described. The truss 1 is supported by multiple barrel-shaped core tubes 2. Each core tube 2 is provided with four large-angle giant steel pipe columns 2-1. The truss 1 is provided with an inner ring oblique truss 1-1 and an outer ring oblique truss 1-2. Both the inner ring oblique truss 1-1 and the outer ring oblique truss 1-2 are provided with multiple layers of web members 1-1-3 between the upper chord 1-1-1 and the lower chord 1-1-2. The web members 1-1-3 of the inner ring oblique truss 1-1 and the outer ring oblique truss 1-2, as well as the upper chord 1-1-1 and the lower chord 1-1-2, are connected by platform beams 1-1-4.

[0042] Multiple cantilevered brackets 2-1-1 are welded onto each steel pipe column 2-1, arranged sequentially from top to bottom. The length of the cantilevered brackets decreases sequentially from top to bottom. Inner cantilevered brackets 1-1-5 are installed on the web members of the truss, which are connected one-to-one with the cantilevered brackets 2-1-1. Both the cantilevered brackets 2-1-1 and the inner cantilevered brackets 1-1-5 adopt a box-shaped structure. The web plates 9 and 10 of the cantilevered brackets have different thicknesses, and the ratio is 0.7 to 0.8.

[0043] The truss is assembled on the ground using the following steps:

[0044] 1) Use BIM technology to establish a truss structure model, number and load information for each member, generate a QR code for the information and mark it on the member, and use the QR code to track the construction process in real time; use midas software to perform structural stress analysis, and determine a lifting point on the top of each column of the core tube according to the analysis results. Configure a hydraulic lifter at each lifting point according to the standard value of the reaction force obtained from the stress analysis.

[0045] 2) Ground assembly, using the following steps:

[0046] 2.1) A positioning frame is set on the ground directly below the installation position of the truss 1. The positioning frame includes multiple support units 3 arranged in a horizontal curve according to the lower chords 1-1-2 of the inner and outer ring oblique trusses 1-1 and 1-2. Each support unit 3 is provided with two four-legged table structures 3-1, with the two four-legged table structures 3-1 arranged leg-to-leg. A lifting cavity is provided at the joint of the table legs 3-1-1. An operating opening is provided on one side of the lifting cavity. A hydraulic jack 3-2 is provided in the lifting cavity. The upper four-legged table structure 3-1 is provided with a support panel 3-4.

[0047] 2.2) The upper surface of the ultra-flat positioning frame support panel 3-4.

[0048] 2.3) Assemble the lower chords 1-1-2 of the inner and outer ring oblique trusses on the support panel 3-4 of the positioning jig. After the horizontal position of the lower chords 1-1-2 of the inner and outer ring oblique trusses is adjusted to the correct position, use left and right limiting parts for limiting.

[0049] 2.4) Adjust the bottom surface of the lower chord 1-1-2 of the inner and outer ring oblique trusses of the positioning jig by adjusting the hydraulic jack 3-2 of the positioning jig.

[0050] 2.5) The two table legs 3-1-1 of the positioning frame are fixed together by the connector 3-3.

[0051] 2.6) Install the web members 1-1-3 and corresponding platform beams 1-1-4 and upper chord members 1-1-1 of truss 1 layer by layer. Before installing the upper chord members 1-1-1 of the inner and outer ring oblique trusses located on both sides of each core tube 2, make downward arching treatment. During the installation of the web members 1-1-3 and platform beams 1-1-4 of the truss, weld the inner cantilever brackets 1-1-5.

[0052] 2.7) Four lower lifting points are set around a core tube 2 on the upper chord 1-1-1 of the inner and outer ring oblique trusses. These four lower lifting points correspond one-to-one with the lifting upper lifting points on the core tube. A lifting device 4 is installed at each lower lifting point. A temporary reinforcement structure is set at the bottom of the fixed end of the cantilever section of the truss 1. A permanent reinforcement structure is set inside the upper chord 1-1-1 of the inner and outer ring oblique trusses below the lifting device 4.

[0053] 3) Upgrade installation, using the following steps:

[0054] 3.1) Mark the positioning point on the lifting platform 6, set up a total station on the ground, and calculate the difference between the theoretical horizontal distance and the actual horizontal distance through coordinate transformation. The lifting platform 6 is positioned and fixed on the top of the steel pipe column with the marked positioning point as the reference.

[0055] 3.2) Install the lifting system:

[0056] The lifting system includes a hydraulic lifter 5, a synchronous control system, and a hydraulic pump source system. The hydraulic lifter 5 is installed at the upper lifting point on the lifting platform 6, and the lifting device 4 is installed at the lower lifting point on the upper chord 1-1-1 of the truss. Then, the hydraulic lifter 5 and the lifting device 4 are connected together using bottom anchors and steel strands.

[0057] 3.3) Based on the standard value of the reaction force at each lifting point, the truss 1 is subjected to graded loading to ensure that the truss 1 rises synchronously as a whole.

[0058] 3.4) After the truss 1 is lifted into place, the high-altitude docking of the truss 1 and the core tube 2 is completed, and the inner cantilever brackets 1-1-5 and the outer cantilever brackets 2-1-1, which are arranged in a stepped and staggered manner with reserved activity space, are connected one by one.

[0059] 3.5) Grouped and graded unloading

[0060] After the installation of the post-installed rods between every two adjacent core tubes 2 is completed, the hydraulic lifters 5 on the upper part of the two adjacent core tubes 2 are unloaded in stages.

[0061] 3.6) After the hydraulic lifter 5 is unloaded, remove the temporary support.

[0062] In this embodiment, a more specific method is as follows: the lifting platform 6 is provided with a lifting cantilever 6-1 extending outward along the length of the core tube steel box girder, and the lifting device 5 is fixed on the cantilever end of the lifting cantilever 6-1. The length difference between two adjacent extended cantilever brackets 2-1-1 is the same, and is any value between 80 and 120 mm. The design interval between the connected extended cantilever brackets 2-1-1 and the inner cantilever brackets 1-1-5 is the same, and is any value between 10 and 15 mm. The temporary reinforcement structure adopts a transverse truss 7, which connects the inner and outer ring oblique trusses. The permanent reinforcement structure is provided with four vertical stiffening plates 8 with the same cross-section as the lifting device 4, arranged in a "well" shape. The legs 3-1-1 and frame of the four-legged table structure 3-1 are made of square tubing. A horizontal support plate 3-1-2 is provided on the inner bottom of the legs, and the lifting cavity is located between two opposing horizontal support plates 3-1-2. The connector 3-3 is made of steel plate.

[0063] Features of this invention:

[0064] 1) Truss ground assembly

[0065] Truss 1 is assembled on a positioning jig. The lower chords 1-1-2 of the inner and outer ring oblique trusses are mounted on the jig in sections. The overall curvature of the lower chords 1-1-2 is controlled by adjusting the horizontal position and installation elevation of each section of the lower chord 1-1-2.

[0066] During assembly, positioning jigs are placed every three meters along the ink lines projected onto the lower chord 1-1-2. Ensuring the accuracy of the positioning jigs is crucial for ensuring the assembly accuracy of truss 1. After the positioning jigs are arranged, the planar position and elevation of the four corner points and the midpoint of the positioning jig support panel 3-4 are checked using a total station. The center line and edge line of the lower chord 1-1-2 to be installed are then marked with ink lines. After the lower chord 1-1-2 is hoisted onto the jig, it is first measured using a total station with the aid of a steel tape measure. After fine-tuning, the planar position of the lower chord 1-1-2 is fixed with limiting devices. Then, the elevation of the lower chord 1-1-2 is re-measured using a level to ensure that the bottom surface of the lower chord 1-1-2 is at the same elevation.

[0067] When there is a deviation in the elevation of the lower chord 1-1-2, adjust the hydraulic jack 3-2 inside the positioning jig leg 3-1-1 to adjust the bottom elevation of the lower chord 1-1-2. After repeatedly adjusting each control point to precision, spot weld the two adjacent lower chords 1-1-2 to fix them, and then carry out the formal welding.

[0068] The web members 1-1-3 and the platform beam are installed layer by layer based on the lower chord member 1-1-2 of the truss.

[0069] The lower chord 1-1-2 of truss 1 is divided into segments, making it easier to control the curvature of individual segments. The lower chord 1-1-2 is assembled on a positioning jig, with each segment of the lower chord 1-1-2 being assembled from both sides towards the middle. The spatial position and installation elevation of each segment of the lower chord 1-1-2 are restricted for positioning. This process gradually eliminates accumulated errors and ensures the assembly accuracy of truss 1.

[0070] 2) Truss reinforcement

[0071] Because truss 1 has a large span and excessively long cantilever, it needs to be reinforced to ensure the safety and stability of the structure during lifting. Permanent reinforcement would expose the structural components and affect the appearance, while temporary reinforcement would need to be removed after lifting, which is economical. Therefore, a combination of temporary and permanent reinforcement is used to strengthen the lifting unit and ensure the safety and stability of the structure during lifting. Specific measures are as follows:

[0072] A temporary reinforcement structure is installed at the cantilever end. The temporary reinforcement structure is installed between the bottom layers of the cantilever section of the truss. A transverse truss 7 is welded from H-beams to connect the inner ring skew truss 1-1 and the outer ring skew truss 1-2 of the cantilever section.

[0073] During the overall lifting process, the lifting unit mainly bears the vertical load generated by its own weight. Therefore, the upper chord 1-1-1 of the truss 1 is a weak member, and the position corresponding to the lifting device 4 is the weakest. Therefore, when processing the upper chord 1-1-1, according to the structural model, the installation position of the lifting device on the upper chord 1-1-1 of the truss is found. The corresponding installation position of the lifting device is to weld a permanent vertical stiffening plate 8 inside the upper chord 1-1-1 of the truss. The thickness of the vertical stiffening plate 8 is the same as the web wall thickness of the upper chord 1-1-1.

[0074] 3) Interference prevention during docking

[0075] The inner cantilever bracket 1-1-5, connecting truss 1 to the barrel-shaped core tube steel pipe column 2-1, is the most important load-bearing structure. To reduce the amount of high-altitude welding after lifting and positioning, the outer cantilever bracket 2-1-1 and the inner cantilever bracket 1-1-5 are pre-welded to the steel pipe column 2-1 and truss 1. However, this may cause the inner cantilever bracket 1-1-5 on truss 1 to collide with the outer cantilever bracket 2-1-1 on steel pipe column 2-1 during lifting, preventing normal lifting. To solve this problem, the following three measures are adopted:

[0076] 3.1) The cantilevered brackets 2-1-1 on each layer and the inward cantilevered brackets 1-1-5 on each layer of truss 1 are distributed in a stepped manner. The length of the cantilevered brackets 2-1-1 decreases from top to bottom, with a difference of 80-120mm between each layer, while the inward cantilevered brackets 1-1-5 increase from bottom to top, with a difference of 80-120mm between each layer. This method ensures that during the lifting process, the inward cantilevered brackets 1-1-5 on each layer can only collide with the cantilevered brackets 2-1-1 on the corresponding layer, and will not collide with the cantilevered brackets 2-1-1 on other layers.

[0077] 3.2) In order to resolve the possibility of collision between the outward cantilever bracket 2-1-1 and the inward cantilever bracket 1-1-5 on this floor, a gap of 10-15mm is left on each side.

[0078] 3.3) To further reduce the possibility of collision between the inner cantilever bracket 1-1-5 on truss 1 and the outer cantilever bracket 2-1-1 on the steel pipe column of this floor, the upper chord 1-1-1 of the inner and outer ring oblique trusses located on both sides of each core tube is arched downward.

[0079] 4) The advantages of hydraulic synchronous overall lifting have been detailed in the beneficial effects section and will not be repeated here.

[0080] 5) High-altitude docking to prevent deviation

[0081] After the structure is lifted into place, the corresponding outward cantilever brackets 2-1-1 and inward cantilever brackets 1-1-5 need to be welded together. Due to the large number of joints, preventing the multiple cantilever brackets from shifting at high altitude during the overall lifting of the truss structure is a key challenge in the construction.

[0082] Using structural calculation software, the weld strength of the two connected components is calculated. After ensuring that the weld width and penetration depth meet the structural stress requirements, the web plates 10 and 9 of the inner and outer cantilever corbels are designed to have different thicknesses with a ratio of 0.7 to 0.8. When the outer cantilever corbel 2-1-1 and the inner cantilever corbel 1-1-5 are connected at high altitude, the web plates 10 and 9 are aligned center-to-center to align the centerlines of the two web plates in the height direction. Since there is a deviation in the thickness of the two web plates, a misalignment allowance is provided for the high-altitude connection of the outer cantilever corbel 2-1-1 and the inner cantilever corbel 1-1-5.

[0083] Although preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other modifications under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these modifications are within the scope of protection of the present invention.

Claims

1. A construction method for a large-span asymmetric horseshoe-shaped multi-layer truss, wherein the truss is supported by multiple barrel-shaped core tubes, each core tube is provided with four large-angle giant steel pipe columns, the truss is provided with inner and outer ring oblique trusses, and the inner and outer ring oblique trusses are provided with multiple layers of web members between the upper chord and the lower chord, and the web members of each layer of the inner and outer ring oblique trusses and the upper and lower chords are connected by platform beams; characterized in that Multiple cantilevered brackets are welded to each steel pipe column, arranged sequentially from top to bottom. The length of the cantilevered brackets decreases sequentially from top to bottom. Inner cantilevered brackets are installed on the web members of the truss, which are connected one by one with the cantilevered brackets. Both the cantilevered brackets and the inner cantilevered brackets adopt a box-shaped structure with different web thicknesses and a ratio of 0.7 to 0.

8. The truss is installed using the following steps: 1) Use BIM technology to build a truss structure model, number and load information for each member, generate a QR code for the information and mark it on the member, and use the QR code to track the construction process in real time; use midas software to perform structural stress analysis, and determine a lifting point on the top of each column of the core tube according to the analysis results. Configure hydraulic lifters at each lifting point according to the standard value of the reaction force obtained from the stress analysis. 2) Ground assembly, using the following steps: 2.1) A positioning frame is set on the ground directly below the truss installation position. The positioning frame includes multiple support units distributed according to the horizontal arrangement curve of the lower chord of the inner and outer ring oblique trusses. Each support unit is provided with two four-legged table structures with legs facing each other. A lifting cavity is provided at the joint of the table legs. An operating opening is provided on one side of the lifting cavity. A hydraulic jack is provided in the lifting cavity. The upper four-legged table structure is provided with a support panel. 2.2) The upper surface of the support panel of the ultra-flat positioning jig; 2.3) Assemble the lower chords of the inner and outer ring oblique trusses on the support panel of the positioning jig. After the horizontal position of the lower chords of the inner and outer ring oblique trusses is adjusted to the correct position, use left and right limiting parts for limiting. 2.4) Adjust the bottom surface of the lower chord of the inner and outer ring oblique trusses by adjusting the hydraulic jacks of the positioning jig; 2.5) The two table legs of the positioning frame are fixed together using connectors; 2.6) Install the web members of the truss and the corresponding platform beams and top chords layer by layer. Before installing the top chords of the inner and outer ring skew trusses on both sides of each core tube, make downward arching treatment. Weld the inner cantilever brackets during the installation of the web members and platform beams. 2.7) Four lower lifting points are set around a core tube on the upper chord of the inner and outer ring skew trusses. These four lower lifting points correspond one-to-one with the lifting upper lifting points on the core tube. A lifting device is installed at each lower lifting point. A temporary reinforcement structure is set at the bottom of the fixed end of the cantilever section of the truss. A permanent reinforcement structure is set inside the upper chord of the inner and outer ring skew trusses located below the lifting device. 3) Upgrade installation, using the following steps: 3.1) Mark the positioning point on the lifting platform, set up a total station on the ground, and calculate the difference between the theoretical horizontal distance and the actual horizontal distance through coordinate transformation. The lifting platform is positioned and fixed on the top of the steel pipe column with the marked positioning point as the reference. 3.2) Install the lifting system The lifting system includes a hydraulic lifter, a synchronous control system, and a hydraulic pump source system. The hydraulic lifter is installed at the upper lifting point on the lifting platform, and the lifting device is installed at the lower lifting point on the upper chord of the truss. Then, the hydraulic lifter and the lifting device are connected together using bottom anchors and steel strands. 3.3) Based on the standard value of the reaction force at each lifting point, the truss is subjected to graded loading to ensure that the truss rises synchronously as a whole; 3.4) After the truss is lifted into place, complete the high-altitude docking of the truss and the core tube, and connect the inner cantilever brackets and outer cantilever brackets that are reserved for movement space and are distributed in a stepped and staggered manner. 3.5) Grouped and graded unloading After the installation of the post-installed rods between every two adjacent core tubes is completed, the hydraulic lifters on the upper part of the two adjacent core tubes are unloaded in stages. 3.6) After the hydraulic lifter is unloaded, remove the temporary support.

2. The construction method of a long-span asymmetric horseshoe multi-layer truss according to claim 1, characterized in that, The lifting platform is provided with a lifting cantilever extending outward along the length of the outward cantilever bracket, and the hydraulic lifter is fixed on the cantilever end of the lifting cantilever.

3. The construction method of a long span asymmetric horseshoe multi-layer truss according to claim 1, characterized in that, The difference in length between two adjacent outwardly extending cantilevered corbels is the same, and can be any value between 80 and 120 mm.

4. The construction method of a long span asymmetric horseshoe multi-layer truss according to claim 1, characterized in that, The design interval between the outward and inward cantilever corbels is the same, which is any value between 10 and 15 mm.

5. The construction method of a long span asymmetric horseshoe multi-layer truss according to claim 1, characterized in that, The temporary reinforcement structure adopts a transverse truss, which is connected between the inner and outer ring diagonal trusses.

6. The construction method for large-span asymmetric horseshoe-shaped multi-layer trusses according to claim 1, characterized in that, The permanent reinforcement structure is provided with four vertical stiffening plates with the same cross-section as the lifting device, arranged in a "well" shape.

7. The construction method for large-span asymmetric horseshoe-shaped multi-layer trusses according to claim 1, characterized in that, The legs and frame of the four-legged table structure are made of square tubing. A horizontal support plate is provided on the inner bottom of the legs, and the lifting cavity is located between two opposing horizontal support plates.

8. The construction method for large-span asymmetric horseshoe-shaped multi-layer trusses according to claim 1, characterized in that, The connector is made of steel plate.

Images