Construction method of spatial truss with prestressed structure

Abstract

The application discloses a kind of space truss construction methods containing prestressed structure, comprising the following steps: step 1: simulation calculation, lifting point design;Step 2: according to step 1, simulation calculation, determine the prestressed tension mode;Step 3: according to the calculation results of step 1 and step 2, actual construction is carried out;Wherein, in step 2, by model calculation, set model parameters, obtain the best tension mode of prestress, to reduce the influence of tension prestress on original structure, the model parameters in step 2 are: the comprehensive stress ratio of original structure is not more than 0.8, displacement is not more than 1 / 250.The application optimizes prestressed tension method and sequence, reasonably designs lifting point and sets up hydraulic jack and the method of phased synchronous etc. unloading, guarantees the stability of structure in the whole construction process and the convenience of construction, improves the safety of construction.

Description

Technical Field

[0001] This invention relates to the field of steel structure construction, and more specifically to a method for constructing a space truss with a prestressed structure. Background Technology

[0002] The statements in this section provide only background information relevant to the disclosure of this application and may not constitute prior art.

[0003] With the development of the national economy and urbanization, many cities need to build various museums, exhibition halls, concert halls, stadiums and airports to meet the needs of urban development and improve the city's image. These buildings are often landmark buildings of a city, representing the level of urban development. To achieve these effects, these buildings often need to adopt personalized appearance and unique irregular structure. These structures are not only complex in construction and have unique shapes, but also often use new structural constructions designed with the latest design theories. Therefore, traditional and single construction techniques can no longer meet the technical requirements of these buildings.

[0004] There are many technical challenges in constructing spatial steel pipe truss structures.

[0005] 1. How to prevent steel strands from becoming tangled during the threading process; Due to its own weight, the steel cable will naturally sag in the middle after both ends are tightened. The steel strands that are threaded later are prone to getting tangled with the steel strands in front, which will affect the pulling effect.

[0006] 2. How to set up lifting points and hydraulic jacks to ensure the overall synchronous lifting of the space truss structure;

[0007] 3. How to design a reasonable lifting point structure so that the lifting and closing can be carried out directly without replacing the rod first.

[0008] 4. How to ensure synchronization and stability during the unloading of the roof truss. Summary of the Invention

[0009] The purpose of this invention is to provide a construction method for space trusses with prestressed structures, which addresses the current technical challenges and reduces the impact of prestressed construction on existing structures, thereby improving the convenience and safety of construction.

[0010] The technical solution of the present invention is as follows:

[0011] A construction method for a space truss containing a prestressed structure includes the following steps:

[0012] Step 1: Design the suspension points by modeling using structural software;

[0013] Step 2: Based on the lifting points and using structural software, determine the prestressing tensioning method;

[0014] Step 3: Conduct actual construction based on the lifting points and prestressing tensioning method.

[0015] According to a preferred embodiment, the suspension point is set based on the deflection value or the location of the force.

[0016] According to a preferred embodiment, step 2 includes: determining the optimal prestressing tensioning method by setting model parameters based on the lifting points and structural software.

[0017] The model parameters include: the original structure's comprehensive stress ratio not exceeding 0.8, the displacement not exceeding 1 / 250, and reference values ​​that are consistent with the maximum camber value during truss assembly and the deflection value under self-weight.

[0018] Existing single-tension prestressing construction methods, when used, are prone to two problems because the prestressing tension is the design value under normal roof structure conditions. This is because the roof load may not be fully applied during prestressing construction: 1) Insufficient unloading may occur when the prestressing acts as an unloading agent; 2) Overloading may occur when the prestressing acts as a load-increasing agent. To avoid these problems, this application determines the appropriate prestressing magnitude and tensioning method based on the different structural stages of construction. Different magnitudes of prestressing are applied at different construction stages to ensure that the prestressing applied at each stage does not negatively impact the structure.

[0019] According to a preferred embodiment, step 3 further includes the following sub-steps:

[0020] Step 3.1: Construct the main truss and assemble the jig;

[0021] Step 3.2: Try to improve;

[0022] Step 3.3: After lifting and positioning, align the main truss.

[0023] Step 3.4: Proceed to the second stage of installation;

[0024] Step 3.5: After the second section is installed, unload the temporary support bracket.

[0025] In steps 3.1-3.5, prestressing is simultaneously performed according to the prestressing tensioning method determined in step 2, including graded prestressing, step-by-step prestressing, and sequential prestressing. "Synchronized" means that step-by-step tensioning is performed during each graded tensioning stage, and sequential tensioning is performed within each step-by-step tensioning stage.

[0026] According to a preferred embodiment, the prestressed graded tensioning includes: the first stage is prestressing in stages during the threading of steel cables to prevent interference between each group of steel strands; the second stage is prestressing the truss on the assembly jig, with the tension value determined based on computer simulation of structural stress; the third stage is tensioning after lifting; after lifting and bringing the truss to rest, it is then tensioned in stages to the final design value.

[0027] The prestressing step-by-step tensioning includes: tensioning the prestress to a predetermined value in multiple steps according to a certain prestressing change gradient;

[0028] The prestressed sequential tensioning includes: threading the prestressed steel strands in a top-to-bottom, right-to-left order; and tensioning the steel strands in opposite directions sequentially from bottom to top. Multiple sets of steel strands need to be threaded through the steel pipe, and the strands are quite long. After the ends of the steel strands are tightened, there will be a natural downward deflection in the middle. This threading sequence prevents the later-threaded steel strands from interfering with the earlier ones, ensuring that the groups are not confused.

[0029] Because the roof's self-weight is borne by temporary supports before lifting, and the lower chord of the steel pipe is not under tension, the prestressing tension cannot counteract the tension on the lower chord. Instead, it can easily lead to excessive stress at the prestressing tensioning location. To minimize the impact of prestressing tensioning on the original structure, simulation calculations at each stage are needed. Adopting a step-by-step, graded, and sequential tensioning method can yield more favorable prestressing tensioning steps and matching tensioning force values, thus reducing the impact on the original structure.

[0030] According to a preferred embodiment, in step 1, the suspension points are designed through modeling, and the arrangement of suspension points is mainly set according to the parts with large deflection values ​​or large forces during simulation calculation.

[0031] According to a preferred embodiment, in step 3.2, the configuration of the lifting point crane is as follows: while meeting the load requirements of the lifting point, the hydraulic reaction force is fed back through the built-in sensor to adjust so that the load on each lifting device is equal; the number of hydraulic devices driven by each hydraulic station is equal, thereby improving the utilization rate of the hydraulic pump station.

[0032] Based on the lifting force, distance, and number of hydraulic cylinders, a method of controlling multiple cylinders with multiple pump stations was set up. Each pump station simultaneously drives multiple cylinders to work. Finally, all pump stations and cylinders are centrally controlled by a computer, and all cylinders work synchronously at the same time, so that all lifting points of the lifting truss are lifted synchronously, ensuring the stability of the entire lifting process and the structural safety.

[0033] According to a preferred embodiment, in steps 3.2 and 3.3, two welded balls at the main truss segment are selected as the lower suspension points at both ends of the main truss; a lifting lower anchor point is set at the upper chord node of the radial truss, and two diagonal tie rods are set on the side of the lifting point position of the lifting lower anchor point to avoid changing the structural force system by replacing the members.

[0034] According to a preferred embodiment, in steps 3.2 and 3.3, synchronous monitoring is performed during the lifting process, and the roof is adjusted when the height difference exceeds a preset value. Preferably, the preset height difference is 20mm.

[0035] Meanwhile, a measuring point was set at each lifting point to continuously monitor the smooth and synchronous lifting of the entire truss, control the precise spatial coordinates of the interface, and ensure the accurate spatial position of the truss.

[0036] According to a preferred embodiment, in step 3.3, after the lifting and alignment, the main structure or temporary support structure is used to replace the hydraulic equipment in bearing the force. Specifically, the crossbeam at the positioning position is placed next to the positioning position in advance. After the lifting to the positioning position, the crossbeam is immediately installed in the designated position, and then the crossbeam is used to support the force.

[0037] According to a preferred embodiment, in step 3.5, the temporary support is unloaded using a phased synchronous proportional unloading method: the maximum deflection value at the mid-span of the inner ring truss is calculated, and the unloading is graded according to the maximum deflection value, with each unloading stage producing a deformation of no more than 20mm, wherein the first unloading stage does not exceed 15mm.

[0038] By controlling the relative displacement difference during unloading, the unloading of the entire roof is equivalent to synchronous unloading, keeping the entire roof structure in a essentially static unloading state. This unloading method is suitable for projects with many unloading control points and small unloading displacements. The advantages of this method are improved unloading safety and reduced unloading costs.

[0039] According to a preferred embodiment, in step 3.5, during unloading, the cantilever portion is unloaded from the outside to the inside, and the main span of the truss is unloaded from the inside to the outside, proceeding synchronously in the circumferential direction. Furthermore, the cantilever portion and the main span of the truss are unloaded cyclically according to stress changes, and the unloading is carried out proportionally.

[0040] This setup prevents excessive unloading and large elevation differences, completing the transformation of the force system of the spatial truss structure and achieving safe and stable unloading of the entire roof. During unloading, the support adjustment plates are pre-cut proportionally to control the unloading error within 20mm, preventing excessive unloading and successfully completing the transformation of the force system of the members at the support points of the spatial truss, thus achieving safe and stable unloading of the entire roof.

[0041] Compared with existing technologies, the advantages of this invention are:

[0042] 1. A construction method for a space truss with a prestressed structure, which calculates the stress and displacement of the structure under different construction conditions in different construction stages to tension the prestress in steps, grades, and sequences, thereby avoiding the impact of applying prestress once on the original structure and improving the safety of the construction process.

[0043] 2. A construction method for a space truss with a prestressed structure, which achieves the overall synchronous lifting of the space truss structure by rationally designing the lifting points and setting hydraulic jacks. By improving the structure of the lifting points, it is possible to directly align and close the structure after lifting without the need for replacing the rods, thereby improving the convenience of the construction process and avoiding the risk of truss instability during the closure process after lifting.

[0044] 3. A construction method for a space truss containing a prestressed structure, which adopts a phased synchronous proportional unloading method to control the height difference of a single unloading. Based on reasonable calculations and a single-point cyclic unloading method, synchronous unloading is achieved, which can ensure the stability of the truss during the unloading of the temporary support structure and improve the safety of the construction process. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the steel strand threading sequence in Embodiment 1 of this application;

[0046] Figure 2 This is a schematic diagram of the tensioning sequence of each group of steel strands in Embodiment 1 of this application;

[0047] Figure 3 This is a schematic diagram of the lifting point setting in Embodiment 2 of this application;

[0048] Figure 4 This is a schematic diagram of the lifting hydraulic jack configuration in Embodiment 2 of this application;

[0049] Figure 5 This is a schematic diagram of the unloading of the cutting adjustment plate in Embodiment 2 of this application. Detailed Implementation

[0050] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0051] Example 1

[0052] A construction method for a space truss containing a prestressed structure includes the following steps:

[0053] Step 1: Design the suspension points by modeling using structural software;

[0054] Step 2: Based on the lifting points and using structural software, determine the prestressing tensioning method (number of tensioning stages and magnitude of prestress in each stage);

[0055] Step 3: Conduct actual construction based on the lifting points and prestressing tensioning method.

[0056] In step 3, prestressing is simultaneously performed according to the prestressing tensioning method determined in step 2, including graded prestressing, step-by-step prestressing, and sequential prestressing.

[0057] Preferably, in step 1, the suspension points are set mainly based on the parts with large deflection or large stress during simulation calculations, which is a conventional technical method in this field.

[0058] Preferably, the basis for determining the prestressing tensioning method in step 2 is that both the maximum displacement and stress meet the specifications, and the maximum displacement and stress should be relatively small. Specifically, the comprehensive stress (tension, compression, bending, shear, torsion) ratio of the structure is calculated using Midas structural software to ensure that it does not exceed 0.8 and the displacement does not exceed 1 / 250, so as to minimize the impact of prestressing tensioning on the original structure. Preferably, when simulating prestressing tensioning, the number of tensioning stages and the tension force at each stage are determined by calculating whether the comprehensive stress and displacement of the main truss in each sub-step of step 3 meet the requirements, using a reference value that is consistent with the maximum camber value during truss assembly and the deflection value under self-weight.

[0059] Existing single-tension prestressing construction methods, when used, are prone to two problems because the prestressing tension is the design value under normal roof structure conditions. This is because the roof load may not be fully applied during prestressing construction: 1) When the prestressing acts as an unloading effect, incomplete unloading may occur; 2) When the prestressing acts as a load-increasing effect, excessive load may occur. To avoid these two problems, this application determines the appropriate prestressing magnitude and tensioning method based on the different structural stages of construction. By applying different magnitudes of prestressing at different construction stages, the impact of prestressing applied at different stages on the structure is reduced.

[0060] According to a preferred embodiment, step 3 further includes the following sub-steps:

[0061] Step 3.1: Construct the main truss and assemble the jig;

[0062] Step 3.2: Try to improve;

[0063] Step 3.3: After lifting and positioning, align the main truss.

[0064] Step 3.4: Proceed to the second stage of installation;

[0065] Step 3.5: After the second section is installed, unload the temporary support bracket.

[0066] In steps 3.1-3.5, prestressing is simultaneously performed according to the prestressing tensioning method determined in step 2, including graded prestressing, step-by-step prestressing, and sequential prestressing. "Synchronized" means that step-by-step tensioning is performed during each graded tensioning stage, and sequential tensioning is performed within each step-by-step tensioning stage.

[0067] According to a preferred embodiment, the prestressed tensioning is performed in stages, including: a first stage of prestressing during the cable threading process to prevent interference between groups of steel strands; a second stage of prestressing the truss on the assembly jig, with the tension value determined based on computer simulation of structural stress; a third stage of tensioning after lifting; and finally, after lifting and bringing the structure to rest, further tensioning in stages to the final design value. This method, through computer model simulation calculations, determines the optimal and safest tension value, ensuring structural safety and quality, and meeting design requirements. The final 5% over-tensioning addresses stress loss in the steel strands, satisfying the structural prestressing requirements.

[0068] The prestressing step-by-step tensioning includes: tensioning the prestress to a predetermined value in multiple steps according to a certain prestressing change gradient;

[0069] The prestressed sequential tensioning includes: such as Figure 1 As shown, the prestressed steel strands are threaded in a top-to-bottom, right-to-left order; as... Figure 2As shown, the steel strands in opposite directions are tensioned sequentially from bottom to top. Multiple sets of steel strands need to be threaded through the steel pipe, and the strands are quite long. After the ends of the steel strands are tightened, there will be a natural downward sag in the middle. This threading sequence prevents the later-threaded steel strands from interfering with the earlier ones, ensuring that the sets are not confused.

[0070] Because the roof's self-weight is borne by temporary supports before lifting, and the lower chord of the steel pipe is not under tension, the prestressing tension cannot counteract the tension on the lower chord. Instead, it can easily lead to excessive stress at the prestressing tensioning location. To minimize the impact of prestressing tensioning on the original structure, simulation calculations at each stage are needed. Adopting a step-by-step, graded, and sequential tensioning method can yield more favorable prestressing tensioning steps and matching tensioning force values, thus reducing the impact on the original structure.

[0071] Since the roof's self-weight was borne by temporary supports before lifting, and the lower chord of the steel pipe was not under tension, the prestressing tension could not offset the tension on the lower chord. Instead, it could easily lead to excessive stress at the prestressing tensioning location. Therefore, prestressing tensioning before lifting requires calculation to avoid excessive tension stress damaging the original structure. This application, through simulation calculations at each stage, demonstrates that prestressing tensioning is performed step-by-step before and after the structure bears its own weight. This step-by-step, graded, and sequential tensioning method yields more favorable prestressing tensioning steps and matching tensioning force values, reducing the impact of prestressing tensioning on the original structure and ensuring minimal impact.

[0072] Preferably, in step 3.3, after lifting and alignment, the main structure or temporary support structure replaces the hydraulic equipment in bearing the load. Specifically, the crossbeam at the alignment position is pre-placed next to the alignment position. After lifting to the alignment position, the crossbeam is immediately installed in the designated position, and then the crossbeam is used for support. Existing construction methods still rely on the hydraulic equipment for load bearing after lifting to the position, gradually transferring the load to the main structure or temporary support structure only after the main structure is connected. Since the connection time after lifting to the position is excessively long (more than one month), this application transfers the load of the hydraulic jacks to a reliable temporary support structure to ensure structural safety, thus increasing the construction safety factor.

[0073] Preferably, a hemispherical component is provided at the wall attachment position of the lifting support frame to avoid mutual interference and overlap of the members. Since there are many support members and their cross-sections are relatively large (steel pipe diameter approximately Ф299x10), the addition of the hemispherical component ensures that each support can effectively transmit force after connecting to the wall.

[0074] Preferably, in step 3.2, the crane is configured according to the lifting points designed in step 1 as follows:

[0075] (1) While meeting the load requirements of the lifting point, try to make the load on each lifting device as similar as possible; use built-in sensors to feed back the hydraulic reaction force and then adjust and control it.

[0076] (2) Try to ensure that the number of hydraulic devices driven by each hydraulic station is equal, so as to improve the utilization rate of the hydraulic pump station.

[0077] Based on the lifting force, distance, and number of hydraulic cylinders, a multi-pump station control method was implemented, with each pump station simultaneously driving multiple cylinders. Finally, all pump stations and cylinders are centrally controlled by a computer, ensuring synchronized operation of all lifting points of the truss. This guarantees the smoothness and structural safety of the entire lifting process. Simultaneously, measuring points were set at each lifting point to continuously monitor the smooth and synchronized lifting of the entire truss, controlling the precise spatial coordinates of the interfaces and ensuring the accurate spatial positioning of the truss.

[0078] In step 3.3, after the truss structure is lifted into place, it usually involves replacing the members. Replacing the members changes the force system during the lifting process. Members that were originally under tension are prone to change to compression members during the replacement process. Since the compressive stability of steel structures is lower than that under tension, accidents are more likely to occur.

[0079] This application features structural improvements to the lifting points. In steps 3.2 and 3.3, two welded spheres at the main truss segment are selected as the lower lifting points at both ends of the main truss. Lower lifting anchor points are installed at the upper chord nodes of the radial truss, connected to the lifting steel strands via ground anchors. The radial truss lower lifting anchor points are located in the middle of two annular trusses. To ensure the stability of the lifting position, two diagonal tie rods are installed on the side of the lower lifting anchor points to prevent changes in the structural force system from being altered by replacing members. Through the aforementioned lower lifting points and lower lifting anchor points, the work of replacing members after lifting and positioning is effectively avoided; that is, lifting and positioning only reinforces the lifting unit, eliminating the risk of instability.

[0080] Preferably, in steps 3.2 and 3.3, synchronous monitoring is performed during the lifting process, and the roof is adjusted when the roof height difference exceeds a preset value. Preferably, the relative height difference adjustment value is 20mm, that is, the roof is adjusted when the relative height difference between any two points exceeds 20mm.

[0081] Preferably, the synchronous detection method can be as follows: hydraulic cylinder stroke accumulation recording: the hydraulic cylinder stroke is 250mm each time, the stroke of each lifting is accumulated and summed, and the roof is synchronously adjusted by the sum of the strokes of each lifting device.

[0082] Preferably, the synchronous detection method can also be used for: total station spatial positioning monitoring:

[0083] After pre-applying reflective patches, the positions of each lifting joint are checked using a total station. Before lifting through the roof structure, the theoretical positioning coordinates of each pipe opening at each connecting steel pipe opening are checked and adjusted.

[0084] Reflective patches are installed at the upper chord pipe openings of all main trusses requiring alignment. A flat iron is pre-welded along any diameter of the pipe opening, with its outer surface flush with the pipe opening. The center point of the steel pipe is then located on the reflective patch, which is then attached to it. Preferably, the flat iron is 6mm in size.

[0085] Preferably, the synchronous detection method can also include: level instrument travel monitoring: considering that the monitoring points of the total station may be obstructed by buildings during the lifting process, the travel of the level instrument is measured. A graduated scale is suspended at the lower chord of each main truss, and the basic data of each point is recorded. After every four travels, the travel of each point is recorded and compared using the level instrument. If the height difference exceeds 20mm, the roof is adjusted. Preferably, the scale can be an inverted 50m measuring tape.

[0086] By continuously measuring and monitoring the smooth and synchronous lifting of the entire truss, and controlling the precise spatial coordinates of the interfaces, the accurate spatial position of the truss is ensured.

[0087] Preferably, in step 3.5, after installation, the temporary support is unloaded as a whole using a "phased synchronous proportional unloading" method. Through simulation and comparative calculations of the schemes, the maximum deflection value at mid-span of the inner ring truss is calculated. Based on the maximum deflection value, the unloading is graded with a limit of no more than 20mm of deformation per stage, with the first stage unloading not exceeding 15mm.

[0088] By controlling the relative displacement difference during unloading, the unloading of the entire roof is equivalent to synchronous unloading, keeping the entire roof structure in a essentially static unloading state. This unloading method is suitable for projects with many unloading control points and small unloading displacements. The advantages of this method are improved unloading safety and reduced unloading costs.

[0089] Preferably, the unloading of the outer ring truss is carried out by selecting two sets of jigs (each set with one unloading point) at each end of the central axis and unloading them synchronously and symmetrically in two zones.

[0090] In step 3.5, during installation, the adjusting plate is set to a value greater than the deflection calculated in the roof truss simulation. During unloading, only the adjusting plate needs to be cut to lower the jacks. The adjusting plate is set as follows: Figure 5 As shown.

[0091] During construction, the cantilever section is carried out from the outside to the inside, and the main span of the truss is carried out from the inside to the outside, in a circumferential and synchronous manner. The cantilever and the main span are carried out cyclically according to stress changes. Unloading is carried out proportionally to prevent excessive unloading or large height differences. This completes the transformation of the force system of the spatial truss structure and achieves safe and stable unloading of the entire roof.

[0092] During unloading, the fulcrum adjustment plate was pre-cut proportionally to keep the unloading error within 20mm, preventing over-unloading and successfully completing the force system conversion of the members at the fulcrum position of the spatial three-dimensional truss, thus achieving safe and stable unloading of the entire roof.

[0093] By controlling the relative displacement difference during unloading, the unloading of the entire roof is equivalent to synchronous unloading, keeping the entire roof structure in a essentially static unloading state. This unloading method is suitable for projects with many unloading control points and small unloading displacements. The advantages of this method are improved unloading safety and reduced unloading costs.

[0094] Example 2

[0095] Taking the Chengdu Grand Cube project as an example, its roof is a spatial steel pipe truss structure with a near-circular "scallop" shape in plan, 146.9m in diameter and 4.5m in height, resting on 12 fixed and 22 sliding supports. Above the stage opening is an 8m×8m "fish belly beam" truss, with 1178t of prestressed steel strands tensioned inside the lower chord steel pipes of the main truss, totaling over 3000 tons. After the completion of this structure, the entire roof truss is supported by 92 support points.

[0096] Lifting point design: Based on the study of this structure, which has a large span, small member cross-sections, and high flexibility in the lifting components, 14 lifting points were calculated and set up for synchronous lifting to ensure that the deflection during the lifting process does not exceed the allowable deviation specified in the code. The arrangement of the lifting points was mainly based on the locations with large deflection or high stress during simulation calculations. The lifting point reactions are shown in Table 1.

[0097] Table 1

[0098]

[0099] Based on the lifting point and reaction force, the hydraulic jack configuration is as follows: Figure 4 As shown.

[0100] (1) The main truss has 4 lifting points, with 2 lifting cylinders configured at the lifting point with the greatest force, for a total of 6 lifting cylinders. The radial trusses have 14 sections with 10 lifting cylinders, for a total of 5 pump stations. The maximum lifting cylinder capacity is 200t, and the minimum is 60t.

[0101] (2) The lifting cylinder stroke is uniformly set at 250mm, and the lifting is synchronized through unified computer control. Conventional measurement methods are used to correct the cumulative error that occurs during lifting.

[0102] The area of ​​the steel roof to be lifted consists of three main trusses (TR19, TR20, and TR21) and the radial trusses connected to them (between axes Ab and Ac). Based on the structural characteristics of the steel roof and the lifting process, a total of 14 lifting points are arranged. Specifically, one lifting point is set between TR19 and TR20, and between TR20 and TR21, for a total of four lifting points; one lifting point is set at each of the upper chord nodes of the radial trusses, for a total of ten lifting points. The lifting point arrangement is as follows: Figure 3 As shown.

[0103] A computer model was established to simulate the prestressing tension. The prestress and displacement under various working conditions are shown in Table 2.

[0104] Table 2

[0105]

[0106] The calculations concluded that prestressing should be tensioned in two stages, specifically in three steps: first, tensioning to 50% on the assembled jig; second, a trial lift; and third, tensioning to 100% during the trial lift. The maximum displacement and stress in these three steps all meet the specifications, and both are relatively small.

[0107] To minimize the impact of prestressing tensioning on the original structure, simulation calculations at each stage were used to derive the most favorable prestressing tensioning steps and matching tension force values. The grading method was based on 10% σcon, 30% σcon, 50% σcon, 80% σcon, and 100% σcon.

[0108] Phase 1: The roof is tensioned in a free state on the support frame, from 0-10%σcon to 30%σcon and then to 50%σcon.

[0109] The second stage: When the roof is tensioned to 50% σcon, a trial lift is carried out, that is, the roof is observed when it has borne its own weight load.

[0110] The third stage: After the roof bears its own load, the prestressing tensioning construction is completed in stages according to 50%σcon-80%σcon-100%σcon.

[0111] After construction is completed, phased synchronous and proportional unloading will be carried out to control the structural system's smooth and safe transition. Through simulation and comparative calculations of this scheme, the unloading scheme for the structure will be finally determined. According to the design model, the maximum deflection at mid-span of the inner ring truss is 80mm. Based on this value, with the deformation caused by each unloading stage not exceeding 20mm, the entire unloading process can be divided into 3 stages, with each stage involving a step-by-step (graded) reduction, and the first stage unloading not exceeding 15mm.

[0112] The unloading process is divided into four steps, with displacement amounts of 20%, 50%, 80%, and 100% respectively. The control of the displacement amounts meets the design requirements.

[0113] The entire roof is mainly unloading the inner truss, which means that the 10 stress areas generated by the 10 sets of temporary supports in the inner ring are slowly and steadily unloaded by selecting 10 unloading points of the 10 sets of support frames, so that the main truss structure changes from being supported by external forces to being completely supported by its own structure.

[0114] Since the outer ring truss has 16 truss support frames, based on the structural characteristics of the outer ring truss, it is only necessary to select 2 sets of support frames (each set with 1 unloading point) at each end of the central axis to unload synchronously and symmetrically in two zones.

[0115] During unloading, the adjusting plate is primarily cut with a cutter, following the unloading sequence and the amount of material cut each time. Before cutting, a 32T jack is used for support. According to lifting simulation calculations, the maximum support reaction force at the lifting node is approximately 24T, the maximum weight at the first support point of the second support frame is 4T, and the simulated maximum force for supports 1 and 2 is 28T. Supported by two points, each support point has an average maximum force of 14T. After proper support, the cutter is used for cutting. After cutting, the jacks are gradually released.

[0116] During unloading, the deformation of adjacent supports must be observed simultaneously to ensure safety during the unloading process. When a major step of unloading is completed, a half-hour pause should be taken for observation. If no abnormalities are found, the next step can be carried out.

[0117] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

[0118] This background section is provided to generally present the context of the invention. The work of the currently named inventors, the work to the extent described in this background section, and aspects of this section that did not constitute prior art at the time of application are neither expressly nor impliedly acknowledged as prior art to the invention.

Claims

1. A construction method for a space truss containing a prestressed structure, characterized in that, Includes the following steps: Step 1: Design the suspension points by modeling using structural software; Step 2: Based on the lifting points and using structural software, determine the prestressing tensioning method; Step 3: Conduct actual construction based on the lifting points and prestressing tensioning method; Step 3 includes the following sub-steps: Step 3.1: Construct the main truss and assemble the jig; Step 3.2: Try to improve; Step 3.3: After lifting and positioning, align the main truss. Step 3.4: Proceed to the second stage of installation; Step 3.5: After the second section is installed, remove the temporary support bracket. In steps 3.1-3.5, prestressing is simultaneously performed according to the prestressing tensioning method determined in step 2, including graded prestressing, step-by-step prestressing, and sequential prestressing. The prestressed graded tensioning includes: the first stage is prestressing in stages during the threading of steel cables; the second stage is prestressing tensioning of the truss on the assembly jig; and the third stage is tensioning after lifting. The prestressing step-by-step tensioning includes: tensioning the prestress to a predetermined value in multiple steps according to a certain prestressing change gradient; The prestressed sequential tensioning includes: threading the prestressed steel strands in a top-to-bottom and right-to-left order; and tensioning the steel strands located in opposite directions in a bottom-to-top order. The unloading temporary support in step 3.5 includes: When unloading the temporary support for the cantilever section, unload from the outside in. When unloading the temporary support bearings in the main span of the truss, unloading should be carried out from the inside out, and the circumferential process should be synchronized. The unloading of temporary supports for the cantilever section and the unloading of temporary supports within the main span of the truss are carried out cyclically according to stress changes.

2. The construction method for a space truss with a prestressed structure according to claim 1, characterized in that, The suspension points are set according to the deflection value or the location of the force.

3. The construction method for a space truss with a prestressed structure according to claim 1, characterized in that, Step 2 includes: determining the optimal prestressing tensioning method by setting model parameters based on the lifting points and using structural software; The model parameters include: the overall stress ratio of the original structure does not exceed 0.8, and the displacement does not exceed 1 / 250.

4. The construction method for a space truss with a prestressed structure according to claim 1, characterized in that, In step 3.5, the temporary support is unloaded using a phased synchronous proportional unloading method: the maximum deflection value at the mid-span of the inner ring truss is calculated, and unloading is carried out in stages according to the maximum deflection value, with the deformation generated by each unloading stage not exceeding 20mm, and the first unloading stage not exceeding 15mm.

5. The construction method for a space truss with a prestressed structure according to claim 1, characterized in that, In steps 3.2 and 3.3, two welded balls at the main truss segment are selected as the lower suspension points at both ends of the main truss; a lifting lower anchor point is set at the upper chord node of the radial truss, and two diagonal tie rods are set on the side of the lifting point of the lifting lower anchor point to avoid changing the structural force system by replacing the members.

6. The construction method for a space truss with a prestressed structure according to claim 1, characterized in that, In steps 3.2 and 3.3, synchronous monitoring is performed during the lifting process, and the roof is adjusted when the roof height difference exceeds the preset value.

7. The construction method for a space truss with a prestressed structure according to claim 1, characterized in that, In step 3.3, after the lifting and alignment, the main structure or temporary support structure is used to replace the hydraulic equipment in bearing the force. The specific method is as follows: the crossbeam at the positioning position is placed next to the positioning position in advance. After the lifting to the positioning position, the crossbeam is immediately installed in the designated position, and then the crossbeam is used to support the force.

Images