Rotary disc buckle type space truss structure and stress detection method

Abstract

The invention relates to the technical field of constructional engineering, in particular to a rotating disc buckle type space truss structure and a stress detection method. According to the rotating disc buckle type space truss structure and the stress detection method, the plurality of spherical node connecting pieces are combined to form a space structure, the spherical node connecting pieces are connected through the connecting pipes and are connected by adopting the rotating disc buckle structures, and the mounting and the dismounting are very convenient. And during use, the positioning bayonet lock can be used for fixing to prevent the rotating disc buckle from being opened. The end sealing plates are welded to the ends of the branch pipes and the ends of the connecting pipes, during assembly, the end sealing plates are in butt joint and sleeved with the external rotating disc buckles, the end sealing plates are rotated by 45 degrees in any direction in the plane perpendicular to the axis of the connecting pipes, then the clamping jaws of the end sealing plates are clamped into the rotating disc buckles, joints can be fixed, and high-strength connection is formed. The branch pipes extend towards the periphery through the connecting pipes to be connected with other spherical nodes, diversified large space truss structures can be combined at will, and the large space truss structure has the advantages of being high in construction efficiency and low in comprehensive cost.

Description

Technical Field

[0001] The present invention relates to the technical field of construction engineering, and in particular to a rotating disk-locking type space grid structure and a stress detection method thereof. Background Art

[0002] At present, large-scale industrial storage buildings are gradually transitioning from small-diameter silos to large-diameter and large-span silo forms, and the construction of the silo roof structure has also changed from a vertical vertical support system to a spatial horizontal structure support system, increasing the construction difficulty. During the construction of these large-diameter storage buildings, there is often a disconnection between construction technology and structural design, mainly reflected in the construction of the silo roof structure. Due to the characteristics of high suspension, large self-weight, large span and large area of the concrete silo roof, the calculation and design of the construction support system for the silo roof structure have become the difficulties and key points in the silo roof construction, and at the same time, the defects of traditional vertical support systems such as full hall scaffolding, central steel support grids and radial beam drum platforms have been highlighted, such as large installation and disassembly workload, low construction efficiency, high comprehensive cost, etc. Therefore, under the condition of ensuring safety and economy, higher requirements are also placed on the construction technology level, construction process and construction equipment. Starting from the actual engineering needs, it is also necessary to develop a more safe, efficient, large-bearing capacity and convenient disassembly and assembly temporary grid support system to complete the construction of ultra-large-diameter storage buildings and large-span empty buildings. Summary of the Invention

[0003] Aiming at the defects in the prior art, the present invention provides a rotating disk-locking type space grid structure and a stress detection method thereof.

[0004] One of the technical solutions adopted by the present invention is: a rotating disk-locking type space grid structure, including a plurality of spherical node connectors and connecting pipes connected between the spherical node connectors. The spherical node connectors include hollow spheres, and branch pipes are provided in the directly above, directly below, directly left, directly right, directly front and directly rear directions of the hollow spheres, and the branch pipes are connected to the connecting pipes through a rotating disk-locking structure.

[0005] To better implement the present invention, end sealing plates are provided at the ends of the branch pipes and the connecting pipes, and claws are provided on the circumferences of the end sealing plates, and two claws are connected together through a rotating disk-locking connection.

[0006] To better implement the present invention, notches for the claws to be inserted into and stoppers for locking the claws are provided on the rotating disk-locking.

[0007] To better implement the present invention, a positioning pin adapted to the notch is further included. When the rotation of the claw is blocked by the stopper, the positioning pin is used to insert into the notch to prevent the claw from disengaging from the stopper.

[0008] To better implement the present invention, a gripping rib for convenient gripping is provided at one end of the positioning dowel pin, and a ratchet pawl for preventing backward movement is provided at the other end.

[0009] To better implement the present invention, a through hole for preventing it from cracking is provided on the positioning dowel pin.

[0010] One of the technical solutions adopted by the present invention is: a method for detecting the force-bearing performance of a rotary button-type space grid structure, including

[0011] Testing the axial tensile performance and axial compressive performance of the connecting pipe, observing the failure phenomenon of the axial test of the connecting pipe, synthesizing the displacement and strain data of the members, plotting the load-displacement and stress-strain curves, analyzing the bearing capacity, deformation performance and stress distribution of the connecting pipe, and exploring the influence law of the member length and material on its bearing capacity;

[0012] Conducting unidirectional tensile and pressure tests on the hollow sphere, analyzing the bearing capacity, failure characteristics and spherical stress distribution of the hollow sphere joint; combining the displacement and strain data, plotting the relationship curves of load with displacement and strain, and performing force analysis on the surface of the spherical joint, the heat-affected zone of the weld and the welded short rod;

[0013] Conducting a vertical loading test on the grid structure to test its bearing capacity; plotting the corresponding load-displacement curve and the load-strain curve of the members according to the test results, and analyzing the structural deformation characteristics and the stress distribution of the connecting pipe;

[0014] Based on the ANSYS software, establishing a corresponding finite element model, loading and solving, and comparing and analyzing with the above test results to obtain the factors and laws affecting the bearing capacity performance of the grid, and providing an application basis and theoretical foundation for the application of the rotary button-type grid.

[0015] To better implement the present invention, when conducting a unidirectional tensile test on the hollow sphere, an eight-hole flange is placed on one side of the hollow sphere, the end anchor of the steel wire rope is passed through the hole of the eight-hole flange, and the bolt is tightened externally; pulling the steel wire rope can transfer the tension of the eight-hole flange to the hollow sphere to achieve the unidirectional tensile test of the hollow sphere.

[0016] To better implement the present invention, when conducting a vertical loading test on the grid structure, a structural static loading system is adopted, and the monotonic continuous grading loading is carried out by the loading method. Two counterweights are loaded at each level and symmetrically placed. After reaching the load level, hold the load for 5 minutes and monitor the deformation of the grid.

[0017] To better implement the present invention, a segmented distribution beam needs to be set at the bottom before placing the counterweight block to prevent uneven distribution of the top load caused by excessive settlement in the middle of the grid during the test; below the longitudinal distribution beam is the transverse distribution beam, which is cut from a channel steel and spans two spherical joints at the end of the upper chord of the grid, serving as the fulcrum of the longitudinal distribution beam and being inverted on the uppermost vertical connecting pipe. Several angle steels are spot-welded both above and below the transverse distribution beam as anchoring joints to prevent slipping.

[0018] The beneficial effects of the present invention are as follows: The rotary socket-connected space grid structure and the stress detection method of the present invention, through the cooperation of connecting pipes, hollow balls, branch pipes and rotary socket structures, etc., several spherical joint connectors form a space structure through combination. The spherical joint connectors are connected through each connecting pipe and are connected by a rotary socket structure, and the installation and disassembly are quite convenient. When in use, it can also be fixed by using positioning pins to prevent the rotary socket from opening. End sealing plates are welded at the ends of the branch pipes and connecting pipes. During assembly, the end sealing plates are butted and the external rotary socket is sleeved, and rotating 45° in any direction in the plane perpendicular to the axis of the connecting pipe can make the claws of the end sealing plate snap into the rotary socket, which can fix the joints and form a connection with high strength. The branch pipes of the spherical joint connectors extend around through the connecting pipes to connect other spherical joint connectors, and a large-scale space grid structure with modularization and diverse forms can be formed through arbitrary combination, which has the advantages of high construction efficiency and low comprehensive cost. Description of the Drawings

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts do not necessarily draw according to the actual ratio.

[0020] Figure 1 It is a schematic structural diagram of a rotary socket-connected space grid structure of the present invention;

[0021] Figure 2 It is a schematic structural diagram of a spherical joint connector of a rotary socket-connected space grid structure of the present invention;

[0022] Figure 3 It is a schematic structural diagram of a rotary socket of a rotary socket-connected space grid structure of the present invention;

[0023] Figure 4 It is a schematic structural diagram of a positioning pin of a rotary socket-connected space grid structure of the present invention;

[0024] Figure 5 It is a schematic structural diagram of a stress detection method of a rotary socket-connected space grid structure of the present invention;

[0025] Figure 6 It is a schematic structural diagram of WJ-1 of the force detection method for the rotating socket button type space grid structure of the present invention;

[0026] Figure 7 It is a schematic structural diagram of WJ-2 of the force detection method for the rotating socket button type space grid structure of the present invention;

[0027] Figure 8 It is a schematic structural diagram of WJ-3 of the force detection method for the rotating socket button type space grid structure of the present invention;

[0028] Figure 9 It is a schematic structural diagram of the test number of the force detection method for the rotating socket button type space grid structure of the present invention;

[0029] Figure 10 It is a schematic structural diagram of the test number of the force detection method for the rotating socket button type space grid structure of the present invention;

[0030] Figure 11 It is a schematic structural diagram of the test number of the force detection method for the rotating socket button type space grid structure of the present invention;

[0031] Figure 12 It is a schematic structural diagram of the test number of the force detection method for the rotating socket button type space grid structure of the present invention;

[0032] Figure 13 It is a schematic structural diagram of the test number of the force detection method for the rotating socket button type space grid structure of the present invention;

[0033] In the drawings, 1 - hollow ball, 2 - branch pipe, 3 - end sealing plate, 4 - claw, 5 - connecting pipe, 6 - rotating socket button, 7 - positioning pin, 8 - through hole, 9 - notch, 10 - stop block, 11 - rib, 12 - ratchet pawl. Detailed implementation manners

[0034] Hereinafter, embodiments of the technical solution of the present invention will be described in detail with reference to the drawings. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and thus are only examples and should not be used to limit the protection scope of the present invention.

[0035] To make the purposes, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are some, but not all, of the embodiments of the present disclosure. Usually, the components of the embodiments of the present disclosure described and illustrated herein can be arranged and designed in various different configurations.

[0036] In the description of the present disclosure, it should be noted that the orientation or positional relationship indicated by terms such as "upper" and "inner" is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the disclosed product is usually placed during use. It is only for the convenience of describing the present disclosure and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present disclosure. In addition, terms such as "first" and "second" are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0037] In the description of the present disclosure, it should also be noted that unless otherwise clearly specified and defined, the terms "arranged" and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0038] It should be noted that unless otherwise stated, the technical terms or scientific terms used in this application should have the ordinary meanings understood by those skilled in the art to which the present invention pertains.

[0039] Embodiment:

[0040] As Figures 1 to 4 shown, the rotary socket-connected space grid structure of the present invention includes a plurality of spherical node connectors and connecting pipes 5 connected between the spherical node connectors. The spherical node connectors include hollow spheres 1. Branch pipes 2 are arranged in the directly upper, directly lower, directly left, directly right, directly front, and directly rear directions of the hollow sphere 1. The branch pipes 2 are connected to the connecting pipes 5 through a rotary socket structure. The rotary socket-connected space grid structure and the stress detection method of the present invention, through the cooperation of the connecting pipes 5, hollow spheres 1, branch pipes 2, and the rotary socket structure, a number of spherical node connectors are combined to form a space structure. The spherical node connectors are connected through each connecting pipe and are connected by a rotary socket structure, and the installation and disassembly are quite convenient. The branch pipes 2 of the spherical node connectors extend around through the connecting pipes 5 to connect other spherical node connectors, and a large-scale space grid structure with modularization and diverse forms can be formed through arbitrary combination, which has the advantages of high construction efficiency and low comprehensive cost.

[0041] As a preferred embodiment, an end sealing plate 3 is provided at the end of the branch pipe 2 and the end of the connecting pipe 5, and a clamping claw 4 is provided on the circumference of the end sealing plate 3, and the two clamping claws 4 are connected together by a rotating disc buckle 6. The end of the branch pipe 2 and the connecting pipe 5 are welded with the end sealing plate 3. When assembling, the end sealing plate 3 is butted and covered with an external rotating disc buckle 6. The clamping claw 4 is clamped into the rotating disc buckle 6 by rotating 45° in any direction in a plane perpendicular to the axis of the connecting pipe 5, which can fix the node and form a connection with higher strength.

[0042] As a preferred embodiment, the rotating disc buckle 6 is provided with a notch 9 for the claw 4 to be inserted into and a stopper 10 for locking the claw 4. When assembling, the end sealing plate 3 is butted and the external rotating disc buckle 6 is put on. After the claw 4 enters from the notch, it rotates 45° in any direction in a plane perpendicular to the axis of the connecting pipe 5, so that the claw 4 is inserted into the rotating disc buckle 6 and is stopped by the stopper 10 to limit the position, so that the node can be fixed to form a connection with higher strength.

[0043] As a preferred embodiment, a positioning pin 7 adapted to the notch 9 is also included. When the claw 4 rotates and is blocked by the block 10, the positioning pin 7 is used to insert into the notch 9 to prevent the claw 4 from escaping from the block 10. With this design, when the claw 4 is rotated from the notch 9 into the block 10, the positioning pin 7 can be inserted into the notch 9 to fix it, preventing the claw 4 from exiting the block 10 and rotating the disc buckle 6 to open.

[0044] As a preferred embodiment, a gripping convex strip 11 for easy gripping is provided at one end of the positioning pin 7, and a ratchet 12 for preventing back-moving is provided at the other end. With this design, the user can grip the convex strip 11 to insert and remove the positioning pin 7. When the positioning pin 7 is inserted into the notch 9 and passes through the rotating disc buckle 6, the ratchet 12 pops up to prevent back-moving, and works together with the convex strip 11, and is located on both sides of the rotating disc buckle 6 to play a limiting role, so that the entire positioning pin 7 will not be easily disengaged, thereby improving stability and safety.

[0045] As a preferred embodiment, a through hole 8 is provided on the positioning pin 7 to prevent it from cracking. The design of the through hole 8 can not only prevent the positioning pin 7 from cracking due to force, but also save materials.

[0046] A method for detecting the force of a rotating disk-type space grid structure, including:

[0047] The axial tensile performance and axial compressive performance tests were carried out on the connecting pipe 5, and the axial test failure phenomenon of the connecting pipe 5 was observed. The displacement and strain data of the rod were integrated to draw the load-displacement and stress-strain curves, analyze the bearing capacity, deformation performance and stress distribution of the connecting pipe 5, and explore the influence of the length and material of the rod on its bearing capacity;

[0048] Perform unidirectional tensile and compressive tests on the hollow sphere 1 to analyze the bearing capacity, failure characteristics, and spherical stress distribution of the joints of the hollow sphere 1; combine displacement and strain data to plot the relationship curves of load versus displacement and strain, and conduct stress analysis on the surface of the spherical joint, the heat-affected zone of the weld, and the welding short rod.

[0049] Perform a vertical load test on the grid structure, as Figure 5 shown, to test its bearing capacity; draw the corresponding load-displacement curve and the load-strain curve of the members according to the test results, and analyze the structural deformation characteristics and the stress distribution of the connecting pipe 5.

[0050] Based on the ANSYS software, establish the corresponding finite element model, perform loading and solution, and compare and analyze with the above test results to obtain the factors and laws affecting the bearing capacity performance of the grid, providing an application basis and theoretical foundation for the application of the rotary socket-connected grid.

[0051] As a preferred implementation, when performing a unidirectional tensile test on the hollow sphere 1, place an eight-hole flange plate on one side of the hollow sphere 1, pass the end anchor of the wire rope through the holes of the eight-hole flange plate, and tighten the bolts externally; pulling the wire rope can transfer the tensile force on the eight-hole flange plate to the hollow sphere 1 to achieve the unidirectional tensile test of the hollow sphere 1.

[0052] As a preferred implementation, when performing a vertical load test on the grid structure, adopt a structural static loading system, use the method of stacking loads for monotonous continuous graded loading, load two counterweights at each level, and place them symmetrically. Hold the load for 5 minutes after reaching the load level, and monitor the deformation of the grid.

[0053] As a preferred implementation, a segmented distribution beam needs to be set at the bottom before placing the counterweight blocks to prevent uneven load distribution at the top due to excessive settlement in the middle of the grid during the test; the longitudinal distribution beam is below the transverse distribution beam. The transverse distribution beam is cut from a channel steel, straddles the two spherical joints at the end of the upper chord of the grid, serves as the fulcrum of the longitudinal distribution beam, and is inverted on the uppermost vertically upward connecting pipe 5. Several angle steels are spot-welded on both the upper and lower sides of the transverse distribution beam as anchoring nodes to prevent slipping.

[0054] Number the three full-scale grid structure specimens as WJ-1, WJ-2, and WJ-3 (single-plane grid), as Figures 6 - 8As shown in the figure, it is placed on a rigid foundation in a simply supported manner. Specimen WJ-1 is the basic grid structure, arranged according to the conventional horizontal support platform in the project; while specimen WJ-2 adopts the same structural form and prestressed cables are tensioned in the middle three steps of its lower chord; on the basis of WJ-2, specimen WJ-3 increases the calculated height of the grid structure, forms a three-layer grid structure by increasing the number of structural layers, and tensiones the prestressed cables in the middle of the lower chord. The longitudinal and transverse node spacings of the structure are both 1.5m. The effective height of specimens WJ-1 and WJ-2 is 1.5m, and the effective height of WJ-3 is 3m.

[0055] The assembly rule of the grid structure is to diverge from the inside to the outside and from the center to the surrounding. First, locate the positions of the spherical nodes on the ground to form square corner nodes with a side length of 1.5m, and place 1100mm bars between the nodes. After realizing the connection from point to line and from line to surface, arrange the vertical bars, diagonal web members and corresponding end spherical nodes upwards, and then assemble the upper chord bars to form the basic cube of the grid structure. Through the organic arrangement of the basic cubes, various grid structures can be assembled according to the engineering needs.

[0056] The prestressed cables are selected as steel wires ropes with a specification of φ19.5mm and 6×19, and the nominal tensile strength is 1770MPa. The minimum breaking force of the steel wire rope is about 210kN, and a safety factor of 3 is taken during use, that is, the allowable force of a single cable does not exceed 70kN. Threaded anchor bolts made of Q355 material are made at the end of the steel wire rope, the diameter of the anchor bolt is 22.5mm, and the outer diameter of the thread is 24mm. Design an eight-hole flange plate. When tensioning the prestressed cables, pass the end anchor bolts of the steel wire ropes through the holes and tighten the bolts outside.

[0057] Vertical loads are applied according to the on-site counterweights. The size of the counterweight is 910mm×3060mm×320mm, and the weight of a single piece is about 20kN. Two counterweights are symmetrically arranged as a single-stage load. Before the test starts, a preload of 20kN is applied to the middle of the grid structure to check whether the test device and instruments are working properly. After debugging the instruments, unload and start the formal test. During the formal loading stage, two counterweights are loaded at each level and placed symmetrically. After reaching the load level, hold the load for 5 minutes to monitor the deformation of the grid structure. When the vertical load of about 200kN is applied, it is static for 30 minutes to observe the strain of the bars, the settlement displacement of the lower chord nodes of the grid structure and the overall bending of the grid structure. Then continue to load until the bars reach the yield strength or the displacement of the lower chord of the grid structure reaches the allowable deflection. After the grid structure is static for 30 minutes, unload the counterweights. When unloading, it is 40kN per level, and at the same time monitor various values and make records.

[0058] During the test, a remotely controlled electric single-girder crane was used for the loading and unloading of the counterweights, and an OCS-type electronic crane scale was suspended below the hook. The maximum weighing capacity of the electronic crane scale is 5t, and the graduation value is 2kg. It is equipped with a digital display and a load recording function to measure the actual weight of the counterweight blocks. The arrangement plan of the counterweight blocks is to place them side by side from the end to the middle, with a spacing of about 150mm. 10 blocks can be placed in a single layer, and after the first layer is full, the second layer is stacked.

[0059] Before placing the counterweight blocks, segmented distribution beams need to be set at the bottom to prevent uneven distribution of the top load caused by excessive settlement in the middle of the grid during the test. The longitudinal distribution beams are made of welded square steel bars dedicated to tower cranes, with a single length of 2.5m - 3.5m. Six of them are selected and divided into two groups. Every three are connected by pin bolts to form a hinge point and placed on the top of a single grid. Below the longitudinal distribution beams are the transverse distribution beams, which are cut from channel steel and span the two spherical joints at the end of the upper chord of the grid as the fulcrums of the longitudinal distribution beams. They are inverted on the spherical joints of the upper chord of the grid. Several angle steels are spot-welded on both the upper and lower sides of the transverse distribution beams as anchoring nodes to prevent slipping.

[0060] The test monitored the deflection of the lower chord nodes of the grid through 8 YWC-type strain displacement sensors with a full-scale value of 100mm and 4 YWC-type strain displacement sensors with a full-scale value of 50mm, and measured the strain of the members using 5×3mm standard resistance strain gauges pasted in the middle of the members. The displacement and strain measurement points were all connected to a CML-1H32 type strain & stress comprehensive tester for monitoring and collecting test data.

[0061] The main stressed part of the grid structure is the longitudinal sheet-shaped single grid. Therefore, the strain measurement points were arranged in the middle of the members within the front and rear two frames of the grid, and the two grids were divided into groups A and B. The upper chord members of group A are numbered AS1 - AS7, the lower chord members are numbered AX1 - AX7, the diagonal web members are numbered AF1 - AF7, and the vertical members are numbered AC1 - AC8. The measurement points of group B are arranged corresponding to those of group A and are numbered accordingly, as Figures 9 - 13 shown.

[0062] After arranging the corresponding measurement points for the internally stressed members and the lower chord nodes of the grid, two groups of strain measurement points were arranged on the transverse members perpendicular to the two stressed grids at the mid-span position of the grid, numbered HS4, HF4, HX4 and HS5, HF5, HX5. These six measurement points are used to observe the stress conditions of the transverse members of the grid under the action of the load. One strain measurement point was arranged on each of the end bolts of the prestressed cables of specimens WJ-2 and WJ-3 to monitor the stress conditions of the prestressed cables in real time.

[0063] The newly added members at the bottom of the lower chord of the test piece WJ-3 are divided into two groups, A and B. 10 corresponding members are selected from each group, numbered A1 - A10 and B1 - B10. Since there are no members in the middle of the lower chord of the space grid, an upward camber effect is formed within the space grid after the prestress is applied. According to the "Technical Specification for Space Grid Structures" (JGJ 7 - 2010), when considering camber for a space grid or truss under large-span conditions, the camber value should not exceed 1 / 300 of the span. For the test piece WJ-3, that is, the camber value is required not to exceed 35 mm, and in design, it can be calculated without considering camber.

[0064] Static Load Test of WJ-1

[0065] Before loading, the self-weight of the space grid and the initial load of the distribution system above it were measured. The total weight of the eight transverse channel steel distribution beams and the two groups of longitudinal distribution beams is 810 kg, and the self-weight of the space grid is 1100 kg, that is, the initial load is 18.72 kN. Due to the special joint structure of the new type of rotary socketed space grid, the gap at the end plate of the joint is inevitable. Under the initial load, the initial settlement at the mid-span of the space grid is about 22 mm, and due to the long and narrow strip structure of the space grid, there is lateral out-of-plane sway under no-load. During the loading process, the hoisting speed of the electric single-girder crane is constant. After preloading two counterweights at the mid-span, the gap at the lower part of the space grid is completely opened, and the space grid no longer generates lateral sway, and the deflection of the lower chord tends to be stable.

[0066] In the formal loading stage, the counterweight blocks were placed from both ends of the space grid towards the middle. The data changes of the two groups of displacement gauges are similar. 1# and 2# are the edge measuring points closest to the supports. The measured displacement values increase uniformly and at a slow rate, with little difference; 5# and 6# are the measuring points at the mid-span of the lower chord, and the displacement values increase faster. When 10 counterweights were loaded, the first layer of the upper part of the space grid was fully covered, and the total load was 195.88 kN. The extreme displacement value of group A is AY6 = 18.25 mm, and the extreme displacement value of group B is BY6 = 21.46 mm. After standing for 30 minutes, the increase in displacement at each measuring point does not exceed 0.25 mm, indicating that the space grid structure is in the elastic stage, no plastic deformation has occurred, and there is still a large bearing capacity upper limit.

[0067] During the standing stage, the data of the acquisition instrument was observed and analyzed. The compressive load on the members in the middle of the upper chord is relatively large, and the tensile load on the members at the mid-span of the lower chord and the adjacent members is relatively large. After the standing stage, the load was continuously applied. At this time, the deflection growth rate of the lower chord became faster, and the displacement gauges at the edge measuring points had a certain torsion from the initial vertical direction, indicating that the space grid began to deform, the mid-span nodes sank, and the edge-span nodes rotated outwards to form an angle.

[0068] A total of 18 counterweights were loaded on the test piece WJ-1, and the converted total bearing capacity is 339.07 kN. At this time, the lower chord tie rod reached the yield strength, and the maximum deflection of the mid-span node of the lower chord of the space grid was 34 mm, and the structural deformation did not reach the allowable deflection. The test was terminated after standing for 30 minutes and unloaded step by step.

[0069] WJ-2 Static Load Test

[0070] Before the formal loading of Specimen WJ-2, prestress was applied to four spherical joints in the middle of the lower chord of the grid and three lower chord bars between them. The external bolts of the screw were tightened alternately by hand to apply prestress, while observing the data of the acquisition instrument and calculating the pre-tightening force value on the steel wire rope in real time. Since the lower chord compression bar is sleeved inside the prestressed steel wire rope, during the tensioning process, the lower chord member is compressed and can reach a self-balanced state, and the prestress can be applied to a relatively high value.

[0071] During the test, a prestress of 50 kN was applied to the lower chord of WJ-2. The initial deflection of the grid under the action of the initial load (self-weight + distribution system) was about 13 mm, indicating that applying prestress can shrink the gap of the lower chord of the grid and effectively control the initial deflection deformation of the grid.

[0072] During the formal loading stage, since the lower chord prestressed cable participated in the tension process and shared the force of the lower chord tie rod, the load on the tie rod at the mid-span of the lower chord was significantly lower than the loads on the adjacent lower chords AX6 and BX2.

[0073] The end mark of the WJ-2 test was that the upper chord member at the mid-span was subjected to the maximum compressive stress and first reached the yield strength. At this time, a total of 21 counterweights were loaded on the upper part of WJ-2, with a calculated total weight of 40073 kg, a converted bearing capacity of 401 kN, and a maximum mid-span deflection of 32.5 mm. The grid structure was left static for 30 minutes, and the maximum increment of the lower chord deflection was 0.16 mm. After the holding time ended, the test was terminated and the upper counterweights were unloaded in stages while monitoring the recovery of the lower chord deflection of the grid. After unloading, the grid returned to the horizontal state, and the displacement gauge value was slightly larger than the initial value, indicating that there was a certain loss of prestress on the steel wire rope after continuous action of the static load.

[0074] WJ-3 Static Load Test

[0075] Specimen WJ-3 had greater changes compared with the previous two specimens. The effect of improving its bearing capacity was studied by increasing the number of grid layers. The assembly process of the grid was similar to that of WJ-1. After assembling the double-layer grid, it was suspended at a certain height and the lower support was made. Subsequently, the positioning and assembly of the bottom layer grid were carried out at the lower part. After the structure was assembled, prestress was applied before the experiment, and the application method was the same as that of WJ-2.

[0076] After the assembly of the test piece WJ-3 is completed, the calculated height reaches 3m. After including the height of the bottom support and the upper distribution system, the height of the top of the grid is close to 4m. To ensure the safety of high-altitude operators, steel ladders are set at both ends of the grid, and planks are laid on their tops. At the same time, safety ropes are erected at high altitudes. To prevent the grid from tilting, diagonal extension supports are extended from the mid-chord nodes of the grid as safety measures. To ensure that the grid has sufficient out-of-plane stability, two groups of chain hoists are used to fasten the nodes transversely. Since the expected bearing capacity of the three-layer grid is relatively high, the preliminary load grading is appropriately amplified. After the first two tests, the self-weights of the counterweight blocks have been marked. During the hoisting process, the counterweight blocks with larger self-weights are first selected and placed on the first and second floors. After the second floor is filled, it is left static for 30 minutes. During the static stage, the maximum displacement of the grid is AY6 = 22.85mm. In the subsequent loading stage, the counterweight blocks with smaller self-weights are selected and loaded in single-block increments.

[0077] After applying the prestress to the lower chord of the grid, the deflection of the grid is further reduced. The test ends when the prestressed cable reaches the safety allowable limit. At this time, a total of 28 counterweight blocks are loaded, the total weight of the upper part of the grid is 52911kg, the converted bearing capacity is 518.53kN, and the maximum deflection at the mid-span of the lower chord is 27.83mm. After the grid is left static for 30 minutes, the test is terminated and the counterweights are unloaded. After complete unloading, the deformation of the grid is restored, the deflection increases slightly compared with the initial stage, and the prestress value on the cable decays.

[0078] The grid structure is a space structure formed by the intersection of the axes of several members at fixed nodes to form many hinged points. In the rotary socketed grid structure, the members are reliably connected to the spherical nodes through end plate docking and rotary socket joints, forming approximately two hinged points at both ends of the members. The members are only subjected to axial loads and do not bear bending moments.

[0079] To more accurately establish the finite element model of the grid, the PIPE288 pipe element is selected for the basic members, and the LINK180 rod element is selected for the prestressed cable of the lower chord of the grid. For PIPE288, it can be set as a thin-walled circular pipe by setting the parameter KEYOPT(4)=2, which can more reasonably simulate the cross-sectional form of the grid members; while the LINK180 element is a collection of all LINK elements in the ANSYS basic version, integrating all the functions of axial tension and compression rods. In the new version, it is set as a tension-only element by modifying the parameter TENSKEY = 1 to simulate the force form of the cable. The LINK180 and PIPE288 elements are similar, each having two nodes, three translational degrees of freedom and three rotational degrees of freedom, so they can be directly coupled. Both elements can be simplified and applied to the solution of complex structural problems such as linear and nonlinear.

[0080] In the finite element model, the PIPE288 element is set as a thin-walled circular tube model with an outer diameter of 50 mm and a wall thickness of 4 mm. To simplify the calculation, the cross-sectional area of the LINK180 element is set to 130 mm². The same material properties are defined for the members and cables, with an elastic modulus E = 2.06×10⁵ N / mm² and a Poisson's ratio v = 0.3.

[0081] The prestress is applied to the lower chord cables by the temperature reduction method. The linear expansion coefficient α1 of the cable material needs to be set to 1.1×10⁻⁵, and the cable strain is calculated according to the designed prestress value. ε And the temperature reduction value T can be obtained by dividing the strain by the linear expansion coefficient, that is, strain = tensile force / (cable cross-sectional area × cable elastic modulus), and temperature reduction value = strain / linear expansion coefficient. The specific calculation steps are shown in Formulas 4-1 and 4-2. Before performing the structural solution, the calculated temperature reduction value is applied to the LINK180 element using the BFE command. For the actual structure, when the stiffness is large, the numerical error of the applied prestress is very small.

[0082]

[0083]

[0084] ANSYS software has a total of three model establishment rules, including directly establishing a finite element model, first geometric modeling and then converting it into a finite element model, and hybrid modeling method

[44] . Directly establishing a finite element model is suitable for structures with a small number of structural elements and clear mesh division. The method of establishing a geometric model is suitable for any structure, especially complex structures or 3D solid elements. After modeling, the modification and division of high and low orders are more flexible, but it is difficult to divide the mesh of geometric models under special conditions. Hybrid modeling is to first establish a geometric model and form a finite element model through mesh division, and then supplement some contact elements and coupled degrees of freedom in the structure, and finally form a complete finite element model. The three grid structure forms designed in this topic are relatively simple, and the unit mesh division is clear. The modeling method of directly establishing a finite element model is selected.

[0085] According to the single-span seven-step socketed grid structure, the basic rectangular coordinate system is selected. First, the coordinates of the spherical nodes are located, and then according to the grid member layout rules, PIPE288 elements are generated between the corresponding nodes. Among them, each member is divided into one element to form the basic structure of the grid. According to the lower structure form of the grid (whether to tension the prestressed cable), the setting of the LINK180 element is determined. The bearing capacity analysis of the welded hollow spherical node element has been carried out before, and it can be seen that its strength is relatively high. During the establishment of the finite element model, the hollow spherical node is simplified and replaced by a spatial hinge node.

[0086] The members made of Q550 low-alloy steel belong to isotropic metallic materials and are applicable to the Mises yield criterion. The material adopts a stress-strain constitutive relationship described by two straight lines.

[0087] In the vertical loading test, the space grid was simply supported on rigid supports. When applying the constraint conditions of the finite element model, hinge constraints were imposed on its 4 support points. The vertical loads during the test were evenly loaded onto a total of 16 nodes at the top of the space grid, and a structural linear static analysis was performed on the space grid structure.

[0088] In the structural static analysis, the space grid was stressed within the elastic range throughout the whole process. The loading and constraint conditions were similar to those of the space grid loading test. The cooling method was used to apply prestress to the cable elements of the lower chord of the space grid, and the bearing capacity performance of the space grid under the action of loads was analyzed by comparison.

[0089] A total vertical load of 339 kN was applied to the top of the space grid. The axial forces of the members and the vertical displacement values at the mid-span obtained from the static analysis in the elastic state. The axial force of the member with the largest stress in the test and the test deflection value were compared with the finite element simulation results.

[0090] Table 4-1 Comparison between test values and finite element results

[0091]

[0092] In the WJ-2 test, a prestress value of 50 kN was applied to the prestressed cables of the lower chord. At the end of the test, a total vertical load of 401 kN was applied to the top of the space grid. The axial forces of the members and the displacement conditions of the nodes of the lower chord of the space grid obtained from the static analysis in the elastic state were obtained. At the same time, the case of prestress P = 100 kN was explored and analyzed. The stress, axial force of the member with the largest stress in the test and the test deflection value were compared with the finite element simulation results, as shown in Table 4-2.

[0093] Table 4-2 Comparison between test values and finite element results

[0094]

[0095] In the test of specimen WJ-3, a total vertical load of 519 kN was applied to the top of the space grid, and the same load was evenly loaded onto the model nodes, and the axial forces and deflection conditions of the members under different prestress conditions were analyzed.

[0096] The test values of the axial force and deflection of the space grid were compared with the finite element simulation results, as shown in Table 4-3.

[0097]

[0098] P represents the prestress condition level, and F represents the total load on the upper part of the space grid.

[0099] (1) Comparative analysis of WJ-1 test and simulation

[0100] Under the action of uniformly distributed vertical load, the stress of the finite element model of the grid is consistent with that of the double-layer basic grid, showing a typical stress mode of compression in the upper chord and tension in the lower chord. Within the same grid, the closer to the middle, the greater the stress of the chord members. The end vertical members are directly connected to the supports and are subject to large axial compression forces, while the other vertical members are hardly stressed; the end web members are subject to large axial forces, and the web members closer to the middle are less stressed, and the stresses of the web members within the same grid are symmetric with each other. The stress laws of the web members and the end vertical members are related to their positions. If the axis of the web member passes through the support node, the web member bears the axial compression force and the vertical member is hardly stressed; conversely, if the axis of the web member does not pass through the support node, the end vertical member bears the axial compression force, and at this time the web member is in tension. Generally speaking, the stress of the internal members of the grid shows clear regularity. The front and rear grids are centrosymmetric, and the stresses of the diagonally symmetric members are almost exactly the same. As can be seen from Table 4-1, under the action of the same vertical load, the stress distribution of the members in the finite element model coincides with that in the grid, and the similarity of the compression characteristic members is relatively high.

[0101] (2) Comparative analysis of the test and simulation results of WJ-2

[0102] Through comprehensive analysis of Table 4-2 and comparison with the double-layer basic grid WJ-1, it can be seen that the prestressed tension cables in the lower chord of the grid greatly improve the bearing capacity of the grid structure and can effectively control the displacement of the lower chord nodes. The stress distribution of the members in the simulation results is relatively close to the test values, but the deflection values are on the small side; compared with the finite element model, under the action of the same external load, increasing the prestress value has little effect on the stress of the members, but the stress on the cables increases faster when the grid is loaded, indicating that the cables can actively bear the tensile stress in the lower chord. Microscopically, the loads on the members acting synchronously with the lower chord cables are significantly reduced, and the stresses on the members adjacent to the cables increase. Since the tensile design strength of the cables is relatively high, the members adjacent to the cables are the weak parts of the grid.

[0103] (3) Comparative analysis of the test and simulation results of WJ-3

[0104] Using the control variable method, the effects of changes in external load and prestress on the stress of the grid are discussed respectively. The comparison between the measured values and the simulated calculated values is shown in Table 4-3.

[0105] From the comparison of the finite element models in the same group, it can be seen that under the action of the same external load, the increase in prestress can effectively control the deflection deformation of the space grid structure. Through the arching effect of the cables in the lower chord of the three-layer space grid, the upper chord members are first subjected to relatively large tensile forces, and then the upper chord members have sufficient loading processes and stress change spaces, ultimately achieving the purpose of reducing the internal forces of the members and concentrating the relatively large tensile stresses on the prestressed cables. Under the same prestress condition, different loads are applied to the space grid. As the load increases, the deflection deformation of the space grid increases, but it does not reach the allowable deflection. The greater the load, the more tensile load the prestressed cable can replace the lower chord tie rod to bear. After increasing the height of the space grid, the typical characteristics of the upper chord members being in compression and the lower chord members being in tension are changed, and the internal force distribution of the members in the three-layer prestressed space grid is optimized and adjusted. By comparing the space grid structure with the finite element model, the prestressed cables and the adjacent members are both subjected to the maximum tensile stress, and the stress simulation is relatively accurate; due to the butt gap of the end plates, the space grid has an initial settlement deformation, and there is a slight difference from the deflection calculated by the finite element simulation.

[0106] (4) By making a horizontal comparison between WJ-2 and WJ-3, when the same prestress is applied to the space grid, since WJ-3 increases the number of layers of the space grid and improves the stress level, the overall bearing capacity of the space grid structure is increased by approximately 29%. The internal force conditions of the members in the three-layer prestressed space grid are significantly improved, and the deflection of the lower chord of the space grid is also effectively controlled. By comparing WJ-1 and WJ-2, the addition of the prestressed cable increases the bearing capacity of the space grid by 18.3%, reduces the internal forces of the tie rods, and improves the safety performance.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and the description of the present invention.

Claims

1. Rotating disc-type space grid structure, characterized by: The invention comprises a plurality of spherical node connectors and connecting pipes (5) connected between the spherical node connectors. The spherical node connector comprises a hollow ball (1). Branch pipes (2) are arranged in the upper, lower, left, right, front and rear directions of the hollow ball (1). The branch pipes (2) are connected to the connecting pipes (5) via a rotating disc buckle structure.

2. The rotating disc-type space grid structure according to claim 1 is characterized in that: An end sealing plate (3) is provided at the end of the branch pipe (2) and the end of the connecting pipe (5), and a clamping claw (4) is provided on the circumference of the end sealing plate (3), and the two clamping claws (4) are connected together by a rotating disc buckle (6).

3. The rotating disc-type space grid structure according to claim 2 is characterized in that: The rotating disc buckle (6) is provided with a notch (9) for the clamping claw (4) to be clamped in and a stopper (10) for locking the clamping claw (4).

4. The rotating disc-type space grid structure according to claim 3 is characterized in that: It also includes a positioning pin (7) adapted to the notch (9). When the claw (4) rotates and is blocked by the block (10), the positioning pin (7) is used to insert into the notch (9) to prevent the claw (4) from escaping from the block (10).

5. The rotating disc-type space grid structure according to claim 4 is characterized in that: A gripping convex strip (11) for easy gripping is arranged at one end of the positioning latch (7), and a ratchet claw (12) for preventing backward movement is arranged at the other end.

6. The rotating disc-type space grid structure according to claim 5 is characterized in that: A through hole (8) is provided on the positioning latch (7) to prevent the positioning latch (7) from cracking.

7. A method for detecting the force of a rotating disk-type space grid structure, characterized in that: include The connecting pipe (5) is subjected to axial tension and axial compression performance tests, and the axial test failure phenomenon of the connecting pipe (5) is observed. The displacement and strain data of the rod are integrated to draw load-displacement and stress-strain curves, analyze the bearing capacity, deformation performance and stress distribution of the connecting pipe (5), and explore the influence of the length and material of the rod on its bearing capacity; Perform unidirectional tension and pressure tests on the hollow sphere (1) to analyze the bearing capacity, failure characteristics and spherical surface stress distribution of the node of the hollow sphere (1); draw a curve of the relationship between load, displacement and strain based on the displacement and strain data, and perform stress analysis on the surface of the spherical node, the heat affected zone of the weld and the welded short rod; A vertical loading test is performed on the grid structure to test its bearing capacity; a corresponding load-displacement curve and a load-strain curve of the rod are drawn according to the test results, and the deformation characteristics of the structure and the stress distribution of the connecting pipe (5) are analyzed; Based on ANSYS software, the corresponding finite element model was established, loaded and solved, and compared with the above test results to obtain the factors and laws that affect the bearing capacity performance of the grid, providing an application basis and theoretical foundation for the application of the rotating disc-type grid.

8. The method for detecting the force of a rotating disk-type space grid structure according to claim 7, characterized in that: When the hollow ball (1) is subjected to a unidirectional tensile test, an eight-hole flange is placed on one side of the hollow ball (1), an anchor rod at the end of a steel wire rope is passed through the holes of the eight-hole flange, and bolts are tightened on the outside; the tensile force on the eight-hole flange is transmitted to the hollow ball (1) by pulling the steel wire rope, thereby achieving a unidirectional tensile test on the hollow ball (1).

9. The method for detecting the force of a rotating disk-type space grid structure according to claim 7, characterized in that: When the grid structure is subjected to vertical loading test, the structural static loading system is adopted, and monotonous continuous graded loading is carried out by means of loading. Two counterweights are loaded at each level and placed symmetrically. After reaching the load level, the load is maintained for 5 minutes, and the deformation of the grid is monitored.

10. The method for detecting the force of a rotating disk-type space grid structure according to claim 9, characterized in that: Before placing the counterweight, a segmented distribution beam needs to be set at the bottom to prevent excessive settlement of the middle of the grid frame during the test, resulting in uneven distribution of the top load. Below the longitudinal distribution beam is a transverse distribution beam, which is cut from a channel steel and spans across two ball nodes at the ends of the upper chord of the grid frame. It serves as a fulcrum for the longitudinal distribution beam and is inverted on the uppermost vertical connection pipe (5). Several angle steels are spot-welded above and below the transverse distribution beam as anchor nodes to prevent it from slipping.

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