Cable force control method for large-span space truss roof inhaul cable

Abstract

According to the large-span space truss roof inhaul cable force control method, the staged dynamic tensioning and real-time monitoring technology is adopted, non-torsion cable unfolding is completed through mechanical and manual cooperation, and an anti-retraction clamp and a vibrating wire sensor are additionally arranged at the anchoring end; a guide pulley block is used for accurate positioning, and a double-oil-pump four-top synchronous system is used for implementing bidirectional symmetrical tensioning; and a three-stage gradient tensioning process (50-90-105% of designed cable force) is combined with load-holding stabilizing treatment and roof displacement synchronous monitoring. The cable force detection device is fixed through front and rear hoops, a gear meshing type vibrating wire sensor and an anti-twisting structure are arranged in the cable force detection device, accurate measurement is achieved through tooth groove meshing, and a soft cushion layer protects a cable body from being damaged. According to the system, double-top synchronous control is achieved through the oil way flow dividing technology, the multi-stage tensioning technology is matched, the problems of insufficient cable force control precision and asynchronous tensioning of a large-span structure are solved, and the construction safety and the structure forming precision are remarkably improved.

Description

Technical Field

[0001] This paper relates to the technical field of truss roof cables, specifically the cable force control method for large-span space truss roof cables. Background Art

[0002] The cable-stayed structure of a truss roof primarily comprises cables, trusses, and struts, forming a complete spatial structural system. One end of the cable is connected to the outer end of the truss, and the other end is connected to a horizontal lower rigid ring or other fixed point. By introducing prestress, the struts are compressed, which reverses the load on the shell and effectively unloads the structure. Under the action of additional loads, the shell and cables work together to resist the load, effectively reducing internal forces and deformation in the structure.

[0003] In cable construction, cable tension control is often particularly important, and the premise of controlling cable tension is how to accurately measure cable tension. Among the common cable tension monitoring methods, the pressure gauge method is not suitable for long-term monitoring; the magnetic flux method and the vibration method are complicated to operate; the clamp method calculates cable tension by measuring strain, which is simple and efficient. The vibrating wire strain method is based on the relationship between the string vibration frequency and tension. It has the advantages of simple structure, convenient installation, and strong anti-interference ability. However, for complex cables with articulated structures (such as steel strands and semi-parallel steel wire bundles), the cross-section rotates relative to each other after being stressed, which will cause torsional offset at both ends of the strain gauge. The vibrating wire strain gauge needs to maintain a horizontal measurement state. Such deformation will cause measurement errors or failure. Therefore, it is necessary to provide an improved technical solution to address the shortcomings of the above-mentioned existing technologies. Summary of the Invention

[0004] To solve the existing roof cable tensioning construction method:

[0005] (1) When the cable is stressed, the cross section rotates relative to each other, which will cause the two ends of the strain gauge to torsion offset. The vibrating wire strain gauge needs to maintain a horizontal measurement state. Such deformation will cause measurement errors or failure.

[0006] (2) The independent operation of multiple jacks can easily cause asynchronous tensioning at both ends of the cable, leading to local stress concentration or excessive structural deformation.

[0007] (3) In traditional cable construction, the displacement detection of the roof cannot be effectively correlated with the cable tensioning, that is, the tensioning force and the roof displacement cannot be adjusted simultaneously in real time during the tensioning process.

[0008] The technical solution adopted in the present invention is as follows:

[0009] A method for controlling cable forces in a large-span space truss roof is characterized in that the construction method comprises the following steps:

[0010] Step 1: hoisting and extending the cable drum. Hoist the cable drum (including the cable drum body and the matching brake) to the predetermined cable extension area of the scaffold (8) through a special hoisting device, ensure that the cable drum axis is consistent with the cable extension direction, adjust the cable drum brake to a semi-loose state, so that the cable body (2) can rotate freely but maintain controllable tension, fix the wire rope of the winch (1) to the end of the cable body, start the winch (1) and pull the cable body at a set speed (≤2m / min), and during the cable extension process, set up a manual auxiliary cable pusher every 5m, use anti-slip rubber pads to avoid direct friction between the cable body and the ground, and monitor the straightness of the cable body through a level meter and a laser rangefinder during the entire cable extension process to ensure that there is no twisting or deviation;

[0011] Step 2: After the cable is extended, a temporary fixture (13) is installed at a distance of 5m±0.5m from the anchor end, and a cable force detection device (3) is installed at the predetermined position of the cable (2) (at the 1 / 4, 1 / 2, and 3 / 4 spans in the middle of the span) to monitor the cable force changes in real time. The cable force data is uploaded to the monitoring terminal through the wireless transmission module, and the cable force deviation warning threshold (±5% of the design value) is set;

[0012] Step 3: Install the guide pulley group (4) on the top of the scaffold (8) to ensure that the cable body is lifted vertically, start the winch (1) to lift the cable body to the designed height (error ≤ ± 10mm), and simultaneously connect the cable ear plate (2-1) with the embedded bolts of the cable node (7) through the guide pulley group (4). The bolt tightening torque should be greater than 200N·m. Connect the cable body (2) and the support rod (9) through a U-shaped clamp. The clamp spacing should be less than 1.5m. A shock-absorbing rubber pad is set at the connection. Four 100-ton light jacks (5) and two oil pumps (6) are symmetrically arranged at both ends of the cable. A spherical hinge support is set between the jack and the cable ear plate (2-1). The accuracy of the oil pump pressure gauge is not less than 0.1MPa.

[0013] Step 4: Start the jack (5) to perform the first-level tensioning, tensioning to 50%±2% of the designed cable force and then hold the load for 15 minutes. During the holding period, record the cable force and displacement data every 5 minutes. Perform the second-level tensioning to 90%±2% of the designed cable force and hold the load for 30 minutes. At the same time, monitor the displacement of the roof support through the total station (accuracy ≤±1mm). Perform the third-level tensioning to 105%±2% of the designed cable force and hold the load for 60 minutes. During the tensioning process, adjust the jack oil pressure in real time to ensure that the tensioning force synchronization deviation at both ends is ≤±3%. After the tensioning is completed, unload the jack and install a permanent anchor. Set an anti-corrosion coating between the anchor and the cable body.

[0014] Furthermore, a cable tension control method for a large-span space truss roof is characterized in that a total station is used to observe and record the displacement of the entire roof in real time during the overall cable tensioning process, so that the tensioning force and roof displacement can be adjusted simultaneously in real time during the tensioning process to meet the design requirements.

[0015] Furthermore, a cable tension control method for a large-span space truss roof is characterized in that: the cable tension detection device in step 2 comprises: a front hoop (3-1), a rear hoop (3-2), and a vibrating string cable tension meter (3-3); the vibrating string cable tension meter (3-3) is fixed on the rear hoop (3-2); the tail of the vibrating string cable tension meter (3-3) is in the torsion groove (3-6) of the front hoop (3-1); each hoop has a rotating shaft (3-4), a fixing plate (3-5) and an internal cushion (3-7); the front hoop (3-1) and the rear hoop (3-2) are both clamped on the cable (2); the front hoop (3-1) and the rear hoop (3-2) are both fixed to the cable (2) through bolts (3-9) and the fixing plate (3-5).

[0016] Furthermore, a cable tension control method for a large-span space truss roof is characterized in that: a rotating gear (3-8) is provided at the tail end of the vibrating wire tension meter (3-3); the rotating gear (3-8) should be provided with a large damping and cannot be easily rotated in the torsion groove (3-6); gear teeth are provided in the torsion groove (3-6) so that the rotating gear (3-8) can be rotated in the torsion groove (3-6) of the front clamp (3-1); and during installation, the rotating gear (3-8) should be located in the middle of the torsion groove (3-6).

[0017] Furthermore, the cable force control method for a large-span space truss roof is characterized in that the jack tensioning in step 4 includes the following steps:

[0018] Step 1: The oil outlet of the oil pump (6) should be connected to the diverter valve (10), and the two interfaces of the diverter valve (10) should be connected to the oil inlets (5-1) of the two jacks (5) to control the oil volume of the two jacks (5);

[0019] Step 2: The oil outlets (5-2) of the two jacks (5) are connected to the oil pump (6) through the oil pipe (11);

[0020] Step 3: Start the oil pump (6), and the oil is evenly distributed to the two jacks (5) through the diverter valve (10). The oil in the jacks (5) is discharged through the oil outlet (5-2) to carry out the tensioning construction.

[0021] Furthermore, a method for controlling the tension of cables of a large-span space truss roof is characterized in that: in step 1, the two interfaces of the diverter valve (10) are connected to the oil inlets (5-1) of the two jacks (5), and the oil inlet ends thereof should be connected to a hydraulic check valve (12). When the oil pump (6) is started, the oil is divided into two paths through the diverter valve (10), and the hydraulic check valve (12) is automatically opened under positive oil pressure, and the two jacks (5) are lifted synchronously. After reaching the specified tensioning height, the hydraulic check valve (12) is automatically locked without control oil pressure.

[0022] Furthermore, a method for controlling the tension of cables in a large-span space truss roof is characterized in that: after the tensioning construction, when the jack (5) needs to be lowered, the oil pump (6) supplies oil in the reverse direction, supplies control oil to the hydraulically controlled one-way valve K port, and the oil flows back to complete the lowering.

[0023] Furthermore, a method for controlling the tension of cables of a large-span space truss roof is characterized in that: when the oil pump (6) is started in step 3 and the oil is evenly distributed to the two jacks (5) through the diverter valve (10), the oil pump (6) should be computer-controlled and have the same flow rate PLC control as the oil pump (6) on the other side of the cable, so as to control the oil output volume of the oil pump (6) and thus control the cable tension value.

[0024] Beneficial effects of the present invention

[0025] (1) The torsion groove of the cable force detection device solves the problem that the cross section of the cable rotates relative to each other after being stressed, which causes torsional offset at both ends of the strain gauge. The vibrating wire strain gauge needs to maintain a horizontal measurement state, and such deformation will cause measurement errors or failure.

[0026] (2) Through three-level gradient tensioning (50%-90%-105%) combined with load-holding aging treatment, the material stress relaxation is released in stages to ensure the stability of the cable force.

[0027] (3) The tensioning process is linked to the roof displacement monitoring in real time. By dynamically adjusting the oil pump flow, the coordinated control of cable force and structural deformation is achieved. The real-time roof displacement can be adjusted during the tensioning process, and the forming accuracy is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Roof cable construction flow chart

[0029] Figure 2 Schematic diagram of the roof cable structure

[0030] Figure 3 Schematic diagram of roof cable construction

[0031] Figure 4 Schematic diagram of the cable force detection device application

[0032] Figure 5 Schematic diagram of the cable force detection device

[0033] Figure 6 Schematic diagram of the vibrating wire tension meter components

[0034] Figure 7 Schematic diagram of the front hoop cross section

[0035] Figure 8 Schematic diagram of jack tensioning construction

[0036] In the figure: 1 is a winch; 2 is a cable; 3 is a cable force detection device; 3-1 is a front clamp; 3-2 is a rear clamp; 3-3 is a vibrating wire tension meter; 3-4 is a rotating shaft; 3-5 is a fixed plate; 3-6 is a torsion groove; 3-7 is an internal cushion; 3-8 is a rotating gear; 3-9 is a bolt; 4 is a guide pulley group; 5 is a jack; 6 is an oil pump; 7 is a cable node; 8 is a scaffold; 9 is a support rod; 10 is a diverter valve; 11 is an oil pipe; 12 is a hydraulic one-way valve; 13 is a temporary clamp. DETAILED DESCRIPTION

[0037] like Figure 1 、 Figure 2 and Figure 3 As shown: hoist the cable drum to the predetermined cable extension area of the scaffolding (8), and adjust the cable drum brake to a semi-loose state. Connect the wire rope of the winch (1). Start the winch (1) to pull the cable body. Simultaneously use manual auxiliary cable pushing to avoid friction between the cable (2) and the ground; after the cable extension is completed, install a temporary clamp (3) 5m away from the anchor end to prevent retraction. The cable body must be kept free of twisting during the entire cable extension process. Install a cable force detection device (3) at the predetermined position of the cable (2) to perform real-time cable force detection. Use the guide pulley group (4) and the winch (1) to lift the cable body to the designed height. At the same time, connect the cable ear plate (2-1) to the cable node (7) through the guide pulley group (4). The cable (2) The cable body is connected to the support rod (9), and four 100-ton light jacks (5) and two oil pumps (6) are used to perform symmetrical tensioning at both ends. At the same time, tensioning ends are set at the cable head ear plates (2-1) at both ends of the cable; the jacks (5) are used to perform first-level tensioning, and after tensioning to 50% of the design cable force, the load is held for 15 minutes, followed by second-level tensioning: 90% of the design cable force (holding load for 30 minutes) and then third-level tensioning: 105% of the design cable force (holding load for 60 minutes), while real-time monitoring of roof support displacement.

[0038] like Figure 4 、 Figure 5 、 Figure 6 and Figure 7As shown: A cable force detection device comprises: a front clamp (3-1), a rear clamp (3-2), and a vibrating string cable force meter (3-3); the vibrating string cable force meter (3-3) is fixed on the rear clamp (3-2); the tail of the vibrating string cable force meter (3-3) is in a torsion groove (3-6) of the front clamp (3-1); each clamp has a rotating shaft (3-4), a fixing plate (3-5), and an internal cushion (3-7); the front clamp (3-1) and the rear clamp (3-2) are clamped on the cable (2); the front clamp (3-1) and the rear clamp (3-2) are fixed to the cable (2) via bolts (3-9) and the fixing plate (3-5). The vibrating wire tension meter (3-3) has a rotating gear (3-8) at its tail end. The rotating gear (3-8) should be provided with a large damping so as not to easily rotate in the torsion groove (3-6). The torsion groove (3-6) has gear teeth therein, which enable the rotating gear (3-8) to rotate in the torsion groove (3-6) of the front clamp (3-1). During installation, the rotating gear (3-8) should be located in the middle of the torsion groove (3-6). When the cable is stressed, the cross section rotates relative to the cable, the rear clamp (3-2) is relatively displaced, and the rotating gear (3-8) can rotate relative to the cable in the torsion groove (3-6), thereby offsetting the effect of the torsion on the vibrating wire tension meter (3-3).

[0039] like Figure 8 As shown, when the jack is tensioned, the oil pump (6) outlet should be connected to the diverter valve (10), and the two interfaces of the diverter valve (10) should be connected to the oil inlets (5-1) of the two jacks (5) to control the oil volume of the two jacks (5). The oil outlets (5-2) of the two jacks (5) are gathered together through the oil pipe (11) to the oil pump (6). The oil pump (6) is started, and the oil is evenly distributed to the two jacks (5) through the diverter valve (10). The oil in the jack (5) is discharged through the oil outlet (5-2) to carry out the tensioning construction. When the jack (5) needs to be lowered, the oil pump (6) supplies oil in the reverse direction and supplies control oil to the hydraulic control check valve k port, and the oil flows back to complete the lowering.

Claims

1. A method for controlling cable forces in a large-span space truss roof, characterized by: The construction method includes the following steps: Step 1: hoisting and extending the cable drum. Hoist the cable drum (including the cable drum body and the matching brake) to the predetermined cable extension area of the scaffold (8) through a special hoisting device, ensure that the cable drum axis is consistent with the cable extension direction, adjust the cable drum brake to a semi-loose state, so that the cable body (2) can rotate freely but maintain controllable tension, fix the wire rope of the winch (1) to the end of the cable body, start the winch (1) and pull the cable body at a set speed (≤2m / min), and during the cable extension process, set up a manual auxiliary cable pusher every 5m, use anti-slip rubber pads to avoid direct friction between the cable body and the ground, and monitor the straightness of the cable body through a level meter and a laser rangefinder during the entire cable extension process to ensure that there is no twisting or deviation; Step 2: After the cable is extended, a temporary fixture (13) is installed at a distance of 5m±0.5m from the anchor end, and a cable force detection device (3) is installed at the predetermined position of the cable (2) (at the 1 / 4, 1 / 2, and 3 / 4 spans in the middle of the span) to monitor the cable force changes in real time. The cable force data is uploaded to the monitoring terminal through the wireless transmission module, and the cable force deviation warning threshold (±5% of the design value) is set; Step 3: Install the guide pulley group (4) on the top of the scaffold (8) to ensure that the cable body is lifted vertically, start the winch (1) to lift the cable body to the designed height (error ≤ ± 10mm), and simultaneously connect the cable ear plate (2-1) with the embedded bolts of the cable node (7) through the guide pulley group (4). The bolt tightening torque should be greater than 200N·m. Connect the cable body (2) and the support rod (9) through a U-shaped clamp. The clamp spacing should be less than 1.5m. A shock-absorbing rubber pad is set at the connection. Four 100-ton light jacks (5) and two oil pumps (6) are symmetrically arranged at both ends of the cable. A spherical hinge support is set between the jack and the cable ear plate (2-1). The accuracy of the oil pump pressure gauge is not less than 0.1MPa. Step 4: Start the jack (5) to perform the first-level tensioning, tensioning to 50%±2% of the designed cable force and then hold the load for 15 minutes. During the holding period, record the cable force and displacement data every 5 minutes. Perform the second-level tensioning to 90%±2% of the designed cable force and hold the load for 30 minutes. At the same time, monitor the displacement of the roof support through the total station (accuracy ≤±1mm). Perform the third-level tensioning to 105%±2% of the designed cable force and hold the load for 60 minutes. During the tensioning process, adjust the jack oil pressure in real time to ensure that the tensioning force synchronization deviation at both ends is ≤±3%. After the tensioning is completed, unload the jack and install a permanent anchor. Set an anti-corrosion coating between the anchor and the cable body.

2. The method for controlling cable tension in a large-span space truss roof according to claim 1, wherein: During the overall process of cable tensioning, a total station should be used to observe and record the displacement of the entire roof in real time, so that the tensioning force and roof displacement can be adjusted simultaneously in real time during the tensioning process to meet the design requirements.

3. The method for controlling cable tension in a large-span space truss roof according to claim 1, wherein: The cable force detection device in step 2 comprises: a front hoop (3-1), a rear hoop (3-2), and a vibrating string cable force meter (3-3); the vibrating string cable force meter (3-3) is fixed on the rear hoop (3-2); the tail of the vibrating string cable force meter (3-3) is in the torsion groove (3-6) of the front hoop (3-1); each hoop has a rotating shaft (3-4), a fixing plate (3-5), and an internal cushion (3-7); the front hoop (3-1) and the rear hoop (3-2) are both clamped on the cable (2); and the front hoop (3-1) and the rear hoop (3-2) are both fixed to the cable (2) via bolts (3-9) and the fixing plate (3-5).

4. The method for controlling cable tension in a large-span space truss roof according to claim 2, wherein: The vibrating wire tension meter (3-3) has a rotating gear (3-8) at the tail end. The rotating gear (3-8) should be provided with a large damping so as not to be easily rotated in the torsion groove (3-6). The torsion groove (3-6) has gear teeth so that the rotating gear (3-8) can be rotated in the torsion groove (3-6) of the front clamp (3-1). When installed, the rotating gear (3-8) should be located in the middle of the torsion groove (3-6).

5. The method for controlling cable tension in a large-span space truss roof according to claim 1, wherein: The jack tensioning in step 4 includes the following steps: Step 1: The oil outlet of the oil pump (6) should be connected to the diverter valve (10), and the two interfaces of the diverter valve (10) should be connected to the oil inlets (5-1) of the two jacks (5) to control the oil volume of the two jacks (5); Step 2: The oil outlets (5-2) of the two jacks (5) are connected to the oil pump (6) through the oil pipe (11); Step 3: Start the oil pump (6), and the oil is evenly distributed to the two jacks (5) through the diverter valve (10). The oil in the jacks (5) is discharged through the oil outlet (5-2) to carry out the tensioning construction.

6. The method for controlling cable tension in a large-span space truss roof according to claim 4, wherein: In step 1, the two interfaces of the diverter valve (10) are connected to the oil inlets (5-1) of the two jacks (5), and the oil inlet ends thereof should be connected to a hydraulic check valve (12). When the oil pump (6) is started, the oil is divided into two paths through the diverter valve (10), and the hydraulic check valve (12) is automatically opened under positive oil pressure, and the two jacks (5) are lifted synchronously. After reaching the specified tensioning height, the hydraulic check valve (12) is automatically locked without control oil pressure.

7. The method for controlling cable forces in a large-span space truss roof according to claim 4, wherein: After the tensioning construction, when the jack needs to be lowered, the oil pump supplies oil in reverse and supplies control oil to the hydraulic control one-way valve K port, opens the one-way valve, and the oil flows back to complete the descent.

8. The method for controlling cable forces in a large-span space truss roof according to claim 4, wherein: In step 3, the oil pump (6) is started, and the oil is evenly distributed to the two jacks (5) through the diverter valve (10). The oil pump (6) should be computer-controlled and have the same flow rate as the oil pump (6) on the other side of the cable, which is controlled by a PLC to control the oil output of the oil pump (6) and thus control the cable tension value.

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