Small load substitution device and method suitable for large-tonnage cable load-bearing fire test

Abstract

The application is a small load substitution device and method for fire test of large tonnage cable load bearing, which comprises three systems, namely, a self-balancing cable stress loading system, a self-adaptive hearth heat insulation and smoke exhaust system and a multi-element data monitoring system.The self-balancing cable stress loading system comprises a self-balancing cable translation counterforce frame and two subsystems of transmission anchoring and fixed anchoring.The method is a substitution model which can reflect the real thermal force coupling process of the cable, i.e., the structure is arranged by combination of force-bearing steel wires and non-force-bearing steel wires, the force-bearing steel wires are uniformly and spacedly distributed in the cable cross section, and the force-bearing steel wires in the cable replace the force of the full-size cable, so that the heat transfer of the full-size real cable under fire is replaced by the combination of the force-bearing steel wires and the non-force-bearing steel wires.The application can study the influence of different cable diameters, loads, constraints, fires, fire protection and fire time on the mechanical properties of the cable, and can realize the thermal force coupling process of the full-diameter real cable by small tonnage loading.

Description

Technical Field

[0001] This invention belongs to the field of bridge multi-diameter cable load-fire coupling technology, specifically relating to a small load alternative device and method applicable to fire tests of large-tonnage cables under load. Background Technology

[0002] With economic development, long-span bridges experience massive traffic volumes, with hazardous chemical transport vehicles and large passenger buses making up a significant portion. This presents a prominent fire safety hazard, and bridge fires severely threaten the structural safety of bridges. Main cables and suspenders are crucial force-transmitting components of bridge structures, typically composed of steel wire bundles and strands. High-strength steel wires and strands are highly susceptible to damage in fires and are difficult to repair or replace. Therefore, the fire safety of cables faces significant challenges.

[0003] Bridge cables typically carry a certain load during a fire. Therefore, when studying the evolutionary response and fire resistance of cables under fire, the influence of the load should be considered, including deformation, fire resistance limit, and degradation of mechanical properties. This helps to accurately simulate the actual fire conditions of cables. Furthermore, when a bridge fire occurs, the main cable and suspenders will exhibit different thermal responses, affecting the mechanical properties of the cables. Different cable diameters will also produce different evolutionary mechanisms and failure mechanisms under load-fire coupling. Currently, the assessment of the mechanical properties of cables after fire is inaccurate. Therefore, it is necessary to conduct research on the catastrophic conditions of multi-diameter cables, especially large-diameter cables, under load-fire coupling, and to establish a multi-size cable load-fire coupling monitoring and testing system. The establishment of this testing system mainly involves the following issues: 1. Currently, there is a lack of systematic and mature experimental methods in the full-process load-fire coupling test research of large-diameter cables. Conventional experimental methods are usually limited by the cable diameter. For small-diameter cables, it is impossible to realistically simulate the fire temperature field of the cable; therefore, studying the thermo-coupling process of large-diameter cables is more meaningful. For large-diameter cables, the loads required during the test are enormous, sometimes reaching tens of thousands of tons. Existing experimental equipment cannot meet such load requirements, and even if it could, it would pose significant safety risks.

[0004] 2. Currently, load-fire coupled testing devices for cables are rare, and there are no relevant design specifications. Existing testing devices generally have significant limitations. The equipment used to apply loads to cables is usually not heat-resistant, and high-temperature furnaces capable of applying fire conditions to cables lack corresponding loading equipment. Therefore, it is difficult to achieve load-fire coupled testing.

[0005] 3. Designing and manufacturing relevant loading equipment based on existing conventional test furnace bodies is more convenient, practical, and cost-effective. However, a major challenge is how to confine an insulated space within the conventional test furnace to allow only the cables to be heated. This requires the insulated space to be connected to the conventional test furnace's flame and exhaust systems while ensuring that the loading equipment is not located inside the heated space.

[0006] 4. In conventional testing methods, the cable anchorage zone has a transition section with varying diameter, which leads to stress concentration. This makes it difficult to accurately reflect the cable's mechanical properties, resulting in distorted results for the failure area. While lengthening the main cable model can alleviate this issue, it does not meet the testing requirements.

[0007] Therefore, based on the above problems, it is necessary to propose a new test method that overcomes the stress concentration problem in the anchorage zone, satisfies the accuracy of physical simulation of temperature field in large-diameter cable fires, and ensures safety during the thermal coupling process of large-diameter cables; at the same time, it is also applicable to the load-fire test coupling system device for bridge multi-diameter cables in conventional test open-hearth furnaces. Summary of the Invention

[0008] This invention provides a small-load alternative device and method for fire-bearing tests of large-tonnage cables. It can study the effects of different cable diameters, loads, constraints, fires, fire protection, and fire exposure time on the mechanical properties of cables. It can replace the thermo-mechanical coupling process of full-size real cable stress with small-tonnage loading.

[0009] The technical solution adopted by this invention to solve its technical problem is: a small-load alternative device suitable for large-tonnage cable-borne fire tests, including a self-balancing cable stress loading system, a cable model, an adaptive open-hearth furnace insulation and smoke exhaust system, and a multi-dimensional data monitoring system, wherein: The self-balancing cable stress loading system is installed inside a horizontal test furnace. The self-balancing cable stress loading system includes a cable translational self-balancing reaction frame, a transmission anchoring subsystem, and a fixed anchoring subsystem. The main body of the cable translational self-balancing reaction frame consists of two steel box columns. Each of the two steel box columns is equipped with a pressure-bearing guide cylinder in the middle. The transmission anchoring subsystem is installed in one pressure-bearing guide cylinder, and the fixed anchoring subsystem is installed in the other pressure-bearing guide cylinder. One end of the cable model is connected to the transmission anchoring subsystem via a transmission anchor, and the other end is connected to the fixed anchoring subsystem via a fixed anchor. The diameter of the test cable in the cable model can be adjusted by simply replacing the transmission anchor and the fixed anchor with different diameters. The cable model adopts an alternative model that can reflect the actual cable thermal coupling process. The alternative model adopts a combination arrangement of stressed and unstressed steel wires. The stressed steel wires are evenly spaced within the cable cross-section, and the stressed steel wires are parallel and of equal length. The unstressed steel wires are evenly and densely filled inside the stressed steel wires, thus acting as the medium for cable heat transfer. The adaptive open-hearth furnace insulation and exhaust system includes two adaptive partition barriers and several open-hearth furnace cover plates for limiting the cable fire-receiving space inside the horizontal test furnace. The two adaptive partition barriers are set inside the cable translational self-balancing reaction frame, and their positions inside the cable translational self-balancing reaction frame can be adjusted according to the required fire-receiving space size. Several open-hearth furnace cover plates are placed over the horizontal test furnace and the two adaptive partition barriers to form a sealed cable fire-receiving space. The multi-data monitoring system integrates a displacement monitoring system, a furnace temperature monitoring system, a cable temperature monitoring system, a cable strain monitoring system, a cable axial load monitoring system, and a furnace image acquisition system. It simultaneously monitors and acquires multiple parameters, including displacement, furnace temperature, cable temperature, cable strain, cable load, and furnace images.

[0010] A crossbeam is installed above the two steel box columns, and an anti-tilting support is installed below the two steel box columns. The installation positions of the two steel box columns at the crossbeam and the anti-tilting support are adjustable, so the distance between the two steel box columns is adjustable. The main body of the transmission anchoring subsystem is a power transmission rod. One end of the power transmission rod is connected to the cable model through a replaceable transmission anchor, and the other end of the power transmission rod passes horizontally through the pressure-bearing guide cylinder of the adjacent steel box column and extends to the external environment. The main body of the fixed anchoring subsystem is a fixed force bar. One end of the fixed force bar is connected to the cable model through a replaceable fixed anchor, and the other end of the fixed force bar passes horizontally through the pressure-bearing guide cylinder of the adjacent steel box column and extends to the external environment. The distance between the transmission anchor near the transmission anchoring subsystem and the pressure-bearing guide cylinder connected to the same transmission anchoring subsystem is the deformation stroke of the cable model; the transmission anchor near the transmission anchoring subsystem moves horizontally with the transmission anchoring subsystem, and reaches the limit when the deformation stroke is zero, thus protecting the furnace body of the horizontal test furnace.

[0011] As a further preferred embodiment of the present invention, the fire-receiving space is enclosed by a horizontal test furnace, two side furnace walls, several flat furnace cover plates and two adaptive partition barriers; several burners are provided on the side of the two furnace walls away from the fire-receiving space, and several S-type thermocouples are provided on the side of the two furnace walls facing the fire-receiving space. The adaptive partition enclosure moves along the furnace wall to form fire-receiving spaces of different sizes to meet the fire-receiving requirements of different lengths or areas of the main cable. The bottom of the enclosure is reserved with a flue opening for the open furnace exhaust system, which expands in a sloping shape to form the enclosure flue. The adaptive partition enclosure has a U-shaped or inverted U-shaped opening in the middle. The opening at the bottom of the U-shaped or inverted U-shaped opening is the first opening, and the opening at the top is the second opening. The width and height of the first opening are not less than the width and height of the anti-tilting support, and the height and width of the second opening are not less than the height and diameter of the cable under the protection of the fireproof and anti-corrosion material. The adaptive partition enclosure is reinforced with square steel pipes welded to the fire-resistant side to form a ring rib. The fire-resistant side is prefabricated with fixed ribs at equal intervals. Felt-type fireproof material is passed through the fixed ribs and bonded to the enclosure steel plate with fireproof mud. The enclosure flue is also covered with felt-type fireproof material of the same thickness. The thickness of the felt-type fireproof material shall not be less than the length of the fixing ribs and the height of the side wall of the enclosure; The flue gas outlet of the open-hearth furnace exhaust system is located at the bottom of the horizontal test furnace.

[0012] As a further preferred embodiment of the present invention, the transmission anchor and the fixed anchor have the same structure, both including a variable diameter through anchor cylinder and an anchor plate. The two ends of the variable diameter through anchor cylinder are provided with internal threads of different diameters. The anchor plate and the transmission rod or the fixed rod are respectively adapted to the two ends of the variable diameter through anchor cylinder, and are provided with corresponding external threads. The variable diameter through anchor cylinder, the anchor plate, and the transmission rod, or the variable diameter through anchor cylinder, the anchor plate, and the fixed rod, are coaxially connected by variable diameter threads. The anchor plate has evenly and densely spaced holes for directly anchoring the stressed steel wires in the cable model; the two ends of the stressed steel wires are anchored with threaded nuts or with anchor heads. The cable uses parallel steel wire bundles to overcome the common stress concentration problem in the cable anchorage area; Tighten the anchor plate and the power transmission rod or the anchor plate and the fixing rod to the two ends of the variable diameter through-hole anchor tube respectively, and adjust the distance between the anchor plate and the power transmission rod, and between the anchor plate and the fixing rod to be exactly equal to the length of the anchoring zone at both ends of the steel wire, so as to ensure that the two ends of the steel wire do not shift.

[0013] A method for using a small-load alternative device suitable for fire tests involving large-tonnage cables is also provided, specifically including the following steps: Step 1: Assemble the cable translational self-balancing reaction frame; Step 2: Install a fixed anchor at one end of the fixed anchoring subsystem, and pass the other end through a pressure-bearing guide cylinder on the cable translational self-balancing reaction frame to the external environment and connect it with the fasteners; One end of the transmission anchoring subsystem is equipped with a transmission anchor, and the other end passes through another pressure-bearing guide cylinder, force application equipment, and force measuring equipment in sequence from the inside of the cable translational self-balancing reaction frame, and finally connects to the fastener. Step 3: Thread the ends of the stressed steel wires that make up the cable model. Anchor the ends of the steel wires to the transmission anchor and the fixed anchor respectively. Install several telescopic steel pressure bars between the transmission anchor and the fixed anchor. Then use several matching nuts to tighten the ends of the steel wires and apply a small amount of prestress to the steel wires. Step four: Install the cable temperature monitoring system and the cable strain monitoring system. The cable temperature monitoring system consists of several K-type thermocouples uniformly welded to the stressed steel wires in three cross-sections within the longitudinal fire-exposed space of the cable model. The K-type thermocouples are used to monitor the temperature changes of the cable cross-section during the test. The cable strain monitoring system consists of several strain gauges uniformly pasted onto the stressed steel wires in any cross-section of the cable model. The strain gauges are used to monitor the strain changes of the stressed steel wires during the tensioning process, thereby determining the overall stress condition and uniformity of the cable. Step 5: Fill the inside of the stressed steel wire with non-stressed steel wire evenly and densely to serve as a heat transfer medium for the cable, and then bind the steel wire with dense steel straps to complete the assembly of the cable model. Step 6: Anchor one end of the hoisting cable model to the fixed anchoring subsystem via a fixed anchor, and anchor the other end to the transmission anchoring subsystem via a transmission anchor. Start the force application equipment to provide pre-tension to the cable. The cable axial load monitoring system, which is part of a multi-dimensional data monitoring system installed in a horizontal test furnace, monitors the changes in cable load in real time. When the tension is sufficient, the telescopic steel bar automatically detaches, and then fireproof and corrosion-resistant materials are used to protect the cable from fire. The cable axial load monitoring system is a force measuring device and load display recorder installed in front of the force application equipment to monitor the changes in the cable axial load value. Step 7: Hoist the cable translational self-balancing reaction frame into the horizontal test furnace and install the furnace image monitoring system and displacement monitoring system. The furnace image acquisition system consists of a monitoring camera with a built-in water cooling system placed at the bottom of one side of the horizontal test furnace to monitor the appearance of the cable inside the furnace during the test. The displacement monitoring system consists of several pull-wire displacement gauges installed between the force application equipment and the force measuring equipment. The pull-wire displacement gauges are used to monitor the displacement changes at both ends of the cable during the test. Step 8: Apply fireproof material to the cable translational self-balancing reaction frame support, install the furnace temperature monitoring system inside the horizontal test furnace, and then cover the furnace with a flat furnace cover plate to form a sealed heat-insulated space where only the cable model is heated. The furnace temperature monitoring system is an S-type thermocouple installed inside the horizontal test furnace to monitor the ambient temperature of the fire-affected space. Step 9: The data acquisition instrument sends the collected cable temperature, displacement, load, and strain change signals to the processor via wired and wireless means. The processor calculates the cable strain and stress values ​​based on the displacement and load, analyzes the uniformity of cable stress, and plots the temperature, strain, and stress curves of the cable locally and as a whole, thereby identifying the cable condition. Step 10: Prepare cable models of different diameters by replacing transmission anchors and fixed anchors of different sizes. This allows for the application of different loads, constraints, fires, and fireproof materials to different cables. The cable models are then subjected to multiple tests and analyses according to different test regimes to ultimately determine the different thermo-coupling deformations of the cables under various working conditions.

[0014] By employing the above technical solutions, the present invention has the following beneficial effects compared to the prior art: 1. This invention can be used to study the thermo-coupling process of large-diameter cables, and proposes a load-bearing fire resistance test method for cable systems of long-span bridges, which can realistically and accurately simulate the fire temperature field of cables. For large-size cables, a loading mode of small-tonnage loading to replace the full-size real cable stress is proposed to meet the test requirements in an economical, safe and efficient manner.

[0015] 2. The device of the present invention can load cables in high temperature or fire environments to complete the load-fire coupling test of cables.

[0016] 3. The device of the present invention is compatible with conventional horizontal test furnace bodies, including dimensions, flame injection system, and smoke exhaust system, making it convenient, practical, and cost-effective.

[0017] 4. This invention avoids the stress concentration problem caused by the transition section of the variable diameter in conventional test methods, and truly reflects the cable disaster process, making it more realistic and reliable.

[0018] 5. This invention can study the effects of different cable diameters, loads, fires, fire protection, and fire exposure time on the mechanical properties of cables, and can replace the thermo-mechanical coupling process of full-size real cables with small-tonnage loading. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the horizontal test furnace and adaptive fireproof enclosure structure of the present invention; Figure 3 This is a schematic diagram of the cable translational self-balancing reaction frame structure of the present invention; Figure 4 This is a schematic diagram of the adaptive fireproof enclosure back-fire side structure of the present invention; Figure 5 This is a schematic diagram of the fire-resistant surface structure of the adaptive fireproof enclosure of the present invention; Figure 6 This is a schematic diagram of the variable diameter through-hole anchor cylinder structure of the present invention; Figure 7 This is a schematic diagram of the steel wire anchorage zone structure inside the anchorage of the present invention.

[0021] In the diagram: 1. Cable model; 2. Anchor plate; 3. Cable translational self-balancing reaction frame; 4. Steel box column; 5. Crossbeam; 6. Anti-tilting support; 7. Pressure-bearing guide cylinder; 8. Power transmission rod; 9. Transmission anchor; 10. Force application equipment; 11. Force measuring equipment; 12. Transmission nut; 13. Fixed force rod; 14. Fixed anchor; 15. Fixed nut; 16. Adaptive partition enclosure; 17. Open-hearth furnace cover plate; 18. Enclosure flue; 19. 20. Flue opening of open-hearth furnace exhaust system; 21. Variable diameter through-hole anchor tube; 22. Bolt; 23. Furnace wall; 24. Burner; 25. S-type thermocouple; 26. Thin steel plate; 27. Bottom enlarged end; 28. Camera space; 30. Square steel pipe; 31. Fixing rib; 32. Enclosure steel plate; 33. Enclosure side wall; 34. First opening; 35. Second opening; 36. Felt-type fireproof material; 37. Length of steel wire anchoring end; 38. Load-bearing steel wire. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0023] In the description of this invention, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of this invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of this invention. Example

[0024] This embodiment provides a preferred implementation scheme, a small-load alternative device suitable for large-tonnage cable-borne fire tests, such as... Figures 1 to 4 As shown, this device includes a self-balancing cable stress loading system, a cable model, an adaptive open-hearth furnace insulation and flue gas exhaust system, and a multi-dimensional data monitoring system, wherein: The aforementioned self-balancing cable stress loading system is installed inside a horizontal test furnace. This system includes a cable translational self-balancing reaction frame 3, a transmission anchoring subsystem, and a fixed anchoring subsystem. The main body of the cable translational self-balancing reaction frame 3 consists of two steel box columns 4. Each steel box column 4 has a pressure-bearing guide cylinder 7 installed in its middle. The transmission anchoring subsystem is installed in one pressure-bearing guide cylinder 7, and the fixed anchoring subsystem is installed in the other. A crossbeam 5 is installed above the two steel box columns 4, and anti-tilting supports 6 are installed below them. The installation positions of the two steel box columns 4 at the crossbeam 5 and anti-tilting supports 6 are adjustable, thus the distance between the two steel box columns 4 is adjustable.

[0025] Specifically, the pressure-bearing guide cylinder 7 is a steel cylinder that penetrates and is welded to the steel box column 4, through which the transmission anchoring subsystem and the fixed anchoring subsystem pass and serve as guides and limiters. The main body of the transmission anchoring subsystem is the power transmission rod 8. One end of the power transmission rod 8 is connected to the cable model 1 through a replaceable transmission anchor 9, and the other end of the power transmission rod 8 passes horizontally through the pressure-bearing guide cylinder 7 of the adjacent steel box column 4, the force application device, and the force measuring device, and is finally anchored to the transmission nut 12. The main body of the fixed anchoring subsystem is the fixed force rod 13. One end of the fixed force rod 13 is connected to the cable model 1 through a replaceable fixed anchor 14, and the other end of the fixed force rod 13 passes horizontally through the pressure-bearing guide cylinder 7 of the adjacent steel box column 4 and extends to the external environment to be anchored to the fixed nut 15.

[0026] One end of the cable model 1 is connected to the transmission anchoring subsystem via a transmission anchor 9, and the other end is connected to the fixed anchoring subsystem via a fixed anchor 14. The diameter of the test cable in the cable model 1 can be adjusted by simply changing the diameters of the transmission anchor 9 and the fixed anchor 14. The cable model 1 adopts an alternative model that reflects the actual cable thermal coupling process. The alternative model is formed by a uniform arrangement of stressed steel wires 38 and unstressed steel wires. The stressed steel wires 38 are parallel and of equal length, and the interior of the stressed steel wires 38 is uniformly and densely filled with unstressed steel wires, thus serving as the medium for cable heat transfer. In this embodiment, the stress on some steel wires in the cable model 1 is used to replace the stress on the full-size cable, and the heat transfer of the combination of stressed steel wires 38 and unstressed steel wires is used to replace the internal heat transfer of the full-size actual cable under fire conditions.

[0027] The aforementioned transmission anchor 9 and fixed anchor 14 have the same structure, both including an anchor plate 2 and a variable-diameter through-hole anchor cylinder 20. The variable-diameter through-hole anchor cylinder 20 has internal threads of different diameters at both ends. The anchor plate 2 and the transmission rod 8 or the fixed rod 13 are respectively adapted to both ends of the variable-diameter through-hole anchor cylinder 20, and are also provided with corresponding external threads. The variable-diameter through-hole anchor cylinder 20, anchor plate 2, and transmission rod 8, or the variable-diameter through-hole anchor cylinder 20, anchor plate 2, and fixed rod 13, are coaxially connected by variable-diameter threads. The anchor plate 2 has evenly and densely spaced holes for directly anchoring the stressed steel wire 38 in the cable model 1. The stressed steel wire 38 is anchored at both ends using threaded-nut anchoring or head anchoring. The cable uses parallel wire bundles to overcome the common stress concentration problem in the cable anchorage area. Tighten the anchor plate 2 and the power transmission rod 8 or the anchor plate 2 and the fixing rod 13 to the two ends of the variable diameter through-hole anchor cylinder 20 respectively. Adjust the distance between the anchor plate 2 and the power transmission rod 8 and between the anchor plate 2 and the fixing rod 13 so that they are exactly equal to the length of the anchoring area at both ends of the steel wire, thereby ensuring that the two ends of the steel wire do not shift.

[0028] The aforementioned anchor plate 2 is threadedly connected to the variable diameter through-hole anchor cylinder 20. The anchor plate 2 has evenly and densely spaced holes for directly anchoring the stressed steel wire in the cable model 1. One end of the variable diameter through-hole anchor cylinder 20 is connected to the anchor plate 2, and the other end is connected to either the transmission anchoring subsystem or the fixed anchoring subsystem. The distance between the transmission anchor 9 near the transmission anchoring subsystem and the pressure-bearing guide cylinder 7 connected to the same transmission anchoring subsystem is the deformation stroke of the cable model 1. The transmission anchor 9 near the transmission anchoring subsystem moves horizontally with the transmission anchoring subsystem, reaching the limit position when the deformation stroke is zero, thus protecting the furnace body of the horizontal test furnace. The transmission rod 8 and the fixed rod 13 are both provided with vertical holes at their outer ends facing the cable translational self-balancing reaction frame 3. The anchor plate 2 cooperates with the transmission rod 8 and the fixed rod 13 to screw the transmission rod 8 and the fixed rod 13. The aforementioned stressed steel wires 38 are parallel and of equal length, with threads at both ends, and are anchored to the anchor plate 2 by means of a thread-nut or one end of the anchor head and the other end of the anchor plate 2 by means of a thread-nut; the aforementioned non-stressed steel wires are slightly shorter than the stressed steel wires, and are evenly distributed around the stressed steel wires 38, between the anchor plate 2 of the transmission anchor 9 and the anchor plate 2 of the fixed anchor 14, and finally form a large-size parallel steel wire bundle cable.

[0029] The aforementioned adaptive open-hearth furnace insulation and flue gas system includes two adaptive partition barriers 16 and several open-hearth furnace cover plates 17 for limiting the cable-receiving space inside the horizontal test furnace. The two adaptive partition barriers 16 are installed within the cable translational self-balancing reaction frame 3, and their positions within the frame 3 can be adjusted according to the required size of the receiving space. The several open-hearth furnace cover plates 17 cover the horizontal test furnace and the two adaptive partition barriers 16, together forming a sealed cable-receiving space. A flue gas outlet 19 for the open-hearth furnace flue gas system is reserved at the bottom of the adaptive partition barriers 16, which expands in a sloping shape to form a barrier flue 18. The flue gas outlet 19 is located at the bottom of the horizontal test furnace.

[0030] The fire-receiving space described in this embodiment is enclosed by a horizontal test furnace, two side furnace walls 23, several flat furnace cover plates 17, and two adaptive partition barriers 16. Several burners 24 are installed on the side of each furnace wall 23 away from the fire-receiving space, and several S-type thermocouples 25 are installed on the side of each furnace wall 23 facing the fire-receiving space. The anti-tilting support 6 of the self-balancing cable translational reaction frame 3 is located inside the fire-receiving space and is covered with a large amount of fireproof material to form an insulated space to protect the anti-tilting support 6. The adaptive partition barrier 16 is composed of thin steel plates 26 welded to a bottom enlarged end 27; square steel pipes 30 are cross-welded to the back of the barrier steel plate 32 to provide rigidity, and fixing ribs are evenly welded on both sides to fix the flexible insulation material. The bottom enlarged end 27 is used to support the adaptive partition barrier 16 to be stably placed inside the horizontal test furnace. The adaptive partition enclosure 16 is equipped with an enclosure flue 18, which is connected to the flue outlet 19 of the open-hearth furnace exhaust system for the discharge of waste heat and exhaust gas; the adaptive partition enclosure is provided with a camera space 28 to house a monitoring camera.

[0031] Specifically, the adaptive partition enclosure 16 moves along the furnace wall to form fire-receiving spaces of different sizes, meeting the fire-receiving requirements of different lengths or areas of the main cable. Its bottom is a flue opening 19 adapted to the open-hearth furnace exhaust system, which expands in a sloping shape to form the enclosure flue 18. The adaptive partition enclosure has a U-shaped or inverted U-shaped opening in the middle. The opening at the bottom of the U-shaped or inverted U-shaped opening is the first opening 34, and the opening at the top is the second opening 35. The width and height of the first opening 34 are not less than the width and height of the anti-tilting support 6, and the height and width of the second opening 35 are not less than the height and diameter of the cable under the protection of the fireproof and anti-corrosion material, respectively. Square steel pipes 30 are welded to the unfired side of the adaptive partition enclosure to form annular rib reinforcement. Fixed ribs 31 are prefabricated at equal intervals on the fire-receiving side. Felt-type fireproof material 36 is used to pass through the fixed ribs 31 and is bonded to the enclosure steel plate 32 with fireproof mud. The enclosure flue 18 is also covered with felt-type fireproof material of the same thickness. The thickness of the felt-type fireproof material 36 is not less than the length of the fixing rib 31 and the height of the side wall 33 of the enclosure.

[0032] This implementation plan also includes a multi-dimensional data monitoring system installed in the horizontal test furnace. The multi-dimensional data monitoring system integrates a displacement monitoring system, a furnace temperature monitoring system, a cable temperature monitoring system, a cable strain monitoring system, a cable axial load monitoring system, and a furnace image acquisition system. It simultaneously monitors and acquires multiple parameters such as displacement, furnace temperature, cable temperature, cable strain, cable load, and furnace images.

[0033] This implementation scheme also provides a test method for the small-load alternative device applicable to the large-tonnage cable-borne fire test, specifically including the following steps: Step 1: Connect the crossbeam 5 and the anti-tilting support 6 to the two steel box columns 4 respectively using bolts 21, and assemble the cable translational self-balancing reaction frame 3.

[0034] Step 2: One end of the fixed anchoring subsystem is equipped with a fixed anchor 14, and the other end passes through a pressure-bearing guide cylinder 7 on the cable translational self-balancing reaction frame 3 to the external environment and is connected to the fastener; one end of the transmission anchoring subsystem is equipped with a transmission anchor 9, and the other end passes through another pressure-bearing guide cylinder 7, force application device 10, and force measuring device 11 from the inside of the cable translational self-balancing reaction frame 3, and is finally connected to the fastener.

[0035] Specifically, a fixing rod 13 is passed through a pressure-bearing guide cylinder 4. One end of the fixing rod 13 is fixed to the cable translational self-balancing reaction frame 3 with a fixing nut 15, and the other end of the fixing rod 13 is connected to a fixing anchor 14. One end of the transmission rod 8 is connected to a transmission anchor 9, and the other end of the transmission rod 8 passes sequentially from the inside of the cable translational self-balancing reaction frame 3 through the pressure-bearing guide cylinder 4, the force application device 10, and the force measuring device 11, and is finally threadedly connected to the transmission nut. The force application device 10 is a through-hole jack, and the force measuring device 11 is a through-hole pressure sensor.

[0036] Step 3: Thread the two ends of the stressed steel wire that makes up the cable model 1. Anchor the two ends of the steel wire to the transmission anchor 9 and the fixed anchor 14 respectively. Install several telescopic steel pressure rods between the transmission anchor 9 and the fixed anchor 14. Then use several matching nuts to tighten the two ends of the steel wire and apply a small amount of prestress to the steel wire.

[0037] Step four: Install the cable temperature monitoring system and the cable strain monitoring system. The cable temperature monitoring system consists of several K-type thermocouples uniformly welded to the stressed steel wires in three cross-sections within the longitudinal fire-exposed space of the cable model 1. The K-type thermocouples are used to monitor the temperature change of the cable cross-section during the test. The cable strain monitoring system consists of several strain gauges uniformly pasted onto the stressed steel wires in any cross-section of the cable model 1. The strain gauges are used to monitor the strain change of the stressed steel wires during the tensioning process, thereby determining the overall stress condition and uniformity of the cable.

[0038] Step 5: Fill the inside of the stressed steel wire with non-stressed steel wire evenly and densely to serve as a heat transfer medium for the cable, and then bind the steel wire with dense steel straps to complete the assembly of the cable model.

[0039] Step 6: One end of the hoisting cable model 1 is anchored to the fixed anchoring subsystem via the fixed anchor 14, and the other end is anchored to the transmission anchoring subsystem via the transmission anchor 9. The force application device 10 is then activated to provide pre-tension to the cable.

[0040] The cable axial load monitoring system, which is part of the multi-dimensional data monitoring system installed in the horizontal test furnace, monitors the changes in cable load in real time. When the tension is sufficient, the telescopic steel pressure bar automatically falls off, and then fireproof and corrosion-resistant materials are used to protect the cable from fire. The cable axial load monitoring system consists of a force measuring device 11 and a load display recorder installed in front of the force application device 10, which are used to monitor the changes in the axial load value of the cable.

[0041] The telescopic steel pressure bar is a long bar composed of two steel rods of appropriate length connected by threads. Both ends of the long bar have slight protrusions at their centers, allowing it to be placed in the anchor holes of the anchor plate 2 for positioning. The telescopic steel pressure bar is mainly used in the construction of the cable model 1, providing a pre-tension force to the stressed steel wires within the cable during construction. It itself bears pressure between the two anchor plates 2. The length of the telescopic steel pressure bar is adjustable; adjusting the thread length ensures that the telescopic steel pressure bar between the two anchor plates 2 is simultaneously stressed, ensuring uniform stress on the stressed steel wires. The telescopic steel pressure bar can detach after the cable is subjected to appropriate prestress by the force-applying device 10.

[0042] Step 7: Hoist the cable translational self-balancing reaction frame 3 into the horizontal test furnace and install the furnace image monitoring system and displacement monitoring system. The furnace image acquisition system is a monitoring camera with a built-in water cooling system placed at the bottom of one side of the horizontal test furnace to monitor the appearance of the cable inside the furnace during the test. The displacement monitoring system consists of several pull-wire displacement gauges installed between the force application device 10 and the force measuring device 11. The pull-wire displacement gauges are used to monitor the displacement changes at both ends of the cable during the test.

[0043] Step 8: Apply fireproof material to the cable translational self-balancing reaction frame support 3, install the furnace temperature monitoring system inside the horizontal test furnace, and then cover the furnace with the flat furnace cover plate 17 to form a sealed heat-insulated space where only the cable model 1 is heated. The furnace temperature monitoring system is an S-type thermocouple 25 installed inside the horizontal test furnace to monitor the ambient temperature of the fire-affected space.

[0044] Step nine: The data acquisition instrument sends the collected cable temperature, displacement, load, and strain change signals to the processor via wired and wireless means. The processor calculates the cable strain and stress values ​​based on the displacement and load, analyzes the uniformity of cable stress, and plots the temperature, strain, and stress curves of the cable's local and overall conditions, thereby identifying the cable's condition.

[0045] Step 10: Prepare cable models 1 of different sizes by replacing molds of different sizes, so as to apply different loads, fires, constraints, and fireproof materials to different cables. Conduct multiple tests and analyses on cable models 1 according to different test systems, and finally determine the different thermo-coupling deformations of the cables under different working conditions.

[0046] The stressed steel wires are parallel and of equal length, and are anchored to the anchor plate 2 by threading both ends and relying on the thread-nut method, or by anchoring one end to the head and the other end to the thread-nut method.

[0047] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0048] The meaning of "and / or" as used in this application includes situations where each exists alone or both exist simultaneously.

[0049] The term "connection" as used in this application can mean a direct connection between components or an indirect connection between components through other components.

[0050] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A small-load alternative device suitable for fire tests involving large-tonnage cables, characterized in that: This includes a self-balancing cable stress loading system, a cable model, an adaptive open-hearth furnace insulation and flue gas exhaust system, and a multi-dimensional data monitoring system, among which: The self-balancing cable stress loading system is set in a horizontal test furnace. The self-balancing cable stress loading system includes a cable translational self-balancing reaction frame (3), a transmission anchoring subsystem, and a fixed anchoring subsystem. The main body of the cable translational self-balancing reaction frame (3) consists of two steel box columns (4). Each of the two steel box columns (4) is equipped with a pressure-bearing guide cylinder (7) in the middle. The transmission anchoring subsystem is installed in one pressure-bearing guide cylinder (7), and the fixed anchoring subsystem is installed in the other pressure-bearing guide cylinder (7). One end of the cable model (1) is connected to the transmission anchoring subsystem via the transmission anchor (9), and the other end is connected to the fixed anchoring subsystem via the fixed anchor (14). The diameter of the test cable in the cable model (1) can be adjusted by simply replacing the diameters of the transmission anchor (9) and the fixed anchor (14). The cable model (1) adopts an alternative model that can reflect the real cable thermal coupling process. The alternative model adopts a combination arrangement of stressed steel wires (38) and non-stressed steel wires. The stressed steel wires (38) are evenly spaced within the cable cross-section. The stressed steel wires (38) are parallel and of equal length. The non-stressed steel wires are evenly and densely filled inside the stressed steel wires (38), thus serving as the medium for cable heat transfer. The adaptive open-hearth furnace insulation and flue gas system includes two adaptive partition barriers (16) and several open-hearth furnace cover plates (17) for limiting the cable fire-receiving space inside the horizontal test furnace. The two adaptive partition barriers (16) are set inside the cable translational self-balancing reaction frame (3). The position of the two adaptive partition barriers (16) inside the cable translational self-balancing reaction frame (3) can be adjusted according to the required fire-receiving space size. Several open-hearth furnace cover plates (17) are placed over the horizontal test furnace and the two adaptive partition barriers (16) to form a sealed cable fire-receiving space. The multi-data monitoring system integrates a displacement monitoring system, a furnace temperature monitoring system, a cable temperature monitoring system, a cable strain monitoring system, a cable axial load monitoring system, and a furnace image acquisition system. It simultaneously monitors and acquires multiple parameters, including displacement, furnace temperature, cable temperature, cable strain, cable load, and furnace images. A crossbeam (5) is installed above the two steel box columns (4), and an anti-tilting support (6) is installed below the two steel box columns (4). The installation positions of the two steel box columns (4) on the crossbeam (5) and the anti-tilting support (6) are adjustable, so the distance between the two steel box columns (4) is adjustable. The main body of the transmission anchoring subsystem is the power transmission rod (8). One end of the power transmission rod (8) is connected to the cable model (1) through a replaceable transmission anchor (9). The other end of the power transmission rod (8) passes horizontally through the pressure-bearing guide cylinder (7), force application device, and force measuring device of the adjacent steel box column (4) in sequence, and is finally anchored to the transmission nut. The main body of the fixed anchoring subsystem is a fixed force bar (13). One end of the fixed force bar (13) is connected to the cable model (1) through a replaceable fixed anchor (14), and the other end of the fixed force bar (13) passes horizontally through the pressure-bearing guide cylinder (7) of the adjacent steel box column (4) and extends to the external environment. The distance between the transmission anchor (9) close to the transmission anchoring subsystem and the pressure-bearing guide cylinder (7) connected to the same transmission anchoring subsystem is the deformation stroke of the cable model (1); the transmission anchor (9) close to the transmission anchoring subsystem moves horizontally with the transmission anchoring subsystem, and reaches the limit when the deformation stroke is zero, thus protecting the furnace body of the horizontal test furnace.

2. The small-load alternative device for fire testing of large-tonnage cables according to claim 1, characterized in that: The fire-receiving space is formed by a horizontal test furnace, two furnace walls (23), several flat furnace cover plates (17) and two adaptive partition barriers (16); several burners (24) are provided on the side of the two furnace walls (23) away from the fire-receiving space, and several S-type thermocouples (25) are provided on the side of the two furnace walls (23) facing the fire-receiving space. The adaptive partition enclosure (16) moves along the furnace wall to form fire-receiving spaces of different sizes to meet the fire-receiving requirements of different lengths or areas of the main cable. The bottom of the enclosure is reserved with a flue opening (19) for the open furnace exhaust system, which expands in a sloping shape to form a flue (18). The adaptive partition enclosure has a convex or inverted convex opening in the middle. The convex or inverted convex opening at the bottom is the first opening (34), and the opening at the top is the second opening (35). The width and height of the first opening (34) are not lower than the width and height of the anti-tilting support (6), and the height and width of the second opening (35) are not lower than the height and diameter of the cable under the protection of the fireproof and anti-corrosion material. The adaptive partition enclosure is reinforced with a ring rib by welding square steel pipes (30) on the fire-resistant side. The fire-resistant side is prefabricated with fixed ribs (31) at equal intervals. Felt-type fireproof material (36) is passed through the fixed ribs (31) and bonded to the enclosure steel plate (32) with fireproof mud. The enclosure flue (18) is also covered with felt-type fireproof material of the same thickness. The thickness of the felt-type fireproof material (36) shall not be less than the length of the fixing rib (31) and the height of the side wall (33) of the enclosure; The flue outlet (19) of the open-hearth furnace exhaust system is located at the bottom of the horizontal test furnace.

3. The small-load alternative device for fire testing of large-tonnage cables according to claim 1, characterized in that: The transmission anchor (9) and the fixed anchor (14) have the same structure, both including a variable diameter through anchor cylinder (20) and an anchor plate (2). The variable diameter through anchor cylinder (20) has internal threads of different diameters at both ends. The anchor plate (2) is adapted to the two ends of the variable diameter through anchor cylinder (20) and the transmission rod (8) or the fixed rod (13) respectively. At the same time, the corresponding external threads are provided. The variable diameter through anchor cylinder (20), the anchor plate (2), and the transmission rod (8) or the variable diameter through anchor cylinder (20), the anchor plate (2), and the fixed rod (13) are connected by coaxial variable diameter threads. The anchor plate (2) has uniform and densely spaced holes for directly anchoring the stressed steel wire (38) in the cable model (1); the stressed steel wire (38) is anchored at both ends with threaded nuts or head anchors. The cable uses parallel steel wire bundles to overcome the common stress concentration problem in the cable anchorage area; Tighten the anchor plate (2) and the power transmission rod (8) or the anchor plate (2) and the fixing rod (13) to the two ends of the variable diameter through-hole anchor cylinder (20) respectively. Adjust the distance between the anchor plate (2) and the power transmission rod (8) and between the anchor plate (2) and the fixing rod (13) to be exactly equal to the length of the anchoring area at both ends of the steel wire, so as to ensure that the two ends of the steel wire do not shift.

4. A method using the small-load alternative device for large-tonnage cable-borne fire tests as described in any one of claims 1 to 3, characterized in that, Specifically, the following steps are included: Step 1: Assemble the cable translational self-balancing reaction frame (3). Step 2: Install a fixed anchor (14) at one end of the fixed anchoring subsystem, and pass the other end through a pressure-bearing guide cylinder (7) on the cable translational self-balancing reaction frame (3) to the external environment and connect with fasteners; One end of the transmission anchoring subsystem is equipped with a transmission anchor (9), and the other end passes through another pressure-bearing guide cylinder (7), force application device (10), and force measuring device (11) from the inside of the cable translational self-balancing reaction frame (3), and finally connects to the fastener; Step 3: Thread the two ends of the stressed steel wire that makes up the cable model (1), and anchor the two ends of the steel wire to the transmission anchor (9) and the fixed anchor (14) respectively. Install several telescopic steel pressure rods between the transmission anchor (9) and the fixed anchor (14), and then use several matching nuts to tighten the two ends of the steel wire to apply a small amount of prestress to the steel wire. Step 4: Install the cable temperature monitoring system and the cable strain monitoring system. The cable temperature monitoring system consists of several K-type thermocouples uniformly welded onto the stressed steel wires in three sections within the longitudinal fire-exposed space of the cable model (1). The K-type thermocouples are used to monitor the temperature change of the cable cross-section during the test. The cable strain monitoring system consists of several strain gauges uniformly pasted onto the stressed steel wires in any section of the cable model (1). The strain gauges are used to monitor the strain change of the stressed steel wires during the tensioning process, thereby determining the overall stress condition and uniformity of the cable. Step 5: Fill the inside of the stressed steel wire with non-stressed steel wire evenly and densely to serve as a heat transfer medium for the cable, and then bind the steel wire with dense steel straps to complete the assembly of the cable model. Step 6: Hoist the cable model (1) at one end to the fixed anchorage subsystem via the fixed anchorage (14) and at the other end to the transmission anchorage subsystem via the transmission anchorage (9). Start the force application equipment (10) to provide pre-tension to the cable. The cable axial load monitoring system installed in the multi-dimensional data monitoring system in the horizontal test furnace monitors the changes in cable load in real time. When the tension is sufficient, the telescopic steel pressure bar automatically falls off. Then, fireproof and anti-corrosion materials are used to protect the cable from fire. The cable axial load monitoring system is a force measuring device (11) and a load display recorder installed in front of the force application device (10) to monitor the changes in the cable axial load value. Step 7: Hoist the cable translational self-balancing reaction frame (3) into the horizontal test furnace and install the furnace image monitoring system and displacement monitoring system; the furnace image acquisition system is a monitoring camera with a built-in water cooling system placed at the bottom of one side of the horizontal test furnace, used to monitor the appearance of the cable in the furnace during the test; the displacement monitoring system is a number of pull-wire displacement gauges installed between the force application device (10) and the force measuring device (11), the pull-wire displacement gauges are used to monitor the displacement changes at both ends of the cable during the test; Step 8: Apply fireproof material to the cable translational self-balancing reaction frame support, install the furnace temperature monitoring system inside the horizontal test furnace and then cover the flat furnace cover plate (17) to form a closed heat-insulated space where only the cable model (1) is heated. The furnace temperature monitoring system is an S-type thermocouple (25) installed inside the horizontal test furnace to monitor the ambient temperature of the fire-affected space. Step 9: The data acquisition instrument sends the collected cable temperature, displacement, load, and strain change signals to the processor via wired and wireless means. The processor calculates the cable strain and stress values ​​based on the displacement and load, analyzes the uniformity of cable stress, and plots the temperature, strain, and stress curves of the cable locally and as a whole, thereby identifying the cable condition. Step 10: Replace the transmission anchor (9) and fixed anchor (14) of different sizes to prepare cable models (1) of different diameters, so as to apply different loads, constraints, fires, and fireproof materials to different cables. Perform multiple tests and analyses on the cable model (1) according to different test systems, and finally determine the different thermo-coupling deformations of the cable under different working conditions.

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