Self-adapting track panel telescopic device and method for end of low-medium speed maglev large-span bridge

Abstract

The present application belongs to the technical field of medium and low speed maglev track structure design, and discloses a medium and low speed maglev large-span bridge end adaptive track row expansion and contraction device and method. The device is arranged at the beam joint position of the bearing track beam corresponding to the large-span bridge structure joint, spans and overlaps between the beam ends of two adjacent bearing track beams, and is composed of a bearing structure, a modular track unit, an adjusting cushion layer structure, a connecting limiting structure and a linkage structure. The device can effectively adapt to the longitudinal expansion and contraction deformation and beam end corner of the bridge, and ensure the continuity and running smoothness of the track structure at the beam joint. Meanwhile, the device has a certain height adjusting capacity in the vertical direction to adapt to the construction error and structural deformation in the operation stage. The method covers multi-process collaborative control of bearing structure reverse positioning, adjusting cushion layer hierarchical layout, connecting limiting structure adaptive installation and modular track unit structure pre-adjustment positioning, so as to realize the balanced release of the structure assembly precision and dynamic expansion and contraction performance of the track row expansion and contraction device.

Description

Technical Field

[0001] This invention belongs to the technical field of medium- and low-speed maglev track structure design in railway tracks, and relates to an adaptive track extension device and method at the end of a medium- and low-speed maglev long-span bridge. Background Technology

[0002] Medium- and low-speed maglev transportation, employing a non-contact levitation and guided operation method, places extremely high demands on the geometric continuity and smoothness of the track. Long-span bridges, due to their large beam length and high structural flexibility, typically experience significant structural deformation under the influence of temperature changes, train loads, concrete shrinkage and creep, and foundation settlement. This deformation manifests primarily as longitudinal displacement at the beam ends, vertical deflection, and beam end rotation. When the bridge span is small, the elastic deformation capacity of the track structure itself and the adjustment capability of the fastening system can usually absorb or coordinate the deformation differences between the bridge and the track to a certain extent, ensuring the normal operation of the track structure. However, when the bridge span increases to a certain extent, the amplitude of beam temperature expansion and contraction and structural deformation significantly exceeds the allowable deformation range of the track structure. In this case, track expansion joints must be installed at the beam ends of long-span bridges to release structural deformation and ensure track continuity and operational safety.

[0003] In existing medium- and low-speed maglev projects, longitudinal track expansion and contraction are mainly achieved through track panel joints (including Type I, Type II, and Type III expansion joints). However, the design expansion and contraction capacity of these devices is limited, typically only meeting the deformation requirements of conventional bridges or ground-based lines. With the increasing application of medium- and low-speed maglev lines on long-span bridges crossing rivers and lakes, the longitudinal displacement amplitude at bridge structural joints has significantly increased. Existing track panel expansion joints have limitations in terms of expansion and contraction amount, uniformity of track joint movement, and guide rail continuity, making it difficult to fully guarantee the stability of the track structure and the smoothness of line operation.

[0004] Existing expansion joints used in railways and urban rail transit are primarily designed for wheel-rail systems, and their performance is insufficient to meet the stringent requirements of medium- and low-speed maglev systems in terms of track continuity, levitation and guidance stability, and uniform rail gap variation. Furthermore, due to significant differences between medium- and low-speed maglev systems and traditional wheel-rail systems in terms of vehicle suspension clearance, equipment interfaces, beam-rail structure, and civil engineering layout, existing wheel-rail expansion joints cannot be directly applied to the large longitudinal displacement conditions of medium- and low-speed maglev lines. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention discloses an adaptive track extension device and method for the ends of long-span medium- and low-speed maglev bridges. This device effectively adapts to the longitudinal expansion and contraction deformation of the bridge and the rotation angle at the beam ends, ensuring the continuity of the track structure and smooth operation at the beam joints. Simultaneously, it possesses a certain height adjustment capability in the vertical direction to accommodate construction errors and structural deformation during operation. Furthermore, the overall structural design of the device embodies simplification and standardization, facilitating subsequent operation, maintenance, and component replacement.

[0006] To achieve the above objectives, this invention provides an adaptive track extension device for the end of a medium-low speed maglev long-span bridge. It is installed at the beam joint corresponding to the structural joint of the long-span bridge, spanning and overlapping the ends of two adjacent beams. The device includes a cooperating load-bearing structure, modular track units, an adjusting pad structure, a connecting and limiting structure, and a linkage structure, wherein: The load-bearing structure spans between adjacent rail beams on both sides of the structural joint of a long-span bridge. Specifically, it includes a longitudinal load-bearing beam spanning both sides of the structural joint of the long-span bridge and a displacement box structure fixed on the rail beam on the movable side of the bridge. The longitudinal load-bearing beam is used to bear the load of the upper modular track unit and provide it with a longitudinal sliding interface. The displacement box structure is slidably connected to the longitudinal load-bearing beam. The load-bearing structure is used to bear the load of the upper track structure and provide a longitudinal sliding support interface to cooperate with other structures to release the longitudinal expansion and contraction deformation of the bridge. Modular track units are arranged longitudinally along the track and supported on a load-bearing structure. Adjacent modular track units are connected by a linkage structure to form a continuous linked track, ensuring the continuity and smoothness of the track. The load-bearing structure spans the structural joint and provides longitudinal sliding support. Together with the linkage structure and modular track units, it transforms the concentrated deformation at the beam end into uniform displacement between each unit, avoiding displacement concentration and realizing the uniform transmission and distribution of beam end expansion and contraction displacement among each modular track unit, ensuring the smooth operation of the maglev vehicle. The connecting limiting structure is respectively set between the modular track unit and the load-bearing structure and between the load-bearing structure and the rail beam. It includes an upper flange buckle plate set between the modular track unit and the load-bearing structure and a buckle iron structure set between the load-bearing structure and the rail beam, which are used to provide lateral, vertical and longitudinal limiting constraints. An adjustable pad structure, which is set between the load-bearing structure and the rail beam, includes a buffer pad, a height adjustment pad, and an iron pad, etc., for sliding support, height adjustment, and adaptive adjustment of beam end rotation angle. The adjustable pad structure and the load-bearing structure work together to achieve vertical height adjustment and longitudinal sliding, which can compensate for construction errors and operational deformations, enabling the track structure to adapt to complex deformations at the beam end and achieve comprehensive compensation for vertical and rotation angles.

[0007] In the above technical solution, the load-bearing structure, modular track unit, connecting and limiting structure, adjusting pad structure and linkage structure cooperate with each other in function and adapt to each other in structure, together forming an overall coordinated and structurally adapted adaptive track extension system. Each structure can be replaced or adjusted independently, achieving high adaptability to complex deformation of bridge beam ends, high smoothness of track structure and high convenience of operation and maintenance.

[0008] In the above technical solution, the load-bearing structure includes a set of longitudinal load-bearing beams working in concert and a displacement box structure located on the movable side of the bridge, wherein: The longitudinal load-bearing beam spans across both sides of the structural joint. The longitudinal load-bearing beam is a double-linked I-beam load-bearing beam, which is composed of two parallel and symmetrically arranged I-beam longitudinal load-bearing ribs along the longitudinal direction of the bridge. The upper part of the I-beam longitudinal load-bearing rib is provided with a rib slide plate for providing a longitudinal sliding interface for the modular track unit, and the lower part is provided with a transverse connecting beam for improving the overall rigidity. The I-beam longitudinal load-bearing rib and the transverse connecting beam are integrally formed to form an overall frame structure. The displacement box structure is fixedly installed on the rail beam on the movable side of the bridge. Inside, there are two parallel sliding chambers arranged along the longitudinal direction of the bridge. The sliding chambers are separated by vertical ribs to accommodate the ends of the I-shaped longitudinal bearing ribs and realize longitudinal relative sliding. The double-linked I-beam bearing beam and the displacement box structure work together to achieve longitudinal displacement release while maintaining the continuity and support stability of the track structure.

[0009] Specifically, the double-linked I-beam load-bearing beams are arranged across the structural joints of the bridge. To enhance the overall stiffness of the longitudinal load-bearing beams, transverse connecting beams are provided at the lower part of the longitudinal load-bearing ribs of the I-beams, and are integrally formed with the longitudinal load-bearing ribs of the I-beams to form an integral frame structure. It should be noted that in the part of the bridge that crosses the displacement box structure at the movable end, since the displacement box structure has vertical ribs inside, no transverse connecting beams are provided at the lower part of the longitudinal load-bearing ribs in this area. This ensures that the double-linked I-beam load-bearing beams can extend into the displacement box structure at the movable end and effectively release the longitudinal displacement caused by the expansion and contraction of the bridge.

[0010] Furthermore, the upper part of the I-shaped longitudinal bearing rib is provided with a rib slide plate, which is used to provide longitudinal sliding support and a continuous and stable force interface for the modular track unit.

[0011] Furthermore, the upper flange end of the I-shaped longitudinal bearing rib is provided with a closed limiting baffle. The closed limiting baffle is higher than the envelope interface of the lower sliding steel plate of the modular track unit in both vertical and horizontal directions, so as to prevent the modular track unit from falling off when it moves longitudinally to the end of the bearing beam.

[0012] Furthermore, on the fixed side of the bridge, the double-linked I-beam bearing beam restricts longitudinal displacement by being anchored to the lower rail bearing beam; while on the movable side of the bridge, the double-linked I-beam bearing beam can extend into the displacement box structure, and adapt to the longitudinal displacement generated at the movable end of the bridge by sliding within the displacement box structure, thereby avoiding the accumulation of large expansion and contraction displacement at the end of the expansion device, and ensuring that the spacing between the modular track unit at the end of the expansion device and the steel sleeper at the end of the adjacent rail panel remains within a reasonable range.

[0013] Specifically, the displacement box structure is fixedly installed on the movable side rail support beam of the bridge. Unlike the conventional connection method where steel sleepers are fixed to the support block and rail support platform by fasteners, the steel sleepers at the end of the adjacent rail panel of the movable side expansion device are directly welded to the displacement box structure. The displacement box structure has two parallel sliding chambers extending longitudinally along the bridge, separated by vertical ribs to enhance the vertical stiffness of the box and maintain the geometric stability of the sliding chambers. The ends of the double-linked I-beam can extend into the sliding chambers to achieve longitudinal relative sliding. At the same time, the entire box bears the vertical load of the steel sleepers at the end of the adjacent rail panel of the expansion device.

[0014] Furthermore, the side walls and internal ribs of the displacement box structure are made of thickened and reinforced plates to ensure overall strength and rigidity.

[0015] Furthermore, the sliding chamber is provided with an arc-shaped progressive ramp structure on its four sides. The arc-shaped progressive ramp is calculated using a parabolic progressive curve. The shape of the curve is determined by the requirements of the maximum longitudinal displacement of the bridge's movable end, the end size of the double-linked I-beam bearing beam, the coefficient of sliding friction, and the vertical load, so as to achieve smooth contact of the beam end when entering the sliding chamber, reduce instantaneous stress, and ensure uniform force distribution.

[0016] In the above technical solution, the modular track unit is supported on the longitudinal sliding interface above the I-shaped longitudinal bearing rib, and adjacent modular track units are connected by a linkage device to form an overall linkage structure with a cooperative constraint relationship; the modular track unit includes a short F-shaped guide rail, a special-shaped steel sleeper, and a sliding steel plate, wherein: The irregular steel sleeper has a pair of through holes symmetrically opened in the middle of its web plate, which extend longitudinally along the line. The through holes are used to pass through the linkage structure. V-shaped reinforcing ribs are also arranged obliquely around the through holes of the irregular steel sleeper to enhance local stiffness while ensuring that the movement of the linkage structure is not hindered, so as to achieve the coordination of linkage force transmission and structural stability. The short F-type guide rail is rigidly connected to the upper wing of the irregularly shaped steel sleeper via a high-strength bolt assembly. The sliding steel plate is welded to the bottom of the irregular steel sleeper and cooperates with the sliding interface on the upper part of the I-shaped longitudinal bearing rib of the bearing structure to achieve longitudinal sliding.

[0017] Specifically, the irregularly shaped steel sleeper web has a pair of symmetrical through holes extending longitudinally along the track in the middle. The axis of the through holes is parallel to the track centerline, and a linkage structure passes through the through holes. V-shaped reinforcing ribs extending obliquely are provided around the through holes. One end of the V-shaped reinforcing ribs is connected to the edge of the web hole, and the other end is connected to the upper and lower flanges of the sleeper web, thereby achieving local stiffness enhancement in the through hole area while ensuring that the movement of the linkage structure is not hindered.

[0018] Specifically, the short F-shaped guide rail is rigidly connected to the upper wing of the irregular steel sleeper through four sets of high-strength bolts, nuts and elastic anti-loosening washers.

[0019] In the above technical solution, one end of the V-shaped reinforcing rib is connected to the edge area of ​​the through hole, and the other end extends to the upper and lower flanges of the web of the irregular steel pillow, so as to form a continuous connection structure from the edge of the hole to the upper and lower flanges in the opening area of ​​the through hole.

[0020] In the above technical solution, the linkage structure includes an end tie rod, a connecting rod, a connecting rod end rotating shaft, an inner rotating shaft, a rolling bearing, and a sliding bearing, etc., wherein: An end tie rod is installed between the end sleeper and the end modular track unit of the track panel. It is used to transmit longitudinal force between the two and maintain the stability of their relative distance. The end tie rod has a rotatable threaded adjustment part in the middle of the rod body for precise adjustment of the rod body length. A connecting rod is inserted through the through hole of the shaped steel sleeper of the modular track unit. The connecting rod has round holes at both ends and the center. Rotating fittings, such as rolling bearings and sliding bearings, are installed in the round holes. An internal rotating shaft is set in the through hole of the web of the shaped steel sleeper of the modular track unit. The internal rotating shaft is fixedly connected to the shaped steel sleeper and is used to connect the circular hole at the center of the connecting rod. The connecting rod rotates relative to the internal rotating shaft through the central circular hole to form an X-shaped connecting rod unit. The connecting rod end rotating shaft is used to connect the round holes at the ends of adjacent connecting rods to form a continuous scissor-type linkage structure; The linkage structure achieves uniform displacement distribution and synchronous force transmission of multiple modular track units during longitudinal expansion and contraction through a scissor-type linkage structure, ensuring the uniformity of track gap distribution and smooth operation.

[0021] Specifically, the end tie rod device includes a rod body and an adjustment structure disposed in the middle of the rod body. The adjustment structure adopts a rotatable threaded adjustment component for adjusting the length of the end tie rod device. The rod body is thickened at the location of the adjustment structure to improve its bending load-bearing capacity.

[0022] Furthermore, the threaded adjusting component is a rotatable sleeve structure, with threaded sections of opposite direction at both ends of the rod. The threaded adjusting component engages with the threaded sections at both ends, and an anti-loosening component is provided at the threaded connection to ensure structural stability after adjustment. By rotating the threaded adjusting component, the extension length of the threaded sections at both ends is changed simultaneously, thereby achieving adjustment of the overall length of the end pull rod device.

[0023] Specifically, the web plates of the adjacent rail end steel sleepers at both ends of the telescopic device are provided with connecting holes for the end tie rod connecting components to pass through; the corresponding positions of the irregular steel sleepers of the modular track units at both ends of the telescopic device are also provided with connecting holes, and the connecting holes and the through holes on the web plates of the irregular steel sleepers of the end modular track units need to be staggered.

[0024] Specifically, the connecting rod is a steel component with circular holes at both ends and the center. Rolling bearings are installed inside the circular holes, and limiting structures are installed inside the rolling bearings to constrain the deformation range under extreme displacement conditions. Sliding bearings are installed on both sides of the circular holes at the ends of the connecting rod.

[0025] Furthermore, the connecting rods are inserted into the through holes of the irregular steel sleeper web of the modular track unit and arranged sequentially along the longitudinal direction of the track; the central circular holes of the two connecting rods are fitted into the rotating shaft inside the sleeper, and the connecting rods can rotate relative to each other around the rotating shaft to form an X-shaped connecting rod unit; the circular holes at the ends of the connecting rods are fitted into the rotating shaft at the ends of the connecting rods to realize end support and connection, so that multiple X-shaped connecting rod units are sequentially connected along the longitudinal direction of the track to form a continuous scissor-type linkage structure, so that the relative displacement of the track panels caused by the longitudinal displacement of the bridge can be evenly distributed.

[0026] Specifically, the internal rotating shaft is installed in the through hole of the web of the irregularly shaped steel sleeper of the modular track unit, and is firmly connected to the steel sleeper through clamping end plates. The end plates are inserted through both sides of the web of the steel sleeper and fixed with bolts, so that the internal rotating shaft and the steel sleeper are reliable. Through the combination of the linkage structure, the modular track unit can realize synchronous force transmission and constraint in longitudinal extension and scissor movement, while taking into account local stiffness enhancement and uniform displacement distribution, thereby improving the accuracy and safety of the overall linkage structure.

[0027] In the above technical solution, the end tie rod and displacement box structure constitute an end displacement control structure, which is used to realize the boundary constraint, displacement release and spacing control of beam end expansion and contraction.

[0028] Specifically: the double-linked I-beam bearing beam spans the bridge beam joint, with its movable end extending into a sliding chamber inside the displacement box structure. The longitudinal expansion and contraction displacement of the bridge is released through relative sliding within the chamber. The displacement box structure is fixedly mounted on the movable side of the bridge's rail bearing beam, and the steel sleepers at the ends of adjacent rail sections are rigidly connected to the displacement box structure instead of using traditional fasteners, thus forming a stable end displacement control benchmark. The end tie rod is positioned between the end steel sleepers of adjacent rail sections of the expansion joint and the irregularly shaped steel sleepers of the modular track unit at the end of the expansion joint. On one hand, the initial distance between them can be set through a threaded adjustment structure, keeping the end distance within a reasonable range. On the other hand, the end distance can be dynamically controlled by adjusting the length of the end tie rod to adapt to seasonal changes and structural deformation.

[0029] Based on the above structural combination, a collaborative working mechanism of boundary constraint, displacement release, and spacing control is formed at the end of the telescopic device. Through the above collaborative effect, the present invention can effectively control the spacing of the steel sleepers at the end of the telescopic device, avoid the concentrated accumulation of telescopic displacement at the end, and significantly improve the geometric continuity and running smoothness of the track structure. At the same time, with the help of the adjustable characteristics of the end tie rod, the end spacing can be finely controlled during the construction and operation stages, improving the structure's adaptability to environmental changes, and is especially suitable for medium and low speed maglev lines with high requirements for track continuity.

[0030] In the above technical solution, the connecting and limiting structure is used to realize the constrained connection between the modular track unit, the load-bearing structure and the rail beam, and to provide lateral, vertical and longitudinal limiting constraints. The connecting and limiting structure includes a fastening plate on the upper edge of the longitudinal beam, a fixed end fastening iron and a movable end fastening iron, etc., wherein: The upper flange buckle plate is fixedly connected to the lower flange of the irregular steel sleeper of the modular track unit and clamped to the upper flange of the I-shaped longitudinal bearing rib of the bearing structure to form a pressing state, thereby realizing the coordinated function of sliding and limiting. The fastening structure includes a fixed end fastening iron set on the rail bearing beam on the fixed side of the bridge and a movable end fastening iron set on the rail bearing beam on the movable side of the bridge. The fixed end fastening iron and the movable end fastening iron are respectively fastened to the outer side of the lower flange of the I-shaped longitudinal bearing rib to provide lateral restraint. A high-friction anti-slip pad is installed on the inside of the fixed end buckle to provide stable constraint on the longitudinal load-bearing ribs of the I-beam. The inner sliding plate of the buckle is located inside the movable end buckle and is used to provide lateral and vertical limits while allowing the longitudinal bearing ribs of the I-shaped structure to slide relative to each other in the longitudinal direction, so as to achieve the coordination of limiting and displacement release.

[0031] Specifically, the upper flange of the I-shaped longitudinal bearing rib is provided with an upper flange buckle plate, which is fixedly connected to the lower flange of the irregular steel sleeper and has an overall bent structure. The upper flange buckle plate clamps and connects the modular track unit with the upper flange of the I-shaped longitudinal bearing rib by applying a pre-tightening force, so that the two form a compressed state at the contact interface, eliminating structural gaps and thus avoiding unevenness during train operation.

[0032] Furthermore, a lubricating coating is applied to the contact surface between the upper flange buckle plate and the I-shaped longitudinal bearing rib. While ensuring clamping connection and limiting constraint, the frictional resistance of the contact interface is reduced, enabling the modular track unit to slide relative to the longitudinal bearing rib of the I-shaped rib, thus realizing the innovative function of sliding and limiting.

[0033] Specifically, both the fixed-end fastener and the movable-end fastener are L-shaped fastening structures, fastened to the outer side of the lower flange of the I-shaped longitudinal bearing rib, to provide lateral limiting constraint for the I-shaped bearing beam; the fixed-end fastener is arranged on the fixed side of the bridge, and the movable-end fastener is arranged on the movable side of the bridge.

[0034] Furthermore, the fixed end fastener and the movable end fastener are fixed to the rail beam by anchor bolts. The rail beam has a pre-embedded sleeve and anchor holes. The anchor bolts pass through the fastener structure and are screwed into the sleeve, thereby achieving a reliable anchoring connection between the fastener structure and the rail beam and ensuring structural stability.

[0035] Furthermore, both the fixed-end fastener and the movable-end fastener have interface components on their inner sides that contact the lower flange of the I-shaped longitudinal bearing rib; wherein, the fixed-end fastener has a high-friction anti-slip pad on its inner side to form a stable constraint on the I-shaped longitudinal bearing rib; the movable-end fastener has an inner sliding plate on its inner side, which provides lateral and vertical restraint on the I-shaped longitudinal bearing rib while allowing it to slide relative to the longitudinal direction of the bridge to accommodate the longitudinal expansion and contraction deformation of the bridge.

[0036] In the above technical solution, the adjusting pad structure is set between the load-bearing structure and the rail beam to realize the adaptive functions such as longitudinal sliding support, vertical height adjustment and beam end rotation of the modular track unit. The adjusting pad structure includes buffer pads, height adjustment pads and iron pads, etc. The components work together to form an adaptive functional system integrating sliding, buffering, height adjustment and load bearing. The adjusting pad structure on the fixed side of the bridge and the moving side of the bridge are composed of different structures.

[0037] Specifically, a buffer pad, a height adjustment pad, and an iron pad are sequentially arranged from top to bottom between the fixed-side I-beam bearing beam and the rail bearing beam of the bridge; a beam slide plate, a buffer pad, a height adjustment pad, and an iron pad are sequentially arranged from top to bottom between the movable-side I-beam bearing beam and the rail bearing beam of the bridge; the adjusting pad structure, through the superposition and partitioning of different functional layers, synergistically achieves the composite functions of longitudinal sliding, vibration buffering, vertical height adjustment, and load bearing.

[0038] In the above technical solution, the linkage structure includes an end tie rod, a connecting rod, a connecting rod end rotating shaft, an inner rotating shaft, a rolling bearing, and a sliding bearing, etc., wherein: An end tie rod is installed between the end sleeper and the end modular track unit of the track panel. It is used to transmit longitudinal force between the two and maintain the stability of their relative distance. The end tie rod has a rotatable threaded adjustment part in the middle of the rod body for precise adjustment of the rod body length. A connecting rod is inserted through the through hole of the shaped steel sleeper of the modular track unit. The connecting rod has round holes at both ends and the center. Rotating fittings, such as rolling bearings and sliding bearings, are installed in the round holes. An internal rotating shaft is set in the through hole of the web of the shaped steel sleeper of the modular track unit. The internal rotating shaft is fixedly connected to the shaped steel sleeper and is used to connect the circular hole at the center of the connecting rod. The connecting rod rotates relative to the internal rotating shaft through the central circular hole to form an X-shaped connecting rod unit. The connecting rod end rotating shaft is used to connect the round holes at the ends of adjacent connecting rods to form a continuous scissor-type linkage structure; The linkage structure achieves uniform displacement distribution and synchronous force transmission of multiple modular track units during longitudinal expansion and contraction through a scissor-type linkage structure, ensuring the uniformity of track gap distribution and smooth operation.

[0039] Specifically, the end tie rod device includes a rod body and an adjustment structure disposed in the middle of the rod body. The adjustment structure adopts a rotatable threaded adjustment component for adjusting the length of the end tie rod device. The rod body is thickened at the location of the adjustment structure to improve its bending load-bearing capacity.

[0040] Furthermore, the threaded adjusting component is a rotatable sleeve structure, with threaded sections of opposite direction at both ends of the rod. The threaded adjusting component engages with the threaded sections at both ends, and an anti-loosening component is provided at the threaded connection to ensure structural stability after adjustment. By rotating the threaded adjusting component, the extension length of the threaded sections at both ends is changed simultaneously, thereby achieving adjustment of the overall length of the end pull rod device.

[0041] Specifically, the web plates of the adjacent rail end steel sleepers at both ends of the telescopic device are provided with connecting holes for the end tie rod connecting components to pass through; the corresponding positions of the irregular steel sleepers of the modular track units at both ends of the telescopic device are also provided with connecting holes, and the connecting holes and the through holes on the web plates of the irregular steel sleepers of the end modular track units need to be staggered.

[0042] Specifically, the connecting rod is a steel component with circular holes at both ends and the center. Rolling bearings are installed inside the circular holes, and limiting structures are installed inside the rolling bearings to constrain the deformation range under extreme displacement conditions. Sliding bearings are installed on both sides of the circular holes at the ends of the connecting rod.

[0043] Furthermore, the connecting rods are inserted into the through holes of the irregular steel sleeper web of the modular track unit and arranged sequentially along the longitudinal direction of the track; the central circular holes of the two connecting rods are fitted into the rotating shaft inside the sleeper, and the connecting rods can rotate relative to each other around the rotating shaft to form an X-shaped connecting rod unit; the circular holes at the ends of the connecting rods are fitted into the rotating shaft at the ends of the connecting rods to realize end support and connection, so that multiple X-shaped connecting rod units are sequentially connected along the longitudinal direction of the track to form a continuous scissor-type linkage structure, so that the relative displacement of the track panels caused by the longitudinal displacement of the bridge can be evenly distributed.

[0044] Specifically, the internal rotating shaft is installed in the through hole of the web of the irregularly shaped steel sleeper of the modular track unit, and is firmly connected to the steel sleeper through clamping end plates. The end plates are inserted through both sides of the web of the steel sleeper and fixed with bolts, so that the internal rotating shaft and the steel sleeper are reliable. Through the combination of the linkage structure, the modular track unit can realize synchronous force transmission and constraint in longitudinal extension and scissor movement, while taking into account local stiffness enhancement and uniform displacement distribution, thereby improving the accuracy and safety of the overall linkage structure.

[0045] The second objective of this invention is to provide a construction and installation method for an adaptive track expansion joint at the end of a medium-low speed maglev long-span bridge, comprising the following steps: S1. Elevation control and pre-positioning of load-bearing structure The absolute design elevation of the rail surface is determined based on the longitudinal profile parameters of the track given in the construction drawings; the design and installation elevation of the double-linked I-beam load-bearing beam is calculated in reverse by combining the standard structural height of the track system; the double-linked I-beam load-bearing beam is placed in the predetermined spatial position using temporary support fixtures, and its initial positioning and locking in three-dimensional spatial orientation are completed.

[0046] S2. Reverse matching positioning of embedded parts and matching construction with civil structure Using the lower flange of the double-linked I-beam bearing beam initially positioned in step S1 as the absolute reference for construction, the theoretical three-dimensional coordinates of the pre-embedded sleeve located inside the bearing beam are reverse-calibrated to ensure that the central axis of the pre-embedded sleeve is precisely matched with the bearing beam in the longitudinal, transverse and vertical spatial dimensions. After calibration and fixing are completed, the concrete of the bearing beam is poured and cured. After the concrete has initially set and reached the design strength, a suitable civil engineering bearing foundation is formed.

[0047] S3. Adjusting the graded layout of the subgrade and coordinating leveling. After the track-bearing beams are formed and reach the preset curing strength, the layout of the adjustment layer structure and the fine-tuning of the double-linked I-beam load-bearing beams are carried out according to the longitudinal profile design elevation of the section. The specific operation steps are as follows: S301. Between the double-linked I-beam bearing beam and the rail bearing beam, iron pads, height adjustment pads and buffer pads are laid in sequence; in addition, for the moving end of the bridge, a beam slide bed is added above the above foundation pad layer.

[0048] S302. Based on the specific longitudinal profile design elevation of the fixed and movable ends of the bridge, the elevation of the double-linked I-beams at both ends is verified separately and independently. By dynamically increasing, decreasing, or changing the specifications of the height adjustment pads, the accumulated errors of the previous civil construction are eliminated, ensuring that the actual elevation of each end bearing beam accurately matches the design rail surface elevation at that point, thereby guaranteeing the absolute continuity and geometric smoothness of the longitudinal alignment of the entire line.

[0049] S4. Installation of the fastening structure Based on the position of the pre-embedded sleeve in step S2, the lower pad of the fastener is arranged accordingly; the fastener is assembled and pressed onto the lower flange of the double-linked I-beam bearing beam; then, the anchor bolt is inserted into the reserved hole of the fastener and screwed down into the pre-embedded sleeve for tightening, so as to achieve rigid anchoring between the fastener and the bearing beam. Preferably, after the fastening operation is completed, the fastener only forms vertical and lateral clamping and limiting on the double-linked I-beam load-bearing beam, and never forms a rigid connection with the load-bearing beam.

[0050] Furthermore, for the fixed end fasteners installed at the fixed end of the bridge, an anti-slip pad is fixedly installed inside the fastener before assembly to provide static friction to limit the longitudinal displacement of the bridge; for the movable end fasteners installed at the movable end of the bridge, a sliding plate is fixedly installed inside the fastener before assembly to provide a low-friction sliding interface to accommodate the longitudinal expansion and contraction displacement of the movable end of the bridge.

[0051] S5. Alignment and interface assembly of modular track unit structure In the factory manufacturing process, the modular track unit structure has been integrated and assembled. The modular track unit includes a short F-shaped guide rail, a special-shaped steel sleeper, and a sliding steel plate. At the same time, the rotating shaft inside the sleeper and the middle part of the linkage rod are pre-sleeved and assembled into the through hole cavity reserved in the steel sleeper to form a modular track unit with a built-in linkage mechanism.

[0052] For the prefabricated modular track units with built-in linkage structures, precise hoisting and interface assembly of the built-in linkage structures are carried out. The specific procedures are as follows: S501. Using lifting equipment, the modular track unit is lifted as a whole and smoothly installed onto the top surface of the double-linked I-beam load-bearing beam that has been installed in steps S1-S4. The track surface elevation and alignment are then checked. Subsequently, the connecting rods of adjacent modular track units are fixed by sleeve through the rotating shaft at the end of the connecting rod.

[0053] S502. Based on the pre-calculated changes in bridge expansion and contraction and the initial opening and closing angle of the connecting rod, the positions of the modular track units are adjusted longitudinally to align the track gaps between each modular track unit, while ensuring that the linkage structure is within the reasonable working stroke range corresponding to the design conditions.

[0054] S503. After the geometric parameters and rail gap spacing of the linkage structure meet the design standards, the modular track unit and the double-linked I-beam load-bearing beam are pre-fastened by the upper flange buckle plate.

[0055] Furthermore, the upper flange buckle plate is installed on the lower flange of the irregular steel sleeper of the modular track unit by anchor bolts. The buckling end of the upper flange buckle plate overlaps the upper flange of the longitudinal bearing rib of the double-linked I-beam bearing beam, so that the two form a compressed state at the contact interface, eliminating structural gaps and ensuring the smoothness of train operation.

[0056] Furthermore, a lubricating coating needs to be pre-applied to the contact surface between the upper flange buckle plate and the upper flange of the I-beam load-bearing beam.

[0057] S6. End tie rod installation and initial boundary setting The initial state settings for end tie rod connection and boundary conditions are implemented for the modular track unit at the end and the adjacent end sleeper of the track panel. For the end-shaped steel sleepers of the modular track unit at the end of the expansion joint and the end-shaped steel sleepers of the track panel adjacent to the expansion joint, the initial state settings of the end tie rods and boundary conditions are implemented. The specific procedures are as follows: S601. Web positioning and drilling operations Precisely position the web of the end irregular steel sleeper of the modular track unit at the end of the expansion joint and the web of the end steel sleeper of the adjacent track panel of the expansion joint. Use drilling tools to make alignment holes in the two webs to form through-type connecting holes for installing the end tie rod.

[0058] S602. Installation of end tie rods The two ends of the end tie rod are respectively inserted into the connection holes of the modular track unit and the end steel sleeper of the existing track panel. The connection between the telescopic device and the adjacent track panel structure is realized by using the rotatable threaded adjustment parts and fasteners at both ends of the end tie rod.

[0059] S603. Adjustment of initial spacing of end tie rod Based on specifications, seasonal temperature characteristics of the construction site, and the longitudinal expansion and contraction characteristics of the bridge, the theoretical initial end spacing between the modular track unit and the adjacent existing track panel was calculated. The end gap between the modular track unit and the existing track panel was dynamically adjusted by rotating the rotatable threaded adjustment component of the end tie rod. After the gap value reached the design calibration requirements, the anti-loosening nuts at each end were tightened to achieve precise control and locking of the end boundary conditions. The structural constraints of the end tie rod effectively control and limit the extreme range of the end expansion joint, while simultaneously ensuring the smooth and continuous transmission of longitudinal temperature forces between the expansion device and the adjacent track panel structure.

[0060] S7. Fine-tuning of the telescopic device track shape and position Static re-measurement was conducted on key geometric parameters such as track gauge, level, and elevation throughout the entire length of the expansion joint. Secondary corrections and system fine-tuning were performed on any nodes where the measured values ​​did not meet design requirements. After all track geometric parameters passed verification, a final torque check and anti-loosening locking were performed on all fasteners of the expansion joint, and construction debris was cleared.

[0061] This invention provides a track panel expansion joint that adapts to complex deformations at bridge beam ends, ensures continuous and smooth track operation, and facilitates maintenance through the systematic synergy of a load-bearing structure, modular track units, an adjustable pad structure, a connecting and limiting structure, and a linkage structure. Combining all the above technical solutions, the advantages and positive effects of this invention include: 1. Unified Displacement Release and Track Continuity: The longitudinal displacement is freely released through the cooperation of the longitudinal bearing beam and the displacement box structure. At the same time, the continuous linkage of the track system is ensured by the coordinated cooperation of the modular track units and the linkage structure, and the uniform transmission and distribution of beam end expansion and contraction displacement among the modular track units is realized.

[0062] 2. Multi-directional deformation self-adaptation: Relying on the vertical height adjustment function of the adjustable cushion structure, the sliding and limiting function of the limiting connection structure, and the displacement distribution function of the linkage structure, it can achieve comprehensive adaptation to longitudinal expansion and contraction deformation, beam end rotation angle and vertical deformation, and has the ability to adapt to structural deformation during construction error and operation.

[0063] 3. Stability and durability of steel sleepers: For irregularly shaped steel sleepers, a combination design of "through holes + V-shaped reinforcing ribs" is adopted. While meeting the requirements of the linkage structure layout, it effectively overcomes the strength reduction problem caused by the opening of the steel sleeper, and optimizes the local structure from the weakened area to the controlled strengthened area. This not only ensures the reliability and continuity of the linkage device operation, but also improves the overall stability and durability of the steel sleeper under complex stress conditions.

[0064] 4. Convenient integrated operation and maintenance: Each functional module has the advantages of simplified structure and high integration, which facilitates on-site installation and subsequent maintenance. Key components can be replaced independently, which facilitates later operation, maintenance and component replacement.

[0065] 5. Vertical constraint and low-resistance sliding are unified: The combination structure of "upper flange buckle plate + lubricating coating" is adopted. Under the premise of ensuring clamping connection and limiting constraint, the frictional resistance of the contact interface is effectively reduced, so that the modular track unit can slide relative to the longitudinal bearing rib of the I-shaped structure, realizing the function of sliding and limiting, and achieving the coordinated unity of vertical constraint and low-resistance sliding.

[0066] 6. Synergistic effect of boundary constraints, displacement release and spacing control: The end displacement control structure effectively controls the spacing of the steel sleepers at the ends of the expansion joint, avoiding the concentrated accumulation of expansion displacement at the ends, and significantly improving the geometric continuity and smooth operation of the track system; at the same time, with the help of the adjustable characteristics of the end tie rods, the end spacing can be finely controlled during the construction and operation stages, improving, for example, the structure's adaptability to environmental changes.

[0067] 7. Smooth operation: Through multiple measures such as uniform displacement distribution, optimized sliding interface, and adjusted pad setting, the impact and vibration of the train when passing through the beam joint area are effectively reduced, improving the smoothness of operation and ride comfort.

[0068] 8. Multi-process collaborative control: The construction and installation methods cover multi-process collaborative control means such as reverse positioning of the load-bearing structure, graded layout of the adjustment pad, adaptive installation of the connection and limiting structure, and pre-adjustment and positioning of the modular track unit structure, so as to achieve a balanced release of the structural assembly accuracy and dynamic expansion performance of the track expansion device.

[0069] In addition, the inventive step evidence for this invention is also reflected in the following important aspects: 1. From a construction perspective, this invention adopts a modular and standardized structural design, with some functional units prefabricated in the factory and quickly assembled on-site, significantly reducing the workload of complex on-site debugging. Simultaneously, by adjusting the subbase structure to provide vertical adjustability, it effectively absorbs construction errors and installation deviations, improving construction adaptability and assembly efficiency, and reducing reliance on high-precision on-site construction conditions.

[0070] 2. From an operation and maintenance perspective, the functional modules of this invention have clear boundaries and well-defined structural partitions, facilitating subsequent inspection, maintenance, and partial replacement. When local components are damaged, segmented disassembly and targeted repairs can be performed, avoiding the high costs and long downtime caused by overall dismantling. This significantly reduces the total lifecycle operation and maintenance costs and improves the reliability and maintainability of the line operation. Attached Figure Description

[0071] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure; Figure 1 This is a schematic elevation view of the adaptive track extension device at the end of a low-speed maglev long-span bridge in this invention. Figure 2 This is a schematic cross-sectional view of the adaptive track extension device at the end of the low-speed maglev long-span bridge in this invention along section AA. Figure 3 This is a schematic cross-sectional view of the adaptive track extension device at the end of the low-speed maglev long-span bridge in this invention along section BB. Figure 4 This is a schematic cross-sectional view of the adaptive track extension device at the end of the low-speed maglev long-span bridge in this invention along the CC section. Figure 5 This is a schematic cross-sectional view of the adaptive track extension device at the end of the low-speed maglev long-span bridge in this invention along the DD section. Figure 6 This is a schematic cross-sectional view of the adaptive track extension device at the end of the low-speed maglev long-span bridge in this invention along the EE section. Figure 7 This is a three-dimensional schematic diagram of the double-linked I-beam bearing beam in the adaptive track extension device at the end of a low-speed maglev long-span bridge in this invention. Figure 8 This is a top view schematic diagram of the double-linked I-beam bearing beam in the adaptive track extension device at the end of a low-speed maglev long-span bridge in this invention. Figure 9 This is a three-dimensional schematic diagram of the displacement box structure in the adaptive track extension device at the end of a low-speed maglev long-span bridge in this invention. Figure 10 This is a schematic diagram (not of the end) of the modular track unit in the adaptive track extension device at the end of a low-speed maglev long-span bridge in this invention. Figure 11 This is a schematic diagram of the longitudinal section (not at the end) of the adaptive track extension device at the end of a low-speed maglev long-span bridge in this invention. Figure 12This is a schematic diagram of the transverse cross-section (not at the end) of the adaptive track extension device at the end of a low-speed maglev long-span bridge in this invention. Figure 13 This is a three-dimensional schematic diagram (not at the end) of the modular track unit and scissor lift unit structure in the assembled state of the adaptive track extension device at the end of the low-speed maglev long-span bridge in this invention. Figure 14 This is a three-dimensional schematic diagram (not at the end) of the adaptive track extension device at the end of a low-speed maglev long-span bridge in this invention, showing the assembled state of the irregular steel sleepers and scissor lift unit structure. Figure 15 This is a three-dimensional schematic diagram (not of the end) of the modular track unit in the adaptive track extension device at the end of a low-speed maglev long-span bridge in this invention. Figure 16 This is a three-dimensional schematic diagram of the connecting rod in the adaptive track extension device at the end of a low-speed maglev long-span bridge in this invention. Figure 17 This is a three-dimensional schematic diagram of the inner rotating shaft, end seat, and ear plate of the adaptive track extension device at the end of a low-speed maglev long-span bridge in this invention. Figure 18 This is a diagram showing the geometric and force relationships of the scissor-type linkage structure in this invention.

[0072] In the diagram: 1. F-type guide rail; 2. Short F-type guide rail; 3. Steel sleeper at the end of adjacent rail panels; 4. Support block; 5. Rail support platform; 6. Fastener; 7. End tie rod; 8. Displacement box structure; 9. Double-linked I-beam load-bearing beam; 10. Rail support beam; 11. Special-shaped steel sleeper; 12. Sliding steel plate; 13. Rib slide plate; 14. Rubber pad; 15. Upper edge fastening plate of longitudinal beam; 16. I-beam longitudinal load-bearing rib; 17. 18. Transverse connecting beam; 19. Fixed end fastener; 20. Anchor bolt; 21. Fastener lower pad; 22. Fastener inner anti-slip pad; 23. Buffer pad; 24. Height adjustment pad; 25. Iron pad; 26. Beam slide bed plate; 27. Movable end fastener; 28. Fastener inner slide bed plate; 29. ​​End connecting rod connection hole; 30. V-shaped reinforcing rib; 31. Pillow inner rotating shaft; 32. Connecting rod; 33. Rolling bearing. Detailed Implementation

[0073] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0074] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0075] Example 1: Track expansion joint like Figures 1-17 As shown, this embodiment provides an adaptive track extension device suitable for the end of a long-span bridge of medium and low speed maglev. Specifically, it includes a load-bearing structure, a modular track unit, an adjustable pad structure, a connecting and limiting structure, and a linkage structure. The structural modules cooperate with each other in function and adapt to each other in structure, forming an adaptive integrated functional system that integrates load-bearing, sliding, limiting, adjustment, and linkage. Together, it achieves high adaptability to complex deformations at the bridge beam end, high smoothness of the track structure, and high convenience of operation and maintenance.

[0076] This expansion joint can effectively adapt to the longitudinal expansion and contraction deformation of the bridge and the rotation angle of the beam end, ensuring the continuity of the track structure and the smoothness of operation at the beam joint; at the same time, it has a certain height adjustment capability in the vertical direction to adapt to construction errors and structural deformation during the operation phase; in addition, the overall structural design of the device is simplified and standardized, which facilitates later operation, maintenance and component replacement.

[0077] Example 2: Load-bearing structure The load-bearing structure in this embodiment includes a set of double-linked I-beam load-bearing beams 9 and a displacement box structure 8 located on the movable side of the bridge.

[0078] like Figure 1 As shown, the set of double-linked I-beam bearing beams 9 spans and is set on the adjacent rail bearing beams on both sides of the structural joint of the long-span bridge, forming a continuous longitudinal bearing structure. Its main function is to bear the modular rail unit and provide longitudinal sliding support, while also being able to adapt to the longitudinal expansion and contraction deformation of the bridge.

[0079] Furthermore, the double-linked I-beam load-bearing beam 9 includes two parallel and symmetrical I-beam longitudinal load-bearing ribs 16 arranged along the longitudinal direction of the bridge. By using an I-beam shape instead of a rectangular section, structural lightweighting can be achieved while ensuring the bending stiffness and moment resistance of the web, effectively reducing the beam's self-weight.

[0080] like Figures 7-8 As shown, to enhance the overall stiffness of the longitudinal load-bearing beam, a transverse connecting beam 17 is provided at the lower part of the I-shaped longitudinal load-bearing rib 16, and is integrally formed with the I-shaped longitudinal load-bearing rib 16 to form an integral frame structure. It should be noted that in the part where the bridge moves into the displacement box structure, since the displacement box structure has vertical ribs inside, no transverse connecting beam is provided at the lower part of the I-shaped longitudinal load-bearing rib in this area. This ensures that the double-stranded I-shaped load-bearing beam can smoothly slide into the displacement box structure at the moving end and effectively release the longitudinal displacement caused by the bridge expansion and contraction.

[0081] like Figures 3-6 As shown, to ensure the smooth longitudinal sliding of the modular track unit on the I-shaped longitudinal bearing rib 16, an upper slide plate 13 is provided on the upper part of the I-shaped longitudinal bearing rib 16. The upper slide plate 13 provides a continuous and flat sliding interface for the modular track unit, while effectively reducing frictional resistance and preventing local jamming or uneven sliding.

[0082] In addition, the upper flange end of the I-shaped longitudinal load-bearing rib 16 is provided with a closed limiting baffle, the height of which is higher than the envelope interface of the lower sliding steel plate of the modular track unit both vertically and horizontally. When the modular track unit slides longitudinally along the beam end to the limit position, the closed limiting baffle can prevent the track unit from detaching from the load-bearing beam, ensuring the continuity of the track structure and operational safety.

[0083] like Figure 1 As shown, in this embodiment, the displacement box structure 8 is installed on the movable side of the bridge. The displacement box structure is fixedly mounted on the rail-bearing beam on the movable side of the bridge to provide a stable installation foundation. The end sleepers 3 of the adjacent rail panels at the ends of the bridge's movable side expansion joints are no longer fixed to the rail-bearing beam, but are directly welded to the displacement box structure 8. Through this design, the displacement box structure 8 not only provides vertical support for the last sleeper at the end of the rail panel, but also releases the longitudinal displacement of the movable end of the bridge through its internal structure.

[0084] like Figure 9 As shown, the displacement box structure 8 has two parallel sliding chambers opened along the longitudinal direction of the bridge, separated by vertical ribs. The vertical ribs enhance the overall vertical stiffness of the box and maintain the geometric stability of the sliding chambers, allowing the ends of the double-linked I-beam load-bearing beams 9 to smoothly extend into the sliding chambers and achieve longitudinal relative sliding.

[0085] Furthermore, the side walls and internal ribs of the displacement box structure are made of thickened and reinforced plates to ensure the overall structural strength and rigidity. For example... Figure 9 As shown, the four sides of the sliding chamber are equipped with an arc-shaped progressive ramp structure, which is calculated using a parabolic progressive curve. The design of the parabolic curve is determined based on the requirements of the maximum longitudinal displacement of the bridge's movable end, the end dimensions of the double-linked I-beam load-bearing beam, the coefficient of sliding friction, and the vertical load, so as to achieve smooth contact of the I-beam load-bearing beam end when entering the sliding chamber, reduce instantaneous stress, and ensure uniform stress distribution.

[0086] Example 3: Modular Track Unit like Figure 1As shown, in this embodiment, the modular track units are arranged at intervals along the longitudinal direction of the track and supported on the sliding interface above the I-shaped longitudinal bearing rib 16. Adjacent modular track units are connected by a linkage device to form an overall linkage structure with a cooperative constraint relationship, realizing the uniform transmission and distribution of beam end expansion and contraction displacement.

[0087] like Figures 3-6 As shown, each modular track unit includes a short F-shaped guide rail 2, a special-shaped steel sleeper 11, and a sliding steel plate 12. The short F-shaped guide rail 2 is rigidly connected to the upper wing of the special-shaped steel sleeper 11 by four sets of high-strength bolts, nuts, and elastic anti-loosening washers, thereby ensuring the overall rigidity and stability of the track structure.

[0088] It should be noted that the length of the short F-shaped guide rail 2 of the modular track unit located on both sides is longer than the length of the short F-shaped guide rail 2 of other modular track units. For easy distinction, in this embodiment, the short F-shaped guide rail of the modular track unit located on both sides is named F-shaped guide rail 1.

[0089] like Figure 10 As shown, the irregularly shaped steel sleeper 11 has a pair of symmetrical through holes extending longitudinally along the track in the middle of its web. The axis of the through holes is parallel to the centerline of the track. A linkage structure is installed inside the through holes for the transmission of longitudinal displacement between modular track units. V-shaped reinforcing ribs 29 are obliquely arranged around the through holes, one end of which is connected to the edge of the web hole, and the other end is connected to the upper and lower flanges of the sleeper web. This ensures that the movement of the linkage structure is not hindered, thereby achieving local stiffness enhancement in the through hole area and ensuring the stability of the irregularly shaped steel sleeper under beam end stress and linkage process.

[0090] Furthermore, a sliding steel plate 12 is welded below the irregularly shaped steel sleeper 11. This sliding steel plate 12 cooperates with the sliding interface on the upper part of the I-shaped longitudinal bearing rib 16. The setting of the sliding steel plate 12 ensures that the friction force is controllable and the sliding is smooth during the longitudinal sliding of the modular track unit. At the same time, it bears the vertical load of the modular track unit, avoids local jamming or stress concentration, thereby ensuring the continuity of the rail gap and the smoothness of the line operation.

[0091] Furthermore, the formula relating the number of modular track units to the amount of expansion and contraction is as follows: The variation in track gap spacing Δδ between adjacent modular track units should satisfy the following relationships: the number of modular track units N, and the longitudinal expansion / contraction ΔL of the bridge. The displacement distribution relationship.

[0092] Furthermore, at the maximum longitudinal expansion of the bridge Under the influence of the system, the variation in the gap between adjacent modular track units must not exceed the maximum safety value. The constraints, i.e., satisfying: .

[0093] Example 4: Irregularly Shaped Steel Pillow In existing medium- and low-speed maglev track structures, steel sleepers typically serve as load-bearing components, with their structural design primarily focused on overall strength and stiffness. When longitudinal linkage devices need to be introduced into the track panel, openings must be incorporated into the steel sleeper structure. However, these openings weaken the effective cross-section of the sleeper's web, reducing its local load-bearing capacity and making it prone to stress concentration or even local buckling in the area around the opening, thus affecting structural safety. Furthermore, traditional reinforcement methods often involve simple thickening or localized plate additions, lacking optimized design for the stress paths characteristic of the linkage devices, and failing to balance structural strength and space requirements while ensuring the normal movement of the linkage structure.

[0094] To address this issue, this embodiment provides an irregularly shaped steel sleeper structure. Symmetrical through holes extending longitudinally along the track are provided in the middle of the sleeper's web. Simultaneously, V-shaped reinforcing ribs 29 extending obliquely are provided around the through holes. One end of each V-shaped reinforcing rib 29 is connected to the edge region of the through hole, and the other end extends to the upper and lower flanges of the web, thus forming a continuous connection structure from the edge of the hole to the upper and lower flanges in the opening area.

[0095] Through the aforementioned combined design of "through holes + V-shaped reinforcing ribs" for irregularly shaped steel sleepers, a structural optimization form based on openings and directional reinforcement is formed locally in the steel sleeper. Specifically, while the through holes meet the requirements for the linkage structure to pass through, they inevitably weaken and interrupt the original force path; while the V-shaped reinforcing ribs are not simply local reinforcement components, but are arranged along the main force transmission direction of the web, redirecting and distributing the force flow that was interrupted by the openings to the upper and lower flanges, thereby reconstructing and continuing the force path. In addition, the arrangement of the V-shaped reinforcing ribs avoids the movement space of the linkage structure, ensuring that the rotation and displacement of the connecting rods within the through holes are not disturbed.

[0096] Through the above structural combination, this embodiment effectively overcomes the strength reduction problem caused by the opening of the steel sleeper while meeting the requirements of the linkage structure layout. It transforms the local structure from a weakened area to a controlled strengthened area, which not only ensures the reliability and continuity of the linkage device operation, but also improves the overall stability and durability of the steel sleeper under complex stress conditions.

[0097] Example 5: Connection Limiting Structure The connection limiting structure in this embodiment includes a longitudinal beam upper edge buckle plate 15, a fixed end buckle 18, and a movable end buckle 26, which are used to realize the constraint connection between the modular track unit, the double-linked I-beam bearing beam and the rail bearing beam, and provide lateral, vertical and longitudinal limiting functions.

[0098] like Figures 3-6As shown, the upper flange of the I-shaped longitudinal bearing rib 16 is provided with an upper flange fastener, which is fixedly connected to the lower flange of the irregular steel sleeper 11, and the whole has a bent structure. By applying pre-tightening force, the upper flange fastener clamps and connects the modular track unit with the upper flange of the I-shaped longitudinal bearing rib, so that the contact interface forms a compressed state, eliminating structural gaps and thus avoiding unevenness during train operation.

[0099] Furthermore, a lubricating coating is applied to the contact surface between the upper flange fastener and the I-shaped longitudinal load-bearing rib 16, employing a combined structure of "upper flange fastener + lubricating coating." The upper flange fastener uses pre-tensioning force to press the modular track unit against the upper flange of the I-shaped longitudinal load-bearing rib, while the lubricating coating is applied to the contact surface between the upper flange fastener and the I-shaped longitudinal load-bearing rib. This reduces the frictional resistance of the contact interface while ensuring clamping connection and limiting constraints, allowing the modular track unit to slide relative to the longitudinal load-bearing rib along the I-shaped longitudinal load-bearing rib, achieving both sliding and limiting functions. This design ensures stable support for the modular track unit while allowing longitudinal movement during bridge longitudinal expansion and contraction.

[0100] This combined structure significantly reduces longitudinal sliding resistance without reducing clamping force by directly controlling the friction characteristics of the contact interface, thereby achieving a synergistic unity between vertical clamping constraint and longitudinal low-resistance sliding. It breaks the inherent mode of clamping that restricts sliding in traditional structures and solves the functional conflict between anti-jumping and stress relief in traditional devices. It is an innovative physical characteristic coupling for maglev operating conditions.

[0101] like Figures 3-6 As shown, both the fixed end buckle 18 and the movable end buckle 26 adopt an L-shaped buckling structure and are fastened to the outer side of the lower flange of the I-shaped longitudinal bearing rib 16 to provide lateral limiting constraint for the I-shaped bearing beam. The fixed end buckle is arranged on the fixed side of the bridge, and the movable end buckle is arranged on the movable side of the bridge.

[0102] Furthermore, the fixed end buckle 18 and the movable end buckle 26 are fixed to the rail beam 10 by anchor bolts. The rail beam 10 has a pre-embedded sleeve and an anchor hole. The anchor bolts pass through the buckle structure and are screwed into the sleeve, so as to realize a reliable anchor connection between the buckle structure and the rail beam and ensure the stability of the entire structure.

[0103] Furthermore, both the fixed end clamp 18 and the movable end clamp 26 have interface components on their inner sides that contact the lower flange of the I-shaped longitudinal bearing rib 16: the fixed end clamp 18 has a high-friction anti-slip pad on its inner side to form a stable constraint on the I-shaped longitudinal bearing rib; the movable end clamp 26 has an inner sliding plate 27 on its inner side, which provides lateral and vertical limits while allowing the I-shaped longitudinal bearing rib to slide relative to each other along the longitudinal direction of the bridge, so as to adapt to the longitudinal expansion and contraction deformation of the bridge and achieve uniform force distribution and displacement release.

[0104] Example 6: Adjusting the cushion layer structure In this embodiment, the adjusting pad structure is set between the double-linked I-beam bearing beam and the rail bearing beam, forming a composite functional system integrating sliding, buffering, height adjustment and bearing, which is used to realize the adaptive functions of longitudinal sliding support, vertical height adjustment and beam end rotation of the modular track unit.

[0105] like Figures 3-6 As shown, the adjusting pad layer is composed of a beam sliding bed 25, a buffer pad 22, an adjusting pad 23, and an iron pad 24 stacked together. Each component works in concert: the beam sliding bed 25 provides a longitudinal sliding interface, allowing the track unit to move freely along the longitudinal direction of the bridge to adapt to the expansion and contraction of the beam end; the buffer pad 22 absorbs the beam end rotation and vibration, improving the smoothness of operation; the adjusting pad 23 adjusts the elevation of the I-beam longitudinal beam and compensates for construction errors, ensuring the accuracy of the track layout; the iron pad bears the load of the I-beam longitudinal beam and provides a smooth force interface, realizing stable force transmission of the structure.

[0106] Specifically, a buffer pad, a height adjustment pad, and an iron pad are arranged sequentially from top to bottom between the fixed-side I-beam bearing beam and the rail bearing beam of the bridge; a beam slide plate, a buffer pad, a height adjustment pad, and an iron pad are arranged sequentially from top to bottom between the movable-side I-beam bearing beam and the rail bearing beam of the bridge.

[0107] Example 7: Multidimensional Adaptive Compensation System This embodiment provides a multi-dimensional adaptive compensation system composed of an adjusting pad structure and a connecting limiting structure, which reconstructs and coordinates the function of the two types of structures through the combination of the two types of structures.

[0108] Specifically, in the vertical direction, the height adjustment pads are used to adjust the track elevation, simultaneously compensating for construction errors and settlement during operation; in the horizontal direction, the tie-bar structure provides limiting constraints on the double-linked I-beam load-bearing beams, ensuring the structural lateral stability; in the longitudinal direction, the movable end provides a low-friction sliding interface through the slide plate, releasing temperature stress and bridge expansion and contraction displacement; in the rotational direction, the buffer pads absorb beam end rotation through their own deformation, reducing the additional constraint effect. This achieves the decomposition and coordinated adaptation of multi-directional deformation requirements.

[0109] Furthermore, based on the aforementioned multi-dimensional compensation system, this invention proposes a functionally differentiated design for the fixed and movable ends. At the fixed end, an inner anti-slip pad is installed on the inner side of the clamp, forming a high-friction constraint interface with the lower flange of the I-beam longitudinal bearing rib, thereby providing stable constraint on the structure and serving as a control benchmark for longitudinal displacement. At the movable end, an inner sliding plate is installed on the inner side of the clamp, providing lateral and vertical restraint while forming a low-friction sliding interface, allowing the double-linked I-beam bearing beams to slide relative to each other along the bridge's longitudinal direction to accommodate bridge expansion and contraction. Simultaneously, the padding structure between the bearing beam and the rail beam also adopts a differentiated arrangement: at the fixed end, a buffer pad, a height adjustment pad, and an iron pad are sequentially installed; at the movable end, a beam-sliding sliding plate is added on top of this, thereby forming a longitudinal displacement release channel.

[0110] Through the above structural combination, this invention constructs a collaborative working mechanism of multi-dimensional compensation and end-differentiated constraints, realizing the decomposition of deformation requirements, the clarification of constraint boundaries, and the orderly control of displacement paths. Compared with traditional structures, this invention not only integrates multi-directional deformation capabilities, but also, through the reconstruction of the end-constraint system, enables the track structure to transform from passive adaptation to active control under complex working conditions, significantly improving the structural stress rationality, geometric stability, and operational smoothness, demonstrating outstanding system integration and innovation characteristics.

[0111] Example 8: Linkage Structure

[0112] The linkage structure in this embodiment consists of an end tie rod 7, a connecting rod 31, a connecting rod end rotating shaft, an inner rotating shaft 30, a rolling bearing 32, and a sliding bearing.

[0113] Specifically, the end tie rod 7 is installed between the end steel sleeper of the track panel and the shaped steel sleeper of the end modular track unit, used to transmit longitudinal force between the two and maintain a stable spacing. The end tie rod 7 includes a rod body and a rotatable threaded adjusting component located in the middle of the rod body. The rod body is thickened at the threaded adjusting component to enhance its bending load-bearing capacity. By rotating the threaded adjusting component, the extension length of the threaded sections at both ends of the rod body can be changed simultaneously, realizing precise adjustment of the overall length of the end tie rod to accommodate installation and construction errors of the modular track unit. Connection holes are respectively opened on the web plates of the adjacent end steel sleepers of the track panel and the shaped steel sleepers of the end modular track unit at both ends of the telescopic device for the end tie rod to pass through the connecting components. The connection holes of the shaped steel sleepers of the modular track unit need to be staggered at the through hole position.

[0114] like Figures 15-17As shown, the connecting rod is a steel component with circular holes at both ends and the center. Rolling bearings are installed within these holes, and each bearing has a limiting structure to constrain the deformation range under extreme displacement conditions. Sliding bearings are located on both sides of the circular hole at the end of the connecting rod to ensure smooth movement under longitudinal force. The connecting rod passes through the through holes in the web of the shaped steel sleeper of the modular track unit and is arranged sequentially along the longitudinal direction of the track. A rotating shaft is fitted into the central circular hole of the connecting rod, allowing relative rotation around the shaft to form an X-shaped connecting rod unit, i.e., a scissor unit structure. A rotating shaft is fitted into the circular hole at the end of the connecting rod, providing end support and connection. This allows multiple scissor unit structures to be sequentially connected along the longitudinal direction of the track to form a continuous scissor-type linkage structure, thereby evenly distributing the relative displacement of the track panels caused by the longitudinal displacement of the bridge to each modular track unit.

[0115] Furthermore, the internal rotating shaft is disposed within a through hole in the web of the irregularly shaped steel sleeper of the modular track unit, and is securely connected to the steel sleeper via clamping end plates. The end plates are inserted into both sides of the steel sleeper web and fixed with bolts, ensuring reliable fixation between the internal rotating shaft and the steel sleeper. Through the combination of these linkage structures, synchronous force transmission and constraint are achieved for the modular track unit under longitudinal extension and scissor movement conditions, while simultaneously considering local stiffness enhancement and uniform displacement distribution, thereby improving the stability, accuracy, and operational safety of the overall linkage structure.

[0116] Furthermore, the principles for determining the length and service angle of the connecting rod in the scissor unit structure of the linkage are as follows: The geometric and force relationships of the scissor-type linkage structure are as follows: Figure 18 As shown, let the length of the long connecting rod be L, the included angle of the scissor unit structure be α, the distance from points A and B to the vertical centerline be l, and the vertical distance between B and D be h. The following geometric relationships should be satisfied: , .

[0117] Furthermore, in the vertical load of the scissor unit structure Under action, the driving force of the connecting rod The structural angle α should satisfy a mechanical equilibrium relationship: This determines the connecting rod length and service angle range.

[0118] Example 9: End displacement control structure

[0119] In this embodiment, the end displacement control structure, which is formed by the end tie rod and the displacement box structure, is used to realize the boundary constraint, displacement release and spacing control of beam end expansion and contraction.

[0120] In existing track expansion joints, there is a general lack of effective control measures for the distribution and constraint of expansion displacement at the ends. Under the longitudinal expansion and contraction of bridges, structural displacement is often concentrated at the ends of the expansion joint. Especially under large expansion and contraction conditions, the cumulative effect of end displacement is significantly enhanced, thus forming a local geometric abrupt change zone at the ends, affecting the continuity of the track structure and the smoothness of operation. It is particularly difficult to meet the strict requirements of medium and low speed maglev systems for uniform track spacing and structural continuity.

[0121] To address this issue, the present invention provides an end displacement control structure, which is jointly constructed by an end tie rod and a displacement box structure. A double-linked I-beam spans the bridge beam joint, with its movable end extending into a sliding chamber within the displacement box structure. The longitudinal expansion and contraction displacement of the bridge is released through relative sliding within the chamber. The displacement box structure is fixedly mounted on the movable side of the bridge's rail support beam, and the steel sleepers at the ends of adjacent rail sections are rigidly connected to the displacement box structure instead of using traditional fasteners, thus forming a stable end displacement control benchmark. The end tie rod is positioned between the steel sleepers at the ends of adjacent rail sections of the expansion joint and the irregularly shaped steel sleepers of the modular track unit at the end of the expansion joint. On one hand, the initial distance between them can be set through a threaded adjustment structure, keeping the end distance within a reasonable range. On the other hand, the end distance can be dynamically controlled by adjusting the length of the end tie rod to adapt to seasonal changes and structural deformation.

[0122] Based on the above structural combination, a collaborative working mechanism of boundary constraint, displacement release, and spacing control is formed at the end of the telescopic device. Through the above collaborative effect, the present invention can effectively control the spacing of the steel sleepers at the end of the telescopic device, avoid the concentrated accumulation of telescopic displacement at the end, and significantly improve the geometric continuity and running smoothness of the track structure. At the same time, with the help of the adjustable characteristics of the end tie rod, the end spacing can be finely controlled during the construction and operation stages, improving the structure's adaptability to environmental changes, and is especially suitable for medium and low speed maglev lines with high requirements for track continuity.

[0123] Example 10: Construction and Installation Method A construction and installation method for an adaptive track expansion joint at the end of a medium-low speed maglev long-span bridge is disclosed. This method involves the coordinated control of multiple processes, including reverse positioning of the load-bearing structure, graded layout of the adjustment pad, adaptive installation of the connecting and limiting structure, and pre-adjustment and positioning of the modular track unit structure, to achieve a balanced release of the structural assembly accuracy and dynamic expansion performance of the track expansion joint. Specifically, the method includes the following steps: S1. Elevation control and pre-positioning of load-bearing structure Based on the longitudinal profile parameters of the track given in the construction drawings, the absolute design elevation of the track surface is established; combined with the standard structural height of the track system, the design installation elevation of the double-linked I-beam load-bearing beam is calculated in reverse; based on this elevation data, temporary support fixtures are used to erect the double-linked I-beam load-bearing beam to the predetermined spatial position, and its initial positioning and locking of its three-dimensional spatial posture are completed.

[0124] S2. Reverse matching positioning of embedded parts and matching construction with civil structure Using the lower flange of the double-linked I-beam bearing beam initially located in step S1 as the absolute reference for construction, the theoretical three-dimensional coordinates of the embedded sleeve of the rail bearing beam are reverse-calibrated to ensure that the central axis of the embedded sleeve is precisely matched with the bearing beam in the longitudinal, transverse and vertical spatial dimensions. After calibration and fixing are completed, the concrete of the rail bearing beam is poured and cured. After the concrete has initially set and reached the design strength, a suitable civil engineering bearing foundation is formed.

[0125] S3. Adjusting the graded layout of the subgrade and coordinating leveling. After the rail-bearing beams are formed and reach the preset curing strength, the adjustment layer is laid and the double-linked I-beam bearing beams are fine-tuned according to the longitudinal profile design elevation of the section. The specific operating steps are as follows: Between the double-linked I-beam bearing beam and the rail bearing beam, iron pads, height adjustment pads and buffer pads are laid in sequence; in addition, for the moving end of the bridge, a beam slide bed is added above the above foundation pad layer.

[0126] Furthermore, based on the specific longitudinal profile design elevations at the fixed and movable ends of the bridge, the elevations of the double-linked I-beams at both ends are verified independently. By dynamically increasing, decreasing, or replacing the specifications of the height adjustment pads, accumulated errors from previous civil construction are eliminated, ensuring that the actual elevation of each end bearing beam precisely matches the design rail surface elevation at that point, thereby guaranteeing the absolute continuity and geometric smoothness of the longitudinal alignment of the entire line.

[0127] S4. Installation of the fastening structure Based on the position of the pre-embedded sleeve mentioned in step S2, the lower pad of the fastener is arranged accordingly; the fastener is assembled and pressed onto the lower flange of the double-linked I-beam bearing beam; then, the anchor bolt is inserted into the reserved hole of the fastener and screwed downward into the pre-embedded sleeve for tightening, so as to achieve rigid anchoring between the fastener and the bearing beam.

[0128] Preferably, after the fastening operation is completed, the fastener only forms vertical and lateral clamping and limiting on the double-linked I-beam load-bearing beam, and never forms a rigid connection with the load-bearing beam.

[0129] Furthermore, for the fixed end fasteners installed at the fixed end of the bridge, an anti-slip pad is fixedly installed on the inner side of the fastener before assembly to provide static friction to limit the longitudinal displacement of the bridge; for the fasteners installed at the movable end of the bridge, an inner sliding plate is fixedly installed on the inner side of the fastener before assembly to provide a low-friction sliding interface to accommodate the longitudinal expansion and contraction displacement of the movable end of the bridge.

[0130] S5. Modular track unit alignment and interface assembly In the factory manufacturing process, the modular track unit structure has been integrated and assembled. The modular track unit includes a short F-shaped guide rail, a special-shaped steel sleeper, and a sliding steel plate. At the same time, the rotating shaft inside the sleeper and the middle part of the linkage rod are pre-sleeved and assembled into the through hole cavity reserved in the steel sleeper to form a modular track unit structure with a built-in linkage mechanism.

[0131] For the modular track unit structure with the built-in linkage mechanism, precise hoisting and interface assembly of the built-in linkage structure are carried out. The specific procedures are as follows: S501. Using lifting equipment, the modular track unit is lifted as a whole and smoothly installed onto the top surface of the double-linked I-beam load-bearing beam that has been installed in steps S1-S4. The track surface elevation and alignment are then checked. Subsequently, the connecting rods of adjacent modular track units are fixed by sleeve through the rotating shaft and sliding bearing at the end of the connecting rod.

[0132] S502. Based on the pre-calculated changes in bridge expansion and contraction (calculation method see Example 3 above) and the initial opening and closing angle of the connecting rod (calculation method see Example 8 above), the position of the modular track unit is adjusted longitudinally to align the track gap between each modular track unit, while ensuring that the linkage mechanism is within the reasonable working stroke range corresponding to the design working condition.

[0133] S503. After the geometric parameters of the linkage mechanism and the rail gap spacing meet the design standards, the modular track unit and the double-linked I-beam are pre-fastened by the upper flange buckle plate.

[0134] Furthermore, the upper flange buckle plate of the longitudinal beam is installed at the lower flange of the irregular steel sleeper of the modular track unit by anchor bolts. The buckling end of the upper flange buckle plate overlaps the upper flange of the longitudinal bearing rib of the double-linked I-beam bearing beam, so that the two form a pressed state at the contact interface, eliminating structural gaps and ensuring the smoothness of train operation.

[0135] Furthermore, a lubricating coating needs to be pre-applied to the contact surface between the upper flange plate of the longitudinal beam and the upper flange of the I-beam bearing beam.

[0136] S6. End tie rod installation and initial boundary setting For the irregularly shaped steel sleepers of the modular track unit at the end of the telescopic device and the steel sleepers at the end of the adjacent track panel of the telescopic device, the initial state settings for end tie rod connection and boundary conditions are implemented. The specific procedures are as follows: S601. Web positioning and drilling operations: Precise positioning is performed on the web plates of the end-shaped steel sleeper of the modular track unit at the end of the telescopic device, and the end-shaped steel sleeper of the adjacent track panel of the telescopic device. Drilling equipment is used to align and drill holes in the two web plates, forming through-holes for installing the end tie rods.

[0137] S602. Installation of end tie rods: The two ends of the end tie rod are respectively inserted into the connection holes of the modular track unit and the end sleepers of the existing track panel. The connection between the telescopic device and the adjacent track panel structure is achieved by using the adjusting thread structure and fastening components at both ends of the end tie rod.

[0138] S603. Adjustment of initial spacing of end tie rods: Based on the specifications, the seasonal temperature characteristics of the construction site, and the longitudinal expansion and contraction characteristics of the bridge, the theoretical initial end spacing between the modular track unit and the adjacent existing track panel was calculated. The end gap between the modular track unit and the existing track panel was dynamically adjusted by rotating the adjusting thread structure of the end tie rod. After the gap value reached the design calibration requirements, the anti-loosening nuts at each end were tightened to achieve precise control and locking of the end boundary conditions.

[0139] The structural constraints of the end tie rods effectively control and limit the extreme range of the end expansion joint, while ensuring the smooth and continuous transmission of longitudinal temperature forces between the expansion device and the adjacent track structure.

[0140] S7. Fine-tuning of the telescopic device track shape and position Static re-measurement was conducted on key geometric parameters such as track gauge, level, and elevation throughout the entire length of the expansion joint. Secondary corrections and system fine-tuning were performed on any nodes where the measured values ​​did not meet design requirements. After all track geometric parameters passed verification, a final torque check and anti-loosening locking were performed on all fasteners of the expansion joint, and construction debris was cleared.

[0141] The above description is merely a preferred embodiment of the present invention. It should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments, but can be used in various other combinations, modifications, and environments. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. An adaptive track extension device at the end of a medium-low speed maglev long-span bridge, characterized in that: Including mutual coordination and cooperation: The load-bearing structure includes longitudinal load-bearing beams spanning both sides of the structural joint of a long-span bridge and a displacement box structure fixed on a rail-bearing beam on the movable side of the bridge. The longitudinal load-bearing beams are used to bear the load of the upper modular track unit and provide a longitudinal sliding interface for it. The longitudinal load-bearing beams are composed of two I-shaped longitudinal load-bearing ribs arranged parallel and symmetrically along the longitudinal direction of the bridge. The upper part of the I-shaped longitudinal load-bearing ribs is provided with a rib slide plate, and the lower part is provided with a transverse connecting beam. The displacement box structure has two parallel sliding chambers arranged along the longitudinal direction of the bridge inside. The sliding chambers are separated by vertical ribs and are used to accommodate the ends of the I-shaped longitudinal load-bearing ribs and realize longitudinal relative sliding. Modular track units are arranged at intervals along the longitudinal direction of the track and supported on a load-bearing structure. Adjacent modular track units are connected by a linkage structure to form a continuous linkage track. The connection limiting structure includes an upper flange buckle plate disposed between the modular track unit and the load-bearing structure and a buckle iron structure disposed between the load-bearing structure and the rail beam. The adjusting pad structure is set between the load-bearing structure and the rail beam. It includes a buffer pad, a height adjustment pad, and an iron pad. The composition of the adjusting pad structure on the fixed side of the bridge and the moving side of the bridge is different. The linkage structure includes: An end tie rod is installed between the end sleeper and the end modular track unit of the track panel. The end tie rod has a rotatable threaded adjustment part in the middle of the rod body for precise adjustment of the rod length. The end tie rod and the displacement box structure work together to form an end displacement control structure for realizing boundary constraints, displacement release and spacing control of beam end expansion and contraction. A connecting rod is inserted through a hole in the irregular steel sleeper of the modular track unit. The connecting rod has round holes at both ends and the center, and a rotating fitting is installed in the round hole. An internal rotating shaft is set in the through hole of the web of the shaped steel sleeper of the modular track unit. The internal rotating shaft is fixedly connected to the shaped steel sleeper and is used to connect the circular hole at the center of the connecting rod. The connecting rod rotates relative to the internal rotating shaft through the central circular hole to form an X-shaped connecting rod unit. The connecting rod end rotating shaft is used to connect the ends of adjacent connecting rods through round holes to form a continuous scissor-type linkage structure.

2. The adaptive track extension device at the end of a medium-low speed maglev long-span bridge according to claim 1, characterized in that: The longitudinal bearing beams are in a set, and the longitudinal bearing beams are double-linked I-beam bearing beams. The upper part of the I-beam longitudinal bearing rib is provided with a rib slide plate for providing a longitudinal sliding interface for the modular track unit, and the lower part is provided with a transverse connecting beam for improving the overall rigidity.

3. The adaptive track extension device at the end of a medium-low speed maglev long-span bridge according to claim 2, characterized in that: The sliding chamber has an arc-shaped progressive ramp structure on its four sides, and the arc-shaped progressive ramp is designed with a parabolic curve.

4. The adaptive track extension device at the end of a medium-low speed maglev long-span bridge according to claim 2, characterized in that: The modular track unit is supported on the longitudinal sliding interface above the I-shaped longitudinal bearing rib, and the modular track unit includes: The irregular steel sleeper has a pair of through holes symmetrically opened in the middle of its web plate, which extend longitudinally along the line. The through holes are used to install the linkage structure. V-shaped reinforcing ribs are also provided obliquely around the through holes of the irregular steel sleeper. The short F-type guide rail is rigidly connected to the upper wing of the irregularly shaped steel sleeper via a high-strength bolt assembly. The sliding steel plate is welded to the bottom of the irregular steel pillow and cooperates with the sliding interface on the upper part of the load-bearing structure to achieve longitudinal sliding.

5. The adaptive track extension device at the end of a medium-low speed maglev long-span bridge according to claim 4, characterized in that: One end of the V-shaped reinforcing rib is connected to the edge area of ​​the through hole, and the other end extends to the upper and lower flanges of the web of the irregular steel pillow, so as to form a continuous connection structure from the edge of the hole to the upper and lower flanges in the opening area of ​​the through hole.

6. The adaptive track extension device at the end of a medium-low speed maglev long-span bridge according to claim 1, characterized in that: The connection and limiting structure is used to achieve a constrained connection between the modular track unit, the load-bearing structure, and the rail beam, and provides lateral, vertical, and longitudinal limiting constraints. The connection and limiting structure includes: The upper flange buckle plate is fixedly connected to the lower flange of the irregular steel sleeper of the modular track unit and clamped to the upper flange of the I-shaped longitudinal bearing rib of the bearing structure to form a compressed state; The fastening structure includes a fixed end fastening iron set on the rail bearing beam on the fixed side of the bridge and a movable end fastening iron set on the rail bearing beam on the movable side of the bridge. The fixed end fastening iron and the movable end fastening iron are respectively fastened to the outer side of the lower flange of the I-shaped longitudinal bearing rib to provide lateral restraint. A high-friction anti-slip pad is installed on the inside of the fixed end buckle to provide stable constraint on the longitudinal load-bearing ribs of the I-beam. The inner slide plate of the buckle is located inside the movable end buckle and is used to provide lateral and vertical limits while allowing the longitudinal bearing ribs of the I-beam to slide relative to each other longitudinally.

7. The adaptive track extension device at the end of a medium-low speed maglev long-span bridge according to claim 1, characterized in that: The fixed side of the bridge is provided with buffer pads, height adjustment pads and iron pads in sequence from top to bottom; The movable side of the bridge is provided with a beam slide plate, a buffer plate, a height adjustment plate, and an iron plate in sequence from top to bottom.

8. A construction and installation method for an adaptive track extension device at the end of a medium-low speed maglev long-span bridge as described in any one of claims 1-7, characterized in that: Includes the following steps: S1. Based on the longitudinal profile parameters of the track given in the construction drawings, determine the absolute design elevation of the rail surface; combine the standard structural height of the track system to reverse calculate the design installation elevation of the longitudinal bearing beam; use temporary support fixtures to set the longitudinal bearing beam to the predetermined spatial position, and complete the preliminary positioning and locking of its three-dimensional spatial posture. S2. Using the lower flange of the longitudinal bearing beam initially located in step S1 as the absolute reference for construction, the theoretical three-dimensional coordinates of the pre-embedded sleeve located inside the bearing beam are reverse-calibrated. After calibration and fixing are completed, the concrete for the rail bearing beam is poured and cured to form the civil engineering load-bearing foundation. S3. After the rail beam is formed and reaches the preset curing strength, adjust the layout of the pad structure and fine-tune the longitudinal bearing beam according to the longitudinal profile design elevation of the section. S4. Based on the position of the pre-embedded sleeve in step S2, install the lower pad of the fastener; assemble and fasten the fastener to the lower flange of the longitudinal bearing beam; then insert the anchor bolt into the reserved hole of the fastener and screw it downward into the pre-embedded sleeve for fastening, so as to achieve rigid anchoring between the fastener and the bearing beam. S5. Perform precise hoisting of the prefabricated modular track units with built-in linkage structure and assemble the interfaces of the built-in linkage structure; S6. Implement end tie rod connection and initial state setting of boundary conditions for the modular track unit at the end and the adjacent end sleeper of the track panel; S7. Perform static re-measurement of the track geometry parameters throughout the entire length of the telescopic device, and correct and fine-tune any nodes that do not meet the design requirements; After the inspection is passed, a final torque check and anti-loosening locking are performed on all fasteners of the telescopic device.

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