Drone-mounted high-strength steel-composite material self-monitoring beam and its construction method

Abstract

This invention provides a drone-mounted high-strength steel-composite material self-monitoring beam and its construction method. The drone-mounted high-strength steel-composite material self-monitoring beam is composed of multiple box girder segments. Each box girder segment includes a main load-bearing frame, which integrates a self-powered sensing network. A CFRP composite reinforcement layer is bonded to the outer surface of the main load-bearing frame. A hoisting interface is located at the top of the main load-bearing frame, and a mechanical compensation docking mechanism is installed at its end. A remote self-locking fastening system is deployed in conjunction with this mechanical compensation docking mechanism. This invention provides a drone-mounted high-strength steel-composite material self-monitoring beam and its construction method, enabling high-precision automated assembly of box girder segments without manual intervention. This allows for the efficient and rapid construction of emergency bridges, providing support for disaster relief efforts.

Description

Technical Field

[0001] This invention relates to the fields of bridge engineering and emergency rescue technology, and in particular to a drone-mounted high-strength steel-composite material self-monitoring beam and its construction method. Background Technology

[0002] Following natural disasters such as earthquakes, floods, and mudslides, emergency bridges are lifelines for ensuring the passage of rescue forces and the transportation of supplies. They are crucial for restoring traffic and ensuring emergency rescue, and their rapid deployment capability directly affects disaster relief efficiency. Traditional emergency bridges have heavy steel frame structures, with each segment typically exceeding 5 tons, requiring the deployment of mobile cranes with a capacity of 500 tons or more. However, traffic disruptions caused by natural disasters often prevent heavy equipment from entering, thus affecting the use of mobile cranes. Furthermore, in environments with frequent aftershocks and secondary disasters, procedures such as segment alignment and bolt tightening require operators to work at heights or manually operate inside the box girder, posing a significant risk to manual operations. Moreover, disaster areas are often without power and water after natural disasters, and traditional wired monitoring systems cannot achieve "black start" early warning at critical moments due to the lack of external power.

[0003] In recent years, with the rapid development of heavy-duty UAV technology with a payload of 1-3 tons, it has been gradually applied to emergency bridge deployment. However, its effective payload is usually 500-2000 kg, which cannot support the weight of a single segment. Moreover, UAVs are affected by turbulence and rotor downwash in the air, and their hovering accuracy is usually on the order of ±5-15 cm. This cannot achieve the millimeter-level alignment accuracy required for bolted connections, resulting in an order-of-magnitude gap between centimeter-level hovering accuracy and millimeter-level alignment accuracy. Furthermore, the existing locking mechanism still requires manual operation using a torque wrench, which still poses a risk of manual operation. There is an urgent need for a new type of bridge to at least solve some of the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a drone-mounted high-strength steel-composite material self-monitoring beam and its construction method, which not only achieves true unmanned and automated aerial docking, but also ensures control and alignment accuracy.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a drone-mounted high-strength steel-composite material self-monitoring beam, wherein the drone-mounted high-strength steel-composite material self-monitoring beam is composed of multiple box girder segments, each box girder segment includes a main load-bearing frame, the main load-bearing frame integrates a self-powered sensing network, the outer surface of the main load-bearing frame is bonded with a CFRP composite reinforcement layer, the main load-bearing frame is provided with a hoisting interface on its upper part, and a mechanical compensation docking mechanism is provided at its end, and a remote self-locking fastening system is deployed in conjunction with the mechanical compensation docking mechanism.

[0006] Preferably, the main load-bearing frame is made of high-strength steel with a yield strength ≥ 690 MPa and a single segment weight ≤ 1500 kg.

[0007] Preferably, the CFRP composite reinforcing layer is applied at the hoisting interface using a multi-directional layup structure. The layers are laid out sequentially to create a stress diffusion zone during hoisting.

[0008] Preferably, the self-powered sensing network includes a PZT piezoelectric energy harvesting module and a wireless sensor. The PZT piezoelectric energy harvesting module stores the generated electrical energy in a supercapacitor. When the voltage of the supercapacitor exceeds a preset threshold, the wireless sensor is activated to collect and transmit strain data.

[0009] Preferably, the mechanical compensation docking mechanism is disposed at the docking end of adjacent segments, including a trapezoidal shear key and its matching shear keyway. The trapezoidal shear key has an inclined meshing surface, the angle of the inclined meshing surface relative to the joint normal direction is 45° to 60°, and the key depth is 60mm to 90mm. It is used to convert the horizontal displacement deviation into sliding power along the inclined surface during the segment docking process, so as to realize mechanically assisted self-guided alignment.

[0010] Preferably, the remote self-locking fastening system includes a preload spring, a one-way self-locking wedge, and a locking pin; when the trapezoidal shear key is fully engaged, the normal pressure generated between the segments causes the preload spring to release, thereby ejecting the one-way self-locking wedge and locking it into the opposite groove, and the locking pin achieves the locking between the box girder segments.

[0011] Preferably, the wedge angle of the unidirectional self-locking wedge is less than the self-locking critical angle; multiple unidirectional self-locking wedges are arranged at the joint position of the box girder segment, and the unidirectional self-locking wedge is integrated with a remote electronically controlled unlocking actuator, which is used to receive non-destructive disassembly instructions from the ground control terminal and drive the wedge to rebound and reset.

[0012] Preferably, the box girder segment is provided with visual or laser alignment marks at the edge of the hoisting interface for identification by the UAV's visual sensor, in order to assist in achieving coarse positioning in the air.

[0013] A construction method for a UAV-mounted high-strength steel-composite material self-monitoring beam as described above includes: The drone carries the box girder segment to be installed through the hoisting interface and takes off, and is guided to the target location by RTK-GNSS; Identify the installed box girder segments and obtain their installation information; Adjust the hovering position according to the installation information of the installed box girder segments; Descends slowly at a preset speed based on the hovering position; Once the box girder segment to be installed contacts the already installed box girder segment through the mechanical compensation docking mechanism, the remote self-locking fastening system automatically locks the connection, completing the rigid connection. The drone detaches from and releases the box girder segment to be installed via the hoisting interface. Utilizing the unloading rebound vibration or mechanical triggering energy generated at the moment of detachment and release, the PZT piezoelectric energy harvesting module converts it into instantaneous electrical energy to forcibly wake up the wireless sensors, completing the first black start and self-activating the self-powered sensing network of the box girder segment to be installed, thus initiating self-powered wireless health monitoring.

[0014] Preferably, the hoisting cycle of the box girder segments to be installed is 8-12 minutes, and all segments comply with road and low-altitude air transport restrictions during transportation.

[0015] The present invention has achieved the following beneficial effects: This invention realizes the transformation of bridge beams from passive load-bearing structures to intelligent structures that are actively sensing, autonomously assembled, and self-powered for monitoring. It reduces the reliance on large lifting machinery, enabling the construction of bridges without human intervention in the splicing of box girder segments. This improves construction efficiency while reducing the risks of working at heights. Moreover, the drone-mounted high-strength steel-composite material self-monitoring beam can continuously monitor the construction and service status of the beam, facilitating subsequent bridge maintenance.

[0016] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the application.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the cross-section of the box girder segment (1) of the UAV-mounted high-strength steel-composite material self-monitoring beam described in this invention; Figure 2 This is a schematic diagram of the layout of the self-powered sensing network in the UAV-mounted high-strength steel-composite material self-monitoring beam described in this invention; Figure 3 This is a schematic diagram of the components of the remote self-locking fastening system for the UAV-mounted high-strength steel-composite material self-monitoring beam described in this invention; Figure 4 This is a schematic diagram illustrating the construction steps of the construction method for a drone-mounted high-strength steel-composite material self-monitoring beam described in this invention. Figure 5 This is a schematic diagram illustrating the application scenario of the construction method for the UAV-mounted high-strength steel-composite material self-monitoring beam described in this invention.

[0019] In the diagram, 1 represents a box girder segment; 2 represents the main load-bearing frame; 3 represents a self-powered sensing network; 4 represents a hoisting interface; 3a represents a PZT piezoelectric energy harvesting module; 3b represents a wireless sensor; c represents a preload spring; d represents a one-way self-locking wedge; and e represents a locking pin. Detailed Implementation

[0020] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0021] This invention provides a drone-mounted high-strength steel-composite material self-monitoring beam, which is composed of multiple box girder segments 1, such as... Figure 1 As shown, the box girder segment 1 includes a main load-bearing frame 2. The main load-bearing frame 2 integrates a self-powered sensing network 3. The outer surface of the main load-bearing frame 2 is pasted with a CFRP composite reinforcement layer. The main load-bearing frame 2 is provided with a hoisting interface 4 on the top and a mechanical compensation docking mechanism at the end. A remote self-locking fastening system is deployed in the mechanical compensation docking mechanism.

[0022] In the above technical solution, an emergency bridge is formed by using a drone-mounted high-strength steel-composite material self-monitoring beam, thereby realizing the construction of an emergency rescue bridge and enabling rescue operations for natural disasters. The number of box girder segments 1 is determined according to the scale of the emergency rescue bridge. The box girder segments 1 are longitudinally spliced ​​together to form a drone-mounted high-strength steel-composite material self-monitoring beam.

[0023] In the above technical solution, the length of box girder segment 1 is usually set at 3.5m, but it can also be adjusted according to actual needs.

[0024] In the above technical solution, the main load-bearing frame 2 is the core of the box girder segment 1 and is the main load-bearing structure.

[0025] In the above technical solution, the CFRP composite reinforcement layer on the outer surface of the main load-bearing frame 2 is made by bonding high-modulus carbon fiber cloth (CFRP) to the outer surface of the main load-bearing frame 2 with epoxy resin structural adhesive. The CFRP composite reinforcement layer is mainly arranged along the axial direction and tension zone of the main frame, forming a steel-composite structure with the internal steel frame. Without significantly increasing the weight, the bending stiffness and fatigue life of the beam are significantly improved.

[0026] In the above technical solution, the self-powered sensing network 3 is integrated inside the main load-bearing frame 2, which can avoid physical impact damage and environmental erosion during the drone hoisting process, ensure the performance of sensing and monitoring, and achieve real-time self-powered monitoring of the structural status even in a power outage environment.

[0027] In the above technical solution, the hoisting interface 4 is usually set according to the center of gravity of the box girder segment 1 and is located above the main load-bearing frame 2 to prevent concentrated loads during hoisting from damaging the CFRP layer.

[0028] In the above technical solution, the mechanical compensation docking mechanism is located at the end of the splicing between box girder segments 1, and can automatically correct the docking posture during the hoisting process to achieve millimeter-level auxiliary alignment.

[0029] In the above technical solution, the remote self-locking fastening system is located at the edge or inside of the docking interface. After the mechanical compensation docking mechanism completes the complete fit of the contact surfaces of the two box girder segments 1, the normal pressure between the docking surfaces triggers the release of the preload spring, driving the unidirectional self-locking wedge to engage with the opposite groove, thus fastening the corresponding two box girder segments 1 into a rigid whole. The remote self-locking fastening system achieves active mechanical response through physical triggering. Its locking state and joint preload are collected in real time by pre-embedded strain and displacement sensors and fed back to the ground control terminal wirelessly, realizing remote status monitoring and digital verification of the locking effect.

[0030] The above-mentioned transformation of bridge beams from passive load-bearing structures to intelligent structures with active sensing, autonomous assembly, and self-powered monitoring reduces reliance on large lifting machinery. This allows box girder segments 1 to form a bridge without human intervention, improving construction efficiency while reducing the risks of high-altitude operations. Furthermore, the drone-mounted high-strength steel-composite material self-monitoring beam can continuously monitor the construction and service status of the beam, facilitating subsequent bridge maintenance.

[0031] The aforementioned use of multiple box girder segments 1 allows for flexible increases or decreases in the number of segments 1 according to span requirements, enabling standardized modular production and customized assembly. It also facilitates disassembly and transportation, adapting to the maximum takeoff weight limitations of drones. By employing a combination structure of a high-strength steel main load-bearing frame 2 and an outer surface-bonded CFRP composite reinforcement layer, the weight is effectively reduced while ensuring high load-bearing capacity of the beam. This allows the assembly of box girder segments 1 to no longer rely solely on large lifting machinery, enabling easy lifting by drones. By integrating a self-powered sensing network 3 within the main load-bearing frame 2, real-time acquisition of internal strain, vibration, and damage can be achieved, facilitating bridge maintenance and ensuring the safety of bridges erected temporarily or in emergencies. Furthermore, it allows for real-time collection of structural response parameters such as strain, temperature, and damage without external power supply or wiring, enabling continuous self-monitoring of the beam's construction and service status even in remote or unmanned environments. By setting a hoisting interface 4 above the main load-bearing frame 2, it can quickly match and dock with the UAV hoisting equipment, avoiding sling slippage and center of gravity shift, simplifying the mounting operation, reducing the risk of swaying in the air, and thus improving the efficiency and safety of the hoisting operation. By setting a mechanical compensation docking mechanism at the end to absorb the horizontal, vertical and angular errors generated when the UAV hovers and positions itself, multiple box girder segments 1 can still be accurately docked under low-precision guidance, which greatly reduces the stringent requirements on the UAV flight control system, improves construction fault tolerance, ensures the precise alignment of box girder segments 1, and guarantees construction accuracy. Moreover, a remote self-locking fastening system is deployed in conjunction with the mechanical compensation docking mechanism. The mechanical locking between segments is automatically triggered by the docking normal force, and the locking status and preload data are fed back to the ground control terminal in real time through wireless sensors for closed-loop verification. This completely replaces the high-altitude manual bolt tightening or welding operation, enabling automatic locking between box girder segments 1, improving construction speed, and avoiding safety risks for construction personnel in complex terrain or high-altitude environments.

[0032] In one embodiment of the present invention, the main load-bearing frame 2 is made of high-strength steel with a yield strength ≥ 690 MPa and a single segment weight ≤ 1500 kg.

[0033] In the above technical solution, the main load-bearing frame 2 is usually made of Q690 grade high-strength structural steel, and its density is usually set to 7.85g / cm³. It can also be appropriately adjusted according to actual needs, so that the rigidity of the main load-bearing frame 2 is doubled while the plate thickness is reduced by about half, thereby reducing the weight of the box girder segment 1 by 70% to 75%, ensuring that the weight of a single box girder segment 1 is ≤1500kg, which is within the load-bearing range of the UAV.

[0034] Furthermore, the CFRP composite reinforcing layer adopts a multi-directional layup structure at the four lifting interfaces. The layers are laid out sequentially to create a stress diffusion zone during hoisting.

[0035] In the above technical solution, the CFRP composite reinforcing layer provides lateral stiffness constraint on the outer surface of the main load-bearing frame 2, solving the problem of local buckling of thin walls.

[0036] In the above technical solution, 's' indicates that the layers are symmetrically distributed with the central layer as the plane of symmetry.

[0037] In the above technical solution, the yield strength of the CFRP composite reinforcing layer is at least in the range of 2000-3000 MPa, and its density is usually 1.6 g / cm³, but it can also be adjusted according to actual needs.

[0038] In the above technical solution, the CFRP composite reinforcing layer adopts a multi-directional layup structure at the four lifting interfaces. When bonding the layers, the center layer should be the reference point, and the angles of the upper and lower layers should be completely symmetrical to eliminate residual internal stress generated during the curing process of the composite material and prevent warping or peeling of the reinforcing layer. Furthermore, in During layering, the layers are arranged longitudinally along the beam, primarily bearing the axial tensile stress generated during hoisting and improving the beam's bending stiffness. During layering, the layers are arranged in a cross pattern, specifically designed to resist the shear forces and torsional moments generated during hoisting, preventing diagonal cracks from appearing at the joint areas. During the layup process, the layers are arranged circumferentially along the transverse direction of the beam to limit the lateral deformation of the steel frame under compression and enhance local compressive stability.

[0039] The aforementioned method achieves overall weight reduction and local reinforcement of box girder segment 1 through the main load-bearing frame 2 and CFRP composite reinforcement layer. This avoids the problem of excessive weight caused by increasing the overall beam wall thickness to compensate for local stress, allowing box girder segment 1 to balance lightweighting and local reinforcement, thus enhancing its adaptability to UAV lifting methods. By using high-strength steel with a yield strength ≥690MPa to construct the main load-bearing frame 2, the weight of a single box girder segment 1 is controlled within 1500kg while meeting structural stress requirements. This allows box girder segment 1 to be compatible with the maximum lifting weight range of current industrial-grade UAVs, thereby ensuring the safe and stable completion of aerial lifting and assembly operations by the UAV. By adopting a multi-directional layered structure... The sequential bonding of the layers allows the multi-directional layered structure of the CFRP composite reinforcement layer to simultaneously withstand the combined axial tension, circumferential compression, and shear loads generated during hoisting. This disperses the concentrated force at the hoisting point to a larger area of ​​the steel frame surface, reduces the peak stress at hoisting interface 4, prevents local yielding of the high-strength steel matrix or delamination between CFRP layers, and extends the fatigue life of hoisting interface 4, thereby ensuring the structural integrity and safety of the hoisting process.

[0040] In one embodiment provided by the present invention, such as Figure 2As shown, the self-powered sensing network 3 includes a PZT piezoelectric energy harvesting module 3a and a wireless sensor 3b. The PZT piezoelectric energy harvesting module 3a stores the generated electrical energy in a supercapacitor. When the voltage of the supercapacitor exceeds a preset threshold, the wireless sensor 3b is activated to collect and transmit strain data.

[0041] In the above technical solution, the PZT piezoelectric energy harvesting module 3a uses PZT-5A piezoelectric material, and the piezoelectric constant is usually taken as 374pC / N.

[0042] In the above technical solution, the excitation frequency of the PZT piezoelectric energy harvesting module 3a ranges from 0.25 to 15 Hz, which is suitable for vehicle traffic vibration or rotor downwash airflow excitation conditions. The single piezoelectric output power is 1 to 10 mW, and the peak output voltage is 0.5 to 7.5 V.

[0043] In the above technical solution, the supercapacitor has a capacity of 0.1 to 1F, which not only has a longer cycle life, but also can adapt to extreme temperature difference environments in the wild.

[0044] In the above technical solution, the PZT piezoelectric energy harvesting module 3a is deployed in the high strain zone or vibration sensitive zone of the main load-bearing frame 2. Here, the high strain zone is, for example, the inner side of the tension flange, and the vibration sensitive zone is, for example, the center of the web.

[0045] In the above technical solution, the PZT piezoelectric energy harvesting module 3a has a high-efficiency rectifier bridge integrated at the back end, which converts the unstable AC power into DC power and inputs it into the supercapacitor for storage.

[0046] In the above technical solution, a supercapacitor and an ultra-low power voltage comparator are integrated to form an energy storage circuit. The ultra-low power voltage comparator analyzes and determines the relationship between the voltage of the supercapacitor and a preset threshold in real time. The preset threshold is a voltage threshold that is pre-set and determined, for example, 3.3V.

[0047] In the above technical solution, when the wireless sensor 3b is in deep sleep mode, the power consumption remains at the microampere level. In the early stage of construction, when the bridge is not open to traffic and there is no external power supply, the UAV performs a release action through the lifting interface 4. The mechanical impact generated when the lifting device is released and the elastic recovery vibration after the beam is unloaded form an initial strong excitation pulse. The PZT piezoelectric energy harvesting module 3a captures the energy of this initial pulse and quickly inputs DC power into the supercapacitor, causing its voltage to instantaneously exceed the preset threshold, thereby forcing the black start of the wireless sensor 3b, so that it can be autonomously activated without external power and an initial wireless wake-up command, and start continuous monitoring throughout its entire life cycle.

[0048] In the above technical solution, after the wireless sensor 3b finishes transmitting data, or when the voltage drops to a specific value, it re-enters a sleep state and waits for the next round of energy accumulation.

[0049] In the above technical solution, the self-powered sensing network 3 also provides safety warnings based on real-time strain monitoring data combined with safety warning thresholds. For example: when the strain monitoring data is less than 0.8 times the yield strain force, a green warning is issued, indicating a normal safety condition. When the strain monitoring data is not less than 0.8 times the yield strain force but less than 0.95 times the yield strain force, an orange warning is issued, indicating a safety condition requiring attention. When the strain monitoring data is not less than 0.95 times the yield strain force, a red warning is issued, indicating a dangerous safety condition.

[0050] The black start monitoring logic is realized through the self-powered sensing network 3. The PZT piezoelectric energy harvesting module 3a converts environmental vibration into electrical energy and stores it in a supercapacitor to provide a continuous and autonomous power supply, thus enabling black start capability. There is no need to lay power supply lines or replace batteries, ensuring that the monitoring can operate with the same lifespan as the beam structure.

[0051] Moreover, the wireless sensor 3b is only activated to collect and transmit strain data when the voltage of the supercapacitor exceeds a preset threshold. This avoids the wireless sensor 3b from failing to start or losing data when the energy is insufficient, minimizing average power consumption. This allows the small amount of energy collected by the PZT to sustain the operation of the sensing network for a long time, improving the reliability and maintenance-free cycle of the self-powered sensing network 3. It can also automatically match the rhythm of energy accumulation and data collection. During periods of intense vibration, such as hoisting and assembly, the PZT has a high energy collection rate, and the capacitor quickly reaches the threshold, causing the wireless sensor 3b to be activated at a high frequency. This enables intensive monitoring of strain peaks and structural transient responses. During static service, energy accumulation is slow, and the sensor activation frequency is reduced to avoid invalid data. This ensures that the sensing network always collects effective data under the premise of sufficient energy, providing reliable real-time strain feedback for construction operations such as aerial hoisting attitude adjustment and self-locking timing judgment.

[0052] In one embodiment of the present invention, the mechanical compensation docking mechanism is disposed at the docking end of adjacent segments, including a trapezoidal shear key and a matching shear keyway. The trapezoidal shear key has an inclined meshing surface, the angle of the inclined meshing surface relative to the joint normal direction is 45° to 60°, and the key depth is 60mm to 90mm. It is used to convert the horizontal displacement deviation into sliding force along the inclined surface during the segment docking process, so as to realize mechanically assisted self-guided alignment.

[0053] In the above technical solution, the larger the angle between the oblique meshing surface and the joint normal direction, the greater the horizontal component force, but the more obvious the stress concentration at the key root; the smaller the angle, the smoother the alignment, but the lower the compensation capability. Here, the joint normal direction is the normal direction of the joint surface.

[0054] In the above technical solution, the shear keyway matches the trapezoidal shear key, and the depth of the shear keyway is slightly larger than the key depth of the trapezoidal shear key to accommodate the epoxy resin sealing layer. In addition, a 2mm thick polytetrafluoroethylene wear-resistant gasket is provided on the bottom surface of the shear keyway to reduce the alignment friction coefficient.

[0055] In the above technical solution, during the descent of the box girder segment 1 carried by the UAV, due to the influence of wind field or hovering accuracy, the box girder segment 1 may deviate in the horizontal direction. The trapezoidal shear key generates a horizontal component force through the oblique meshing surface, forcibly pushing the segment to the correct position. Here, the horizontal component force generated by the oblique meshing surface is based on the vertical force during the descent of the box girder segment 1 and the angle of the oblique meshing surface relative to the joint normal direction. It is confirmed that, among them, To generate a horizontal component force on the oblique meshing surface, For the vertical force during the descent of box girder segment 1, It is the angle between the oblique meshing surface and the direction of the joint normal.

[0056] In the above technical solution, during the descent of box girder segment 1 carried by the UAV, the maximum compensable horizontal deviation of box girder segment 1 is determined by the key depth of the trapezoidal shear key and the angle of the oblique meshing surface relative to the joint normal direction, and its geometric relationship is as follows: ,in, To maximize the compensable horizontal deviation, The key depth of the trapezoidal shear key. This refers to the angle of the oblique meshing surface relative to the joint normal direction. Furthermore, the compensation time depends on the horizontal deviation, the angle of the oblique meshing surface relative to the joint normal direction, and the coefficient of friction of the oblique meshing surface. Analysis determined that, To compensate for the time required, The horizontal deviation of box girder segment 1 The angle between the oblique meshing surface and the normal direction of the joint. It is the acceleration due to gravity. is the coefficient of friction of the inclined meshing surface.

[0057] In the above technical solution, the oblique meshing surface of the trapezoidal shear key is coated with a layer of polytetrafluoroethylene (PTFE) friction-reducing coating or nano-graphite lubricating layer to reduce the friction coefficient during the docking process, prevent the high-strength steel surface from generating sparks or wear due to hard friction, and ensure smooth alignment and sliding.

[0058] In the above technical solution, the trapezoidal shear key is welded to the main load-bearing frame 2 at the end of the box girder segment 1, and the weld between the trapezoidal shear key and the main load-bearing frame 2 is reinforced to ensure that it can withstand the impact load at the moment of docking and the structural shear force after the bridge is completed.

[0059] Furthermore, such as Figure 3 As shown, the remote self-locking fastening system includes a preload spring c, a one-way self-locking wedge d, and a locking pin e; when the trapezoidal shear key is fully engaged, the normal pressure generated between the segments causes the preload spring c to release, thereby popping out the one-way self-locking wedge d and locking it into the opposite groove, and the locking pin e realizes the locking between the box girder segments 1 and 1.

[0060] In the above technical solution, the ultimate bearing capacity of the one-way self-locking wedge d is determined based on the property characteristics of the one-way self-locking wedge d and the preload spring c. Here, the property characteristics of the one-way self-locking wedge d include: the friction coefficient of the one-way self-locking wedge d and the size of the self-locking angle of the one-way self-locking wedge d. The specific analysis and calculation formula for the ultimate bearing capacity of the one-way self-locking wedge d is as follows: ; In the above formula, The ultimate bearing capacity of the unidirectional self-locking wedge d is... Let d be the coefficient of friction of the unidirectional self-locking wedge. The value of the self-locking angle of the unidirectional self-locking wedge d is given. The normal force provided to the preloaded spring c.

[0061] In the above technical solution, when the inter-segment normal pressure is based on the pre-compression spring c to eject the one-way self-locking wedge d, the end face normal distance between the two box girder segments 1 approaches zero. The contact pressure at the docking end of the box girder segment 1 squeezes the mechanical compensation docking mechanism. Based on the inter-segment normal pressure, the pre-compression spring c loses its constraint and quickly releases elastic potential energy, pushing the one-way self-locking wedge d to eject along the guide rail.

[0062] In the above technical solution, after the one-way self-locking wedge d is inserted into the opposite groove, due to the continuous thrust of the preload spring c, the one-way self-locking wedge d forms a tight frictional locking state with the inner wall of the groove. At this time, the locking pin e is released, and the locking pin e passes through the end of the movement path of the one-way self-locking wedge d in the horizontal or vertical direction, thereby realizing the locking between the box girder segments 1 and 1.

[0063] In the above technical solution, the locking pin e is the final safety redundancy component. It also provides feedback on the locking completion signal between box girder segments 1 after passing through the end of the movement path of the unidirectional self-locking wedge block d in the horizontal or vertical direction. This allows the UAV operator to understand that box girder segments 1 have achieved rigid connection, so that they can confidently execute the sling release command.

[0064] Furthermore, the wedge angle of the unidirectional self-locking wedge d is smaller than the self-locking critical angle; multiple unidirectional self-locking wedges d are arranged at the joint position of the box girder segment 1, and the unidirectional self-locking wedge d integrates a remote electronically controlled unlocking actuator, which is used to receive non-destructive disassembly commands from the ground control terminal and drive the wedge to rebound and reset.

[0065] In the above technical solution, when multiple one-way self-locking wedges d are arranged at the joint position of box girder segment 1, 8 to 12 one-way self-locking wedges d are symmetrically arranged along the top plate, bottom plate and two side webs at the joint position of box girder segment 1 to ensure uniform stress at the joint and eliminate rotational freedom after splicing.

[0066] In the aforementioned technical solution, the one-way self-locking wedge d forms a geometric shape that is easy to enter but difficult to exit by setting a self-locking angle. Once it pops out and locks into the groove, it cannot be bounced back by the vibration of the beam itself or the reverse tension. To achieve fully unmanned disassembly and transportation, the one-way self-locking wedge d further integrates a remotely controlled electronic unlocking actuator, such as a shape memory alloy wire or a miniature electromagnetic push rod. When a disassembly command is received, the actuator releases a reverse thrust to overcome the self-locking state, driving the one-way self-locking wedge d to bounce back and disengage, thereby eliminating the operational risks of manually carrying hydraulic tools into the box girder or performing high-altitude unlocking. The value of the self-locking angle of the one-way self-locking wedge d is related to its coefficient of friction, conforming to... The conditions and constraints, here, The value of the self-locking angle of the unidirectional self-locking wedge d is given. d is the friction coefficient of the unidirectional self-locking wedge.

[0067] The aforementioned mechanical compensation docking mechanism, utilizing the inclined meshing surface design of the trapezoidal shear key, transforms horizontal deviations during hoisting into geometric guiding forces through the component of gravity. This ensures smooth guidance while maximizing docking tolerance, enabling the UAV to precisely align box girder segment 1 even in unstable airflow environments. The linkage between the preloaded spring c and the self-locking wedges achieves automatic locking based on physical contact feedback, transforming traditional external power fastening into an active mechanical response within the structure. This significantly increases the bridge construction speed and achieves complete unmanned operation on the construction site, enhancing construction safety. The wedge angle of the unidirectional self-locking wedge d is smaller than the critical self-locking angle, ensuring that once the locking pin e is in place, the wedge cannot slip off under external vibration or alternating loads. This makes the locking between box girder segments 1 more reliable. Furthermore, multiple unidirectional self-locking wedges d are arranged at the joints to distribute locking force along the joint length, preventing eccentric loading or localized stress concentration and improving the overall integrity and fatigue resistance of the assembled girder.

[0068] In one embodiment of the present invention, the box girder segment 1 is provided with a visual or laser alignment mark on the edge of the hoisting interface 4 for identification by the UAV visual sensor, so as to assist in achieving coarse positioning in the air.

[0069] In the above technical solution, visual or laser alignment markers are symmetrically distributed around the center of the hoisting interface 4. The visual alignment markers use high-contrast geometric shapes, such as ArUco codes or QR code arrays, sprayed or pasted onto the flat area around the hoisting interface 4. The surface uses a fluorescent coating with retroreflective properties to ensure a high signal-to-noise ratio even when the drone's built-in supplementary lighting is on, especially during rainy days or nighttime operations. Laser alignment markers are sprayed or pasted onto the four corners of the hoisting interface 4 using corner reflectors or specially designed laser reflective patches. Combined with the drone's LiDAR or laser rangefinder, the precise altitude and horizontal displacement data of the segment are obtained by calculating the time-of-flight (ToF) and intensity of the reflected beam. Both methods can be used individually or in combination to ensure the reliability of coarse positioning for the drone under different weather conditions and time periods, improving environmental adaptability.

[0070] In the above technical solution, when the UAV visual sensor is used to assist in achieving coarse positioning in the air, the UAV is guided to the target area for visual scanning via RTK-GNSS. Once the alignment mark on the edge of the hoisting interface 4 is identified, the UAV no longer relies entirely on satellite positioning and automatically switches to the airborne visual guidance mode. The altitude is determined by identifying the size change of the alignment mark, and the pitch and roll angles are determined by the geometric distortion of the alignment mark, thereby finely adjusting the hovering attitude in real time.

[0071] By setting visual or laser alignment markers on the edge of the hoisting interface 4 of box girder segment 1, the UAV can identify the markers in real time with the help of airborne visual sensors, thereby completing the coarse positioning relative to the segment to be docked in the air. This allows the mechanical compensation docking mechanism of the segment to be installed to be lowered into the capture range of the installed segment, completing a smooth transition from satellite guidance to local perception. This eliminates the need for the UAV to rely on high-precision GPS or expensive external guidance equipment, and can guide the segment to the effective range of the mechanical compensation docking mechanism based solely on airborne vision. This reduces the accuracy requirements and operational difficulty of the UAV flight control system, while avoiding high-frequency control jitter caused by relying solely on vision. It also compensates for the limited travel of the mechanical compensation docking mechanism, together forming a graded and fault-tolerant aerial assembly and alignment scheme, improving the success rate of docking box girder segment 1, and thus shortening the time of a single hoisting operation. Moreover, placing the alignment mark on the edge of the hoisting interface 4 ensures that it remains within the clear field of view of the airborne vision while the UAV is mounted, facilitating continuous tracking during hoisting, moving, and approaching. It also eliminates the need for additional marking structures in other parts of the segment, achieving a balance between functional integration and structural simplicity without affecting the overall stress and aesthetics of the main load-bearing frame 2 and the CFRP reinforcement layer.

[0072] This invention provides a construction method for bridges, applicable to any of the aforementioned UAV-mounted high-strength steel-composite material self-monitoring beams, such as... Figure 4 and Figure 5 As shown, its construction methods include: Step 1: Use a drone to carry the box girder segment 1 to be installed through the hoisting interface 4 and take off, and guide it to the target location via RTK-GNSS; Step 2: Identify the installed box girder segment 1 and obtain the installation information of the installed box girder segment 1; Step 3: Adjust the hovering position according to the installation information of the installed box girder segment 1; Step 4: Descend slowly at a preset speed based on the hovering position; Step 5: After the box girder segment 1 to be installed makes contact with the box girder segment 1 already installed through the mechanical compensation docking mechanism, the remote self-locking fastening system automatically locks the connection, completing the rigid connection. Step 6: The UAV detaches from and releases the box girder segment 1 to be installed via the hoisting interface 4. Utilizing the unloading rebound vibration or mechanical triggering energy generated at the moment of detachment and release, the PZT piezoelectric energy harvesting module 3a converts it into instantaneous electrical energy to forcibly wake up the wireless sensor 3b, completing the first black start and self-activating the self-powered sensing network 3 of the box girder segment 1 to be installed, thus starting the self-powered wireless health monitoring.

[0073] Furthermore, the hoisting cycle of the box girder segment 1 to be installed is 8-12 minutes, and it complies with road and low-altitude air transport restrictions during transportation.

[0074] The installation information in the above technical solution includes: spatial location information, attitude angle information, etc.

[0075] In the above technical solutions, the restrictions on low-altitude air transport include: the size of the air transport, the weight of the air transport, etc.

[0076] In the above technical solution, in steps two and three, the UAV determines its altitude by recognizing changes in the size of the alignment markers and determines its pitch and roll angles by the geometric distortion of the alignment markers, thereby fine-tuning its hovering attitude in real time under airborne visual guidance mode.

[0077] The above-mentioned technical solution is applicable to the rapid construction of large structures such as bridges in complex environments. Through the synergistic effect of UAV hoisting, high-precision visual-assisted docking, and remote self-locking fastening system, high efficiency, high precision, and unmanned operation of bridge construction are achieved. This not only shortens the construction cycle and reduces the construction difficulty in special terrains, but also enables the bridge to have intelligent attributes of construction-monitoring by synchronously activating the self-powered sensing network 3, realizing the synchronization and integration of construction and monitoring. By adopting high-strength steel-composite material box girder segments 1, the load requirements of UAV hoisting are reduced, while the self-powered wireless health monitoring significantly improves the maintenance efficiency and operational safety of the structure throughout its entire life cycle. Furthermore, the multi-box girder segment 1 design of the UAV hoisting high-strength steel-composite material self-monitoring beam can efficiently coordinate with UAV hoisting, eliminating the need for large lifting machinery, enhancing the construction flexibility and convenience in complex terrain environments, and thus shortening the construction cycle. Furthermore, the mechanical compensation docking mechanism and remote self-locking fastening system enable stable installation in the dynamic environment of drone hoisting, automatically correcting minor alignment deviations caused by airflow or hovering sway, improving the splicing accuracy between box girder segments 1, and eliminating the need for manual intervention in construction operations, reducing the risks of high-altitude operations caused by manual intervention, ensuring construction safety, reducing environmental sensitivity, and guaranteeing the wind resistance stability of the structure during the construction phase.

[0078] Those skilled in the art should understand that the terms "first" and "second" in this invention merely refer to different application stages.

[0079] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

[0080] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A drone-mounted high-strength steel-composite material self-monitoring beam, characterized in that, The UAV-mounted high-strength steel-composite material self-monitoring beam is composed of multiple box girder segments (1). Each box girder segment (1) includes a main load-bearing frame (2). The main load-bearing frame (2) integrates a self-powered sensing network (3). A CFRP composite reinforcement layer is pasted on the outer surface of the main load-bearing frame (2). A hoisting interface (4) is provided above the main load-bearing frame (2). A mechanical compensation docking mechanism is provided at the end. A remote self-locking fastening system is deployed in the mechanical compensation docking mechanism.

2. The UAV-mounted high-strength steel-composite material self-monitoring beam according to claim 1, characterized in that, The main load-bearing frame (2) is made of high-strength steel with a yield strength ≥690MPa and a single segment weight ≤1500kg.

3. The UAV-mounted high-strength steel-composite material self-monitoring beam according to claim 1, characterized in that, The CFRP composite reinforcement layer is pasted at the hoisting interface (4) in accordance with the multi-directional ply structure and the ply sequence to form a hoisting stress diffusion zone.

4. The UAV-mounted high-strength steel-composite material self-monitoring beam according to claim 1, characterized in that, The self-powered sensing network (3) includes a PZT piezoelectric energy harvesting module (3a) and a wireless sensor (3b). The PZT piezoelectric energy harvesting module (3a) stores the generated electrical energy in a supercapacitor. When the voltage of the supercapacitor exceeds a preset threshold, the wireless sensor (3b) is activated to collect and transmit strain data.

5. The UAV-mounted high-strength steel-composite material self-monitoring beam according to claim 1, characterized in that, The mechanical compensation docking mechanism is located at the docking end of adjacent segments and includes a trapezoidal shear key and its matching shear keyway. The trapezoidal shear key has an inclined meshing surface with an angle of 45° to 60° relative to the joint normal direction and a key depth of 60mm to 90mm. It is used to convert horizontal displacement deviation into sliding force along the inclined surface during segment docking, thereby achieving mechanically assisted self-guided alignment.

6. The UAV-mounted high-strength steel-composite material self-monitoring beam according to claim 5, characterized in that, The remote self-locking fastening system includes a preload spring (c), a one-way self-locking wedge (d), and a locking pin (e). When the trapezoidal shear key is fully engaged, the normal pressure generated between the segments causes the preload spring (c) to release, thereby popping out the one-way self-locking wedge (d) and locking it into the opposite groove. The locking pin (e) then achieves the locking between the box girder segments (1) and the box girder segments (1).

7. The UAV-mounted high-strength steel-composite material self-monitoring beam according to claim 6, characterized in that, The wedge angle of the unidirectional self-locking wedge (d) is less than the self-locking critical angle; multiple unidirectional self-locking wedges (d) are arranged at the joint position of the box girder segment (1), and the unidirectional self-locking wedge (d) is integrated with a remote electric unlocking actuator, which is used to receive the non-destructive disassembly command from the ground control terminal and drive the wedge to rebound and reset.

8. The UAV-mounted high-strength steel-composite material self-monitoring beam according to claim 1, characterized in that, The box girder segment (1) is provided with visual or laser alignment marks on the edge of the hoisting interface (4) for identification by the UAV visual sensor, so as to assist in achieving coarse positioning in the air.

9. A construction method for the UAV-mounted high-strength steel-composite material self-monitoring beam described in any one of claims 1-8, characterized in that, The construction method includes: The UAV takes off with the box girder segment (1) to be installed through the hoisting interface (4) and is guided to the target location by RTK-GNSS; Identify the installed box girder segment (1) and obtain the installation information of the installed box girder segment (1); Adjust the hovering position according to the installation information of the installed box girder segment (1); Descends slowly at a preset speed based on the hovering position; When the box girder segment (1) to be installed comes into contact with the box girder segment (1) already installed through the mechanical compensation docking mechanism, it is automatically locked by the remote self-locking fastening system to complete the rigid connection; The UAV detaches from and releases the box girder segment (1) to be installed via the hoisting interface (4). Using the unloading rebound vibration or mechanical triggering energy generated at the moment of detachment and release, the PZT piezoelectric energy harvesting module (3a) converts it into instantaneous electrical energy to forcibly wake up the wireless sensor (3b), completes the first black start and self-activates the self-powered sensing network (3) of the box girder segment (1) to be installed, and starts the self-powered wireless health monitoring.

10. The construction method according to claim 9, characterized in that, The hoisting cycle of the box girder segment (1) to be installed is 8-12 minutes, and all of them comply with the restrictions on road and low-altitude air transport during transportation.

Images