Pedestrian overpass canopy electromagnetic jacking construction method

Abstract

The invention discloses a construction method for electromagnetic jacking of a pedestrian overpass canopy, and aims to solve the construction problem of the pedestrian overpass canopy near an overhead high-voltage line. The method comprises the steps that the canopy structure is cut into an upper part and a lower part; blocking traffic at the jacking position and treating the foundation; a sliding device, a bearing device, a positioning device, an electromagnetic device, a supporting device and a limiting device are sequentially installed; the spiral hollow coil is electrified, so that the rainshed is jacked to a preset position by the electromagnetic force and then is fixed; welding a canopy and connecting the canopy to the bridge floor; and jacking is repeated until completion. According to the electromagnetic principle, personnel and equipment are prevented from entering a high-voltage line danger area, the construction safety is remarkably improved, meanwhile, the construction period is shortened, the cost is reduced, the canopy installation quality is ensured, and the device has wide application prospects and is particularly suitable for municipal engineering pedestrian overpass canopy construction projects with special condition limitations.

Description

Technical Field

[0001] The invention relates to the technical field of construction modeling, in particular to a construction method for electromagnetic jacking of a pedestrian bridge canopy. Background Art

[0002] In the process of continuous upgrading and transformation of urban infrastructure, conflicts between municipal construction and existing facilities are often encountered. For example, when constructing a pedestrian bridge canopy in an area with overhead high-voltage transmission lines, due to the certain height of the pedestrian bridge itself, when carrying out operations such as hoisting the canopy frame and installing glass, construction equipment and personnel are very likely to enter the protection range of the high-voltage line. The electromagnetic field around the high-voltage line may cause air breakdown, resulting in major casualties and mechanical damage accidents. If the transmission equipment is relocated, it will not only cost a lot of money, but also take a long time to construct, which is extremely unrealistic for municipal projects with tight construction schedules. Therefore, there is an urgent need for an innovative construction method that can not only ensure construction safety and prevent personnel and equipment from entering the dangerous area of ​​the high-voltage line, but also efficiently and quickly complete the installation of the pedestrian bridge canopy to meet the needs of urban construction. Summary of the invention

[0003] In view of the above situation, and the fact that the canopy frame of the pedestrian bridge is made of rigid material, the purpose of the present invention is to provide a construction method for electromagnetic lifting of the canopy of the pedestrian bridge, which uses the electromagnetic force generated by the electromagnetic induction phenomenon to complete the installation of the canopy without entering the dangerous area of ​​the overhead high-voltage line, thereby avoiding the major casualties that may occur in the construction of the traditional method. By setting multiple groups of spiral hollow coils under the canopy of the pedestrian bridge, an electromagnetic field is generated around the coils after the coils are energized. The electromagnetic field will generate an electromagnetic force in the opposite direction of gravity on the steel frame of the canopy, thereby lifting the canopy frame to a predetermined position, fixing it through upper and lower limit devices, supporting the upper half of the canopy and welding the lower half of the frame, and finally completing the installation of the canopy without entering the protection range of the high-voltage line.

[0004] In order to achieve the above object, the present invention is implemented through the following technical scheme: a construction method for electromagnetic jacking of a pedestrian bridge canopy, comprising the following steps:

[0005] Pretreatment of the canopy structure: First, cut the canopy structure into two parts, the upper and lower parts. The cutting position can be selected according to the actual structure and mechanical properties of the canopy, but is not limited to the center of the structure. At the same time, it is necessary to ensure that the incision is a horizontal incision so that it can fit closely with the supporting device later to ensure stability and reliability during the construction process.

[0006] Construction site preparation:

[0007] Before the operation, the traffic at the jacking position is strictly blocked, and no vehicles or pedestrians are allowed to pass. A clear cordon is set up around it to prevent unauthorized personnel from entering the dangerous construction area.

[0008] The foundation at the working location is fully leveled, and the foundation bearing capacity is reviewed through professional testing methods to ensure that the foundation can withstand various loads during the construction process and to prevent safety accidents such as overturning of the jacking device due to uneven foundation settlement or insufficient bearing capacity during construction.

[0009] Sliding device installation:

[0010] Carry out precise measurement and layout work, use high-precision measuring instruments to accurately locate the projection position of the pre-lifting structure on the ground, and make clear markings.

[0011] Lay the rails according to the marked positions and evenly lay sleepers under the rails to enhance the stability and load-bearing capacity of the rails. Use anchor bolts to firmly connect the rails to the ground at certain intervals to ensure that the rails will not move during construction. In addition, the sleepers between the rails are arranged in a triangle to further improve the stability and seismic resistance of the entire sliding device.

[0012] Load-carrying device installation:

[0013] A load-bearing device is installed above the sliding device. The load-bearing device mainly consists of an upper crossbeam (distribution beam), a lower load-bearing tire frame, a retractable top support inside the tire frame, and track pulleys. Among them, the crossbeam is made of hot-rolled H-shaped steel and is rigidly connected through a reliable connection method to ensure that it has sufficient strength and rigidity to withstand the weight of the canopy structure and various forces during the jacking process. The tire frame is made of steel pipes, and the diagonal braces and horizontal braces between the brackets are reinforced with angle steel to enhance the overall stability of the load-bearing device. The track pulley itself has grooves, which can enable the load-bearing device to move smoothly and smoothly on the sliding device, reducing friction and resistance during movement.

[0014] Each component is welded with a fitting fillet weld to ensure a firm and reliable connection. The outer surface of the load-bearing device is coated with insulating paint to prevent the electromagnetic force generated during the electromagnetic lifting process from causing unnecessary impact on the load-bearing device itself and surrounding auxiliary devices, ensuring the safety and stability of the construction process.

[0015] A lifting device is installed between adjacent load-bearing devices. The lifting device is used to place the spiral hollow coil. At the same time, a retractable jacking support is reasonably placed in the main tire frame of the load-bearing device to provide reliable support and adjustment means for subsequent jacking operations. After the installation of the load-bearing device is completed, it must undergo strict quality inspection to ensure that all technical indicators meet the design requirements and construction specifications. Only after the inspection is qualified can the next jacking operation be carried out.

[0016] Installation of positioning device: Install a positioning tripod at the track pulley of the sliding device. The tripod is inserted into the slide rail to form a stable mortise and tenon structure. This structure can effectively prevent the sliding device from sliding freely on the slide rail, ensure the position accuracy and stability of the bearing device and the canopy structure during the construction process, and provide reliable basic conditions for electromagnetic jacking operations.

[0017] Arrangement of electromagnetic device: Accurately place multiple groups of spiral hollow coils above the lifting device, and ensure that the direction of the current entering the coil is counterclockwise, so that vertical electromagnetic force can be generated according to the principle of electromagnetic induction to provide power support for the lifting of the canopy structure. By reasonably controlling the number of coil groups, number of turns, current size and other parameters, the size and direction of the electromagnetic force can be accurately adjusted to meet the needs of different canopy structures and construction conditions.

[0018] Support device installation: The support device is installed on the top surface of the load-bearing device. The support device is made of insulating material to avoid electromagnetic interference and conduction. The support device spans between adjacent load-bearing devices and is reliably connected to the retractable top support in the load-bearing device through the reserved holes to form a stable support system for effectively supporting and positioning the canopy structure during the lifting process, ensuring the verticality and horizontality of the canopy structure during the lifting process, and preventing tilting and offset.

[0019] Installation of limit devices: Install limit devices on both sides of the load-bearing device. The limit devices mainly include sensors and uprights. The position of the sensor is the final height after jacking. Through precise debugging and calibration, it can accurately detect whether the canopy structure has reached the predetermined position. At the same time, the sensor is electrically connected to the retractable top support to realize automatic control and feedback adjustment functions. When the sensor detects that the canopy structure has reached the predetermined position, it can send a signal in time to start the corresponding control program, such as reducing the current output, extending the retractable top support, etc., to ensure the accuracy and safety of the construction process.

[0020] Electromagnetic lifting operation:

[0021] After completing the installation and debugging of the above devices, the spiral hollow coil is energized. During the power-on process, the current gradually increases from zero, causing the electromagnetic force to gradually increase, thereby driving the canopy structure to rise slowly and evenly. During the lifting process, the real-time monitoring system closely monitors the rising state of the canopy structure to ensure that its rising process is smooth, without jamming and abnormal vibration.

[0022] When the canopy structure reaches the predetermined position, the sensor immediately detects this state and sends out a light alarm signal to remind the operator to start reducing the current output. According to the alarm signal, the operator gradually and steadily reduces the current until the canopy structure is in a static suspended state and stops the current adjustment operation. At this time, after waiting for the retractable top support to reach the predetermined position, continue to slowly reduce the current until the power is completely cut off. At the same time, the retractable top support extends from the bearing device, and the jacking support device is lifted to the bottom of the canopy structure, so that it fits tightly with the canopy structure to form a stable support structure, ensuring the safety and stability of the canopy structure during the subsequent construction process.

[0023] Welding and fixing of canopy: Weld the lower and upper parts of the canopy precisely to ensure that the welding quality meets the requirements of relevant standards and specifications, so that the canopy structure forms a complete whole. At the same time, firmly connect the lower part of the canopy to the deck structure of the pedestrian bridge, and use reliable connection methods such as bolt connection and welding to ensure the connection strength and stability between the canopy and the deck, so that it can withstand various natural environments and use loads, and ensure the long-term safety and reliability of the canopy.

[0024] Device reset and repeat operation: After completing the above canopy welding and fixing operations, ensure that all electrical equipment is completely powered off and keep it powered off for more than half an hour to ensure that the electromagnetic device completely stops working and eliminate residual electromagnetic force and electrical safety hazards. Then, remove the tripod positioning, push the bearing device to the next lifting position manually or mechanically, and repeat the lifting process according to the above steps until the lifting operation of the entire pedestrian bridge canopy is completed, so as to achieve efficient and safe installation of the entire canopy.

[0025] The present invention has the following beneficial effects:

[0026] 1. High safety: The present invention utilizes electromagnetic force to lift the canopy, which prevents construction personnel and equipment from entering the dangerous area of ​​overhead high-voltage lines, effectively prevents casualties and mechanical damage accidents caused by air breakdown caused by electromagnetic fields, and greatly improves the safety of the construction process.

[0027] 2. High construction efficiency: Compared with the traditional construction method of migrating power transmission equipment or taking other complex protective measures, the electromagnetic jacking construction method of the present invention is easy to operate and has a compact process. It can significantly shorten the construction period, improve construction efficiency, and meet the requirements of short construction period for municipal engineering.

[0028] 3. Cost saving: It avoids the high cost of relocating power transmission equipment and various additional costs caused by the extension of construction period, such as labor costs, equipment rental costs, etc., while reducing the impact on the surrounding environment and traffic, and reducing the overall construction cost.

[0029] 4. Reliable construction quality: Through precise measurement and layout, reasonable device design and installation, and stable electromagnetic jacking control, the stability and accuracy of the canopy structure during the jacking process can be ensured, the installation quality of the canopy can be guaranteed, and the overall performance and service life of the pedestrian bridge can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0031] Figure 1 It is a side view of the electromagnetic lifting device;

[0032] Figure 2 It is a schematic diagram of the canopy cross section;

[0033] Figure 3 It is a schematic diagram of the canopy structure force;

[0034] Figure 4 is a schematic diagram of the structure of the sliding device;

[0035] Figure 5 It is a schematic diagram of the structure of the bearing device.

[0036] Specific structural description in the figure: 1-canopy structure, 21-slide rail, 22-sleeper, 23-anchor bolt, 31 track pulley, 32-main frame (steel pipe), 33-retractable top support, 34-diagonal brace, 35-cross beam (distribution beam), 4-lifting device, 5-support device, 51-reserved hole, 6-spiral hollow coil, 71-vertical pole, 72-sensor. DETAILED DESCRIPTION

[0037] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0038] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, upper end, lower end, top, bottom...) are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0039] In the present invention, unless otherwise clearly defined and limited, the term "connection" should be understood in a broad sense, for example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] In addition, in the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features; in addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0041] The following is combined with Figure 1 To Attachment Figure 5 The present invention is described in further detail.

[0042] Reference Figures 1 to 5 The present invention has carefully constructed a construction method for electromagnetic lifting of a pedestrian bridge canopy, which includes the following steps:

[0043] 1. First, cut the canopy structure 1 into two parts, the cutting position can be selected but not limited to the center of the structure, and the incision must be a horizontal incision to ensure a close fit with the supporting device 5.

[0044] 2. Before the operation, the traffic at the jacking location must be blocked, and no people or vehicles are allowed to pass through. A cordon must be placed around it. At the same time, the foundation of the operation location must be leveled and the bearing capacity of the foundation must be reviewed to prevent the device from overturning due to uneven ground during the jacking process;

[0045] 3. Carry out precise measurement and layout to locate the projection position of the pre-lifting structure on the ground. After marking the position, lay the slide rails 21 and sleepers 22 to form a sliding device. Connect the slide rails 21 to the ground through anchor bolts 23 at intervals. The sleepers 22 between the slide rails 21 are arranged in a triangle to enhance stability.

[0046] 4. Install the bearing device above the sliding device. The bearing device consists of an upper crossbeam (distribution beam), a lower bearing tire frame, a retractable top support 33 inside the tire frame, and a track pulley 31. The crossbeam 35 (distribution beam) is made of hot-rolled H-shaped steel. The crossbeams 35 are rigidly connected. The tire frame is made of steel pipes. The diagonal braces 34 and horizontal braces between the brackets are made of angle steel. The track pulley 31 itself has grooves to allow the bearing device to move smoothly on the sliding device. Each component is welded with fitted corner welds. The outer surface of the bearing device needs to be coated with insulating paint as a whole to prevent the electromagnetic force generated from pushing the auxiliary device. A lifting device 4 is installed between adjacent bearing devices to place the spiral hollow coil 6, and a retractable top support 33 is placed in the main tire frame 32 of the bearing device. After the bearing device is installed, it must be inspected and accepted before the jacking operation can be carried out;

[0047] 5. Install a positioning tripod at the slide track pulley 31, and insert the tripod into the slide rail 21 to form a mortise and tenon structure to prevent the slide device from sliding freely on the slide rail 21;

[0048] 6. Multiple groups of spiral hollow coils 6 are placed above the lifting device 4;

[0049] 7. A support device 5 is installed on the top surface of the load-bearing device. The support device 5 is made of insulating material and spans between adjacent load-bearing devices. The support device 5 is connected to the retractable top support 33 in the load-bearing device through a reserved hole 51;

[0050] 8. Limiting devices are installed on both sides of the bearing device. The limiting devices include sensors 72 and uprights 71. The position of the sensor 72 is the final height after jacking. The sensor 72 is connected to the retractable jacking support 33.

[0051] 9. The coil is energized, and the direction of the energized current entering the coil must be counterclockwise to generate a vertically upward electromagnetic force, which gradually increases from zero, so that the vertically upward electromagnetic force gradually increases until the canopy structure 1 rises slowly and evenly. After reaching the predetermined position, the sensor 72 detects that the canopy structure 1 has arrived and starts to light up an alarm, reminding the operator to start reducing the current output until the canopy structure 1 is suspended in a static state, and stops the operation until the retractable top support 33 arrives and then continues to reduce the current until the power is completely cut off. After the sensor 72 alarms, the retractable top support 33 is extended from the bearing device, and the lifting support device 5 is lifted to the bottom of the canopy structure 1 and fits closely with it;

[0052] 10. Weld the lower part of the canopy to the upper part, and connect the lower part to the deck structure of the pedestrian bridge;

[0053] 11. After the power is completely cut off for more than half an hour, remove the tripod positioning, push the carrying device to the next jacking position and repeat the above jacking process until the jacking operation of the entire pedestrian overpass canopy is completed.

[0054] The present invention has the following beneficial effects:

[0055] 1. High safety: The present invention utilizes electromagnetic force to lift the canopy, which prevents construction personnel and equipment from entering the dangerous area of ​​overhead high-voltage lines, effectively prevents casualties and mechanical damage accidents caused by air breakdown caused by electromagnetic fields, and greatly improves the safety of the construction process.

[0056] 2. High construction efficiency: Compared with the traditional construction method of migrating power transmission equipment or taking other complex protective measures, the electromagnetic jacking construction method of the present invention is easy to operate and has a compact process. It can significantly shorten the construction period, improve construction efficiency, and meet the requirements of short construction period for municipal engineering.

[0057] 3. Cost saving: It avoids the high cost of relocating power transmission equipment and various additional costs caused by the extension of construction period, such as labor costs, equipment rental costs, etc., while reducing the impact on the surrounding environment and traffic, and reducing the overall construction cost.

[0058] 4. Reliable construction quality: Through precise measurement and layout, reasonable device design and installation, and stable electromagnetic jacking control, the stability and accuracy of the canopy structure during the jacking process can be ensured, the installation quality of the canopy can be guaranteed, and the overall performance and service life of the pedestrian bridge can be improved.

[0059] In practical application, preparation before construction:

[0060] A professional construction team is formed, including engineers, technicians, electricians, welders, etc. with rich experience in construction, to ensure that personnel in each position have the corresponding professional skills and qualification certificates and are familiar with the construction method and process flow of the present invention.

[0061] Prepare all kinds of materials and equipment required for construction, such as hot-rolled H-shaped steel, steel pipes, angle steel, insulating paint, spiral hollow coils, welding equipment, measuring instruments, electrical control equipment, etc., and carry out strict quality inspection and debugging of all materials and equipment to ensure that their performance meets the design requirements and construction specifications.

[0062] Fully communicate and coordinate with relevant departments (such as the power department, traffic management department, etc.), complete the necessary construction procedures, obtain construction permits, and formulate detailed construction safety measures and emergency plans to ensure that the construction process will not cause adverse effects on the surrounding environment and public safety.

[0063] Canopy structure cutting:

[0064] According to the design drawings and actual structural characteristics of the canopy, select the appropriate cutting position and cutting tools. The cutting position should take into account the mechanical properties, weight distribution and convenience of subsequent construction of the canopy, so as to ensure that the upper and lower parts of the canopy structure can remain stable and balanced during the lifting process.

[0065] Use professional cutting equipment (such as plasma cutting machine, oxyacetylene cutting machine, etc.) to ensure that the cut is flat, smooth, and perpendicular to the canopy surface, and the error is controlled within the specified range. During the cutting process, take effective protective measures such as fire prevention, dust prevention, and splash prevention to ensure construction safety and a clean environment.

[0066] Site layout and foundation treatment:

[0067] According to the construction design plan, the traffic around the jacking position was closed, and obvious traffic warning signs and fences were set up to guide vehicles and pedestrians to detour. At the same time, a cordon was set up around the construction site, and unauthorized personnel were strictly prohibited from entering the construction area.

[0068] Conduct detailed survey and evaluation of the foundation at the jacking position, and formulate a reasonable foundation treatment plan based on the actual situation of the foundation. Use mechanical leveling, compaction, replacement and other methods to treat the foundation so that it can reach the bearing capacity and flatness required by the design. During the treatment process, strictly control the construction quality, conduct regular foundation bearing capacity testing, and ensure the stability and reliability of the foundation.

[0069] Sliding device installation:

[0070] According to the position determined by measurement and layout, the sleepers are laid first. The sleepers should be made of qualified and uniform wood and arranged closely on the ground in a triangular layout to ensure that the connection between the sleepers is firm and reliable to form a stable support foundation.

[0071] Install the slide rails on the sleepers, place them precisely at the predetermined position, and use anchor bolts to securely connect the slide rails to the ground. The specifications, quantity, and spacing of the anchor bolts should meet the design requirements to ensure that the slide rails will not move or deform when subjected to heavy loads. During the installation process, use measuring tools such as a level to strictly control the flatness and verticality of the slide rails to ensure that the installation accuracy of the slide rails meets the construction requirements.

[0072] Load-carrying device assembly and installation:

[0073] At the assembly site in the factory or construction site, the various components of the load-bearing device are assembled according to the design drawings and technical requirements. First, the lower load-bearing tire frame is welded into shape to ensure that the connection between the steel pipes is firm, and the welds are full and uniform without obvious defects. Then, the retractable top support inside the tire frame is installed, and its position and stroke are adjusted to enable it to work normally. Next, the upper crossbeam (distribution beam) is installed, and the crossbeam is connected to the load-bearing tire frame as a whole by a rigid connection method to ensure that the entire load-bearing device has sufficient strength and rigidity. Finally, the track pulley is installed so that it can roll freely and smoothly on the slide rail, and the pulley is debugged and lubricated to ensure that it runs smoothly and without jamming.

[0074] After the load-bearing device is assembled, its outer surface is painted with insulating paint. The insulating paint should be applied evenly and without omissions, and the thickness should meet the design requirements to ensure that the load-bearing device can work normally in the electromagnetic environment without being disturbed and affected by electromagnetic forces.

[0075] Use lifting equipment to lift the assembled load-bearing devices one by one to the top of the sliding device, and install them according to the predetermined spacing and position. During the installation process, ensure that the connection between the load-bearing device and the sliding device is firm and reliable, and the track pulley and the slide rail cooperate well to achieve smooth sliding movement. The connection between adjacent load-bearing devices should be tight to ensure the integrity and stability of the entire load-bearing system.

[0076] Installation of lifting device and electromagnetic device:

[0077] A lifting device is installed between adjacent load-bearing devices. The structure and size of the lifting device should be designed and manufactured according to the specifications and quantity of the spiral hollow coils to ensure that the coils can be placed stably and provide good support and fixing conditions for the coils. The connection between the lifting device and the load-bearing device should be firm and reliable to prevent loosening and displacement during the lifting process.

[0078] Place the spiral hollow coil on the lifting device according to the design requirements, and ensure that the coil is arranged neatly and tightly without looseness or deviation. At the same time, check the electrical connection line of the coil to ensure that the line connection is correct and firm, without short circuit, open circuit and other fault hazards. Before powering on, perform insulation resistance test on the coil to ensure that its insulation performance meets safety requirements.

[0079] Installation of support and limit devices:

[0080] The support device is made of insulating material and is customized according to the spacing of the load-bearing device and the size of the canopy structure. The support device is installed on the top surface of the load-bearing device, and the support device is connected to the retractable top support in the load-bearing device through the reserved holes to ensure that the connection is firm and reliable. The support device can withstand the weight of the canopy structure and the force during the lifting process. During the installation process, the horizontality and verticality of the support device are strictly controlled to ensure that it has good contact with the bottom of the canopy structure and can provide stable support.

[0081] Install the limit devices on both sides of the load-bearing device, firmly install the vertical pole on the load-bearing device, and ensure that it is perpendicular to the ground and accurately positioned. Then, install the sensor on the vertical pole, and adjust the height and position of the sensor so that it can accurately detect the lifting height of the canopy structure. The electrical connection between the sensor and the retractable top support should be correct to ensure that when the canopy structure reaches the predetermined position, the sensor can send a signal in time to control the movement of the retractable top support and realize the automatic lifting control and limit function.

[0082] Electromagnetic lifting operation:

[0083] After completing the installation and commissioning of all the above devices, conduct a comprehensive inspection of the construction site to ensure that all personnel and equipment are in a safe state and there are no obstacles that affect the jacking operation. Then, energize the spiral hollow coil according to the operating procedures.

[0084] At the beginning of power-on, increase the current slowly and observe the lifting of the canopy structure closely. By controlling the magnitude and rate of change of the current, the canopy structure can be raised at a slow and uniform speed to avoid accidents such as tilting, shaking or collision of the canopy structure due to excessive or uneven lifting speed. During the lifting process, use measuring instruments (such as levels, total stations, etc.) to monitor the verticality and horizontality of the canopy structure in real time, adjust the current magnitude and lifting speed in time, and ensure that the canopy structure always remains on the correct lifting trajectory.

[0085] When the canopy structure approaches the predetermined position, the rate of current increase is gradually reduced to more accurately control the lifting speed. When the sensor detects that the canopy structure has reached the predetermined position, an alarm signal is immediately issued. At this time, the operator should respond quickly and begin to gradually reduce the current output so that the canopy structure gradually stops rising and is in a static suspended state. After the canopy structure is stationary, wait for the retractable jacking support to reach the predetermined position, and then continue to slowly reduce the current until the power is completely cut off. At the same time, the retractable jacking support extends out of the lifting support device so that it fits tightly against the bottom of the canopy structure, completing the lifting and supporting operation of the canopy structure.

[0086] Canopy welding and fixing:

[0087] After the canopy structure is lifted into place and stably supported, welders are immediately organized to weld the lower and upper parts of the canopy. Before welding, the welding parts are cleaned and polished to remove impurities such as oil, rust and scale on the surface to ensure welding quality. Use appropriate welding technology and welding materials and perform welding operations according to design requirements.

[0088] Implementation case 1:

[0089] Project Overview:

[0090] The pedestrian bridge canopy installation project in the central area of ​​a city is located above a busy main road, and there is a 110kV overhead high-voltage line passing through it. The vertical distance between the high-voltage line and the installation location of the bridge canopy is 8 meters, and the horizontal distance is only 5 meters at the closest point. The overall structure of the canopy is a steel structure, with a length of 30 meters, a width of 4 meters, a height of 2.5 meters, and a total weight of about 15 tons. It is designed in an arc shape, which requires high installation accuracy.

[0091] Construction process:

[0092] Cutting of canopy structure: According to the mechanical analysis of the canopy and the on-site construction conditions, the canopy structure is cut at a distance of 1.2 meters from the bottom using a plasma cutting machine. The cutting speed is controlled at 300mm / min to ensure that the flatness deviation of the cut is within ±2mm. After cutting, the cut is polished to remove burrs and oxide layers so that the surface roughness reaches Ra6.3μm to ensure a close fit with the support device.

[0093] Site layout and foundation treatment:

[0094] Fences and traffic warning signs were set up within 50 meters around the jacking position to guide vehicles to detour, and 4 traffic controllers were arranged to be on duty 24 hours a day. A cordon with reflective signs was arranged 10 meters around the construction site, and 2 security personnel were arranged to patrol and guard, and unauthorized personnel were strictly prohibited from entering.

[0095] The foundation at the jacking position was surveyed and found to be silty clay with a bearing capacity of 120kPa, which did not meet the design requirement of 180kPa. The foundation was treated by replacing 500mm thick graded sand and gravel, compacted layer by layer, with each layer being 250mm thick and a compaction degree of more than 95%. After a flat plate load test, the foundation bearing capacity reached 200kPa, meeting the construction requirements.

[0096] Sliding device installation:

[0097] A total station with an accuracy of 1mm was used for measurement and layout to locate the projection position of the pre-lifting structure on the ground. The error was controlled within ±3mm, and clear and durable marks were made with red paint. The marked areas were covered with transparent plastic film to prevent wear and contamination.

[0098] A 43kg / m light rail is laid as the slide rail, and sleepers are evenly laid every 0.5m under the slide rail. The sleepers are made of larch with a moisture content of 18%, a compressive strength of 40MPa, and a bending strength of 60MPa. The slide rail is connected to the ground through M20 anchor bolts, and the tightening torque of the anchor bolts reaches 400N·m. The sleepers between the slide rails are arranged in a triangle, and the sleepers are connected with bolts with a diameter of 12mm to ensure that the stability and seismic performance of the sliding device meet the requirements of the local seismic fortification intensity of 7 degrees.

[0099] Load-carrying device installation:

[0100] The upper crossbeam of the bearing device is made of HM300×200 hot-rolled H-shaped steel, made of Q345B, with a yield strength of 345MPa, a tensile strength of 470MPa, and an elastic modulus of 206GPa. The crossbeams are rigidly connected with M24 10.9 grade high-strength bolts, and the preload force reaches 220kN. The lower bearing tire frame is made of Q235B steel pipe with a diameter of 159mm and a wall thickness of 6mm. The diagonal braces and horizontal braces between the brackets are reinforced with ∠75×5 angle steel. The welded connection parts are ultrasonically inspected, and the weld quality meets the second-level standard. The track pulley groove is 30mm deep and 40mm wide. The pulley is made of QT500-7 wear-resistant cast iron with a hardness of 170HB, which makes the moving resistance coefficient of the bearing device on the sliding device 0.08.

[0101] Each component is welded with a fitted fillet weld, with a weld height of 8mm and a length of 100mm. The weld is visually inspected and X-rayed to ensure that there are no defects. The outer surface of the load-bearing device is painted with two coats of epoxy insulating paint, with a breakdown voltage of 25kV and a coating thickness of 300μm. A self-made steel structure lifting device with a load-bearing capacity of 5kN is installed between adjacent load-bearing devices to place spiral hollow coils, and a retractable top support with a stroke of 200mm-500mm and a lifting force of 8kN is placed in the main tire frame of the load-bearing device. After the installation of the load-bearing device is completed, it is inspected and accepted in accordance with the design requirements and construction specifications, including component size measurement, connection quality inspection, insulation performance test, load-bearing capacity test, etc. The next step of operation can only be carried out after passing the acceptance, and detailed records of the acceptance process are formed and archived.

[0102] Installation of positioning device: A positioning tripod made of high-strength steel is installed at the track pulley of the sliding device. The tripod is made of Q345B with a yield strength of 345MPa, a tensile strength of 470MPa, and an elastic modulus of 206GPa. The matching accuracy of the tenon and mortise is controlled within ±1mm. The tripod is connected to the track pulley and the slide rail by welding, and the welding parts are inspected for flaws to ensure that it can withstand various forces during the construction process and effectively prevent the sliding device from sliding freely.

[0103] Layout of electromagnetic device: 8 groups of spiral hollow coils are placed above the lifting device. The number of coil turns is 200, the wire diameter is 2mm, and it is wound with polyimide insulated wires that are resistant to high temperatures and withstand a voltage of 10kV. The direction of the current entering the coil is counterclockwise. The electromagnetic force is precisely controlled by adjusting the current size (the current range is 0-100A). The adjustment accuracy of the electromagnetic force reaches ±50N, which meets the requirements of the canopy lifting. During the layout of the electromagnetic device, protective measures are taken for the coils, such as installing a protective cover to prevent mechanical damage, and using sealant to seal the wiring to prevent electrical short circuits.

[0104] Installation of support device: The support device is made of epoxy resin insulating material with a dielectric constant of 3.5 and a volume resistivity of 1×1014Ω·m. It spans between adjacent load-bearing devices with a span of 2 meters. The structure is a truss structure, which is connected to the retractable top support in the load-bearing device through reserved holes. A 10mm thick reinforcing rib is set at the connection part. The material of the reinforcing rib is the same as that of the support device to ensure that the support device has sufficient strength and rigidity. During the jacking process, the verticality deviation of the canopy structure is controlled within ±3mm, and the horizontality deviation is controlled within ±2mm.

[0105] Installation of limit device: high-precision displacement sensors are installed on both sides of the load-bearing device as limit devices, with a measurement accuracy of ±1mm. The position of the sensor is the final height after jacking, and the height deviation is controlled within ±2mm. Through debugging and calibration, it can accurately detect whether the canopy structure has reached the predetermined position. The sensor and the retractable top support are connected by a shielded cable, and the grounding resistance of the shielding layer is 0.5Ω, realizing automatic control and feedback adjustment functions. The pole is made of 304 stainless steel with a diameter of 50mm and a height of 1.5 meters. The pole and the load-bearing device are connected by welding, and the connection part is strength-checked to ensure its stability.

[0106] Electromagnetic lifting operation:

[0107] The spiral hollow coil is energized, and the current is gradually and steadily increased from zero at a rate of 5A / s, so that the electromagnetic force drives the canopy structure to rise slowly and evenly at a speed of 5mm / s. The rising state of the canopy structure is closely monitored through real-time monitoring systems such as displacement sensors, stress sensors and video monitoring. The monitoring data acquisition frequency is 10Hz to ensure that the rising process is smooth and the vibration amplitude of the canopy structure does not exceed ±2mm.

[0108] When the canopy structure reaches the predetermined position, the sensor sends out a light alarm signal within 0.5s, and the operator gradually reduces the current at a rate of 3A / s until the canopy structure is suspended in a static state and the current adjustment operation is stopped. At this time, wait for the retractable top support to reach the predetermined position at a speed of 10mm / s, and then continue to slowly reduce the current at a rate of 2A / s until the power is completely cut off. At the same time, the retractable top support extends the lifting support device to the bottom of the canopy structure, and the fitting gap is controlled within ±1mm to form a stable support structure.

[0109] Welding and fixing of canopy: CO2 gas shielded welding is used to weld the lower and upper parts of the canopy. The welding material is ER50-6 welding wire. The chemical composition and mechanical properties meet national standards. The welds are visually inspected and ultrasonically tested. The appearance inspection complies with GB 50205-2020 "Standards for Acceptance of Steel Structure Construction Quality". The qualified level of non-destructive testing is level 2, ensuring that the welds are defect-free. The lower part of the canopy is connected to the deck structure of the pedestrian overpass with M20 high-strength bolts, and the preload force reaches 180kN to ensure the strength and stability of the connection. The size and position accuracy deviation of the connection parts are controlled within ±2mm.

[0110] Device resetting and repeated operation: After completing the canopy welding and fixing operations, ensure that all electrical equipment is completely powered off and maintain this state for 40 minutes, remove the tripod positioning, manually push the load-bearing device to the next lifting position, and control the pushing speed at 3mm / s. Repeat the lifting process according to the above steps until the lifting operation of the entire pedestrian bridge canopy is completed. During the repeated operation, regularly inspect and maintain each device. If the pulley is found to be worn more than 2mm, replace it in time to ensure that its performance and accuracy meet the requirements.

[0111] Implementation case 2:

[0112] Project Overview:

[0113] A pedestrian bridge canopy construction project in a new district is surrounded by a commercial area under development, with heavy traffic. A 220kV overhead high-voltage line runs diagonally across the bridge. The vertical distance between the high-voltage line and the canopy installation location is 10 meters, and the horizontal distance is 8 meters at the closest point. The canopy structure is made of aluminum alloy, with a length of 40 meters, a width of 5 meters, a height of 3 meters, and a total weight of about 18 tons. It is designed with a wavy appearance, which requires high flatness and stability for installation.

[0114] Construction process:

[0115] Awning structure cutting: Taking into account the structural characteristics and construction convenience of the awning, the awning is cut at a distance of 1.5 meters from the bottom. Professional aluminum alloy cutting equipment is used with a cutting speed of 250mm / min to ensure that the flatness deviation of the cut is within ±1.5mm. After cutting, the cut is finely polished to a surface roughness of Ra3.2μm so that it can fit perfectly with the supporting device.

[0116] Site layout and foundation treatment:

[0117] Traffic control is implemented within 60 meters around the jacking position, solid fences and obvious traffic signs are set up, 6 traffic coordinators are arranged to guide vehicle diversion, and a cordon with warning lights is set up 12 meters around the construction site. 3 security personnel are arranged to be on duty 24 hours a day to prevent unauthorized personnel from entering the construction area.

[0118] After investigation, the foundation soil is sandy soil with a bearing capacity of 150kPa, which does not meet the design requirement of 200kPa. Layered rolling and tamping are adopted and a 600mm thick lime soil cushion layer is laid for treatment. The thickness of each layer of lime soil is 300mm, and the compaction coefficient reaches 0.97. Through static load test, the foundation bearing capacity is increased to 220kPa, which meets the construction bearing requirements.

[0119] Sliding device installation:

[0120] An electronic total station with an accuracy of 0.5mm is used to carry out precise measurement and layout to determine the projection position of the pre-lifting structure on the ground. The error is strictly controlled within ±2mm. Clear and eye-catching marks are made with yellow paint and covered with protective tape to prevent the marks from being damaged.

[0121] 50kg / m heavy rails are laid as slide rails, and sleepers are laid every 0.6 meters under the slide rails. The sleepers are made of larch with a moisture content of 15%, a compressive strength of 50MPa, and a bending strength of 70MPa. The slide rails are fastened to the ground by M22 anchor bolts, and the tightening torque of the anchor bolts reaches 500N·m. The sleepers between the slide rails are arranged in a triangle and fixed with special connectors to ensure that the overall stability and seismic performance of the sliding device meet the local seismic fortification requirements (seismic fortification intensity 8 degrees).

[0122] Load-carrying device installation:

[0123] The upper crossbeam of the bearing device is made of HN400×200 hot-rolled H-shaped steel, made of Q355B, with a yield strength of 355MPa, a tensile strength of 490MPa, and an elastic modulus of 206GPa. The crossbeams are rigidly connected with M27 10.9 grade high-strength bolts, and the preload force is 250kN. The lower bearing tire frame uses Q235B steel pipes with a diameter of 180mm and a wall thickness of 8mm. The diagonal braces and horizontal braces between the brackets are reinforced with ∠80×6 angle steel. The welding parts are tested by magnetic particle flaw detection, and the weld quality reaches level 2. The groove depth of the track pulley is 35mm and the width is 45mm. The pulley is made of QT600-3 wear-resistant cast iron with a hardness of 200HB. The moving resistance coefficient of the bearing device on the sliding device is 0.07.

[0124] The height of the fitting fillet welds between the components is 10mm and the length is 120mm. Appearance inspection and radiographic flaw detection are carried out to ensure the quality of the welds. The outer surface of the load-bearing device is painted with three coats of polyurethane insulating paint, with a breakdown voltage of 30kV and a coating thickness of 350μm. A customized aluminum alloy lifting device with a load-bearing capacity of 6kN is installed between adjacent load-bearing devices to place spiral hollow coils, and a retractable top support with a stroke of 250mm-600mm and a lifting force of 10kN is placed in the main tire frame of the load-bearing device. After the installation of the load-bearing device is completed, a comprehensive acceptance is carried out according to the design and specifications, including dimensional review, connection reliability inspection, insulation performance evaluation, load-bearing capacity test, etc. Only after passing the acceptance will the next step be entered. The acceptance records are detailed and archived.

[0125] Installation of positioning device: A positioning tripod made of high-strength steel is installed at the track pulley of the sliding device. The tripod is made of Q355B with a yield strength of 355MPa, a tensile strength of 490MPa, and an elastic modulus of 206GPa. The matching accuracy of the tenon and mortise is controlled within ±0.8mm. The tripod is connected to the track pulley and the slide rail by welding, and the welding parts are inspected for flaws to ensure that it can withstand various forces during construction and effectively prevent the sliding device from displacement.

[0126] Layout of electromagnetic device: 10 sets of spiral hollow coils are placed above the lifting device, with 250 turns of coils and a wire diameter of 2.5mm. They are wound with high-voltage and high-temperature resistant fluoroplastic insulated wires, and the insulation layer withstands a voltage rating of 15kV. The direction of the current is counterclockwise, and the electromagnetic force is precisely regulated by adjusting the current (the current range is 0-120A). The adjustment accuracy of the electromagnetic force reaches ±60N, which meets the power requirements of the canopy lifting. During the installation of the electromagnetic device, comprehensive protective measures are taken for the coils, such as installing guardrails to prevent collisions, and using waterproof tape to wrap the wiring to prevent moisture and short circuits.

[0127] Installation of support device: The support device is made of polycarbonate insulating material with a dielectric constant of 3.0 and a volume resistivity of 5×1014Ω·m. It spans between adjacent load-bearing devices with a span of 2.5 meters. It is designed as an arch structure and is connected to the retractable top support in the load-bearing device through reserved holes. Reinforcement ribs with a thickness of 12mm are set at the connection part. The material of the reinforcement ribs is the same as that of the support device to ensure that the support device has sufficient strength and rigidity. During the jacking process, the verticality deviation of the canopy structure is controlled within ±2.5mm, and the horizontality deviation is controlled within ±1.5mm.

[0128] Installation of limit device: high-precision laser displacement sensors are installed on both sides of the load-bearing device as limit devices, with a measurement accuracy of ±0.5mm. The position of the sensor is the predetermined height after jacking, and the height deviation is controlled within ±1.5mm. After precise debugging and calibration, it is ensured that the canopy structure can accurately detect whether it has reached the specified position. The sensor and the retractable top support are connected by a double-layer shielded cable, and the grounding resistance of the shielding layer is 0.3Ω, realizing automatic control and feedback adjustment functions. The pole is made of 316L stainless steel with a diameter of 60mm and a height of 1.8 meters. The pole and the load-bearing device are connected by welding, and the connection part is strength-checked to ensure its stability.

[0129] Electromagnetic lifting operation:

[0130] The spiral hollow coil is energized, and the current gradually increases from zero at a rate of 6A / s, driving the canopy structure to rise slowly and uniformly at a speed of 6mm / s. The real-time monitoring system such as displacement sensors, stress sensors and high-definition video monitoring is used to closely monitor the rising dynamics of the canopy structure. The monitoring data acquisition frequency is 15Hz to ensure that the rising process is smooth and without abnormalities, and the vibration amplitude of the canopy structure does not exceed ±1.5mm.

[0131] When the canopy structure reaches the predetermined position, the sensor sends out an audible and visual alarm signal within 0.3s, and the operator gradually reduces the current at a rate of 4A / s until the canopy structure is in a static suspended state and stops current adjustment. At this time, wait for the retractable top support to reach the predetermined position at a speed of 12mm / s, and then continue to slowly reduce the current at a rate of 3A / s until the power is completely cut off. At the same time, the retractable top support extends the jacking support device to the bottom of the canopy structure, and the fitting gap is controlled within ±0.8mm to form a stable support structure.

[0132] Welding and fixing of canopy: Argon arc welding is used to weld the lower and upper parts of the canopy. The welding material is ER4043 welding wire, which complies with relevant national standards. The welds are visually inspected and X-rayed. The appearance inspection complies with industry standards, and the qualified level of non-destructive testing is level 1, ensuring the quality of the welds. The lower part of the canopy is connected to the deck structure of the pedestrian overpass by M22 high-strength bolts, with a preload of 200kN to ensure the firmness and stability of the connection. The size and position accuracy deviation of the connection parts are controlled within ±1.5mm.

[0133] Device resetting and repeated operation: After completing the welding and fixing of the canopy, ensure that all electrical equipment is powered off for 45 minutes, remove the tripod positioning, use a small tractor to push the load-bearing device to the next lifting position at a pushing speed of 4mm / s, and repeat the lifting operation according to the above steps until the lifting and installation task of the entire pedestrian overpass canopy is completed. During the repeated operation, each device should be inspected and maintained regularly. If the insulating paint is found to be peeling, it should be repainted in time to ensure that the performance of the device is always in good condition and meets the construction requirements.

[0134] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A construction method for electromagnetic lifting of a pedestrian bridge canopy, characterized in that: The following steps are involved: Step S1, cutting the canopy structure into two parts, the cutting position can be selected but not limited to the center of the canopy structure, and the incision is a horizontal incision; Step S2, block the traffic at the jacking position, level the foundation at the operation position and check the bearing capacity, and place a cordon around it; Step S3, measuring and laying out, positioning the pre-lifting structure at the projection position on the ground, laying the slide rails and sleepers to form a sliding device, connecting the slide rails and the ground with anchor bolts, and arranging the sleepers in a triangle; Step S4, installing a load-bearing device above the sliding device, the load-bearing device comprising an upper crossbeam, a lower load-bearing tire frame, a retractable top support inside the tire frame, and a track pulley; the outer surface of the load-bearing device is painted with insulating paint, and a lifting device is installed between adjacent load-bearing devices and a spiral hollow coil is placed; Step S5, installing a positioning tripod at the track pulley of the sliding device; Step S6, placing multiple groups of spiral hollow coils above the lifting device, and the direction of the current is counterclockwise; Step S7, installing a supporting device on the top surface of the carrying device, wherein the supporting device is connected to a retractable top support in the carrying device through a reserved hole; Step S8, installing limiting devices on both sides of the carrying device, including sensors and upright poles, and the sensors are connected to the retractable top support; Step S9, energize the coil to make the electromagnetic force lift the canopy structure to a predetermined position, reduce the current after the sensor alarms, and extend the retractable jacking support device out of the lifting support device until the power is completely cut off; Step S10, welding the lower half of the canopy to the upper half, and connecting them to the deck structure of the pedestrian bridge; Step S11, after the power is completely turned off for half an hour, the tripod is removed for positioning, and the bearing device is pushed to repeat the lifting process until the lifting operation of the entire canopy is completed.

2. The construction method of electromagnetic lifting of a pedestrian bridge canopy according to claim 1 is characterized in that: The crossbeam of the bearing device is made of hot-rolled H-shaped steel and rigidly connected, the tire frame is made of steel pipe, and the diagonal braces and horizontal braces between the brackets are made of angle steel.

3. The construction method of electromagnetic lifting of a pedestrian bridge canopy according to claim 1 is characterized in that: The supporting device is made of insulating material.

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