【In-depth Discussion on Modular Installation of HaiChuan】Overall Installation of 1300-ton Modular Corridor

The lifting speed is only 5-6 meters per hour; the steel corridor rises slowly, with an elevation increase of just 5 to 6 meters per hour. The project team remains highly focused, constantly monitoring the lifting process to ensure that the load is distributed evenly across all lifting points and that the overall posture of the corridor stays stable, allowing no room for any slackness

Peng Yibiao, Jiangsu Chuangsheng Project Management Co., Ltd. Abstract: This paper provides a brief introduction to the construction process involved in the overall lifting of steel walkways. By referring to actual lifting examples, it focuses on the lifting plan and the key points for safety control during the lifting process, and discusses various safety control techniques to ensure the safety of such overall lifts. 　　Keywords: steel corridor ； Overall lifting improvement ； Key safety control points: The steel corridor in this project is located at the intersection of 1-11*1-14 and axes 1-E*1-G, on the 20th floor, between the office main buildings at 18F and 22F. The total weight of the truss is 180 T, with a structural span of 25.5 meters and a width of 17.2 meters. The elevation of the lower chord axis of the truss is 76.9 meters, while that of the upper chord axis is 80.8 meters; the net height of the truss is 3.9 meters. It consists of 3 trusses: 2 side beams along the 1-G axis and 1-E axis, and 1 middle beam along the 1-F axis. Each beam is composed of upper and lower chord beams serta vertical bracing members, all of which are box-shaped steel beams with dimensions of 400*600*40*60 and 400*600*40*40 respectively. Between each beam, there are horizontal support beams, horizontal diagonal support beams, and secondary beams, all of which are made of I-beam steel. Corrugated steel sheets are installed on the 20th floor level (at an elevation of 77.5 meters), with 150 mm thick cast-in-place concrete. 　　I. Key safety control points in the construction preparation phase 1. The overall lifting height of the steel walkway in this project is 76.9 meters, and lifting is carried out using unconventional equipment; this constitutes a construction task of considerable scale and high risk. A safety supervision team composed of the project director, professional steel structure supervision engineers, and safety supervision engineers defines the responsibilities of each supervisor, with the project director serving as the person in charge. In accordance with the provisions of Document Jianzhi [2009] No. 87 issued by the Ministry of Housing and Urban-Rural Development, construction units are required to prepare a specialized construction plan for the overall lifting and hoisting work, and to organize expert groups to review and evaluate it. 　　2. For the overall lifting and hoisting project of the steel corridor, the chief supervision engineer assigns specialized supervision engineers to prepare targeted implementation details for supervision. Safety supervision personnel are assigned to oversee the entire process of steel structure hoisting, and a detailed supervision briefing is provided to the construction unit prior to commencement of work. 　　3. Verify the qualifications of the lifting unit, its safety production license, the presence of qualified safety management personnel, and ensure that all workers performing special types of work hold the necessary certificates; the number of personnel must be sufficient to meet the requirements for lifting operations. 　　4. Inspect the establishment and implementation of the construction unit’s safety management system as well as various safety management regulations. 　　5. Check that the lifting machinery, steel strands, hooks, jacks, and locking devices come with inspection certificates to ensure safe lifting. Hydraulic jacks come with valid third-party calibration certificates. 　　6. Review the overall special construction plan for lifting, with a focus on the following aspects: (1) The general layout plan of the construction site and the schematic diagram of the assembly sequence. 　　(2) Description of the construction process flow and schematic diagram. 　　(3) Performance of the main construction machinery and equipment, including truck cranes, welding machines, levels, theodolites, torque wrenches, jacks, steel strands, as well as the management systems for mechanical maintenance. 　　(4) Safety measures for lifting components such as edge girders, middle beams, diagonal braces, horizontal support beams, support columns, secondary beams, and temporary supports. 　　(5) Schematic diagram of lifting points for large steel components such as beams, supports, and columns. 　　(6) Calculation sheets for the forces and deformations experienced during lifting of steel strands, cantilever lifting brackets for end and intermediate box-shaped steel beams, formwork, rotary lifting devices, and steel trusses. 　　(7) Emergency rescue plan for the construction site and lifting equipment. 　　7. Verification of the review and approval procedures for the special construction plan: The construction unit organized relevant personnel to prepare a special lifting construction plan, taking into account factors such as the on-site working conditions, welding quality, overall stability, project timeline, and safety. A group of five experts was brought in to review and evaluate this plan; after numerous revisions and improvements, it was finally approved by the experts for implementation based on the improved version of the plan. The following implementation plan has been determined: manufacture 8 jigs that are 1.8 meters high. On-site, a 25T truck crane was used for lifting. On the tire frame, the components were assembled into a single unit following a logical lifting sequence; temporary fixing measures were employed to assemble, fix, and weld each component one by one. After the 3 beams are assembled, 6 lifting points are used, and hydraulic jacks are employed to lift them as a unit to the installation location, where they are connected to the pre-installed brackets at height. Suspension brackets 4.95 meters in length are pre-installed at the upper chord of the steel truss on axes 1-11, while suspension brackets 1.6 meters in length are pre-installed at the upper chord of axes 1-14 to serve as lifting anchors. Fixing members are added as needed before the overall lifting process to enhance the structural stability during lifting. 　　The project supervision director and safety supervision engineer actively participated in the expert group’s review and evaluation of the special construction plan. After modifications and improvements were made, the head of the expert group signed to give approval, followed by the technical supervisor of the construction company signing as well and affixing the company’s official seal. The project’s chief supervision engineer reviews and signs it, and the supervision company’s official seal is affixed. The project leader of the construction unit shall review and sign, and affix the official seal of the construction unit’s enterprise. 　　8. For the safety training at three levels, safety training records, and safety technical briefing records of personnel involved in on-site lifting operations, responsibility must be assigned to specific individuals, with signatures for confirmation. 　　II. Key points for safety control during the lifting process 1. Check the implementation and enforcement of the specific construction plan, with a focus on the following aspects. 　　(1) The on-site fabrication of the jig and its support reinforcement meet the requirements of the special construction plan. A total of 3 support frames are arranged, providing 9 support points in total, all of which are located below the lower chord of the main truss. The jig is made using H-shaped steel 400*200*8*11 to form supports that are 1.5 m long, 1.0 m wide, and 1.8 m high, with their axes aligned as closely as possible with those of the columns and beams in the basement floor. A 10mm thick steel plate is laid as a leveling layer below to ensure that the top surfaces are at the same level. Based on the stability checks of the shoring structure, the maximum reaction forces at each support point, when converted into a uniformly distributed load, require reinforcement of the 450-mm-thick civil air defense roof. A full-scale scaffold should be erected at the support locations, with vertical pole spacing of 300*300 mm and horizontal step spacing of 1.0 meter. The adjustable height of the top support is 200 mm, while the length and width of the scaffold are both 2.4 meters. Upon inspection and acceptance by the supervisor, the flatness and overall stability of the jigs fabricated and assembled on site meet the support requirements for the steel truss. 　　(2) Check the structure of the lifting brackets for the side truss frames and those of the intermediate truss frames. Given that the anchor legs at the site are directly connected to the main steel-concrete structure, the special construction plan includes calculations to enhance the load-bearing capacity and stiffness of these anchor legs. Due to the additional bending moments generated by the structure of the steel box anchor legs, the static equivalence principle is applied in the calculations. Using a 3D finite element model in Midas/Gen software, the most unfavorable loads are applied to verify the deflection and stress levels of each anchor leg; the results meet the requirements for construction safety. The project supervision personnel inspected each of the edge trusses, the middle truss, as well as the structure and installation of the 6 lifting brackets one by one, and found that all met the requirements of the specific construction plan. 　　(3) Setting of elevation points and reinforcement structure. In this truss project, the 6 lifting points are located on the 21st floor. At the cantilevered ends of the upper chord beams of the two side trusses at axes 1-E and 1-G, steel box brackets are welded as supports for a 60T jack. The lowering points use rotary cranes, which are installed at both ends of the upper chord of the steel truss; each jack is equipped with 4 steel strands of grade 1860 with a diameter of ∮15.2. For the 1-F axis, one intermediate truss utilizes the cantilevered section of the upper chord of the steel truss as a support for two 60T jacks; each jack is equipped with 4 strands of 1860 grade steel wires with a diameter of ∮15.2. Lifting fixtures are used at the lower suspension points, which are located at both ends of the lower chord of the truss, with 2 sets of such fixtures per truss. A total of 6 lifting platforms, 8 jacks, and 32 steel strands. The selection of lifting points took into account the characteristics of the structural loading system; reinforcement members were added between the upper and lower chords to minimize any changes to the principles of the loading system. During the lifting process, the structural stresses and deformations could be kept under control, and the layout of the lifting points met the requirements of the specific construction plan. 　　Details of the lifting points for the axial frames at axes 1-11 and 1-14, as well as those for the intermediate truss frames, along with the reinforcement structures; these serve as working platforms for the lifting jacks, ensuring that the required load-bearing capacity and stiffness are met, thereby guaranteeing the safety of the lifting process and the smooth alignment and closure of the structures. The triangular trusses formed by the left and right half-spans of the steel truss serve as the lifting brackets at this lifting point. To reduce the vertical deformation of these brackets, diagonal braces are installed above them; these braces are made of I25 steel beams, and they form angles of 45° and 68° with the axis of the upper chord of the lifting brackets, being welded to the embedded steel plates. For categorized searches of journal articles, turn to the Journal Library. To prevent deflection and instability of the lifting brackets outside their lifting plane, reinforcing corner braces are installed within the floor plane of the upper chord members of these brackets; these corner braces are made of H-shaped steel beams, with an angle of 30° between them and the axis of the upper chord members, and they are welded to the pre-installed steel plates. To reduce the large concentrated forces acting on the cross-sectional area of the upper chord of the lifting bracket during lifting, which could cause twisting or warping of the section, transverse end plates are welded at the section to close off the end face of the bracket. The details of each lifting point and the reinforcement methods meet the requirements of the special construction plan. 　　(4) Based on the calculations of the maximum tensile stress of the lifting steel strands as specified in the special construction plan, and taking into account the amplification factor of dynamic loads during the lifting process – a safety amplification factor of 1.5 times is applied. Two 60T hydraulic jacks are used as lifting equipment at a single point on the intermediate truss; after further verification, a total of 8 steel strands of grade 1860 with a diameter of 15.2 mm are utilized. 　　(5) Verification of rotating lifting gear. To ensure the safety and reliability of the pin-type lifting device during the lifting process, its load-bearing capacity is checked. The upper ear plate, lower ear plate, pin shaft, as well as the welds between the lower ear plate and the lower chord member were all rechecked. Through modeling and detailed calculations, it was confirmed that both the maximum tensile stress and maximum deformation meet the requirements for construction. 　　(6) Overall structural stability of the steel truss. Taking into account the self-weight of the steel truss, the secondary steel beams, profiled steel sheets, etc., a safety factor of 1.5 was adopted. Through finite element analysis based on modeling, it was determined that the maximum deflection of the steel truss is sufficient to ensure the safety of lifting the assembled truss as a whole. The maximum tensile stresses at the upper and lower edges of the steel truss section are both less than the yield strength of the Q345 steel used in the trusses of this project. Based on the comprehensive verification of all members of the truss, the load-bearing capacity, stiffness, and deformation of the assembled truss structure meet the requirements for safety and precision during lifting. 　　2. Technologies and equipment for synchronized overall improvement. This project employs 6-point synchronous lifting. For the side trusses 1-E and 1-G, lifting points are installed at both ends of the upper chord; one 60T hydraulic jack is used as the lifting device at each lifting point. The lowering points are located on the upper chord of the steel structure, and lifting is carried out gradually through steel cables ； The intermediate truss 1-F axis has lifting points at both ends of the upper chord; two 60T hydraulic jacks are installed at each lifting point as lifting equipment. The lowering points are located on the lower chord of the steel structure, and lifting is carried out gradually by using steel cables for tensioning. Each jack is fitted with 4 steel strands, in a combination of 2 left-handed and 2 right-handed strands. Each lower lifting point has two 4-hole anchor plates, with the anchor plates being of the OVM M15-4 type. The hydraulic jack has a through-type structure, with steel strands serving as the lifting rigging. The entire lifting equipment is safe and reliable, has a low weight, and is easy to transport, install, and dismantle. During the lifting process, one oil pump is used to control multiple jacks simultaneously, ensuring that the lifting speed of the jacks on the same side remains consistent. The lifting speed of the jacks on the other side is regulated uniformly via walkie-talkies, thereby ensuring synchronization, stability, and safety during the lifting process. 　　3. During the trial lift, monitor and check parameters such as the position of various points and the load ； The lifting height is controlled at approximately 20 cm. After the trial lift is completed, the construction unit is required to prepare a summary of the trial lift, assessing whether the equipment is operating properly ； Assess the level of organizational coordination, and evaluate whether the command system functions smoothly as well as whether the operators and implementers work together efficiently ； Measure the changes in the horizontal and vertical displacements of the steel truss, and compare them with those before the trial lift. The trial lifting for this project went well. 　　4. During the overall lifting process, supervision personnel are present throughout to inspect the lifting jacks, the lifting bracket structure, and weather conditions. The construction unit is required to assign a person to each lifting point to monitor the movement at that location. In the event of issues such as misalignment of the point, breakage of the steel strands, or unanchoring, lifting must be stopped immediately; a thorough inspection and repair must be carried out before lifting can resume, in order to ensure safety during the lifting process. 　　5. Overall lifting and closing. All lifting personnel involved in this project use walkie-talkies to coordinate their actions and ensure unified control, while strengthening monitoring at various points during the lifting process. During lifting, professional rigging personnel are present at each jack location to monitor the lifting height of the jack cylinders; once the cylinders have risen by 200 mm, they promptly inform the oil pump operator to close the oil valve. One oil pump controls 4 jacks, ensuring that the lifting speed of the jacks on the same side is exactly the same. During lifting, there is a slight deviation due to differences in the retraction amount of the fixtures; appropriate individual adjustments are made based on the deviation measured on-site between the clamping piece and the scale. After raising it to the design elevation, lock the upper and lower anchor plates of all jacks, and then close the steel truss. Once lifted into place, to prevent swaying or shaking due to wind forces acting horizontally, it is secured using a chain block before being closed. In the event of local misalignment, use jacks to adjust the displacement in the span direction of the truss, and use chain blocks to adjust the displacement in the width direction. During the closing process, the tension of each member is adjusted using chain blocks, and the weld intervals at both ends are determined on-site based on actual conditions. Immediately after closing, install the diagonal braces and horizontal diagonal braces. 　　6. Unload after the corridor is lifted into place as a whole. The overall installation and welding of the steel walkway have been completed, forming the designed spatial structure; its strength and stability are sufficient to enable it to bear loads independently. The horizontal and diagonal supports have also been welded, and the butt welds have passed inspection. Once all inspections and approvals are completed, the entire truss can be unloaded. Diagonal symmetry with staged unloading, 25% at a time. 　　III. Key aspects for the overall improvement of process technology, measurement, closure, and safety control 1. Installation of the lifting cylinder. When lifting the cylinder, pay attention to safety ； Install the ground anchor structure on the lifted structure ； Install the lifting cylinder. When installing the lifting cylinder and the ground anchor bracket, ensure accurate positioning ； 　　2. Installation of steel strands and ground anchors. Cut the steel strands according to the designed length ； Pass the steel strand from top to bottom through the guide anchor, upper anchor, and lower anchor (safety anchor) rings ； The steel strands are inserted into the lifting anchor through the comb guide plates ； 　　3. Hydraulic system installation. Install a hydraulic jack on the lifting platform and connect the hydraulic hoses. Check the hydraulic oil and prepare spare oil. 　　4. Overall improvement of equipment debugging. Equipment commissioning is a very crucial step, which is carried out from the following aspects: (1) Commissioning of the hydraulic pump station. The hydraulic pump station is powered on to carry out oil feeding and oil collection operations, and it is checked to ensure that all components of the pump station are functioning properly. 　　(2) Improve cylinder debugging. Check that both the upper and lower anchors of the cylinder are in a tightly secured state ； After the anchor is released, start the main pump to initiate the extension of the cylinder; during this extension process, carry out a shutdown operation, and observe whether the cylinder stops. If it does stop, it indicates that the operation is functioning properly ； A retraction command is given; a shut-off action is initiated during retraction, and the cylinder coming to a stop indicates that the operation is normal. Move the cylinder back and forth several times, retract it to the bottom, and secure it. Stop the pump station after the cylinder has been properly inspected. 　　5. The overall safety protection devices of the equipment must be complete, sensitive, and reliable. All types of mechanical equipment must go through installation and acceptance procedures, with safety operation procedures and nameplates indicating the person in charge of the equipment displayed in visible locations. Strictly implement the shift handover system and keep proper records of it. 　　6. It is strictly prohibited to overload or operate the equipment in a faulty condition; maintenance is not allowed during operation. When the operator leaves the machine or there is a power outage during operation, the power supply must be disconnected. 　　7. Qualified products must be used for lifting gear. Steel strands shall ensure a sufficient safety factor. Those with surface wear, corrosion, or wire breaks exceeding the standards, or those with severe bends, broken strands, or exposed oil cores must not be used. 　　IV. Key Safety Control Points for Work at Heights 　　1. After the steel walkway is lifted into place, check the firmness and stability of the operating platform; construction workers may stand there only after it has been confirmed to be safe. Safety equipment such as helmets, safety belts, and safety shoes must be available in sufficient quantities, and they must be worn as required. When working at heights, safety belts must be worn as required; it is strictly prohibited to work without a belt or with a belt that is not securely fastened. The seat belt should be fastened to a main structure that will not slip. 　　2. No one shall stay below the working height. Workers should wear safety helmets. It is strictly prohibited to throw tools and materials up or down ； It is strictly prohibited to place tools or materials on crossbars or other objects that are not stable enough to hold them. 　　3. Before installing components such as nodes, horizontal support rods, and upper and lower chord beams in high-altitude work, select an appropriate working area and path to ensure personal safety; it is prohibited to carry heavy equipment or to climb heights while carrying cables or pulling overhead wires. High-altitude work must not be carried out during heavy rain or winds of force 6 or above. 　　4. Various mechanical and electrical equipment used for work at heights, as well as facilities such as cableways, wind ropes, and hoists, must be handled in accordance with relevant regulations. A designated person should be assigned to carry out regular inspections and repairs, especially after strong winds, heavy rain, or thunderstorms. 　　5. For communication and command between workers at heights and those on the ground, there should be uniformly specified signals, flag signals, gestures, whistles, or walkie-talkies to be used. Shouting cannot replace command. 　　6. Vertical work and fall prevention measures: To prevent accidents caused by falling objects from concurrent operations, a horizontal safety net is installed under the lower flange of the lower steel beam at the construction site of the steel structure. If there are voids in the plane, a horizontal grid needs to be installed in those voids. 　　7. A life line should be installed for work at edges, and operators should attach their safety belts to this life line. A ￠10mm steel wire rope is used as the lifeline. 　　Conclusion The steel corridor in this project is located between the tops of two main office buildings; it involves the lifting of a high-rise, large-scale steel structure, with a considerable lifting height, and the lifting process took 3 days. Throughout the entire process, appropriate safety control measures were implemented, ensuring good safety and reliability. The steel structure project not only had its quality guaranteed but also saw time savings, and moreover

Peng Yibiao, Jiangsu Chuangsheng Project Management Co., Ltd. Abstract: This paper provides a brief introduction to the construction process involved in the overall lifting of steel walkways. By referring to actual lifting examples, it focuses on the lifting plan and the key points for safety control during the lifting process, and discusses various safety control techniques to ensure the safety of such overall lifts. 　　Keywords: steel corridor ； Overall lifting improvement ； Key safety control points: The steel corridor in this project is located at the intersection of 1-11*1-14 and axes 1-E*1-G, on the 20th floor, between the office main buildings at 18F and 22F. The total weight of the truss is 180 T, with a structural span of 25.5 meters and a width of 17.2 meters. The elevation of the lower chord axis of the truss is 76.9 meters, while that of the upper chord axis is 80.8 meters; the net height of the truss is 3.9 meters. It consists of 3 trusses: 2 side beams along the 1-G axis and 1-E axis, and 1 middle beam along the 1-F axis. Each beam is composed of upper and lower chord beams serta vertical bracing members, all of which are box-shaped steel beams with dimensions of 400*600*40*60 and 400*600*40*40 respectively. Between each beam, there are horizontal support beams, horizontal diagonal support beams, and secondary beams, all of which are made of I-beam steel. Corrugated steel sheets are installed on the 20th floor level (at an elevation of 77.5 meters), with 150 mm thick cast-in-place concrete. 　　I. Key safety control points in the construction preparation phase 1. The overall lifting height of the steel walkway in this project is 76.9 meters, and lifting is carried out using unconventional equipment; this constitutes a construction task of considerable scale and high risk. A safety supervision team composed of the project director, professional steel structure supervision engineers, and safety supervision engineers defines the responsibilities of each supervisor, with the project director serving as the person in charge. In accordance with the provisions of Document Jianzhi [2009] No. 87 issued by the Ministry of Housing and Urban-Rural Development, construction units are required to prepare a specialized construction plan for the overall lifting and hoisting work, and to organize expert groups to review and evaluate it. 　　2. For the overall lifting and hoisting project of the steel corridor, the chief supervision engineer assigns specialized supervision engineers to prepare targeted implementation details for supervision. Safety supervision personnel are assigned to oversee the entire process of steel structure hoisting, and a detailed supervision briefing is provided to the construction unit prior to commencement of work. 　　3. Verify the qualifications of the lifting unit, its safety production license, the presence of qualified safety management personnel, and ensure that all workers performing special types of work hold the necessary certificates; the number of personnel must be sufficient to meet the requirements for lifting operations. 　　4. Inspect the establishment and implementation of the construction unit’s safety management system as well as various safety management regulations. 　　5. Check that the lifting machinery, steel strands, hooks, jacks, and locking devices come with inspection certificates to ensure safe lifting. Hydraulic jacks come with valid third-party calibration certificates. 　　6. Review the overall special construction plan for lifting, with a focus on the following aspects: (1) The general layout plan of the construction site and the schematic diagram of the assembly sequence. 　　(2) Description of the construction process flow and schematic diagram. 　　(3) Performance of the main construction machinery and equipment, including truck cranes, welding machines, levels, theodolites, torque wrenches, jacks, steel strands, as well as the management systems for mechanical maintenance. 　　(4) Safety measures for lifting components such as edge girders, middle beams, diagonal braces, horizontal support beams, support columns, secondary beams, and temporary supports. 　　(5) Schematic diagram of lifting points for large steel components such as beams, supports, and columns. 　　(6) Calculation sheets for the forces and deformations experienced during lifting of steel strands, cantilever lifting brackets for end and intermediate box-shaped steel beams, formwork, rotary lifting devices, and steel trusses. 　　(7) Emergency rescue plan for the construction site and lifting equipment. 　　7. Verification of the review and approval procedures for the special construction plan: The construction unit organized relevant personnel to prepare a special lifting construction plan, taking into account factors such as the on-site working conditions, welding quality, overall stability, project timeline, and safety. A group of five experts was brought in to review and evaluate this plan; after numerous revisions and improvements, it was finally approved by the experts for implementation based on the improved version of the plan. The following implementation plan has been determined: manufacture 8 jigs that are 1.8 meters high. On-site, a 25T truck crane was used for lifting. On the tire frame, the components were assembled into a single unit following a logical lifting sequence; temporary fixing measures were employed to assemble, fix, and weld each component one by one. After the 3 beams are assembled, 6 lifting points are used, and hydraulic jacks are employed to lift them as a unit to the installation location, where they are connected to the pre-installed brackets at height. Suspension brackets 4.95 meters in length are pre-installed at the upper chord of the steel truss on axes 1-11, while suspension brackets 1.6 meters in length are pre-installed at the upper chord of axes 1-14 to serve as lifting anchors. Fixing members are added as needed before the overall lifting process to enhance the structural stability during lifting. 　　The project supervision director and safety supervision engineer actively participated in the expert group’s review and evaluation of the special construction plan. After modifications and improvements were made, the head of the expert group signed to give approval, followed by the technical supervisor of the construction company signing as well and affixing the company’s official seal. The project’s chief supervision engineer reviews and signs it, and the supervision company’s official seal is affixed. The project leader of the construction unit shall review and sign, and affix the official seal of the construction unit’s enterprise. 　　8. For the safety training at three levels, safety training records, and safety technical briefing records of personnel involved in on-site lifting operations, responsibility must be assigned to specific individuals, with signatures for confirmation. 　　II. Key points for safety control during the lifting process 1. Check the implementation and enforcement of the specific construction plan, with a focus on the following aspects. 　　(1) The on-site fabrication of the jig and its support reinforcement meet the requirements of the special construction plan. A total of 3 support frames are arranged, providing 9 support points in total, all of which are located below the lower chord of the main truss. The jig is made using H-shaped steel 400*200*8*11 to form supports that are 1.5 m long, 1.0 m wide, and 1.8 m high, with their axes aligned as closely as possible with those of the columns and beams in the basement floor. A 10mm thick steel plate is laid as a leveling layer below to ensure that the top surfaces are at the same level. Based on the stability checks of the shoring structure, the maximum reaction forces at each support point, when converted into a uniformly distributed load, require reinforcement of the 450-mm-thick civil air defense roof. A full-scale scaffold should be erected at the support locations, with vertical pole spacing of 300*300 mm and horizontal step spacing of 1.0 meter. The adjustable height of the top support is 200 mm, while the length and width of the scaffold are both 2.4 meters. Upon inspection and acceptance by the supervisor, the flatness and overall stability of the jigs fabricated and assembled on site meet the support requirements for the steel truss. 　　(2) Check the structure of the lifting brackets for the side truss frames and those of the intermediate truss frames. Given that the anchor legs at the site are directly connected to the main steel-concrete structure, the special construction plan includes calculations to enhance the load-bearing capacity and stiffness of these anchor legs. Due to the additional bending moments generated by the structure of the steel box anchor legs, the static equivalence principle is applied in the calculations. Using a 3D finite element model in Midas/Gen software, the most unfavorable loads are applied to verify the deflection and stress levels of each anchor leg; the results meet the requirements for construction safety. The project supervision personnel inspected each of the edge trusses, the middle truss, as well as the structure and installation of the 6 lifting brackets one by one, and found that all met the requirements of the specific construction plan. 　　(3) Setting of elevation points and reinforcement structure. In this truss project, the 6 lifting points are located on the 21st floor. At the cantilevered ends of the upper chord beams of the two side trusses at axes 1-E and 1-G, steel box brackets are welded as supports for a 60T jack. The lowering points use rotary cranes, which are installed at both ends of the upper chord of the steel truss; each jack is equipped with 4 steel strands of grade 1860 with a diameter of ∮15.2. For the 1-F axis, one intermediate truss utilizes the cantilevered section of the upper chord of the steel truss as a support for two 60T jacks; each jack is equipped with 4 strands of 1860 grade steel wires with a diameter of ∮15.2. Lifting fixtures are used at the lower suspension points, which are located at both ends of the lower chord of the truss, with 2 sets of such fixtures per truss. A total of 6 lifting platforms, 8 jacks, and 32 steel strands. The selection of lifting points took into account the characteristics of the structural loading system; reinforcement members were added between the upper and lower chords to minimize any changes to the principles of the loading system. During the lifting process, the structural stresses and deformations could be kept under control, and the layout of the lifting points met the requirements of the specific construction plan. 　　Details of the lifting points for the axial frames at axes 1-11 and 1-14, as well as those for the intermediate truss frames, along with the reinforcement structures; these serve as working platforms for the lifting jacks, ensuring that the required load-bearing capacity and stiffness are met, thereby guaranteeing the safety of the lifting process and the smooth alignment and closure of the structures. The triangular trusses formed by the left and right half-spans of the steel truss serve as the lifting brackets at this lifting point. To reduce the vertical deformation of these brackets, diagonal braces are installed above them; these braces are made of I25 steel beams, and they form angles of 45° and 68° with the axis of the upper chord of the lifting brackets, being welded to the embedded steel plates. For categorized searches of journal articles, turn to the Journal Library. To prevent deflection and instability of the lifting brackets outside their lifting plane, reinforcing corner braces are installed within the floor plane of the upper chord members of these brackets; these corner braces are made of H-shaped steel beams, with an angle of 30° between them and the axis of the upper chord members, and they are welded to the pre-installed steel plates. To reduce the large concentrated forces acting on the cross-sectional area of the upper chord of the lifting bracket during lifting, which could cause twisting or warping of the section, transverse end plates are welded at the section to close off the end face of the bracket. The details of each lifting point and the reinforcement methods meet the requirements of the special construction plan. 　　(4) Based on the calculations of the maximum tensile stress of the lifting steel strands as specified in the special construction plan, and taking into account the amplification factor of dynamic loads during the lifting process – a safety amplification factor of 1.5 times is applied. Two 60T hydraulic jacks are used as lifting equipment at a single point on the intermediate truss; after further verification, a total of 8 steel strands of grade 1860 with a diameter of 15.2 mm are utilized. 　　(5) Verification of rotating lifting gear. To ensure the safety and reliability of the pin-type lifting device during the lifting process, its load-bearing capacity is checked. The upper ear plate, lower ear plate, pin shaft, as well as the welds between the lower ear plate and the lower chord member were all rechecked. Through modeling and detailed calculations, it was confirmed that both the maximum tensile stress and maximum deformation meet the requirements for construction. 　　(6) Overall structural stability of the steel truss. Taking into account the self-weight of the steel truss, the secondary steel beams, profiled steel sheets, etc., a safety factor of 1.5 was adopted. Through finite element analysis based on modeling, it was determined that the maximum deflection of the steel truss is sufficient to ensure the safety of lifting the assembled truss as a whole. The maximum tensile stresses at the upper and lower edges of the steel truss section are both less than the yield strength of the Q345 steel used in the trusses of this project. Based on the comprehensive verification of all members of the truss, the load-bearing capacity, stiffness, and deformation of the assembled truss structure meet the requirements for safety and precision during lifting. 　　2. Technologies and equipment for synchronized overall improvement. This project employs 6-point synchronous lifting. For the side trusses 1-E and 1-G, lifting points are installed at both ends of the upper chord; one 60T hydraulic jack is used as the lifting device at each lifting point. The lowering points are located on the upper chord of the steel structure, and lifting is carried out gradually through steel cables ； The intermediate truss 1-F axis has lifting points at both ends of the upper chord; two 60T hydraulic jacks are installed at each lifting point as lifting equipment. The lowering points are located on the lower chord of the steel structure, and lifting is carried out gradually by using steel cables for tensioning. Each jack is fitted with 4 steel strands, in a combination of 2 left-handed and 2 right-handed strands. Each lower lifting point has two 4-hole anchor plates, with the anchor plates being of the OVM M15-4 type. The hydraulic jack has a through-type structure, with steel strands serving as the lifting rigging. The entire lifting equipment is safe and reliable, has a low weight, and is easy to transport, install, and dismantle. During the lifting process, one oil pump is used to control multiple jacks simultaneously, ensuring that the lifting speed of the jacks on the same side remains consistent. The lifting speed of the jacks on the other side is regulated uniformly via walkie-talkies, thereby ensuring synchronization, stability, and safety during the lifting process. 　　3. During the trial lift, monitor and check parameters such as the position of various points and the load ； The lifting height is controlled at approximately 20 cm. After the trial lift is completed, the construction unit is required to prepare a summary of the trial lift, assessing whether the equipment is operating properly ； Assess the level of organizational coordination, and evaluate whether the command system functions smoothly as well as whether the operators and implementers work together efficiently ； Measure the changes in the horizontal and vertical displacements of the steel truss, and compare them with those before the trial lift. The trial lifting for this project went well. 　　4. During the overall lifting process, supervision personnel are present throughout to inspect the lifting jacks, the lifting bracket structure, and weather conditions. The construction unit is required to assign a person to each lifting point to monitor the movement at that location. In the event of issues such as misalignment of the point, breakage of the steel strands, or unanchoring, lifting must be stopped immediately; a thorough inspection and repair must be carried out before lifting can resume, in order to ensure safety during the lifting process. 　　5. Overall lifting and closing. All lifting personnel involved in this project use walkie-talkies to coordinate their actions and ensure unified control, while strengthening monitoring at various points during the lifting process. During lifting, professional rigging personnel are present at each jack location to monitor the lifting height of the jack cylinders; once the cylinders have risen by 200 mm, they promptly inform the oil pump operator to close the oil valve. One oil pump controls 4 jacks, ensuring that the lifting speed of the jacks on the same side is exactly the same. During lifting, there is a slight deviation due to differences in the retraction amount of the fixtures; appropriate individual adjustments are made based on the deviation measured on-site between the clamping piece and the scale. After raising it to the design elevation, lock the upper and lower anchor plates of all jacks, and then close the steel truss. Once lifted into place, to prevent swaying or shaking due to wind forces acting horizontally, it is secured using a chain block before being closed. In the event of local misalignment, use jacks to adjust the displacement in the span direction of the truss, and use chain blocks to adjust the displacement in the width direction. During the closing process, the tension of each member is adjusted using chain blocks, and the weld intervals at both ends are determined on-site based on actual conditions. Immediately after closing, install the diagonal braces and horizontal diagonal braces. 　　6. Unload after the corridor is lifted into place as a whole. The overall installation and welding of the steel walkway have been completed, forming the designed spatial structure; its strength and stability are sufficient to enable it to bear loads independently. The horizontal and diagonal supports have also been welded, and the butt welds have passed inspection. Once all inspections and approvals are completed, the entire truss can be unloaded. Diagonal symmetry with staged unloading, 25% at a time. 　　III. Key aspects for the overall improvement of process technology, measurement, closure, and safety control 1. Installation of the lifting cylinder. When lifting the cylinder, pay attention to safety ； Install the ground anchor structure on the lifted structure ； Install the lifting cylinder. When installing the lifting cylinder and the ground anchor bracket, ensure accurate positioning ； 　　2. Installation of steel strands and ground anchors. Cut the steel strands according to the designed length ； Pass the steel strand from top to bottom through the guide anchor, upper anchor, and lower anchor (safety anchor) rings ； The steel strands are inserted into the lifting anchor through the comb guide plates ； 　　3. Hydraulic system installation. Install a hydraulic jack on the lifting platform and connect the hydraulic hoses. Check the hydraulic oil and prepare spare oil. 　　4. Overall improvement of equipment debugging. Equipment commissioning is a very crucial step, which is carried out from the following aspects: (1) Commissioning of the hydraulic pump station. The hydraulic pump station is powered on to carry out oil feeding and oil collection operations, and it is checked to ensure that all components of the pump station are functioning properly. 　　(2) Improve cylinder debugging. Check that both the upper and lower anchors of the cylinder are in a tightly secured state ； After the anchor is released, start the main pump to initiate the extension of the cylinder; during this extension process, carry out a shutdown operation, and observe whether the cylinder stops. If it does stop, it indicates that the operation is functioning properly ； A retraction command is given; a shut-off action is initiated during retraction, and the cylinder coming to a stop indicates that the operation is normal. Move the cylinder back and forth several times, retract it to the bottom, and secure it. Stop the pump station after the cylinder has been properly inspected. 　　5. The overall safety protection devices of the equipment must be complete, sensitive, and reliable. All types of mechanical equipment must go through installation and acceptance procedures, with safety operation procedures and nameplates indicating the person in charge of the equipment displayed in visible locations. Strictly implement the shift handover system and keep proper records of it. 　　6. It is strictly prohibited to overload or operate the equipment in a faulty condition; maintenance is not allowed during operation. When the operator leaves the machine or there is a power outage during operation, the power supply must be disconnected. 　　7. Qualified products must be used for lifting gear. Steel strands shall ensure a sufficient safety factor. Those with surface wear, corrosion, or wire breaks exceeding the standards, or those with severe bends, broken strands, or exposed oil cores must not be used. 　　IV. Key Safety Control Points for Work at Heights 　　1. After the steel walkway is lifted into place, check the firmness and stability of the operating platform; construction workers may stand there only after it has been confirmed to be safe. Safety equipment such as helmets, safety belts, and safety shoes must be available in sufficient quantities, and they must be worn as required. When working at heights, safety belts must be worn as required; it is strictly prohibited to work without a belt or with a belt that is not securely fastened. The seat belt should be fastened to a main structure that will not slip. 　　2. No one shall stay below the working height. Workers should wear safety helmets. It is strictly prohibited to throw tools and materials up or down ； It is strictly prohibited to place tools or materials on crossbars or other objects that are not stable enough to hold them. 　　3. Before installing components such as nodes, horizontal support rods, and upper and lower chord beams in high-altitude work, select an appropriate working area and path to ensure personal safety; it is prohibited to carry heavy equipment or to climb heights while carrying cables or pulling overhead wires. High-altitude work must not be carried out during heavy rain or winds of force 6 or above. 　　4. Various mechanical and electrical equipment used for work at heights, as well as facilities such as cableways, wind ropes, and hoists, must be handled in accordance with relevant regulations. A designated person should be assigned to carry out regular inspections and repairs, especially after strong winds, heavy rain, or thunderstorms. 　　5. For communication and command between workers at heights and those on the ground, there should be uniformly specified signals, flag signals, gestures, whistles, or walkie-talkies to be used. Shouting cannot replace command. 　　6. Vertical work and fall prevention measures: To prevent accidents caused by falling objects from concurrent operations, a horizontal safety net is installed under the lower flange of the lower steel beam at the construction site of the steel structure. If there are voids in the plane, a horizontal grid needs to be installed in those voids. 　　7. A life line should be installed for work at edges, and operators should attach their safety belts to this life line. A ￠10mm steel wire rope is used as the lifeline. 　　Conclusion The steel corridor in this project is located between the tops of two main office buildings; it involves the lifting of a high-rise, large-scale steel structure, with a considerable lifting height, and the lifting process took 3 days. Throughout the entire process, appropriate safety control measures were implemented, ensuring good safety and reliability. The steel structure project not only had its quality guaranteed but also saw time savings, and moreover