1. Focus points and difficulties of on-site installation
No |
Content |
1 |
Choice of installation plan |
2 |
Assembly and hoisting of plane pipe truss and triangular steel truss |
3 |
Hoisting of V-shaped column of stadium |
4 |
Hoisting of steel structure mast of stadium |
5 |
Displacement control of steel structure after unloading of support frame |
6 |
Overall unloading measures of truss |
7 |
Coordination and management of cross construction |
8 |
Construction cooperation with the civil engineering and other professional construction teams |
9 |
Protection of finished completed buildings |
2. Analysis of Focus points and difficulties of on-site installation
No |
Focus points and difficulties |
Analysis of Focus points and difficulties |
1 |
Choice of installation plan |
The installation plan is the central program for the on-site construction of the steel structure. All production technical activities on the construction site are carried out around it. Its technological advancement determines the economic rationality of the overall plan and the realization of the construction period goals. Therefore, it is the fist priority of the on-site construction of the steel structure. |
2 |
Assembly and hoisting of plane pipe truss and triangular steel truss |
The main stress-bearing system of the steel structure project is composed of plane pipe truss and triangular steel truss, and it has the characteristics of large span and long length of the truss itself. Therefore, how to avoid the disadvantage,such as permanent deformation of the truss during the hoisting process is one of the key points of this project; and the choice of lifting method directly determines the assembly accuracy of the structure, and the quality of the assembled weld, etc., which is one of the key factors that determine the quality of the project. |
3 |
Hoisting of V-shaped column of stadium |
The V-shaped column of this project is mainly composed of a plane pipe truss with a height of 30 meters and a maximum width of 21 meters. How to control the assembly accuracy of the V-shaped column and the deformation during the lifting process is one of the key points of the installation in this project. |
4 |
Hoisting of steel structure mast of stadium |
Since the mast height of this project is 66 meters, the cross-sectional shape is triangular, and the cross-sectional height is 2.3 meters, how to reasonably choose the hoisting method of the mast is the key factor of this project. |
5 |
Displacement control of steel structure after unloading of support frame |
The radial main truss of this project is up to 45.5 meters long. When the construction state is transitioned to the design state, the structure where the support frame is installed naturally deflects, and the other structures also deform accordingly. Whether the structural state coincides with the design state after completion is an important indicator for measurement of the construction quality. |
6 |
Overall unloading measures of truss |
In order to ensure the stability of the truss structure during the installation process, and at the same time to ensure that the structure slowly transitions from the construction state to the design state, the truss must be ensured that the location is consistent with the design of the initial position through the stable force of the internal and external support after the structure is removed. During this period, a large internal force redistribution occurs in the truss structure and gradually transits to the design state. Therefore, the removal of the support frame is crucial. |
7 |
Coordination and management of cross construction |
According to the arrangement of each process of this project, roof construction and steel structure construction will be carried out simultaneously. The provision of the steel structure construction work surface is the premise for the roof construction to be proceeded smoothly. Therefore, the rational coordination of construction process for the steel structure and the metal roof is also one of the keys of this project. |
8 |
Construction cooperation with the civil engineering and other professional construction teams |
Due to its own factors in the construction of steel structures, cooperation with other professional construction teams is the guarantee for the entire construction period. |
9 |
Protection of finished completed buildings |
In order to prevent the components from colliding with the completed buildings during transportation and hoisting, so that the steel structure construction is not affected, the construction team must carry out strict precautions during the construction process. |
3. Measures of focus points and difficulties of on-site installation
3.1 Choice of installation plan
Compare a variety of installation plans, organize the expert demonstrations, and analyze the advantages and disadvantages of the project combined with the structure characteristics, construction period, construction site conditions and other factors, and select the best plan, that is, the entire stadium hood steel structure construction is divided into two construction areas, respectively for the Western District and Eastern District. In order to speed up the construction progress, two 150-ton crawler cranes are arranged on the outside of the stadium, and one 80-ton truck crane is arranged in the inside of the stadium. Each construction area is hoisted from the middle to both sides. After hoisting the steel structure in the west area, hoist the steel structure in the east area.
3.2 Measures of assembly and hoisting of truss
No |
Content |
Measures |
1 |
Assembly |
Compared to factory processing and production, due to the limitations of equipment,construction site and other factors,the quality and efficiency of on-site assembly is difficult to match. Therefore, in this project, we reduce the on-site assembly volume as much as possible, the truss should be made in the factory as much as possible, and it is docked after being transported to the site in sections. And in order to ensure the assembly precision and quality of the truss, our company specially designed the assembly tire frame according to the characteristics of the truss of this project, and set a fine adjustment device on it. |
2 |
Hoisting |
After the assembling and docking are completed on site, our company plans to use the 150-ton crawler crane and 80-ton truck crane for lifting of the main truss. In order to reduce the irreversible damage to the structure during the hoisting process, our company specially set up hoisting girder beams and fir to increase the hoisting point through such measures, increase the angle between the steel wire rope and the truss to reduce the axial pressure inside of the truss components to ensure that the truss does not cause instability during lifting. |
3.3 Hoisting measures of V-shaped column of stadium
No |
Measures |
1 |
The V-shaped column components are firstly produced in sections in the factory, and then transported to the site to be assembled into a lifting unit. In order to prevent the deformation of the V-shaped column during lifting, temporary rods are installed at the end of the V-shaped column and the lifting point for reinforcement. |
2 |
After the V-shaped column is hoisted in place, install the embedded parts on the beam of the civil engineering stand, install temporary tie rods, weld one end to the embedded parts, and connect with the V-shaped column at the other end to prevent the V-shaped column from falling to the outside. |
3 |
In order to prevent the deformation of the rod during the lifting of the V-shaped column, two rods are added horizontally and diagonally on the round column to reinforce the upper part of the V-shaped column. The lifting point is set at the middle of the end of V-shaped column. One 150-ton crawler crane and one 25-ton truck crane are adopted to achieve the lifting method of double-machine rotary lifting and single-machine lifting. And use the calculation software to analyze the construction simulation conditions. |
3.4 Hoisting measures of steel structure mast of stadium
No |
Measures |
1 |
Because the horizontal truss is assembled horizontally, it needs to be turned upright during the demoulding process. In order to prevent the truss from out-of-plane instability occurs during demoulding , two fir ties are set on the plane truss. For the stress conditions during demoulding and lifting, see "Analysis of Steel Structure Hoisting Conditions". |
2 |
The mast steel components are firstly produced in three sections in the factory, and then transported to the site for sectional assembly into a hoisting unit for complete hoisting. |
3 |
When the mast is hoisted, a 150-ton crawler crane is used for eight-point hoisting, and a 25-ton truck is hoisted at the tail. The main hoisting point is located on the upper chord. In order to adjust the inclination of the mast, a reverse link is provided on the chord of the mast, so as to adjust the inclination of the mast in time. |
3.5 Displacement control measures of steel structure after unloading of support frame
No |
Measures |
1 |
Before unloading, carry out computer simulation calculation on the unloading process of the support frame, and organize and analyze the displacement values of various parts of the structure. |
2 |
When the support frame is erected before installation, the height of the erection is pre-elevated, and the adjustment value is determined according to the calculation result. |
3 |
During the unloading process, it is necessary to strictly control the accuracy of each level of elevation control during cyclic unloading, set measurement control points, monitor the entire process of unloading, and compare with the calculation results to implement information construction management to ensure that the structural state of the final completion are consistent with the design state. |
3.6 Overall unloading measures of truss
No |
Measures |
1 |
During the unloading process, the support points in the same unloading step cannot be absolutely synchronized. The unloading order of the support points of the brackets is different. The axial force will inevitably cause increase or decrease. According to the design requirements or calculation results,the detection device (such as attaching strain gauges) should be placed on the support points of the key brackets to detect the change of the axial force of the fulcrum of the bracket to ensure the safety of the temporary bracket and truss. |
2 |
During the unloading process, it is necessary to strictly control the accuracy of each level of elevation control during cyclic unloading, set measurement control points, monitor the entire process of unloading, and compare with the calculation results to implement information construction management. |
3 |
The condition of the support frame provided by the truss is equivalent to loading the truss node, while the temporary support gradually decreases in batches, and its condition is equivalent to the uneven settlement of the support. This will cause changes and adjustments to the internal forces of the truss structure. Measures should be taken in advance for the situation where a small number of rods may be overloaded, and the reinforcing rods can be replaced in advance based on local reinforcement or calculations. In order to prevent individual support points from being concentrated, it is advisable to remove the support points according to the deflection value of the structure weight of each support point, using a partition, step-by-step descending proportionately, or using an equal-step descent method with each step not greater than 5 mm. |
3.7 Measures for coordination and management of cross-construction
No |
Content |
Measures |
1 |
Handover of work surface |
Before installing the roofing system, it is necessary to perform the handover work with the relevant professions to provide a good working surface for the metal roof installation. |
2 |
Working time division |
Before handing over the installation work surface, it is necessary to coordinate with other professions, leaving a sufficient installation cycle to ensure the quality of the construction and the target of the construction period |
3 |
Determination of construction scope |
During the roof installation process, some working surfaces may have multiple professional joint constructions at the same time. The construction scope of each major should be clearly divided in time to ensure the smooth progress of construction. |
3.8 Construction cooperation and cohesion with the civil engineering and other professional construction team
Content |
Measures |
Cooperate with civil engineering general contractors |
After confirming the winning bid, our company will assign full-time technical personnel to stay on the construction site, and cooperate with the general contractor to be responsible for the steel structure embedded parts and other construction connection issues related to the steel structure. |
Cooperate with other professional construction |
After confirming the winning bid, our company promises that from the deepening of the drawings to the factory processing and on-site installation, we must appoint full-time personnel to be responsible for timely communication with other professional construction. Especially in the process of on-site construction and installation, our company promises to comply with the overall arrangement of the owner, supervision and general contractor,and cooperate with other professional construction companies to achieve the aim at completing the project with smooth and high quality. |
3.9 Protection of finished completed buildings
No |
Measures |
1 |
Personnel education: After the steel structure installation personnel enter the field, all the staff will carry out special education on the protection of existing structures, and strengthen the personnel's awareness of the protection of existing structures,especially the awareness of construction safety officer and construction dispatcher, machinery operation commander in this respect; encourage employees to protect construction products and semi-finished products through rewards and punishments. |
2 |
Reinforcement of cargoes, material and machine management: During the transportation, assembly and installation of steel structural members, the establishment of a complete management system for completed buildings and the establishment of a responsible person system to strengthen the management of cargoes, material and machine to minimize the active factors possibility that possibility cause damage to structures. |
3 |
Strengthen passive protection: set up the protective nets on the external surface of the structure connected to the steel structure or consult with the professional construction teams to work out appropriate protection measures to reduce the possibility of damage to the structure |
4 |
Carry out leveling and hardening of the area where the crane moves and the assembled docking area. For the construction area of the support frame, the local area needs to be strengthened. For particularly complex reinforced areas, it shall be resolved through consultation with the owner and the general contractor. |
4. Determination of the construction sequence of stadium steel structure
Content |
Measures |
Determination of the construction sequence of stadium |
The construction of the entire stadium hood steel structure project is divided into two construction areas, namely the West District and the East District. In order to speed up the construction progress, two 150-ton crawler cranes are arranged on the outside of the stadium, and one 80-ton truck crane is arranged in side of the stadium. Each construction area is hoisted from the middle to both sides. After hoisting the steel structure in the west area, hoist the steel structure in the east area. We follow the construction principle of bilateral symmetry and conduct construction simulation with a large-scale finite element program for the whole process to monitor the internal force changes during the construction phase. During on-site construction, make a timely inspection and compare with the calculation results to ensure the safety of the construction and ensure that the final completed structure meets the design requirements. |