Construction technology of pre-assembly of high-rise steel structure building

From today’s high-rise building work, it can be seen that in the process of application of steel structure, not only breaks the complex form of steel structure, but also has a certain correlation between components. In addition, in the process of high-rise steel structure construction, due to the constraints of various different factors, in order to improve work efficiency, high-rise steel structure construction should break the traditional construction method. In the process of construction, the staff need to pay more attention to the construction site, the lifting equipment and the construction time, which can effectively solve practical problems. In addition, in the actual work, the staff should pay more attention to the pre-assembly construction technology, do a good job of application, and improve the efficiency of construction under the guidance of this construction technology.
1 Project Overview
A construction project is a typical high-rise steel structure building, in the process of construction, the staff mainly uses the pre-assembly construction technology. The building is 120 meters high and is divided into two main structures, with 35 floors above ground and 3 floors below ground. In this construction project, the main building structure is mainly reinforced concrete structure, the appearance is mainly steel frame outer cylinder, the outer frame column structure is mainly concrete filled steel tube column. Concrete-filled steel tube columns show certain inclinability. The outer steel frame column has undergone obvious changes in size. Among them, the structure of 3-4 layers on the ground is more complex, in addition, the elliptic cylinder is also transformed into a cylindrical structure. In the actual project, the construction of steel column structure has a certain complexity and difficulty, the relevant staff in the construction of the project, the use of pre-assembly construction technology.
2 The overall scheme of the application of pre-assembly construction technology
In the entire construction process, the steel column structure of 2-3 layers on the ground is more complex, in addition, because the steel column structure of this level is relatively large in the horizontal direction or in the vertical direction, in the assembly process, not only to ensure the precision of pre-assembly, but also to try to be concise and economical. Therefore, before the construction, it is very important to formulate a scientific and reasonable construction plan. It can be seen from the actual construction site that in order to carry out the overall assembly, the site should be fully taken into account, but the construction site in this project is not allowed, and the economy is not very prominent. In order not to affect the stability of construction and to improve the simplicity of construction, the staff mainly involves the following construction schemes:
A total of 18 elliptic cylindrical structures are distributed in 3 regions, and they are equally distributed. In the actual setting process, the elliptic cylinder in each region should form an Angle of 120°. In order to meet the needs of the entire construction site and achieve the purpose of assembly, the construction personnel divided the entire construction project into three batches to do a good job of pre-assembly. After the end of the pre-assembly, the pre-assembly tire frame remains unchanged, and one end of the radial beam and the steel column should be connected to each other. It should be noted that the radial beam does not do the pre-assembly work. In the design process, in order to ensure that the height of the assembled tire frame meets the standard, the designer mainly uses the lying method to carry out, specifically, to select a datum surface for construction, to ensure that the assembled tire frame is in a relatively gentle stage. In this way, the tire frame is relatively easy to set up and ensure the scientific and normative work of pre-assembly. At the same time, it should also ensure that the steel column structure and the floor ring beam structure and the panel maintain a certain vertical.
3 tire frame design and layout
In the actual component setting and construction is too heavy, its spatial coordinates will appear a certain difference, the layout of the tire frame is relatively complex, in order to ensure that the pre-assembled tire frame to achieve a certain level of stability, the base level of the tire frame needs to maintain a certain balance with the earth. In the process of setting it, the staff and technicians need to compare and analyze by drawing, in general, the origin is mainly set in the middle of the circular tube center 600mm below the position. Then CAD software is used to model and ensure the scientific position of the tire frame. This setting is mainly to adjust the height of the steel column and realize the connection between the steel column and the tire frame. In addition, in the actual work, the construction personnel should design and improve the scientific layout of the tire frame, which should mainly be based on the actual needs of users, and should also improve the accuracy of the template setting.
In the CAD three-dimensional model, the user’s current coordinate xy plane is defined on the datum plane, so that the height of the tire frame can be determined according to the control point z coordinate of the tire frame. According to the position of the tire frame template, a vertical geodetic plane is made and the steel column is tangent, so that the accurate shape of the template can be obtained. Draw the positioning inspection line of the component and the inspection line of the tire frame on the ground, and the tolerance requirements of the reference line are as follows: length ±1mm, width ±1mm, diagonal ±1mm. When the tire frame is arranged, the three-dimensional coordinate measurement of the template is carried out by the total station instrument. After the template is accurately positioned, the template is welded firmly with the tire frame.
4 Pre-assembly details
The pre-assembled components are hoisted to the tire frame, and the coordinates of the steel column port and the bull leg control point are ensured by the fit between the hammer line and the reference line on the ground. After all the components are hoisted in place, the three-dimensional coordinates of each steel column detection point are measured by the total station instrument. If there is any deviation, the gasket is used for fine tuning to ensure that the coordinate values of the steel column port and the bull leg meet the requirements. In addition, the verticality of the steel column wing edge must be ensured, spot-welded with the tire frame after correct positioning. 3 to 4 layers of ring beam on the tire frame for positioning, the ring beam positioning should be relaxed, do not impact on the column leg to prevent the leg from moving. When the ring beam is positioned, its center line is aligned with the ground positioning center line, and the coincidence between the center line and the contour line of each component and the ground line is strictly controlled. In addition, it is necessary to pay attention to the weld gap and the interface wrong edge between the ring beam end and the steel column leg. When the steel beam is positioned, the web of the steel beam and the web of the bull leg of the steel column are temporarily connected by the connecting plate with the tool bolt. At the same time, in order to check the perforation rate of the bolt hole, a hole tester 0.3mm larger than the nominal diameter of the high-strength bolt is used to test the hole of each bolt hole to ensure that the perforation rate of the high-strength bolt reaches 100%, and the spot welding with the tire frame is firm after correct positioning.
The leg web of each component connecting the ring beam is spot-welded. When the hole tester cannot pass through the bolt hole, the position of the leg web should be adjusted appropriately to ensure that the bolt perforation rate reaches 100%, and the leg web should be welded according to the requirements of the drawing. The component or structure is in a free state during pre-assembly and shall not be forcibly fixed. After the pre-assembly is completed, the components are marked. Ring beam at both ends of the corresponding axis number, clear site installation direction; At the same time, the joint mark line is marked as the basis for on-site installation. After the pre-assembly is completed, the components shall not be damaged during disassembly. The spot welding position shall be polished to ensure that the interfaces are smooth and clean.
Closing remarks
This paper combined with an engineering project, through the pre-assembly of steel structure components, timely grasp the production and assembly accuracy of components, adjust some out-of-standard items, and analyze the causes, and timely control in the subsequent processing. This paper introduces the application of preassembly technology in a steel column steel structure engineering, and expounds its technical principle and operation method. The dimensional accuracy of the component is better controlled by measuring the three-dimensional coordinates of the control points with the total station. Through the analysis of the problems in the process of pre-assembly, the engineering practice provides a reference for the subsequent processing of components. The pre-assembly process can provide a similar reference for the subsequent production and installation of similar steel structures.