Discussion on construction technology and management of super high-rise steel structure buildings

　　1 Construction technology of super high-rise steel structure

　　The technological process and characteristics of super high-rise steel structure: component acceptance → hoisting → high-strength bolts → welding and testing → profiled steel plates and studs. Combined with this process and characteristics, the construction technology of super high-rise steel structure is briefly summarized.

　　The construction technology of super high-rise steel structure mainly includes the following aspects: selection, layout and assembly and disassembly of tower cranes; entry, acceptance and stacking of components; hoisting; measurement control; welding; construction period and quality control; safe construction.

　　2 Selection, layout and assembly and disassembly of tower cranes

　　2.1 Selection, arrangement and assembly and disassembly of tower cranes. Tower cranes are the core equipment for the construction of super high-rise steel structure projects. Safe, convenient and reliable. In the selection of tower cranes, the internal climbing tower crane should be given priority, because the steel structure building does not need to reinforce the floor and has a greater degree of freedom in the layout of the crane. On the other hand, the use of internal climbing tower cranes for hoisting and construction of super high-rise buildings with steel structures does not require the lifting capacity and amplitude of the tower cranes to be as severe as the use of attached tower cranes. In addition, the cost of using the attached tower crane is much higher than that of the same type of inner climbing tower crane with slightly smaller lifting capacity. The column is 12m, the sling is 4m-6m, the hook pulley and the trolley are 4m high, the safe operation distance is 2m, etc.), and the height of the underground part is 250m, while the inner climbing tower crane is used. The tower body is about 40m to 50m. The rental cost of the attached tower crane is higher than that of the inner climbing tower crane. Therefore, from an economic point of view, in order to save costs, internal climbing tower cranes are preferred for the construction of super high-rise buildings with steel structures.

　　2.2 Hoisting

　　Hoisting is an important process in steel structure construction, and the speed and quality of hoisting play a pivotal role in the entire project. Before the hoisting of the steel structure, the hoisting partition and hoisting sequence should be determined according to factors such as the shape of the structural plane and elevation, the structural form, the number and location of tower cranes, and on-site construction conditions. A project is divided into two operation areas, east and west, and two operation groups complete the hoisting of components within their respective scopes.

　　The general principle of hoisting is:

　　(1) In the plane, it expands from the central core tube to the surrounding, that is, starting from a unit in the middle, first assemble a stable rigid column net unit, first hang the column and then hang the beam, after a column net unit is hoisted and temporarily fixed, Then hoist two units on its left and right or front and back, and after all three unit components are hoisted, carry out a comprehensive and accurate correction.

　　(2) Vertical hoisting sequence (taking one column and three floors as an example): first install 4 steel columns → lower frame beams → measurement correction → bolt initial tightening → middle frame beam → upper frame beam → measurement correction → bolt initial tightening → Measurement and calibration → final tightening of high-strength bolts → welding → weld inspection → lamination of upper laminated steel plates and stud welding → lower and middle laminated steel plates and stud welding → lower, middle and upper steel ladders, platform hoisting → floor Cover reinforced concrete floor construction.

　　In the construction of the main steel structure of a certain project, the "regional hoisting" and "one machine multiple hoisting" technologies are adopted to solve the contradiction between the tight construction period and the large amount of work. It is obvious from the steel structure construction process that each process is not only interrelated They also restrict each other, and the choice of measurement control method directly affects the measurement accuracy and progress of the project. In the measurement and construction of a certain project, we adopt a combination of "pre-control" and "tracking correction", that is, to perform preliminary measurement of the floor column elevation and positioning before hoisting, and control the marking of components. After hoisting, the column and beam frame will form The column is initially corrected and corrected in time, and the final correction is performed after the unit body is formed, which greatly reduces the difficulty of correction and achieves the goal of a virtuous circle between the various processes of regional construction. In the aspect of overall measurement and control of the structure, according to the characteristics of the structure without a standard layer and the space hyperboloid, a complete set of measurement methods for "spatial coordinate point positioning" and "double-system review control" using a laser plumbometer and a total station were explored. , which solved the problem of positioning the hyperboloid structure well and ensured the realization of the project quality control objectives.

　　2.3 Welding

　　2.3.1 Determine the welding sequence

　　①In-plane: It should expand from the center of the building plane to the surrounding, and adopt the sequence of structural symmetry, node symmetry and omnidirectional symmetry.

　　②Vertically: upper frame beam → profiled steel plate support → lower frame beam → profiled steel plate support → middle frame beam → profiled steel plate support → welding inspection (column-to-column welding can be carried out before beam welding, or later).

　　③The column-to-column welding should be performed by two welders facing each other, and the two sides should be welded symmetrically at the same temperature and speed.

　　④For the welding of column and beam section head, generally the lower flange plate of H-beam is welded first, and then the upper flange plate is welded. The two ends of a beam should be welded with one end first, and the other end should be welded after it has cooled to room temperature.

　　2.3.2 Determine the welding process

　　The welding construction of the steel structure of a certain project is difficult, not only the steel plate is thick, but also because the structure is hyperboloid, a large number of diagonal braces and diagonal columns are used in the design, resulting in more vertical welding and diagonal vertical welding. Important parts, and most of them are outward and oblique, and it is difficult to operate safely and protect them during construction. For the contradiction between the urgent construction period and the large welding engineering quantity, it is recommended to use CO2 gas shielded semi-automatic welding for vertical welding, inclined vertical welding and depression fillet welding, which fundamentally solves the problem that the slow speed of manual arc welding affects the progress. , to meet the needs of welding construction.

　　2.3.3 Determining welding parameters

　　After selecting the process, the welding QC (QC is the abbreviation of "Quality-Control", which means quality control) team, led by the project team, passed the process evaluation, and compiled a set of practical CO2 gas protection semi-automatic suitable for the characteristics of the project. Welding method and parameters. First of all, determine the key targets, use the ABC method to find out the reasons that affect the quality, and carry out a series of analysis to find out the corresponding countermeasures for these problems; establish an effective quality assurance system, and formulate a complete process instruction. After repeated tests, the process parameters for horizontal welding, flat welding, vertical welding and oblique vertical welding were determined. Operation essentials: In order to keep the welding environment in a relatively stable state, construction protection measures and auxiliary measures have been strengthened. Through the unremitting efforts of the project team and the welding QC team, the welding process problem of CO2 gas shielded welding applied to the vertical and oblique vertical joints of ultra-thick parts has been well solved.

　　2.4 Safe construction

　　Safety construction is a very important link in the construction of steel structures. The construction of super high-rise steel structures is characterized by many high-altitude and suspended working points. In the construction process, there are hundreds of thousands of high-strength bolts alone. Although these parts are small, if they fall from a height of more than 100m, the consequences can be imagined. According to the characteristics of super high-rise steel structure construction, the method of combining advance and process control is adopted, that is, protective measures (such as anti-falling plates, anti-falling devices, safety ladders, cable wind ropes, etc.) are taken in advance, and the construction personnel are strengthened. Safety education and training, adhere to the daily safety inspection system. In a project, a safety net is installed on the outer wall when hoisting the column, and a temporary movable walkway is set up when hoisting the frame beam, which is raised layer by layer with the frame hoisting; when high-strength bolts are tightened, a hanging basket is hung at the end of the beam, and an operating platform is set up during welding. Do the laying of floor profiles in time to ensure construction safety.

　　3 Suggestions on the construction of super high-rise steel structures

　　3.1 Fully understand the node deepening diagram and formulate the construction process reasonably.

　　3.2 Reasonable selection of mechanical equipment according to the characteristics of the project, especially the selection of tower cranes, and the feasibility of its assembly and disassembly should be considered.

　　3.3 Reasonable welding process and parameters should be selected according to different structural characteristics, welding forms and climatic conditions. It cannot be generalized and blindly copied.

　　3.4 The processing sequence and quantity of structural components should fully consider the site stacking conditions and the hoisting capacity of the hoisting equipment.

　　3.5 Strict factory production process to reduce the number of on-site processing.

　　3.6 The measurement control should be closed and corrected by sections, levels and stages to prevent the generation of accumulated errors.

　　3.7 Security protection should be followed up in a timely manner, measures should be strict, and inspections should be in place.