Discuss the construction technology and management of super high-rise steel structure building
2020-05-10 22:01:05
Share
Construction Technology of 1 Ultra High Steel Structure
Process flow and characteristics of ultra-high-rise steel structure: component acceptance → hoisting → high strength bolt → welding and testing → profiled steel plate and stud. Combined with the current 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, arrangement and installation of tower crane; entry, acceptance and stacking of components; hoisting; measurement control; welding; duration and quality control; safe construction.
Selection, Layout and Installation of 2 Tower Hoists
2.1 Selection, layout and assembly and disassembly of tower cranes, tower cranes are the core equipment for the construction of super high-rise steel structures, and their selection and arrangement should be comprehensively considered according to the layout of the building, site conditions and the weight of the steel structure and other factors, and ensure the assembly and disassembly Safe, convenient and reliable. In the selection of tower cranes, priority should be given to internal climbing tower cranes, because the use of internal climbing tower cranes for steel structures does not require reinforcement of floors, and there is a greater degree of freedom in the placement of cranes. On the other hand, the use of internal climbing tower cranes for the construction of steel super-tall buildings does not require the lifting capacity and range of tower cranes to be as demanding 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 internal climbing tower crane with a small lifting capacity. For example, the height of a project is 200m, and the height of the tower using the attached tower crane is about 230m (including 3 layers of steel structure) Column 12m, sling 4m ~ 6m, hook pulley and trolley full height 4m, safe operating distance 2m, etc.), plus the underground part height of 250m, and the tower body with internal climbing tower crane is about 40m ~ 50m. The rental cost of the attached tower crane is greater than that of the internal climbing tower crane. Therefore, from the economic point of view, in order to save costs, the internal climbing tower crane is preferred for the construction of steel super-tall buildings.
Measures should be strict and inspections should be in place.
2.2 Hoisting
Hoisting is an important process of steel structure construction, the speed and quality of hoisting plays an important role in the whole project. Before hoisting the steel structure, the hoisting partition and hoisting sequence should be determined according to the structure plane and elevation shape, structure form, the number and position of tower crane, the construction conditions on the spot and so on. A project is divided into two operation areas, east and west, and the two operation groups respectively complete the lifting of components within their respective scope.
The general principles of hoisting are:
(1) In-plane expansion from the central core cylinder to the surrounding, that is, starting from the middle of a unit, first assembled into a stable stiffness column net element, first lifting post and then lifting beam, a column net element hoisting and temporary fixing, and then in its left and right or back hoisting two units, after the completion of all three unit members hoisting, complete accurate correction.
Vertical hoisting sequence (take one column and three layers as an example): first install 4 steel columns → lower frame beam → measurement correction → bolt initial screw → middle frame beam → upper frame beam measurement correction → bolt initial screw measurement correction, final screw high strength bolt → welding → weld inspection, loose upper profiled profiled steel plate and stud welding → lower middle profiled steel plate and stud welding lower, middle, upper steel ladder, platform hoisting < unk1> Reinforced concrete floor construction.
In the construction of the main steel structure of a certain project, by adopting the techniques of "area hoisting" and "one machine and more hoisting ", the contradiction between the tight construction period and the large amount of engineering is solved. It is obvious from the construction process of steel structure that each working procedure is connected and restricted, and the selection of measurement control method directly affects the measurement accuracy and progress of the project. In a certain engineering survey construction, we adopt the combination of "pre-control" and "tracking correction ", that is, the floor column elevation and positioning are preliminarily measured before hoisting, and the components are marked and controlled. After hoisting, the column is initially corrected and corrected in time before the column beam frame is formed, and the final correction is carried out after forming the unit body, which greatly reduces the difficulty of correction and realizes the goal of virtuous cycle between the various processes of regional construction. In the aspect of overall measurement and control of structure, according to the characteristics of structure without a standard layer and spatial hyperbolic surface, a whole set of measurement methods of "spatial coordinate point positioning" and "dual system check control" using laser collimator and total station instrument is found out, which solves the problem of structure positioning of hyperboloid well and ensures the realization of project quality control goal.
2.3 Welding
2.3.1 Determination of welding sequence
1 In-plane: It should be extended from the center of the building plane to the surrounding area by sequential welding of structural symmetry, node symmetry and omnidirectional symmetry.
Vertical: upper frame beam → profiled steel plate support → lower frame beam → profiled steel plate support → middle frame beam and profiled steel plate support welding inspection (column and column welding can be done before or after beam welding).
The welding of 3 columns and columns shall be opposite by two welders, and the two sides shall be welded at equal temperature and isokinetic symmetry.
4 column and beam joint head welding, generally first welding the lower flange plate of H section steel, then welding the upper flange plate. The two ends of a beam should be first welded one end, after cooling to normal temperature, then the other end.
2.3.2 Determination of welding process
It is difficult to weld steel structure in a certain project, not only the steel plate is thick, but also because the structure is hyperboloid, a large number of inclined braces and columns are used in the design, resulting in more vertical welding, oblique vertical welding, such structures are not only in the important part of the structure, but also mostly in the outward, oblique, safe operation and construction protection are more difficult. For the contradiction between the urgent time limit and the larger welding quantity, it is suggested that the semi-automatic welding with CO2 gas protection should be used in vertical welding, oblique vertical welding and angle welding, which can fundamentally solve the problem that the slow speed of manual arc welding affects the progress and meet the needs of welding construction.
2.3.3 Determination of welding parameters
The welding QC (QC is the abbreviation of "Quality―Control", which means quality control) team worked out a complete set of practical and feasible semi-automatic welding methods and parameters for CO2 gas protection according to the characteristics of the project through process evaluation under the drive of the project team. First, the key target is determined, the cause of affecting quality is found out by ABC method, and a series of analysis is carried out to find out the corresponding countermeasures against these problems; an effective quality assurance system is established, and a perfect process instruction is formulated. After repeated tests, the process parameters used in horizontal welding, flat welding, vertical welding and oblique vertical welding were determined; through the extension length of welding wire, weld layer cleaning, welding torch welding angle repeatedly groping, forming a whole set of operating essentials; in order to make the welding environment in a relatively stable state, the construction protection measures and auxiliary measures were strengthened. Through the unremitting efforts of the project team and all the personnel of the welding QC group, the welding process of the CO2 gas shielded welding applied to the vertical and oblique vertical joints of super thick parts is solved well
2.4 Safe construction
Safety construction is a very important link in the construction of steel structure, and the construction of super high-rise steel structure is characterized by high altitude and suspended operation points. During the construction process, there are hundreds of thousands of high strength bolts alone. Although these parts are small, if they fall from a high altitude of more than 100 m, the consequences can be imagined. According to the characteristics of super high-rise steel structure construction, the method of combining prior and process control is adopted, that is, taking protective measures (such as anti-fall plate, anti-fall device, safety ladder, cable wind rope, etc.) in advance, and strengthening safety education and training for construction personnel, and adhering to the daily safety inspection system. A safety net is set up on the outer wall of a project when lifting the post, temporary movable walkways are set up when lifting the frame beam, and rise layer by layer with the frame hoisting; hanging basket is set up at the end of the beam when twisting the high strength bolt, operating platform is set up when welding, and floor compression plate is laid in time to ensure the construction safety.
Some Suggestions on the Construction of Super High-rise Steel Structure
3.1 Fully understand the node deepening map and rationally formulate the construction technology.
3.2 Reasonable selection of machinery and equipment according to the characteristics of the project, especially the selection of tower cranes, and the feasibility of their installation and disassembly should be considered.
3.3 Reasonable welding process and parameters should be chosen according to different structural characteristics, welding form and climatic conditions.
3.4 The processing sequence and entry quantity of structural components should take full account of site stacking conditions and lifting capacity of hoisting equipment.
3.5 Strict factory manufacturing process to reduce the number of on-site processing.
3.6 Measurement control should be divided into sections, levels, stages of closure, correction, to prevent the cumulative error.
3.7 Safety protection should be followed up in a timely manner, with strict measures and inspection in place.
