The space frame structure has good structural performance and a wide range of applications, especially for the installation of long-span steel structures. It has the advantages of saving steel, manufacturing technology, and convenient installation and construction. It is widely used in large-scale power generation facilities, petrochemical, coal fields and other industries. In the construction of coal yards, in the past, most of the coal yards were piled in the open air, which caused great environmental pollution and affected the normal use of the coal yards. The coal raw material workshops of thermal power plants required relatively large building areas and spans (currently, the domestic span has reached 120m above), so that the steel space frame shell structure is widely used in the raw material dry coal shed workshop.
The shell structure of the space frame of the dry coal shed has the characteristics of large span and high vertical height. During the construction process, it is necessary to comprehensively determine a reasonable construction method according to different structural forms, combined with project progress and quality and safety requirements. At present, space frame installation methods include high-altitude loose assembly method, block installation method, sliding method, overall hoisting, etc. This paper takes the space frame of a dry coal yard as an example to carry out the calculation and implementation of the construction plan selection.
A project is a space frame of a dry coal shed in a strip-shaped closed coal yard, using square quadrangular pyramids and bolt ball nodes. The space frame has a span of 105.8m and a length of 320m. The space frame is divided into two identical 105.8m×160m mirror space frames (Figure 1 ). The projected area is 33856m2. The space frame is supported by the lower string, and the elevation of the space frame is 40.14m. The space frame of this project is assembled on the ground and at high altitude at a high height, and the space frame has a large span, making hoisting difficult. After research, the project plans to use the technologies of ground assembly, starting frame lifting and hoisting, and high-altitude loose assembly for installation and construction.
Figure 1 Project renderings
2、Analysis of important and difficult points in construction
1）The overall size of the space frame of this project is large, it is difficult to lift, the installation accuracy is high, and it is difficult to take temporary safety measures after it is in place.
2）There are many types of components: various steel components are manufactured by the processing plant, and then loaded and transported to the construction site. There are many types and numbers of various components, and the specifications of the components are inconsistent. The on-site stacking is easy to be confused, and the organization and classification are difficult.
The space frame of this project has a large span, the main body size and quality are large, the height of the high-altitude splicing is high, and the hoisting is difficult. Ground assembly is adopted, and the installation method of starting frame lifting combined with high-altitude loose assembly is adopted. The first problem is the assembly of the starting frame, how to control it The stability and precise position of the starting frame installation are the difficulties in the control of this project. The space frame starting frame is the key to the hoisting of this project. The overall idea of this project is to use the “small unit assembly and deflection control method” to complete the construction of the starting space frame, and then carry out high-altitude loose assembly, and various components are interspersed in sequence. Select a suitable column space in the middle of the space frame and weld the support plate at one end of the shell of the space frame with the ball of the support in advance, so that the support at the end becomes a hinge. The units are assembled into structural units. According to the principle of the hinge, the structure can be rotated by 180° on the vertical surface of the support (hinge), and the other end of the structural unit between the columns is gradually lifted by a crane, and assembled at the same time until the space of the most edge unit after the frame is assembled, the whole is lifted to the design height and landed on another support. When using this technology, most of the components are installed on the ground or at low altitude, with high safety and quality, fast construction speed, and the safety of construction personnel is guaranteed. At the same time, the construction period is short, avoiding the construction of full scaffolding, and saving a lot of scaffolding costs.
1）Disclosure of construction drawings, technology and safety to all construction personnel. Organize construction personnel to carefully familiarize themselves with drawings, study construction specifications and procedures, and master construction techniques.
2）Check the foundation axis and elevation again before the structure is installed. The space frame structure should meet the following requirements: the axis meets the design and specification requirements; the elevation and the elevation of each node connected to the space frame support meet the design requirements.
3）Prepare equipment review record forms and various installation record forms.
4）The hoisting machinery that enters the site has an inspection certificate, and it must be submitted for examination and approval in time when entering the construction site.
5）The flaw detection of the assembly welding seam must be qualified, the welding process shall be evaluated, and the requirements shall be met, and the report shall be complete and effective.
6）The assembly of the space frame is divided into inspection batches, and inspections are submitted and accepted according to the batches, and the materials are complete and valid.
7）The hoisting scheme meets the requirements after expert demonstration and supervision approval.