Spatial grid frame of steam turbine roof structure

For the space grid of the steam turbine roof structure, at present, each main design unit generally outsources the design, production and installation of the steel structure grid company. The main design unit proposes design technical conditions and special requirements, compiles the bidding document, and is responsible for explaining and reviewing the special requirements of design technology during the process of answering questions in the bidding. The main design institute should be responsible for confirming whether the adopted regulations and specifications conform to the contract text; whether the design scope, depth, and calculation principles meet the contract requirements; whether the grid design meets the specifications and contract requirements.

In view of the great advantages and characteristics of the space grid roof structure, especially after the Tangshan earthquake, in order to reduce the structural self-weight, more and more grid structures and light roofs are adopted for the steam turbine roofs and substation control buildings of power plants. In the early years of the Panshan Power Plant and the second phase (2×500MW) of the Shentou First Power Plant, the grid structure was successfully adopted for the turbine house, which played a role in promoting. In the side bunker system of the thermal power plant demonstration design in 2000, the steam turbine roof system was discussed and analyzed, and the economy and rationality of the grid structure were proposed from many aspects. The grid structure is used in the main powerhouse of many power generation projects. However, in April and July 2005, roof grid collapse accidents occurred in Shanxi Changzhi Power Plant (2×300MW) and Inner Mongolia Xinfeng Thermal Power Plant (2×300M). Many projects later changed the grid structure to an ordinary steel roof truss structure.

The grid structure is a form of spatial grid structure, and most of the grid structures are made of steel pipes and spherical nodes. The grid structure is generally divided into the following four major types of grid structures consisting of a plane truss system, a quadrangular pyramid, a triangular pyramid and a hexagonal cone.
In the main building of thermal power plant, the steam turbine roof system usually adopts a four-cone grid. The bottom of the quadrangular pyramid that composes this grid is parallel or perpendicular to the boundary, and the pyramids are spread over the entire grid plane. The upper (lower) chord node of the grid is the vertex of the straight (inverted) pyramid, and can also be regarded as the corner point of the bottom of the inverted (ordered) pyramid, so that the plane of the upper and lower chords in the same direction The projection exactly forms two sets of parallel lines, which differ by half the grid spacing from each other. The formed upper and lower chord grids are usually square. When the chord lengths in the two directions are not equal, rectangular grids can also be formed.
Advantages and characteristics of grid structure:
1. Space work, the way of force transmission is simple and convenient, which is more suitable for large-span, large-column roof structure.
2. Light structure and good economic indicators. Compared with the flat steel roof truss of the same span, when the span is less than 30m, it can save 5~10% of steel consumption; when the span is more than 30m, it can save 10~20%.
3. Large spatial rigidity, low structural weight, and good seismic performance.
4. Easy construction and installation. The grid rods and nodes are of few types and small in size. Transportation, storage, loading and unloading, assembling are more convenient.
5. The layout of the grid is flexible, and the roof system is flat, which is conducive to the installation of suspended ceilings, pipelines and equipment.
In the middle of the 20th century, especially in the past 30 years, space grid structures have been widely used in large-span buildings such as stadiums, hangars, and exhibition centers throughout the world. Since the first flat-panel grid structure was built in China in 1964, the grid structure has developed rapidly in the past 40 years, and the construction and manufacturing scale of the grid structure have ranked first in the world.