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2022-10-17
Prefab workshop construction is increasingly using space frame structures, the space frame structure is one of the spatial structures. Most of the space frame structures are made of steel tubes and spherical joints. The space frame structure is generally divided into four categories: plane truss system, quadrangle cone, triangular cone, and hexagonal cone.
The surface system of the steam engine house in the main workshop of the thermal power plant usually adopts the forward four-cone network frame, the bottom edge of which is parallel to the boundary, or the vertical cone covered in the whole network plane. The rack on (under) string node is down (down) the vertex in the pyramid can also be used as a fall (cis) by a cone bottom corner, and keep the same direction, the bottom chord plane projection on two sets of parallel lines and poor for just a half of the space frame spacing, formation of upper and lower chord is usually a square space frame when two directions of chord length range can also form a rectangular space frame.
Advantages and characteristics of the space frame structure:
1) Space work, simple way of force transmission, more suitable for large span, large column space frame roof structure;
2) Lightweight structure, good economic indicators. Compared with the same span of the plane steel roof frame, when the span <30m, steel, can save 5%~10%; When the span >30m, the amount of steel can be saved by 10%~20%
3) Large space stiffness, small structure dead weight, good seismic performance.
4) Simple construction and installation · There are a few types of space frame rods and nodes, and the size is not large. Transportation, storage, loading and unloading, and assembly are convenient
5) The layout of the space frame is flexible and the roof system is smooth, which is conducive to the installation of suspended ceiling, pipes, and equipment
In the middle of the 20th century, especially in the last 30 years, spatial space frame structure was widely used in the world gymnasium, hangars, exhibition centers, and other large-span buildings. Since the first flat-type space frame structure was built in 1964, the space frame structure has developed rapidly in the past 40 years. The construction and manufacturing scale of space frame structure rank first in the world. In view of the advantages and characteristics of spatial space frame roof structure, in order to reduce the weight of the structure, especially after the Tangshan earthquake, more and more space frame structures and light roofs are used in the main workshop of the power plant and the control building of the substation. In the early 1990s, Nanshan Power Plant and The second phase (2×500 MW) of Shantou No.1 galvanized steel warehouse adopted the space frame structure successfully, which played a driving role: in the coal bunker system of thermal power plant demonstration design in 2000, After discussion and analysis, the economy and rationality of the space frame structure are proved from many aspects. The space frame structure has been applied in many power generation projects. However, in April 2005 and July 2005 respectively in Shanxi Changzhi power Plant (2×300MW) and Inner Mongolia Xinfeng Thermal Power Plant (2×300M) roof space frame engineering collapse accident followed by many projects to ordinary steel roof truss structure. At present, the space frame of the surface structure of the steam turbine house is generally outsourced to the steel structure space frame company for design, production, and installation. The main design unit shall put forward design technical conditions and special requirements, compile the bidding document, and be responsible for explaining and reviewing the special requirements of design technology in the process of answering questions in bidding. The main design institute shall be responsible for confirming whether the procedures and specifications adopted are in conformity with the contract text; Whether the design scope, depth, and calculation principle meet the requirements of the contract; Whether the space frame design meets the specification and contract requirements.
Technical and economic characteristics of the space frame structure system of prefab workshop.
The main workshop structure of the demonstration power plant in 2000 adopts the scheme of an outer coal bunker. The steam engine head is close to the boiler, which provides more advantages for the space frame roof structure in the objective SAIC engine room. In the engineering design of the demonstration power plant (300MW conventional generator set) in 2000, southwest Electric Power Design Institute used STAAD-III spatial structure analysis software to compare and analyze the above roof structure types.
Plane size of steam engine room: 24m×48m Longitudinal column distance: 2×11+10+3×8 = 48m; Gable column spacing: 2×9+6 = 24m. The space frame structure adopts peripheral column support and the gable column is considered as the supporting point of the space frame structure and transmits the gable wind load. Steel roof truss and light steel structure are supported by one-way-bearing bilateral columns. The roof shall adopt light double-layer insulation sandwich-shaped steel roof dead load (excluding load-bearing structure gravity but including purlin gravity) of 0.3kN/m2 roof live load: 0.7kN/m2; Consider using the stiffness of roof structure to bear and transfer horizontal load. The space frame rod generally does not exceed ф 133×8 space frame structure is hinged with the frame column at the top of the column. Light steel structure steel beam height generally between 750 ~ 900mm steel truss, light door steel frame, and frame column rigidly connected. The calculation and analysis of two schemes of space frame structure and light steel roof structure show that the internal force of the gable of the space frame structure is greater than that of light steel structure and the displacement is less than that of light steel structure under the action of horizontal brake force. The displacement of the gable and internal force of the column foot under longitudinal and horizontal brake force are greater than those of light steel structure, indicating that the space performance of the space frame structure is better than that of light steel structure. From STAAD – simulation of crane transverse level III brake force under the action of the structure of the whole deformation graphics to underestimate the steel structure depend mainly on the brake force plane steel frame with so that both across the width and the space truss structure within the scope of the pillars of node still has certain displacement curve comparison shows that the structure of the space truss structure mainly relies on the overall synergy Shared lateral local horizontal load.
In terms of steel quantity index and deformation value, the steel truss is the best and the light steel structure is the worst. This is due to the length-to-width ratio of the project roof structure: 48m / 24m = 2≤ 2.5 using the space frame structure can give full play to the space frame structure in the surrounding support, bidirectional stress conditions of good mechanical performance. Compared with steel trusses and light steel structures, the steel content of roof purlins with smaller mesh sizes (generally between 2.5 and 3.0 m) can also be greatly reduced.
At present, the following methods are commonly used for spatial space frame roof structures:
① The possibility of the implementation of the overall lifting depends on the actual lifting capacity of the construction unit.
(2) Small-unit aerial assembly is currently more popular with construction units.
(3) high-altitude bulk needs to use steam engine room driving or other production of construction platform. However, due to the construction of the initial stress and initial deformation of large steam engine room traffic and equipment installation professional contradiction is more prominent power construction companies generally will not consider the space frame company using steam engine room traffic installation conditions. Design units generally should not recommend methods (2), (3) high altitude assembly, and high altitude bulk solutions.
