Design of fully enclosed steel structure space frame coal shed (Part 1)

1、Enclosed coal storage structure

Most of the closed coal storage structures adopt masonry, wood and concrete structures. The classification of coal storage structure from the point of view of force, there are two forms of three-dimensional force system and space force system, plane force system is simple including beam and column system, portal steel frame system, etc.. The most common way of coal storage in China is space bearing system. According to the body type can be divided into flat type, column type, spherical type, conical type, etc.. According to the level of closure is open-air, semi-enclosed, fully enclosed. According to the material is concrete structure, steel structure, wood structure membrane structure, alloy structure.

2、Design principles of coal storage structure

(1) The rationality of coal storage structure and the arrangement of space frame structure support. The selection of coal storage structure should be based on the construction form, span, support mode, load mode and other requirements to determine a reasonable understanding of coal storage, but also should consider the mutual influence of the lower support structure of the grid structure, but also to ensure the stability and safety of the structure. Grid structure is generally the upper chord or lower chord node resting on the beam, truss and other lower structures, according to different resting methods, can be divided into side support, point support and mixed mode.

(2) Support bearing of space frame shell structure. Column surface mesh shell can be used along the four sides of the support, end cross-section or through the support along the two sides of the way. The support points along both sides of the support should ensure the condition of resistance to horizontal displacement of the bundle, and the end support cross-section should have sufficient plane stiffness support. Most of the coal storage column face mesh shell construction is supported along two sides, and when the end is closed by a mountain wall there will also be a situation of three aspects of support. The support of the column mesh shell can not only fall directly to the ground, but also be supported on the structure below. Depending on the location of the support discharge, it can be divided into single-row and double-row supports. Single-row support is the structure upper chord support and lower chord support is the upper and lower chord support at the same time. Spherical mesh shell generally adopts the form of circumferential support, which can be specifically divided into internal support, external support and internal and external support at the same time.

(3) Load and application principles. The design of coal storage structure should consider the impact of wind load, constant load, temperature and earthquake on the safety of the structure. Structure force under load internal force, displacement and the necessary stability calculation, and according to the actual situation, the temperature, earthquake, support sitting and work installation and other effects of displacement and force to calculate. For more complex body type or overhanging coal storage structure in the absence of a solid coefficient is appropriate to do wind tunnel experiments to determine the body type and wind pressure distribution; and from different wind directions to consider the role of different load components, it is appropriate to combine the wind effects of multiple wind directions respectively.

(4) The design of structural rods. Space frame structure rod length-thin ratio has a system that is the size of the allowable length-thin ratio. Create a space frame structure of the rod cross-section size, the rod length-thin ratio do not exceed this permissible length-thin ratio. About the rod under pressure, the allowable length to slenderness ratio is primarily to prevent the rod excess slenderness better bending, and this curvature for the pressure rod stability limit bearing capacity has a very large impact; about the rod under pressure, the allowable slenderness ratio is mainly responsible for ensuring that the rod in the production, transportation, installation and use process has sufficient stiffness; for the support seat near the support seat, because of the complex boundary conditions sometimes produce change, the requirements of some strict.