Due to the advantages of fast construction, good seismic performance, high bearing capacity, and strong overall rigidity, steel structure workshops are more and more widely applied and popularized with economic development. It is also short, and it is inevitable that there are many defects and shortcomings.This article discusses the precautionary measures in the design of steel structure workshop.
In today's economic development and technological progress, steel structures are playing an increasingly important role in the field of construction due to their short construction period, large bearing capacity, and good disaster resistance. They have been widely used in plant design. In the past, reinforced concrete The plant is gradually being replaced by a steel structure plant. But at the same time, the disadvantages of the steel structure such as easy deformation, poor fire resistance, and easy corrosion should also be paid enough attention. Therefore, it is of great significance to discuss the design of steel structure workshops.
1. The design of steel structure workshop
1. The basic problem of steel structure workshop
Common ground foundation problems are mainly manifested in three aspects: foundation strength, foundation deformation and foundation failure. The strength of the foundation is concentrated on the problem of insufficient foundation stability due to insufficient bearing capacity; the deformation of the foundation occurs mostly in the uneven settlement of the loaded foundation, excessively deformed soft soil, expansive soil, collapsible loess and Seasonal frozen soil and other areas; the damage of the foundation is mainly in the form of local or whole shear failure and punching shear failure. When designing the foundation of the steel structure workshop, attention should be paid to these issues.
2. The size of the portal steel frame column net and the installation of the structural system
The number of components included in the steel structure plant project will have a direct impact on the construction progress and project cost of the project. The spacing design of the portal steel frame columns of the plant should first meet the use requirements of the plant. The spacing of the portal frame columns should be designed as 8. -9m, when the column spacing of the steel frame is designed to be 9m, the number of purlins, steel frames and other components required for the project will be reduced by 30% compared to the 6m column spacing, which is of great significance for shortening the project cycle and reducing the cost. The spacing of steel frame columns will affect the span of the project, and the design of the maximum span should not exceed 36m. Secondly, the problem of setting the steel frame column structure system, the purlins, wall beams and other members of the steel structure plant are used as the connecting parts between the steel frames to support the load in the longitudinal and horizontal directions of the plant, because the longitudinal horizontal force is borne by the support system of the plant Therefore, the horizontal support of the roof should be set between the end columns of each temperature section or reasonably, so that the plant as a whole forms a stable spatial structure. In the selection of the horizontal and vertical temperature sections of the door-type steel frame light structure plant, The transverse temperature section should not exceed 150m, and the longitudinal direction should not exceed 300m.
3. The design problem of the steel roof system
Most of the load-bearing members of steel roofs are composed of slender and thin-walled rods. The shape of the cross section is relatively complex. The stress of the nodes is relatively concentrated and there is eccentricity. Due to the calculated limit state, the safety reserves of the system component's bearing capacity are limited. The corresponding system is very sensitive to the effects of temperature, overload and corrosion. Accidental factors may cause its failure. Due to the impact of negative effects, the roof of the steel structure factory is easily the most damaged part. The damage of the steel roof is mostly manifested in the collapse of the roof, the deformation or cracking of the rods and node plates, the bending of the roof support, the deflection exceeding the standard and Analysis of broken rods and other aspects.
4. Design problems of crane beam system
The crane beam system is an important part of the steel structure workshop, including crane beam, crane track and connection, brake structure and other parts. The stress situation of the crane beam is very complicated, and the vertical and lateral forces of the crane have dynamic characteristics. Due to the effects of fatigue and impact, the calculation method and calculation diagram of the crane beam system are very different from the actual application situation. Compared with the roof system, it has more instability, and the overall reliability and durability of the system lowest. The design stress of the column system of the steel structure workshop is much smaller than the actual stress, the safety reserve of the column is larger, the probability of simultaneous load is relatively small, and the failure of the column due to insufficient bearing capacity is rare.
5. Purlins, wall beams and bracing problems
The purlins, braces and wall beams of the light-weight steel structure plant project mostly use Z-shaped and C-shaped solid-web cold-formed thin-walled steel materials. This type of steel has the advantages of better overall rigidity, slewing radius and inertia of the section The moment is large, which can give full play to the performance of the material. At the same time, the torsional stiffness of the profile section is small, and it is sensitive to load eccentricity. In the design process, it should be noted that the profile may have problems of constraining warping stress and torsional deformation. In purlins, The following issues should be noted in the design of bracing members such as braces, wall beams, etc .: (1) The standard value of wind load should be calculated according to the regulations. To reduce the inconvenience in the construction of the project, the use of double braces should be avoided; (2) The purlin is affected by the wind suction. When the lower flange is under pressure, it can be solved by stability calculation. The stability of the purlin can be checked by the formula in "Code for Design of Steel Structures".
2. Preventive Measures for Problems Existing in the Steel Structure Factory
1. Improve the fire resistance of the plant
Steel has a direct impact on the fire resistance of the plant. Due to the high temperature resistance of the steel, the strength of the steel itself will be significantly reduced in high temperature environments, resulting in deformation or even failure of the steel structure components. Fire resistance, to avoid the phenomenon of failure and collapse of the plant immediately in the event of a fire. To improve the fire resistance of steel structures, in addition to changing the material composition elements in the manufacture of steel, changing the structure and metallographic structure of steel itself to improve the fire resistance and weather resistance of steel, in the construction process, spraying method is usually used to improve the steel structure. Fire resistance, reasonable design of spray thickness, and spray according to design value. As the most economical and effective method, the spraying method has a faster construction speed, and is especially suitable for steel components with complex shapes. But at the same time, this method has the disadvantages of rough surface and difficulty in cleaning, and it should be modified by certain design techniques during construction.
2. Reinforced steel structure
In the design process of the steel structure workshop, the stability of the steel structure needs to be considered, and the reinforcement of the steel structure can be achieved by changing the structure. According to the distribution of the steel structure, the load, joint properties and force transmission path are reasonably changed, and the steel structure is reinforced by adding rods and supports, prestressing and strengthening the cooperative work of the space.
3. Roof and support design
In order to improve the overall rigidity of the steel structure plant, ensure the stability of the plant as a whole, and avoid excessive deformation of the members and the instability of the pressure rod, factors such as the form of the steel structure, the distribution of the equipment, and the length of the temperature section should be reasonably designed To make the plant support system stable and reliable. The support system can be set between the stable columns in the temperature section of the plant, and the horizontal and horizontal support of the roof can be coordinated. The lower column support of the plant should be set as far as possible in the middle of the temperature zone, so that the crane beam and other components can freely expand and contract to the two ends of the zone with temperature changes. The steel structure roof currently mainly has two forms: a rigid roof composed of two layers of colored profiled steel inner insulation cotton and a composite flexible roof composed of a color steel plate inner panel, an insulation layer, a gas barrier layer and a roll waterproof layer.
4. Reasonable design temperature expansion joint
The temperature change will cause deformation of the steel structure factory building, which will cause temperature stress to the steel structure. When the plane scale of the steel structure factory building is large, in order to avoid the large temperature stress of the steel structure, the temperature expansion joints should be reasonably set at the two sides of the factory building. In each direction, the distance of the section is determined according to the steel structure specification. Generally, the temperature expansion joints are processed by setting double columns, and the longitudinal temperature expansion joints can be set as rolling supports at the roof support.
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