With the rapid development of the national economy, steel structure plays an important role in the building field, and plays an increasingly important role in industrial and civil buildings. With its outstanding characteristics, steel structure has rapidly occupied an increasingly broad market. Its characteristics are: good overall stiffness and seismic performance, fast construction speed, light weight and high bearing capacity. It has replaced the reinforced concrete structure in large-span and super high-rise buildings, but it also has shortcomings such as poor fire protection performance and easy corrosion. According to its characteristics, the role of steel structure is brought into play. Now, the current situation and Optimization Countermeasures of steel structure plant design are analyzed.

1. Overview of steel structure industrial plant.

1.1. Advantages of steel structure industrial plant.

At present, in the design and construction of engineering plants in China, steel structure materials are mainly used as the main construction materials, and their advantages are mainly reflected in the following aspects:

(1) During the on-site construction of the industrial plant, since the steel structure materials can be produced in industrial batches, the mechanical equipment used in the construction process can be assembled on site. Therefore, the construction period of the project is greatly shortened and the total investment cost of the project is reduced.

(2) Compared with concrete structural materials, steel structural materials have the characteristics of light weight and high strength. Therefore, in the practical application process, it can not only greatly reduce the load generated by the building structure in use, but also effectively improve the stability and reliability of the plant structure. Moreover, after reliable anti-corrosion measures are taken, the steel structure also has strong corrosion resistance during use, which also makes the industrial plant structure unaffected by external environmental factors during use, resulting in problems in the stability and durability of the structure.

(3) Steel structure materials have high strength, low investment cost and can be recycled for many times, which makes the steel structure industrial plant have good environmental protection and energy conservation functions and lays a solid foundation for the sustainable development of China's social economy.

1.2. Design principle of steel structure industrial plant.

In the design of industrial plant with steel structure, materials, structural schemes and structural measures shall be reasonably selected based on the actual situation of the project, so as to meet the strength, stability and stiffness requirements of structural members during transportation, installation and use, meet the requirements of fire prevention and corrosion prevention, give priority to general and standardized members, and reduce the production and installation workload. The design service life of the building structure shall be indicated in the steel structure design document. Brand number of steel used. Model (or steel grade) of connecting material.

2. Main features of structural design of steel structure industrial plant.

Steel structure workshops are widely used all over the world, especially in developed countries. Steel structure workshop is generally applicable to warehouse, industrial workshop, exhibition hall, purification workshop and supermarket. The main features of its design are as follows:

① Large space and span, light building mass and high strength;

② The most advanced method is generally used in the design, which can fully meet the requirements of steel for impact, deformation, seismic resistance, rigidity, etc;

③ The steel structure building can be reused, and it is very convenient to move, avoid the waste of a large amount of steel, and protect the environment from pollution;

④ The steel structure is unique and light, with small actual occupation area and wide application area, which increases the use space in the building;

⑤ Standard components, excellent production, convenient and fast installation, effectively shorten the construction period and reduce the investment cost;

⑥ After reliable fire prevention and corrosion prevention measures are taken, it has high fire resistance and strong corrosion resistance.

3. Design status and Optimization Countermeasures of steel structure industrial plant.

In the process of stability research of steel structure factory building, the most critical content is the coupling effect of axial force and bending moment, and then the relationship between global stability and local stability. At present, the safety factor in the design of steel structure workshop cannot reflect the relationship between the whole and the part. The structural parameters are uncertain, the structural responses are significantly different, and the structural extreme values of random parameters are in an unstable state. Therefore, the design of steel structure plant should be constantly optimized to improve its service performance and safety performance.

3.1. Optimize steel insulation and fire protection.

Steel has high thermal conductivity, with a thermal conductivity of 50W (M. ℃). When it is heated above 100 ℃, its tensile strength will decrease and its plasticity will increase; When the temperature reaches 250 ℃, the tensile strength of the steel will increase slightly, but the plasticity will decrease, and blue brittle phenomenon will appear; When the temperature reaches 500 ℃, the strength of steel will be reduced to a very low level, leading to the collapse of steel structures. Therefore, when the ambient temperature of the steel structure reaches above 150 ℃, thermal insulation and fire protection design must be carried out. The general method is: steel structure is wrapped with fire-resistant brick, concrete or hard fire-proof board. Or the steel structure shall be coated with thick fire-retardant coating, and the thickness shall be calculated according to the technical specification for fire-retardant coating of steel structure.

3.2. Optimize the elevation design of steel structure industrial plant.

Light steel structure buildings mainly have the following four aspects: scale, line, color and change.

The facade of the steel structure industrial plant is mainly determined by the process layout. While meeting the process requirements, the facade should be simple and magnificent to make the nodes as simple and unified as possible. The color profiled steel plate makes the light steel plant building light in volume and rich in color, which is obviously superior to the single weight of the traditional reinforced concrete structure. In the design of light steel plant, jump color and cold color are often used, and the main entrance and exit, outer gutter, edge flashing and other places are highlighted, which not only reflects the magnificent momentum of modern plant, but also enriches the facade effect.

In the traditional industrial plant with reinforced concrete structure, the external wall is maintained as brick masonry, and the external wall is decorated with paint or face brick, supplemented by color bands. Because the lighting window on the concrete roof is not ideal, a large number of lighting windows are usually set on the wall in the design. However, this is not the case for the steel structure plant with color pressure steel plate as the maintenance wall. Lines are the most unique feature of the light steel structure architectural style. The lines are uniform or horizontal or vertical, which makes the light steel structure buildings have smooth metal texture and reflect a strong modern industrial atmosphere.

3.3. Optimize the support system of steel structure industrial plant.

During the layout of the inter column support system and roof support system of the steel structure industrial plant, it shall be determined according to the actual vibration equipment, tonnage, span, structural form, column grid setting, height and crane setting. Generally speaking, purlins that do not consider the roof structure are mainly set on vertical supports. In the non purlin system, the roof slab shall be welded with the roof to achieve the purpose of upper chord support. However, in the actual design process, due to the constraints of construction conditions. Considering the installation requirements, the top chord horizontal support system shall be set at the top chord position of the roof and the top chord position of the skylight frame. At the same time, when the spacing between the frames of the power house exceeds 12M, or when special vibration equipment and bridge cranes are installed, the longitudinal horizontal support system shall be installed.

3.4. Optimize the roof design of steel structure industrial plant.

In the roof design of steel structure workshop, the main content is waterproof. Roof waterproof design mainly considers three factors: first, roof slope; Second, gutter form; The third is the length of single slope roof. Relevant roof engineering technical standards have been implemented. In actual projects, the roof slopes of many plants are between (2% ~ 3%), which meets the actual requirements. Considering the material performance, node treatment, technology and other factors, the slope should be set at 5%. In snow covered areas, the slope should be increased, and the length design of the single slope roof of the steel structure plant should pay attention to the temperature difference and rainfall change in the area. According to relevant engineering design data, the length of the single slope roof shall be controlled below 70m to ensure the service performance of the plant. When this standard value is exceeded, special treatment should be carried out. At present, there are two kinds of steel structure roof design schemes: one is to use double-layer color profiled steel sheet, whose thermal insulation cotton is helpful to waterproof, but the temperature changes greatly, which is difficult to solve the problem of thermal expansion and cold contraction; The second is the composite flexible steel roof system composed of insulation layer, vapor barrier layer and coiled material waterproof layer, which helps to improve the conditions of thermal expansion and cold contraction.