What are the characteristics of steel structure? Material requirements for steel structure
What are the characteristics of steel structure?
Material requirements for steel structure
Abstract: Steel structure is a structure composed of steel materials and is one of the main types of building structures. Steel structure has the characteristics of high strength, light weight, good overall stiffness, strong deformation ability, etc., so it can be used to build large span, super high and super heavy buildings. Material requirements for steel structure The strength index is based on the yield strength of steel. After the plasticity of steel exceeds the yield point, it has the property of significant plastic deformation without breaking.
What are the characteristics of steel structure
1. High material strength and light weight. Steel has high strength and high elastic modulus. Compared with concrete and wood, its density to yield strength ratio is relatively low. Therefore, under the same stress conditions, the steel structure has a small cross-section, light weight, easy transportation and installation, and is suitable for structures with large spans, high heights and heavy loads.
Material requirements for steel structure
1. Strength The strength index of steel is composed of elastic limit σe, yield limit σy, and tensile limit σu. The design is based on the yield strength of steel. High yield strength can reduce the weight of the structure, save steel and reduce construction costs. The tensile strength ou is the maximum stress that the steel can withstand before it is damaged. At this time, the structure loses its usability due to large plastic deformation, but the structure deforms greatly without collapsing, and should be able to meet the requirements of the structure to resist rare earthquakes.
2. Plasticity
The plasticity of steel generally refers to the property that after the stress exceeds the yield point, it has significant plastic deformation without breaking. The main indicators for measuring the plastic deformation capacity of steel are elongation ō and cross-sectional shrinkage ψ.
3. Cold bending performance
The cold bending performance of steel is a measure of the resistance of steel to cracks when plastic deformation is generated by bending processing at room temperature. The cold bending performance of steel is to use cold bending experiments to test the bending deformation performance of steel under a specified bending degree.
4. Impact toughness
The impact toughness of steel refers to the ability of steel to absorb mechanical kinetic energy during the fracture process under impact load. It is a mechanical property that measures the resistance of steel to impact load, which may cause brittle fracture due to low temperature and stress concentration. Generally, the impact toughness index of steel is obtained through impact tests of standard specimens.
5. Welding performance The welding performance of steel refers to the welding joint with good performance under certain welding process conditions. Welding performance can be divided into welding performance during welding and welding performance in terms of use performance. Welding performance during welding refers to the sensitivity of the weld and the metal near the weld to not produce thermal cracks or cooling shrinkage cracks during welding. Good welding performance means that under certain welding process conditions, neither the weld metal nor the nearby parent material will produce cracks. Welding performance in terms of use performance refers to the impact toughness at the weld and the ductility in the heat-affected zone, requiring that the mechanical properties of the steel in the weld and heat-affected zone should not be lower than those of the parent material. my country adopts the welding performance test method of the welding process and also adopts the welding performance test method in terms of use properties.
6. Durability
There are many factors that affect the durability of steel. The first is that the corrosion resistance of steel is poor, and protective measures must be taken to prevent corrosion and rust of steel. The protective measures include: regular maintenance of steel paint, use of galvanized steel, and special protective measures under strong corrosive media such as acid, alkali, and salt. For example, the offshore platform structure adopts "anodic protection" measures to prevent the corrosion of the jacket. Zinc ingots are fixed on the jacket, and the seawater electrolyte will automatically corrode the zinc ingots first, thereby achieving the function of protecting the steel jacket. Secondly, because the destructive strength of steel is much lower than the short-term strength under high temperature and long-term load, the long-term strength of steel under long-term high temperature should be measured. Steel will automatically become hard and brittle over time, which is the "aging" phenomenon. The impact toughness of steel under low temperature load should be tested.
