For example, cutting tools for mechanical processing require high strength and hardness of steel; Some petrochemical equipment requires steel with high temperature and corrosion resistance; Some machine parts need gantry punch has a high strength, wear resistance and medium toughness and so on a wide variety of materials, carbon steel there are more than one hundred, alloy steel there are more than three hundred, but the steel suitable for building steel structure is only a small part of the steel used as building steel structure must have the following properties.

High tensile strength and yield point f high yield point can reduce the section of the component, reduce the weight of the structure, save steel, and reduce the cost. Tensile strength ∫. High can increase the safety reserve of the structure and improve the reliability of the structure. Good plasticity, toughness and fatigue resistance can make the structure produce a large deformation before the destruction, giving people an obvious warning of damage, so that people can find and take remedial measures in time to reduce losses.

The better plasticity of the gantry punch can also adjust the local peak stress, so that the internal force of the structure is redistributed, so that the stress of some parts of the structure or members with different forces tends to be uniform, and the bearing capacity of the structure is improved. Better toughness can make the structure absorb more energy when it is damaged under the action of dynamic impact load, and reduce the risk of brittle failure. Better fatigue resistance can make the structure have better resistance to repeated loads. Therefore, the steel must have the ability to resist various effects of the various characteristics of steel under various effects, such as strength, plasticity, toughness, etc., called the mechanical properties of steel (also known as mechanical properties). The mechanical properties of steel are measured by the performance index of steel machine. The mechanical properties of steel are important for the design of gantry presses. These indicators are mainly determined through tests.

The impact toughness of the gantry press is not only related to the quality of steel and the notch shape of the specimen. Moreover, the impact toughness is greatly affected by temperature, especially low temperature. When the temperature is lower than a certain negative temperature, the impact toughness will decrease sharply. Therefore, the impact toughness value of steel structure design code has been specified respectively at room temperature and low temperature.

When designing important structures under low temperature conditions, especially those bearing dynamic loads, it is not only required to ensure the impact toughness at room temperature (20 ° C), but also to ensure the impact toughness design at low temperature (-20 ° C or a 40 ° C), the corresponding impact toughness indicators should be proposed according to the specific use of the structure.

Many long-span grids have been built throughout the country, some of which have reached the world's advanced level. On the basis of the development of gantry punch structure, reticulated shell structure is currently being studied and developed, and many large-span reticulated shell structure houses have been successfully built. Suspension structure is a kind of structure which uses high-strength steel cable to be compressed by tensile concrete, makes full use of material characteristics, and has a very reasonable force. The structure of the gantry punch can adapt to a variety of plane shapes, and it is a kind of space structure with unique shape and more saving steel.