For example, machining tools need high strength and hardness of steel; Some petrochemical equipment need steel to have high temperature and corrosion resistance; Some machine parts need gantry punch with high strength, wear resistance and medium toughness, etc. there are many kinds of materials, such as carbon steel has more than 100 kinds and alloy steel has more than 300 kinds. But steel suitable for building steel structure is only a small part of the steel used as building steel structure must have the following properties.
The higher tensile strength and the yield point F yield point can reduce the section of the member, reduce the weight of the structure, save the steel and reduce the cost. Tensile strength. High can increase the safety reserve of the structure, improve the plasticity, toughness and fatigue resistance of the structure with better reliability, which can cause large deformation before the failure, and give obvious damage omen, so that people can find and take remedial measures in time to reduce the loss.
The plastic properties of gantry punch can also adjust the local peak stress, and make the internal force redistribution of the structure, make the stress of some parts of the structure or component with different stress become uniform, and improve the bearing capacity of the structure. The better toughness can make the structure absorb more energy when it is damaged under the dynamic impact load, and reduce the risk of brittle failure. The better fatigue resistance can make the structure have better resistance to repeated load because the gantry punch has to be subjected to various functions in the process of use, Therefore, steel must have the ability to resist various functions. The mechanical properties of steel are called mechanical properties (also called mechanical properties) of steel under various actions, such as strength, plasticity and toughness. The mechanical properties of steel are measured by the mechanical properties of the steel machine Acer. The mechanical properties of steel are the important basis for the design of gantry punch. These indexes are mainly measured by tests.
The impact toughness of gantry punch is not only related to the quality of steel and the shape of the specimen notch; And the impact toughness will decrease sharply when the temperature is lower than a negative temperature. Therefore, the steel structure design specification has made the normal temperature and low temperature regulations for the impact toughness of steel.
When designing important structures under low temperature, especially those under dynamic load, not only the impact toughness at room temperature (20 ℃) is required, but also the impact toughness design at low temperature (-20 ℃ or 140 ℃), the corresponding requirements of impact toughness index shall be put forward according to the specific use of the structure.
Many large span grids have been built in China, some of which have reached the advanced level in the world. Based on the development of gantry punch structure, the reticulated shell structure is being studied and developed, and many large-span latticed shell structures have been successfully built. Suspension structure is a kind of structure which takes full advantage of material characteristics and is very reasonable in force by using high strength steel cable tension concrete. The gantry punch structure can adapt to many plane shapes and have unique shape and more economical steel.
