What Is Elastic Limit?

The elastic limit refers to the metal material's external force (pulling force) to a certain limit. If the external force is removed, its deformation (elongation) disappears and returns to its original state. The elastic limit refers to the ability of the metal material to resist the external force of this limit. If it continues to be used When the tensile force is enlarged, the object will be plastically deformed until it breaks. (Take a round bar tensile sample, as the tensile force increases, the round bar sample will elastically deform; if the tensile force exceeds the elastic limit, the round bar sample will begin to yield. The tensile force continues to increase until the tensile limit is reached, and the rod breaks.

When a material is subjected to a tensile test, stress and strain will show a functional relationship. When the stress reaches a certain value, the material will not return to its original state by itself. This stress value is called the elastic limit. If the stress on the material is less than the elastic limit, it can return to its original state by itself.

The stress at which a material transitions from elastic deformation to plastic deformation depends on the resistance of the material to plastic deformation.

Elastic limit

The maximum stress that the material can withstand without leaving any permanent deformation, expressed in kg / cm2 [Pa]

Note: In the actual measurement of strain, a small load is often used instead of zero load as the final or initial reference load.

Concrete-filled steel tubes have outstanding advantages such as high bearing capacity, good seismic performance, saving steel, and simple construction. Therefore, in recent years, they have been popularized and developed in high-rise buildings and developed rapidly. Research on concrete-filled steel tubes has also become a hot spot in the field of civil engineering.

What we usually refer to as concrete-filled steel tube refers to round concrete-filled steel tube. The basic principle of concrete-filled steel tube is to make the core concrete in a three-way compression state by means of the hoop restraining effect of the round steel tube on the core concrete, so that the core concrete has higher compressive strength and compressive deformation capacity. However, the concrete-filled steel tube does not exist or has a small hoop restraining effect in the initial stage of compression (that is, the elastic working stage). Therefore, the elastic limit point is an approximate starting point for the restraint effect of the ferrule, and it is also a characteristic point of the concrete-filled steel tube axial compression member-typical relationship curve. How to obtain the axial pressure at this point becomes very important. Attempts will be made to find a simple and practical approach to this point axis pressure calculation.

Since the elastic limit point of concrete-filled steel tube is very close to the starting point of the restraining effect of ferrule, here for simplification, the axial pressure calculation formula of concrete-filled steel tube column ferrule restraining effect is used instead of the axial limit calculation formula of elastic limit point. ^[1]