Yield Strength

Summary

Yield Strength - Yield Strength of a material is the amount of stress it can take before it begins to deform plastically.

Technical Information

A material will initially deform elastically, but once it has surpassed its yield strength, it will deform plastically. For materials such as steel, which give a ductile failure response, the compressive and tensile yield strength are roughly equal.

Concrete however will fail at very low tensile stresses, the compressive strength far exceeds the tensile capacity.

The reasons for concrete’s considerable compressive strength compared to its tensile strength are:

When in compression, the aggregate and the paste both resist the stresses in the concrete. Stresses of 20-60+MPa can be withstood.
When in tension, only the cement paste resists the stresses. It will fail at stresses of 2-5MPa.

When designing for the ultimate limit state, the element is considered to fail at its yield stress. Hence, yield strengths often carry large safety factors in design.

A material visibly breaks at the ultimate tensile strength.