What is the term used to describe the loss of stress that occurs over time while concrete is held at a constant strain?

The term that describes the loss of stress that occurs over time while concrete is held at a constant strain is relaxation. Relaxation refers to the gradual decrease in stress that a material experiences when it is subject to a constant strain or deformation for a prolonged period. This phenomenon is particularly relevant in materials like concrete, where factors such as creep and shrinkage contribute to the reduction of internal stresses over time.

Understanding relaxation is important in the design and analysis of structures, as it can affect the long-term performance and stability of concrete elements. By recognizing how concrete behaves under sustained loads, engineers can make informed decisions about material selection, structural design, and load management to ensure safety and longevity.

The other terms, while related to material properties, don't accurately describe this specific phenomenon. Resilience refers to a material's ability to absorb energy when deformed and return to its original shape. Elasticity describes the ability of a material to return to its original shape after the removal of a load that caused deformation. A soft story is a structural term referring to a level in a building that has significantly less stiffness compared to the levels above or below it, often leading to performance issues during loading scenarios.