What is elasticity?
Elasticity is the property of a material to deform temporarily under load and to spring back fully to its original shape once that load is removed. It is a fundamental concept in construction, because almost every structural element must accommodate service loads without permanent damage.
How does elasticity work?
Under load, atoms or molecules in a material shift slightly relative to each other. In elastic behaviour:
- Stress and strain are proportional — doubling the force doubles the deformation
- No heat loss — energy is stored and released
- No permanent deformation — the material returns fully to shape
This behaviour is described by Hooke’s law: stress = E × strain, where E is the modulus of elasticity.
When does elasticity end?
Every material has an elastic limit. Above that stress:
- Plastic deformation occurs — a permanent change
- The material starts to yield or creep
- It may eventually fail
In steel, the yield point (onset of plasticity) is clearly defined. Concrete behaves largely linear-elastic up to about 40% of its failure load.
Application in construction
| Material | Elasticity | Application |
|---|---|---|
| Steel | High, well defined | Beams, columns, reinforcement |
| Concrete | Lower, with cracking | Floors, walls, foundations |
| Timber | Resilient, anisotropic | Trusses, beams, floors |
| Rubber / elastomer | Very high | Vibration isolators, bearings |
| Glass | Fully elastic until fracture | Glazing, glass structures |
Importance for the engineer
- Determining stiffness — to limit deflection
- Predicting vibrations — e.g. footbridges
- Seismic behaviour — elastic response absorbs energy
- Applying prestress — in prestressed concrete
Related terms
- Modulus of elasticity
- Elastic deformation
- Plasticity
- Plastic deformation
- Relaxation
Looking for more DIY plans? Check out fredsdiyplans.com.