Fracture point
The fracture point (similar to the yield point) describes a solid material’s elastic limit, which is the maximum stress per unit area it can withstand before there is permanent deformation or fracture. In other words, it is the limit of the material’s elasticity, for up to that point, the solid can resume its original shape when the load is removed; after that point, it undergoes permanent (plastic) deformation and will not return to its original shape even after the load (yield load) has been removed. For example where a timber beam might bow under a weight but will return to its original straight shape once the load is removed.
However no structural material exhibits perfect elasticity: depending on the type of structure and the material, permanent deformations are often unavoidable whenever loads exceed certain values. That is why engineers design structures to ensure the materials are being used within their elastic range and the loads involved will not produce permanent deformations. All structural materials behave plastically beyond their elastic range.
However, even if some materials show elastic behaviour, they may – after a long period of service, usually many years – exhibit a degree of plastic flow (or creep). In the example of the timber beam bowing, if the weight remains for sometime and is then removed the beam may remain bowed, showing signs of creep, this may also be the case with timber beams bowing over time from a combination of self weight, angle of cut and drying out.
On a graph showing a stress-strain curve, the point of the limit of elastic behaviour is called the ‘yield point’ and this is where plastic deformation begins – some of this deformation will be plastic and irreversible. In structural engineering, the yield point is regarded as a ‘soft failure’ mode which does not usually cause catastrophic or ultimate failure, it might be described as ductile fracture depending on the material, or a brittle fracture. This is effect the fracture point, where the material starts to break, either gradually or quickly, the behaviour depending on the material and stresses, the breaking point might be where a timber beam goes beyond, the yield, soft or ductile failure and brittle or fracture points to break and collapse.
[edit] Related articles on Designing Buildings
- Brittle fracture.
- Concept structural design.
- Detailed design.
- Ductile fracture.
- Elements of structure in buildings.
- Elasticity.
- Elastic limit.
- Moment.
- Stiffness.
- Structural engineer.
- Structural principles.
- Structural systems for offices.
- Structural vibration.
- Structures at the end of their design life.
- The development of structural membranes.
- Types of structural load.
- Vibrations.
- Yield point.
Featured articles and news
What it is and how to use it.
Investors in People: CIOB achieves gold
Reflecting a commitment to employees and members.
Scratching beneath the surface; a guide to selection.
ECA 2024 Apprentice of the Year Award
Entries open for submission until May 31.
UK gov apprenticeship funding from April 2024
Brief summary the policy paper updated in March.
For the World Autism Awareness Month of April.
70+ experts appointed to public sector fire safety framework
The Fire Safety (FS2) Framework from LHC Procurement.
Project and programme management codes of practice
CIOB publications for built environment professionals.
The ECA Industry Awards 2024 now open !
Recognising the best in the electrotechnical industry.
Sustainable development concepts decade by decade.
The regenerative structural engineer
A call for design that will repair the natural world.
Buildings that mimic the restorative aspects found in nature.
CIAT publishes Principal Designer Competency Framework
For those considering applying for registration as a PD.
BSRIA Building Reg's guidance: The second staircase
An overview focusing on aspects which most affect the building services industry.
Design codes and pattern books
Harmonious proportions and golden sections.
Introducing or next Guest Editor Arun Baybars
Practising architect and design panel review member.