Point of contraflexure
|
| The point of contraflexure (PoC) occurs where bending is zero and at the point of change between positive and negative (or between compression and tension). |
In a beam that is flexing (or bending), the point where there is zero bending moment is called the point of contraflexure. At that point, the direction of bending changes its sign from positive to negative or from negative to positive. (It may also be thought of as a change from compression to tension or vice versa).
For this change to happen, it must pass through zero – the point of contraflexure. On a bending moment diagram, it is the point at which the bending moment curve intersects with the zero line.
An analogy may be made with a speeding train travelling west on a single track. In order to reverse direction and travel east, it must decelerate, stop then accelerate in the opposite direction. The point it stops, even if momentary, is zero – the neutral point, where it is not travelling.
Theoretically, when considering a structural member under load, such as a reinforced concrete beam, the point of zero bending moment would seem to suggest no reinforcement would be required. However, omitting reinforcement at that point is considered inadvisable as, in a real-life situation, it may be difficult to locate the exact point of contraflexure.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
CIOB and CORBON combine forces
To elevate professional standards in Nigeria’s construction industry.
Amendment to the GB Energy Bill welcomed by ECA
Move prevents nationally-owned energy company from investing in solar panels produced by modern slavery.
Gregor Harvie argues that AI is state-sanctioned theft of IP.
Heat pumps, vehicle chargers and heating appliances must be sold with smart functionality.
Experimental AI housing target help for councils
Experimental AI could help councils meet housing targets by digitising records.
New-style degrees set for reformed ARB accreditation
Following the ARB Tomorrow's Architects competency outcomes for Architects.
BSRIA Occupant Wellbeing survey BOW
Occupant satisfaction and wellbeing tool inc. physical environment, indoor facilities, functionality and accessibility.
Preserving, waterproofing and decorating buildings.
Many resources for visitors aswell as new features for members.
Using technology to empower communities
The Community data platform; capturing the DNA of a place and fostering participation, for better design.
Heat pump and wind turbine sound calculations for PDRs
MCS publish updated sound calculation standards for permitted development installations.
Homes England creates largest housing-led site in the North
Successful, 34 hectare land acquisition with the residential allocation now completed.
Scottish apprenticeship training proposals
General support although better accountability and transparency is sought.
The history of building regulations
A story of belated action in response to crisis.
Moisture, fire safety and emerging trends in living walls
How wet is your wall?
Current policy explained and newly published consultation by the UK and Welsh Governments.
British architecture 1919–39. Book review.
Conservation of listed prefabs in Moseley.
Energy industry calls for urgent reform.