Where Bending Moment changes sign on Bending Moment Diagram.
In a bending beam, a point is known as a point of contra flexure if it's a location at which no bending occurs.
In a bending moment diagram, it is the point at which the bending moment curve intersects with the zero lines.
In other words where the bending moment changes its sign from negative to positive or vice versa.
A point of contra flexure occurs in the overhanging beam.
Important Point
Section
τmax/τavg
τNeutral axis / τavg
Rectangular/square
3/2
3/2
Solid circular
4/3
4/3
Triangle
3/2
4/3
Diamond
9/8
1
Shear centre:
The shear centre is the point through which if the resultant shear force acts then member is subjected to simple bending without twisting.
Location of shear centre:
(i) Shear centre generally does not coincide with the centroid of section except in special cases when the area is symmetrical bout both axis.
(ii) Shear centre always lies on the axis of symmetry if exists.
(iii) If there are two or more than two axis of symmetry exist, then shear center will coincide with point of intersection of axis of symmetry. In this case shear centre of area will be same as centroid of area.
(iv) If a section is made of two narrow rectangles then shear centre lies on the junction of both rectangles.
