why the steel bars in concrete are round why not diamond shape of rect 2

[wzaka]

Respected Sir,
Why the bars use for reinforcement are round , why they are not diamond shape or rectangular shape , can there any other shape if yes which shape .

 

[Ron]

Long ago bars were various shapes, starting with square and occasionally hexagonal.

In bending, rebars with corners create significant stress concentrations on the concrete, thus failing the bond. This condition does not occur with round bars under normal loading. Additionally, if other than round, there would be some preferential orientation of the rebar, which makes for difficult construction.

Also, when bending the rebar, square or other corners tend to fracture. Another reason that round cross-sections are used.

Ron

 

[Gourile]

Dear wzaka,
In addition to the reasons explained by Ron, lower cost of rolling and deforming for round bars might be a good reason for their extensive usage.

 

[ADT]

Square-twist bar used to be used in European and Australasian areas because it was easy to obtain as Mild Steel square bar which was then Cold Worked by the action of twisting. This gave a helical shape longitudinally which was also very good for concrete bond reasons.
Usually only the small bar sizes were twisted because the machine necessary became too large, in those days. Later this pattern was pretty much superseded by deformed bar, which is also (always??) cold worked by twisting.
Any other eccentric or singly-symmetrical shape will cause placement problems ... a bar has to (at least) have the same section properties in two orthogonal directions. Anthony Tugwell
Project Director & Consulting Engineer - now in Australia