What is development length?

Question

Accepted Answer

Development length is the minimum length of reinforcement required to transfer the stress from reinforcing bar to concrete.

It is the length of the bar that must be embedded in concrete to develop its full strength.
It is influenced by the diameter of the bar, the strength of the concrete, and the bond strength between the bar and the concrete.
It is calculated using the formula Ld = (phi x Fy x As) / (4 x tau x sqrt(f'c)).
Ld is the development length, phi is the diameter of the bar, Fy is the yield strength of the bar, As is the area of the bar, tau is the bond stress, and f'c is the compressive strength of the concrete.
For example, if a #5 bar (diameter of 5/8 inch) with a yield strength of 60 ksi is used in concrete with a compressive strength of 4 ksi and a bond stress of 100 psi, the development length would be approximately 24 inches.

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