What is anchorage length?

Anchorage length is the length of embedded reinforcement or bar beyond the critical section in order to develop design strength of reinforcing bar (rebars). It is the minimum length over which the reinforcement must extend beyond the point where the full design stress is required, so that the steel may be stressed to its full working value with safety against slip.

Anchorage is provided to transfer the force from the reinforcement to the concrete. The bond length or the anchorage length of a rebar is required for the development of the tensile strength of the bar through bond with the concrete. Bond length is required at both ends of a bar.

The anchorage length is determined based on the bar diameter, the grade of steel, and the concrete strength. The anchorage length is also affected by the type of concrete member (i.e., beam or column) and the distance from the support to the point where the full design stress is required.

The anchorage length is important because it ensures that the reinforcement will not slip and that the concrete will not crack or spall. The anchorage length is a critical design parameter that must be carefully considered in the design of reinforced concrete structures.

The required development length ld for tension members is calculated using the following formula:

ld = (fy/0.85 f'c) db (for deformed bars)

ld = (fy/4 f'c) db (for plain bars)

where:

fy = yield strength of the rebar

f'c = compressive strength of the concrete

db = diameter of the rebar

The development length for compression members is calculated using the following formula:

ld = (0.05 fy/0.85 f'c) db (for deformed bars)

ld = (0.02 fy/4 f'c) db (for plain bars)

where:

fy = yield strength of the rebar

f'c = compressive strength of the concrete

db = diameter of the rebar