Structural Detailing of Reinforcement for Economy - Simplified Design of Reinforced Concrete Buildings - page 239

The development length may be reduced when the provision for excess reinforcement given in ACI 12.2.5 are
satisfied. Also ˜ d must never be taken less than 12 in. (ACI 12.2.1).

Values for tension development length ˜ d are given in Table 8-1 for grade 60 reinforcing bars and concrete
strengths ranging from 3 to 6 ksi. The values in the table are based on bars that are not epoxy-coated and on
normal weight concrete. To obtain ˜ d for top bars (horizontal bars with more than 12 in. of concrete cast below
the bars) the tabulated values must be multiplied by 1.3 (ACI 1212.2.4). The cover and clear spacing referred
to in the table are depicted in Fig. 8-1.

As can be seen from the table, very long development lengths are required for the larger bar sizes, especially
when the cover is less than d b .

side
cover

cover, c

Clear space
s

d b

Transverse
reinforcement

Figure 8-1 Cover and Clear Spacing of the Reinforcement

Table 8-1 Tension Development Length for ˜ d Grade 60 Bars

Values are based on bars which are not epoxy-coated and on normal weight concrete. For top
Bars, multiply tabulated values by 1.3