Structural Concrete - Hassoun

286 Chapter 7 Development Length of Reinforcing Bars
Section 7.4
Development length in compression for all bars is
l dc = 0.02d bf y
λ √ ≥ 0.0003d b f y ≥ 8in. (Eq. 7.14)
f c
′
For specific values, refer to Tables 7.3 and 7.4.
Section 7.6
The critical sections for the development of reinforcement in flexural members are
• At points of maximum stress
• At points where tension bars are terminated within the span
• At the face of the support
• At points of inflection
Section 7.7
The minimum diameter of bends in standard hooks is
• For no. 3 to no. 8 bars, 6d b
• For no. 9 to no. 11 bars, 8d b
The development length l dh of a standard hook is
( )
0.02ψfy
l dh =
λ √ (d b )(modification factor)
f c
′
Section 7.8
1. For splices in tension, the minimum lap-splice length is 12 in. If (a) one-half or less of the total
reinforcement is spliced within the required lap-splice length and (b) the area of reinforcement
provided is at least twice that required by analysis over the entire length of the splice, then
l st = 1.0 l d = class A splice.
2. For all other cases, class B has to be used when l st = 1.3l d .
3. For splices in compression, the lap-splice length should be equal to or greater than l dc in
compression, but it also should satisfy the following: l sc ≥ 0.0005 f y d b (for f y ≤ 60,000 psi).
REFERENCES
1. L. A. Lutz and P. Gergely. “Mechanics of Bond and Slip of Deformed Bars in Concrete.” ACI Journal 68
(April 1967), pp. 711–721.
2. ACI Committee 408. “Bond Stress—The State of the Art.” ACI Journal 63 (November 1966).
3. ACI Committee 408. “Opportunities in Bond Research.” ACI Journal 67 (November 1970).
4. Y. Goto. “Cracks Formed in Concrete around Deformed Tensioned Bars.” ACI Journal 68 (April 1971).
5. T. D. Mylrea. “Bond and Anchorage.” ACI Journal 44 (March 1948), pp. 521–552.
6. E. S. Perry and J. N. Thompson. “Bond Stress Distribution on Reinforcing Steel in Beams and Pullout
Specimens.” ACI Journal 63 (August 1966).