24.02.2017 Views

Structural Concrete - Hassoun

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

7.7 Standard Hooks (ACI Code, Sections 25.3 and 25.4) 275<br />

Figure 7.10<br />

Stress distribution in 90 ∘ hooked bar.<br />

2. With no cross wire within l d or with a single cross wire less than 2 in. from the point of critical<br />

section, ψ w = 1.0.<br />

Example 7.5<br />

Compute the development length required for the top no. 8 bars of the cantilever beam shown in Fig. 7.11<br />

that extend into the column support if the bars are<br />

a. Straight<br />

b. Have a 90 ∘ hook at the end<br />

c. Have a 180 ∘ hook at the end<br />

Figure 7.11 Example 7.5.<br />

The bars are confined by no. 3 stirrups spaced at 6 in. and have a clear cover = 1.5 in. and clear<br />

spacings = 2.0 in. Use f c ′ = 4ksi normal-weight concrete and f y = 60 ksi.<br />

Solution<br />

a. Straight bars: For no. 8 bars, d b = 1.0 in. Because clear spacing = 2d b and clear cover is greater<br />

than d b with bars confined by stirrups, then conditions a and b are met. Equation 7.10 can be used

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!