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Structural Concrete - Hassoun

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346 Chapter 10 Axially Loaded Columns<br />

Figure 10.3<br />

Arrangement of bars and ties in columns.<br />

5. The minimum diameter of spiral bar is 3 in. (ACI Code, Section 25.7.3.2), and their clear<br />

8<br />

spacing according to ACI Code, Section 25.7.3.1 should not be more than 3 in. nor less than<br />

1 in. or 4/3 the nominal maximum size of coarse aggregate. Splices may be provided by welding<br />

or by lapping the deformed uncoated spiral bars by 48 diameters or a minimum of 12 in.<br />

(ACI Code, Section 25.7.3.6). Lap splices for plain uncoated bar or wire = 72d p ≤ 12 in. The<br />

same applies for epoxy-coated deformed bar or wire. The Code also allows full mechanical<br />

splices. ACI Code, Table 25.7.3.56 gives details for the different cases.<br />

6. Ties for columns must have a minimum diameter of 3 in. to enclose longitudinal bars of no.<br />

8<br />

10 size or smaller and a minimum diameter of 1 in. for larger bar diameters (ACI Code,<br />

2<br />

Section 25.7.2).<br />

7. Center to center spacing of ties shall not exceed the smallest of 48 times the tie bar diameter,<br />

16 times the longitudinal bar diameter, or the least dimension of the member. Clear spacing<br />

of ties should be at least 4/3 the nominal maximum size of the aggregate. Table 10.1 gives the<br />

spacing for no. 3 and no. 4 ties. The Code does not give restrictions on the size of columns to<br />

allow wider utilization of reinforced concrete columns in smaller sizes.

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