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Building Design and Construction Handbook - Merritt - Ventech!

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CONCRETE CONSTRUCTION 9.83<br />

FIGURE 9.27 Various arrangements of shear reinforcement.<br />

reinforcement is 1.5 in., instead of 0.75 in. as in st<strong>and</strong>ard joists. Minimum shear<br />

reinforcement is required. Shear carried by the concrete is 10% less than that allowed<br />

for st<strong>and</strong>ard joists. Draped two-way reinforcement in the top slab is permitted.<br />

The principal practical problem is providing shear reinforcement in the amounts<br />

required in the ribs—detailed for practicable placing in narrow sections. Vertical<br />

U-stirrups are acceptable, although practicable bending limitations may require that<br />

they be set at an angle to the longitudinal reinforcement. See Fig. 9.27. Single leg<br />

stirrups with alternating direction of the hooked ends have been considered. The<br />

ACI 318 <strong>Building</strong> Code also permits single leg, deformed or plain welded wire<br />

fabric (WWF) meeting special requirements. Figure 9.27 shows several possible<br />

details. Minimum shear reinforcement requirements will control in most cases, either<br />

throughout the span or at a short distance from supports.<br />

TWO-WAY SLAB CONSTRUCTION<br />

A two-way slab is a concrete panel reinforced for flexure in more than one direction.<br />

(See also Art.. 9.63.) Many variations of this type of construction have been used<br />

for floors <strong>and</strong> roofs, including flat plates, solid flat slabs, <strong>and</strong> waffle flat slabs.<br />

Generally, the columns that support such construction are arranged so that their

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