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• maximum cross-sectional dimension of the column = 30 in. ^ controls

Use #4 ties and crossties at 10 in. spacing within the lo region. In between lo, provide ties @ 20 in. spacing. Figure 4.37 provides a schematic reinforcement layout of column vertical bar and ties.

Figure 4.37. Design example, frame column; ordinary moment frame. Note: €o is the same as for columns of SMRF. There is no requirement to splice the column bars at mid-height.

4.2.9.5. Shear Wall Example: Seismic Design Category (SDC) A, B, or C

Although ACI 318-99 specifies certain seismic design and detailing requirements for intermediate moment frames (IMFs) there are no requirements for shear walls in buildings assigned to SDC A, B, or C. For these buildings, ACI considers that the requirements given in Chapters 1 through 18 and 22 are sufficient to provide a degree of toughness that is consistent with the seismic risk associated with zone 2 or for buildings assigned to SDC C.

The design procedure for a reinforced shear wall subject to bending and axial loads is a two-step process. First, generate an axial load-moment interaction diagram for the shear wall of given dimensions and concrete strength, with various percentages of reinforcement. This is done by taking successive choices of neutral axis distance measured from one face of the wall, and then calculating the axial force PU and the corresponding moment MU. Each sequence of calculations is repeated until the complete interaction diagram is obtained. The next step is the selection of reinforcement that satisfies the design requirement under loads and moments equal to or larger than the factored loads and moments. The formulation is based on the principles of ultimate strength design with a linear strain diagram that limits the concrete strain at the extremity of the section to 0.003. With the general availability of computers it is no longer tedious to establish axial load-moment interaction diagrams, Therefore, design for axial loads and moments is not discussed further in this section.

Given. A shear wall 24 ft. long and 12 in. thick with a floor-to-floor height of 14 ft.

Compressive strength of concrete f = 4000 psi

Yield strength of reinforcing bars fy = 60 ksi

Maximum factored shear force VU = 500 kips

Vertical reinforcement as determined for bending and axial loads = four # 7 @ 9 in. vertical at each end, and # 6 @ 15 vertical in between each face.

Required. Shear design using the provisions of ACI 318-99.

Solution.

Shear Design.

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