Design Considerations for Economical Formwork - Simplified Design of Reinforced Concrete Buildings - page 261

9.4 ECONOMICAL ASPECTS OF VERTICAL FRAMING

9.4.1 Walls

Walls provide an excellent opportunity to combine multiple functions in a single element; by doing this, a more
economical design is achieved. With creative layout and design, the same wall can be a fire enclosure for stair
or elevator shafts, a member for vertical support, and bracing for lateral loads. Walls with rectangular
cross-sections are less costly than nonrectangular walls.

9.4.2 Core Areas

Core areas for elevators, stairs, and utility shafts are required in many projects. In extreme cases, the core may
require more labor than the rest of the floor. Standardizing the size and location of floor openings within the
core will reduce costs. Repeating the core framing pattern on as many floors as possible will also help to
minimize the overall costs.

9.4.3 Columns

Although the greatest costs in the structural frame are in the floor system, the cost of column formwork should
not be overlooked. Whenever possible, use the same column dimensions for the entire height of the building.
Also, use a uniform symmetrical column pattern with all of the columns having the same orientation. Planning
along these general lines can yield maximum column economy as well as greater floor framing economy
because of the resulting uniformity in bay sizes.

9.5 GUIDELINES FOR MEMBER SIZING

9.5.1 Beams

• For a line of continuous beams, keep the beam size constant and vary the reinforcement from span to span.

• Wide flat beams (same depth as joists) are easier to form than beams projecting below the bottom of the
joints (see Fig, 9-4).

Beam

Joist

Wide flat beams are
more ecomonical than
narrow, deep beams

Figure 9-4 One-Way Joist Floor System