Suggestions for Design

Economy of concrete structures begins in the development

stage with designers who have a good understanding of formwork

logic. Often, two or more structural alternatives will meet the design

objective equally well. However, one alternative may be significantly

less expensive to build. Constructability, that is, making structural

frames faster, simpler, and less costly to build, must begin in the earliest

phase of the design effort.

Economy in formwork begins with the design of a structure and

continues through the selection of form materials, erection, stripping,

care of forms between reuses, and reuse of forms, if any. When a

building is designed, consideration should be given to each of the

following methods of reducing the cost of formwork:

1. Prepare the structural and architectural designs simultaneously.

If this is done, the maximum possible economy in

formwork can be ensured without sacrificing the structural

and architectural needs of the building.

2. At the time a structure is designed, consider the materials

and methods that will be required to make, erect, and remove

the forms. A person or computer-aided drafting and design

(CADD) operator can easily draw complicated surfaces, connections

between structural members, and other details;

however, making, erecting, and removing the formwork may

be expensive.

3. If patented forms are to be used, design the structural members

to comply with the standard dimensions of the forms

that will be supplied by the particular form supplier who will

furnish the forms for the job.

4. Use the same size of columns from the foundation to the roof,

or, if this is impracticable, retain the same size for several

floors. Adopting this practice will permit the use of beam and

column forms without alteration.

5. Space columns uniformly throughout the building as much

as possible or practicable. If this is not practicable, retaining

the same position from floor to floor will result in economy.

6. Where possible, locate the columns so that the distances between

adjacent faces will be multiples of 4 ft plus 1 in., to permit the

unaltered use of 4-ft-wide sheets of plywood for slab decking.

7. Specify the same widths for columns and column-supported

girders to reduce or eliminate the cutting and fitting of girder

forms into column forms.

8. Specify beams of the same depth and spacing on each floor

by choosing a depth that will permit the use of standard sizes of

lumber, without ripping, for beam sides and bottoms, and

for other structural members.

It is obvious that a concrete structure is designed to serve specific

purposes, that is, to resist loads and deformations that will be applied

to the structure, and to provide an appearance that is aesthetically

pleasing. However, for such a structure, it frequently is possible to

modify the design slightly to achieve economy without impairing the

usability of the structure. The designer can integrate constructability

into the project by allowing three basic concepts: design repetition,

dimensional standards, and dimensional consistency. Examples of

these concepts, excerpted from ref. [1], are presented in this chapter

to illustrate how economy in formwork may be affected.

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