Building Design and Construction Handbook - Merritt - Ventech!

9.26 SECTION NINE
stress, which depend on workmanship, are eliminated), and a vertically progressive
failure can be averted.
One indirect measure is to read deflections of successive floors at each stage.
With accurate measurements of E c, load per floor can then be estimated by structural
theory. A more direct measure (seldom used) is strain measurement on the shores,
usable with metal shores only. On large projects, where formwork cost and cost of
failure justify such expense, both types of measurement can be employed.
9.20 SPECIAL FORMS
Special formwork may be required for uncommon structures, such as folded plates,
shells, arches, and posttensioned-in-place designs, or for special methods of construction,
such as slip forming with the form rising on the finished concrete or with
the finished concrete descending as excavation progresses, permanent forms of any
type, preplaced-grouted-aggregate concreting, underwater concreting, and combinations
of precast and cast-in-place concreting.
9.21 INSPECTION OF FORMWORK
Inspection of formwork for a building is a service usually performed by the architect,
engineer, or both, for the owner and, occasionally, directly by employees of
the owner. Formwork should be inspected before the reinforcing steel is in place
to ensure that the dimensions and location of the concrete conform to design drawings
(Art. 9.16). This inspection would, however, be negligent if deficiencies in the
areas of contractor responsibility were not noted also.
(See ‘‘Guide to Formwork for Concrete,’’ ACI 347R, and ‘‘Formwork for Concrete,’’
ACI SP-4, for construction check lists, and ‘‘Manual of Concrete Inspection,’’
ACI SP-2.)
REINFORCEMENT
9.22 REINFORCING BARS
The term deformed steel bars for concrete reinforcement is commonly shortened
to rebars. The short form will be used in this section.
Standard rebars are produced in 11 sizes, designated on design drawings and in
project specifications by a size number. Since the late 1990’s, bar producers have
been manufacturing soft-metric rebars for use in both metric and inch-pound construction
projects. Soft metric rebars have the same physical features as the corresponding
inch-pound bars, i.e., the same nominal diameters and weight per foot
(Table 9.4). Soft metric bars are marked with the metric size number and the metric
grade of steel.