|
References |
|
|
Section 2.3
Reinforcing Steel
Last Revised: 04/07/2018
ACI 318-14 Chapter 20 provides the requirements for reinforcing steel. As this text deals with nonprestressed reinforced concrete, you can skip any references to prestressing when working problems in this text.
The reinforcing steel that is referred to in this text comes as round bars with deformations as shown in Figure 2.3.1. Bars are specified by their diameters.
|
|
|
Figure 2.3.1 |
ACI 318-14 20.2.1.1 requires that all bars, except those used in spirals, be "deformed" bars. The deformations referred to are the "bumps" found on reinforcing steel. The presences of these deformations enhances the mechanical bond between the steel and concrete.
The Concrete Reinforcing Steel Institute (CRSI) website has lots of valuable resource information about reinforcing steel. Their webstore has a number of references that are quite useful. You should check it out.
Also note that each bar, per ASTM specifications, is marked with a symbol from the producing mill, bar size, bar type, and grade. The CRSI website has information about the specifics of the markings at http://www.crsi.org/index.cfm/steel/identification.
The two most used mechanical properties for reinforcing steel are the specified yield strength, fy, and the modulus of elasticity, Es.
Specified Yield Strength, fy
In most cases the steel will have an fy of either 40 ksi or 60 ksi, with 60 ksi being the most common. Higher strengths are available, however, they are typically available only on special order. The "grade" of a bar is the specified yield strength of the bar in ksi. For example, a Grade 60 bar has fy=60 ksi.
Modulus of Elasticity, Es
ACI 318-14 20.2.2.2 allows Es to be 29,000 ksi. This is consistent with all steels.
Types of Rebar
ACI 318-14 20.2.1.3 lists the various ASTM steel types that are used for reinforcing bar. Take the time to review the section. Your choice of rebar will be dictated by the demands of your project. ACI 318-14 Table 20.2.2.4a will assist you in choosing the right bars for the right applications. Please take some time to review this table. You should also become familiar with what types and grades are commonly available in your area by talking with the local suppliers.
Rebar Sizes
ACI 318-14 Appendix A has a table of standard rebar sizes in USCU. The table also gives the nominal diameter, nominal area, and weight per foot. Metric standard bar sizes can be readily found using an internet search.
The rebar size designator is the number of eighths of an inch closest to the nominal diameter. For example a #3 bar has a nominal diameter of about 3/8", an number #10 bar has a nominal diameter of approximately 10/8". Note that the nominal diameter to be used in design is not always an even eighth of an inch and the nominal area is not necessarily computed from the nominal diameter. Consequently you should use the values as they are listed in the table as opposed to computing diameters and areas numerically from the size designators.
<<< Previous Section <<< >>> Next Section >>>