Steel Reinforcements: Applications, Uses, and Specs

STEEL REINFORCEMENTS
OBJECTIVE OF THE ACTIVITY: This activity will encourage estimators to look into the
different methods to be used in estimating RSBs for their different uses. It will also nurture
understanding on the different provisions on hooks, bends and splicing as stipulated in the
National Structural Code of the Philippines. Further, the students will be able to develop
patience in conducting quantity take-offs.
Types of Rebars Commonly Used in Construction

Applications, Uses, and Specs
Reinforcing steel bars are used to help concrete withstand tension forces. Concrete is
sufficiently strong to compression forces by nature, but tension forces can crack it.
Deformed rebars on reinforcing steel have been a standard requirement since 1968, but
plain rebars are also used in situations where the reinforcing steel is expected to slide.
This is typically the case when they're installed in highway pavement and segmental
bridges.
The deformed pattern on a rebar helps the concrete adhere to the reinforcing steel surface.
The pattern on a deformed bar isn't specified, but the spacing and the height of the
"bumps" are regulated.
Rebar: Reinforcing Steel Bar Specifications

Reinforcing bars are hot-rolled using different steel materials. Most rebars are rolled from
new steel billets, but others are rolled from steel debris or railroad rails. Rebars are
required to contain some sort of identification that can be used to identify the mill that
produced the reinforcing steel bar.
The American Society for Testing and Materials (ASTM) has created a standard
identification ruling that all rebars must comply with:
 The number must identify the bar size.

 The type of steel symbol must be noted. For example, "N" means the bar was
rolled from a new billet, "W" stands for weldable steel, and "A" designates rolled
axle steel.
 The rebar grade identification must be cited: This is either 60 or 75, or metric 420
or 520. The grade indicates the rebar yield strength.
 A symbol identifying the manufacturer that rolled the bar must be included: This
is usually a single letter or a plain symbol.
Lower-strength reinforcing steel bars have only three marks that identify the mill that
produced the bar, the rebar size, and the type of steel used. High-strength reinforcing
steel uses a continuous line system to show steel grade. If the rebar contains two lines, it
indicates that the rebar was rolled into the 75,000-psi bars. When a single line is present,
it represents a 60,000-psi bar.
Types of Rebar
Carbon Steel Rebars: This is the most common type of rebar and is sometimes
referred to as a "black bar." It's extremely versatile but it corrodes more easily than other
types, making it inappropriate in areas that are subject to high humidity or in structures
that are frequently exposed to water. Many consider carbon steel rebars to be the best
option in all other types of construction, however.
Welded Wire Fabric: Welded wire fabric (WWF) is made from a series of steel
wires arranged at right angles and electrically welded at all steel wire crossings. It can be
used in slab-on-ground slabs where the ground has been well compacted. A heavier
fabrication of welded wire fabric can be used in walls and structural floor slabs. This is
commonly used in road pavement, box culverts, drainage structures, and in small
concrete canals.
Sheet-Metal Reinforcing Bars: Sheet-metal reinforcement is commonly used in

floor slabs, stairs, and roof construction. Sheet-metal reinforcing is composed of annealed
sheet steel pieces bent into corrugations of about one-sixteenth of an inch deep with holes
punched at regular spacing.
Epoxy-Coated Rebars: Epoxy-coated rebars are expensive and used in areas that

will be in contact with salt water or where a corrosion problem is imminent. The only
problem is that the coating can be very delicate, so bars should be ordered from a
reputable supplier.
European Rebars: These rebars are typically made of manganese so they tend to

bend more easily. They're not suitable for use in areas that are prone to extreme weather
conditions or geological effects, such as earthquakes, hurricanes, or tornadoes. They can
be cost-effective, however.
Stainless Steel Rebars: Stainless steel can be used as an alternative reinforcing

steel bar with carbon steel reinforcement. Using stainless steel reinforcing bars will not
create galvanic corrosion, and it can be a cost-effective solution in areas subject to
corrosion problems or where repair is difficult and expensive. These rebars will cost at
least eight times more than epoxy-coated rebars, however.
Galvanized Rebars: Galvanized rebars are 40 times more resistant to corrosion
than carbon steer rebars, making them ideal for structures that will be heavily exposed to
wet and humid conditions. They're pricey, however.
Expanded Metal or Wire Mesh Rebars: Expanded metal or wire mesh

reinforcement is another good product for concrete. Expanded metal is made by shearing
a sheet of steel into parallel lines that are then expanded to form a diamond shape or a
square shape between each cut. Expanded metal is commonly used as reinforcement in
areas where a considerable thickness of plaster is required, or to reinforce light concrete
construction. Wire mesh reinforcement can be used on sidewalks, small concrete pads, or
walkable surfaces that don't receive high live or load charges.
Glass-Fiber-Reinforced-Polymer (GFRP) Rebars: Similar to carbon fiber,

GFRP rebars will not corrode — ever, under any conditions. You'll pay dearly for that,
however. These rebars can run 10 times the cost of epoxy-coated rebars.
STEEL REINFORCEMENT ESTIMATION

(Also, refer to Fajardo’s book pages 87-142)
Estimation of steel reinforcement quantity is a necessary step in calculating cost of

RCC structure along with other building materials as per construction drawing.
Accurate calculation of reinforcement in the building plays an important role in

the overall costing of the project. The estimation of the reinforcement is made from the
drawings and bar bending schedule.in the cases where there is no availability of drawings
and schedules, the quantity is normally described in accordance with the requirements of
the Standard method of measurement of building works.
Methods of Reinforcement Quantity Estimation:

 There are different methods for estimating the quantities of reinforcement; three
methods of varying accuracy are:
Method-1 : Reinforcement Estimation (Thumb Rule
Method)
 This simplest method is based on the type of structure and the volume of the
reinforced concrete elements.
 Average values for typical concrete frames:
 Heavy industrial = 130 kg/m 3
Commercial = 100 kg/m 3
Institutional = 90 kg/m 3
 Residential = 85 kg/m 3
 However, while this simplest method to check on the total estimated quantity if
reinforcement, same time it is the least accurate and it requires considerable
experience to breakdown the tonnage down to Standard Method of Measurement
requirements. Some of the elements breakdown is given below,

 Standard Method of Measurement
Method-2 : Reinforcement Estimation (Accurate

Method):
 This is the most accurate method for quantity estimation of reinforcement. This
method requires the drawings and schedules. The drawings used in this estimation
are the representative of actual structure. The sketches include the intended form
of detailing and distribution of main and secondary reinforcement. An allowance
of additional steel for variations and holes may be made by inspection.
 Let us take an example and estimate the quantity of reinforcement in method,

 Reinforcement Details of a Typical Beam
 Cross Section of a Typical Beam

 Calculation:
 Bar 1:
 b = 4000 + (2 x 230) – (2 x 40) = 4380
 No bends, hence, no deductions
 Cutting Length = 4380 mm
 Bar 2:
 a = 200
 b = 4000 + (2 x 230) – (2 x 40) = 4380
 Deduction :
 (2 x dia x no. of bends) = 2 x 20 x 2
 Cutting Length = (2×200) + (4380) – (2 x 20 x 2) = 4700 mm
 Bar 3:
 a = 230 – (2×40) = 140
 c = 375 – (2×40) = 285
 Cutting Length:
 (2A + 2C) + 24d = (2x 140 + 2x 285) + 24×8 = 1042 mm
 No. of Stirrups: (4000/180) + 1 = 23.22 = 24
 Bar Bending Schedule for the Beam

 Number of bars:
 Suppose the spacing of stirrups is 150 c/c and the length along which they are
placed is 6800 mm, we can find the number of bars by the formula below
 [ Length / Spacing] + 1 = number of bars
 [ 6800 / 150] + 1 = 46.33
 In this case, we always round up. Hence, we require 47 stirrups.
 Cutting Length:
 We must remember than steel is ductile in nature and is subject to elongation.
Hence, the length of a bar is increased when bends or hooks are introduced.
Hence, certain deductions are needed to offset this increase in length.
 Cutting Length = True Length of a bar – Deductions
 For 45 degree
Cutting length = Total length – 1 x Dia of bar x No. of bends
 For 90 degree
Cutting length = Total length – 2 x Dia of bar x No. of bends
 For stirrups:
 90 degree hook:
 Length of stirrup = (2A + 2B) + 20 x dia
 135 degree hook:
 Length of stirrup = (2A + 2B) + 24 x dia
 Quantity Estimate for Reinforcement in Kg:

 Quantity Estimation of Reinforcement in Kg

 **Unit weight in kg/m is calculated using the formula = D /1622
 For 8mm bar = 8 /162
2
 = 64/162
 = 0.395 kg/m
Exercise 1:
Both Ends Midspan
L/4 L/4
1. Consider beam reinforcement shown. The length of the beam is 5.0 m. Estimate the
no. of 16-mm diameter RSB x 6.0m length to be used for the said beam. If for
instance the designer has calculated that the spacing for stirrups is 2@50mm,
4@100, the rest is 300. Is he correct? If yes, give your proof. If no, likewise. Then
estimate the no. of 10-mm diameter 6-m.
2. Suppose the beams to be constructed will be 3-bays at 5.0m at center of the column,
calculate the number of 16-mm diameter needed for the said beam. Integrate the
lap splicing which is needed since you are to utilize a 6.0m length only as other
lengths are not available at the moment (assumption only, not really true all the
time). Also include the bends at the ends of the beam (start and terminated ends, in
this case first span and third span are its start and terminal).
Exercise 2:
1.25 m
1. Refer to figure given. Sorry for the drawing I don’t have AUtocad at the moment.
Installers are not available at this time. The footing design is 1.25 x 1.25m and
300mm thick. Is the extended hook needed? Why, or why not?
2. Supposed the hook is based on Figure 3-7 page 103 of Fajardo and use Illustration
3-4 as your basis for the computation of the number of 16-mm needed.
3. There are 25 footings to be constructed of the same sizes as above, calculate the total
number of 16-mm x 6.0m length RSB to be utilized for the footing.
Exercise 3. Do problem exercises 1-5 pages 139 to 142 of Fajardo’s.
Please use the format:
SURNAME_GIVEN NAME_ACTIVITY 3_STEEL REINFORCEMENT as your filename.
DUE: JULY 11, 2020

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STEEL REINFORCEMENTS

Types of Rebars Commonly Used in Construction

Rebar: Reinforcing Steel Bar Specifications

 The number must identify the bar size.

Sheet-Metal Reinforcing Bars: Sheet-metal reinforcement is commonly used in

Epoxy-Coated Rebars: Epoxy-coated rebars are expensive and used in areas that

European Rebars: These rebars are typically made of manganese so they tend to

Stainless Steel Rebars: Stainless steel can be used as an alternative reinforcing

Expanded Metal or Wire Mesh Rebars: Expanded metal or wire mesh

Glass-Fiber-Reinforced-Polymer (GFRP) Rebars: Similar to carbon fiber,

STEEL REINFORCEMENT ESTIMATION

Estimation of steel reinforcement quantity is a necessary step in calculating cost of

Accurate calculation of reinforcement in the building plays an important role in

Methods of Reinforcement Quantity Estimation:

Commercial = 100 kg/m 3

 Standard Method of Measurement

Method-2 : Reinforcement Estimation (Accurate

 Reinforcement Details of a Typical Beam

 Cross Section of a Typical Beam

 Bar Bending Schedule for the Beam

 Quantity Estimation of Reinforcement in Kg

Both Ends Midspan

Exercise 3. Do problem exercises 1-5 pages 139 to 142 of Fajardo’s.

Please use the format:

SURNAME_GIVEN NAME_ACTIVITY 3_STEEL REINFORCEMENT as your filename.

DUE: JULY 11, 2020

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