Reinforcing Steel

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  • Topic: Reinforced concrete, Concrete, Steel
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REINFORCING STEEL:
Reinforced concrete was designed on the principle that steel and concrete act together in resisting force. Concrete is strong in compression but weak in tension. The tensile strength is generally rated about 10 percent of the compression strength. Steel is the best material for reinforcing concrete because the properties of expansion for both steel and concrete are considered to be approximately the same; that is, under normal conditions, they will expand and contract at an almost equal rate. At very high temperatures, steel expands more rapidly than concrete and the two materials will separate. Another reason steel works well as a reinforcement for concrete is because it bonds well with concrete. Reinforcing steel must be strong in tension and, at the same time, be ductile enough to be shaped or bent cold. TYPES/FORMS:

* BARS OR RODS
* PLAIN BAR
* DOWELS AT EXPANSION JOINTS
* CONTRACTION JOINTS IN ROADS AND RUNWAYS
* COLUMN SPIRALS
* DEFORMED BAR
* MAIN REBAR
* STIRRUPS AND TIES
* COLUMN SPIRALS
* EXPANDED METAL or WIRE MESH
* WELDED WIRE FABRIC
* SHEET METAL

Table 2.1 – Reinforcement bar sizes and dimensions.
Source:http://www.sizes.com/materls/rebar.htm

Sizes and Dimensions |
old bar size | "soft"
metric
size | Weight in pounds per foot | nominal diameter in inches (not including the deformations) | #3| #10| 0.376| 0.375, that is, 3/8|
#4| #13| 0.668| 0.500, that is, 4/8|
#5| #16| 1.043| 0.625|
#6| #19| 1.502| 0.750, that is, 6/8|
#7| #22| 2.044| 0.875|
#8| #25| 2.670| 1.000, that is, 8/8|
#9| #29| 3.400| 1.128|
#10| #32| 4.303| 1.270|
#11| #36| 5.313| 1.410|
#14| #43| 7.650| 1.693|
#18| #57| 13.60| 2.257|

Grade and Diameter |
Grade | NOMINAL DIAMETER, mm |
230| 10| 12| 16| 20| 25| ---| ---| ---| ---| ---| 275| 10| 12| 16| 20| 25| 28| 32| 36| 40| ---|
415| 10| 12| 16| 20| 25| 28| 32| 36| 40| 50|
Plain Round Bars (For general purpose, forging and bright drawing) | Grade | NOMINAL DIAMETER, mm |
230/275/415| 10| 12| 16| 20| 25| 28| 32| 36| 40| 50| Commercial lengths for deformed bars |
Grade | Commercial Lengths, meter | Special Length, meter | All Grades| 6.0| 7.5| 9.0| 10.5| 12.0| 13.5| 15.0|

Source: NCDP Handbook

WELDED WIRE FABRIC (WWF)
USES IN REINFORCED CONCRETE CONSTRUCTION
* FLOOR SLABS ON WELL-COMPACTED GROUND
* HEAVIER FABRIC IS USED IN WALLS AND PRIMARY REINFORCEMENT IN STRUCTURAL FLOOR SLABS * ROAD AND RUNWAY PAVEMENTS
* BOX CULVERT
* CANAL LININGS

SHEET METAL REINFORCE MAT
USES IN REINFORCED CONCRETE CONSTRUCTION
* FLOOR SLABS
* STAIRS
* ROOFS

* Allowable Vs Working Stress
* Working Stress is almost synonymous with allowable stress. * In equation form:
* Stress (working) <= Stress (allowable)‏

PLACING:
Before you place reinforcing steel in forms, all form oiling should be completed. Oil on reinforcing bars should be avoided because it reduces the bond between the bars and the concrete. Use a piece of burlap to remove rust, mill scale, grease, mud, or other foreign matter from the bars. A light film of rust or mill scale is not objectionable

TYING:
* Tie wire is used to hold rebar in place to ensure that when concrete is placed the bars do not shift out of position. * Sixteen gauge wire is used to tie reinforcing bars. About 12 pounds (5.4 kg) of wire is required to tie an average ton (0.9 ton) of bars.

has the advantage of causing little or no twist in the bars.
CROSS TIE or FIGURE-EIGHT TIE
used for heavy mats that are to be lifted by a crane.
SADDLE TIE WITH TWIST
used on special locations, such as on walls
SADDLE TIE.
especially favored for heavy...
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