Transcript
REBAR WORKS 101
Construction ManpowerDevelopment Foundation
Be familiar with pertinent code provisions/requirements
Identify grade, size and type of steel used
Prepare rebar placing/working drawings and bar bending and cutting schedule
Objectives
Material Specification PNS 49 : 1991 - Specs. For Steel Bars for
Concrete Reinforcement ASTM A 615 – Specs. For Deformed and Plain
Billet Steel Bars for Concrete Reinforcement ASTM A 616 – Specs. For Rail Steel Deformed
and Plain Bars for Concrete Reinforcement ASTM A 617 – Specs. For Axle Steel Deformed
and Plain Bars for Concrete Reinforcement ASTM A 706 – Specs. For Low Alloy Steel
Deformed Bars for Concrete Reinforcement
REINFORCING BARS SHALL BE:
• ACCURATELY PLACED
• ADEQUATELY SUPPORTED AND
• SHALL BE SECURED AGAINST DISPLACEMENT
Fundamentals
Tolerance on effective depth
(d)
Tolerance on minimum
concrete cover
d 200 mm
d > 200 mm
± 10 mm
± 12 mm
- 10 mm
- 12 mm
Placing Tolerances
Fundamentals
Cutting Reinforcing bars shall be cut cold
Bending Reinforcing bars shall be bent cold Don’t re-bend, heat or re-straighten
reinforcing bars
900 BEND 1800 BEND
E = larger of4db or 65mm
E
db = nominal diameter of main bar
Standard Hooks for Main Bars
900 BEND 1350 BEND
6db (db16mm)12db (db=20 or 25mm)
6db (db 25mm)or 75mm
E
E
Standard Hooks for Ties and Stirrups
Minimum Bend DiameterNominal Diameter
Minimum Bend Diameter
Main Bars Ties/Stirrups
6 db
4 db10
12
16
206 db
25
288 db
-32, 36
42, 58 10 db
Types of Structure Minimum Concrete Cover (mm)
Concrete cast against and permanently exposed to earth
Concrete exposed to earth or weather: 20mm through 36mm bars 16mm and smaller bars
Concrete not exposed to earth or weather or not in contact with ground: Slabs, walls, joists 32mm and smaller Beams, columns. Primary reinforcement ties, stirrups, spirals
75
5040
20
40
Concrete Cover
Sc = db, but notless than 25mm
db = bar diameter
Parallel Bars Parallel Bars in two or more layers
Sc = 25mm
Spacing Limits of RSB
Sc
Spirally reinforced or tied reinforced compression members
Sc = 1.5db but not less than 40mm
Contact Lap Splices
Sc = db, but not less than 25mm
Spacing Limits of RSB
Walls and Slabs
Sc < 3t but not greater than 450mmSc = 25 mm minimum
t = wall or slab thickness
Spacing Limits of RSB
Identifying the type, size and grade of steel used
Anong size kayaito ?
A
W
A
275
32
W
Manufacturer’sMarking
Grade
Bar Size
Weldable
PNS 49: 2002
PNS Grade Marking
Dash Metric Englishno dash
1 dash2 dash
Grade 230
Grade 415Grade 275
33 ksi
60 ksi40 ksi
275
PNS 49: 2002
lugs
Ribs
PNS 49: 2002
Quality Test Rebar (PNS 49) Classification
Regular steel bars; and Weldable
Chemical Composition Mechanical Properties
Yield strength Tensile Strength % Elongation Bend Test
Dimension and Mass Tolerance Deformation Requirements
Height of Lugs Spacing Gap distance
PNS 49: 2002Nominal Dimensions and Unit Mass Standards
Diameter, mm Perimeter, mmCross
Sectional Area, mm2
Mass, Kg/m
10 31.4 78.54 0.617
12 37.7 113.10 0.888
16 50.3 201.06 1.578
20 62.8 314.16 2.466
25 78.5 490.88 3.853
28 88.0 615.75 4.834
32 100.5 804.25 6.313
36 113.1 1017.88 7.990
40 125.7 1256.64 9.865
50 157.1 1963.50 15.413
Tolerance, height of lugs
Nominal diameter, mmMinimum height of lugs *
10 4.0
12 and 16 4.5
20 and above 5.0
*Percent of nominal diameter
Deformation Requirements
Diameter, mm
Max. average spacing of lugs, mm
Height of tolerance of lugs, mm
Max. Value summation of gaps of Lugs,
mmMin. Max.10 7.0 0.4 0.8 7.8
12 8.4 0.5 1.0 9.4
16 11.2 0.7 1.4 12.6
20 14.0 1.0 2.0 15.7
25 17.5 1.2 2.4 19.6
28 19.6 1.4 2.8 22.0
32 22.4 1.6 3.2 25.1
36 25.2 1.8 3.6 28.3
40 28.0 2.0 4.0 31.4
50 35.0 2.5 5.0 39.3
PNS 49: 2002
White - Grade 230
Yellow - Grade 275
Green - Grade 415
PNS 49: 2002
Red – Weldable Bars
Prepare Placing/working drawing
Bar cut off/bend point Splice location & length Number of bars Placing dimension Cut length Bar position/location X-dimension & clear distance
GIRDER PLACING DRAWING
Joint
COLUMN PLACING DRAWING
Perimeter beams, shall have continuous reinforcement over the span length passing thru the region bounded by the longitudinal reinforcement of the column consisting of
1. At least 1/6 of the required tension reinforcement for neg. moment but not less than 2 bars
2. At least 1/4 of the required tension reinforcement for positive moment but not less than 2 bars
And tied with closed stirrups. Closed stirrups need not be extended through any joints. Continuity with top bars spliced at midspan & bottom bars spliced at or near the support with Class B tension splices
(NSCP 2010)407.14 Requirements for Structural Integrity, Perimeter Beams
(NSCP 2010)407.14 Requirements for Structural Integrity, Interior beams
In other than perimeter beams, when closed stirrups are provided there are no additional requirement for longitudinal integrity reinforcement. Where such transverse reinforcement is not provided, at least 1/4 of the positive moment reinforcement required at midspan, but not less than 2 bars shall be continuous or shall be spliced near or over the support with a “class B” tension splice and at non- continuous supports be terminated with a standard hook
Contact Lap Splice
Splicing of Reinforcing Bars
Welded Splice
Coupled Splice
Splicing of Reinforcing Bars
GAS PRESSURE WELDING (GPW)
Splicing of Reinforcing Bars
(NSCP 2010) 412.11 Development of Flexural Reinforcement - General
.3 Reinforcement shall extend beyond the point at which it is no longer required to resist flexure for a distance equal to the effective depth of the member or 12db, whichever is greater or, except at supports of simple spans and at free end of cantilevers
Dd
412.11 Development of Flexural Reinforcement - General
L/4 d or 12db
d or 12db
TOP BAR
BOTTOM BAR
Dd
d or12db
412.11 Development of Flexural Reinforcement - General
L/3d or12 db
d or12 db
L/3
d or12db
(NSCP 2010) 412.11 Development of Flexural Reinforcement - General
.4. Continuing reinforcement shall have an embedment length not less than the development length ld beyond the point where bent or terminated tension reinforcement is no longer required to resist flexure.
412.12 Development of Positive Moment Reinforcement
.1. At least 1/3 of the positive moment reinforcement in simple members and 1/4 the positive moment reinforcement in continuous members shall extend along the same face of member into the support. In beams, such reinforcement shall extend into the support at least 150 mm
Dd
412.12 Development of Positive Moment Reinforcement
L/4
d or 12dbBOTTOM BAR
150 mm min.
1/4 x BOTTOM BAR
412.13 Development of Negative Moment Reinforcement
.1. Negative moment reinforcement in a continuous, restrained, or cantilever member or in any member of a rigid frame, shall be anchored in or through the supporting member by embedment length, hooks, or mechanical anchorage.
412.13 Development of Negative Moment Reinforcement
.3. At least 1/3 of the total tension reinforcement provided for negative moment at the support shall have an embedment length beyond the point of inflection not less than effective depth of member, 12db, or 1/16 of the clear span, whichever is greater.
Dd
412.13 Development of Negative Moment Reinforcement
L/4 d or 12db TOP BAR1/3 x TOP BAR
d or 12db or L/16
412.16, NSCP 2010, Splices of Deformed Bars & Wires in Tension
.2 Lap splices of deformed bars and deformed wires in tension shall be Class B except that Class A splices are allowed when:
a. The area of reinforcement provided is at least twice that required by analysis over the entire length of splice, and
b. 1/2 or less of the total reinforcement is spliced within the required length
CLASS A LAP SPLICE = 1.0 ld
CLASS B LAP SPLICE = 1.3 ld
412.16, NSCP 2010, Splices of Deformed Bars & Wires in Tension
Basic Development Length Formula - Tension
= db (fy Ψl Ψc )
For 20 mm dia and smaller
= db (fy Ψl Ψc )
For 25 mm dia and larger
2.1 λ √fc’
1.7 λ √fc’
Note:
Sc and cc ≥ db, stirrups and ties through out ld not less than the code min.
Or
Sc ≥ 2db and cc ≥ db
Basic Development Length Formula - Tension
= db (fy Ψl Ψc )
For 20 mm dia and smaller
= db (fy Ψl Ψc )
For 25 mm dia and larger
1.4 λ √fc’
1.1 λ √fc’
Note:
for other cases
LAP SPLICE = 0.071fydb
412.17, NSCP 2010, Splices of Deformed Bars in Compression
412.18.2, Lap Splices in Columns
.2 Where bar stress due to factored load is tensile and does not exceed 0.5Fy in tension, lap splices shall be Class B tension lap splices if more than 1/2 of the bars are spliced at any section, or Class A tension lap splices if half or fewer bars are spliced at any section and alternate lap splices are staggered by ld.
Prepare Bar Bending & Cutting Schedule
Structure Location/position of RSB Shape and dimension Bar size Cut length No. of pieces
Position/LocationStructure
Co
lum
nG
ird
er
Be
am
Main Bar
End Bar
Top Bar
Bottom Bar
Extra Top Bar
Extra Bottom Bar
Stiffener
StirrupsSpreader
Top Bar
Bottom Bar
Extra Bottom Bar
Stirrups
Shape/Dimension Bar Ø Cut Length PcsStructure Location/Position
Change in Length from Detailing Dimension to Cutting Length
Bar Φ, mm
Main Bars
Bend Correction Hook Correction
45° 90° 180° 90° 180°
8
- 0.5 db - 2.5 db + 3 db + 13.5 db
+7db + 6510
12
16
+ 11 db20
25
28
- 0.6 db - 2.9 db + 4.1 db + 14.1 db + 13.1 db32
36
Change in Length from Detailing Dimension to Cutting Length
Bar Φ, mm
Ties/Stirrups
Bend Correction
Hook Correction
90° 90° 135°
8
- 2 db
+ db + 60 + 3 db + 60
10
+ 7 db + 9 db12
16
20- 2.5 db + 13.5 db + 10.2 db
25
Structure Position/Location Shape/Dimension Bar Diameter Cut Length No. of Pieces
Cutting List (Sample Form)
Snap or Single Tie- a simple tie
wrapped once around the two crossing bar in diagonal manner.
Wrap and Snap Tie- used in tying
wall reinforcement.
Saddle or U tie- for footing bars or other mats.- for securing col. ties to vertical bars.
Wrap and Saddle Tie- used to secure heavy mats that are lifted by crane.
Figure Eight Tie- can be used instead of Wrap Snap tie.
Methods of Tying Bars
Bar Supports
Metal Concrete Plastic
Bar Supports