Sect Sectio ion n3
Reinforced Concrete 3.1 3.1 Basics Basic s of Rein Reinfo forc rced ed Concr ete
2
PCA PCA Video, Video , VC11 VC114 4 ’88 Mod ‘07: Fund amentals ament als of Reinfor cing and Prestressed Prestressed Concrete
4
Structural Struct ural Enginee ngi neerin ring g Concepts
5
Reinf Reinforc orceme ement nt Inspection
12
CRSI CRSI Video, Mod ‘08: Field Inspectio Inspect ion n of Reinfor cing Bars Bars
13
WCI WCI Video: Jo bsit bs ite e Hand Handli ling ng of Epoxy Coated Coated Rebar
24
CRSI CRSI:: MSP MSP Chp. 8, Placin Placing g Rein Reinfo forc rcin ing g Bars
25
Bar Supports Suppor ts
28
Bar Ties
30
Clearances
32
Splices
40
Reinforced Concrete
Section 3.1
Reinforced Concrete Section 3.1
So what’s what’s wron g with usin g unreinforced concrete?
January, 2014
1
Reinforced Concrete
Section 3.1
Concrete Cracks
Basics of Reinforced Concrete • Concrete is strong in compression and weak in tension.
Compression
Tension
• Tensile capacity is approximately 10% of the compressive strength of concrete.
January, 2014
2
Reinforced Concrete
Section 3.1
Beam Exercise
Basics of Reinforced Concrete Cont’d: • Steel reinforcement is strong in tension. • Reinforcement is added to carry tensile loads in concrete members. • Temperature reinforcement is added to carry tensile loads due to thermal expansion of concrete members.
January, 2014
3
Reinforced Concrete
Section 3.1
Why Use Rebar? Simpl y su pport ed beam example Applied Load
View PCA Video Fundamentals Of Reinforcing And Prestressed Concrete (PCA VC114 ’88 Mod ‘07)
January, 2014
4
Reinforced Concrete
Section 3.1
Structural Engineering Concepts
Shear & Moment Diagram Uniformly Loaded Simple Beam
January, 2014
5
Reinforced Concrete
Section 3.1
Uniformly Loaded Simple Span • Shear is Maximum at End Bents • Shear is Zero at Midspan • Moment is Maximum at Midspan • Moment is Zero at End Bents
Maximum Shear Load at Bridge Ends and Piers Larger Stirrup Spacing @ Midspan
Tighter Stirrup Spacing Near Abutments
January, 2014
6
Reinforced Concrete
Section 3.1
Tighter Stirrup Spacing at Beam Ends
Shear & Moment Diagram Uniformly Loaded Continuous 3 Span
January, 2014
7
Reinforced Concrete
Section 3.1
Uniformly Loaded Continuous Beam 3 Spans • Shear is Zero near Midspans. • Shear is Maximum at Interior Bents. • Positive Moment is Maximum near Midspans. • Negative Moment is Maximum near Interior Bents. • Moment is Zero at End Bents.
Uniformly Loaded Continuous Beam 3 Spans Maximum negative moment over interior bents. Additional longitudinal reinforcement added in top mat.
January, 2014
8
Reinforced Concrete
Section 3.1
Beam Capacity
Strength of the Beam
Beam Cross-section
Beam Side View
M = Astf y(d-1/2a) = 0.85f c’ ab(d-1/2a)
January, 2014
9
Reinforced Concrete
Section 3.1
Case Study I-25: Walnut Street Denver, CO
January, 2014
10
Reinforced Concrete
Section 3.1
Thoughts?
Deck To Be Placed Later
Construction Joint
I-25: Walnut Street Pier Collapse
January, 2014
11
Reinforced Concrete
Section 3.1
Pier Collapse I-25: Walnut Street, Denver, CO Oct. 4, 1985 Fatalities: 1 Injuries: 4
Reinforcement Inspection
January, 2014
12
Reinforced Concrete
Section 3.1
View CRSI Video CRSI Field Insp Reinf Bars Mod 08
Type of Reinforcement • Source • Certifications • Grade • Epoxy Coated or Uncoated or Stainless
January, 2014
13
Reinforced Concrete
Section 3.1
Documentation
Bill s of material – what was delivered
Certifications
Rebar (steel) mill certificate
January, 2014
14
Reinforced Concrete
January, 2014
Section 3.1
15
Reinforced Concrete
Section 3.1
QPL Appendix A http ://www.or egon.gov /ODOT/HWY/CONSTRUCTION/QPL/Docs/QPL.pdf
January, 2014
16
1 A e g a P
s t i n ) U c 0 i r 1 4 t 0 f e 2 o y 1 M l u e – J s ( g a r L P e P , c u ” d Q A o – “ r t P T n O e r a D m b h n c e o a R g t t d e r A e v O o r p p A
e g a I & F C s a w 1 2 6 1 # D I T O D O
2 1 1 1 # D I T O D O
1 1 1 1 # D I T O D O
s t i n ) U c 0 i r 1 4 t 0 f e 2 o y 2 M l u e – J s ( g a r L P e P , c u ” d Q A o – “ r t P T n O e r a D m b h n c e o a R g t t d e r A e v O o r p p A
3 – A e g a P 2 4 8 1 # D I T O D O
1 4 8 1 # D I T O D O
s t i n ) U c 0 i r 1 4 t 0 f e 2 o y 3 M l u e – J s ( g a r L P e P , c u ” d Q A o – “ r t P T n O e r a D m b h n c e o a R g t t d e r A e v O o r p p A
2 2 6 1 # D I T O D O
3 2 6 1 # D I T O D O
4 A e g a P
a n o z i r A a s e M – l e e t S C M C
8 1 1 4 # D I T O D O
5 3 9 2 # D I T O D O
s t i n ) U c 0 i r 1 4 t 0 f e 2 o y 4 M l u e – J s ( g a r L P e P , c u ” d Q A o – “ r t P T n O e r a D m b h n c e o a R g t t d e r A e v O o r p p A
Reinforced Concrete
Section 3.1
Rebar Example Mill: Size: Dia: Type: Grade:
Rebar ebar Exercise xerci se Mill: Size: Dia: Type: Grade:
January, 2014
17
Reinforced Concrete
Section 3.1
Rebar Exercise Mill: Size: Dia: Type: Grade:
Rebar Exercise Mill: Size: Dia: Type: Grade:
January, 2014
18
Reinforced Concrete
Section 3.1
Size & Shape • Bar size • Bar length • Bar shape (correct radius) • Agrees with shop drawings
REBAR MATERIAL TAG A
B
A. Quantity B. Size
C
C. Bend diagram D. Project D
E
January, 2014
E. Bar ID or mark →
Verify
19
Reinforced Concrete
Section 3.1
Doubled Up Horizontal Bars in Abutment?
Hooked Bar in Middle of Deck by Itself?
January, 2014
20
Reinforced Concrete
Section 3.1
Rebar Condition
Condition • Look for any loose scale or rust, grease, oil, paint, or other foreign material that could harm the bond with the concrete. • Properly stored off the ground to avoid water and mud which can cause corrosion. • Do not use cracked or split bars (look at bends). • Look for epoxy damage.
January, 2014
21
Reinforced Concrete
Section 3.1
Field Bent Bars?
Epoxy Damage
January, 2014
22
Reinforced Concrete
Section 3.1
Rebar Jobsite Storage Total exposure time of epoxy-coated bar in storage or in place is not to exceed 2 months without covering. (530.40)
Epoxy breaks down under prolonged UV exposure – it gets Chalky
Faded Epoxy & Bare Ties?
January, 2014
23
Reinforced Concrete
Section 3.1
View WCI Video Jobsite Handling Epoxy Coated Rebar
January, 2014
24
Reinforced Concrete
Section 3.1
Layout • Number • Spacing • Alignment
Placement Tolerances according to “ Manual of Standard Practice” 530.41
January, 2014
25
Reinforced Concrete
Section 3.1
Effective Depth “ d”
Distance from the compression face of the beam to the centroid of the reinforcement
January, 2014
26
Reinforced Concrete
Section 3.1
Transverse Bar Alignment Shift?
Longitudinal Bar Alignment Shift?
January, 2014
27
Reinforced Concrete
Section 3.1
Bar Supports
Rail Stirrup Height Uneven?
January, 2014
28
Reinforced Concrete
Section 3.1
Transverse Deck Bars Drop at Corner?
Bar Supports 530.41(b) & (c) 2’ Centers (plans) Concrete blocks (Dobies) or other approved devices No rocks, broken brick, or wood
January, 2014
29
Reinforced Concrete
Section 3.1
Large Support Spacing Caused Epoxy Ties to Unzip
Ties
January, 2014
30
Reinforced Concrete
Section 3.1
Top mat of footings & decks: Tie 100%
Ties 530.41(b) Epoxy coated ties for epoxy rebar
If spacing < 6” Tie 50%
Other locations: Tie 100% If spacing < 1’ Tie 50%
No Ties for Up to 10 Feet?
January, 2014
31
Reinforced Concrete
Section 3.1
Missing Ties
Clearances
January, 2014
32
Reinforced Concrete
Section 3.1
Concrete Cover Affects Rebar Corrosion
Concrete cover
Clearances • Within tolerances recommended in CRSI’s Manual of Standard Practice, Chapter 8 unless otherwise specified. (00530.41) • As specified on the plans. • Tolerance on top mat of r einfor cement to t he top of deck sur face is (+/-) 1/4” . (00540.48(g))
January, 2014
33
Reinforced Concrete
Section 3.1
Hooked Bar Laying on Form?
Transverse Bar on Chamfer Strip?
January, 2014
34
Reinforced Concrete
Section 3.1
Transverse Deck Bar Under Drip Strip?
Transverse Bar Touching Fillet Form?
January, 2014
35
Reinforced Concrete
Section 3.1
¾” Clearance Under Deck Rebar Over Slabs?
Bott om Transverse Bars in Pilecap Touching Forms?
January, 2014
36
Reinforced Concrete
Section 3.1
Bar Touching Form in Crossbeam?
High Stirrup in Crossbeam?
January, 2014
37
Reinforced Concrete
Section 3.1
Watch Clearances on Rail Windows
½” Clearance on Vertical Rail Bars to Window Form
January, 2014
38
Reinforced Concrete
Section 3.1
How far are rail stir rups from the deck side form?
Clearance Exercise Calculate the dist ance from the rail stirr ups to th e deck side form.
___________________________ ___________________________ ___________________________ ___________________________
January, 2014
39
Reinforced Concrete
Section 3.1
Splices
No Splice?
January, 2014
40
Reinforced Concrete
Section 3.1
Splices • As permitted per plans • Splice bars No. 11 & smaller by Lapping or Approved Mechanical Splice. • Splice bars No. 14 and larger with an Approved Mechanical Splice Only. • Welded only with prior approval and with a certified welder.
Lap Splice 530.42(b) • Place bars in contact. • Fasten with 3 ties/Splice Minimum. • Length as shown (General Notes). • Epoxy coated reinforcement requires longer splice length.
January, 2014
41
Reinforced Concrete
Section 3.1
1 Tie on Splice?
January, 2014
42
Reinforced Concrete
Section 3.1
1 Tie on Splice?
Mechanical Splice 530.42(c) • Construct per Specifications and Manufacturers Recommendations. • Construct test splices in the presence of The Engineer. • Install splices in the presence of The Engineer. Splices made without The Engineer present will be rejected.
January, 2014
43
Reinforced Concrete
Section 3.1
Mechanical Splice Installers 530.30 • Provide qualified mechanical splice installers. • Construct test splices in the presence of The Engineer. • Construct 3 splice samples per type and size for each installer. • Do not begin splice installation until installers have been approved.
Spliced Bars Project Up?
January, 2014
44
Reinforced Concrete
Section 3.1
Spliced Vertical Column Bars
Reinforcement Inspection Inspection of the forms and reinforcement takes time. Check early & often to help assure they are doing things correctly and to avoid minimal rework. Do not wait until just before the concrete placement. Do a final check just prior to the concrete placement to assure everything still looks good.
January, 2014
45
Deck Rebar Checklist Project Information Project Name (Section)
Contract No.
Highway
Federal Aid No.
Contractor or Subcontractor
Deck Placement Date: Inspected Item
Yes
No
N/A
Date
Remarks
(mm/dd/yyyy)
1 Bottom Mat Bar Size & Spacing 2 Bottom Mat Ties @ 50% 3 Bottom Mat Clearance 4 Epoxy Ties (if epoxy bars) 5 Supports @ 2' Centers 6 Clearance @ Drip Strip 7 Lap Splices have three (3) ties 8 Top Mat Bar Size & Spacing Top Mat Ties @ 100% if spacing is greater than or equal to 6" Top Mat Ties @ 50% 9b if spacing is less than 6" Top Mat Bars directly over 10 Bottom Mat Bars Top & Bottom Mat Bars installed parallel 11 to skewed joint at both ends of deck 9a
12 Side & End Form Clearances 13 Rail Stirrup Size & Spacing 14 Additional Rail Stirrups @ Joints 15
Rail longitudinal bars cut at joint except bottom two
16 Rail 1-1/4" inside Edge of Deck 17 Rebar Support @ Corners 18 Dry Run Clearance Check Remarks
Inspected by 734-2837 (11-2010)
Date http://www.oregon.gov/ODOT/HWY/CONSTRUCTION/hwyConstForms1.shtml
1 of 1
