(Bridge #1618-150 in Wayne, NJ)

Contents
I.
II.
III.
IV.
V.
2

I. Introduction
1.
• Established in 1995 just after the tragic collapse of Sungsu
Bridge in Korea
• Regulation for maintenance of important infrastructures
• KISTEC(Korea Infrastructure Safety & Technology
Corporation) was established by Government according to this law which is responsible for the safety maintenance of important infrastructures
• All guidelines and manuals for inspection and condition evaluation have been made by KISTEC under the supervision of Korean Government
3

I. Introduction
2.
1) Initial Inspection
• After construction, widening, strengthening, etc.
2) Routine Inspection
• Every 6 months
• Brief inspection for important and/or damaged members
3) Precision Inspection
• Every 2 years
• Detail inspection for all members & NDT
• Condition evaluation
4) In-depth Inspection
• Every 5 years
• Precision inspection & structural safety assessment
5) Damage Inspection
• Unscheduled inspection for the environmental attack or car accident
4

I. Introduction
3.
• 3-stage condition evaluation
[element-level] → [span-level] → [bridge-level] defect investigation
Minimum level
Element-level CE
Element-level CE
Element-level CE
Avg.
span-level
CE for girder span-level
CE for
Pavement support-level
CE for
Pier
• •
Weighting on members
Bridge-level CE
5

I. Introduction
4.
1) Classification and Grades for Elements
Concrete material
Classification of Elements
Slabs, Girders, Cables
Superstructure
Cross beams, Stringers
Substructure Abutments, Piers, Pylons, Footings, Piles
Bearing Bearings
Miscellaneous
Expansion Joints, Railings, Curbs, Pavement,
Drainage
Carbonation, Chloride content
• Primary structural members : a – e
• Secondary or non-structural members : a – d
Grades a, b, c, d, e a, b, c, d a, b, c, d, e a, b, c, d, e a, b, c, d a, b, c, d
6

I. Introduction
2) Categories of CE at Element Level l.
m.
n.
o.
h.
i.
j.
k.
p.
q.
e.
f.
g.
a.
b.
c.
d.
Concrete Slabs
Steel members(slabs, girders, piers, pylons)
Reinforced concrete girders
Pre-stressed concrete girders
Concrete cross beams
Steel cross beams and stringers
Cables
Abutments
Concrete piers
Footing, piles, caissons
Bearings
Expansion joints
Pavement
Drainage
Railings and curbs
Carbonation
Chloride content
* Total 17 categories (15 member groups and 2 concrete material tests)
7

I. Introduction
3) Criterion for Concrete Slabs
Crack
Criterion
One-way Two-way a cw < 0.1mm
None b c cw < 0.1mm
0.1
≤ cw < 0.3mm
cr
≤
2%
0.3
≤ cw < 0.5mm
2%
≤ cr
≤
10%
0.1
≤ cw < 0.3mm
cw
≥
0.3mm
Ac < 2% d e
0.5
≤ cw < 1.0mm
10%
≤ cr
≤
20% cw
≥
1.0mm
cr
≥
20%
Delamination occurred
Possible punching shear
Deterioration & Damage
2%
≤
Ac < 10%
Acs < 2%
Minor delamination and leakage of deck plate
Ac
≥
10%
Acs
≥
2%
Severe delamination and corrosion of deck plate
Structural safety of slab is reduced caused by corrosion of reinforcements
• cw : crack width
• cr : crack ratio = crack area / surface area (crack area = length x 0.25m)
• Ac : damaged concrete area
• Acs : damaged concrete area with reduction of sectional area of reinforcement by corrosion
8

I. Introduction
4) Criterion for Steel Members(Slabs, Girders, Piers, etc.)
Criterion a
Crack
None
Defect or damage
Distortion or Fracture
Omission or loose of bolts
None
Defect on welding
Surface
Deterioration b c d e
None
Minor crack on secondary members
Severe crack on secondary members
Minor crack on main members
Severe crack on main members
Severe crack causing fracture on main members
Minor distortion on secondary members
Severe distortion or fracture on secondary members
Minor distortion on main members
Corrosion of bolts connecting pylon and basement
Severe distortion or fracture on main members
Buckling distortion on main members
Fracture of bolts connecting pylon and basement
Decrease of safety of main members caused by severe buckling or fracture
Nbs < 2
%
2
% ≤
Nbs < 10%
Nbm < 2
%
Nbs
≥
10%
2
% ≤
Nbm < 10%
Nbm
≥
10%
None
Minor welding defects on secondary members
(slag, pothole, undercut)
Severe welding defects on main members
(slag, pothole, undercut)
Minor welding defects
(omission and/or incomplete penetration)
None
Asp < 10
%
Asc < 2
%
Asp
≥
10
%
2%
≤
Asc < 10%
Decrease of safety of tension members caused by omission and/or IP
Crack development on welding line of tension members
Asc
≥
10
%
Asl < 10%
Asl
≥
10
%
• Nbs: # of damaged bolts on secondary members
• Nbm: # of damaged bolts on main members
• Asp: Damaged painting area of steel members
• Asc: Corroded area of steel members
• Asl: Corroded area with sectional loss of steel members
9

I. Introduction
5) Criterion for Concrete Piers
Criterion Crack or dislocation Deterioration & Damage a b cw < 0.1mm
0.1
≤ cw < 0.3mm
None c 0.3
≤ cw < 0.5mm
Ac < 2%
2%
≤
Ac < 10%
Acs < 2% d e
0.5
≤ cw < 1.0mm
Pier inclination by differential settlement
Ac
Acs
≥
10%
≥
2% cw
≥
1.0mm
Decrease of safety by differential settlement
Possible girder drop by breakage of coping
Decrease of safety by severe corrosion of reinforcement
• cw : crack width
• Ac : damaged concrete area
• Acs : damaged concrete area with reduction of sectional area of reinforcement by corrosion
10

I. Introduction
5.
• A to E
• Results from visual inspection and NDT
Grade
A
B
C
D
E
Description
Excellent condition.
Minor problems in secondary members.
Needs repair works to increase durability.
Minor problems in primary members and/or extensive problems in secondary members.
Needs repair works to increase performance.
Extensive problems in primary members.
Needs reinforcement works to ensure structural safety.
Road closure considered
Critical or failure condition. Close the bridge.
Needs reinforcement or rebuilding
US
9, 8
7, 6, 5
4, 3
2
1, 0
Austria
1
2
3
4, 5
6
11

I. Introduction
5.
1) Weighting Factors
12

I. Introduction
5.
2) Result of Condition Evaluation
 Damage Index (DI)
Grade
DI range
A
0 ≤ DI < 0.13
B
0.13 ≤ DI < 0.26
C
0.26 ≤ DI < 0.49
D
0.49 ≤ DI < 0.79
E
0.79 ≤ DI
13

II. Summary of Visual
Inspection
1.
Deck plates : good condition (no delamination, no leakage)
Concrete slabs : good condition with small lateral cracks
(Deck plates) (Cracks in cantilever of slabs)
14

II. Summary of Visual
Inspection
2.
Inner girders : good condition (no corrosion)
(Inner girders) (End of inner girder)
15

II. Summary of Visual
Inspection
2.
Outer girders : poor condition (severe corrosion with sectional loss on lower flanges)
(Outer girders) (End of outer girder)
16

II. Summary of Visual
Inspection
2.
Fatigue cracks on webs were reported in DOT reports
but couldn’t indentify by visual inspection
induced by vibration of lateral bracing due to differential deflection of girders
(Crack with stopholes)
(Location of web cracks, drawing by UT)

II. Summary of Visual
Inspection
3.
Good condition
Shear cracks and spalling were developed on the vertical surface of
P1 southbound caused by omitting vertical reinforcements in the pier cap on the top of column
Bending cracks were developed underside of pier cap of P2
(Shear crack of pier cap) (Bending crack of pier cap)
18

II. Summary of Visual
Inspection
4.
Poor condition
Severe vertical cracks and fault were developed
Severe shear cracks were developed both side surface
(Crack and fault of A1)
19

II. Summary of Visual
Inspection
4.
Poor condition
Severe vertical cracks on the parapet and severe shear cracks were developed both side surface
(Crack and fault of A2)
20

II. Summary of Visual
Inspection
5.
Under inner girders : good condition
Under outer girders : poor condition (corrosion and sectional loss)
(Inner bearing) (Outer bearing)
21

III. Summary of NDT
1.
1) Compressive Strength
• Rebound test using Schmidt Hammer
(Abutment) (Column) (Pier Cap)
22

III. Summary of NDT
1) Compressive Strength
• Design Strength : 21 Mpa
• Compressive strength of piers and abutments is estimated to exceed the design strength
23

III. Summary of NDT
2) Arrangement of Re-bars
• Using handy GPR(Ground Penetrating Radar)
• Measuring rebar spacing and concrete cover depth
(Abutmrnt) (Pier Cap)
24

III. Summary of NDT
2) Arrangement of Re-bars
• Compared with design values
• Good matching except slight difference in horizontal re-bars of abutment
25

III. Summary of NDT
2.
1) Sectional Loss of Steel Members
• Thickness measurement using ultrasonic equipment
• Sectional loss of outer steel girders by corrosion
(Thickness measurement of lower flange of steel girders)
26

III. Summary of NDT
2) Sectional Loss of Steel Members
• Lower flange of outer girder southbound
• Original thickness : 25.4 mm
• Measured thickness : 25.0 mm
• Sectional loss rate : 1.6%
27

IV. Result of Condition
Evaluation
28


AASHTO LRFD Code (HS 20-44 +10% load scale)
Multiple presence factor for 4 lanes (1.2 / 1 / 0.85 / 0.65)

Maximum Vertical Reaction
1,00
Maximum Vertical Reaction of Bearing
1,00
0,82
0,80
0,60 0,53
0,55
0,39 0,40
0,35
0,43
0,40
0,20
0,00
1 2 3 4 5
Bearing Number
6 7 8
Non-dimensional Reaction Force F i
 i
/ max


-
-
Largest reaction force
Missing of vertical & lateral wrapping reinf.
Concrete cover thickness < 2” missing

V. Intervention for Repair
1.
Outer Girders
• Removing Rust and painting is needed to prevent further corrosion and sectional loss
2.
Bearings under outer girders
• Severely corroded bearings should be changed for proper movement by thermal expansion
3.
Abutments
• Severe cracks and inclination due to structural deficiency
• Hard to decide the safety of Abutments at this time
• Need to monitor the behavior of abutments using crack meters and inclinometers
31