Visual Inspection and Condition Assessment

Report
(Bridge #1618-150 in Wayne, NJ)
Jungseok Lee*, Namhee Jin, Jongchul Kim & Soobong Shin
PEC, KCQRC & Inha Univ.
Republic of Korea
Contents
I.
II.
III.
IV.
V.
Introduction of Bridge Inspection System of Korea
Summary of Visual Inspection Results
Summary of NDT Results
Result of Condition Evaluation
Intervention for Repair
2
I. Introduction
1.
Special Law for the Safety Maintenance of Infrastructures
•
•
•
•
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.
Classification of Inspection
1)
Initial Inspection
•
2)
After construction, widening, strengthening, etc.
Routine Inspection
•
•
3)
Every 6 months
Brief inspection for important and/or damaged members
Precision Inspection
•
•
•
4)
Every 2 years
Detail inspection for all members & NDT
Condition evaluation
In-depth Inspection
•
•
5)
Every 5 years
Precision inspection & structural safety assessment
Damage Inspection
•
Unscheduled inspection for the environmental attack or car accident
4
I. Introduction
3.
Procedure of Condition Evaluation of a Bridge
•
3-stage condition evaluation
[element-level] → [span-level] → [bridge-level]
Element-level CE
Element-level CE
Avg.
span-level
CE for
girder
span-level
CE for
Pavement
support-level
CE for
Pier
•
Element-level CE
defect investigation
Weighting on members
Minimum level
Bridge-level CE
5
•
I. Introduction
4.
Condition Rating at Element Level
1)
Classification and Grades for Elements
Classification of Elements
Superstructure
Substructure
Bearing
Miscellaneous
Concrete
material
Grades
Slabs, Girders, Cables
a, b, c, d, e
Cross beams, Stringers
a, b, c, d
Abutments, Piers, Pylons, Footings, Piles
a, b, c, d, e
Bearings
a, b, c, d, e
Expansion Joints, Railings, Curbs, Pavement,
Drainage
a, b, c, d
Carbonation, Chloride content
a, b, c, d
• Primary structural members : a – e
• Secondary or non-structural members : a – d
6
I. Introduction
2)
Categories of CE at Element Level
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
m.
n.
o.
p.
q.
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
•
•
•
•
Deterioration & Damage
Two-way
a
cw < 0.1mm
cw < 0.1mm
None
b
0.1 ≤ cw < 0.3mm
cr ≤ 2%
0.1 ≤ cw < 0.3mm
Ac < 2%
c
0.3 ≤ cw < 0.5mm
2% ≤ cr ≤ 10%
cw ≥ 0.3mm
2% ≤ Ac < 10%
Acs < 2%
Minor delamination and leakage of deck plate
d
0.5 ≤ cw < 1.0mm
10% ≤ cr ≤ 20%
Delamination
occurred
Ac ≥ 10%
Acs ≥ 2%
Severe delamination and corrosion of deck plate
e
cw ≥ 1.0mm
cr ≥ 20%
Possible
punching shear
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.)
Defect or damage
Criterion
Crack
Distortion or Fracture
Omission or
loose of bolts
Defect on welding
Surface
Deterioration
a
None
None
None
None
b
Minor crack on
secondary
members
Minor distortion on
secondary members
Nbs < 2%
Minor welding defects
Asp < 10%
on secondary members
(slag, pothole, undercut) Asc < 2%
c
Severe crack on
secondary
members
Minor crack on
main members
Severe distortion or fracture
on secondary members
Minor distortion on
main members
Corrosion of bolts connecting
pylon and basement
d
Severe crack on
main members
Severe distortion or fracture
on main members
Buckling distortion on
main members
Fracture of bolts connecting
pylon and basement
e
Severe crack
causing fracture
on main members
Decrease of safety of main
members caused by severe
buckling or fracture
•
•
•
•
•
2% ≤ Nbs < 10%
Nbm < 2%
Nbs ≥ 10%
2% ≤ Nbm < 10%
Nbm ≥ 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
None
Severe welding defects
on main members
(slag, pothole, undercut) Asp ≥ 10%
Minor welding defects
2% ≤ Asc < 10%
(omission and/or
incomplete penetration)
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%
9
I. Introduction
5)
Criterion for Concrete Piers
Criterion
•
•
•
Crack or dislocation
Deterioration & Damage
a
cw < 0.1mm
None
b
0.1 ≤ cw < 0.3mm
Ac < 2%
c
0.3 ≤ cw < 0.5mm
2% ≤ Ac < 10%
Acs < 2%
d
0.5 ≤ cw < 1.0mm
Pier inclination by differential settlement
Ac ≥ 10%
Acs ≥ 2%
e
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.
Condition Rating at Bridge Level
•
•
A to E
Results from visual inspection and NDT
Grade
Description
A
Excellent condition.
B
Minor problems in secondary members.
Needs repair works to increase durability.
C
Minor problems in primary members
and/or extensive problems in secondary members.
Needs repair works to increase performance.
D
Extensive problems in primary members.
Needs reinforcement works to ensure structural safety.
Road closure considered
E
Critical or failure condition. Close the bridge.
Needs reinforcement or rebuilding
US
Austria
9, 8
1
7, 6, 5
2
4, 3
3
2
4, 5
1, 0
6
11
I. Introduction
5.
Condition Rating at Bridge Level
1)
Weighting Factors
12
I. Introduction
5.
Condition Rating at Bridge Level
2)
Result of Condition Evaluation
 Damage Index (DI)
Grade
A
B
C
D
E
DI range
0 ≤ DI < 0.13
0.13 ≤ DI < 0.26
0.26 ≤ DI < 0.49
0.49 ≤ DI < 0.79
0.79 ≤ DI
13
II. Summary of Visual Inspection
1.
Concrete Slabs
- 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.
Steel Plate Girders
- Inner girders : good condition (no corrosion)
(Inner girders)
(End of inner girder)
15
II. Summary of Visual Inspection
2.
Steel Plate Girders
- 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.
Steel Plate Girders
- 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)
17
(Crack without stopholes)
II. Summary of Visual Inspection
3.
Concrete Piers
- 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.
Abutment (A1)
- 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.
Abutment (A2)
- 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.
Bearings
- Under inner girders : good condition
- Under outer girders : poor condition (corrosion and sectional loss)
(Inner bearing)
(Outer bearing)
21
III. Summary of NDT
1.
Concrete NDT
1)
Compressive Strength
•
(Abutment)
Rebound test using Schmidt Hammer
(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.
Steel NDT
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
(Special Consideration on Cracks & Spalls in Pier Cap)
Nondimentional Reaction Force
 Vehicle Loading
- AASHTO LRFD Code (HS 20-44 +10% load scale)
- Multiple presence factor for 4 lanes (1.2 / 1 / 0.85 / 0.65)
 Reactions to Vehicle Loading
Maximum Vertical Reaction of Bearing
1.00
1.00
- Maximum Vertical Reaction
0.82
0.80
0.60
0.40
0.39
0.40
3
4
0.53
0.55
7
8
0.43
0.35
0.20
0.00
1
2
5
6
Bearing Number
Non-dimensional Reaction Force
Fi  Fi / Fm ax
(Special Consideration on Cracks & Spalls in Pier Cap)
 Possible Reasons for Cracks & Spalls
- Largest reaction force
- Missing of vertical & lateral wrapping reinf.
- Concrete cover thickness < 2”
missing
V. Intervention for Repair
1.
Outer Girders
•
2.
Removing Rust and painting is needed to prevent further
corrosion and sectional loss
Bearings under outer girders
•
3.
Severely corroded bearings should be changed for proper
movement by thermal expansion
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

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