recent nysdot bridge failure ivestigations_ub presentation
TRANSCRIPT
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 1/83
Bridge Failures - Lessons learned
Recent NYSDOT Bridge Failure Investigations
George A. Christian, P.E.Director, Office of Structures
New York State Dept. of Transportation
Bridge Engineering Course
University at Buffalo
March 29, 2010
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 2/83
2
I-787 - Dunn Memorial Bridge Interchange
Albany, NY
partial collapse at pier 11- August 2005
I-787 Ramp NB toSouth Mall
Expressway WB
(BIN 109299A)
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 3/83
3
BIN 109299A
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 4/83
4
Structure Layout (looking east)
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 5/83
5
Overview of Failure
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 6/83
6
High Rocker Bearings
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 7/83
7
History of Misalignment of High
Rocker Bearings at Pier 11
1987Inspection
Temp. @ 45 °
1999Inspection
Temp. @ 70 °
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 8/83
8
2003 Inspection – Span 12 East Bearing
Temp @ 45 F
Lifted 0.25 ft.(3 in.) - Eccentricity = 3.4 in.
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 9/83
9
How did the bearings get misaligned?
Superstructure Displacements:• Survey of adjacent piers (w/ fixed bearings)
– Pier 10 displaced north 1.6 inches.
– Pier 12 displaced north 1.0 in (avg.) 1.7 inches oneast side.
• History of Pier 13 joint
– Joints ‘reset’ (vertical) in 1990
– Joint was closed in 1990
– Closed in 1995 thru present
• Longitudinal forces due to braking, centrifugal force
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 10/83
10
Condition of Rocker Bearings
• Susceptible to corrosion, debris when continuallytilted
• Corrosion, debris prevents rocking back towardvertical
– Under rocker – Pin corrosion
• Contact surfaces flatten or “dish”
• Result: Bearings become resistant to horizontal
movement, especially back toward being plumb .
Transfers longitudinal forces to substructure
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 11/83
11
Corrosion &
Flattening
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 12/83
12
Frozen Pins
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 13/83
13
Rocker and Pintle Corrosion – Span 11
Bearing
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 14/83
14
Pier 11
• Height: 82.3 feet
• 13.9’ x 6.44’ at
base
• 9’ x 4’ at top of
stem
• Stem rebar: 46 -
# 8 bars
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 15/83
15
Pier 11: Lack of Elastic Range
• Cracks 40 ft. upnorth face
• Rebounded51/2 in. when‘released’
• The pier failed
in flexure
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 16/83
16
Comparison of Adjacent Piers
PIER
NO.
HGT. BASE REINFORCING STEEL
No.-Size Bars Area
BEARINGS
FIX OR EXP
9 67.47’ 131.4” x 71.2” 42 - # 8 33.18 Fix - Exp
10 72.79’ 132.6” x 72.6” 36 - #11 56.16 Fix
11 82.31’ 166.6” x 77.3” 46 - # 8 36.34 Exp - Exp
12 83.38’ 155.3” x 77.6” 42 – #11 65.52 Fix
13 84.75’ 156.4” x 84.2” 42 - #11 65.52 Exp - Exp
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 17/83
17
Pier 11 Design Check
• Designed per 1965 AASHO code
• Meets strength req. for code assumptions
– Allowable / Actual ratio = 0.98 =1.0 (OK)
• No provision for large flexural displacements
• Equivalent Column with 1% reinforcing.
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 18/83
18
Results of Pier Analysis
• Limited elastic range - yields at 5.5” deflection
• Cracking at 2.5” deflection
• No capacity increase beyond cracking
Old Pier 11 (AC-12)
0
20
40
60
80
100
120
140
160
0 5 10 15 20
Longitudinal Pier Cap Displacement [in.]
L o n g i t u d i n a l P
i e r C a p
F o r c e [ k i p s ]
f’c=9
210psi
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 19/83
19
Forces Needed for Failure
• Thermal: limited by resistance of bearing
– Up to 0.58 x Dead Load if sliding assumed: approx.
200 kip from Span 12 only
– Limited range of movement
• Corrosion Build-up:
– Develops horizontal component of vertical dead, live
load reactions
– Larger range of movement
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 20/83
20
Probable Failure Sequence
• Bearings tilted to north > 20 years ago
• Bearings begin to resist horizontal mov’t.
• Superstructure longitudinal displacements began tomove pier instead of Span 12 bearings
• Bearings resist movement moving back toward vertical – Increased southward tipping of Span 12 and 11 bearings
• Instability point reached – bearings tipped
• Forces (displacements) sustained to deflect pier 16 +
in. (bearings tipping and spans falling on tippedbearings)
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 21/83
21
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 22/83
22
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 23/83
23
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 24/83
24
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 25/83
25
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 26/83
26
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 27/83
27
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 28/83
28
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 29/83
29
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 30/83
30
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 31/83
31
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 32/83
32
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 33/83
33
Underlying Cause of Failure
1. Rocker bearings becoming misaligned
2. Rocker bearing not functioning properly
3. Pier 11 was flexible in direction longitudinal
to the bridge
4. Pier 11 stem was “lightly” reinforced, and
not elastically ductile
• 1, 2 and 3 were required for failure to occur.
4 may have been required, but contributed
to extent of failure
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 34/83
34
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 35/83
35
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 36/83
36
Follow up actions
• Reviewed all high rocker bearings with low
inspection ratings (CR 3 or less)
• Inspected those overextended
• Preventive interim retrofits – bolsters
• Technical Advisory: INSP 05-001
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 37/83
37
Follow up actions
• Bolsters installed as an extraordinary
precautionary measures on 10 bridges
• Alerted other owners of bridges not under
DOT’s inspection jurisdiction
• Corrective action:
– Dunn Complex, bearing replacements
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 38/83
Marcy Pedestrian Bridge CollapseOctober 2002
South Abutment
North Abutment
Bracket
Field Splice
Span = 171 ft.
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 39/83
Acknowledgements
• Sponsored by New York State DOT
• P.I.—Weidlinger Associates, Inc.
• Material testing and weld inspections by
ATLSS Research Engineering Center, Lehigh
University
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 40/83
Outline
1. Collapsed Bridge
2. Review of Bridge Design
3. Analysis of Bridge Failure
4. Demolition
5. Laboratory Testing
6. Conclusions
7. Recommendations
8. NYSDOT Actions
9. Applications—Tub girders and beyond
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 41/83
Tub Girder Cross Section
Intermediate
Diaphragm
14.0 ft (4.27 m)
6 . 3
f t ( 1 . 9
3 m
)
4.3 ft (1.3 m)
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 42/83
Collapsed Bridge
North Abutment
South Abutment
Screed
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 43/83
Collapsed Bridge
South Abutment
Exp. Bearing
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 44/83
Collapsed Bridge
North AbutmentFixed Bearing
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 45/83
2. Review of Bridge Design
Objective: Evaluate the adequacy of the
bridge design
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 46/83
2.1 Design Codes
• NYS Standard Specifications for Highway Bridges with
provisions in effect as of April 2000.
• AASHTO Standard Specifications for Highway Bridges, 16th
Ed. LFD (1996) with 1997, 1998 & 1999 interim
• · AASHTO Subsection 10.51 Composite Box Girders (LFD) ….
“This section pertains to the design of … bridges of
moderate length supported by two or more single cell composite box girders…..”
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 47/83
2.3 Finished Bridge
• Design assumption: Two I-girders
• Conclusions: The bridge, as designed, would have been
sufficient to resist its design loads if it had survived itsconstruction.
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 48/83
2.4 During Construction
Failure Modes:
• b/t of top flange;
•
Top flange buckling (betweenintermediate diaphragms)
• Global Torsional buckling
IntermediateDiaphragm
Top
Flange
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 49/83
3. Analysis of Bridge Failure
Objective: To find and prove the cause of failure
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 50/83
Metal Form
Angle
Bottom Flange
Bracket
(3' apart)
Form/Catwalk
Tie-rod
(4' apart)
Web Concrete
Top Flange
Web
Hanger West
Operator
Drum
C.L. Bridge
Engine
Screed
East
3.1 Deck Construction Facilities:
3 3 El i B i
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 51/83
Top
Top Steel Plate
Bottom Steel Plate
Elastomer
Steel
Plates
a). Expansion Bearing
Top Steel Plate
Bottom Steel Plate
b). Fixed Bearing
Steel Pin
k ESk ES
k EC
X
Y
Z k BRG=k ES+k PIN
k FS
k EC
X
Y
Z
FD
Nonlinear Spring
k PIN
3.3 Elastomeric Bearings
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 52/83
0
10000
20000
30000
40000
50000
0 1 2 3 4 5 6 7 8 9 10
Deformation, mm
F o r c e ,
N
36 mm dia
Applied Force
SteelPlate
Force-Deformation CurveFixedBoundary
9 4 m m
3.4 Fixed Bearing Steel Pin Model
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 53/83
End
Diaphragm
Top Flange
Top Flange
Web
Diaphragm
Strut
3.5 Global Model
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 54/83
SW+DL (rebar, form, etc.)Concrete Screed
Steel girder
North
Abutment
-10.0
-9.0
-8.0
-7.0
-6.0
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
0.0 10.0 20.0 30.0 40.0 50.0
Concrete Pour Length, m
G i r d e r R o t a
t i o n ,
D e g r e e
As-built
As-designed (ideal)
Y
Rotation
42'
105'
3.6 Analysis Results
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 55/83
Middle Screw
Location
Edge Screw
Location3.7 Corrugated Metal Form
Form Thickness = 1.2 mm (3/64 in.)Top Flange
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 56/83
F
Fixed Boundarya
Weak Form: a=1/2" (12 mm)
Fy = 40 ksi (275 MPa)
Strong Form: a=3/4" (20 mm)Fy = 45 ksi (310 MPa)
3.9 Form Connection Model
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 57/83
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 58/83
-10.0
-9.0
-8.0
-7.0
-6.0
-5.0
-4.0
-3.0-2.0
-1.0
0.0
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0
Concrete Pour Length, m
G i r d e r
R o t a t i o n ,
D e g r e e
As-designed (ideal),
No form
As-built
No form
Strong form,
as-built
Weak
form,
as-built
42' 82'95' 105'
Y
Rotation
3.11 Force-Rotation Curve
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 59/83
4. Demolition
• Remove debris safely;
• Sample materials;
• Preserve evidence
Temp. Support
Cut Location
Objectives
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 60/83
5. Laboratory Testing
• Verify Analysis Assumptions
• Check whether materials conform to contract specifications
Objectives:
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 61/83
0
2000
4000
6000
8000
10000
12000
0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25
Lateral Deformation, mm
F o r c e ,
N
Force-Deformation Curve
of Form Connections
Strong Form Model
Weak Form Model
Lab Results
5.1 Form Connection Tests
Form connection test
Gage 12
Steel PL
Form
Screw
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 62/83
0
2000
4000
6000
8000
10000
12000
0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25
Lateral Deformation, mm
F o r c e ,
N
Force-Deformation Curve
of Form Connections
Strong Form Model
Weak Form Model
Lab Results
5.1 Form Connection Tests
Form connection test
Gage 12
Steel PL
Form
Screw
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 63/83
b. Bearing Model
Fixed Boundary
a. Damaged Fixed Bearing
5.2 Bearing Inspection
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 64/83
6. Conclusions
• The bridge failed in a global torsional mode;
• Stay-in-place forms greatly delayed thecollapse, but were not strong enough toprevent it;
• Progressive failure of form connections thatinitiated the failure sequence
• The bridge would have buckled even if thetwo deck haunches were identical
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 65/83
7. Recommendations
• Clarify applicable codes;
• Add a new code provision that requires full
length lateral bracing to be installed between
top flanges unless proven unnecessary by
analysis
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 66/83
8. NYSDOT Actions
• Reviewed similar ongoing projects in NYS.
• Required bracing systems for similar bridges in
NYS—(NYSDOT “Blue Page”)
• Sought recommendations from AASHTO
regarding code revisions.
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 67/83
AASHTO LRFD Specs. – 3rd Edition (2004)
• Art. 6.11: Provisions for single or multipleclosed-box or tub girders
• Art. 6.7.5: Lateral Bracing
– 6.7.5.3: Top lateral bracing shall be provided between flanges of individual tub sections. The
need for a full-length system shall be
investigated…
– If a full length lateral bracing system is not provided, the local stability of the top flanges and
global stability of the individual tub sections shall
be investigated for the assumed construction
sequence
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 68/83
Centroid @ +36.3” Shear Ctr. @ -36.0”
Izz = 36 in^4Iyy = 205,817 in^4
Centroid @ +37.3” Shear Ctr. @ -12.2”
Izz = 114,870 in^4Iyy = 212,572 in^4
1/16” Top Plate
Lateral Torsional Stability of Open-tub girders
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 69/83
Application to I-Girder Bridges
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 70/83
Application to I-Girder Bridges
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 71/83
Twin I-Girders: No bottom lateral bracing
Iyy = 15,470 in^4 Izz = 472 in^4
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 72/83
Centroid @ +19.96”
Shear Ctr. @ -19.06”
Izz = 472 in^4Iyy = 296,426 in^4
Twin I-Girders: With bottom lateral bracing
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 73/83
LTB with Non-linear Plate Model
0.0
0.5
1.0
1.5
2.0
2.5
0.0 20.0 40.0 60.0 80.0
Transverse Displacement at Midspan [in.]
D e a d
L o a d
F a c
t o r
Twin I-Girders: With bottom lateral bracing
6
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 74/83
LTB with Non-linear Plate ModelNo Lateral Bracing
0.0
0.5
1.0
1.5
2.0
0.0 20.0 40.0 60.0 80.0 100.0
Transverse Displacement at Midspan [in.]
D e a d
L o a d
F a c t o r
11
Twin I-Girders: No bottom lateral bracing
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 75/83
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 76/83
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 77/83
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 78/83
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 79/83
Twin I-Girder Behavior--summary
• More stable than open tub girder.
• Lateral or lateral-torsional behavior (vs. global torsional)
• Bottom lateral system effective for lateral resistance
• Consider top and bottom laterals for long, narrow spans
• No “spec-ready” equations for checking global behavior
(Single Tubs or Twin-I systems)
l h b d f l
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 80/83
Dealing with a bridge failure
• Expect your inspection program to come underscrutiny
• Expect safety of other bridges to be questioned
• Expect requests for data on failed bridge and otherbridges
• Establish point of contact for all media questions.
• Make “public” info. Easily available –
l h b d f l
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 81/83
Dealing with a bridge failure
• Work with your lawyers, (but do not expect them toalways have the same priorities).
• Establish protections for privileged material, e.g.
ongoing investigations.
O
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 82/83
The Paradox of Failure
“When it comes to bridge
design, collapse is a most
reliable teacher.”
Henry Petroski
“Success Through Failure; The
Paradox of Design”
One Final Lesson
Q i ?
7/28/2019 Recent NYSDOT Bridge Failure Ivestigations_UB Presentation
http://slidepdf.com/reader/full/recent-nysdot-bridge-failure-ivestigationsub-presentation 83/83
Questions?