Lezione #B:
Structural Robustness of Bridges and Viaducts
PONTI E GRANDI STRUTTURE - A.A. 2022/23
Franco Bontempi
Professore Ordinario di Tecnica delle Costruzioni
Facoltà di Ingegneria Civile e Industriale
UNIVERSITÀ DEGLI STUDI DI ROMA LA SAPIENZA
Via Eudossiana 18 - 00184 Roma – ITALIA
franco.bontempi@uniroma1.it

Index
• DISASTROUS FAILURES
• STRUCTURAL ROBUSTNESS IN THE NARROW SENSE
• STRUCTURAL ROBUSTNESS IN A GENERAL SENSE
• HUMAN ERROR
• MANAGING THE UNEXPECTED
- Unexpected events
- HRO
- HRO principles
- People
- Culture
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NTC 2018
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NTC 2018
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La scoperta dell’acqua calda
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1846
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2005

https://www.slideshare.net/FrancoBontempi/robustezza-strutturale-113343022
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DISASTROUS FAILURES
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Can an airplane crash because it
punctured a tire?
1
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Structural Robustness of Bridges and Viaducts

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Structural Robustness of Bridges and Viaducts

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Structural Robustness of Bridges and Viaducts

1. During takeoff from runway 26 right at Roissy
Charles de Gaulle Airport, shortly before
rotation, the front right tyre (tyre No 2) of the
left landing gear ran over a strip of metal, which
had fallen from another aircraft, and was
damaged.
2. Debris was thrown against the wing structure
leading to a rupture of tank 5.
3. A major fire, fuelled by the leak, broke out
almost immediately under the left wing.
4. Problems appeared shortly afterwards on engine
2 and for a brief period on engine 1.
5. The aircraft took off. The crew shut down engine
2, then only operating at near idle power,
following an engine fire alarm.
6. They noticed that the landing gear would not
retract.
7. The aircraft flew for around a minute at a speed
of 200 kt and at a radio altitude of 200 feet, but
was unable to gain height or speed. Engine 1
then lost thrust, the aircraftªs angle of attack
and bank increased sharply. The thrust on
engines 3 and 4 fell suddenly.
8. The aircraft crashed onto a hotel. 22

1
0
2
3
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How will this bridge die?
2
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Es.: genetics
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https://en.wikipedia.org/wiki/Alm%C3%B6_Bridge
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The Almö Bridge (inaugurated in 1960), that connected the island of
Tjörn (Sweden's 7th largest island) to the mainland. The bridge collapsed
January 18th 1980, when the bulk carrier MS Star Clipper struck the
bridge arch. Eight people died that night as they drove over the edge
until the road on the Tjörn side was closed 40 minutes after the
accident. A new cable-stayed bridge, Tjörn Bridge, was built and
inaugurated in 1981.
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Minnesota I-35W Bridge
3
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Downtown
District
I-35W Bridge
Source: Google Earth
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Bridge Scheme (1)
DNA - INTRINSIC NATURE OF THE BRIDGE STRUCTURE:
Load Path – Redundancy – Robustness – Survaivability
Reliability - Availability – Maintenability - Safety
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The fixed bearing assemblies were located at piers 1, 3, 7, 9, 12, and 13.
Expansion (sliding) bearings were used at the south and north abutments and at piers 2,
4, 10, and 11.
Expansion roller bearings were used at piers 5, 6, and 8.
Bridge Scheme (2)
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The fixed bearing assemblies were located at piers 1, 3, 7, 9, 12, and 13.
Expansion (sliding) bearings were used at the south and north abutments and at piers 2,
4, 10, and 11.
Expansion roller bearings were used at piers 5, 6, and 8.
Bridge Scheme (3)
+
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Structural Robustness of Bridges and Viaducts

Roller #5
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• Structural integrity is the term used for the performance
characteristic applied to a component, a single structure,
or a structure consisting of different components.
• Structural integrity is the ability of an item to hold
together under a load, including its own weight, resisting
breakage or bending. It assures that the construction will
perform its designed function, during reasonable use, for
as long as the designed life of the structure.
• Items are constructed with structural integrity to ensure
that catastrophic failure does not occur, which can result
in injuries, severe damage, death, or monetary losses.
Structural Integrity
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1
Roller #4
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The fixed bearing assemblies were located at piers 1, 3, 7, 9, 12, and 13.
Expansion (sliding) bearings were used at the south and north abutments and at piers 2,
4, 10, and 11.
Expansion roller bearings were used at piers 5, 6, and 8.
Bridge Scheme (3)
+
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Structural Robustness of Bridges and Viaducts

Bridge Scheme (4)
-
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Structural Robustness of Bridges and Viaducts

2
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Structural Robustness of Bridges and Viaducts

Time (not scaled)
Critical
load
(not
scaled)
Original
design
2007
modification
1998
modification
1977 modification
Instantaneousload
Lower bound of load
Upper bound of load
Failure
level
Precise moment
of failure
3
Crossing the Threshold of Failure
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Structural Robustness of Bridges and Viaducts

Compression
diagonal
Tension
diagonal
Orange and red shading:
exceeds yield stress
Stress
Yield
stress
0
Allowable
Dead Load of Original 1967 Bridge
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Orange and red shading:
exceeds yield stress
Compression
diagonal
Tension
diagonal
Stress
Yield
stress
0
Allowable
After 1977 and 1998 Modifications
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Compression
diagonal
Tension
diagonal
Orange and red shading:
exceeds yield stress
Stress
Yield
stress
0
Allowable
Loads at Time of Accident
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Structural Robustness of Bridges and Viaducts

4
5
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HAZARD
I
N
-
D
E
P
T
H
D
E
F
E
N
C
E
HOLES DUE TO
ACTIVE ERRORS
HOLES DUE TO
HIDDEN ERRORS
Failure Logic
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NTSB
TT
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15/67
Sub-structured model
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FORWARD
ANALYSIS
BACK
ANALYSIS
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COSE – STRUTTURE - SISTEMI
THINGS – STRUCTURES - SYSTEMS
PERSONE – COMPORTAMENTI
PEOPLE – HUMAN BEHAVIOR
COSA
WHAT
CHI
WHO
ROTTURA – COLLASSO - CRISI
FAILURES – COLLPASE - CRISIS
PERCHE’
WHY
SPIEGAZIONE – CAUSE
REASONS - DISCLOSURE
CONOSCENZA
KONWLEDGE
Forensic Engineering
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Knowledge Development
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RESISTANCE OF GUSSET PLATES:
✓GUSSET PLATES IN TENSION
✓GUSSET PLATES SUBJECT TO SHEAR
✓GUSSET PLATES IN COMPRESSION
FHWA GUIDELINES, (2009)
26/67
RESISTANCE OF FASTENERS
✓SHEAR RESISTANCE OF FASTENERS
✓PLATE BEARING RESISTANCEAT FASTENERS
http://bridges.transportation.org/Documents/FHWA-IF-09
014LoadRatingGuidanceandExamplesforGussetsFebruary2009rev3.pdf
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After this tragedy, the Federal Highway Administration (FHWA) focused its attention on all the
465 steel deck truss bridges present in the National Bridge Inventory [NTSB, 2008].
“The term “fracture critical” indicates that if one main component of a bridge fails, the entire
structure could collapse. Therefore, a fracture critical bridge is a steel structure that is designed
with little or no load path redundancy. Load path redundancy is a characteristic of the design that
allows the bridge to redistribute load to other structural members on the bridge if any one member
loses capacity. “
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I-35W SAINT ANTHONY FALLS BRIDGE (September 2008)
Thereare 323 sensors that regularly measure bridge conditions
such as deck movement, stress, and temperature
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http://www.startribune.com/new-35w-bridge-already-is-
aging/268746561/
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Structural Robustness of Bridges and Viaducts

Opening day was six years ago, and the I-35W bridgeis needing repairs — somethat come
from our harsh winters, but some from improper installations.
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Examples
4
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Es.
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For six days in January 1998, freezing rain coated
Ontario, Quebec and New Brunswick with 7-11
cm (3-4 in) of ice. Trees and hydro wires fell and
utility poles and transmission towers came
down causing massive power outages, some for
as long as a month. It was the most expensive
natural disaster in Canada. According to
Environment Canada, the ice storm of 1998
directly affected more people than any other
previous weather event in Canadian history.
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Es.
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https://californiawaterblog.com/2
016/05/01/the-collapse-of-water-
exports-los-angeles-1914/
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Es.
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Es.
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http://urbanplanet.info/architecture/par
is-air-terminal-collapse-report-france/
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Es.
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http://www.wise-uranium.org/img/stavaa.gif
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System Complexity (Perrow)
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Es.
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Seismic Action
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Critical Node
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FAR FIELD ZONE
EXCHAGE ZONE
STRUCTURE
FAR FIELD ZONE
EXCHAGE ZONE
STRUCTURE
INFRASTRUCTURE
OBJECT
NET
Local / Punctual
Scale
Global / Regional
Scale
Structural
System
Infrastructural
System
Also if artificial,
these systems
need to have
necessarily
evolutive soundness,
ecological coherence
and sustainability
chara