Sicurezza Strutturale di Gallerie in Caso di Incendio

Sicurezza Strutturale
di Gallerie in Caso di Incendio
Prof. Ing. Franco Bontempi
Ordinario di Tecnica delle Costruzioni
Docente di TEORIA E PROGETTO DI PONTI – GESTIONE DI PONTI E GRANDI STRUTTURE
PROGETTAZIONE STRUTTURALE ANTINCENDIO
Facoltà di Ingegneria Civile e Industriale
Università degli Studi di Roma La Sapienza
franco.bontempi@uniroma1.it

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Franco Bontempi - Sicurezza Strutturale
2

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Indice
1. Strutture in sotterraneo
a. Geometrie
b. Impianti di ventilazione
2. Complessità
3. Natura accidentale
4. Azione incendio
a. Caratteristiche intensive
b. Caratteristiche estensive
5. Sviluppo di un incendio in galleria
6. Sicurezza e verifiche
7. Riferimenti
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Strutture in sotterraneo
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1

GEOMETRIE
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Tipo A - autostrade
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Tipo B – extraurbane principali
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Tipo C – extraurbane secondarie
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Altri aspetti geometrici
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Sezioni non standard
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Intersezioni
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Geometrie non tubolari
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Stazioni metropolitane
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IMPIANTI VENTILAZIONE
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Normal ventilation - Piston effect
• Is the result of natural induced draft caused by free-flowing traffic (> 50
km/h) in uni-directional tunnel thus providing natural ventilation.
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Mechanical ventilation
• “forced” ventilation is required where piston effect is not sufficient such as
in
❑congested traffic situations;
❑bi-directional tunnels (piston effect is neutralized by flow of traffic in two
opposite directions);
❑long tunnels with high traffic volumes.
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Tunnel Ventilation Systems
• Road Tunnel Ventilation Systems have two modes of operation:
• Normal ventilation, for control of air quality inside tunnels due to vehicle
exhaust emissions:
❑in any possible traffic situation, tunnel users and staff must not suffer
any damage to their health regardless the duration of their stay in the
tunnel;
❑the necessary visual range must be maintained to allow for safe
stopping.
• Emergency ventilation in case of fire, for smoke control:
❑the escape routes must be kept free from smoke to allow for self-rescue;
❑the activities of emergency services must be supported by providing the
best possible conditions over a sufficient time period ;
❑the extent of damage and injuries (to people, vehicles and the tunnel
structure itself) must be kept to a minimum.
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Longitudinal ventilation system
• employs jet fans suspended under tunnel roof; in normal operation fresh air
is introduced via tunnel entering portal and polluted air is discharged from
tunnel leaving portal.
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Semi-transverse ventilation system
• employs ceiling plenum connected to central fan room equipped with axial
fans; in normal operation fresh air is introduced along the tunnel trough
openings in the ventilation plenum while polluted air is discharged via tunnel
portals.
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Full transverse ventilation system
• employs double supply and exhaust plenums connected to central fan rooms
equipped with axial fans; in normal operation fresh air is introduced and
exhausted via openings in double ventilation plenums.
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Attachments
• Dispersion stack and fan room combined with longitudinal ventilation: may
be required in order to reduce adverse effect on environment of discharge of
polluted air from tunnel, where buildings are located in proximity (< 100m)
to tunnel leaving portal.
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Ventilation unit
Air extraction
Ventilation unit
Supply of fresh air
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Observation
• A tunnel must be considered as a system, composed of structures and
plants.
• The essential difference between structures and plants concerns the fact
that the latter require energy that is not necessary for the former.
• In synthetic terms, it can be said that structures are dead works while plants
are living works. This involves different life horizons (50-100 years for
structures, 5-10 years for plants) and consequent different levels of control
and maintenance.
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Complessità
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2

LOOSE
couplings
TIGHT
LINEAR interactions NONLINEAR
System Complexity (Perrow)
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Exactitude

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Gregory Bateson
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• La mappa non è il territorio e il nome non è la cosa designata.
• Questo principio, reso famoso da Alfred Korzybski, opera a molti livelli. Esso
ci ricorda in termini generici che quando pensiamo alle noci di cocco o ai
porci, nel cervello non vi sono né noci di cocco né porci.
• Ma in termini più astratti, la proposizione di Korzybski asserisce che sempre
quando c'è pensiero o percezione oppure comunicazione sulla percezione vi
è una trasformazione, una codificazione, tra la cosa comunicata, la Ding an
sich, e la sua comunicazione. Soprattutto, la relazione tra la comunicazione e
la misteriosa cosa comunicata tende ad avere la natura di una classificazione,
di un'assegnazione della cosa a una classe. Dare un nome è sempre un
classificare e tracciare una mappa è essenzialmente lo stesso che dare un
nome.

Multiphysics
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Factors for Coupling
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
INFORMATION
FLOW DIRECTION
time
tK
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Level 1 - Fully Coupled Scheme
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
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Level 2 - Staggered Coupled Scheme
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
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Level 3 - Temperature Driven Scheme
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
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Level 4 - Scheme With No Memory
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
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Analysis Strategy #1:
Sensitivity governance of priorities
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Bounding behavior governance
p
(p)

p
(p)

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Super
Controllore
Problema Risultato
Solutore #1
Solutore #2
Voting System
Redundancy Governance
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Multiphysics
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Fire fighting timeline
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• Context dependence
• Contrast effect
• Recency effect
• Halo effect
• Plasticity
• Order effects
• Pseudo-opinions
• Vividness
• Wishful thinking
• Anchoring
• Social loafing
• Conformity
• The representativeness heuristic
• Law of small numbers
• Hot hand
• Neglecting base rates
• No regressive prediction
• Synchronicity
• Causalation
• Salience
• Minority influence
• Groupthink
Problem Structuring
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Un caso: incendio tunnel del Monte Bianco
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Mont Blanc Tunnel fire

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On the morning of 24 March 1999, 39 people died when a Belgian transport truck carrying flour and margarine, which had entered the French-side portal, caught fire in the tunnel.[1][2]
The truck came through the tollbooth at 10:46 CET. The initial journey through the tunnel was routine.
According to the documentary television series Seconds from Disaster, the fire and smoke appeared at around 10:49.
Shortly after, the driver realized something was wrong as cars coming in the opposite direction flashed their headlights at him; a glance in his mirrors showed white smoke coming out from under
his cabin. This was not yet considered a fire emergency. In fact, there had been 16 other truck fires in the tunnel over the previous 35 years, always extinguished on the spot by the drivers.
At 10:53, the driver of the vehicle, Gilbert Degrave, stopped 6 km into the 11.6 km tunnel, in attempt to fight the fire but he was suddenly forced back when the payload violently combusted.[2]
Degrave subsequently abandoned his vehicle and ran to the Italian entrance of the tunnel.
At 10:54, one of the drivers called from refuge 22 to raise the alarm.
At 10:55, the tunnel employees triggered the fire alarm and stopped any further traffic from entering. At this point, there were at least 10 cars and 18 trucks in the tunnel that had entered from
the French side. A few vehicles from the Italian side passed the Volvo truck without stopping. Some of the cars from the French side managed to turn around in the narrow two-lane tunnel to
retreat back to France, but navigating the road in the dense smoke that had rapidly filled the tunnel quickly made this impossible.
Between 10:53 and 10:57, the smoke had already covered half a kilometer of the French side. The larger trucks were stranded, as they did not have the space to turn around, and reversing out
was not an option.
Most drivers rolled up their windows and waited for rescue. The ventilation system in the tunnel drove toxic smoke back down the tunnel faster than anyone could run to safety. These fumes
quickly filled the tunnel and starved off oxygen, disabling vehicles. This included fire engines which, once affected, had to be abandoned by the firefighters. Many drivers near the blaze who
attempted to leave their cars and seek refuge points were quickly overcome due to toxic components of the smoke, mainly cyanide.
Within minutes, two fire trucks from Chamonix responded to the unfolding disaster. Melted wiring had eliminated any possible light sources in the tunnel; in the smoke and with abandoned and
wrecked vehicles blocking their path, the fire engines were unable to proceed. Italian firefighters had come within 300 metres of the truck. Without other possibilities, fire crews abandoned their
vehicles and took refuge in two of the emergency fire cubicles (fire-door sealed small rooms set into the walls every 600 metres).
As the firefighters took refuge in a fire cubicle, burning fuel flowed down the road surface, causing tires and fuel tanks to explode and sending deadly shrapnel in the air. This is probably the point
where fire began to spread to other vehicles from the truck, at 11:00.
By 11:11, more Italian firefighters had come to tackle the fire. They also abandoned their vehicles, and searched for trapped groups of firefighters who had taken refuge in the fire cubicles. When
it was realized that the cubicles were offering little protection from the smoke, they began searching for the doors that led to the ventilation duct.
All of the firefighters were rescued five hours later by a third fire crew that responded and reached them via a ventilation duct; of the 15 firefighters who had been trapped, 14 were in serious
condition and one (their commanding officer) later died in the hospital.
Some victims were also able to escape to the fire cubicles. The original fire doors on the cubicles were rated to survive for two hours. Some had been upgraded in the 34 years since tunnel
construction to survive for four hours.
By 11:30, 37 minutes after start of the fire, smoke had reached the French entrance of the tunnel, 6 kilometers from the truck.
In total, the fire burned for 53 hours and reached temperatures of 1,000 °C (1,830 °F), mainly because of the margarine load in the trailer, equivalent to a 23,000-litre (5,100 imp gal; 6,100 US gal)
oil tanker. The fire spread to other cargo vehicles nearby that also carried combustible loads. The fire trapped around 40 vehicles in dense and poisonous smoke containing carbon monoxide and
cyanide. Due to weather conditions at the time, airflow through the tunnel was from the Italian side to the French side.[3] Authorities compounded the chimney effect by pumping in further fresh
air from the Italian side, escalating the fire whist trapping toxic fumes inside. Only vehicles past the fire on the French side of the tunnel were trapped, while cars on the Italian side of the fire
were mostly unaffected.
There were 29 deaths trapped inside of vehicles, and nine more died trying to escape on foot. All the deceased were on the French side, and were ultimately reduced to bones and ash by the
intense heat. Of the initial 50 people trapped by the fire, 12 survived, all of them from the Italian side.[2]
It was more than five days before the tunnel cooled sufficiently to start repairs.

Natura Accidentale
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3

Situazioni HPLC
High Probability Low Consequences
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Low Probability High Consequences
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HPLC vs LPHC events
HPLC
High Probability
Low Consequences
LPHC
Low Probability
High Consequences
release of energy SMALL LARGE
numbers of breakdown SMALL LARGE
people involved FEW MANY
nonlinearity WEAK STRONG
interactions WEAK STRONG
uncertainty WEAK STRONG
decomposability HIGH LOW
course predictability HIGH LOW
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The burnt out interior of the Mont Blanc Tunnel
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effect
time
decomposability
course predictability
Runaway: Progressive Collapse
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Cascade Effect / Chain Reaction
• A cascade effect is an inevitable and sometimes unforeseen chain
of events due to an act affecting a system.
• In biology, the term cascade refers to a process that, once started,
proceeds stepwise to its full, seemingly inevitable, conclusion.
• A chain reaction is the cumulative effect produced when one
event sets off a chain of similar events.
• It typically refers to a linked sequence of events where the time
between successive events is relatively small.
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Es.
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http://www.wise-uranium.org/img/stavaa.gif
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Design Strategy #1: CONTINUITY
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Design Strategy #2: Segmentation
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Tunnel with a single-point extraction system
• The usual way to control the longitudinal velocity is to provide several independent
ventilation sections.
• When a tunnel has several ventilation sections, a certain longitudinal velocity in the fire
section can be maintained by a suitable operation of the individual air ducts.
• By reversing the fan operation in the exhaust air duct, this duct can be used to supply air
and vice versa.
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Water barriers

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Approcci di analisi
HPLC
Eventi Frequenti con
Conseguenze Limitate
LPHC
Eventi Rari con
Conseguenze Elevate
Complessità:
Aspetti non lineari e
Meccanismi di interazioni
Impostazione
del problema:
DETERMINISTICA
STOCASTICA
ANALISI
QUALITATIVA
DETERMINISTICA
ANALISI
QUANTITATIVA
PROBABILISTICA
ANALISI
PRAGMATICA
CON SCENARI
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CAPITOLO 2:
SICUREZZA
E
PRESTAZONI
ATTESE
QUALITA’
CAPITOLO 3:
AZIONI
AMBIENTALI
CAPITOLO 6:
AZIONI
ANTROPICHE
CAPITOLO 4:
AZIONI
ACCIDENTALI
DOMANDA
CAPITOLO 5:
NORME
SULLE
COSTRUZIONI
CAPITOLO 7:
NORME PER LE
OPERE
INTERAGENTI
CON I TERRENI E
CON LE ROCCE,
PER GLI
INTERVENTI NEI
TERRENI E PER
LA SICUREZZA
DEI PENDII
CAPITOLO 9:
NORME
SULLE
COSTRUZIONI
ESISTENTI
PRODOTTO
CAPITOLO 11:
MATERIALI
E
PRODOTTI
PER USO
STRUTTURALE
CAPITOLO 10:
NORME PER LA
REDAZIONI DEI
PROGETTI
ESECUTIVI
CAPITOLO 8:
COLLAUDO
STATICO
CONTROLLO
D.M. 14 settembre 2005
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Il Progettista, a seguito della classificazione e della caratterizzazione delle azioni,
deve individuare le possibili situazioni contingenti in cui le azioni possono
cimentare l’opera stessa. A tal fine, è definito:
• lo scenario: un insieme organizzato e realistico di situazioni in cui l’opera
potrà trovarsi durante la vita utile di progetto;
• lo scenario di carico: un insieme organizzato e realistico di azioni che
cimentano la struttura;
• lo scenario di contingenza: l’identificazione di uno stato plausibile e
coerente per l’opera, in cui un insieme di azioni (scenario di carico) è
applicato su una configurazione strutturale.
Per ciascuno stato limite considerato devono essere individuati scenari di carico
(ovvero insiemi organizzati e coerenti nello spazio e nel tempo di azioni) che
rappresentino le combinazioni delle azioni realisticamente possibili e
verosimilmente più restrittive.
Scenari (D.M. 14 settembre 2005)
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Near miss (Wikipedia)
• A near miss, near hit or close call is an unplanned event that has the
potential to cause, but does not actually result in human injury,
environmental or equipment damage, or an interruption to normal
operation.
• OSHA defines a near miss as an incident in which no property was damaged
and no personal injury was sustained, but where, given a slight shift in time
or position, damage or injury easily could have occurred. Near misses also
may be referred to as near accidents, accident precursors, injury-free events
and, in the case of moving objects, near collisions. A near miss is often an
error, with harm prevented by other considerations and circumstances.
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Secondo una consulenza tecnica
depositata da tre esperti (Franco
Bontempi, Paolo Galli e Maria
Migliazza) alla Procura di Genova, al
2020 il 75% delle gallerie autostradali
liguri presentava elementi fuori
norma. Tre tunnel su quattro sfuggiti
alla manutenzione, ai controlli, al
rinnovamento. La consulenza è stata
redatta alla conclusione di un lungo
lavoro partito dopo il crollo del soffitto
della galleria Berté, sulla A26, il 30
dicembre del 2019.
https://www.formulapassion.it/automoto/mobility/gallerie-liguria-indagine-75-per-cento-fuori-norma-
2020-lavori-cantieri-579186.html

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Sicurezza formale
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General assumptions of EN 1990
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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 Path: Reason Model
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STRUCTURAL
SYSTEM
CHARACTERISTICS
STRUCTURAL
SYSTEM
WEAKNESS
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STRUCTURAL
CONCEPTION
STRUCTURAL
TOPOLOGY
&
GEOMETRY
threats
No
Yes
threats
STRUCTURAL
MATERIAL
& PARTS
No
Yes
passive
structural
characteristics
threats
No
Yes
STRUCTURAL
CONCEPTION
STRUCTURAL
TOPOLOGY
&
GEOMETRY
threats
No
Yes
threats
STRUCTURAL
MATERIAL
& PARTS
No
Yes
passive
structural
characteristics
threats
FIRE DETECTION
& SUPPRESSION
No
Yes
active
structural
characteristics
threats
ORGANIZATION &
FIREFIGHTERS
No
Yes
threats
MAINTENANCE
& USE
No
Yes
threats
No
alive
structural
characteristics
Yes
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FIRE DETECTION
& SUPPRESSION
active
structural
characteristics
threats
ORGANIZATION &
FIREFIGHTERS
No
Yes
threats
MAINTENANCE
& USE
No
Yes
threats
No
alive
structural
characteristics
Yes
STRUCTURAL
CONCEPTION
STRUCTURAL
TOPOLOGY
&
GEOMETRY
threats
No
Yes
threats
STRUCTURAL
MATERIAL
& PARTS
No
Yes
passive
structural
characteristics
threats
FIRE DETECTION
& SUPPRESSION
No
Yes
active
structural
characteristics
threats
ORGANIZATION &
FIREFIGHTERS
No
Yes
threats
MAINTENANCE
& USE
No
Yes
threats
No
alive
structural
characteristics
Yes
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Conceptual Design
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Conceptual Design
MULTI-HAZARD
BLACK-SWAN
DISASTER CHAIN
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Azione Incendio
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4

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•Accidental features
•Intensive features
•Extensive features

INTENSIVE FEATURES
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ISO 13387: Example of Design Fire
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Energie coinvolte

Andamento nel tempo potenza termica
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Incipient
period
Growth period Burning period Decay period
Fire
behavior
Heating
of fuel
Fuel
controlled burning
Ventilation
controlled burning
Fuel
controlled burning
Human
behavior
Prevent
ignition
Extinguish by hand,
escape
Death
Detection Smoke
detectors
Smoke detectors,
heat detectors
External smoke and flame
Active
control
Prevent
ignition
Extinguish by
sprinklers or fire
fighters; control of
smoke
Control by fire-fighters
Passive
control
- Select materials with
resistance to flame
spread
Provide fire resistance;
contain fire, prevent collapse
T
time
Buchanan,
2002
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flashover
STRATEGIE
ATTIVE
(approccio
sistemico)
STRATEGIE
PASSIVE
(approccio
strutturale)
Tempo t
Temperatura
T(t)
andamento di T(t) a
seguito del successo
delle strategie attive
flashover
STRATEGIE
ATTIVE
(approccio
sistemico)
STRATEGIE
PASSIVE
(approccio
strutturale)
Tempo t
Temperatura
T(t)
andamento di T(t) a
seguito del successo
delle strategie attive
Strategie
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F
L
A
S
H
O
V
E
R
passive
▪ Create fire
compartments
▪ Prevent damage
in the elements
▪ Prevent loss of
functionality in
the building
active
▪ Detection measures
(smoke, heat, flame
detectors)
▪ Suppression
measures (sprinklers,
fire extinguisher,
standpipes, firemen)
▪ Smoke and heat
evacuation system
prevention protection robustness
▪ Limit ignition
sources
▪ Limit hazardous
human behavior
▪ Emergency
procedure and
evacuation
▪ Prevent the
propagation of
collapse, once
local damages
occurred (e.g.
redundancy)
Fire Safety Strategies
systemic structural
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active
protection
passive
protection
no
failures
doesn’t
trigger
Y
N
Y
N
spreads
extinguishes
damages
Y
N
robustness
no
collapse
collapse
Y
N
triggers
prevention
1 4
2 3
Fire Safety Strategies
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SnakeFighter
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EXTENSIVE FEATURES
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Windsor Hotel Madrid

Windsor Hotel Madrid
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The Great Fire of Chicago, October 7-10, 1871
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Sviluppo di un incendio in galleria
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5

Tunnel Fires vs Compartment Fires (1)
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Tunnel Fires Progression (0)
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Tunnel Fires Progression (1)
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Effects of ventilation
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Temperature development
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Smoke development
• A smoke layer may be created in tunnels at the early stages of a fire with
essentially no longitudinal ventilation. However, the smoke layer will
gradually descend further from the fire.
• If the tunnel is very long, the smoke layer may descend to the tunnel surface
at a specific distance from the fire depending on the fire size, tunnel type,
and the perimeter and height of the tunnel cross section.
• When the longitudinal ventilation is gradually increased, the stratified layer
will gradually dissolve.
• A backlayering of smoke is created on the upstream side of the fire.
• Downstream from the fire there is a degree of stratification of the smoke
that is governed by the heat losses to the surrounding walls and by the
turbulent mixing between the buoyant smoke layers and the normally
opposite moving cold layer.
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Backlayering
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Temperature along the tunnel
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Maximum gas temperatures in the ceiling area

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Maximum gas temperatures in the ceiling area

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Maximum gas temperatures in the cross section

CURVE TEMPERATURE-TEMPO
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• Defined in various national standards, i.e. ISO 834, BS 476: part 20, DIN 4102, AS 1530 etc.
• This curve is the lowest used in normal practice.
• It is based on the burning rate of the materials found in general building materials.
Cellulosic curve
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• Although the cellulosic curve has been in use for many years, it soon became apparent that the
burning rates for certain materials i.e. petrol gas, chemicals etc, were well in excess of the rate at
which for instance, timber would burn.
• The hydrocarbon curve is applicable where small petroleum fires might occur, i.e. car fuel tanks,
petrol or oil tankers, certain chemical tankers etc.
Hydrocarbon (HC) curve
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• Increased version of the hydrocarbon curve, prescribed by the French regulations.
• The maximum temperature of the HCM curve is 1300ºC instead of the 1100ºC, standard HC curve.
• However, the temperature gradient in the first few minutes of the HCM fire is as severe as all
hydrocarbon based fires possibly causing a temperature shock to the surrounding concrete
structure and concrete spalling as a result of it.
Hydrocarbon modified (HCM) curve
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• The RABT curve was developed in Germany as a result of a series of test programs such as the
EUREKA project. In the RABT curve, the temperature rise is very rapid up to 1200°C within 5
minutes.
• The failure criteria for specimens exposed to the RABT-ZTV time-temperature curve is that the
temperature of the reinforcement should not exceed 300°C. There is no requirement for a
maximum interface temperature.
RABT-ZTV (train)
Time (minutes) T (°C)
0 15
5 1200
60 1200
170 15
RABT-ZTV (car)
Time (minutes) T (°C)
0 15
5 1200
30 1200
140 15
RABT ZTV curves
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• The RWS curve was developed by the Ministry of Transport in the Netherlands. This curve is based
on the assumption that in a worst case scenario, a 50 m³ fuel, oil or petrol, tanker fire with a fire
load of 300MW could occur, lasting up to 120 minutes.
• The failure criteria for specimens is that the temperature of the interface between the concrete and
the fire protective lining should not exceed 380°C and the temperature on the reinforcement should
not exceed 250°C.
RWS, RijksWaterStaat
Time
(minutes)
T
(°C)
0 20
3 890
5 1140
10 1200
30 1300
60 1350
90 1300
120 1200
180 1200
RWS (Rijkswaterstaat) curve
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Types of fire exposure for tunnel analysis
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0
200
400
600
800
1000
1200
1400
0 30 60 90 120 150 180
Temperature (
ƒ
C)
Time (min.)
Cellulosic Hydrocarbon Hydrocarbon modified
RABT-ZTV train RABT-ZTV car RWS

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Lönnermark, A. and Ingason, H., “Large Scale Fire Tests in the Runehamar tunnel – gas
temperature and Radiation”, Proceedings of the International Seminar on Catastrophic
Tunnel Fires, Borås, Sweden, 20-21 November 2003.
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Fire Scenario Recommendation
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Eurocodes

EMERGENCY VENTILATION
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Multiphysics
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Smoke stratification
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Natural smoke venting
• It can be sufficient in short, level tunnels where smoke stratification allows
for escape in clear/tenable conditions.
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Smoke filling long tunnel
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Emergency ventilation with longitudinal system
• It can be employed in unidirectional, medium length tunnels, with free-
flowing traffic conditions. Smoke is mechanically exhausted in direction of
traffic circulation, clear tenable conditions for escape are obtained on
upstream side of fire.
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Ventilation with semi-transverse “point extraction”
• Smoke is mechanically exhausted from single ceiling opening (reverse mode)
leaving clear tenable escape conditions on both sides of fire.
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Goal #1

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Goal #2

k size factor for HGV fire
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k size factor for small pool fire
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Observation: goal
• The purpose of controlling the spread of smoke is to keep people as long as
possible in a smoke-free environment.
• This means that the smoke stratification must be kept intact, leaving a more
or less clear and breathable air underneath the smoke layer.
• The stratified smoke is taken out of the tunnel through exhaust openings
located in the ceiling or at the top of the sidewalls.
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EU directive 2004/54/EC sec. 2.9 - Ventilation
• Criteria concerning minimum requirements for installation of mechanical
ventilation:
• 9.2.2 - A mechanical ventilation system shall be installed in all tunnels longer
than 1,000 meters with a traffic volume higher than 2,000 vehicles per lane
(per day).
• 2.9.3 - In tunnels with bi-directional and/or congested unidirectional traffic,
longitudinal ventilation shall be allowed only if a risk analysis according to
Article 13 shows it is acceptable and/or specific measures are taken, such as
appropriate traffic management, shorter emergency exit distances, smoke
exhausts at intervals.
• 2.9.4 - Transverse or semi-transverse ventilation systems shall be used in
tunnels where a mechanical ventilation system is necessary and longitudinal
ventilation is not allowed under point 2.9.3. These systems must be capable
of evacuating smoke in the event of a fire.
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Observation: longitudinal velocity
• With practically zero longitudinal air velocity, the smoke layer expands to
both sides of the fire. The smoke spreads in a stratified way for up to 10 min.
• After this initial phase, smoke begins to mix over the entire cross section,
unless by this time the extraction is in full operation.
• The longitudinal velocity of the tunnel air must be below 2 m/s in the vicinity
of the fire incidence zone. With higher velocities, the vertical turbulence in
the shear layer between smoke and fresh air quickly cools the upper layer
and the smoke then mixes over the entire cross section.
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Observations: turbulence
• With an air velocity of around 2 m/s, most of the smoke of a medium-size
fire spreads to one side of the fire (limited backlayering) and starts mixing
over the whole cross section at a distance of 400 to 600 m downstream of
the fire site. This mixing over the cross section can also be prevented if the
smoke extraction is activated early enough.
• Vehicles standing in the longitudinal air flow increase strongly the vertical
turbulence and encourage the vertical mixing of the smoke.
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Observation: fresh air
• In a transverse ventilation system, the fresh air jets entering the tunnel at
the floor level induce a rotation of the longitudinal airflow, which tends to
bring the smoke layer down to the road.
• No fresh air is to be injected from the ceiling in a zone with smoke because
this increases the amount of smoke and tends to suppress the stratification.
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Observation: smoke extraction
• In reversible semi-transverse ventilation with the duct at the ceiling, the
fresh air is added through ceiling openings in normal ventilation operation.
• If a fire occurs, as long as fresh air is supplied through ceiling openings, the
smoke quantity increases by this amount and strong jets tend to bring the
smoke down to the road surface. The conversion of the duct from supply to
extraction must be done as quickly as possible.
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Observation: traffic conditions
• For a tunnel with one-way traffic, designed for queues (an urban area), the
ventilation design must take into consideration that cars can likely stand to
both sides of the fire because of the traffic. In urban areas it is usual to find
stop-and-go traffic situations.
• For a tunnel with two-way traffic, where the vehicles run in both directions,
it must be taken into consideration that in the event of a fire vehicles will
generally be trapped on both sides of the fire.
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Strategies
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Smoke extraction
• Continuous extraction into a return air duct is needed to remove a stratified
smoke layer out of the tunnel without disturbing the stratification.
• The traditional way to extract smoke is to use small ceiling openings
distributed at short intervals throughout the tunnel.
• Another efficient way to remove smoke quickly out of the traffic space is to
install large openings with remotely controlled dampers. They are normally
in an open position where equal extraction is taking place over the whole
tunnel length.
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VENTILATION MODELING
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Levels
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1D
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1D
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2D (zone model)
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2D (zone model)
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FDS Simulation
3D
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FDS Simulation
3D
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3D
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Multiscala
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Multiscala
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Multiscala
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Multiscala (strutturale)
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Multiscala (strutturale)
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Sicurezza e verifica
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6

BASIS
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Design Process - ISO 13387
A. Design constraints and possibilities (blue),
B. Action definition and development (red),
C. Passive system and active response (yellow),
D. Safety and performance (purple).
3/22/2011
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SS0a
PRESCRIBED
DESIGN
PARAMETERS
SS0b
ESTIMATED
DESIGN
PARAMETERS
SS1
initiation and
development
of fire and
fire efluent
SS2
movement of
fire effluent
SS3
structural response
and fire spread
beyond enclosure
of origin
SS4
detection,
activitation and
suppression
SS5
life safety:
occupant behavior,
location and
condition
SS6
property
loss
SS7
business
interruption
SS8
contamination
of
environment
SS9
destruction
of
heritage
(0)
DESIGN
CONSTRAINTS
AND
POSSIBILITIES
(1+2)
ACTION
DEFINITION
AND
DEVELOPMENT
(3+4)
SYSTEM
PASSIVE
AND ACTIVE
RESPONSE
BUS
OF
INFORMATION
RESULTS
DESIGN
ACTION
RESPONSE
SAFETY
&
PERFORMANCE
FSE
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Buchanan,
2002
0
1
2
3
4
5
6
7
8
9
Strategie per
la gestione
dell'incendio
1
Prevenzione
2
Gestione
dell'evento
3
Gestione
dell'incendio
4
Gestione delle
persone e
dei beni
15
Difesa sul posto
16
Spostamento
17
Disposibilità
delle vie
di fuga
18
Far avvenire
il deflusso
19
Controllo
della quantità
di
combustibile
5
Soppressione
dell'incendio
10
Controllo
dell'incendio
attraverso il
progetto
13
Automatica
11
Manuale
12
Controllo dei
materiali
presenti
6
Controllo
del movimento
dell'incendio
7
Resistenza e
stabilità
strutturale
14
Contenimento
9
Ventilazione
8
Fire safety concepts tree (NFPA)
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Line 2
• La gestione dell’incendio non è necessaria se si previene l’ignizione.
• Può essere solo ridotta la probabilità che avvenga l’ignizione.
• Gli incendi dolosi è difficile da prevedere dal progettista
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Line 4
Exposed persons and property can be managed by moving them from the building
or by defending them in place; in order for people to move, the fire must be
detected, the people must be notified, and there must be a suitable safe path for
movement.
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Line 6
There are three options for managing a fire; in the first case the fuel source can be controlled, by limiting the
amount of fuel or the geometry; the second options is to suppress the fire; the third is to control the fire by
construction. Control fire by construction it is necessary to both control the movement of the fire and provide
the structural stability.
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Line 9 - The two strategies for controlling fire movement are:
a. fire venting: venting can be by an active system of mechanically operated vents, or a passive system that
relies on the melting of plastic skylights; in either case, the increased ventilation may increase the local severity
of the fire, but fire spread within the building and the overall thermal impact on the structure will be reduced;
b. containment of a fire to prevent spread is the principal tool of passive fire protection; preventing fire growing
to a large size is ne of the most important components of a fire safety strategy; radiant spread of the fire to
neighboring buildings must also be prevented, by limiting the size of openings in exterior walls. Smoke
containment can also controlled by venting or containment; pressurizations and smoke barriers can also used.
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Basis of tunnel fire safety design
• The first priority identified in the literature for fire design of all
tunnels is to ensure:
1. Prevention of critical events that may endanger human life, the
environment, and the tunnel structure and installations.
2. Self-rescue of people present in the tunnel at time of the fire.
3. Effective action by the rescue forces.
4. Protection of the environment.
5. Limitation of the material and structural damage.
• Furthermore, part of the objective is to reduce the consequences
and minimize the economic loss caused by fires.
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RISK CONCERN
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216
Option 1 Risk avoidance, which usually means not
proceeding to continue with the system; this is
not always a feasible option, but may be the only
course of action if the hazard or their probability
of occurrence or both are particularly serious;
Option 2 Risk reduction, either through (a) reducing the
probability of occurrence of some events, or (b)
through reduction in the severity of the
consequences, such as downsizing the system, or
(c) putting in place control measures;
Option 3 Risk transfer, where insurance or other financial
mechanisms can be put in place to share or
completely transfer the financial risk to other
parties; this is not a feasible option where the
primary consequences are not financial;
Option 4 Risk acceptance, even when it exceeds the criteria,
but perhaps only for a limited time until other
measures can be taken.

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DEFINE SYSTEM
(the system is usually decomposed into
a number of smaller subsystems and/or
components)
HAZARD SCENARIO ANALYSIS
(what can go wrong?
how can it happen?
waht controls exist?)
ESTIMATE
CONSEQUENCES
(magnitude)
ESTIMATE
PROBABILITIES
(of occurrences)
DEFINE
RISK SCENARIOS
SENSITIVITY
ANALYSIS
RISK
ANALYSIS
FIRE
EVENT
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219
Simulations
DEFINE SYSTEM
(the system is usually decomposed into
a number of smaller subsystems and/or
components)
HAZARD SCENARIO ANALYSIS
(what can go wrong?
how can it happen?
waht controls exist?)
ESTIMATE
CONSEQUENCES
(magnitude)
ESTIMATE
PROBABILITIES
(of occurrences)
DEFINE
RISK SCENARIOS
SENSITIVITY
ANALYSIS
RISK
ANALYSIS
NUMERICAL
MODELING

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Point of view for life safety risks
• Individual risk
The purpose of the individual risk is to ensure that individuals in the society
are not exposed to unacceptably high risks.
It can be defined as the risk to any occupant on the scene for the
event/hazard scenario i.e. it is the risk to an individual and not to a group of
people.
• Societal risk
One is not looking at one individual, but it is concerned with the risk of
multiple fatalities.
People are treated as a group, there are no considerations taken to the
individuals within the group: the definition of the risk is from a societal point
of view.
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F (frequency) – N (number of fatalities) curve
• An F–N curve is an alternative way of describing the risk associated with loss
of lives.
• An F–N curve shows the frequency (i.e. the expected number) of accident
events with at least N fatalities, where the axes normally are logarithmic.
• The F–N curve describes risk related to large-scale accidents, and is thus
especially suited for characterizing societal risk.
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FN-curves UK Road Rail Aviation Transport, 67-01

Persson, M. Quantitative Risk Analysis Procedure for the Fire Evacuation of a
Road Tunnel - An Illustrative Example. Lund, 2002
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Risk acceptance – ALARP (1)
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228
Risk acceptance – ALARP (2)

Risk reduction by design
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What is the maximum amount the society (or the decisionmaker) is
willing to pay to reduce the expected number of fatalities by 1?
Typical numbers for the value of a statistical life used in
cost-benefit analysis are 1–10 million euros.
Monetary values – cost of human life (!)
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STRUCTURAL CONCERN
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Mechanical Analysis
• The mechanical analysis shall be performed for the same duration as used in
the temperature analysis.
• Verification of fire resistance should be in:
• in the strength domain: Rfi,d,t ≥ Efi,requ,t
(resistance at time t ≥ load effects at time t);
• in the time domain: tfi,d ≥ tfi,requ
(design value of time fire resistance ≥
time required)
• In the temperature domain: Td ≤ Tcr
(design value of the material temperature ≤ critical material
temperature);
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Verification of fire resistance (3D)
R = structural resistance
T = temperature
t = time
T=T(t)
R=R(t,T)=R(t,T(t))=R(t)
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Verification of fire resistance (R-safe)
T = temperature
t = time
Rfi,d,t
Efi,requ,t
15-Dec-22 235

Verification of fire resistance (R-fail)
T = temperature
t = time
Efi,requ,t
Rfi,d,t
Failure !
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Verification of fire resistance (t)
T = temperature
t = time
Efi,requ,t
Rfi,d,t
Failure !
tfi,d ≥ tfi,requ
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Verification of fire resistance (T)
T = temperature
t = time
Efi,requ,t
Rfi,d,t
Failure !
Td ≤ Tcr
15-Dec-22 238

Verification of fire resistance (T)
T = temperature
t = time
Efi,requ,t
Rfi,d,t
Failure !
Td ≤ Tcr
15-Dec-22 239

Aspetti di analisi non lineare
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Level 3 - Temperature Driven Scheme
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
time
tK
TERMAL
STATE
(Temperature Field
and Termic Related
Properties)
MECHANICAL
STATE
(Strain and Stress
Fields and
Mechanical related
Properties)
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Non linearità di materiale

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Calcestruzzo in compressione

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Calcestruzzo a trazione

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Acciaio per barre

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Parametri

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Coefficiente di dilatazione termica

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Dilatazione termica acciai

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Spalling

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https://www.youtube.com/watch?v=36WlIzOVx30

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March 24, 1999 - Mont Blanc Tunnel fire. 39 dead.

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https://www.intechopen.com/chapters/51837

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Temperature distribution at the depth of the cross-section after
(a) t = 5 min, (b) t = 10 min and (c) t = 30 min of fire exposure

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https://www.intechopen.com/chapters/51837

Introduction
• As the most typical form, spalling is defined as the violent or nonviolent
breaking off of layers or pieces of concrete from the surface of a structural
element when exposed to high and rapidly rising temperature under fire
conditions.
• All that spalling could be grouped into four categories: (a) aggregate
spalling, (b) corner spalling, (c) surface spalling, and (d) explosive spalling.
• As shown in, aggregate spalling, surface spalling, and explosive spalling occur
during the first 7–30 minutes in a fire, accompanied by popping sounds
(aggregate spalling) or violent explosions (surface and explosive spalling).
• Spalling may also occur nonviolently (corner spalling) later in a fire when the
concrete has so weakened after a period of heating of 30–90 minutes that
cracks develop, and pieces fall off its surface. The most important of these is
explosive spalling, which occurs violently and results in serious loss of
material.
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272
Time of occurrence of different types of spalling in fire

Mechanisms of explosive spalling
• The most recent theories of the causes of explosive spalling indicate that
three factors play a crucial role, i.e., (a) the build-up of pore pressure, (b)
thermal stresses, and (c) combined high pore pressure and thermal stress in
the concrete when exposed to a rapidly increasing temperature.
• The first hypothesis supposes that heating produces water vapor in concrete
and as the permeability of HPC is low, which limits the ability of vapor to
escape, a build-up of vapor pressure results.
• The second possibility is thermal stresses close to the heated surface due to
preload or a high temperature gradient caused by a high heating rate.
• Third, a combination of both phenomena is also possible.
• These different mechanisms may act individually or on combination
depending upon the moisture content, the section size, and the material.
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1 - Pore pressure spalling
• The hypothesis is that the spalling is due to the build-up of very high pore
pressures within the concrete as a result of the liquid-vapor transition of the
capillary pore water as well as that bound in the cement paste component of
the concrete (so-called moisture clog spalling).
• Heating on the surface of concrete results in a temperature gradient, which
forces moisture into the internal of the concrete as well as out of the
surface.
• The explosive spalling occurs when the pore pressure in the matrix
accumulates to a threshold exceeding their tensile strength
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274

2 - Thermal stress spalling
• Thermal stresses will occur inside the concrete due to temperature gradients
from the heated surface toward the inner, cooler sections of the concrete.
• These gradients will increase with rapid heating rates. Different strains due
to the thermal gradient are deemed to cause tensile and compressive
stresses, depending on the thermal and mechanical properties of the
concrete. Hindered expansion, loads, and restraints as well as the heating
rate are mentioned as further parameters.
• Failure due to spalling is considered to exceed the compressive strength of
the concrete close to the heated surface. The compressive stresses due to
the thermal gradient also lead to tensile stresses in the cooler sections of the
concrete.
• Explosive spalling only due to thermal stresses is relatively a rare occurrence
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276
Mechanism of thermal stress spalling

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277
3
-
Explosive
spalling
caused
by
combined
thermal
stresses
and
pore
pressure

Note
• Although theoretical modeling for the various spalling forms has been
attempted in the past, it is recently that significant development has been
made in this field.
• The complex combined nature of the influences of moisture content, pore
pressures, and thermal stresses in the heterogeneous concrete material with
complex pore structure, which varies markedly with temperature during first
heating, does not lend themselves easily to analytical modeling.
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278

Factors influencing spalling
• Based on the spalling mechanisms, the main factors leading to the explosive
spalling of concrete at high temperatures are heating rate, permeability of
concrete, moisture content, presence of reinforcement, and level of external
applied load, but more factors have been identified in the literature review
as influencing on the risk and extent of spalling.
• The factors influencing to the explosive spalling of concrete can be classified
into three categories as follows:
1.Material-related factors.
2.Structural or mechanical factors.
3.Heating characteristics.
• However, some of these factors would fit into more than one category.
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Use of various fibers to prevent the explosive spalling

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Non linearità geometrica

282
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Indice
1. Strutture in sotterraneo
a. Geometrie
b. Impianti di ventilazione
2. Complessità
3. Natura accidentale
4. Azione incendio
a. Caratteristiche intensive
b. Caratteristiche estensive
5. Sviluppo di un incendio in galleria
6. Sicurezza e verifiche
7. Riferimenti
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ACKNOWLEDGEMENTS
• Dr. Konstantinos GKOUMAS – Uniroma1
• Dr. Francesco PETRINI – Uniroma1
• Ing. Alessandra LO CANE – MIT
• Dr. Filippo GENTILI – Coimbra (PT)
• Mr. Tiziano BARONCELLI – Uniroma1
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Riferimenti
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7

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DIRETTIVA 2004/54/CE DEL PARLAMENTO EUROPEO E DEL CONSIGLIO
del 29 aprile 2004
relativa ai requisiti minimi di sicurezza per le gallerie della rete stradale
transeuropea
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CV
• Franco Bontempi - Nato 1963. Servizio militare 1989. Laurea Ingegneria
Civile 1988 e Dottorato di Ricerca in Ingegneria Strutturale 1993, Politecnico
di Milano.
• Dal 2000, Professore Ordinario di Tecnica delle Costruzioni alla Facoltà di
Ingegneria Civile e Industriale dove insegna TEORIA E PROGETTO DI PONTI,
GESTIONE DI PONTI E GRANDI STRUTTURE, PROGETTAZIONE STRUTTURALE ANTINCENDIO.
• Periodi di ricerca: Harbin Institute of Technology (CHINA), Univ. of Illinois
Urbana-Champaign (USA), TU Karlsruhe (D), TU Munich (D). Consulente per
progetto e analisi di strutture speciali, procedimenti di ingegneria forense.
• https://sites.google.com/a/uniroma1.it/francobontempi/
• https://fr.linkedin.com/in/francobontempi
• https://www.youtube.com/channel/UCW3IyXTBJVIiS6OZeSdIN7g/videos
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https://sitES.google.com/a/uniroma1.it/francobontempi/
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311

https://www.youtube.com/channel/UCW3IyXTBJVIiS6OZeSdIN7g
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312

https://fr.linkedin.com/in/francobontempi
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