Progettazione Strutturale Antincendio: Robustezza Strutturale

Progettazione Strutturale Antincendio
ROBUSTEZZA STRUTTURALE
Franco Bontempi
Professore Ordinario di Tecnica delle Costruzioni
Facoltà di Ingegneria Civile e Industriale
Sapienza Università di Roma
franco.bontempi@uniroma1.it

Can an airplane crash
because
it punctured a tire?
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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.
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1
0
2
3
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Requisiti
12
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Requisiti strutturali
• Condizioni di esercizio:
• Rigidezza
• Condizioni ultime:
• Resistenza
• Stabilita’
• Duttilita’
• Durabilita’
• Condizioni estreme:
• Robustezza
• Resilienza
• Configurazione nominale
della struttura
• Configurazione danneggiata
della struttura
13

Robustezza / Durabilita’
14

RESILIENCE
15

Definizioni
16

Levels of Structural Crisis
Usual
ULS
&
SLS
Verification
Format
Structural Robustness
Assessment
1st level:
Material
Point
2nd level:
Element
Section
3rd level:
Structural
Element
4th level:
Structural
System 17

18
Structural Robustness (1)
ATTRIBUTES
RELIABILITY
AVAILABILITY
SAFETY
MAINTAINABILITY
INTEGRITY
SECURITY
FAILURE
ERROR
FAULT
permanent interruption of a system ability
to perform a required function
under specified operating conditions
the system is in an incorrect state:
it may or may not cause failure
it is a defect and represents a
potential cause of error, active or dormant
THREATS
NEGATIVE CAUSE
STRUCTURAL
QUALITY
more robust
less robust

• Capacity of a construction to show regular
decrease of its structural quality due to
negative causes.
• It implies:
a) some smoothness of the decrease of
structural performance due to negative
events (intensive feature);
b) some limited spatial spread of the
rupture (extensive feature).
19

20
20
Compartimentazione

21

22

23
Es.

es.

29
1846

RUNAWAY (1)
effect
time 30

EFFECT
RUNAWAY
(2)
31

32
32
32
Connessione

Es.
33

34

35

36

37

Bad vs Good Collapse
STRUCTURE
& LOADS
Collapse
Mechanism
NO SWAY
“IMPLOSION”
OF THE
STRUCTURE
“EXPLOSION”
OF THE
STRUCTURE
is a process in which
objects are destroyed by
collapsing on themselves
is a process
NOT CONFINED
SWAY
38

39

40

41
WTC 7

Simulated exterior buckling of WTC 7 during the collapse.
42

Es.
43

44
Es.

45

46

47

Bad vs Good Collapse
STRUCTURE
& LOADS
Collapse
Mechanism
NO SWAY
“IMPLOSION”
OF THE
STRUCTURE
“EXPLOSION”
OF THE
STRUCTURE
is a process in which
objects are destroyed by
collapsing on themselves
is a process
NOT CONFINED
SWAY
48

• Capacity of a construction to show regular
decrease of its structural quality due to
negative causes.
• It implies:
a) some smoothness of the decrease of
structural performance due to negative
events (intensive feature);
b) some limited spatial spread of the
rupture (extensive feature).
49

50
ATTRIBUTES
RELIABILITY
AVAILABILITY
SAFETY
MAINTAINABILITY
INTEGRITY
SECURITY
FAILURE
ERROR
FAULT
permanent interruption of a system ability
to perform a required function
under specified operating conditions
the system is in an incorrect state:
it may or may not cause failure
it is a defect and represents a
potential cause of error, active or dormant
THREATS
NEGATIVE CAUSE
STRUCTURAL
QUALITY
more robust
less robust

Analisi
51

Levels of Structural Crisis
Usual
ULS
&
SLS
Verification
Format
Structural Robustness
Assessment
1st level:
Material
Point
2nd level:
Element
Section
3rd level:
Structural
Element
4th level:
Structural
System
52

Risposta strutturale
e formati di verifica
53

54
Materiale

55
Sezione

56
Momento–curvatura sezione

57
Elemento
SMEARED:
Plasticita’
diffusa
LUMPED:
Plasticita’
Concentrata
1

58
Momento–curvatura sezione: idealizzazione
2
1 2
+ = CERNIERA PLASTICA

59
1/ψ
Interazione M-N

60
Interazione M-N

61

62

63

64

65

66

67

68

69

Carico imposto
70

Carico / Spostamento imposto (1)
71

72

73

Push-over (1)
74

Push-down (1)
75

76
Es.

77

78

Applicazione
79

https://en.wikipedia.org/wiki/B-
25_Empire_State_Building_crash

http://galleryhip.com/plane-
crashes-into-empire-state-
building.html

https://en.wikipedia.org/wiki/2002_Pirelli
_Tower_airplane_crash

103
Esempio: edificio alto

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D0
Es.

D1 D2
Scenari (1-2)
106

D3 D4
Scenari (3-4)
107

Modalità di collasso (1-2)
D1 D2 108
108

Modalità di collasso (3-4)
D3 D4 109
109

0
4
Lo scenario D4
è quello più cattivo:
l’elemento strutturale
critico individuato è la
colonna più esterna!
110
Sintesi dei risultati: elemento critico
110

Modellazione edificio alto

Scenario 1
(1 asta
eliminata)
Scenario 2
(3 aste
eliminate)
Scenario 3
(5 aste
eliminate)
Scenario 4
(7 aste
eliminate)
Scenari di danneggiamento

Collasso secondo scenario 1

Moltiplicatore Ultimo e sua variazione
4,05
3,57
3,19
2,64 2,40
0,48
0,86
1,41 1,65
0,00
0,50
1,00
1,50
2,00
2,50
3,00
3,50
4,00
4,50
D0 D1 D2 D3 D4
Scenario di danneggiamento
u
Delta F
F
Sintesi dei risultati
Δ u
u

Design Strategy #1: CONTINUITY
119

Progetto
120

Design Strategy #1: CONTINUITY
121

Design Strategy #2: SEGMENTATION
PROGETTAZIONE STRUTTURALE
ANTINCENDIO

123
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Es.

124
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125
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126
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Es.

Stiffener, bulkhead & deck layout
129

Hull sections with and without
the outer hull
130

USS San Francisco after collision
with an underwater mountain
131

Es.

http://pressurevesseltech.as
medigitalcollection.asme.org
/article.aspx?articleid=16970
68#

Definizioni: compartimentazione
• CAPACITÀ DI COMPARTIMENTAZIONE IN CASO
D’INCENDIO: attitudine di un elemento costruttivo a
conservare, sotto l’azione del fuoco, oltre alla propria
stabilità, un sufficiente isolamento termico ed una
sufficiente tenuta ai fumi e ai gas caldi della
combustione, nonché tutte le altre prestazioni se
richieste.
• COMPARTIMENTO ANTINCENDIO: parte della
costruzione organizzata per rispondere alle esigenze
della sicurezza in caso di incendio e delimitata da
elementi costruttivi idonei a garantire, sotto l’azione del
fuoco e per un dato intervallo di tempo, la capacità di
compartimentazione.

Esempi
139

Es.

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.

Es.

https://californiawaterblog.com/2
016/05/01/the-collapse-of-water-
exports-los-angeles-1914/

Es.

http://urbanplanet.info/architecture/par
is-air-terminal-collapse-report-france/

Es.

http://www.wise-uranium.org/img/stavaa.gif

Es.

Bonus track
174

Es.

http://www.confederationbridge.com/ab
out/confederation-bridge/design.html

https://www.tuhh.de/sdb/starossek/Ver
oeffentlichungen/Dateien/Progressive%2
0collapse%20of%20bridges%20(Uwe%20
Starossek).pdf

Es.

1) Minimum number of removed hangers and most sensitive location for
the triggering of the progressive collapse: the bridge results to be more
sensible to the damage at mid-span, where the removal of just 5 hanger
for the symmetrical rupture and 7 hangers for the asymmetrical rupture is
needed in order to trigger the collapse propagation.
Shifting the initial damage location aside (about at 1/3 of the span) the
asymmetrical rupture of 9 hangers is required for the collapse propagation,
while moving the initial damage near the tower even the asymmetrical
removal of 12 hangers has no global effects on the structure and very 7
hangers must be symmetrically removed on both sides in order to trigger
the propagation of the ruptures on the adjoining hangers.

2) Preferential direction for the collapse propagation: to the higher damage sensibility of
the bridge central zone counterpoises a lower acceleration of the collapse progression
triggered by central ruptures, with respect to that one triggered by lateral ruptures.
This effect is due to the particular configuration of the structural system that requires a
growing hanger length from the centre to the sides of the bridge: when a chain rupture
trigger, the ultimate elongation required to the hangers adjoining the failed ones increases
as the collapse propagates (because the unsupported deck length also increases).
If the initial damage occurs at mid-span, it involves the shortest hangers and the collapse
propagation is partially slowed down from the growing element ductility of sideward
hangers. On the contrary, a more intense initial damage is required sideways to trigger
chain ruptures, but then the hanger breakdowns speeds up when moving toward the
centre, where the hanger length decreases.

3) Qualitative measure that could possibly lead the collapse to an halt: in the case of a
central rupture a closer increment in the section of the hangers (that remain instead the
same for about 5/6 of the span length) could possibly provide for a collapse standstill. In
the case of a chain rupture triggered in a lateral zone the preferential direction showed by
the progressive collapse would probably make less effective such a measure.
3) Qualitative measure that could possibly lead the collapse to an halt: in the case of a
central rupture a closer increment in the section of the hangers (that remain instead the
same for about 5/6 of the span length) could possibly provide for a collapse standstill. In
the case of a chain rupture triggered in a lateral zone the preferential direction showed
by the progressive collapse would probably make less effective such a measure.

4) Sensibility to modality of damage (asymmetrical or symmetrical failure): another
consideration about the possible collapse standstill concerns the higher susceptibility of
the bridge to an unsymmetrical hanger failure than to a symmetrical one: in the last case
the symmetrical hinge formations determines a symmetrical moment increment on the
deck box-girders, thus possibly allowing for an early deck segment detachment that would
arrest the collapse
4) Sensibility to modality of damage (asymmetrical or
symmetrical failure): another consideration about the
possible collapse standstill concerns the higher susceptibility
of the bridge to an unsymmetrical hanger failure than to a
symmetrical one: in the last case the symmetrical hinge
formations determines a symmetrical moment increment
on the deck box-girders, thus possibly allowing for an early
deck segment detachment that would arrest the collapse

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Bonus track
202

HUMAN ERROR

100%
Time
%
of
failure
Unknown phenomena
Known phenomena
Research level Design code level
past present future
A
B
B B
C
Human
errors
Causes of System Failure

Errors by Reason
conoscenza
valutazione
scelta
decisione
esecuzione

conoscenza
valutazione
scelta
decisione
esecuzione

Factors (1)

Factors (2)

Errors by Rasmussen

Eccesso di Norme Tecniche
• «Ma un numero di regole eccessivo comporta vari degli
inconvenienti dianzi citati e in particolare:
- l'impoverimento dell'autonomia e della creatività, in
quanto l'opera del progettista è irretita dalle norme;
- la difficoltà di discernere ciò che veramente conta;
- la sensazione di avere, al riparo delle norme,
responsabilità assai alleviate;
- la difficoltà non infrequente di rendersi conto dei
ragionamenti che giustificano certe regole, rischiando
di considerare queste alla stregua di algoritmi, ossia di
schemi operativi che, una volta appresi, il pensiero non
è più chiamato a giustificare.»
- Proliferazione delle normative e tecnicismo. Ultima lezione ufficiale del corso di Tecnica delle costruzioni tenuta dal prof. Piero Pozzati
- nell'a.a. 1991-'92, presso la Facoltà di Ingegneria dell'Università di Bologna (3 giugno 1992).

Sharp Criteria vs. Fuzzy Criteria

The effect of context

Judgement Errors
• 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
• Nonregressive prediction
• Synchronicity
• Causalation
• Salience
• Minority influence
• Groupthink

MANAGING
THE UNEXPECTED

Unexpected events

Brutal audit
• The ability to deal with a crisis is largely dependent
on the structures that have been developed before
chaos arrives.
• The event can in some ways be considered as an
abrupt and brutal audit: at a moment’s notice,
everything that was left unprepared becomes a
complex problem, and every weakness comes
rushing to the forefront.

Small events
• Small events have large consequences.
• Small discrepancies give off small clues that are hard to
spot but easy to treat if they are spotted.
• When clues become much more visible, they are that
much harder to treat.
• Managing the unexpected often means that people
have to make strong responses to weak signals,
something that is counterintuitive and not very heroic.
• Normally, we make weak responses to weak signals and
strong responses to strong signals.

Sensitivity to initial conditions

Butterfly Effect
• The meteorologist Edward Lorenz discovered that a
simple model of heat convection possesses intrinsic
unpredictability, a circumstance he called the
“butterfly effect,” suggesting that the mere flapping
of a butterfly’s wing can change the weather.
• A more homely example is the pinball machine: the
ball’s movements are precisely governed by laws of
gravitational rolling and elastic collisions—both
fully understood—yet the final outcome is
unpredictable.

Chaos Theory (1)
• Chaos theory concerns deterministic systems whose
behavior can in principle be predicted. Chaotic systems
are predictable for a while and then 'appear' to become
random.
• The amount of time that the behavior of a chaotic
system can be effectively predicted depends on three
things:
❑how much uncertainty can be tolerated in the forecast,
❑how accurately its current state can be measured,
❑and a time scale depending on the dynamics of the
system, called the Lyapunov time.

Chaos Theory (2)
• In chaotic systems, the uncertainty in a forecast
increases exponentially with elapsed time. Hence,
mathematically, doubling the forecast time more
than squares the proportional uncertainty in the
forecast. This means, in practice, a meaningful
prediction cannot be made over an interval of more
than two or three times the Lyapunov time.
• When meaningful predictions cannot be made, the
system appears random.

http://abyss.uoregon.edu/~js/21st_century_science/lectures/lec08.html

Authorities vs Experts
• Systems that mismanage the unexpected tend to
ignore small failures, accept simple diagnoses, take
frontline operations for granted, neglect
capabilities for resilience, and defer to authorities
rather than experts

How to handle unexpected events
1. Tracks small failures
2. Resists oversimplification
3. Remains sensitive to operations
4. Maintains capabilities for resilience
5. Takes advantage of shifting locations of
expertise

HRO

High Reliability Organization (HRO)
• A high reliability organization (HRO) is an organization
that has succeeded in avoiding catastrophes in an
environment where normal accidents can be expected
due to risk factors and complexity.
• Important case studies in HRO research include both
studies of disasters (e.g., Three Mile Island nuclear
incident, the Challenger explosion and Columbia
explosion, the Bhopal chemical leak, the Tenerife air
crash, the Mann Gulch forest fire, the Black Hawk
friendly fire incident in Iraq) and cases like the air traffic
control system, naval aircraft carriers, and nuclear
power operations.

2 - Resists
oversimplification
3 - Remains sensitive to operations
5 - Takes advantage of
shifting locations of
expertise
4 - Maintains capabilities for
resilience
1 - Tracks small failures

Mindfulness (1)
• Mindfulness – a rich awareness of discriminatory
detail and an enhanced ability to discover and
correct errors that could escalate into a crisis.
• By mindful, one also means striving to maintain an
underlying style of mental functioning that is
distinguished by continuous updating and
deepening of increasingly plausible interpretations
of the context, what problems define it, and what
remedies it contains.

Mindfulness (2)
• The big difference between functioning in HROs
and in other organizations is often most evident in
the early stages when the unexpected gives off only
weak signals of trouble.
• The overwhelming tendency is to respond to weak
signals with a weak response. Mindfulness
preserves the capability to see the significance of
weak signals and to respond vigorously.

Mindfulness Defined
1. combination of ongoing scrutiny of existing
expectations,
2. continuous refinement and differentiation of
expectations based on newer experiences,
3. willingness and capability to invent new expectations
that make sense of unprecedented events,
4. a more nuanced appreciation of context and ways to
deal with it,
5. and identification of new dimensions of context that
improve foresight and current functioning.

Detection, Containment,
Resilience
• One attributes the success of HROs in managing the
unexpected to their determined efforts to act
mindfully.
1) By this one means that they organize themselves in
such a way that they are better able to notice the
unexpected in the making and halt its development.
2) If they have difficulty halting the development of the
unexpected, they focus on containing it.
3) And if the unexpected breaks through the
containment, they focus on resilience and swift
restoration of system functioning.

Resilience
• To be resilient is to be mindful about errors that
have already occurred and to correct them before
they worsen and cause more serious harm.
• Resilience encourages people to act while thinking
or to act in order to think more clearly.
• Resilience is about bouncing back from errors and
about coping with surprises in the moment.
• Achieved through an extensive action repertoire
and skills with improvisation.

Note
• Mindfulness also involves preferences that are diverse; close
attention to situations; resilience in the face of events;
sensemaking that shows whether a decision is necessary;
people with diverse interests who debate, speak up, and
listen to one another; and designs that are malleable rather
than fixed.
• When you try to move toward mindfulness, there is
resistance, partly because of threats to psychology safety.
• After all, it’s a whole lot easier to bask in success, keep it
simple, follow routines, avoid trouble, and do an adequate
job. I know how to do those things. But dwell on failure?
Question my assumptions? Linger over details? Fight fires
creatively? Ask for help? No thanks. Or more likely, “You
first!”

Mindlessness (1)
• When people function mindlessly, they don’t
understand either themselves or their
environments, but they feel as though they do.
• A silent contributor to mindlessness is the zeal
found in most firms for planning. Plans act the
same way as expectations. They guide people to
search narrowly for confirmation that the plan is
correct.
• Mindlessness is more likely when people are
distracted, hurried, or overloaded.

Mindlessness (2)
• A tendency toward mindlessness is characterized by a style
of mental functioning in which people follow recipes,
impose old categories to classify what they see, act with
some rigidity, operate on automatic pilot, and mislabel
unfamiliar new contexts as familiar old ones.
• A mindless mental style works to conceal problems that are
worsening.

Mindless Control Systems
• It is impossible to manage any organization solely
by means of mindless control systems that depend
on rules, plans, routines, stable categories, and
fixed criteria for correct performance.
• No one knows enough to design such a system so
that it can cope with a dynamic environment.
• Instead, designers who want to hold dynamic
systems together must organize in ways that evoke
mindful work.

Plans, visions and forecast
• Plans and visions and forecasts are inaccurate and gain
much of their power from efforts to avoid disconfirmation.
• You’ll also discover that plans and visions and forecasts
create blind spots.
• Corrections to those inaccuracies lie in the hands of those
who have a deeper grasp of how things really work. And
that grasp comes from mindfulness.
• People who act mindfully notice and pursue that rich,
neglected remainder of information that mindless actors
leave unnoticed and untouched. Mindful people hold
complex projects together because they understand what is
happening.

Mindless/Mindful Investments
• To manage the unexpected is to be reliably mindful,
not reliably mindless.
• Obvious as that may sound, those who invest
heavily in plans, standard operating procedures,
protocols, recipes, and routines tend to invest more
heavily in mindlessness than in mindfulness.

John Boyd

Principles of HRO

HRO Principle 1:
Preoccupation with failure.
• HROs are distinctive because they are preoccupied
with failure.
• They treat any lapse as a symptom that something
may be wrong with the system, something that
could have severe consequences if several separate
small errors happened to coincide.

Note
• HROs encourage reporting of errors, they elaborate
experiences of a near miss for what can be learned,
and they are wary of the potential liabilities of
success, including complacency, the temptation to
reduce margins of safety, and the drift into
automatic processing.
• They also make a continuing effort to articulate
mistakes they don’t want to make and assess the
likelihood that strategies increase the risk of
triggering these mistakes.

HRO Principle 2:
Reluctance to simplify.
• Another way HROs manage for the unexpected is by
being reluctant to accept simplifications.
• It is certainly true that success in any coordinated
activity requires that people simplify in order to stay
focused on a handful of key issues and key indicators.
But it is also true that less simplification allows you to
see more. HROs take deliberate steps to create more
complete and nuanced pictures of what they face and
who they are as they face it.

Note
• Knowing that the world they face is complex, unstable,
unknowable, and unpredictable, HROs position themselves
to see as much as possible.
• They welcome diverse experience, skepticism toward
received wisdom, and negotiating tactics that reconcile
differences of opinion without destroying the nuances that
diverse people detect.
• When they “recognize” an event as something they have
experienced before and understood, that recognition is a
source of concern rather than comfort. The concern is that
superficial similarities between the present and the past
mask deeper differences that could prove fatal.

HRO Principle 3:
Sensitivity to operations.
• HROs are sensitive to operations.
• They are attentive to the front line, where the real
work gets done. The “big picture” in HROs is less
strategic and more situational than is true of most
other organizations.
• When people have well-developed situational
awareness, they can make the continuous
adjustments that prevent errors from accumulating
and enlarging.

Note
• Anomalies are noticed while they are still tractable
and can still be isolated.
• All of this is made possible because HROs are aware
of the close ties between sensitivity to operations
and sensitivity to relationships.
• People who refuse to speak up out of fear
undermine the system, which knows less than it
needs to know to work effectively.
• People in HROs know that you can’t develop a big
picture of operations if the symptoms of those
operations are withheld.

HRO Principle 4:
Commitment to resilience.
• No system is perfect. HROs know this as well as
anyone.
• This is why they complement their anticipatory
activities of learning from failure, complicating their
perceptions, and remaining sensitive to operations
with a commitment to resilience.

Note
• The essence of resilience is therefore the intrinsic
ability of an organization (system) to maintain or
regain a dynamically stable state, which allows it to
continue operations after a major mishap and/or in
the presence of a continuous stress.
• HROs develop capabilities to detect, contain, and
bounce back from those inevitable errors that are
part of an indeterminate world.
• The hallmark of an HRO is not that it is error-free
but that errors don’t disable it.

Note
• Resilience is a combination of keeping errors small
and of improvising workarounds that allow the
system to keep functioning.
• Both pathways to resilience demand deep
knowledge of the technology, the system, one’s
coworkers, and most of all, oneself.
• HROs put a premium on training, personnel with
deep and varied experience, and skills of
recombination and making do with whatever is at
hand. They imagine worst-case conditions and
practice their own equivalent of fire drills.

HRO Principle 5:
Deference to Expertise.
• HROs is deferent to expertise.
• HROs cultivate diversity, not just because it helps
them notice more in complex environments, but also
because it helps them do more with the complexities.
• Rigid hierarchies have their own special vulnerability
to error. Errors at higher levels tend to pick up and
combine with errors at lower levels, thereby making
the resulting problem bigger, harder to comprehend,
and more prone to escalation.

Note
• Decisions are made on the front line, and authority
migrates to the people with the most expertise,
regardless of their rank. This is not simply a case of
people deferring to the person with the “most
experience.”
• Experience by itself is no guarantee of expertise, since
all too often people have the same experience over and
over and do little to elaborate those repetitions. The
pattern of decisions “migrating” to expertise is found in
flight operations on aircraft carriers, where
“uniqueness coupled with the need for accurate
decisions leads to decisions that ‘search’ for the expert
and migrate around the organization.

People

Error is pervasive.
The unexpected is pervasive.
• Nowhere one finds any mention of perfection, zero
errors, flawless performance, or infallible humans.
• Error is pervasive.
• The unexpected is pervasive.
• By now that message should be clear. What is not
pervasive are well-developed skills to detect and
contain these errors at their early stages.

Expectations (1)
• The basic argument is that expectations are built
into organizational roles, routines, and strategies.
These expectations create the orderliness and
predictability that count on when one organizes.
• Expectations, however, are a mixed blessing
because they create blind spots.
• Blind spots sometimes take the form of belated
recognition of unexpected threatening events. And
frequently blind spots get larger simply because
one does a biased search for evidence that
confirms the accuracy of original expectations.

Expectations (2)
• To have an expectation is to envision something, usually for
good reasons, that is reasonably certain to come about.
• To expect something is to be mentally ready for it. Every
deliberate action you take is based on assumptions about
how the world will react to what you do.
• Expectancies form the basis for virtually all deliberate
actions because expectancies about how the world operates
serve as implicit assumptions that guide behavioral choices.
• Expectations provide a significant infrastructure for
everyday life. They are like a planning function that suggests
the likely course of events…

Blind spots
• The problem with blind spots is that they often conceal
small errors that are getting bigger and can produce
disabling brutal audits.
• To counteract these blind spots, organizations try to develop
a greater awareness of discriminatory detail.
• This enriched awareness, which we call mindfulness,
uncovers early signs that expectations are inadequate, that
unexpected events are unfolding, and that recovery needs
to be implemented.
• Recovery requires updating both of one’s understanding of
what is happening and of the lines of action that were tied
to the earlier expectations.

Detection / Not Error-Free
• It is the failure both to articulate important mistakes that
must not occur and to organize in order to detect them that
allows unexpected events to spin out of control.
• HROs develop capabilities to detect, contain, and bounce
back from those inevitable errors that are part of an
indeterminate world.
• The signature of an HRO is not that it is error-free, but that
errors don’t disable it.
• Resilience is a combination of keeping errors small and of
improvising workarounds that keep the system functioning.

Error Reporting
• A necessary component of an incident review is the
reporting of an incident. And research shows that
people need to feel safe to report incidents or they
will ignore them or cover them up.
• HROs increase their knowledge base by
encouraging and rewarding error reporting.

Assumptions
• Every deliberate action you take is based on
assumptions about how the world will react to what
you do.
• Expectancies form the basis for virtually all deliberate
actions because expectancies about how the world
operates serve as implicit assumptions that guide
behavioral choices.
• Expectations provide a significant infrastructure for
everyday life. They are like a routine that suggests the
probable course of events. They direct your attention
to certain features of events, which means that they
affect what you notice, mull over, and remember. When
you expect that something will happen, that is a lot like
testing a hypothesis.

Self-fulfilling prophecy (1)
• A self-fulfilling prophecy is the sociopsychological
phenomenon of someone "predicting" or expecting
something, and this "prediction" or expectation coming
true simply because the person believes it will and the
person's resulting behaviors aligning to fulfill the belief.
• This suggests that people's beliefs influence their
actions.
• The principle behind this phenomenon is that people
create consequences regarding people or events, based
on previous knowledge of the subject.
• A self-fulfilling prophecy is applicable to either negative
or positive outcomes.

Self-fulfilling prophecy (2)
• American sociologist William Isaac Thomas was the first
to discover this phenomenon. In 1928 he developed
the Thomas theorem (also known as the Thomas
dictum), stating that,
If men define situations as real,
they are real in their consequences.
• In other words, the consequence will come to fruition
based on how one interprets the situation. Using
Thomas' idea, another American sociologist, Robert K.
Merton, coined the term "self-fulfilling prophecy",
popularizing the idea that “a belief or expectation,
correct or incorrect, could bring about a desired or
expected outcome.”

Note
• Self-fulfilling theory can be divided into two behaviors, one would be
the Pygmalion effect which is when “one person has expectations of
another, changes her behavior in accordance with these expectations,
and the object of the expectations then also changes her behavior as a
result.”
• Additionally, philosopher Karl Popper called the self-fulfilling prophecy
the Oedipus effect:
• One of the ideas I had discussed in The Poverty of Historicism was the
influence of a prediction upon the event predicted. I had called this the
"Oedipus effect", because the oracle played a most important role in the
sequence of events which led to the fulfilment of its prophecy. [...] For a
time I thought that the existence of the Oedipus effect distinguished the
social from the natural sciences. But in biology, too—even in molecular
biology—expectations often play a role in bringing about what has been
expected.
• An early precursor of the concept appears in Edward Gibbon’s Decline
and Fall of the Roman Empire: "During many ages, the prediction, as it is
usual, contributed to its own accomplishment" (chapter I, part II).

Confirmations
• Many of expectations are reasonably accurate.
They tend to be confirmed, partly because they are
based on experience and partly because one
corrects those that have negative consequences.
• The tricky part is that all of us tend to be awfully
generous in what we accept as evidence that our
expectations are confirmed.
• Furthermore, we actively seek out evidence that
confirms our expectations and avoid evidence that
disconfirms them.

Unpleasant Feelings
• Evidence shows that when something unexpected
happens, this is an unpleasant experience. Part of
managing the unexpected involves anticipating
these feelings of unpleasantness and taking steps
to minimize their impact.

Cognitive dissonance
• A person who experiences internal inconsistency tends to
become psychologically uncomfortable and is motivated to
reduce the cognitive dissonance. They tend to make
changes to justify the stressful behavior, either by adding
new parts to the cognition causing the psychological
dissonance or by avoiding circumstances and contradictory
information likely to increase the magnitude of the cognitive
dissonance.
• Coping with the nuances of contradictory ideas or
experiences is mentally stressful. It requires energy and
effort to sit with those seemingly opposite things that all
seem true. Festinger argued that some people would
inevitably resolve dissonance by blindly believing whatever
they wanted to believe.

Routines and planes
• People also search for confirmation in other forms
of expecting such as routines and plans.
• Organizations often presume that because they
have routines to deal with problems, this proves
that they understand those problems.
• Although there is a grain of truth to that inference,
what they fail to see is that their routines are also
expectations that are subject to the very same
traps as any other expectations.

Kahneman and Tversky
• We actively seek out evidence that confirms our
expectations and avoid evidence that disconfirms
them.
• We tend to overestimate the validity of
expectations currently held.
• The continuing search for confirming evidence
postpones your realization that something
unexpected is developing.

Updating
• Whenever a routine is activated, people assume
that the world today is pretty much like the world
that existed at the time the routine was first
learned.
• Furthermore, people tend to look for confirmation
that their existing routines are correct. And over
time, they come to see more and more
confirmation based on fewer and fewer data.
• What is missing are continuing efforts to update
the routines and expectations and to act in ways
that would compel such updating.

Plans
• This same pattern of confirmation seeking is
associated with plans.
• Plans guide people to search narrowly for
confirmation that the plans are correct.
• Disconfirming evidence is avoided, and plans lure
you into overlooking a buildup of the unexpected.
• This is not surprising since much of the imagery
used to describe plans is like the imagery people
use when they talk about expectations.

Counteract to seek confirmation
• People in HROs work hard to counteract the
tendency to seek confirmation by designing
practices that incorporate the five principles.
• They understand that their expectations are
incomplete and that they can come closer to
getting it right if they doubt those expectations that
seem to be confirmed most often.

Alertness
• The tendencies to seek confirmation and avoid
disconfirmation are well-honed, well-practiced
human tendencies.
• That’s why HROs have to work so hard and so
continuously to override these tendencies and
remain alert. And that’s why you may have to work
just as hard.
• All of us face an ongoing struggle for alertness
because we face an ongoing preference for
information that confirms.

Expectations and Planning
• If you understand the problems that expectations
create, you understand the problems that plans
create. And you may begin to understand why a
preoccupation with plans and planning makes it
that much harder for you to act mindfully.
• By contrast, mindfulness is essentially a
preoccupation with updating. It is grounded in an
understanding that knowledge and ignorance grow
together.

Redirecting Attention
• The power of a mindful orientation is that it
redirects attention from the expected to the
irrelevant, from the confirming to the
disconfirming, from the pleasant to the unpleasant,
from the more certain to the less certain, from the
explicit to the implicit, from the factual to the
probable, and from the consensual to the
contested.

Believing is Seeing
• Trouble starts when I fail to notice that I see only
whatever confirms my categories and expectations
but nothing else. The trouble deepens even further
if I kid myself that seeing is believing. That’s wrong.
It’s the other way around. Believing is seeing. You
see what you expect to see. You see what you have
the labels to see. You see what you have the skills
to manage.

L'occhio vede solo ciò
che la mente è preparata
a comprendere
(Henri Bergson)
Henri-Louis Bergson (Parigi, 18 ottobre 1859 – Parigi, 4 gennaio 1941) è stato un filosofo francese. La sua opera superò le tradizioni ottocentesche dello Spiritualismo
e del Positivismo ed ebbe una forte influenza nei campi della psicologia, della biologia, dell'arte, della letteratura e della teologia. Fu insignito del Premio Nobel per la
letteratura nel 1927 sia «per le sue ricche e feconde idee» sia «per la brillante abilità con cui ha saputo presentarle».
Occhio clinico

Forms of unexpected
I. The first form of the unexpected occurs when an
event that was expected to happen fails to occur.
II. A second form of the unexpected occurs when an
event that was not expected to happen does
happen.
III. The third form of the unexpected occurs when an
event that was simply unthought of happens.

Start
• In each of these three cases, the surprise starts with an
expectation.
• Presumably, if you hold these expectations, you look for
evidence that confirms them rather than evidence that
disconfirms them.
• If you find confirming evidence, this “proves” that your
hunches about the world are accurate, that you are in
control, that you know what’s up, and that you are
safe.
• The continuing search for confirming evidence
postpones your realization that your model has its
limits.

Finally
• If you are slow to realize that things are not the way
you expected them to be, the problem worsens and
becomes harder to solve and gets entangled with other
problems.
• When it finally becomes clear that your expectation is
wrong, there may be few options left to resolve the
problem.
• In the meantime, efficiency and effectiveness have
declined, the system is now vulnerable to further
collapse, and safety, reputations, and production are in
jeopardy.

Imaginations
• A significant goal of HROs is to increase their understanding
of the third form of the unexpected and to expand
knowledge of “the imagined deemed possible.”
• HRO principles steer people toward mindful practices that
encourage imagination.
• The crucial nature of imagination is reflected in the report
of the commission investigating the terrorist attacks on
September 11, 2001. It found shortfalls in imagination prior
to the collapse of the twin towers.

WTC
• The commission’s report contains this striking
assertion:
“Imagination is not a gift usually associated with
bureaucracies. ... It is therefore crucial to find a way
of routinizing, even bureaucratizing the exercise of
imagination. Doing so requires more than finding an
expert who can imagine that aircraft could be used
as weapons.”

Alertness
• It takes more than a shrewd expert to forestall the
unexpected in most situations.
• It takes mindful practices that encourage
imagination, foster enriched expectations, raise
doubts about all expectations, increase the ability
to make novel sense of small interruptions in
expectations, and facilitate learning that intensifies
and deepens alertness.

Trivialize
• People sometimes inadvertently trivialize the
importance of imagination. For example, these days
we keep hearing the hollow maxim “Expect the
unexpected.” That well-meaning sentiment
assumes that people can live their lives while
assuming that their expectations are misleading.
• The problem is, they can’t afford to. They live,
instead, as if their expectations are basically correct
and as if there is little that can surprise them. To do
otherwise would be to forgo any feeling of control
or predictability.

Virginity
• Once you’ve accepted an anomaly or something
less than perfect, you know, you’ve given up your
virginity. You can’t go back. You’re at the point that
it’s very hard to draw the line. You know, next time
they say it’s the same problem, it’s just eroded 5
mils more. Once you accepted it, where do you
draw the line? Once you’ve done it, it’s very
difficult to go back now and get very hard-nosed
and say I’m not going to accept that.

Leemers
• You’ll probably know when something unexpected happens
because you’ll feel surprised, puzzled, or anxious. Aviators
call these feelings leemers (probably derived from leery),
the feeling that something is not quite right, but you can’t
put your finger on it. Trust those feelings. They are a solid
clue that your model of the world is in error.
• More important, try to hold on to those feelings and resist
the temptation to gloss over what has just happened and
treat it as normal. In that brief interval between surprise
and successful normalizing lies one of your few
opportunities to discover what you don’t know.

Learning moment
• This is one of those rare moments when you can
significantly improve your understanding.
• If you wait too long, normalizing will take over, and
you’ll be convinced that there is nothing to learn.
• Most opportunities for learning come in the form
of brief moments.
• And one of the best moments for learning, a
moment of the unexpected, is also one of the
shortest-lived moments.

Sustained High Performance
• If you update and differentiate the labels you
impose on the world, the unexpected will be
spotted earlier and dealt with more fully, and
sustained high performance will be more assured.
• Reliability is a dynamic event and gets
compromised by distraction and ignorance.
• Mindfulness is about staying attuned to what is
happening and about a deepening grasp of what
those events mean.

Culture

Importance of Doctrine
• When you think about mindful culture as a means to
manage the unexpected, keep the following picture of
culture in front of you.
• Culture is about the assumptions that influence the people
who manage the unexpected. Culture can hold large
systems together. Culture is unspoken, implicit, taken for
granted. You feel culture when what you do feels
appropriate or inappropriate. You feel the unexpected when
something surprises you.
• Culture produces simultaneous centralization-
decentralization by binding people to a small set of core
values and allowing them discretion over everything else.

Churchill’s Audit
• Why didn’t I know?
• Why didn’t my advisors
know?
• Why wasn’t I told?
• Why didn’t I ask?
• Perché non lo sapevo?
• Perché i miei consulenti
non lo sapevano?
• Perché non me l'hanno
detto?
• Perché non l'ho
chiesto?

Culture
• Culture is a pattern of shared beliefs and
expectations that shape how individuals and groups
act.
• Descriptions of safety culture often read like lists of
banal injunctions to “do good.”
• Culture will affect what you see and how you
interpret it.
• Culture change takes a long time.

Culture - Schein
• Culture is defined by six formal properties:
(1) shared basic assumptions that are
(2) invented, discovered, or developed by a given group as it
(3) learns to cope with its problem of external adaptation and
internal integration in ways that
(4) have worked well enough to be considered valid and,
therefore,
(5) can be taught to new members of the group as the
(6) correct way to perceive, think, and feel in relation to those
problems.

Building on strengths
• Never start with the idea of changing culture.
• Try to build on existing cultural strengths rather
than attempting to change those elements that
may be weaknesses.

Four Subcultures
• The problem is that candid reporting of errors takes trust
and trustworthiness. Both are hard to develop, easy to
destroy, and hard to institutionalize.
1. Reporting Culture
2. Just Culture
3. Flexible Culture
4. Learning Culture
James Reason

Reason (James)
• Reason (James) argues that it takes four subcultures to
ensure an informed culture. Assumptions, values, and
artifacts must line up consistently around the issues of
1. What gets reported when people make errors or
experience near misses (reporting culture)
2. How people apportion blame when something goes wrong
(just culture)
3. How readily people can adapt to sudden and radical
increments in pressure, pacing, and intensity (flexible
culture)
4. How adequately people can convert the lessons that they
have learned into reconfigurations of assumptions,
frameworks, and action (learning culture).

1 - Reporting Culture
• Since safety cultures are dependent on the
knowledge gained from rare incidents, mistakes,
near misses, and other “free lessons,” they need to
be structured so that people feel willing to
“confess” their own errors.
• A reporting culture is about protection of people
who report.
• It is also about what kinds of reports are trusted.

2 - Just Culture
• An organization is defined by how it handles blame
and punishment, and that in turn can affect what
gets reported in the first place.

3 - Flexible Culture
• Adapts to changing demands
• Deference to expertise – decisions migrate to
expertise during periods of high-tempo activity
• Collect multiple signals from a variety of sources
• HROs assume that the system is endangered until
there is conclusive proof that it is not

4 - Learning Culture
• An informed culture learns by means of ongoing
debates about constantly shifting discrepancies. These
debates promote learning because they identify new
sources of hazard and danger and new ways to cope.
• Culture shapes actions largely without people being
aware of how little they see and how many options
they overlook.
• When people are drawn into a culture that is partly of
their own making, it is very hard for them to see that
what they take for granted hides the beginnings of
trouble.

Mindful Culture
• To be mindful is to become susceptible to learning
anxiety. And anxious people need what Edgar
Schein calls “psychological safety.”
• Mindfulness requires continuous ongoing activity.
• We are not talking about a “safety war” that ends
in victory. We are talking instead about an endless
guerilla conflict.

Progettazione Strutturale Antincendio: Robustezza Strutturale

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