Progettazione Strutturale Antincendio. ROBUSTEZZA

Progettazione Strutturale Antincendio. ROBUSTEZZA
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? 17/03/2023 PSA - Robustezza Strutturale 2
17/03/2023 PSA - Robustezza Strutturale 3
17/03/2023 6 PSA - Robustezza Strutturale
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. 17/03/2023 10 PSA - Robustezza Strutturale
1 0 2 3 17/03/2023 11 PSA - Robustezza Strutturale
Requisiti 12 17/03/2023 PSA - Robustezza Strutturale
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 17/03/2023 PSA - Robustezza Strutturale
Robustezza / Durabilita’ 14 17/03/2023 PSA - Robustezza Strutturale
RESILIENCE 15 17/03/2023 PSA - Robustezza Strutturale
Definizioni 16 17/03/2023 PSA - Robustezza Strutturale
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 17/03/2023 PSA - Robustezza Strutturale
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 17/03/2023 PSA - Robustezza Strutturale
• 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 Structural Robustness (2) 17/03/2023 PSA - Robustezza Strutturale
20 20 Compartimentazione 17/03/2023 PSA - Robustezza Strutturale
21 17/03/2023 PSA - Robustezza Strutturale
23 Es. 17/03/2023 PSA - Robustezza Strutturale
17/03/2023 PSA - Robustezza Strutturale 24 es.
29 1846 17/03/2023 PSA - Robustezza Strutturale
RUNAWAY (1) effect time 30 17/03/2023 PSA - Robustezza Strutturale
EFFECT RUNAWAY (2) 31 17/03/2023 PSA - Robustezza Strutturale
32 32 32 Connessione 17/03/2023 PSA - Robustezza Strutturale
Es. 33 17/03/2023 PSA - Robustezza Strutturale
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 17/03/2023 PSA - Robustezza Strutturale
41 WTC 7 17/03/2023 PSA - Robustezza Strutturale
Simulated exterior buckling of WTC 7 during the collapse. 42 17/03/2023 PSA - Robustezza Strutturale
Es. 43 17/03/2023 PSA - Robustezza Strutturale
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 17/03/2023 PSA - Robustezza Strutturale
• 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 Structural Robustness (2) 17/03/2023 PSA - Robustezza Strutturale
50 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 17/03/2023 PSA - Robustezza Strutturale
Analisi 51 17/03/2023 PSA - Robustezza Strutturale
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 17/03/2023 PSA - Robustezza Strutturale
Risposta strutturale e formati di verifica 53 17/03/2023 PSA - Robustezza Strutturale
54 Materiale 17/03/2023 PSA - Robustezza Strutturale
55 Sezione 17/03/2023 PSA - Robustezza Strutturale
56 Momento–curvatura sezione 17/03/2023 PSA - Robustezza Strutturale
57 Elemento SMEARED: Plasticita’ diffusa LUMPED: Plasticita’ Concentrata 1 17/03/2023 PSA - Robustezza Strutturale
58 Momento–curvatura sezione: idealizzazione 2 1 2 + = CERNIERA PLASTICA 17/03/2023 PSA - Robustezza Strutturale
59 1/ψ Interazione M-N 17/03/2023 PSA - Robustezza Strutturale
60 Interazione M-N 17/03/2023 PSA - Robustezza Strutturale
Carico imposto 70 17/03/2023 PSA - Robustezza Strutturale
Carico / Spostamento imposto (1) 71 17/03/2023 PSA - Robustezza Strutturale
Push-over (1) 74 17/03/2023 PSA - Robustezza Strutturale
Push-down (1) 75 17/03/2023 PSA - Robustezza Strutturale
Applicazione 79 17/03/2023 PSA - Robustezza Strutturale
https://en.wikipedia.org/wiki/B- 25_Empire_State_Building_crash 17/03/2023 PSA - Robustezza Strutturale 80
http://galleryhip.com/plane- crashes-into-empire-state- building.html 17/03/2023 PSA - Robustezza Strutturale 81
https://en.wikipedia.org/wiki/2002_Pirelli _Tower_airplane_crash 17/03/2023 PSA - Robustezza Strutturale 97
103 Esempio: edificio alto 17/03/2023 PSA - Robustezza Strutturale 103
PSA - Robustezza Strutturale 104 17/03/2023
D0 Es. 17/03/2023 PSA - Robustezza Strutturale 105
D1 D2 Scenari (1-2) 106 17/03/2023 PSA - Robustezza Strutturale
D3 D4 Scenari (3-4) 107 17/03/2023 PSA - Robustezza Strutturale
Modalità di collasso (1-2) D1 D2 108 108 17/03/2023 PSA - Robustezza Strutturale
Modalità di collasso (3-4) D3 D4 109 109 17/03/2023 PSA - Robustezza Strutturale
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 17/03/2023 PSA - Robustezza Strutturale
Modellazione edificio alto 17/03/2023 PSA - Robustezza Strutturale 111
Scenario 1 (1 asta eliminata) Scenario 2 (3 aste eliminate) Scenario 3 (5 aste eliminate) Scenario 4 (7 aste eliminate) Scenari di danneggiamento 17/03/2023 PSA - Robustezza Strutturale 113
Collasso secondo scenario 1 17/03/2023 PSA - Robustezza Strutturale 114
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 17/03/2023 PSA - Robustezza Strutturale 118
Design Strategy #1: CONTINUITY 119 17/03/2023 PSA - Robustezza Strutturale
Progetto 120 17/03/2023 PSA - Robustezza Strutturale
Design Strategy #1: CONTINUITY 121 17/03/2023 PSA - Robustezza Strutturale
Design Strategy #2: SEGMENTATION PROGETTAZIONE STRUTTURALE ANTINCENDIO 17/03/2023 PSA - Robustezza Strutturale 122
123 PSA - Robustezza Strutturale 123 17/03/2023 Es.
124 PSA - Robustezza Strutturale 124 17/03/2023
Es. 17/03/2023 PSA - Robustezza Strutturale 128
Stiffener, bulkhead & deck layout 129 17/03/2023 PSA - Robustezza Strutturale
Hull sections with and without the outer hull 130 17/03/2023 PSA - Robustezza Strutturale
USS San Francisco after collision with an underwater mountain 131 17/03/2023 PSA - Robustezza Strutturale
http://pressurevesseltech.as medigitalcollection.asme.org /article.aspx?articleid=16970 68# 17/03/2023 PSA - Robustezza Strutturale 137
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. 17/03/2023 PSA - Robustezza Strutturale 138
Esempi 139 17/03/2023 PSA - Robustezza Strutturale
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. 17/03/2023 PSA - Robustezza Strutturale 145
https://californiawaterblog.com/2 016/05/01/the-collapse-of-water- exports-los-angeles-1914/ 17/03/2023 PSA - Robustezza Strutturale 148
http://urbanplanet.info/architecture/par is-air-terminal-collapse-report-france/ 17/03/2023 PSA - Robustezza Strutturale 161
http://www.wise-uranium.org/img/stavaa.gif 17/03/2023 PSA - Robustezza Strutturale 167
Bonus track 174 17/03/2023 PSA - Robustezza Strutturale
http://www.confederationbridge.com/ab out/confederation-bridge/design.html 17/03/2023 PSA - Robustezza Strutturale 188
https://www.tuhh.de/sdb/starossek/Ver oeffentlichungen/Dateien/Progressive%2 0collapse%20of%20bridges%20(Uwe%20 Starossek).pdf 17/03/2023 PSA - Robustezza Strutturale 189
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. 17/03/2023 PSA - Robustezza Strutturale 197
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. 17/03/2023 PSA - Robustezza Strutturale 198
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. 17/03/2023 PSA - Robustezza Strutturale 199
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 17/03/2023 PSA - Robustezza Strutturale 200
Bonus track 202 17/03/2023 PSA - Robustezza Strutturale
HUMAN ERROR 17/03/2023 PSA - Robustezza Strutturale 203
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 17/03/2023 PSA - Robustezza Strutturale 204
Errors by Reason conoscenza valutazione scelta decisione esecuzione 17/03/2023 PSA - Robustezza Strutturale 205
conoscenza valutazione scelta decisione esecuzione 17/03/2023 PSA - Robustezza Strutturale 206
Factors (1) 17/03/2023 PSA - Robustezza Strutturale 209
Factors (2) 17/03/2023 PSA - Robustezza Strutturale 210
Errors by Rasmussen 17/03/2023 PSA - Robustezza Strutturale 212
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). 17/03/2023 PSA - Robustezza Strutturale 213
Sharp Criteria vs. Fuzzy Criteria 17/03/2023 PSA - Robustezza Strutturale 216
The effect of context 17/03/2023 PSA - Robustezza Strutturale 217
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 17/03/2023 PSA - Robustezza Strutturale 219
MANAGING THE UNEXPECTED 17/03/2023 PSA - Robustezza Strutturale 220
Unexpected events 17/03/2023 PSA - Robustezza Strutturale 223
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. 17/03/2023 PSA - Robustezza Strutturale 224
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. 17/03/2023 PSA - Robustezza Strutturale 225
Sensitivity to initial conditions 17/03/2023 PSA - Robustezza Strutturale 226
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. 17/03/2023 PSA - Robustezza Strutturale 227
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. 17/03/2023 PSA - Robustezza Strutturale 228
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. 17/03/2023 PSA - Robustezza Strutturale 229
http://abyss.uoregon.edu/~js/21st_century_science/lectures/lec08.html 17/03/2023 PSA - Robustezza Strutturale 230
http://abyss.uoregon.edu/~js/21st_century_science/lectures/lec08.html 17/03/2023 PSA - Robustezza Strutturale 231
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 17/03/2023 PSA - Robustezza Strutturale 232
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 17/03/2023 PSA - Robustezza Strutturale 234
HRO 17/03/2023 PSA - Robustezza Strutturale 235
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. 17/03/2023 PSA - Robustezza Strutturale 236
17/03/2023 PSA - Robustezza Strutturale 240 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. 17/03/2023 PSA - Robustezza Strutturale 242
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. 17/03/2023 PSA - Robustezza Strutturale 243
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. 17/03/2023 PSA - Robustezza Strutturale 244
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. 17/03/2023 PSA - Robustezza Strutturale 245
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. 17/03/2023 PSA - Robustezza Strutturale 246
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!” 17/03/2023 PSA - Robustezza Strutturale 247
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. 17/03/2023 PSA - Robustezza Strutturale 249
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. 17/03/2023 PSA - Robustezza Strutturale 250
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. 17/03/2023 PSA - Robustezza Strutturale 251
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. 17/03/2023 PSA - Robustezza Strutturale 252
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. 17/03/2023 PSA - Robustezza Strutturale 253
John Boyd 17/03/2023 PSA - Robustezza Strutturale 255
Principles of HRO 17/03/2023 PSA - Robustezza Strutturale 256
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. 17/03/2023 PSA - Robustezza Strutturale 257
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. 17/03/2023 PSA - Robustezza Strutturale 258
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. 17/03/2023 PSA - Robustezza Strutturale 259
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. 17/03/2023 PSA - Robustezza Strutturale 260
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. 17/03/2023 PSA - Robustezza Strutturale 261
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. 17/03/2023 PSA - Robustezza Strutturale 262
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. 17/03/2023 PSA - Robustezza Strutturale 263
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. 17/03/2023 PSA - Robustezza Strutturale 264
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. 17/03/2023 PSA - Robustezza Strutturale 265
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. 17/03/2023 PSA - Robustezza Strutturale 266
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. 17/03/2023 PSA - Robustezza Strutturale 267
People 17/03/2023 PSA - Robustezza Strutturale 268
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. 17/03/2023 PSA - Robustezza Strutturale 269
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. 17/03/2023 PSA - Robustezza Strutturale 270
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… 17/03/2023 PSA - Robustezza Strutturale 271
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. 17/03/2023 PSA - Robustezza Strutturale 272
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. 17/03/2023 PSA - Robustezza Strutturale 273
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. 17/03/2023 PSA - Robustezza Strutturale 274
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. 17/03/2023 PSA - Robustezza Strutturale 275
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. 17/03/2023 PSA - Robustezza Strutturale 276
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.” 17/03/2023 PSA - Robustezza Strutturale 277
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). 17/03/2023 PSA - Robustezza Strutturale 278
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. 17/03/2023 PSA - Robustezza Strutturale 279
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. 17/03/2023 PSA - Robustezza Strutturale 280
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. 17/03/2023 PSA - Robustezza Strutturale 282
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. 17/03/2023 PSA - Robustezza Strutturale 283
Kahneman and Tversky • We actively seek out evidence that confirms our expectations and avoid evidence that disconfirms them. • We tend to overesti

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