draft of ELEMENTARY CONCEPTS OF STRUCTURAL ROBUSTNESS OF BRIDGES AND VIADUCTS

Journal of Civil Structural Health Monitoring
ELEMENTARY CONCEPTS OF STRUCTURAL ROBUSNESS OF BRIDGES AND
VIADUCTS Franco Bontempi
--Manuscript Draft--
Manuscript Number:
Full Title: ELEMENTARY CONCEPTS OF STRUCTURAL ROBUSNESS OF BRIDGES AND
VIADUCTS Franco Bontempi
Article Type: Original Paper
Corresponding Author: FRANCO BONTEMPI, Ph.D.
Universita degli Studi di Roma La Sapienza
Rome, Italy ITALY
Corresponding Author Secondary
Information:
Corresponding Author's Institution: Universita degli Studi di Roma La Sapienza
Corresponding Author's Secondary
Institution:
First Author: FRANCO BONTEMPI, Ph.D.
First Author Secondary Information:
Order of Authors: FRANCO BONTEMPI, Ph.D.
Order of Authors Secondary Information:
Funding Information:
Abstract: This paper will explain the elementary aspects related to structural robustness.
The concept of structural integrity is firstly introduced and next it is considered how it
varies in time.
The different kind of progressive collapses are introduced with reference to real cases.
Design strategy ae then explained with reference of bridges and viaducts, considering
examples.
Finally, considerations about a more general view of structural robustness is
enlightened.
The role of design clima and conceptual design is stressed also in connection with
structural health monitoring.
In the whole paper, a practical point of view is used, as needed by designer.
Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation

1
ELEMENTARY CONCEPTS OF STRUCTURAL ROBUSNESS OF BRIDGES AND VIADUCTS
Franco Bontempi
1. DEFINITION.
In general terms, constructions - especially those typical of Civil Engineering - live for a
considerable period of years [1]. For example, in the case of common buildings, one talks about a
nominal 50-year life, while for more important or more valuable buildings such as bridges or
strategic infrastructural systems, 100 years are considered as service live time. It must be pointed
out that, while on the one hand special constructions can exceed even this duration as a nominal
service life period, even more common constructions experience lives longer than the nominal
ones assigned to them.
It seems therefore essential to consider how the quality of a construction evolves over time, and
in general terms, how it can reasonably survive all the events that may affect it [2].
The canonical way of considering the events that a construction faces during its life consists in
examining how it behaves in certain circumscribed situations called Limit State conditions [3];
then, the following conditions are considered:
I. service conditions, or functioning, which correspond to the current and correct use of the
structure, for levels of load foreseen precisely during normal operation;
II. ultimate conditions, which concern higher load values, to be defined however as realistic
and possible, and which may occur during the life of the construction;
III. extreme conditions, which concern exceptional load values, that are statistically extremal
values, or accidental scenarios, or events but which, also if still possible, cannot be
characterized statistically.
With reference to Fig.1, this picture can be summarized by introducing the following load levels for
a structure or an infrastructure:
I. a level of use, which involves frequent load scenarios;
II. a security level, which concerns maximum or rare load scenarios;
III. a level of integrity, which concerns extreme load scenarios - accidental or exceptional.
These load levels are ideally represented in Fig.1 for a demand D having a specified statistical
distribution [4]. Also, in this figure it is interesting to introduce different phenomena named black-
swan events [5]. These latter events are identified by the following characteristics:
1. they have a great impact, hard to foresee and very rare, which go beyond what is normally
expected in the historical, scientific, financial, technological and social fields;
2. it is impossible to evaluate the probability of such rare and consequences-laden events ex-
ante with canonical scientific methods;
3. they are easily explained ex-post, that is, once they have occurred.
The most striking example of a black-swan event of the last twenty years was the terrorist attack
on the Twin Towers of the World Trade Center in New York. In this regard, the presence of
psychological barriers that prevent people (both as individuals and as a community) from
Click here to access/download;Manuscript;structural
robustness FB 4 eng.docx
Click here to view linked References
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65

2
capturing the uncertainty and the huge role of rare events in the course of history must be
emphasized.
From all the above considerations, it appears evident that the necessary view of the state of a
structure as a whole, and of its evolution, must refer to the entire time horizon in which the
structure lives and is modified.
In a broad sense, all the quality of a structure can be summarized by the milestone concept of
structural integrity.
Structural integrity is the ability of an item - either a structural component or a structure
consisting of many components - to hold together under a load, including its own weight,
without breaking or deforming excessively. It assures that the construction will perform its
designed function during reasonable use, for as long as its intended life span. Items are
constructed with structural integrity to prevent catastrophic failure, which can result in
injuries, severe damage, death, and/or monetary losses.
Structural integrity can refer therefore, both the set of all the structural qualities, and the single
quality as appropriate. Obviously, how does this quality var for the structure - starting from when
it is new, or in its nominal configuration - throughout its life [8] must be appropriately taken into
account.
In this regard, with the help of Fig.2, the following main aspects can be ideally introduced to
describe the trend of the structural quality over time:
 on the vertical axis, the structural integrity is reported, intended, as seen previously, as an
overall measure of a building's ability to withstand the loads to which it is subjected by
performing the functions for which it was built;
 the horizontal plane, represents the time horizon; along its life, a building is exposed to two
types of events:
- the former take place regularly and can be represented along an axis where the
construction continuously decreases in quality (for reasons that can be classified as
“thermodynamic”: here the causes of degradation are natural, due to the environment
in which the structure is immersed (e.g. corrosion), or anthropic, related to the use
made of the building (e.g. fatigue); in these cases, the structure is required to meet the
durability requirement and the actions that occur in these cases can be probabilistically
characterized on the basis of a solid statistical database [9, 10, 11, 12, 13];
- the second typology of events, on the other hand, are discrete in nature: they occur in
specified instants, with scenarios that are difficult to frame in probabilistic terms - such
as coincidences or accidental actions - and introduce specific discontinuities in the
structural quality [14, 15]; with respect to these special situations, the concept of
robustness must be introduced in order to coherently express the requisite required to
the structure [16, 17, 18].
As shown Fig.2, we can consider how the construction develops over time a precise trajectory
according to the events that the construction itself experiences. Along the life of the structure, the
problem of restoring its integrity to an acceptable level can be posed: the capacity of a structure
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65

3
(and more generally of an infrastructure) to recover an adequate level of integrity is specifically
defined as resilience.
2. ROBUSTNESS.
The concept of structural robustness introduced in the previous section must now be further
discussed [19].
Structural robustness is the capacity of a structure (or, better a structural system) to experiment,
due to negative triggering events, a regular decrease of its structural quality (integrity). It implies:
A. some smoothness of the decrease of structural integrity due to negative events (intensive
feature);
B. some limited spatial spread of the failures inside the structure itself or outside this
(extensive feature).
This concept rooted in Structural Engineering, relates to similar others like:
 damage tolerance (Mechanical Engineering): property of a device (or a machine)
associated to its ability to safely sustain defects until repairing actions can be implemented.
The engineering approach to account for damage tolerance in design assumes that flaws
can exist in any structure and that such flaws certainly propagate with usage. In
engineering, a device or a machine is considered to be damage tolerant if it is possible to
implement a sustainable maintenance program that will result in the detection and repair
of accidental damage, corrosion and fatigue cracking before such damage reduces the
residual capacity of the structure below an acceptable limit.
 graceful degradation (Electronical Engineering): ability of a computer, electronic system or
network to maintain limited functionality even when a large portion of it has been
destroyed or rendered inoperative. The purpose of graceful degradation is to prevent
catastrophic failures. Ideally, even the simultaneous loss of multiple components does not
cause downtime in a system with this feature. In graceful degradation then, the operating
efficiency declines gradually as an increasing number of components fail.
Turning back to the definition of structural robustness, with the help of Fig.3, one can consider the
intensive aspect first. On the diagram represented in the figure, one found:
 on the vertical axis, there is the measure of structural integrity intended, as mentioned
above, the overall quality of the structure: the structural attributes that contribute to the
definition of the integrity are more than one and can be identified in reliability, availability,
maintainability, safety, security, ...;
 on the horizontal axis the magnitude of the generic negative cause a which cause structural
integrity to degrade: these causes are some identified threats and can be divided into [19,
20]:
a) defect: it is a flaw, and represents a potential cause, active or dormant, of damage;
b) wrong layout: the system is in a wrong state that may or may not cause a failure;
c) failure: permanent interruption of a system ability to perform a requested function in
specific operating conditions.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65

4
Through the diagram in the figure, one can judge the quality of the structure in its nominal
configuration and in the damaged one by following the development of the quality as
consequence of a negative cause and in function of the relative magnitude of it. It can therefore
be seen, for example, that the green line characterizes a structure that performs better in nominal
conditions than that characterized by the blue line: the latter, however, results in degrading
performance more slowly as the magnitude of the negative cause increases and is, therefore,
more robust.
It is worth to note that, in order to assess the robustness of a structure, it is not important to know
the precise nature of the negative causes, but only magnitude is required: triggering negative
causes can have the most disparate origins and occurring mechanisms.
Furthermore it should be noted that just as shown in Fig.3, it is possible to develop only a
comparative analysis between different structures to define their relative greater or lesser
robustness: in other words, it is not really possible (and useful) to define an absolute metric to
evaluate the structural robustness, despite all the proposals (not extendable outside the few
academic cases conceived) present in the literature.
The extensive aspect of the structural robustness character requires the examination of how a
possible failures or ruptures - not being essential to know how it originated - propagates in the
structure and perhaps to its exterior: this propagation can conduct to the so-called progressive
collapse.
This disastrous event is also known in other disciplines with the terms of cascade effect or chain
reaction. A cascading effect is an inevitable and sometimes unpredictable chain of events due to a
triggering action that affects a system: in biology, the term cascade refers to a process that, once
started, gradually proceeds to its seemingly inevitable conclusion. A chain reaction is the
cumulative effect produced when an event triggers a chain of similar events: generally, it refers to
a linked sequence of events in which the time-lapse between successive events is relatively small.
These terms are of crucial importance in Engineering when the run-away of the system like the
one illustrated in Fig.4 must be avoided: here we see how a negative effect can grow
exponentially, until it takes on a magnitude that comes out of the expected frame of reference , in
an imaginative way represented by the concept of Chinese syndrome.
In order to understand how such catastrophic manifestations can be avoided [22, 23], and
specifically focusing on the structural engineering field, it is useful to consider the trivial example
shown in Fig.5, where the case of a structure subject to simultaneous loads in two directions is
show: the collapse can occurs without any lateral heeling (no sway) or, differently, it can occur by
involving a global lateral displacement (sway). If, for two different design solution, both collapse
typologies are achieved at the same load multiplier, this means that there is no distinction of merit
between the two solutions in terms of ultimate bearing capacity (or verification of the Ultimate
Limit State). In effect, on closer inspection, the way to collapse without lateral heeling (no sway)
which involves an implosion of the structure is judicially considered better than the sway collapse:
the latter, in fact, can involve other structural parts even of a nearby construction and it can
therefore give rise to a succession of breaks which are typical of progressive collapse.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65

5
The concept of structural robustness allows, therefore, to distinguish between a good collapse,
e.g. an implosive process in which objects are destroyed by collapsing on themselves, and bad
collapses that can trigger unconfined/propagated failures.
Due to this intrinsic need of fully evaluating the structural behavior up to the advanced stages of
collapse, even beyond the maximum bearing capacity, it is necessary to study the response of the
entire structural system. With reference to Fig.6, it can be seen that, while for the usual checks to
the Service or Ultimate Limit States it may be sufficient to consider verification criteria at the
punctual level (structural material), at the sectional level or at the element level, on the contrary,
the coherent assessment of the structural robustness requires the analysis of the entire system,
appropriately taking into account the different types of nonlinearities that are developed during
the collapse phases. It is understood that this computational effort is required only for
constructions of a certain complexity, being possible to consider more synthetic/simplified models
for simpler constructions [24, 25, 26].
3. TIPOLOGIES OF PROGRESSIVE COLLAPSES.
Due to the inherent danger associated to the progressive collapse phenomenon, it is necessary to
examine its features in more detail. Three types of progressive collapse are classified [19]:
I. Pancake-type collapse: it is schematically illustrated in Fig.7, it foresees the subsequent
collapse of structural parts from top to bottom; although more common in the case of
buildings, where an upper floor can fall on the floor below, that in turn falls on the one below
and so on, this collapse can occur also in case of bridges, as shown in Fig.8 with reference to
the collapse of the Cypress Street Viaduct, in which the upper traffic route has fallen on the
below one;
II. Domino-type collapse: it is schematically illustrated in Fig.9 where it is noticed that a collapsing
element turns over the adjacent one which in turn involves the next one and so on; an
example of a structure prone to this type of progressive collapse is illustrated by the diagram
of Fig.10 which represents a viaduct with “crutch” type elements: the collapse of one of these
crutches, would induce unbalance in the next one and so on;
III. Zip-type collapse: in this case, the structure separates like a zipper; the theoretical scheme of
Fig.11 can occur, for example, in suspension bridges in which the hangers that connect deck to
main ropes break in succession: an emblematic case is represented by the collapse of the
Tacoma Narrow Bridge mentioned in Fig.12.
It is important to be aware that these types of progressive collapses are common to different
systems: for example, the tragic collapse of the Stava dams can be traced to a progressive domino-
type collapse.
4. DESIGN STRATEGY FOR ROBUSTNESS.
As frequently happens in Engineering, the experience accumulated during occurred failures leads
designers to implement new design solution in order to avoid the failures as already occurred, or
at least contrast them: this is a process of knowledge increasing that typical of Forensic
Engineering [27]. A further aspect to be considered is that it is possible (and would be auspicable)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65

6
to implement design ideas coming from the analogy with other types of Structural Engineering not
belonging to Civil Engineering: in particular, the concept of robustness is intrinsic in the structures
envisaged in Naval Engineering and in Aeronautical Engineering. From these considerations, we
can identify two design strategies to obtain robust constructions [8, 16].
Strategy I: increase the continuity of the structure.
The first strategy to provide robustness to a structure, is to make the components/parts of the
structure highly connected. In this way, the structure tends to be more statically indeterminate
and can therefore show a redundancy of load transfer paths from the point of application to the
ground. It must however be noted that there is no direct correlation between increased degree of
statically indeterminacy and increased robustness.
To get an idea of this strategy, we can naturally refer to the fuselages of airplanes. Fig.13
illustrates a well-known case of arrested collapse in an aircraft attacked during the Second World
War: the fuselages of these aircraft were, in fact, highly connected being composed of bundles of
elements (geodetic rods) which overall were difficult to cut.
This high degree of connection which makes it possible to suffer the failure of some elements
without experimenting a generalized collapse, presenting a redundancy in the loads path , has
been lacking, for example, in the case of the New Haengju Bridge in Korea, shown in Fig.14: in this
case, the local failure of a support led to a global crisis for the bridge. An analogous local failure in
the Nipigon River Bridge in Canada (Fig.15), has instead caused only reparable damage due to the
presence, in this bridge, of a curtain of stays which carried the load also in damaged state.
Precisely these considerations have led over the years to shift from cable-stayed bridge schemes
with few stays to modern schemes with a significant number of stays.
Strategy II: segmenting the structure.
This second strategy to make a structure robust appears, paradoxically, to be at the opposite of
the previous one: to make a structure robust it is necessary to divide it into compartments as
more isolated as possible from each other, in this way the collapse of one of these compartments
remains confined in the compartment itself and does not propagate to the rest of the structure.
The strategy operates, therefore, trying to make the structure discontinuous instead of increasing
the continuity between the structural parts. The compartmentation strategy is largely used in
design field other than structural engineering, as for example in contrasting the development of a
fire: the concept of compartmentalization against the spread of flames is well known.
The compartmentation does not necessarily imply a physical separation: with reference to Fig.16,
which again shows an aircraft, the loss of part of the nacelle was interrupted by the presence of
strong frames (transverse elements to the aircraft axis). These elements are like the ring nuts of
pipelines, which have the purpose of stopping loss of shape of the pipeline section. Furthermore,
the compartmentalization present in the ships allows them to suffer the flooding of one of its
parts without the ship sinking. Finally, the separation can be not only spatial but also on a time
basis: think, for example, of the quarantine measure implemented in the case of contagious
diseases of populations.
The application of the compartmentation strategy in bridge structures has ancient origins:
consider, for example, the masonry railway bridge that connects Venice to the mainland built in
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65

7
1846 (Fig.17). In this structure, the presence of every five masonry arches of a solid element that
can arrest the propagation of the progressive collapse of arches if one of them had collapsed it is
evident. The presence of these elements of strength is evident, for example, also in the case of the
viaduct on the Haute Marne represented in Fig.18: also, here this characteristic of the “genetic
code” of the structure is immediately recognizable.
The case of viaducts.
The strategy of segmenting a structure to make it more robust has more general characteristics
than the one aiming at the increasing of the structural continuity, in this sense it is worth to think
to the situations when one wants to avoid the propagation of damage, and then the objects are
spatially separated by distancing them each other [28, 29].
The same idea of applying this spatial separation can therefore be useful in the case of viaducts.
The viaducts, in fact, differ from bridges due to their greater linear development and the presence
of structural objects arranged in series along the road: in this sense, while a bridge is a single
object, a viaduct can be viewed as consisting of multiple aligned objects.
From this elementary observation, the concept of structural robustness must be declined with
different attentions to a single bridge and to an entire viaduct. For the entire viaduct, the
segmentation strategy is essential, in fact the loss of a (even conspicuous) part of the structural
system is acceptable, while the overall loss (as can happen in the case of the development of a
progressive collapse that interests all over the viaduct), is not acceptable.
A historical case of localized collapse was that following the impact of the Esso Maracaibo oil
tanker on a pile of the viaduct on the homonymous lake in Venezuela: thanks to an overall static
scheme of the viaduct that provided for separations between the pylons, by a “buffer” beam, the
collapse of one of these piles caused the loss of about 300 meters of deck but did not produce a
progression of collapse to the entire viaduct over seven kilometers (Fig.19).
While in this case one may have doubts about the conscious choice to make the viaduct as robust
as a whole, a case in which one is sure that the robustness was explicitly considered in the
conceptual design, is that of the Confederation Bridge viaduct in Canada. In this case, the design
configuration of the bridge was identified in a way that would allow a part of the deck to be
removed without this dragging the rest: this was achieved either by introducing a hinge along the
deck and by cutting the prestressing cables that otherwise could have dragged towards the low
the deck in most of its length (Fig.20).
5. CONCLUSION: A WIDER LOOK ON STRUCTURAL ROBUSTNESS.
In general terms, it is worth to retrace the path that, starting from the analysis of occurred
structural collapses, leads to conceive new design solution that avoid the same collapses or, at
least, can moderate them.
In this view, a general model that makes it possible to order the factors that can lead to a
structural crisis, already exists. Let us focus on the diagram in Fig.21, showing the Reason’s model
[29], which represents any system, and therefore bridge structures, as obtained from a series of
steps - idealized as a layer - from the one of conceptual design to the realization one, and so on.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65

8
However, in each of these steps, there are inevitably shortcomings, errors or imperfections, ideally
represented as holes in the layers. The Reason’s model predicts that when these holes, these
shortcomings, are aligned, then what is only a threat (hazard), propagates through the layers and
become a real collapse, having the initial hazard perforated all the defenses of the system.
This explanatory model of general utility in Forensic Engineering - also known as Swiss Cheese
Model for Failure due to its clear similarity with the swiss cheese - allows us to examine and order
all the phases and sequences that eventually led to a crisis [27]. One can recognizes, in fact, that
there may be weaknesses or shortcomings in the following “layers”:
(0) in the “design clima”, understood as a set of knowledge and awareness at the time of
project design;
(1) in the conception of the structure;
(2) in the development of technical drawings and graphic representations;
(3) in the design/assessment calculations;
(4) in the choice of materials and components;
(5) in the construction phases;
(6) in the use of the structural system;
(7) in the occurrence of accidental or exceptional events, perhaps linked to dormant defects or
latent threats;
(8) in maintenance;
(9) in monitoring.
It is therefore appropriate and necessary to extend the concept of robustness from the
consideration of strictly structural aspects to that of the overall process that leads from
conception to the conscious use of the structure. This consideration is the one that leads the
concept of a broader definition of robustness, by including - in addition to accidental actions such
as fire, explosions and impacts - also the effects related to human error. This is a crucial concept.
In fact, already in the foundations of the Eurocodes in the 1990s, we find the definition:
Robustness is the ability of a structure to withstand events like fire, explosions, impact or
the consequences of human error, without being damaged to an extent disproportionate to
the original cause.
If this systemic vision is appropriate and necessary, among all these steps, particular attention
must be devoted to the level (0) (design clima), due to its imperceptibility to the actors operating
along the entire life of the structure , and to the level (1) (conceptual design) which concerns the
initial aspects of the design. In this conceptual design phase, which involves the highest and most
creative intellectual abilities, the “genetic basis” of the structure is provided by the designer. This
basis is called “genetic” because it will mark the structure, representing both its positive qualities
and its native weaknesses: these weaknesses are those that can lead to catastrophic collapses in
the future.
In this regard, in Fig.22 it is considered the well-known Almö Bridge (inaugurated in 1960), which
connected the island of Tjörn (Sweden's seventh largest island) to the mainland. The bridge
collapsed on January 18, 1980, when the MS Star Clipper ship impacted the arch of the bridge.
Eight people died that day while driving until the road, that was closed 40 minutes after the
accident. The choice of an arch shape for the bridge can be identified as a congenital weakness
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65

9
that, after many years and many naval transits, at a certain point “exploded” leading to a
catastrophic collapse: in fact, the new bridge that was built and inaugurated in 1981 was cable-
stayed.
As can be argued, the genetic defects deriving from a wrong - or not fully explored - structural
conception cannot be corrected even by the most sophisticated analyzes and verifications, leading
sooner or later to structural collapse.
It must also be emphasized that only a clear understanding of the assumptions involved in levels
(0) (climate in which a work was designed) and (1) (understanding of structural design) can allow
the implementation of an appropriate monitoring activity: only in these cases, the monitoring
activity can actually be useful, until the point of being considered as a structural augmented
capacity [31, 32, 33].
Finally, the framework provided by Fig.21 sheds light on even more general aspects of the overall
structural robustness, with reference to the entire life of a structure. In fact, this framework
highlights the role of the actors that design and manage the infrastructure, actors that play a key
role during the life of the system. This point of view, therefore, clearly identifies the administrative
and managerial dimension of responsibility, raising the level thereof from the mere technical level
to the managerial one.
References
[1]. Bontempi F., Arangio S., Sgambi L., Tecnica delle Costruzioni: basi della progettazione.
Elementi intelaiati in acciaio. (in Italian), p. 1-389, Carocci, ISBN: 9788843044566, 2008.
[2]. EN 1990. Basis of structural design, Brussels: Comité Européen de Normalization CEN, 2002.
[3]. NTC 2018. Norme Tecniche per le Costruzioni, (in Italian), Italy, Ministero delle Infrastrutture,
2018.
[4]. Schneider, Structural Engineering Documents: Introduction to Safety and Reliability of
Structures (SED-5), Zürich: IABSE-AIPC-IVBH, 1997.
[5]. Taleb Nassim Nicholas, The Black Swan: The Impact of the Highly Improbable. (1st ed.).
London: Penguin. p. 400. ISBN 1-84614045-5, 2007.
[6]. Arangio S. & Bontempi F., Soft Computing Based Multilevel Strategy for Bridge Integrity
Monitoring, Computer-Aided Civil and Infrastructure Engineering, 25, 348–362, 2010.
[7]. Arangio S., Bontempi F. & Ciampoli M., Structural integrity monitoring for dependability,
Structure and Infrastructure Engineering, 7 (1), 75-86, 2010.
[8]. Bontempi F., Basis of design and expected performances for the Messina Strait Bridge, In:
Proceedings of the International Conference on Bridge Engineering – Challenges in the 21st
century, 1–3 November 2006 Hong Kong.
[9]. Petrini F. & Bontempi F., Estimation of fatigue life for long span suspension bridge hangers
under wind action and train transit, Structure and Infrastructure Engineering, 7 (7-8), 491-
507, 2011.
[10]. Petrini F., Giuliano F. & Bontempi F., Comparison of time domain techniques for the
evaluation of the response and the stability in long span suspension bridges, Computers and
Structures, 85 (11-14), 1032–1048, 2007.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65

10
[11]. Malerba P.G., Sgambi L., Ielmini D. & Gotti G., Influence of Corrosive Phenomena on the
mechanical behaviour of R.C. Elements. Proceedings of the 2011 World Congress on
Advances in Structural Engineering and Mechanics. Seoul, Ko-rea, 1269-1288, 2011.
[12]. Dordoni S., Malerba P.G., Sgambi L. & Manenti S., Fuzzy reliability assessment of bridge piers
in presence of scouring, In: Proceedings of The Fifth International Conference on Bridge
Maintenance, Safety and Management (IABMAS’10), 11-15 July 2010 Philadelphia (USA).
[13]. Petrini F., Li H. & Bontempi F., Basis of design and numerical modeling of offshore wind
turbines, Structural Engineering and Mechanics, 36 (5), 599-624 2010.
[14]. S. Arangio, F. Bontempi, Basis of the analysis and design for fire-induced collapses in
structures, International Journal of Lifecycle Performance Engineering (IJLCPE), Vol.1, No 2,
2013.
[15]. EN 1993-1-2. Design of steel structures - Part 1-2 General rules - Structural fire design,
Brussels: Comité Européen de Normalisation CEN, 2005.
[16]. Bontempi F., Robustezza strutturale, (in Italian) Relazione ad invito, Atti del Convegno
CRASC’06, Università degli Studi di Messina, Messina, 20-22 aprile 2006, Dario Flaccovio.
[17]. Atti del Convegno GLI EUROCODICI PER LA PROGETTAZIONE STRUTTURALE ANTINCENDIO,
18 settembre 2008, ISA Roma, F. Bontempi, C. Crosti, L. Giuliani, La robustezza strutturale nei
confronti delle azioni accidentali, http://www.vigilfuoco.it/aspx/download_file.aspx?id=4830
(in Italian).
[18]. Olmati P., Petrini F., Bontempi F., Numerical analyses for the assessment of structural
response of buildings under explosions, Structural Engineering and Mechanics, 45 (6), 803-
819, 2013.
[19]. Starossek U., Progressive Collapse of Structures, Inst of Civil Engineers Pub, 2 ed. 2017.
[20]. Laprie, J.-C., ed., Dependability: Basic Concepts and Terminology, New York: Springer- Verlag,
1992.
[21]. Avizienis A., Laprie J-C. & Randell B., Dependability and its Threats: A Taxonomy, In: R.
Jacquart, ed. 18th World Computer Congress, Building the Information Society, 22-27 August
2004 Toulouse. Boston: Springer, 91-120, 2004.
[22]. Starossek U., Avoiding Disproportionate Collapse in High-Rise Buildings, ASCE SEI 2008
Structures Congress—Crossing Borders, Vancouver, Canada April 24-26, 2008
[23]. Milana G., Olmati P., Gkoumas K., & Bontempi F., Ultimate Capacity of Diagrid Systems for
Tall Buildings in Nominal Configuration and Damaged State, Periodica Polytechnica Civil
Engineering, 59(3), 381-391. https://doi.org/10.3311/PPci.7795, 2015.
[24]. Silvestri M. & Bontempi F., Strategy and formulation levels of the structural performance
analysis of advanced systems, In: F. Bontempi, ed., Second International Conference on
Structural and Construction Engineering ISEC-02, 23-26 September 2003 Rome, Lisse: Swets
& Zeitlinger, 2495-2502.
[25]. Gentili F, Giuliani L, Bontempi F. Structural response of high-rise buildings to fire: system
characteristics and failure mechanisms, Journal of Structural Fire Engineering, p. 9-26,
Volume 4, Number 1, 2013.
[26]. Giuliani L., Structural safety in case of extreme actions, Special Issue on: "Performance and
Robustness of Complex Structural Systems", Guest Editor Franco Bontempi, International
Journal of Lifecycle Performance Engineering (IJLCPE), in press (ISSN: 2043-8648), 2012.
[27]. Bontempi F., Ingegneria Forense in campo strutturale, Dario Flaccovio Editore, 2017.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65

11
[28]. Simon H.A., The sciences of the artificial, Cambridge, The MIT Press, 1998.
[29]. C. Perrow, Normal Accidents, Princeton University Press, 1999.
[30]. J. Reason, Human Error, Cambridge University Press, 1991.
[31]. Bontempi F., Frameworks for Structural Analysis. In: B.H.V. Topping, ed. Innovation in Civil
and Structural Engineering Computing, Stirling: Saxe-Coburg Publications, 1-24 (2005).
[32]. Bontempi F., Giuliani L. & Gkoumas K., Handling the exceptions: dependability of systems and
structural robustness, In: A. Zingoni, ed. 3rd Int. Conference on Structural Engineering,
Mechanics and Computation (SEMC), September 10-12, 2007 Cape Town, Rotterdam:
Millpress.
[33]. Bontempi F., Gkoumas K. & Arangio S., Systemic approach for the maintenance of complex
structural systems, Structure & Infrastructure Engineering, 4 (2), 77-94, 2008.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65

OBJECT
NET
Structural
System
Infrastructural
System
USE
SAFETY
INTEGRITY
f(D)
D
Mean
Frequent
Maximum
Rare
Accidental
Exceptional
BlackSwanEvents
Service Limit States
Ultimate Limit States
Integrity Limit States
1Figure 1 – Levels of use of a structure or infrastructure.
Manuscript

2Figure 2 – Time horizon for a structure or for an infrastructure.

ATTRIBUTES
RELIABILITY
AVAILABILITY
SAFETY
MAINTAINABILITY
…
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
STRUCTURALINTEGRITY
less robust
more robust
Nominal
conFiguretion
Damaged
conFiguretion
3Figure 3 – Definition of structural robustness.

Figure 4 – Run-away of a structural system.
time
effect

“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
STRUCTURE
& LOADS
Collapse
Mechanism
NO SWAY
SWAY
5Figure 5 – Sway and no sway collapses.

UsualULS&SLS
VerificationFormat
Structural Robustness
Assessment
1st level:
Material
Point
2nd level:
Element
Section
3rd level:
Structural
Element
4th level:
Structural
System
6Figure 6 – Assessment levels for a structure.

7Figure 7 – Pancake type collapse.

8Figure 8 – Cypress Street Viaduct collapse.

9Figure 9 – Domino type collapse.

10Figure 10 – Viaduct scheme with crutch elements.

11Figure 11 – Zip type collapse.

12Figure 12 – Tacoma Narrow Bridge collapse.

13Figure 13 – Damage reported in a B17 aircraft during the Second World War.

14Figure 14 – New Haengju Bridge global collapse.

15Figure 15 – Nipigon River Bridge partial collapse.

16Figure 16 – Damage reported in a Boeing 737-200 aircraft in 1988.

17Figure 17 – Ponte della Libertà in Venice.

18Figure 18 – Chaumont Viaduct Haute Marne.

19Figure 19 – Maracaibo Viaduct incident.

20Figure 20 – Preliminary and final design of Confederation Bridge in Canada.

HAZARD
IN-DEPTH
DEFENCE
HOLES DUE TO
ACTIVE ERRORS
HOLES DUE TO
HIDDEN ERRORS
[0] DESIGN CLIMA
[1] CONCEPTUAL DESIGN
[2] DRAWINGS
[3] CALCULATION
[4] MATERIALS/COMPONENTS
[5] CONSTRUCTION
[6] USE
[7] ACCIDENTS / EXCEPTIONS
[8] MAINTENANCE
[9] MONITORING
21Figure 21 – Reason Model for incident (Swiss Cheese Failure Model).

draft of ELEMENTARY CONCEPTS OF STRUCTURAL ROBUSTNESS OF BRIDGES AND VIADUCTS

Recommended

Recommended

More Related Content

Similar to draft of ELEMENTARY CONCEPTS OF STRUCTURAL ROBUSTNESS OF BRIDGES AND VIADUCTS

Similar to draft of ELEMENTARY CONCEPTS OF STRUCTURAL ROBUSTNESS OF BRIDGES AND VIADUCTS (20)

More from Franco Bontempi

More from Franco Bontempi (20)

Recently uploaded

Recently uploaded (20)

draft of ELEMENTARY CONCEPTS OF STRUCTURAL ROBUSTNESS OF BRIDGES AND VIADUCTS