Common Case Studies of Marine Structural Failures

Full text

3,250+
OPEN ACCESS BOOKS
105,000+
INTERNAT IONAL
AUTHORS AND EDITORS 111+ MILLION
DOWNLOADS
BOOKS
DELIVERED TO
151 COUNTRIES
AUTHORS AMONG
TOP 1%
MOST CITED SCIENTI ST
12.2%
AUTHORS AND EDITORS
FROM TOP 500 UNIVERSITIES
Selection of our books indexed in the
Book Citation Index in We b of Science ™
Co re Collection (BKCI)
Chapter fr om the boo k
Failure Analysis and Pre vention
Downloade d fro m: http://www.intechopen.com/boo ks /failure -analysis -and-pr evention
PUBLISH ED B Y
World's largest Science,
Technology & Medicine
Open Access book publisher
Interested in publishing with InTechOpen?
Contact us at book.dep artment@intechope n.com

Chapter 9
Common Case Studies of Marine Structural Failures
Goran Vukelić and Goran Vizentin
Additional information is available at the end of the chapter
http://dx.doi.org/10.5772/intechopen.72789
Provisional chapter
© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,
and reproduction in any medium, provided the original work is properly cited.
DOI: 10.5772/intechopen.72789
Common Case Studies of Marine Structural Failures
GoranVukelić and GoranVizentin
Additional information is available at the end of the chapter
Abstract
Marine structures are designed with a requirement to have reasonably long and safe
operational life with a risk of catastrophic failures reduced to the minimum. Still, in
a constant wish for reduced weight structures that can withstand increased loads,
failures occur due to one or several following causes: excessive force and/or tempera-
ture induced elastic deformation, yielding, fatigue, corrosion, creep, etc. Therefore, it
is important to identify threats aecting the integrity of marine structures. In order
to understand the causes of failures, structure’s load response, failure process, pos-
sible consequences and methods to cope with and prevent failures, probably the most
suitable way would be reviewing case studies of common failures. Roughly, marine
structural failures can be divided into structural failures of ships, propulsion system
failures, oshore structural failure, and marine equipment failures. This book chapter
will provide an overview of such failures taking into account failure mechanisms, tools
used for failure analysis and critical review of possible improvements in failure analysis
techniques.
Keywords: marine structures, failure analysis, fracture, fatigue, failure
1. Introduction
Marine structures must comply with such design requirements that the probability of fail-
ures or stability loss of parts and/or complete structures is reduced to minimum. Studies and
analysis of marine structural failures had shown that a signicant percentage of failures were
a consequence of inadequate design due to lack of operational considerations, incomplete
structural elements evaluations, and incorrect use of calculation methods.
Structural safety level is determined during design process by dening specic structural
elements, material properties, and functional requirements based on the expected lifetime
of the structure, ramications of eventual failures and costs of failures. Time dependency
© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly cited.

of strength and loads has to be taken into account because the strength of a structure will
decrease with time while the load is varying through the lifetime of the structure.
Successful material selection process implies reconciling requirements like suitable strength
of material, sucient level of rigidity, appropriate heat resistance, etc. Structures that are
susceptible to crack growth need to be made of materials selected on the basis of fracture
mechanics parameters. Fracture mechanics parameters that dene material resistance to crack
propagation are usually determined through experimental research, but nowadays some of
the experiments can be successfully substituted with numerical analysis. Material fracture
behavior is usually estimated using some of the well-established fracture parameters, like
stress intensity factor (K), J-integral or crack tip opening displacement (CTOD). Besides that,
fatigue limit has to be taken into account, also. It has become customary to perform an opti-
mal fatigue design analysis as an integral part of design calculations. Such analyses are also
largely based on data and procedures developed from experimental and empirical research.
Marine structural failures can be divided into three main groups: failures of ships, oshore
structures, and marine equipment. This book chapter will provide an overview of most com-
mon case studies of such failures. Further, failure mechanisms will be emphasized and tools
used for failure analysis outlined. Possible improvements in failure analysis techniques are
discussed in the end of the chapter.
2. Common case studies
2.1. Ship structural failures
Maybe the most notable case of ship failures are failures of Liberty ships in the early 1940s.
These failures gave a serious boost in the development of fracture mechanics. Ships, mass
produced in assembly line style out of prefabricated sections as an all-welded construction,
exhibited nearly 1500 cases of brile fractures with 12 ships breaking in half. The results of
failure investigation had shown that inadequate grade of steel allowed for brile fracture at
low temperatures. Further, rectangular hull openings, such as hatch square corners, that coin-
cided with a welded seam acted as stress concentrations points and crack origins [1].
There has been a considerable amount of failures in recent times, also. For instance, structural
failure of container ship MOL Comfort [2, 3] in 2013. A yearlong failure investigation con-
centrated on nding the possibility of fracture occurrence and structural safety level. Results
had shown that the hull fracture originated from the boom bu joint in the midship part.
A possibility that the load’s upper limit exceeded strength’s lower limit was also estimated
using probabilistic approach. Furthermore, safety inspections of the MOL Comfort sister
ships have shown buckling deformations (concave and convex) of the boom shell plating of
up to 20 mm (4 mm allowable) in height observed near the center line. Finally, a numerical
analysis of the ship hull taking the load history into account was done. After the investigation,
it was concluded that the load of the vertical bending moment probably exceeded the hull
girder ultimate strength when the deviations of the uncertainty factors are taken into account,
Failure Analysis and Prevention136

which caused the boom shell plates to buckle due to excessive load. The reduction of breadth
of boom shell plate between girders increased the stress in the girder which yielded in the
lower part resulting in the collapse occurs in the middle part of the ship, at the boom, near
the center line.
Bilge keels structures are used to enhance the transverse stability of ships. Cracks have been
noticed in various ships in the internal structure of the bilge keels and on the connecting
points to the ship’s hull. Failure analysis of the damage can identify the causes of failure and
the analysis results serve as basis for design improvements. It has been shown, both theoreti-
cally and applying FEM analysis, that the failure locations in bilge keels structures occur in
the stress concentration regions that are present due to the structure geometry commonly
used, therefore new structural elements are proposed that signicantly reduce the possibility
of failure occurrence [4].
Corrosively aggressive cargo (acids, alkalis, etc.) can represent a danger to the integrity of
ship structures. In the case of the “Stolt Roerdam” freighter, which sank during the cargo
loading in the port, the investigation (visual, macrofractographic, and chemical) following the
sinking has shown that the residue valve has cracked due to a design-specic stress (stier
main valve was missing), thus causing a leak of the acid that accelerated the corrosion process
of the oor panels in the area of the leak. Also, the valve gaskets were made of a material not
resistant to acid which also contributed to the speed of the leak [5].
Marine engines and propellers produce dynamic loads on their supportive structures which
can lead to fatigue failures. One of the most stressed components of the engine structure is
the bearing bushing foundation. A state-of-the-art design procedure for the bearing girders is
comprised of essential procedures such as bearing loads determination, stresses calculation,
and the bearing girder fatigue strength assessment [6]. The fatigue and structural durabil-
ity analysis is conducted for multi-axial stresses and opens the possibility to construct light-
weight engines.
2.2. Propulsion system failures
The propulsion system has a pivotal role on ships. A typical marine propulsion system is
comprised of main engine, driving device, marine shaft, and propeller. Most of the failures
occur on the propulsion shaft that is subjected to various types of loading during operation
(torque moment, bending moment, axial thrust force, and transversal loads). The operating
environment of the propulsion system is characterized by signicant changes in temperatures
and humidity, aggressive atmosphere, long-lasting interrupted operating time, and varia-
tions in load amplitudes. The risk of failures of the propulsion system additionally increases
with the severity of sea and weather conditions as they have a direct eect on the dynamics
of the load variation. All of the above has direct inuence on fatigue behavior and life time of
the propulsion shaft.
Shaft keys are recognized as a potential origin of growing cracks. The geometry of the ends of
keyways represents a stress concentration factor in the cases of torque transmission through
shaft keys for dynamic vibrational loads. Faulty machining of shaft key elements (key groove,
Common Case Studies of Marine Structural Failures
http://dx.doi.org/10.5772/intechopen.72789
137

keyway, and key) geometry, inadequate run out radii, or material imperfection can be root
causes of torsional fatigue failure in shaft keys. The characteristic torsional failure indicator
is the crack paern that initiates at the end of the keyway and propagates in a 45° rotational
direction in a helical shape. Also, interaction between engine body and hull must be taken into
account, especially thermal loads that can aect the integrity of shafts and can be successfully
solved numerically [7], Figure 1.
A case study [8] has shown that inadequate torsional vibration calculation parameters (shaft
elements stiness and damping, natural frequencies, safety factors) and a subsequent poor
design of the shaft’s keyway cause failures. In this case a root cause analysis was done by the
analytical stress calculation process MIL G 17859D and VDI 3822 standards. A FEM model
was used in order to verify the existing fracture characteristics and causes.
An alternative to shaft key joints are spline joints, which are press ed to other shaft ele-
ments. Analysis of spline joint failure [9] shows that the press ing of the joining elements
can cause surface deformation which in turn causes surface cracks formation. Cracks usu-
ally start on the spline teeth at the shaft junction zone. Torsional fatigue caused by uctuat-
ing stress promotes crack growth and propagation. Inhomogeneity of the shaft material can
additionally assist crack propagation. In this case, visual and macroscopic inspection was
performed, followed by material chemical analysis, hardness measurement, optical, and scan-
ning electron microscope (SEM) microstructure analysis with X-ray dispersive analysis of
particles under the SEM.
Bolted connections are used in collar coupling of shaft elements and in propeller blades con-
nections. The changes of rotation direction of the shaft results in torque moment overloading
Figure 1. Engine body-ship hull interaction and thermal loads presenting a threat to structural integrity.
Failure Analysis and Prevention138

and direction change as well as thrust force direction change. The resulting eect is a dynamic
load on collar coupling bolts in a longer operating time [10], which can result in fatigue failure.
The freing that occurs on adjacent connecting surfaces in these cases creates micronotches
that develop into fatigue cracks with the direction of failure growth in planes angled from
35 to 60° which is not a characteristic of pure torsional fatigue failures. The analysis showed
that the coupling bolts are subjected to an increasing bending moment which contributes to
fatigue crack growth. The experimental research and numerical calculation done in this case
study proved the hypothesis of variable bending stress in the coupling as the failure cause.
Bolted connections of propeller blades and the shaft are often in a cathodic protection envi-
ronment. Hydrogen inclusions in the material and variable stress conditions can cause crack
nucleation and propagation, nally causing a failure [11]. Fractographic analysis, chemical
analysis, microhardness tests, slow strain rate test, microstructure analysis, and nite element
analysis were performed in this case.
Abnormal performance of the propeller by way of one non-performing malformed blade can
generate a uniaxial force which uctuates once per rotation in a consistent transverse direc-
tion across the shaft. The uctuating force generates a couple which can cause fatigue failure
of the propeller hub [12]. Uniaxial type of failure is characterized by a fatigue fracture with
a single origination point that progresses across the shaft from the side where the force is
being applied and results in the nal overload failure occurring on the opposite side from the
uctuating force. Visual inspection, detail axis alignment measurements, microscopic metal-
lurgical examination, hardness measurements, and ultrasonic scanning were used during the
analysis.
2.3. Oshore structural failure
Oshore structures can be divided into three groups: xed platforms (steel template and
concrete gravity structures), compliant tower (compliant, guyed and articulated tower, and
tension leg platform), and oating structures (oating production, storage and ooading
systems).
The loads on oshore structures are gravity (self-weight, various equipment, xed platform
elements, and uid loads), environmental (winds, waves, currents, and ice), exploitation
loads, and seismic loads. Environmental loads play a major role in oshore structures design
process.
In complex structures, such as oshore platforms, a fatigue failure of a single structural ele-
ment may not result in a catastrophic failure of the entire structure, but it denitely changes
the expected lifetime of the structure. The need for structural system failure probability esti-
mation of typical marine structures in combination of fatigue and fracture arises. A proposed
numerical and analytical method had been tested on real structures, like a Neka jack-up plat-
form (Iran Khazar) [13], by applying various fatigue sequences that could lead to the collapse
of the platform structure. This comparison has shown that the calculated system failure prob-
ability is higher for the case of combined fatigue and fracture scenarios than for only fatigue
or fracture induced structure collapse which emphasizes the need for regular inspections of
marine structures.
Common Case Studies of Marine Structural Failures
http://dx.doi.org/10.5772/intechopen.72789
139

Oshore pipelines are usually damaged in the form of dents and gouges, which reduces its
static and dynamic load bearing capacity as well as the fatigue life reduction in comparison
to undamaged pipelines. The extent of the fatigue lifetime change depends on the type of the
dent, and it can be analyzed and assessed analytically or numerically (FEM) [14]. Fatigue life
analysis helps in the decision on the necessity of repairs and/or replacement of the damaged
pipelines, i.e., planning of inspection and maintenance activities. Oshore pipelines segments
are usually connected by welds which usually contain surface of embedded defects which
exhibit large plastic strain characteristics if fracture occurs. In such cases, nonlinear elastic
plastic fracture response should be modeled [15].
Subsea structures are subjected to signicant external pressure loads which makes structural
buckling a dominant failure mechanism. Ultra-deep water subsea separators are key equip-
ment of subsea production in oshore petroleum industry. An experimental and numerical
investigation on buckling and post-buckling of a 3000 m subsea separator has been done by
Ge et al. [16]. The analysis has shown that the buckling behavior of deep sea structures can
be assessed accurately applying numerical nonlinear global buckling analysis, proven by the
comparison with experimental analysis results.
2.4. Marine equipment failure
This section deals with failures of marine equipment such as port or dock cranes, cables and
ropes, pressure vessels-mounted onboard ships, and underwater pipelines.
Cranes can be subject to unexpected sudden events which can be divided into accidents and
emergencies. Catastrophic failure of a dockside crane jib [17] occurred in the proximity of the
standing tower, near the connection of the jib’s three main tubes to the tower. Upon the visual
inspection of the fracture surfaces, the presence of a large pre-existing crack was evident.
The crack originated from a seam weld and propagated through one of the main pipes of
the crane jib space frame. The failure occurred during maneuvering with no load aached.
During the investigation crane material properties were obtained experimentally (tensile tests
and Charpy impact tests) and the crane design was veried by FE analysis. Fatigue analy-
sis was conducted, according to standards (FEM 1.001, Eurocode 3), for the welding joints
and the pipes. Failure mode analysis was done from fracture mechanics and plastic collapse
approaches. All of the analysis and investigations brought to the conclusion that the fatigue
design of the jib structure was not done according to standards and that the nal failure was
determined by plastic collapse, after a long stable propagation period of a dominant crack
which originated at the edge of a seam weld.
As for the pressure vessel failures, there are two main reasons for failures, i.e., pressure part
failure (safety valves failures, corrosion, and low water level) or fuel/air explosions in the fur-
nace (gas or liquid fuel leaks). Inadequate construction characteristics of high pressure tubes can
cause failures. An investigation of a prematurely ruptured high-pressure oil tube has shown that
inadequate pipe type (longitudinally welded instead of seamless) and material (design speci-
ed material replaced by a lower grade one) as well as inadequate installation procedures (not
enough pipe clamps which allowed vibrations) resulted in vibration induced fatigue crack [18].
Failure Analysis and Prevention140

All equipment on marine structures is maintained and serviced continuously. In case of a
malfunction, in-situ repairs are often performed. The quality of workmanship and material
choice do have a great importance in such cases. Bending stresses in equipment elements that
should be subjected only to tensile stress (ropes, wires, etc.) can cause failure of such elements.
Numerical analysis of dierent wire rope cross section congurations is performed in order to
determine remaining fatigue of operating wire ropes in dockside cranes [19], Figure 2.
Subsea umbilicals are composite cable and small diameter tubular bundles deployed on the
seabed in conjunction with oshore installations for oil or gas exploitation. These tubes are
loaded by alternating internal pressure and exposed to sea currents, i.e., dynamic loading [20].
Cracks in this type of equipment result in leaks and loss of load-carrying capacity. Umbilical
tubes experience loss of circularity in shape (ovalization) and are subjected to re-rounding pro-
cedures by applying boost pressure prior to service which also translates in fatigue loading.
3. Failure causes and mechanisms
The strength of a structure represents a limit state of loading conditions above which the
structure loses ability to achieve its specied required function. As long as the actual strength
of the structure is kept higher than the actual loading demands, a given marine structure can
be deemed safe. Otherwise, structural failures will occur.
Structural failure can be dened as loss of the load-carrying capacity of a component or
member within a structure or of the structure itself (including global failure modes like
capsizing, sinking, positioning system failures, etc.). The failure can result in catastrophic
Figure 2. Numerical analysis of remaining fatigue life of a wire rope.
Common Case Studies of Marine Structural Failures
http://dx.doi.org/10.5772/intechopen.72789
141

damage (i.e., complete loss of the structure itself) or partial structure damage when the
structure can be repaired or recovered. Global failures can more often result in fatal casual-
ties, while smaller and localized structural damage may result in pollution and recoverable
structural damage.
Structural failure is initiated when the material in a structure is stressed to its strength limit,
thus causing fracture or excessive deformations. The structural integrity of a marine structure
depends on load conditions, the strength of the structure itself, manufacturing and materials
quality level, severity of service conditions, design quality as well as various human elements
that have eects during exploitation of the structure.
There are two distinctive groups of failure causes. The rst group is comprised of unforesee-
able external or environmental eects which exert additional loading on the structure result-
ing in over-load. Such eects are extreme weather (overloads), accidental loads (collisions,
explosions, re, etc.), and operational errors. The second group comprises the causes for fail-
ures that occur either during the design and construction phase (dimensioning errors, poor
construction workmanship, material imperfections) or due to phenomena growing in time
(fatigue), both resulting in reduced actual strength in respect to the design value. All of the
listed causes can partially or completely be a result of human factor.
The process of fatigue failure itself is highly complex in nature and it is dependent on a large
number of parameters. The factors are numerous and perhaps the most signicant are mean
stress (distribution), residual stresses, loading characteristics and sequence, structural dimen-
sions, corrosion parameters, environmental temperature, design criteria fabrication methods
and quality.
Failure mechanisms that usually occur in marine structures can be progressive (excessive
yielding, buckling, excessive deformations) or sudden (brile and fatigue fractures). Excessive
yielding and brile fractures occur when the load exceeds critical strength, while buckling
and fatigue fractures depend on time and specic load conditions.
4. Failure analysis tools
The analysis methods can be grouped into methods that use nominal stresses (typical for stan-
dard codes) acting to a structure or part of a structure and then compare the stress amplitude
to nominal S-N curves. This approach is appropriate for structures that are standardized, and
therefore well backed up with statistical experimental data that can be used as initial assump-
tions for fatigue analysis. The alternative is the evaluation of local stresses inuence to fatigue
(notch stress factors, N-SIF).
Some authors [21] divide fatigue analysis methods in two groups: S-N approach based on fatigue
tests and fracture mechanics approach. The rst method is used for fatigue design purpose using
simplied fatigue analysis, spectral fatigue analysis, or time domain fatigue analysis to deter-
mine fatigue loads. The second method is used for determination of acceptable aw size, pre-
diction of crack growth behavior, planning maintenance of the structure, and similar activities.
Failure Analysis and Prevention142

The latest trend in failure analysis development is the unication of analysis methods and
procedures [22–24], in order to obtain a comprehensive procedure of structural failure analy-
sis that would cover main failure modes and enable a safer and more ecient design, manu-
facture and maintenance processes.
4.1. Experimental tools
Nondestructive testing and examination (NDT and NDE), as well as structural health moni-
toring (SHM), of structures play a signicant role in fracture analysis and control procedures.
Any method used must not alter, change, or modify the failed condition, but must survey
the failure in a nondestructive mode so as to not impact, change, or further degrade the fail-
ure zone. This kind of examination provides input values for fracture analysis, which yields
results that dene inspection and maintenance intervals for the structure and represent input
values for life prediction estimates. Structures are inspected at the beginning of their service
life in order to document initial aws which determine the starting point of the structure
fatigue life prediction. The most commonly used procedures for marine structures are optical
microscopy, scanning electron microscopy (SEM), GDS, and acoustic emission (AE) testing.
Optical microscopy is a common and most widely used NDT analysis method which enables
rapid location and identication of most external material defects. This technique is often
used in conjunction with micro-sectioning to broaden the application. One of the main disad-
vantages is the narrow depth-of-eld, especially at higher magnications.
Scanning electron microscopy is an extension of optical microscopy in failure analysis. The
use of electrons, instead of a light source, provides much higher magnication (up to 100,000×)
and much beer depth of eld, unique imaging, and the opportunity to perform elemental
analysis and phase identication. The examined item is placed in a vacuum enclosure and
exposed with a nely focused electron beam. The main advantage of this method is minimal
specimen preparation activity due to the fact that the thickness of the specimen does not pose
any inuence to the analysis, ultra-high resolution, and 3D resulting appearance of the test
object. Various analyses of marine structures and equipment have been conducted using SEM
[25–28], one of them being analysis of speed boat steering wheel fracture, Figure 3.
As it is well known, structural supporting members emit sounds prior to their collapse, i.e.,
failure. This fact has been the basis of the development of scientic methods of monitoring
and analysis of these sounds with the goal to detect and locate faults in mechanically loaded
structures and components. AE provides comprehensive information on the origin of a dis-
continuity (aw) in a stressed component and also provides information about the develop-
ment of aws in structures under dynamic loading. Discontinuities in stressed components
release energy which travels in the form of high-frequency stress waves. Ultrasonic sensors
(20 kHz–1 MHz) receive these waves or oscillations and turn them into electronic signals
which are in turn processed on a computer yielding data about the source location, intensity
frequency spectrum, and other parameters that are of interest for the analysis. This method
is passive, i.e., no active source of energy is applied in order to create observable eects as in
other NDT methods (ultrasonic, radiography, etc.). Three sources of acoustic emissions are
recognized, namely primary, secondary, and noise. The primary sources have the greatest
Common Case Studies of Marine Structural Failures
http://dx.doi.org/10.5772/intechopen.72789
143

structural signicance and originate in permanent defects in the material that manifest as local
stresses, either on microstructural or macrostructural level. The amount of acoustic emission
energy released, and the amplitude of the resulting wave, depends on the size and the speed
of the source event. The main advantages of AE compared to other NDT methods are that AE
can be used in all stages of testing. Additionally, it is less sensitive to changes in geometry, the
scanning is remote and it gives real-time evaluation [29]. The disadvantages are the sensitivity
to signal aenuation in the structure, less repeatability do to the uniqueness of emissions for a
specic stress/loading conditions, and external noise inuence on accuracy.
4.2. Analytical tools
Although various analytical models have been proposed by a number of authors, no compre-
hensive model exists. Analytical methods have been developed for prediction of progressive
structural failures of marine structures [30]. The nite element modeling approach for predic-
tion of the development of failures is accurate, but can be time consuming. Analytical pro-
cedures, based on spectral fatigue analysis, beam theory, fracture mechanics, and structural
factors, can provide solutions in considerably less time when needed.
The goal is to dene approaches for computing the fracture driving force in structural com-
ponents that contain cracks. The most appropriate analytical methodology for a given situa-
tion depends on geometry, loading, and material properties. The decisive choice factor is the
character of stress. If the structure behavior is predominantly elastic, linear elastic fracture
mechanics can yield acceptable results. On the other hand, when signicant yielding precedes
fracture, elastic-plastic methods, such as referent stress approach (RSA) and failure assessment
diagram (FAD), need to be used. Since a purely linear elastic fracture analysis can yield invalid
and inaccurate results, the safest approach is to adopt an analysis that spans the entire range
from linear elastic to fully plastic behavior. One of the methods that can be applied is the FAD
approach.
Figure 3. Experimental analysis of fractured speed boat steering wheel coupled with numerical analysis.
Failure Analysis and Prevention144

The FAD approach has rst been developed from the strip-yield model and it uses two param-
eters which are linearly dependent to the applied load. This method can be applied to ana-
lyze and model brile fracture (from linear elastic to ductile overload), welded components
fatigue behavior, or ductile tearing. The stress intensity factors are dened on the basis of the
structure collapse stress and the geometry dependence of the strip-yield model is eliminated
[31, 32]. The result is a curve that represents a set of points of predicted failure points, hence
the name failure assessment diagram. The failure assessment diagram is basically an alterna-
tive method for graphically representing the fracture driving force.
Depending on the type of the equation used to model the eective stress intensity factors the
FAD approach can be sub-divided into the strip-yield based FAD, J-based FAD, and approxi-
mated FAD. The J-based FAD includes the eects of hardening of the material, while the
simplied approximations of the FAD curve are used to reduce the calculation times of the
analysis. When stress-strain data are not available for the material of interest generic FAD
expressions may be used [33], which assume that the FAD is independent of both geometry
and material properties. The simplied curves proved adequate for most practical applica-
tions due to the fact that design stresses are usually below yield point. Fracture analysis in
fully plastic regime requires an elastic-plastic J analysis.
Marine structures are subjected to dynamic load that are characterized by exactly unpredict-
able, stochastic changes of value (environmental factors). Most fracture mechanics analyses
are deterministic, therefore a need to view fracture probabilistically for real world condi-
tions arise. The probabilistic fracture analysis overlaps the probability distributions of driving
force in the structure and toughness distribution in the structure to obtain a nite probabil-
ity of failure. Probabilistic methods can take into account time-dependent crack growth and
stress corrosion cracking by applying appropriate distribution laws. Most practical situations
exhibit randomness and uncertainty of the analysis variables so numerical algorithms for
probabilistic analysis may be needed to apply. The well-known Mote Carlo method has been
proven to be suited to accompany FAD models in cases of uncertainties.
Recently, normative institutions have been involved in projects and research, together with
industry, in order to establish probabilistic methods for planning in-service inspection for fatigue
cracks in oshore structures. DNV-issued recommendations on how to use probabilistic methods
for jacket structures, semisubmersibles, and oating production ships [34]. Basically, the goal of
probabilistic method is to replace inspection planning based on engineering assessment of fatigue
and failure consequences with mathematical models for the inuence of exploitation, fatigue
causes, and crack propagation characteristics on the lifetime of the structure to obtain a more reli-
able and secure assessment methodology independent of the engineers’ level of expertise.
Li and Chow [35] have developed a fatigue damage model by formulating a set of damage
coupled constitutive and evolution equations in order to write a computer software that could
predict the behavior of oshore structures under dynamic load. The fatigue damage model is
based on sea wave’s characteristics statistics. The model also includes historical damage data.
Cui [36] has focused his research on the requirement for accurate fracture growth predictions
that preceding fatigue strength assessment methods, mainly based on cumulative fatigue
Common Case Studies of Marine Structural Failures
http://dx.doi.org/10.5772/intechopen.72789
145

damage theory using stress-endurance curves (S-N), have not taken into account. The eects
of initial defects and load sequence are included in the prediction model. A fatigue crack prop-
agation theory has been proposed as technically feasible and adoptable method for fatigue
life prediction using commercial FEA/FEM software packages for the calculation processes.
The need for a database of the size and distribution of initial defects for marine structures is
emphasized.
Li et al. [37] have developed an improved procedure for creation of standardized load-time
history for marine structures based on a short-term load measurement. The need for load-time
history arises from the dependency fatigue crack growth behavior to load sequence eect.
It is known that small variations in the initial (basic) assumptions for a fatigue analysis can
have signicant inuence for the predicted crack growth time. As mentioned above, the S-N
based calculations are sensitive to input parameters values and denitions [38]. As the occur-
rence of a crack is not strictly deterministic, probabilistic methods for the prediction of crack
behavior and sizes, based on fatigue crack propagation theory, can resolve accuracy prob-
lems. Probabilistic methods require extensive database of standardized load-time histories for
marine structures, based on extensive experimental research, which can be used in analysis
procedures.
4.3. Numerical tools
The eective application of numerical methods in fracture mechanics and fatigue analysis
begun with the development of computer science in the second half of the twentieth cen-
tury. Various methods were used (nite dierence method, collocation methods, and Fourier-
transformations) but the nite element method (FEM) has been established as a standard due
to its universality and eciency. FEM enables complicated crack conguration analysis under
complex loads and non-linear material behavior.
Recent years have brought a signicant development and increase in accessibility of com-
mercial computational software and hardware for nite element analysis applications, marine
structures included. This enables more advanced and detailed fatigue and fracture analysis
even for more complex large-scale structures. Furthermore, numerical tools can be used to
complement or even substitute experimental analyses, as in the material selection stage in
design process [39], Figure 4.
As the extent of scientic material published on this maer is very ample, here recently devel-
oped methods will be briey described and referenced.
Extended FEM (X-FEM) is the most recent nite element method developed and is used
mainly for fracture mechanics applications. Based on the nite element method and fracture
mechanics theory, X-FEM can be applied to solve complicated discontinuity issues including
fracture, interface, and damage problems with great potential for use in multi-scale computa-
tion and multi-phase coupling problems. The method has been introduced in 1999 [40] and
since then further developed by various authors. The basic idea of the method is to reduce
the re-meshing around the crack to a minimum. The improvements enabled the crack to be
represented in the FE model independently from the mesh itself [40, 41]. The solution for the
Failure Analysis and Prevention146

problem of modeling curved cracks was developed by forming higher order elements [42].
Improved XFEM methods are continuously being developed by various researchers as the
method has been proven as very valuable.
Various computer software packages for fatigue crack growth analysis have been developed
by NASA. FASTRAN is a life-prediction code based on the crack-closure concept and is used
to predict crack length against cycles from a specied initial crack size to failure for many
common crack congurations found in structural components. NASA FLAGRO v2 fatigue
crack growth computer program developed as an aid in predicting the growth of pre-existing
aws and cracks in structural components using a two-dimensional model which predicts
growth independently in two directions based on the calculation of stress intensity factors.
Recently, specic numerical automatic crack box technique (CBT) has been developed in
order to enable to perform ne fracture mechanics calculations in various structures without
global re-meshing [43]. The algorithm can be used for FEM calculations with ABAQUS code.
The method represents an improvement as only the specic crack zone has to be re-meshed
Figure 4. Numerical prediction of material fracture behavior using FE models of fracture mechanics standardized
specimens in order to get dependence of J-integral to crack growth.
Common Case Studies of Marine Structural Failures
http://dx.doi.org/10.5772/intechopen.72789
147

which results in simpler and time saving calculations. Also, the method allows the analysis of
the inuence of plastic material characteristics on the crack growth path.
5. Conclusions
This chapter provided an overview of common failures of marine structures taking into
account failure mechanisms and tools used for failure analysis. As shown, the majority of
employed failure analysis is comprised of visual, analytical, and mechanical inspection meth-
ods in the aempt to identify failure causes. The working conditions in which marine struc-
tures operate are often stochastic in nature and strongly dependent on weather conditions at
sea as well on loading conditions of the structure. The complexity of failure analysis accentu-
ates the need for numerical simulation of possible catastrophic scenarios during the entire
lifetime span of the structure. If the marine structures coupled with the relevant data collected
during maintenance procedures are numerically modeled than a tool for failure prediction
can be developed. Therefore, complete analysis comprising analytical, experimental, and
numerical research is desirable to obtain satisfying results.
Acknowledgements
The materials and data in this publication have been obtained through the support of the
International Association of Maritime Universities (IAMU) and The Nippon Foundation in Japan.
Author details
Goran Vukelić* and Goran Vizentin
*Address all correspondence to: gvukelic@pfri.hr
Faculty of Maritime Studies Rijeka, University of Rijeka, Rijeka, Croatia
References
[1] Zhang W. Technical problem identication for the failures of the liberty ships. Challenges.
2016;7:20. DOI: 10.3390/challe7020020
[2] Class NK. Investigation Report on Structural Safety of Large Container Ships. Tokyo:
Class NK; 2014.
[3] CLCSS. Final Report of Commiee on Large Container Ship Safety (English Version)
Tokyo: CLCSS; 2015. pp. 1-30
Failure Analysis and Prevention148

[4] Martins RF, Rodrigues H, Leal das Neves L, Pires da Silva P. Failure analysis of bilge
keels and its design improvement. Engineering Failure Analysis. 2013;27:232-249. DOI:
10.1016/j.engfailanal.2012.06.002
[5] Zunkel A, Tiebe C, Schlischka J. “Stolt Roerdam”—The sinking of an acid freighter.
Engineering Failure Analysis. 2014;43:221-231. DOI: 10.1016/j.engfailanal.2014.03.002
[6] Grubišić V, Vulić N, Sönnichsen S. Structural durability validation of bearing girders
in marine diesel engines. Engineering Failure Analysis. 2008;15:247-260. DOI: 10.1016/j.
engfailanal.2007.01.014
[7] Murawski L. Thermal interaction between main engine body and ship hull. Ocean
Engineering. 2018;147:107-120. DOI: 10.1016/j.oceaneng.2017.10.038
[8] Han HS, Lee KH, Park SH. Parametric study to identify the cause of high torsional vibra-
tion of the propulsion shaft in the ship. Engineering Failure Analysis. 2016;59:334-346.
DOI: 10.1016/j.engfailanal.2015.10.018
[9] Arisoy CF, Başman G, Şeşen MK. Failure of a 17-4 PH stainless steel sailboat propeller
shaft. Engineering Failure Analysis. 2003;10:711-717. DOI: 10.1016/S1350-6307(03)00041-4
[10] Dymarski C. Analysis of Ship Shaft Line Coupling Bolts Failure. Journal of Polish
CIMAC. 2009;4(2):33-40
[11] Zhenqian Z, Zhiling T, Chun Y, Shuangping L. Failure analysis of vessel propeller
bolts under fastening stress and cathode protection environment. Engineering Failure
Analysis. 2015;57:129-136. DOI: 10.1016/j.engfailanal.2015.07.013
[12] Aurecon New Zealand Limited. Aratere Shaft Failure Investigation. Wellington: Aurecon
New Zealand Limited; 2015
[13] Shabakhty N. System failure probability of oshore jack-up platforms in the combi-
nation of fatigue and fracture. Engineering Failure Analysis. 2011;18:223-243. DOI:
10.1016/j.engfailanal.2010.09.002
[14] Macdonald KA, Cosham A, Alexander CR, Hopkins P. Assessing mechanical damage in
oshore pipelines—Two case studies. Engineering Failure Analysis. 2007;14:1667-1679.
DOI: 10.1016/j.engfailanal.2006.11.074
[15] Zhang YM, Yi DK, Xiao ZM, Huang ZH. Engineering critical assessment for oshore
pipelines with 3-D elliptical embedded cracks. Engineering Failure Analysis. 2015;51:
37-54. DOI: 10.1016/j.engfailanal.2015.02.018
[16] Ge J, Li W, Chen G, Li X, Ruan C, Zhang S. Experimental and numerical investigation on
buckling and post-buckling of a 3000 m subsea separator. Engineering Failure Analysis.
2017;74:107-118. DOI: 10.1016/j.engfailanal.2017.01.001
[17] Frendo F. Analysis of the catastrophic failure of a dockside crane jib. Engineering Failure
Analysis. 2013;31:394-411. DOI: 10.1016/j.engfailanal.2013.02.026
Common Case Studies of Marine Structural Failures
http://dx.doi.org/10.5772/intechopen.72789
149

[18] Pardal JM, de Souza GC, Leão EC, da Silva MR, Tavares SSM. Fatigue cracking of high
pressure oil tube. Case Studies in Engineering Failure Analysis. 2013;1:171-178. DOI:
10.1016/j.csefa.2013.07.001
[19] Vukelic G, Vizentin G. Damage-induced stresses and remaining service life predictions
of wire ropes. Applied Sciences. 2017;7:107-113. DOI: 10.3390/app7010107
[20] Zerbst U, Stadie-Frohbös G, Plonski T, Jury J. The problem of adequate yield load solu-
tions in the context of proof tests on a damaged subsea umbilical. Engineering Failure
Analysis. 2009;16:1062-1073. DOI: 10.1016/j.engfailanal.2008.05.013
[21] Bai Y. Marine Structural Design. 1st ed. Amsterdam: Elsevier; 2003
[22] Gutiérrez-Solana F, Cicero S. FITNET FFS procedure: A unied European procedure
for structural integrity assessment. Engineering Failure Analysis. 2009;16:559-577. DOI:
10.1016/j.engfailanal.2008.02.007
[23] Cui W, Wang F, Huang X. A unied fatigue life prediction method for marine structures.
Marine Structures. 2011;24:153-181. DOI: 10.1016/j.marstruc.2011.02.007
[24] Choung J. Comparative studies of fracture models for marine structural steels. Ocean
Engineering. 2009;36:1164-1174. DOI: 10.1016/j.oceaneng.2009.08.003
[25] Vukelic G. Failure study of a cracked speed boat steering wheel. Case Studies in
Engineering Failure Analysis. 2015;4:76-82. DOI: 10.1016/j.csefa.2015.09.002
[26] Peng C, Zhu W, Liu Z, Wei X. Perforated mechanism of a water line outlet tee pipe for
an oil well drilling rig. Case Studies in Engineering Failure Analysis. 2015;4:39-49. DOI:
10.1016/j.csefa.2015.07.002
[27] Ilman MN, Kusmono. Analysis of internal corrosion in subsea oil pipeline. Case Studies
in Engineering Failure Analysis. 2014;2:1-8. DOI: 10.1016/j.csefa.2013.12.003
[28] Harris W, Birki K. Analysis of the failure of an oshore compressor crankshaft. Case
Studies in Engineering Failure Analysis. 2016;7:50-55. DOI: 10.1016/j.csefa.2016.07.001
[29] Hellier CJ. Handbook of Nondestructive Evaluation. 2nd ed. New York: McGraw-Hill
Education; 2013
[30] Bardetsky A, Lee A. Analytical prediction of progressive structural failure of a damaged
ship for rapid response damage assessment. In: Proceedings of the ASME 2014 33rd
International Conference on Ocean, Oshore and Arctic Engineering; 2016. pp. 1-9
[31] Dowling AR, Townley CHA. The eect of defects on structural failure: A two-criteria
approach. International Journal of Pressure Vessels and Piping. 1975;3:77-107. DOI:
10.1016/0308-0161(75)90014-9
[32] Milne I, Ainsworth R, Dowling A, Stewart A. Assessment of the integrity of structures
containing defects. International Journal of Pressure Vessels and Piping. 1988;32:3-104.
DOI: 10.1016/0308-0161(88)90071-3
Failure Analysis and Prevention150

[33] Milne I, Ainsworth R, Dowling A, Stewart A. Background to and validation of CEGB
report R/H/R6—Revision 3. International Journal of Pressure Vessels and Piping.
1988;32:105-196. DOI: 10.1016/0308-0161(88)90072-5
[34] Veritas DN. Probabilistic Methods for Planning of Inspection for Fatigue Cracks in
Oshore Structures. 2015. p. 264
[35] Li DL, Chow CL. A damage mechanics approach to fatigue assessment in oshore
structures. International Journal of Damage Mechanics. 1993;2:385-405. DOI: 10.1177/
105678959300200405
[36] Cui W. A feasible study of fatigue life prediction for marine structures based on crack
propagation analysis. Proceedings of the Institution of Mechanical Engineers, Part M.
2003;217:11-23. DOI: 10.1243/147509003321623112
[37] Li S, Cui W, Paik JK. An improved procedure for generating standardised load-time
histories for marine structures. Proceedings of the Institution of Mechanical Engineers,
Part M. 2016;230:281-296. DOI: 10.1177/1475090215569818
[38] Lotsber I, Sigurdsson G, Fjeldstad A, Torgeir M. Probabilistic Methods for Planning of
Inspection for Fatigue Cracks in Oshore Structures. Marine Structures. 2016;46:167-192.
[39] Vukelic G, Brnic J. Numerical prediction of fracture behavior for austenitic and mar-
tensitic stainless steels. International Journal of Applied Mechanics. 2017;9:1750052-1-
1750052-11. DOI: 10.1142/S1758825117500521
[40] Belytschko T, Black T. Elastic crack growth in nite elements with minimal remeshing.
International Journal for Numerical Methods in Engineering. 1999;45:601-620. DOI:
10.1002/(SICI)1097-0207(19990620)45:5<601::AID-NME598>3.0.CO;2-S
[41] Moës N, Dolbow J, Belytschko T. A nite element method for crack growth without
remeshing. International Journal for Numerical Methods in Engineering. 1999;46:131-
150. DOI: 10.1002/(SICI)1097-0207(19990910)46:1<131::AID-NME726>3.0.CO;2-J
[42] Sonsino C. Fatigue testing under variable amplitude loading. International Journal of
Fatigue. 2007;29:1080-1089. DOI: 10.1016/j.ijfatigue.2006.10.011
[43] Lebaillif D, Recho N. Brile and ductile crack propagation using automatic nite ele-
ment crack box technique. Engineering Fracture Mechanics. 2007;74:1810-1824. DOI:
10.1016/j.engfracmech.2006.08.029
Common Case Studies of Marine Structural Failures
http://dx.doi.org/10.5772/intechopen.72789
151