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![Figure 1.1: A typical use of offshore pipelines [72].](profile/Jie-Cai-9/publication/327449689/figure/fig1/AS:667590871511048@1536177475269/A-typical-use-of-offshore-pipelines-72_Q320.jpg)
![Figure 2.1: Three basic scenarios on structures [22].](profile/Jie-Cai-9/publication/327449689/figure/fig4/AS:667590871494658@1536177475435/Three-basic-scenarios-on-structures-22_Q320.jpg)
Contexts in source publication
Context 1
... petroleum industry has proven that pipelines are one of the most economical ways to transport crude oil and natural gas across extensive regions [27]. Figure 1.1 shows the typical use of pipelines underwater. Such pipes can be classified as flowlines transporting oil and/or gas from wells to manifolds, flowlines transporting oil and/or gas from manifolds to platforms, infield flowlines between different platforms, and export pipelines between platforms and bases onshore. ...
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... in a narrow definition, structural damage can also be large defects in terms of corrosion, dents, metal loss or large cracks due to factors such as mechanical interference, and natural forces (earthquakes, etc.) during different phases of pipelines including manufacturing, installa- tion, commissioning and operation. Figure 1.2: A typical mechanical interference between fishing equipment and pipelines un- derwater [46]. ...
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... ically, mechanical interference may be scenarios such as dropped foreign objects [25], drag- ging anchors, excavations, operation of underwater fishing equipment [46], sinking vessels and even mudslides on the sea bottom [65]. Figure 1.2 shows a typical mechanical interfer- ence between otter trawl and pipelines underwater. ...
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... parallel approaches (Finite Element Method (FEM), Experimental test and Analytical method) are used in this thesis, as seen from the flowchart in Figure 1.3. In order to answer these key questions in Section 1.3 and develop an effective solution, the FEM is particu- larly well suited due to its accessibility, reliable predictions, and wide use in engineering practice. ...
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... pipe thickness (t) and outer diameter (D) of each specimen were manually measured before the bending test, as listed in Tables 3.2 -3.6. Followed by a strict surface prepara- tion, i.e. polishing, and surface cleaning (as shown in Figure 3.14), the pipe thickness was measured by an ultrasonic thickness gauge. The general measured points are illustrated in Figure 3.15. ...
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... the end, silica gel was used for gauge protection. In addition, the horizontal ovalizations in critical cross-sections in the form of lateral displacement were measured by customized displacement meters, as seen in Figures 3.18 (a) and (b). The customized displacement meter was made of two steel bars with large stiffness and a flexible flat steel with small stiffness, attaching to the neutral axis of the specimen cross-section when using. ...
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... for specimens with a single crack either on the compression side or on the tensile side, no fracture failure has been observed. Instead, the same failure mode as the intact specimens occurs, as seen in Figure 3.21 (d). The phenomenon will be further discussed in Section 3.7. ...
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... strain here is normalized by ε 0 , which can be expressed as ε 0 = κ 0 D/2. It is observed that the occurrence of a dent has changed the strain distribution from the first beginning, and a localization of strain appears in the dented region, concentrating on both the dent center and the dent edge (Figures 4.14 (c) and (d)). Most of the strains measured from test lie on or close to the predictions curves. ...
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Citations
... Residual stresses can be defined as auto-balancing stresses which are locked into a material when it is free from external forces (Cai, 2018). In submarine pipelines, extensive residual stresses may exist due to many factors such as fabrication, pipe joining processes, welding, heat treatment, mechanical interferences, forming processes and long term service conditions (Jr et al., 1990;Amirat et al., 2004;Pirling et al., 2011). ...
... Meanwhile, it is accepted that the influence of lateral geometric imperfections dominates the influence of residual stresses when it comes to the axial buckling capacity of conventionally fabricated tubular columns (Bjoerhovde, 1973;Toma and Chen, 1979). This phenomenon has been also observed throughout the analysis of a damaged pipe under pure bending, accounting for both residual stresses and initial imperfections (Cai, 2018). ...
This paper consists of a literature review on the latest research progress about the lateral buckling of submarine pipelines under high temperature (HT) and high pressure (HP). First, the main general assumptions and simplifications made in the context of pipe lateral buckling are summarized in order to better understand the practical behavior of submarine pipelines. The governing equations of pipelines under uniaxial compression are then derived. Next, the controversial but widely deployed concept of effective axial force under complex sea environment is introduced. Influential parameters including initial imperfections, pipe-seabed interactions and residual stresses are elaborated and discussed. Furthermore, numerical simulation methods and experimental
tests dealing with the lateral buckling of pipelines are presented as well. Controlled methods which are practically used for buckle initiation are described. This paper also reveals the remaining challenges and new tendencies, such as the use of data-driven methods for the smart prediction of pipe buckling. Finally, a specific case study is numerically conducted. It is found that the effect of axial friction variation can be
generally ignored in practical calculations. This paper may provide a guidance for the design and research on pipelines in the future.
Due to increasing urbanisation rates worldwide combined with growing transportation demand, liveability of the urban environment is under pressure (UN, 2018). In response, many governments worldwide have set goals for increasing the share of trips made using sustainable modes of transport, such as walking and cycling. The use of active modes (i.e. walking and cycling) provides health benefits for individuals due to increased activity levels, and on a network level these modes (standalone or in combination with public transport) can potentially reduce traffic jams and the associated externalities (including air and noise pollution) when substituting the car. To achieve the desired increase in active mode shares, targeted policies need to be implemented. This requires a better understanding of who currently uses these modes, who could be persuaded to switch to active modes, and which determinants are driving active mode choice. This intended change towards active modes requires an adequate representation of walking and cycling in the transportation planning models in order to assess the effect of active mode policies on modal shares and distribution over the network. However, this is often not the case. Moreover, integration of active modes in these models occurs very slowly. Walking and cycling are often missing in transportation planning models, treated as a ‘rest’ category, or combined into slow/active modes, all of which result in incorrect estimates of the active mode shares, making it impossible to correctly identify the impact of potential policy measures on active mode shares. Examples of these policy measures are introduction of new infrastructure or changes to existing infrastructure, which impact route choice and distribution over the network, and reimbursement of using the bicycle to go to work, which impacts the mode choice of individuals.Investigating mode and route choice of active mode users increases the knowledge on active mode choice behaviour. By bridging this gap, the transportation planning models can potentially be improved. The objective of this thesis is ‘to understand and model mode and route choice behaviour of active mode users’. We identify six topics that are imperative to travel choices. First, we investigate the daily mobility patterns of individuals in relation to attitudes towards modes, because attitudes are considered to influence travel behaviour (Chapter 2). Afterwards, we zoom in on individual trips. We aim to understand which determinants drive the choice to walk or cycle (Chapter 3). In this topic we define the mode choice set as all feasible modes per individual and trip. However, not all feasible modes are used by individuals. Therefore, the third topic focuses on modes used over a long period of time, which we coin the experienced choice set. We investigate which determinants are relevant for including or excluding modes in this choice set (Chapter 4). Regarding cyclists’ route choice, we investigate the determinants influencing this choice (Chapter 5). This research is based on the experienced choice set. Accordingly, we compare this method to frequently used choice set generation methods to identify the added value of the experienced choice set (Chapter 6). Finally, we perform a literature review on how mode and route choice can be modelled simultaneously (Chapter 7).
