Transmission pipelines that cross regions prone to ground movement events can experience large longitudinal strains resulting in circumferential strains due to Poisson’s effect. The design trend for new pipelines in areas prone to ground movement has evolved from a stress-based design approach to a strain-based design (SBD) approach to further realize the cost benefits from using higher strength line pipe steels. This paper presents an overview of SBD for pipelines subjected to large cyclic longitudinal strain and high internal pressure, with emphasis on the cyclic tensile strain capacity of microalloyed line pipe steel. The technical basis for this paper involved engineering analysis and examination of the mechanical behavior of grade X80 line pipe steel in both the longitudinal and circumferential directions. Low-cycle fatigue analyses were performed with varying internal pressures. SBD models discussed in this paper are based on classical plasticity theory and account for material anisotropy, triaxial strain, and microstructural damage effects developed from test data. The results are intended to enhance SBD and analysis methods for producing safe, cost-effective pipelines capable of accommodating large plastic cyclic strains.
This paper aims to compare wave tank experimental results in scale 1:40 on two different Tension-Leg-Buoy (TLB) platforms with CFD simulations. The CFD simulations are carried out using the Volume of Fluid (VOF) method included in the STAR-CCM+ code from CDadapco.
Displacements for free decay tests for heave, time-series of tower motions, mooring line tension for regular wave cases and mooring line tension for two regular wave cases in intermediate water depth are presented in the results and compared with experiments.
Good agreement was found with the experiments and the interactions between hydrodynamic loading and motions resulted to be well captured.
Lee, Jangguen (Korea Institute of Civil Engineering and Building Technology) | Kong, Jangguen (Korea Institute of Civil Engineering and Building Technology) | Kim, Youngtak (Korea Institute of Civil Engineering and Building Technology) | Kang, Jaemo (Korea Institute of Civil Engineering and Building Technology)
In-situ capping is designed to isolate and stabilize the undersea contaminated sediment. Though in-situ capping is being applied, longterm stability to keep the pollutants from being discharged needs to be carefully studied. Hydraulic model testing using a wave generator was carried out to identify the erosion for required cap thickness to be maintained, which are a critical factor to determine long-term stability of in-situ capping. 0.075~0.425 mm sand was used as capping material by applying 1:10 scale factor. The capping material was placed by a one-touch opening device in a wave channel before generating the wave, and then various wave conditions were imposed so as to monitor the geometry change of cap which was formed by a mound of the capping material. Consequently, with a 50-year frequency wave height at a proposed site, very little erosion was monitored but causing excessive erosion by increasing wave height.
In Oil & Gas industry Engineering Criticality Assessments (ECAs) are routinely used to provide defect acceptance criteria for pipelines welds joints. Methodologies for industrial application are given in BS7910 (2013), API579-1 (2007), R6, DNV-OS-F101 (2013). Failure Assessment Diagram (FAD) is commonly used for ECA of flawed components. However for ductile material, the use of stress-based approach leads to very conservative assessment. In such case the strain based design could be more appropriated. The purpose of this paper is to introduce a method in order to establish the threshold value of plastic failure criterion for ECA Strain-Based design application.
Bae, Jin-ho (Technical Research Laboratories, POSCO) | Ro, Yun-Jo (Technical Research Laboratories, POSCO) | Chon, Seung-hwan (Technical Research Laboratories, POSCO) | Sung, Hyo Kyung (Pohang University of Science and Technology) | Lee, Sunghak (Pohang University of Science and Technology) | Lee, Chang-Sun (Technical Research Laboratories, POSCO)
Recent linepipe steel is required to have enough deformation capacity through longitudinal direction at severe environments such as permafrost or seismic region, even though after anti-corrosion coating treatment in pipe. Under this background, X60 and X100 linepipe steels with high strain aging resistance have been developed. With thermodynamic calculation and pilot plant rolling, optimal chemical compositions were determined, and it was studied that the effects of hot rolling conditions such as finish cooling temperatures on strengths and uniform elongations after coating simulation. Mo, Ni, and V alloying elements were employed to obtain enough strength and improve uniform elongation by producing microstructures consisting of ferrite, bainite and MA constituent. Such microstructures were characterized by EBSD (electron back scattered diffraction) technique. Pipes with 1m length were manufactured with an UOE simulator which can do U-ing, O-ing and expansion at the same machine. After pipe forming, coating simulation to evaluate strain aging characteristics of pipes was performed.
This paper presents an experimental study on the influence of wetting and drying on matric suction and moisture content of unsaturated compacted cohesive soils. Three as-compacted states and three levels of compaction energy of soil samples were investigated. Test results show that water content increases upon wetting and results in significant matric suction reduction. The effects are the opposite upon drying. In addition, the effects of as-compacted state and the compaction energy also warrant careful consideration. The matric suction appears to be a sensible parameter to evaluate the effects of wetting and drying of unsaturated compacted soils. However, further study is warranted for engineering application.
The purpose of this study is to propose the simulation method of a small ship’s motions in wash wave. Authors have proposed a reproduction method of wash wave by multi-segmented wave generators which are controlled by using computed results of CFD. Moreover, three dimensional numerical wave tank (3D-NWT) which represents a model basin and multi-segmented wave generators has been developed to simulated wash wave.
In this study, ship motions in wash wave were simulated in 3D-NWT and the simulated results were compared with the experimental results which were carried out by using the reproduction method of wash wave by wave generators.
Limited to the depth of the waterway and the height of the crossing river bridges, flat and small draught with double-tailed ship become the preferred type for the ocean going river-sea ships. In order to satisfy this demand, a shallow draft flat container ship with large openings and big B/D ratio (B/D>2.5) was designed beyond the specification of CCS. When sailing to sea, this flat ship would face serious nonlinear wave loads, which have great effects on hull-girder bending moments and fatigue damage. In the present paper, the wave-induced vibrations, such as whipping and springing, of the latest flat river-sea link ship were investigated experimentally. A backbone beam segmented model was used in the experiments with the focus on springing induced vertical bending moments, for the model travelling in regular head waves with different load conditions. In addition, higher order harmonics vertical bending moments are also extracted from the experiments. The distinguish methods on the springing responses, as well as the different high order springing were proposed. The contributions from these nonlinear wave-induced vibrations were discussed. In the meanwhile, the comparison of ultimate vertical bending moments between model test results and design rules of CCS were discussed.
The long wave caused by earthquake, landslide or volcanic eruption can be propagated over the global ocean. The 1883 Krakatau volcanic eruption has generated a destructive tsunami higher than 40 m on the Indonesian coast where more than 36 000 lives were lost. Sea level oscillations related with this event have been reported on significant distances from the source in the Indian, Atlantic and Pacific Oceans. The 2011 Tohoku earthquake triggered extremely destructive tsunami waves which propagated over the Pacific Ocean, Atlantic Ocean through Drake Passage and Indian Ocean respectively. These transoceanic tsunamis are propagated to Antarctica and the impact of 2011 tsunami waves on the icebergs in Sulzberger is captured by satellite images. The worldwide propagation of the tsunami waves is studied numerically using two conventional models: ray tracing method and two-dimensional linear shallow-water model.
In 2010 the Newcastle Port Corporation replaced a number of tubular mild steel piling after 33 years of service on the New South Wales Pacific Ocean coast due to heavy localized corrosion attack. Four of these tubular pilings were taken to the University of Newcastle for investigation. This paper reports on multiple longitudinal cross section loss measurements which allowed for statistical analysis of the variability of corrosion loss at different elevations. The statistical results are unique for such long-term exposures and are of major importance for structural reliability analyses of similar marine infrastructure assets. A pattern consistent with so-called accelerated low water corrosion was observed, suggesting microbiological attack at some point in time.