bluuebunny/crossref_metadata_2025 huggingface dataset:
DEMAND ANALYSIS OF PARKING AT MACHAP NORTHBOUND REST AND SERVICE AREA
Authors: Abd Wahab Muhammad Syimir , Ramli Izzul , Hassan Sitti Asmah , Hainin Mohd Rosli , Minhans Anil
Published: October 2015

Transportation planners need background information of parking generation in order to propose new developments and to predict changes in the parking generation. Most common factors on which the parking generation depends are gross floor area, number of staff employed at a facility, number of beds, etc. Unfortunately, in western as well as Asian countries including Malaysia, there is very little information on the parking generation for roadside rest areas. The parking generation of expressway rest area in Malaysia is believed to vary with time of the day, day of the week and depends on at least one or a few significant parameters. One of the factors influencing the parking demand is the prevailing vehicular volume on the major road, (North-South expressway). Therefore, this study was conducted to determine the effect of vehicular volume on major road on parking demand at Rest Area. The trend of parking demand was conducted at Machap Northbound Rest Area located at North-South Expressway for 4 different days to allow significant variations of traffic volumes. The guidelines of the parking generation by ITE were followed while collecting the parking demand data. The main parameter used in this study was the vehicular volume on the major road, North-South (expressway). The study was conducted on different days to allow significant variation of traffic volumes. It was found that the traffic volume on the major road can be used as a predictor to the parking demand at rest areas. The linear regression between vehicle volume on major road and parking demand showed significant relationship with R2=0.9522. The finding obtained in this study was based on a constrained duration of study at one site, Machap Northbound Rest Area. Further investigation will be conducted at a few locations of rest areas for a better insight on the effect of the parameter to the parking demand.
UNDERSTANDING THE NEIGHBOURHOOD CHOICE DECISIONS OF MOVERS: AN ANALYSIS OF FOCUS GROUP DISCUSSIONS
Authors: Sultan Zahid , Moeinaddini Mehdi , Asadi-Shekari Zohreh , Shah Muhammad Zaly
Published: October 2015

Using a qualitative methods approach, this study explores the key factors that influence household neighbourhood choice. Three newly developed residential neighbourhoods have been studied to examine resident decision making around their neighbourhood preferences. Four focus group (n = 4) discussions with 29 individuals who were recent movers to the study areas were conducted to examine the reasons behind neighbourhood choice and the needs of the household. The results revealed that household neighbourhood choice decisions were multi-faceted and complex. The key findings can be classified into six categories: safety, residential environment, neighbourhood facilities, accessibility, economic and demographic factors. Residents emphasised that the combination of land-use and transportation planning may be one important part of multi-layered solutions to improve quality of life in residential neighbourhoods.
AN EXPERT SYSTEM TO REMEDY CONCRETE IMPERFECTIONS AND THEIR EFFECTS ON RIGID PAVEMENTS
Authors: Mosa Ahmed Mancy , Ismail Norfarah Nadia , Md. Yusoff Nur Izzi , Mubaraki Muhammad Ali , Memon Naeem Aziz , Taha Mohd Raihan , Hainin Mohd Rosli
Published: October 2015

Imperfections of plastic concrete can cause severe deteriorations in rigid pavements surface and structure and reduce its life and serviceability. Diagnosing these imperfections, identifying their causes, and applying effective remedies early can prevent costly repairs in rigid pavements. However, if these imperfections are not remedied in correct time, the deteriorations in rigid pavements shall be reminded as soon as possible to avoid worsening the pavement condition. This domain involves diagnostic nature which suitable to be modelled as an expert system to help practicing engineers to identify the causes of the problems and their expected effects on pavement as well as applying suitable remedies. This paper presents the stages of development of an expert system in this domain. The development process includes knowledge elicitation, knowledge representation, knowledge coding, system validation, verification and evaluation.
A REVIEW OF UTILIZATION OF COCONUT SHELL AND COCONUT FIBER IN ROAD CONSTRUCTION
Authors: Lay Ting Tay , Putra Jaya Ramadhansyah , Abdul Hassan Norhidayah , Yaacob Haryati , Sri Jayanti Dewi
Published: October 2015

This paper provides a review of utilization coconut shell and coconut fiber in road construction. Coconut shell and coconut fiber are new waste materials used in highway industry. Some studies showed that coconut fiber can increase the stability, skid resistance and resilient modulus while coconut shell can improve the indirect tensile strength and static creep behavior of the modified asphalt pavement. In contrast, coconut fiber does not improve the fatigue life of the modified bituminous mixes. In general, the previous research illustrates that coconut shell and coconut fiber significantly improves the engineering properties of asphalt mixtures when mixed with modified bitumen.
A MULTIVARIATE METHODOLOGY FOR DETERMINING THE OPTIMAL HIGHWAY ALIGNMENT CANDIDATE BASED ON GEOGRAPHIC INFORMATION SYSTEM AND ANALYTIC HIERARCHY PROCESS
Authors: Mohd Yunus Mohd Zulkifli , Che Puan Othman , Sajjadi Seyed Mahdi
Published: October 2015

Research on highway alignment optimization has been quite intensive over the last two decades. Determining the best candidate for highway alignment is one of the most complex highway design stages due to the different effects of various parameters. Hence, in the present study, Analytic Hierarchy Process technique and Geographic Information System are proposed to determine the best highway candidate with special focus on the constraint, cost and safety criteria. The methodology presented in the current research is not limited to the constraint, cost and safety criteria but can be extended to other criteria. This methodology has been implemented on a case study region in northwestern of Iran, and therefore the constraint, cost and safety criteria have been obtained for the case study conditions. The final result of the current paper indicates that the optimal highway candidate obtained with the proposed methodology can concurrently satisfy all relative parameters in highway alignment optimization based on their impact.
EVALUATION OF SCENE PARAMETERS FOR OPTIMUM PERFORMANCE OF LOCALIZATION USING KINECT
Authors: Ilias Bukhari , Abdul Shukor Shazmin Aniza , Yaacob Sazali , Adom Abdul Hamid , Haja Hussain Mohd Firdaus
Published: October 2015

The needs of having locations identification are so important in this technological era. Locations identification has been implemented in so many areas nowadays. The challenge in this system is to identify location in real-time. Here, real-time refers to the process of capturing the location and recognize it at the same time. This research proposes a location identification system using Kinect, which is a high speed vision sensor that has been used for Xbox 360 video games. This research is to evaluate the optimum image detection distance, image size and processing time in identifying the locations that have been trained. The algorithm uses the Point Matching Features from the MATLAB software. From here, features are generated from both real time and training images being compared and the matching points between them will be used to identify the locations.
THE DYNAMIC EFFECTS OF PIEZOELECTRIC ACCELEROMETER ON THE STABILITY OF AN ACTIVE VIBRATION CONTROL SYSTEM
Authors: Ab. Rahim Muhajir , Ahmad Sa’ad Fathinul Syahir , Zakaria Ammar
Published: October 2015

The main purpose of this work is to study the dynamic effects of a piezoelectric accelerometer in an active vibration control system. The analysis is focused on the stability based on Nyquist stability criterion. This is done by deriving the overall open-loop system transfer function for a single-degree-of-freedom system which includes the sensor dynamics into the equation. The polar plot results show that the system is only unconditionally stable for acceleration, but is conditionally stable for velocity and displacement feedback control.
CONSTANT AMPLITUDE SPECTRUM OF THREE COACHES TRAIN AND CYCLIC COUNTING ON PRESTRESSED CONCRETE SLEEPERS (PCS)
Authors: Fazlan R. Mohd Ikmal , I. Sharul Nizam , A.B. Afidah , H. Siti Hawa
Published: October 2015

The raw strain data collected from Keretapi Tanah Melayu Berhad (KTMB) railway are in variable amplitude. This paper discovers how the variable amplitude data can be changed to the constant amplitude data. It is found that the raw strain data is not suitable for fatigue and strength testing on Prestressed Concrete Sleepers (PCS). Apart from that, the most suitable method in determining the numbers of cycles is Rainflow Cycle Counting Method. Through rainflow cycle counting method, the number of cycles is determined. The numbers of cycles are used to simplify the laboratory test such as fatigue and strength test for the PCS. The frequencies of dynamic loading test on the PCS are set based the numbers of cycles. The constant strain data are also converted into constant loading data using the relationship of stress-strain and loading-stress. Constant amplitude loading will again simplify the laboratory testing. The goal is to show that the designs used in PCS are appropriate based on current loading demand. Then, a comparison of constant amplitude data is made between different numbers of coaches and freight train. The maximum data from the comparison shows that the higher loadings are obtained from freight train.
THERMAL CONDUCTIVITY, COMPRESSIVE STRENGTH AND WATER ABSORPTION OF RECYCLED COCONUT FIBRE AND CRUSHED CLAY BRICK MASONRY
Authors: Krishnamoorth Renga Rao , David Thevaneyan Krista
Published: October 2015

This study aims to investigate the thermal conductivity, compressive strength and water absorption analysis of recycled masonry bricks using coconut fiber and crushed clay bricks as a partial sand replacement to create a green building material. The variable ratios of coconut fiber were considered and 10 specimens per sample were manufactured manual process using hand. Four (4) series of brick mix design from the total weight of the sand with different levels of coconut fiber and crushed clay brick replace half of the sand was created as irregular mixes comprises of 0%, 2%, 4% and 6% of coconut fiber. Overall, the use of coconut fiber and crushed clay brick as a partial sand replacement reduce the brick thermal conductivity. Thermal properties were measured based on the transient line heat source method using a KD2 Pro thermal properties analyzer. The suitable percentage of partial sand replacement for sand-cement brick using coconut fiber in this study was 4% and 50% of crushed clay brick after compared to commercial brick. The average sample of 4% coconut fiber was 0.532 W/mk of thermal conductivity and 18.74MPa compressive strength with density of 1716.28 kg/m3. In short, the thermal insulation potential of coconut fiber and crushed clay brick is highly promising for commercial development in Malaysia.
THE STUDY OF VEGETATION EFFECT ON WIRELESS STREAMING VIDEO FOR AGRICULTURAL MONITORING
Authors: Ramli Mohd Fitri , Kamarudin Latifah Munirah , Ndzi David Lorater , Harun Azizi , Cynthia Turner Jamie Siregar , Hassan Najmudin , Md. Shakaff Ali Yeon , Jaafar Mahmad Nor , Zakaria Ammar
Published: October 2015

This paper presents the study of video streaming over wireless channel based on experimental measurements in the presence of fading caused by the physical environmental. The emulation of video streaming file through wireless channel is measured using IxChariot software from Ixia. The obtained emulation of signal quality from the video streaming file was measured in terms of network throughput, RSSI and packet loss. The results show the credibility of wireless network for streaming video file in agricultural area. The statistical results show that there is significant negative effect of physical environmental condition on wireless video streaming and received video quality.
PERFORMANCE OF WAVELET BASED MEDICAL IMAGE FUSION ON FPGA USING HIGH LEVEL LANGUAGE C
Authors: Umapathy K. , Balaji V. , Duraisamy V. , S. Saravanakumar S.
Published: October 2015

In this paper presents the implementation of wavelet based medical image fusion on FPGA is performed using high level language C. The high- level instruction set of the image processor is based on the operation of image algebra like convolution, additive max-min, and multiplicative max-min. The above parameters are used to increase the speed. The FPGA based microprocessor is used to accelerate the extraction of texture features and high level C programming language is used for hardware design. This proposed hardware architecture reduces the hardware utilizations and best suitable for low power applications. The paper describes the programming interface of the user and outlines the approach for generating FPGA architectures dynamically for the image co-processor. It also presents sample implementation results (speed, area) for different neighborhood operations.
A REVIEW ON ENHANCING HUMAN-MACHINE-ENVIRONMENT INTERFACE FOR POSTURA MOTERGOTM
Authors: Wan Fauzi Wan Muhammad Syahmi , Omar Abdul Rahman , Jaafar Roseleena , Nor Ma’arof Muhammad Izzat , Rashid Helmi
Published: October 2015

In this era of critical traffic congestion, motorcycles have become one of the popular go-to vehicles. Recently, there are several motorcycle simulators that was developed by several group researchers around the world due to the statistics of motorcycle road accidents globally alarming. They are developed for 2 different purposes which are as testing on prototype models prior to mass production and also as conducting a study on human skills and behaviour in specific motorcycling conditions. The aim of this study was to review several issues detected with respect to the currently available motorcycle simulators. In addition, a special attention was given to a motorcycle test rig named the Postura MotergoTM. The Postura MotergoTM is a new revolutionary motorcycle test rig which was developed based on Riding Posture Classification (RIPOC) system. However, it is noticeable that the current design of Postura MotergoTM could be improved to further elevate users’ experience. Other than adding to better fidelity of the motorcycle test rig, further improvements with respect to design, functionality and users’ experience would ensures the design longevity and overall cost effectiveness provided by the particular motorcycle test rig. Thus, enables the particular motorcycle test rig to contribute to various motorcycle ergonomics researches in the near future. Such matter would then be hope to ultimately aid in reducing the global motorcycle road accident statistics.
EFFECT OF DIAMETER AT BREAST HEIGHT OF LEUCAENA LEUCOCEPHALA ON BIO CHAR PRODUCTION IN TUBE FURNACE PYROLYSIS
Authors: Sayed Idrus Syed Muhammad Azlan , Abd Rahman Norazah , Matali Sharmeela , Abdul Manaf Shareena Fairuz , Bin Elham Puad
Published: October 2015

Renewable energy produced from biomass is a green way to reduce the greenhouse effect. Fast-growing wood species, as the energy source, create independent and fast harvesting cycle for energy fuel stock.  The aim of this study was to determine the effect of tree diameter at breast height (DBH) of a local wood species i.e. leucaena leucocephala, on char yield during pyrolysis. The calorific value (CV) of bio char was also determined in order to analyse the bio char product produced by pyrolysis process. The tree samples were classified into three DBH i.e. 4, 8 and 12 cm and only tree stem was selected for pelletization. The wood pellets were pyrolyzed at 300, 400, 500, 600 and 700 °C with 40 °C/min of heating rate and holding time of 30 min in inert condition. The largest difference percentage of bio char yield production is only 1 % while the largest difference of CV is 0.7 MJ/kg which happened at temperature 300 °C. In this study, it was found that any DBH does not give any significant effect to the production of bio char as well as its CV.
EXPERIMENTAL INVESTIGATION ON THE MAXIMUM AXIAL FORCE OF AN ALUMINUM SQUARE COLUMN
Authors: Lukman Hafizi , Ab. Ghani Amir Radzi , Hashim Hafizan , Bin Zulkefli Mohd Adzureen , Mahat M
Published: October 2015

Energy absorption is one of the characteristics that must be included especially in transportation systems. This property dissipates kinetic energy during collisions. Normally, industries use thin wall structures because of their ease of fabrication, high performance, and low cost. This study determines the first peak force and energy absorption of an aluminum square column. The square columns prepared with various design patterns exhibited different results. The designs showed favorable results in terms of increasing the specific energy absorption and reducing the initial peak force. To achieve the project objective, this project conducted two types of analyses using INSTRON 3382 for the experimental analysis.
TRI-OBJECTIVE OPTIMIZATION OF CARBON STEEL SPOT-WELDED JOINTS
Authors: Ghazali Farizah Adliza , Berhan Mohamad Nor , Manurung Yupiter HP , Salleh Zuraidah , Abdullah Shahrum
Published: October 2015

The investigation was intended to optimize tri-objective of the welding parameters on tensile-shear (TS) strength, Fusion Zone (FZ) size and Heat Affected Zone (HAZ) size development in resistance spot welding (RSW) process of similar sheet metals joint. The experimental studies were conducted on varying weld time, electrode force and weld current for 1.2mm thickness of low carbon steel. The experimental tests, conducted according to the settings of process parameters were carried out according the L9 Taguchi orthogonal array in randomized way. The optimum process parameter for tri-objective was obtained using multi signal to noise ratio (MSNR) and further analyzed the significant level using analysis of variance (ANOVA). Response Surface Method (RSM) was employed to developed second order model at optimal welding parameters. The confirmation tests results demonstrate that the tri-objective Taguchi method used to optimize the welding parameters and enhance the welding performance is practical and effective in RSW process.
THE EFFECT OF LAMINATION SCHEME AND ANGLE VARIATIONS TO THE DISPLACEMENTS AND FAILURE BEHAVIOUR OF COMPOSITE LAMINATE
Authors: Samsudin Azizul Hakim , Mahmud Jamaluddin
Published: October 2015

This paper aims to investigate the effect of lamination scheme and angle variations to the displacements and failure behaviour of composite laminate. Finite element modelling and analysis of symmetric, anti-symmetric and angle-ply Graphite/ Epoxy laminate with various angles of fiber orientation subjected to uniaxial tension are performed. Maximum Stress Theory and Tsai-Wu Failure Criteria are employed to determine the failure load (failure index = 1). Prior to that, convergence analysis and numerical validation are carried out. Displacements and failure behaviour of the composite laminates (symmetric, anti-symmetric and angle ply) are analysed. The failure curves (FPF and LPF) for both theories (Maximum Stress Theory and Tsai-Wu) are plotted and found to be very close to each other. Therefore, it can be concluded that the current study is useful and significant to the displacements and failure behaviour of composite laminate.
Steel Lazy Wave Risers From Turret Moored FPSO for Deepwater Harsh Environment
Authors: Orimolade Adekunle Peter , Karunakaran Daniel , Meling Trond Stokka
Published: October 2015

Steel catenary risers (SCRs) have found greater applications in deep and ultra-deepwater developments. However, the deployment of SCRs in conjunction with a high motion deepwater floater such as the Floating Production Storage and Offloading (FPSO) system faces significant challenges due to their high motion characteristics, especially in harsh environmental conditions. The challenges posed by FPSO’s high motion characteristics include severe dynamic response on the SCRs and poor fatigue performance at the top section and the touchdown point (TDP) area. A number of alternative configurations of the SCR can be employed to decouple the FPSO’s motion from the SCR, thereby improving performance, and this include the steel lazy wave riser (SLWR) configuration. The lazy wave is achieved by introducing buoyancy modules along some lengths of the riser.

In this work, a suitable SLWR configuration for deployment in conjunction with a turret moored FPSO was developed for a typical deepwater offshore West of Shetland environmental conditions. The optimum configuration is a low lazy wave configuration; this was achieved after several analyses using ORCAFLEX software program. In determining the optimum configuration, consideration is given to the SLWR sag and hog bend heights, the net buoyancy force, the buoyant section length, and the hang-off angle, among others.

The extreme response, considering a combination of 100-year wave with 10-year current was satisfactory; the maximum stress was below the allowable stress level, and the maximum DNV utilization was less than unity, indicating a safe design. The wave-induced fatigue damage was calculated using a total of 216 load cases, resulting from 12-wave directions, and the wave-induced fatigue performance was satisfactory, with the minimum fatigue life observed at the riser’s TPD. Fatigue damage resulting from vortex induced vibration (VIV) was calculated considering currents in the in-plane and the out-of-plane directions to the riser, with a total of 22 load cases. The VIV fatigue performance was not satisfactory, and therefore fairings and strakes will be introduced to some lengths of the SLWR to suppress VIV. Detailed sensitivity studies also showed how the configuration can be further optimized.

Overall, the results of this study showed that, the SLWR is a suitable riser concept for deployment from a turret moored FPSO, in deepwater, harsh environmental conditions such as offshore West of Shetland. The riser can be installed using Reeled-Lay installation method. The installation can be performed using pre-lay, abandonment, and recovery, as this offers advantages over the direct transfer approach.
Application of a Statistical Pattern Recognition Technique for Integrity Monitoring of Umbilicals and Subsea Flowlines
Authors: Mosavi Amir A. , Haverty Kevin
Published: October 2015

Evolution of reliable sensing systems which can survive, measure, and transfer data in the harsh environments has resulted in a tremendous increase of their application for integrity monitoring of different subsea components/structures in the past decade. Most of these sensory systems are designed for periodical and long term data measurement from their respective structures. However, they do not directly measure the degradation process. Instead, they intend to measure the structural responses which are affected by the degradation processes. Therefore, the raw measured structural responses should be further processed to identify the potential degradation either caused by aging or during an extreme event. Despite the significant evolution of the sensory systems, less attention has been paid to the data processing methodologies for the integrity monitoring. Different statistical pattern recognition methodologies have been successfully developed and used in the aerospace, automation and civil engineering industries for the purpose of Structural Health Monitoring (SHM). This study demonstrates application of a statistical pattern recognition technique to identify a potential damage in an umbilical line in Gulf of Mexico (GOM). Any potential damage in gas lift umbilical imposes serious environmental risk and shut-down period for production. The study uses sets of simulated sensory data to simulate the measured structural response of both intact and damaged umbilicals under different environmental loading conditions. In this regard, different sensor locations correspond to different Finite Element nodes along the length of the Umbilical. The damages are introduced simply by reducing the stiffness properties of the umbilical cross-section at hang off and touch down areas. The simulated strain time history data were pre-processed to potentially remove the effect of measurement noise and different loading. Damage sensitive features were extracted from the processed strain time history responses for intact and damage conditions of the umbilical under different environmental loadings. Autoregressive models were used for extraction of these damage sensitive features. The data from the intact conditions were used as the baseline data, and statistical analyses were performed to measure the variation of the damage features with respect to the intact condition of the umbilicals. The amounts of variations were investigated at the different sensor locations. The statistical measures were used as damage indices at different locations along the length of umbilical. Results show that the locations with large damage indices successfully corresponded to the areas with reduced stiffness properties. Although the proposed technique is implemented to monitor integrity of an umbilical, this technique can be used for risers and other flowlines to update near real time information about the integrity condition of these structures.
A Simple, Efficient, and High-Order Accurate Sliding-Mesh Interface Approach to Spectral Difference Method on Coupled Rotating and Deforming/Stationary Domains
Authors: Zhang Bin , Liang Chunlei , Yang Jingjing
Published: October 2015

In this paper, we present a novel sliding-mesh interface approach to the spectral difference (SD) method on coupled rotating and deforming/stationary domains. This approach is an extension of the previously reported method for coupled rotating and stationary domains for the flux reconstruction (FR) method [1]. The use of sliding-mesh interfaces not only allows us to study flows around freely rotating bodies but can also dramatically reduce grid twists on deforming domains with large-angle rotations. We test the accuracy of the solver on an inviscid flow, and it is found that the solver is high-order accurate on coupled dynamic grids with sliding-mesh interface. Simulation of viscous flow over a plunging and pitching airfoil is also carried out to verify the solver, it is seen that the solver is accurate and is very efficient in terms of computational cost. Finally, we apply the solver to study a two-dimensional vertical axis wind turbine at different Reynolds numbers. It is found that the turbine is efficient and extracts energy from the flows at high Reynolds numbers. This solver can also be applied to other problems, such as the aerodynamics of rotorcrafts, oscillating wing wind power generators.
Interaction Between Lateral Buckling and Propagation Buckling in Textured Deep Subsea Pipelines
Authors: Karampour Hassan , Albermani Faris , Major Peter
Published: October 2015

Novel analytical solution to lateral buckling of pipelines based on localization of buckle patterns is proposed. Finite element study is conducted on lateral buckling of a full length pipe. Analytical and FE results are compared and advantages of analytical solution to FE model are highlighted. Interaction between lateral buckling and propagation buckling of cylindrical pipe and textured pipe under transient load path are investigated.
Insights Into Sloshing Impact Pressures Through Level Set Modeling of Liquid Droplet Impacting a Wall
Authors: Repalle Nitin , Thiagarajan Krish P. , Kantharaj Murali
Published: October 2015

This research arose from the need to understand the behavior of impact pressure caused by droplets formed during liquid sloshing in a tank. The two phase problem of a cylindrical liquid droplet of diameter D surrounded by a lighter fluid medium, impacting at some angle on a solid wall is studied. The incompressible two-dimensional continuity and Navier Stokes equations are solved by a two-step projection predictor-corrector algorithm, with a third-order Total Variation Diminishing (TVD) Runge-Kutta method for time stepping. The interface of the droplet is tracked by the zero contour of a level set function, which is allowed to evolve over time. Numerical simulation of impact pressure was found to agree well with the measured pressures, in particular at lower droplet velocities where compressibility effects can be ignored. A parametric study was conducted with a droplet of diameter 0.01 m traveling at four different impact angles between 45–90°. Velocities from 3.0–6.0 m/s, corresponding to Reynolds numbers from 2.9E05–4.8E05, and Weber numbers 1.25E04–5.0E05 were considered. The simulated impact pressure maximum plotted against the normal velocity of incidence shows a power law type behavior that is quite insensitive to the density ratio of the two fluids. The relationship between the velocity of the sloshing wave front and resultant pressure obtained from an experiment was found to be well predicted by the power law relationship for the liquid droplet impact.
Measured Metocean Characteristics of Gulf of Mexico Hurricanes
Authors: Forristall George Z. , McConochie Jason
Published: October 2015

A wealth of Gulf of Mexico hurricane wind and wave data has been measured in recent years. We have constructed a database that combines HURDAT storm track information with NDBC buoy data for the years 1978–2010. HURDAT contains 141 storms for that period of which 67 had measured significant wave heights greater than 5 m. Industry measurements in Hurricanes Camille, Lili, Ivan, Katrina, Rita, Gustav and Ike have been added to the buoy data. We have used this data base to study the relationships between wind and wave parameters in hurricanes. Specifically, we have calculated regressions and equal probability contours for significant wave height and peak spectral periods, first and second moment periods, wave height and Jonswap gamma values, wind speeds and wave heights, and wave and wind directions. All of these calculations have been done for azimuthal quadrants of the storm and radial distances near and far from the storm center.
Forecasting Marine and Structural Integrity Parameters for Offshore Platforms
Authors: Prislin Igor , Jafarkhani Reza , Maroju Soma
Published: October 2015

Marine and structural integrity monitoring for offshore platforms is the cornerstone for managing operational risk and safety. Measuring platform responses and loads enables comparisons with design values thus ensuring that the risk does not exceed the designed limits. This paper discusses an advanced data management that is based on machine learning, a set of specialized computer programs that can learn and generalize the platform responses from measured data. The programs should produce sufficiently accurate predictions in previously unseen cases. Examples provided in the paper address capabilities for forecasting the marine and structural integrity parameters.
ECA for Girth Welds of Offshore Pipelines: A Modified BS7910 Analytical Approach vs 3D FE Analyses
Authors: Bruschi Roberto , Leonzio Valerio , Ferrulli Angelo , Scarsciafratte Daniele , Torselletti Enrico
Published: October 2015

In the last decade new standards or revisions of existing guidelines have been launched on the subject. Among those, BS 7910 (now in edition 2013) [1] and DNV-OS-F101 (now in edition 2013) [2] are considered as reference in many world offshore districts of the Oil & Gas Industry.

What is peculiar in offshore pipelines with respect to pressure vessel or nuclear plants, for which an engineering criticality assessment (ECA) was first established, it is the fact that in many circumstances offshore pipelines exceed the elastic limit (global pipe bending is a primary stress that causes mainly membrane stress through the pipe wall). This implies the extension of a stress based ECA into a strain based ECA, further including the bi-axial state of stress, caused by the presence of internal pressure and hoop stresses.

An important step of ECA is the definition of loads and load effects at pipe girth weld, from global applied loads on the pipeline to the local effects at the crack.

Finite elements (FE) are currently used to develop the relevant bending moment stress vs. strain relationship for the given pipe diameter, wall thickness and materials, both parent pipe and weld. Related longitudinal stress distribution on the pipe cross section without flaws in the weld is calculated for different pipe life stages (installation, pressure test and operation). The calculated global (or far from the flaw) longitudinal stress distribution is an input for the ECA analysis.

For this aspect the new DNV OS-F101 (2013) has reviewed the appendix A requiring the use of 3D FE analyses to account for the effect of the internal pressure on the Crack Driving Force (CDF).

In this paper it is discussed an analytical approach both to assess the pipeline strength in presence of flaws in the girth welds of offshore pipelines and to define defect acceptance criteria for specific new projects. The approach follows the framework of BS7910 and of DNV OS-F101 and includes load conditions under both installation and operation. In particular specific 3D FE analyses are presented to enforce the applicability of the proposed analytical approach.
Computation of Nonlinear Hydrodynamic Loads on Floating Wind Turbines Using Fluid-Impulse Theory
Authors: Chan Godine Kok Yan , Sclavounos Paul D. , Jonkman Jason , Hayman Gregory
Published: October 2015

A hydrodynamics computer module was developed to evaluate the linear and nonlinear loads on floating wind turbines using a new fluid-impulse formulation for coupling with the FAST program. The new formulation allows linear and nonlinear loads on floating bodies to be computed in the time domain. It also avoids the computationally intensive evaluation of temporal and spatial gradients of the velocity potential in the Bernoulli equation and the discretization of the nonlinear free surface. The new hydrodynamics module computes linear and nonlinear loads — including hydrostatic, Froude-Krylov, radiation and diffraction, as well as nonlinear effects known to cause ringing, springing, and slow-drift loads — directly in the time domain.

The time-domain Green function is used to solve the linear and nonlinear free-surface problems and efficient methods are derived for its computation. The body instantaneous wetted surface is approximated by a panel mesh and the discretization of the free surface is circumvented by using the Green function. The evaluation of the nonlinear loads is based on explicit expressions derived by the fluid-impulse theory, which can be computed efficiently.

Computations are presented of the linear and nonlinear loads on the MIT/NREL tension-leg platform. Comparisons were carried out with frequency-domain linear and second-order methods. Emphasis was placed on modeling accuracy of the magnitude of nonlinear low- and high-frequency wave loads in a sea state. Although fluid-impulse theory is applied to floating wind turbines in this paper, the theory is applicable to other offshore platforms as well.
Dynamical Analysis of Drill Bit With Ultrasonic Vibration
Authors: Zhao Dapeng , Sangesland Sigbjørn
Published: October 2015

Based on the bit-rock interaction laws, a simple nonlinear 2-dofs mass-spring model is developed to analyze the dynamic cutting process with normal ultrasonic vibration excitation. The study presents a single cutter used in Polycrystalline-Diamond-Compact (PDC) drill bits. Using the 4th Runge-Kutta’s algorithm, numerical simulation found that ultrasonic vibration-induced contact deflection and even loss of contact. The contact friction between the rock and wear-flat (wear surface), which relates to the reaction force, is therefore reduced. This will reduce the wear on the cutter and the force needed to cut the rock. This indicates that the average reduction of friction induced by ultrasonic vibration can be explained by decreasing the average normal force on the cutter-rock wear-flat, rather than changing the friction coefficient.
Strength Assessment of Type ‘C’ LNG Fuel Tanks
Authors: Wang Bo , Shin Yung-Sup , Norris Eric
Published: October 2015

The objective of this study is to present a complete procedure for the strength evaluation of Type ‘C’ liquefied natural gas (LNG) fuel tanks. The fuel tank is designed independent of the ship’s hull and consists of double tanks with inside and outside supports. The inner tank, which holds the LNG cargo, is held within the outer tank using strap and cone supports at two ends. The outer tank is kept in vacuum and the space between the inner tank and the outer tank is filled with insulation materials. There are two saddle supports connecting the outer tank to the hull. The major components of the fuel tank in FE model include inner tank, outer tank, strap support, cone support, as well as two saddle supports. All these structures are designed to withstand all ship and service design loads. The inner tank is subjected to the internal pressure and the outer tank is loaded by external pressure. Due to the ship motion, the inertia forces caused by cargo accelerations will be applied to the tank structure. In this study, Finite Element (FE) analyses were performed in various load cases in which load components include design internal/external pressures, longitudinal / transverse / vertical accelerations, and gravity. Additionally, a Computational Fluid Dynamics (CFD) sloshing simulation on the fuel tank with splash baffles was performed to determine sloshing loads. Accidental load cases, including collision and flooding, were also considered in the structural analysis. Meanwhile, a buckling analysis on the evacuated outer tank was conducted to identify the critical collapse pressure. Acceptance criteria corresponding to yielding and buckling failure modes have been detailed for the strength evaluation of the Type ‘C’ LNG fuel tank. Thus, a complete procedure has been developed for the structural integrity assessment of tank and supporting structures for Type ‘C’ LNG fuel tanks.
Assessment of the Commercial and Safety Limitations of High Capacity Reel Drive Systems vs Under-Rollers for Reel-Based Product Installation
Authors: Dale Nicholas
Published: October 2015

Flexible products are becoming ever longer and larger to cope with the technical demands of deepwater fields and tie-backs. The implication of this being that product reels are becoming larger, heavier and more complex to manage during installation and recovery operations.

This paper explores the current limits of reel-based installation equipment evaluating the implications of the increased deck footprint, the necessity for modularity from an equipment repositioning and handling perspective and the limitations placed on vessel selection and vessel stability during installation. The safety, engineering, operability and commercial factors associated with each area of development are analysed to produce a complete snapshot of where the current industry limits lie and how far we can push the envelope for this method of installation.

Specific equipment focus is placed on reel-drive systems which are the industry standard and under-roller systems which, although represent a more dated technology, are still accepted in certain regions for flex lay operations.
Effects of Highly Ductile Steel on the Crashworthiness of Hull Structures in Ship to Ship Collision
Authors: Yamada Yasuhira , Ichikawa Kazutoshi , Kamita Kenji , Tozawa Shigeru , Inami Akinori , Suga Hayato , Fujita Hitoshi , Senga Yoshihiro , Arima Toshiro , Murakoshi Satoshi
Published: October 2015

In order to preliminary investigate effect of HDS (Highly Ductile Steel) on the crashworthiness of struck ship, a series of large scale 3-dimensional ship-ship collision analysis are carried out using the non-linear finite element code LS-DYNA. A very large crude oil carrier (VLCC) is assumed to collide with midship region of another double hull (D/H) VLCC in right angle (90 deg.). Two collision points for the struck VLCC are assumed. One is between Swash Bulkhead (S.BHD) and Oil Tight Bulkhead (OT.BHD), the other is just on S.BHD. Damage extent and total absorbed energy until oil cargo tank ruptures in the case of HDS are compared with those in the case of conventional material. Critical colliding speed (VB,cr) is also compared. Effects of HDS on absorbed energy and VB,cr are discussed in detail. It can be found energy absorption by inner shell (IS) rupture with using HDS is about 2–3 times larger than that with using conventional It is also estimated that IS rupture does not take place when a striking ship collides in less than 8kt in the case of using HDS although a critical striking velocity in the case of conventional bow is about 4–5kt.
Met-Ocean Conditions Influence Over Floating Wind Turbine Energy Production
Authors: Martini Michele , Guanche Raúl , Armesto José A. , Losada Iñigo J.
Published: October 2015

The operation of a floating wind turbine may be severely affected by met-ocean conditions. In harsh climates, platform motions might exceed their safety limits and thus force the machine shutdown. It is here proposed a methodology for evaluating the effect of met-ocean conditions on the long-term energy production and dynamic response of such machines.

Given a sample wind turbine, located off the coast of Santander, Spain, met-ocean data are extracted from reanalysis databases for a twenty years lifespan.

The behavior of the wind turbine is simulated in the time domain for a subset of 500 hourly conditions, selected using a maximum dissimilarity algorithm (MDA), to reduce the computational effort. Results regarding floating platform motions are then interpolated for the whole set of data using radial basis functions (RBF).

Tower inclination and hub acceleration are selected as relevant operating parameters. When one of them exceeds its safety threshold, the machine is supposed to be stopped. If no stops are considered, the capacity factor is 39%, while imposing more restrictive tolerances results in a non-linear decrease of the energy yield.

This approach can be helpful in determining a good tradeoff between energy production and reliable operation, bridging the design and operational phases of the project.
Distributed Damping of Tsunamis
Authors: Javanmardi Mohammadreza , Alam M. Reza
Published: October 2015

Tsunamis are a major threat to coastal communities. One of the ways to avoid tsunami disasters is to use breakwaters to attenuate the incident tsunami energy. The incident tsunami energy is expected to be dissipated by induced wave breaking in the shallow water over the structure peak.

In this paper, a new method to attenuate the tsunami energy is described and investigated. This new concept dissipates tsunami energy by implementing small barriers into the water before the tsunami reaches the shore. The interaction of tsunami-like solitary waves with new submerged barriers has been investigated and their performance was compared with that of conventional breakwaters. We found that the new structure can be used as a tsunami wave attenuator.
Rationalization of Toughness Requirements for Subsea Forgings
Authors: Bahrami Amir , Zettlemoyer Nick , Vangeertruyden William
Published: October 2015

The oil and gas industry has historically relied on experience-based, toughness target values when qualifying various components, including subsea forgings. However, this experience has been mainly with lower strength grades of steel and modest thicknesses. The increasing demand for higher yield strength steels or thicker cross sections to meet design needs necessitates the development of adequate toughness requirements to ensure safe operation of these components. The approach presented here involves utilization of fracture mechanics assessment methods to develop a more rationalized basis for toughness requirements. The guidance developed in the paper is related to critical components, both static and those that are fatigue-sensitive. And the fatigue-sensitive requirements can be applied to weld procedure qualification.
Real Time Estimation and Prediction of Wave Excitation Forces on a Heaving Body
Authors: Ling Bradley A. , Batten Belinda A.
Published: October 2015

Wave energy converters (WECs) face many technical challenges before becoming a cost-competitive source of renewable energy. The levelized cost of electricity could be decreased by implementing real-time control strategies to increase average power produced by a WEC. These control strategies typically require knowledge of the immediate future excitation force, caused by the waves. This paper presents a disturbance prediction methodology that is independent of the local wave climate and can be implemented on a wide range of devices.

A time-domain model of a generic heaving WEC is developed with the Cummins equations. The model is simulated with measured water surface elevation data collected off the Oregon Coast. A simplified linear frequency-invariant state-space model is used in conjunction with a Kalman filter to estimate the current excitation force with measurements of the WEC’s motion. Future excitation forces are then predicted multiple steps in the future with a recursive least squares filter. The results show this approach makes accurate predictions of excitation force over short time horizons (up to 15 seconds), but accurate predictions become infeasible for longer horizons.
Metal Loss: Corrosion Defects Qualification and Structural Integrity Assessment
Authors: Gentile Manuela , Laudonia Ciro Antonio , Marchionni Lorenzo , Parrella Antonio , Vichi Roberta , Vitali Luigino
Published: October 2015

The management of the flow availability in presence of corrosive fluids may considerably impact on CAPEX and OPEX of offshore pipelines. A correct approach starts from the preliminary phases of a project, with the selection of the most appropriate material in relation to the nature of the corrosive fluids and expected degradation mechanisms (i.e. general corrosion, localized or mesa corrosion and pitting). The construction phases include measures that allow meeting welding requirements and safe guarding the integrity of the line-pipe. The operation shall account for the control of process parameters and transported fluid composition.

In the upcoming future offshore pipeline and field development projects, challenging operating conditions in deep/ultra-deep waters means that increasingly careful considerations on the effect of metal loss: corrosion leading to local loss of material may cause a potential pipeline failure under the additional effect of functional and environmental loads, in particular the high external pressure and applied bending moment. The assessment of the structural integrity depends on the type and accuracy of available measurements. In presence of corrosion patterns and accordingly to existing standards (DNV RP-F101, ASME B31G, API 579, BS 7910) the assessment might be unduly conservative; further the presence of important combined loads is not fully covered by standard assessment format.

The use of FEM numerical lab can help the evaluation of the residual strength and deformation capacity of the pipeline affected by corrosion, leading to a quite-deterministic characterization of pipeline strength capacity at design stage and in operation. Several studies (both theoretical and experimental) available in the open literature faced this issue and their findings support the proposed analysis methodology. Recently full scale tests have been conducted by the relevant Oil & Gas industry companies (such as Statoil and ENI) and the obtained results have been used for the FE Model calibration and validation of corroded pipelines. Herein an application is presented in order to understand and appreciate the proposed methodology performance in corroded pipeline assessment.