bluuebunny/crossref_metadata_2025 huggingface dataset:
CRACK BEHAVIOUR OF PRE-TENSIONED (PRT) CONCRETE BEAM AFTER RETROFITTED WITH CFRP SHEETS
Authors: Suliman Nurul Huda , Abu Bakar Afidah , Hamzah Siti Hawa , Ahmad Nur Amirah
Published: October 2015

This study concentrates on crack that occurs at PRT beam which the beam then retrofitted with carbon fibre reinforced plastic (CFRP) sheets. The beam was tested to determine crack modes and ultimate capacity before and after retrofitted. The beam was tested under static test with displacement control of 0.009mm/sec. Once the first crack appeared, the beam was unloaded and took out for retrofitting process. The beam was loaded again to failure to evaluate the effect of CFRP on the behaviour of the long span beam. Therefore, the finding of this study will guide engineers and construction practitioners to further understand the effects of CFRP sheets used in long span beam in term of load capacity and crack behaviour after retrofitting work.
IMPROVEMENT OF SURFACE ROUGHNESS DURING TURNING OF PRE-HEATED MILD STEEL USING VOICE ACTIVATED ULTRASONIC WAVES
Authors: Patwari Anayet U , Habib Mohammad Ahsan , Chowdhury Md. S. I. , Neelav Afzal H. , Latif Md. Sharfat , Sunny T. M. M.
Published: October 2015

Surface roughness represents the dimensional accuracy of the finished product and is one of the most important quality parameters of the finished product. For improvement of the surface quality several techniques like magnetic field, ultrasonic assisted turning and so on has been introduced. Ultrasonically Assisted Turning has been one of the techniques which showed great promise. It is a hybrid technique based on superimposition of ultrasonic vibration on a movement of a cutting tool in turning process. In this paper, a new technique using the concept of voice activated mode generated ultrasonic smart waves has been proposed and adopted with an aim to improve average surface roughness of the preheated machined surface of mild steel. Externally voice activated ultrasonic sound waves were applied during turning process of preheated mild steel and its effect on average surface roughness was studied. Experimentations were carried out under different ultrasonic frequencies to determine the surface roughness to the best degree possible. The experimental results showed significant improvements in surface roughness in preheated machined products.
A STUDY ON THE EFFECT OF COLLAGEN FIBER ORIENTATION ON MECHANICAL RESPONSE OF SOFT BIOLOGICAL TISSUES
Authors: Fathi Farshid , Shahi Shahrokh , Mohammadi Soheil
Published: October 2015

Extensive research has been performed in the past decades to study the behavior of soft biological tissues in order to reduce the need for practical experiments. The applicability of these researches, particularly for skin, ligament, muscles and the heart, brings up its importance in various biological science and technology disciplines such as surgery and medicine. Softness and large deformation govern the behavior of soft materials and prohibit the use of small strains solutions in finite element method.In this work, the focus is set on a strain energy function which has the advantage of accurately representing the behavior of a variety of soft tissues with only a few parameters in a finite element approach. The numerical results are verified with a set of tensile experiments to demonstrate the performance of the proposed model. The parameters include the matrix and collagen bundles and their orientation. Different cases are analyzed and discussed for better prediction of different soft tissue responses.
THE INFLUENCE OF FEMORAL BALL SIZE ON THE RANGE OF MOTION THAT FULFILLS THE CRITERIA OF SAFE ZONE ORIENTATION ACETABULAR CUP
Authors: Abd Manap Muhammad Faris , Shuib Solehuddin , Romli Ahmad Zafir , Shokri Amran Ahmed
Published: October 2015

Dislocation and edge loading are significant issues highlighted due to the acetabular component orientation during total hip replacement(THR). This study aims to define the optimum acetabular cup orientation with the most suitable femoral ball size, thus eliminating the possible issue that may arise during postoperative surgery. A numerical approach by creating a single function that enables the calculation of the cup inclination (α) and the cup anteversion (β) with respect to range of motion are developed by using a programming language namely Matlab®. Three separate studies were done by having a head neck ratio of 2.33, 2.67 and 3.0, respectively. From these data, it is clear that the size of femoral head affects the area under range of motion at the bearing surfaces. A wide area under the graph resulted in a better and greater number combination of acetabular cup thus reducing the risk of dislocation and edge loading.
ISOLATION OF NANOCELLULOSE FROM JATROPHA WASTE: AN OVERVIEW
Authors: Mahadi Mahazmi Burhanuddin , Abd Rahman Norazah , Abdul Manaf Shareena Fairuz
Published: October 2015

Nanocellulose widely used as an additive to improve the quality of composite for medical appliances, electronic and many other applications. The structure can be found in a plant cell wall and established methods are needed for an isolation process. Biomass from plant is commonly selected for this process due to theirs abundance resources. Nanocellulose from jatropha plant will be thoroughly discussed in this paper where several isolation methods will be highlighted.
BEHAVIOR OF IMPLANT STABILITY DURING IMPLANT TREATMENT: IN VIVO STUDY
Authors: Genisa Maya , Rajion Zainul Ahmad , Shuib Solehuddin , Pohchi Abdullah , Mohamad Dasmawati
Published: October 2015

Implant stability is essential parameters that indicate the success of the implant treatment. However, the relation between implant stability, osseointegration and also remodeling process during that period is still unclear. This study was to evaluate the behavior of implant stability during implant treatment period.To investigate the behavior of the implant stability and its relation with quality and quantity of the bone during implant treatment, eight dental implant patients have been involved. Series of monitoring stages were conducted. The implant stability for each stage were measured using Resonance Frequency Analysis (RFA) devise and the behavior of quality and quantity of the bone during treatment have been monitored by using CBCT data. The phases of monitoring are divided into 3 phases; phase 1 is immediately after implant insertion, phase 2 is immediately after crown installation (4 month after implant insertion), and phase 3 is 1 month after crown installation (5 month after implant insertion).  The results were tabulated and analyzed using statistical software namely SPSS 20.5 to examine the correlation between basic measurement of bone quality and quantity and ISQ. The results show that during 4 month after implant insertion  period, the density of bone around the implant are decrease, this period was predicted as remodeling process. After 5 moth since implant insertion, the density start to increase. This phase possibly indicated the starting phase of osseointegration process. In addition, the ISQ for each patient was increased significantly. The primary implant stability was correlated with the space availability and bone quantity and quality, the result shows that the implant stability is proportional with the height of the mandibular and cortical thickness and inversely with width of mandibular. The highest correlation with the primary implant stability is the product of cortical thickness with the height of mandibular. There is a significant correlation between implant stability (ISQ) with dimension of site implant and density of bone.
NASOFACIAL MORPHOMETRIC ANALYSIS FOR NASAL RECONSTRUCTION
Authors: Tengku Din Tengku Noor Daimah , Ahmad Rajion Zainul , Luddin Norhayati
Published: October 2015

The advances of computer aided design with powerful additive manufacturing techniques have been applied to produce the nasal prostheses. Basically, nasal reconstruction using manual technique was time consuming. The objective of this study is to measure the naso-facial parameters and to model the nasal prostheses from the CT data. The CT data were obtained from the Radiology Department in Hospital Universiti Sains Malaysia (HUSM) Kubang Kerian. Total of 30 normal healthy subjects were included to measure nasal and facial distances. The measurement of the predetermined landmarks on the nose and face were done on the 3D images using medical imaging software. Then, the virtual nose models were segmented from the entire face. Based on the measurements, the mean for the most of parameters were higher in males compared to females. The p values for most of the parameters were also significantly different. The result showed that there was sexual dimorphism in males and females for nasal characteristics. From this study, it can be concluded that this method give more advantages over the conventional methods in terms of prosthesis fabrication time and nose shape accuracy.
HUMAN DRIVING SKILL FOR HUMAN ADAPTIVE MECHATRONICS APPLICATIONS BY USING NEURAL NETWORK SYSTEM
Authors: Izran Ishak Mohamad Hafis , Mazni Mazleenda , Badrul Hisham Amirah 'Aisha
Published: October 2015

The existence of the new improvement system for Human Machine System (HMS) is called as Human Adaptive Mechatronic (HAM) system. The main difference between these two systems is the relationship between human and machine in the system. HMS is one way relationship between human and machine while HAM is a two way relationship between human and machine. In HAM, not only human need to adapt the characteristics of machine but the machine also has to learn on human characteristics. As a part of mechatronics system, HAM has an ability to adapt with human skill to improve the performance of machine. Driving a car is one of the examples of application where HAM can be applied. One of the important elements in HAM is the quantification of human skill. Therefore, this project proposed a method to quantify the driving skill by using Artificial Neural Network (ANN) system. Feedforward neural network is used to create a multilayer neural network and five models of network were designed and tested using MATLAB Simulink software. Then, the best model from five models is chosen and compared with other method of quantification skill for verification. Based on results, the critical stage in designing the network of the system is to set the number of neurons in the hidden layer that affects an accuracy of the outputs.
SELECTION OF MUSCLE GROUPS FOR SURFACE ELECTROMYOGRAPHY (SEMG) MEASUREMENT IN ANALYZING MOTORCYCLING ACTIVITY
Authors: Rashid Helmi , Ma’arof Muhammad Izzat Nor , Haron Rohani , Wan Fauzi Wan Muhammad Syahmi , Omar Abdul Rahman , Jaafar Roseleena
Published: October 2015

While riding motorcycle have become a popular mode of transportation in most parts of the world, increase in motorcycle road accidents are very alarming. Many factors have been found to cause such motorcycle accidents and among others is motorcyclist fatigue. The aim of this study is to identify muscle groups that are related to motorcycling activity that may lead to motorcyclist muscle fatigue especially during prolonged riding. The groups of muscle recommended by this study were extracted from current literatures and studies, questionnaires and direct observation, and also a pilot surface electromyography (sEMG) experiment. Direct observation was made on motorcyclists’ hand and foot positioning during riding including their riding posture. Upon confirming the recommended muscle groups, a sEMG experiment was conducted using an established adjustable motorcycle test rig, the Postura MotergoTM. Several torso muscle groups were identified and recommended for analyzing motorcyclist muscle fatigue. However, lower extremity body muscle groups were not listed. This is due to no considerations were made by neither researchers nor being testified by participants answering the questionnaire.
FLEXIBLE DYNAMIC MODEL OF ATTITUDE MANEUVERING OF RAZAKSAT® SATELLITE
Authors: Vil Cherd Teoh , Abu Bakar Shahriman , Yaacob Sazali , Hamzah Nor Hazadura
Published: October 2015

In this paper, a dynamic model equation of the RazakSAT® class satellite three flexible solar panels for three-dimensional dynamic studies is developed based on the coupling deformation field. In the model, each solar panel is flexible and attached to the satellite body via a fixed joint where the assumption of Euler-Bernoulli beam is applied for the solar panels. Lagrange and assumed mode method are used to develop the dynamic model of the RazakSAT® multi-body system. A comprehensive model of flexible satellite has been provided in ANSYS environment as a reference when simulating the theoretical response generated by MATLAB to show that the coupling effect on the characteristics of the flexible sub system while undergoing rigid-body rotational motion.
FULL-AND REDUCED- ORDER COMPENSATOR FOR INNOSAT ATTITUDE CONTROL
Authors: Hashim Fadzilah , Mashor Mohd Yusoff , Sharun Siti Maryam
Published: October 2015

This paper presents a study on the estimator based on Linear Quadratic Regulator (LQR) control scheme for Innovative Satellite (InnoSAT). By using LQR control scheme, the controller and the estimator has been derived for state space form in all three axes to stabilize the system’s performance. This study starts by converting the transfer functions of attitude control into state space form.  Then, the step continues by finding the best value of weighting matrices of LQR in order to obtain the best value of controller gain, K. After that, the best value of L is obtained for the estimator gain. The value of K and L is combined in forming full order compensator and in the same time the reduced order compensator is also formed. Lastly, the performance of full order compensator is compared to reduced order compensator. From the simulation, results indicate that both types of estimators have presented good stability and tracking performance. However, reduced order estimator has simpler equation and faster convergence to zero than the full order estimator. This property is very important in developing a satellite attitude control for real-time implementation.
ON-LINE MODELLING AND FORECASTING OF A MOVING CAR INFORMATION USING TD-HMLP NETWORK
Authors: Saad Z. , Mashor M. Y. , Khairunizam Wan
Published: October 2015

The study proposed a model called trend data hybrid multilayered perceptron network (TD-HMLP) coupled with a modified recursive prediction error (MRPE) training algorithm as a nonlinear modeling. An on-line model was used to forecast speed, revolution and fuel balanced in a Proton Gen2 car tank. The car measured the injected fuel from fuel injection sensor and become an input for the TD-HMLP model to forecast the speed, revolution and fuel balanced in tank. These forecasted variables were also measured from the car sensors. The criterions for performances are based on the one step ahead forecasting (OSA), multi-step ahead forecasting (MSA) and adjusted R2. The forecasting result showed that TD-HMLP network is better than the conventional HMLP network to maintain higher value in adjusted R2 and produce better step in multi-step ahead forecasting. These preliminary results show that the proposed modeling approach is capable to be used as an on-line information forecaster of a moving car.
3D TERRESTRIAL LASER SCANNER FOR MANAGING EXISTING BUILDING
Authors: Abdul Shukor S. A. , Wong Razak , Rushforth E. , Basah Shafriza Nisha , Zakaria Ammar
Published: October 2015

Building Information Modelling (BIM) has gathered a lot of interest in Architectural, Engineering, Construction (AEC) areas. BIM introduces the 3D visualization element in designing and constructing new buildings, where the same design can be used to manage the building afterwards by assigned it as the 3D as-built. For existing building, professionals like architects and civil engineers need help from a specific hardware, like a 3D terrestrial laser scanner, to gather the data representing its interior and exterior. Although by applying 3D visualization or modelling for post-construction brings a lot of advantages, the implementation process are still slowly improving, compared for pre- and during construction, where it has reached its maturity. This paper will emphasizing on these advantages by discussing the benefits of implementing 3D as-built for current existing buildings and highlighting some case studies from projects done by Geodelta Systems Sdn. Bhd. towards several buildings in Malaysia. From here, having a 3D terrestrial laser scanner has brought a lot of improvement in managing existing buildings for various reasons, from fabrication, renovation to maintenance. Challenges of applying BIM for post-construction are also features here, to show on why the development are slow, compared to pre- and during construction process.
MOTORCYCLE COCKPIT DESIGN CLASSIFICATION: CODEC SYSTEM
Authors: Wan Fauzi Wan Muhammad Syahmi , Omar Abdul Rahman , Jaafar Roseleena , Nor Ma’arof Muhammad Izzat , Rashid Helmi
Published: October 2015

Motorcycle have become very popular transportation nowadays. There are several ways of classifying motorcycle into different types of categories such as according to the engine displacement sizes, type, usage, mechanical function etc. Aside from manufacturer’s classification, which is based on the engine displacement sizes, most of them are subjective. Due to the variations, research related to motorcycle are uncoordinated. In addition, consistency and reliability of data collected are necessary since the field of research is vast. This paper aims to fill this research gap by proposing a standardized method for motorcycle nomenclature system, which is a classification based on a motorcycle cockpit design.
ERGONOMIC IMPROVEMENTS IN THE HANDLING OF FIBRE INSULATOR SHEETS CUTTING
Authors: Huck-Soo Loo , Saad Nor Hayati , Rashid Amirul Abdul , Yusoff Noriah , Mohammed Redza Mohd. Ridhwan
Published: October 2015

This paper gives emphasis to an ergonomics study conducted in a fibre insulation bay of a medium-sized air handler manufacturing plant. Work-related musculoskeletal disorders and other health problems in the fibre insulator sheets cutting operations were closely looked into. Unstructured interviews were initially conducted to uncover the underlying problems, while Direct Observation (DO) and Participative Assessment (PA) methods were utilized to identify ergonomics risk factors. Ergonomics interventions by means of real life experiments were implemented. These included 1) providing semi leather gloves to replace cotton hand gloves, 2) providing plastic chairs with back rest for occasional sitting, and 3) installing a fiberglass rolling mechanism for fiberglass cutting on table top. Post survey incorporating both DO and PA methods was subsequently conducted to gauge its effectiveness in minimizing work-related musculoskeletal disorders and other health problems. This action-oriented study finally produced fruitful results which includedinsignificant low back pain and legs ache, minimized hand irritation sensations, relieved tiredness of operators, reduced nose irritation, eye itchiness, sore throat and dizziness.
INDOOR TEMPERATURE CONTROL AND ENERGY SAVING POTENTIAL OF AN AIR CONDITIONING SYSTEM USING PD CONTROLLER
Authors: Nasution Henry , Abdul Aziz Azhar , Dahlan Afiq Aiman , Zulkifli Amirah Haziqah , Sumeru Sumeru
Published: October 2015

This manuscript presents a PD controller implementation to control the compressor speed of an air conditioning system according to cooling load to fulfill thermal comfort requirements with higher energy efficiency. An interface has been designed to monitor the experiment including the controller algorithm. The temperature settings of the conditioned space are 20, 22 and 24oC with internal heat loads of 0 and 1000 W. The experiments conducted indicate that the proposed technique has better temperature control and energy efficiency compared to the on/off controller.
DEVELOPMENT OF A MOTION CAPTURE SYSTEM USING KINECT
Authors: Bujang Katherina , Ahmad Nazri Ahmad Faiz , Ahmad Azam Ahmad Fidaudin , Mahmud Jamaluddin
Published: October 2015

Microsoft Kinect has been identified as a potential alternative tool in the field of motion capture due to its simplicity and low cost. To date, the application and potential of Microsoft Kinect has been vigorously explored especially for entertainment and gaming purposes. However, its motion capture capability in terms of repeatability and reproducibility is still not well addressed. Therefore, this study aims to explore and develop a motion capture system using Microsoft Kinect; focusing on developing the interface, motion capture protocol as well as measurement analysis. The work is divided into several stages which include installation (Microsoft Kinect and MATLAB); parameters and experimental setup, interface development; protocols development; motion capture; data tracking and measurement analysis. The results are promising, where the variances are found to be less than 1% for both repeatability and reproducibility analysis. This proves that the current study is significant and the gained knowledge could contribute
EFFECT OF NANOSILICA CONTENT ON LONGITUDINAL AND TRANSVERSE TENSILE PROPERTIES OF UNIDIRECTIONAL KENAF COMPOSITE
Authors: Manap Norhashidah , Jumahat Aidah , Sapiai Napisah
Published: October 2015

Nowadays, continuous natural fibre reinforced polymer nanocomposites have attracted substantial attention among researchers due to various benefits possesses by the natural fibres. Kenaf fibre has become one of the high potential candidates to replace synthetic fibres in polymer composite. Kenaf fibre exhibits good strength and modulus properties, low density, non-abrasive during processing and biodegradable. This study is aimed to evaluate the effect of nanosilica on longitudinal and transverse tensile properties of unidirectional (UD) kenaf composite. The UD kenaf composite samples were prepared based on three different nanosilica content; i.e. 5, 13 and 25 wt.%. The samples were prepared using filament winding and vacuum bagging techniques. The 0o and 90o tensile tests were conducted in accordance to ASTM standard D3039 in order to obtain longitudinal and transverse tensile properties of unmodified and nanosilica-modified kenaf composites. The fracture surfaces of the specimens were observed using scanning electron microscope in order to identify fracture mechanisms involved during tension. The results showed that the addition of nanosilica reduced longitudinal tensile Young’s modulus, strength and failure strain of the kenaf composite. SEM micrographs revealed incomplete resin wetting and  fibre pull-out mechanism at high nanosilica content that contributed to premature failure of the kenaf composites.  However, it was found that the addition of nanosilica improved transverse tensile properties of kenaf composites since these properties were mostly governed by the properties of the matrix. A stiffer matrix improved the transverse tensile modulus and strength of kenaf composites.
SECTOR COMPLEXITY MEASURES: A COMPARISON
Authors: Abdul Rahman Siti Mariam , Borst Clark , Mulder Max , Paassen Rene van
Published: October 2015

In developing a more advanced human-machine systems for future Air Traffic Management (ATM) concepts requires a deep understanding of what constitutes operator workload and how taskload and sector complexity can affect it. Many efforts have been done in the past to measure and/or predict operator workload using sector complexity. However, most sector complexity metrics that include sector design are calculated according to a set of rules and subjective weightings, rendering them to be dependent of sector. This research focuses on comparing the Solution Space Diagram (SSD) method with a widely accepted complexity metric: Dynamic Density (DD). In essence, the SSD method used in this research, observed aircraft restrictions and opportunities to resolve traffic conflicts in both the speed and heading dimensions. It is hypothesized that the more area covered on the solution space, that is, the fewer options the controller has to resolve conflicts, the more difficult the task and the higher the workload experienced by the controller. To compare sector complexity measures in terms of their transferability in capturing dynamic complexity across different sectors, a human-in-the-loop experiment using two distinct sectors has been designed and conducted. Based on the experiments, it is revealed that the SSD metric has a higher correlation with the controllers' workload ratings than the number of aircraft and the un-weighted NASA DD metric. Although linear regression analysis improved the correlation between the workload ratings and the weighted DD metric as compared to the SSD metric, the DD metric proved to be more sensitive to changes in sector layout than the SSD metric. This result would indicate that the SSD metric is better able to capture controller workload than the DD metric, when tuning for a specific sector layout is not feasible.
Comparing the Navigator’s Response Time in Collision and Grounding Accidents
Authors: Psarros George Ad.
Published: October 2015

When the ship navigator (deck officer of the watch) is stressed, attention is narrowed and the normal flow of activities as well as action alternatives to be performed can be missed, ignored or discounted. Thus, the amount of time required integrating accessible information (i.e. displays, communication equipment, presence of hazards, etc.) and cope with the situation (course keeping or track changing) can be overestimated leading to poor or unsuccessful performance that may contribute to an accident. In order to understand how the navigator’s situational assessment can be improved, a probabilistic model is proposed consisting of three cognitive processes: information pre-processing, decision making and action implementation. This model can be evaluated by analyzing actual data derived from publicly available accident investigation reports concerning collisions and groundings. With this approach, it is possible to determine the minimum required time for navigation task execution so that erroneous behavior can be prevented from developing and materializing into an accident.
Peak Accelerations of Equipment Within a Bundle Towhead During Pile Driving Operations
Authors: Roberts Graeme , Sriskandarajah T. , Arosio Umberto , McDonald Nick , Pingen Dirk , Rajaratnam Sabesan
Published: October 2015

Pipeline bundles are towed to site between towhead manifold structures which are designed to contain all the manifold valve-work and control equipment. The towhead is a space frame that not only supports and protects the on-board equipment during service but also allows the attachment of temporary buoyancy units that are necessary for the towing and controlled ballasting operations during installation.

Pre-installed equipment within the towhead space-frame must be operable following the bundle on-shore transportation, launch, offshore tow and pile driving operations that are necessary to secure some towheads to the seabed.

The analysis work reported in this paper focuses on pile driving activities and was carried out to demonstrate that forced acceleration of pre-installed equipment, caused by transmission of pile driving energy to the towhead, did not exceed the equipment’s recommended allowable shock limits.

The desired outcome of the analyses was an understanding that equipment pre-installation offered an acceptable design solution for a particular towhead configuration founded on a soft silty clay soil in the North Sea and that this outcome would be applicable to future similar towheads.
Statistical Nanomechanics of Ice and Effect of Embedded Carbon Dioxide
Authors: Cranford Steven W.
Published: October 2015

While the macroscopic mechanical properties of pure ice has been investigated by laboratory tests and its behavior has been characterized by existing fracture mechanics models, the effect of environmental conditions — such as the concentration of embedded carbon dioxide (CO2) — is not fully understood. It is known that the chemical environment can have significant effects on the mechanical properties of ice. Using full atomistic molecular dynamics (MD), we probe the tensile strength of a single ice crystal. We systematically introduce a random concentration of CO2 molecules by replacing H2O molecules on the ice crystal lattice (e.g., substitutional defects). As anticipated, we observe a drop in strength with an increase in CO2 concentration. The decreased ice strength is not merely caused by material defects induced by the CO2 inclusions, but rather by the fact that the strength of hydrogen bonds — the chemical bonds between water molecules in an ice crystal — is actively disrupted under increasing concentrations of CO2. The inclusions provide both stress concentrations and nucleation points for crack/void formation. We then assume a Poisson distribution to reflect various concentrations of CO2 and apply nanoscale Weibull statistics (NWS) as a brittle material failure model. The results can be used to help predict the strength range of bulk ice.
Fatigue Crack Growth Rate of Reeled Pipe in Sour Environments
Authors: Safari Javad , Thodla Ramgopal , Merchant Ian , Hamilton John
Published: October 2015

Fatigue Crack Growth Rate (FCGR) of reeled pipe (strained & aged) in sour environments was investigated. FCGR frequency scans on different microstructures, i.e. heat affected zone (HAZ), and weld center line (WCL), revealed that, FCGR in corrosive environments increased with decreasing frequency and reached a plateau value at low frequencies of 10mHz to 3mHz. At these ‘plateau frequencies’, FCGR in the moderately sour environment that was investigated were found to be about 10–18× or 30× higher than the in-air values for the WCL and HAZ, respectively. There was no effect of the reeling cycles on the FCGR of the WCL or HAZ specimens. The FCGRs of the WCL were consistently lower than that of the HAZ by about a factor of 2–3× under various conditions. The reason for the lower FCGR of the WCL is not well understood. It is possible that it may be due to the higher yield strength (YS) of the overmatched welds, differing hydrogen concentration and/or diffusion coefficient or possibly due to the differences in the microstructure between the HAZ and WCL.

Paris law curves, FCGRs as a function of ΔK (stress intensity factor range), were measured on the HAZ, and WCL (both intrados) at the plateau frequency (10mHz), representative of flowline cyclic loading. They were also measured at a higher frequency of 0.33Hz, representative of Steel Catenary Risers (SCR) cyclic loading associated with wave motion. Comparisons of measured Paris law curves in corrosive environments to those in air were consistent with the results of the frequency scans. There was no effect of number of cycles of reeling on the Paris law curves in the sour environment tested for WCL and HAZ specimens at both the plateau frequency and 0.33Hz.

The results of the test program suggest FCGR of WCL and HAZ in the sour environment tested are not affected by number of cycles (up to 5) of straining on the intrados side for the strain level (1.93% per cycle) used in this study.
Analysis of Impact Loads on a Self-Elevating Unit During Jacking Operation
Authors: Ringsberg Jonas W. , Daun Viktor , Olsson Fredrik
Published: October 2015

The renewable energy resource of offshore wind is believed to have a great potential in playing an essential role on the future energy market in Europe, but there are complications such as harsh weather and low accessibility. To manage this, most offshore wind turbines of today are installed and maintained using self-elevating units (SEUs). In this study, a method is presented that enables the analysis of weather window assessments for the installation and retrieval phases of a SEU. The method of analysis takes site-specific parameters, defined as soil type and water depth, into account in addition to vessel-specific and environmental parameters. The inclusion of site-specific parameters is the novel contribution compared to assessment methodologies used today.

A simulation model is presented that incorporates a coupled non-linear time-domain analysis of vessel motion and soil-structure interaction. Soil deformation behaviour during impact is described by resistance curves based on a bearing capacity theory. A structural evaluation criterion against which impact forces are compared is used for weather window assessments. The simulation model is applied on a case study utilizing different soil types to study impact forces and the capacity of the structure for withstanding such impacts and eventually performing a weather window assessment.

The results show that the jacking operation can be divided into two phases when it comes to loads on the spudcan: a phase dominated by vertical forces followed by a phase dominated by horizontal forces. It is found that including soil deformation behaviour is of paramount importance to the magnitude of the resulting impact forces and that class-recommended practice does indeed produce rather large force estimates. Thus, assessments where site-specific parameters are incorporated could definitely increase the operable weather window for SEUs, and, consequently, increase the economic competitiveness of, for example, the offshore wind industry.
Sensitivity Study of Wake Oscillator Parameters Influencing the Fatigue Damage of a Riser Undergoing VIV
Authors: Low Ying Min , Srinil Narakorn
Published: October 2015

A great deal of attention has recently been paid to the semi-empirical modelling, nonlinear response prediction and estimation of stress and fatigue damage of marine risers undergoing vortex-induced vibrations (VIV). This is because when as the offshore industry move into deeper waters, the impact of VIV caused by ocean currents becomes detrimental being one of great concerns for offshore operators and riser engineers. For computational efficiency in time domain, the van der Pol wake oscillator, coupled with the structural equation of motion, has been an attractive approach. However, wake oscillator models rely on empirical coefficients, which have uncertainties whose effect on the fatigue reliability is not well understood. This study focusses on the wake oscillator proposed by Skop and Balasubramanian (1997). Using a top-tensioned riser model, a sensitivity study is performed on several random variables to determine their influence on the uncertainty of the fatigue damage. These variables include the maximum vibration amplitude, frequency ratio, damping ratio and lift coefficient. In addition, Monte Carlo simulations are conducted to predict the probability of failure.
Parameterization of a Multi-Directional Tidal Turbine Performance Using Computational Fluid Dynamics
Authors: Medvitz Richard B. , Jonson Michael L. , Dreyer James J. , McEntee Jarlath
Published: October 2015

High resolution RANS CFD analysis is performed to support the design and development of the Ocean Renewable Power Company (ORPC) TidGen™ multi-directional tidal turbine. Two-dimensional and three-dimensional unsteady, moving-mesh CFD is utilized to parameterize the device performance and to provide guidance for device efficiency improvements.

The unsteady CFD analysis was performed using a well validated, naval hydrodynamic CFD solver and implementing dynamic overset meshes to perform the relative motion between geometric components. This dynamic capability along with the turbulence model for the expected massively separated flows was validated against published data of a high angle of attack pitching airfoil.

Two-dimensional analyses were performed to assess both blade shape and operating conditions. The blade shape performance was parameterized on both blade camber and trailing edge thickness. The blades shapes were found to produce nearly the same power generation at the peak efficiency tip speed ratio (TSR), however off-design conditions were found to exhibit a strong dependency on blade shape. Turbine blades with the camber pointing outward radially were found to perform best over the widest range of TSR’s. In addition, a thickened blade trailing edge was found to be superior at the highest TSR’s with little performance degradation at low TSR’s.

Three-dimensional moving mesh analyses were performed on the rotating portion of the full TidGen™ geometry and on a turbine blade stack-up. Partitioning the 3D blades axially showed that no sections reached the idealized 2D performance. The 3D efficiency dropped by approximately 12 percentage points at the peak efficiency TSR. A blade stack-up analysis was performed on the complex 3D/barreled/twisted turbine blade. The analysis first assessed the infinite length blade performance, next end effects were introduced by extruding the 2D foil to the nominal 5.6m length, next barreling was added to the straight foils, and finally twist was added to the foils to reproduce the TidGen™ geometry. The study showed that making the blades a finite length had a large negative impact on the performance, whereas barreling and twisting the foils had only minor impacts. Based on the 3D simulations the largest factor impacting performance in the 3D turbine was a reduction in mass flow through the turbine due to the streamlines being forces outward in the horizontal plane due to the turbine flow resistance. Strategies to mitigate these 3D losses were investigated, including adding flow deflectors on the turbine support structure and stacking multiple turbines in-line.
Steep Unidirectional Wave Groups: Fully Nonlinear Simulations vs Experiments
Authors: Shemer Lev , Ee Bernard K.
Published: October 2015

A method was developed to carry out detailed qualitative comparison of fully nonlinear computations with the measurements of unidirectional wave groups. Computational results on evolving wave groups were compared with the available experiments. The local surface elevation variation, evolution of envelope shapes, the velocity of propagation of the steepest crests in the group and their relation to the height of the crests were obtained numerically and experimentally. The results shed additional light on the mechanisms leading to the breaking of steep waves.
VolturnUS 1:8: Conclusion of 18-Months of Operation of the First Grid-Connected Floating Wind Turbine Prototype in the Americas
Authors: Viselli Anthony M. , Goupee Andrew J. , Dagher Habib J. , Allen Christopher K.
Published: October 2015

This paper presents an overview of the successful conclusion of 18 months of testing the first grid-connected floating offshore wind turbine prototype in the Americas. The prototype, called VolturnUS 1:8, was installed off Castine, Maine, USA. The prototype is a 1:8 scale prototype and serves to de-risk the deployment of a full-scale 6MW turbine. VolturnUS utilizes innovations in materials, construction, and deployment technologies such as a concrete semi-submersible hull and an advanced composite tower to reduce the costs of offshore wind. The prototype unit was designed following the American Bureau of Shipping (ABS) “Guide for Building and Classing Floating Offshore Wind Turbine Installations”. Froude scaling was used in designing the 1:8-scale VolturnUS prototype so that the motions of the prototype in the relatively protected site represent those of the full-scale unit in an open site farther offshore. During the past year, a comprehensive instrumentation package monitored key performance characteristics of the platform during operational, extreme, and survival storm conditions. Data collected include: wind speed, turbine power, rotor angular frequency, blade pitch, torque, acceleration; tower bending moment, 6 DOF accelerations at tower top and base, mooring line tensions, and wave elevation at the platform. During the past year the prototype has experienced many environments representative of scaled ABS design conditions including operational wind and sea-states, 50-year sea states and 500-year survival sea states.

This large data set provides a unique view of a near full-scale floating wind turbine subjected to its prescribed environmental conditions. Inspections of the concrete hull following removal provided confirmation of material durability. Marine growth measurements provide data for future design efforts.
Modelling Two-Dimensional Ice-Induced Vibrations of Offshore Structures With Geometric Nonlinearities
Authors: McQueen Hugh , Srinil Narakorn
Published: October 2015

Oil and gas exploration and production has been expanding in Arctic waters. However, numerical models for predicting the ice-induced vibrations (IIV) of offshore structures are still lacking in literature. This study aims to develop a mathematical reduced-order model for predicting the two-dimensional IIV of offshore structures with geometric coupling and nonlinearities. A cylindrical structure subject to a moving uniform ice sheet is analysed using the well-known Matlock model which, in the present study, is extended and modified to account for a new empirical nonlinear stress-strain rate relationship determining the maximum compressive stress of the ice. The model is further developed through the incorporation of ice temperature, brine content, air volume, grain size, ice thickness and ice wedge angle effects on the ice compressive strength. These allow the effect of multiple ice properties on the ice-structure interaction to be investigated. A further advancement is the inclusion of an equation allowing the length of failed ice at a point of failure to vary with time. A mixture of existing equations and newly proposed empirical relationships are used. Structural geometric nonlinearities are incorporated into the numerical model through the use of Duffing oscillators, a technique previously proposed in vortex-induced vibration studies. A one-degree-of-freedom (DOF) model is successfully validated against experimental results from the literature whilst the extended two-degree-of-freedom model produces new insights. Parametric studies highlight the effect of asymmetric geometric nonlinearities and ice velocity on the structural dynamic response. Results were compared to Palmer et al. (2010) which identified quasi-static, random-like or chaotic and locked-in motions. This numerical model has advanced the original Matlock model, showing a potential to be used in future IIV analysis of arctic cylindrical structures, particularly fixed offshore structures such as lighthouses, gravity bases and wind turbine monopiles.
Location Targeting for Wave Energy Deployment From an Operation and Maintenance Perspective
Authors: de Andrés Adrián D. , Guanche Raúl , Vidal César , Losada Íñigo J.
Published: October 2015

When looking for a location for a wave energy converter (WEC) installation, developers usually look for sites with high or very high wave energy resource. From this perspective, countries like Scotland or Ireland have made great effort to include this energy source in their energy mix due to their expected high untapped potential. However, higher resource carries marine operation restrictions. Because of that, the selection of a site for a WEC deployment, the installation, operation and maintenance factors have to be considered from the beginning.

In this work an analysis of the suitable locations for the development of wave energy is performed based on the operation and maintenance (O&M) parameters. This study is performed across the globe coastlines taking the met-ocean climate data from Reguero et al (2011) global reanalysis database (GOW) developed at IH Cantabria.

Firstly, an analysis of the global availability and accessibility levels is performed all around the globe taking different wave height thresholds into account. Seven specific locations (North-West Denmark, West of Ireland, Chile, North of Spain, West Portugal, South-West Australia and North of Scotland) with high interest on wave energy have been further analyzed and compared.

Secondly, the O&M access limits are quantified in terms of the weather windows and the waiting period between available weather windows. A statistical analysis of these parameters is performed within different weather windows lengths (6 h, 12 h and 24 h). The seasonality of these parameters is also analyzed. Finally, a failure analysis will be carried out, simulating the repair operation along the lifecycle of the device for different failure rates and waiting times. The affection of this failure and repair scheme over the power production of a device analyzed previously in Andres et al (2014) will be presented.

In this study, some locations with high resource (Spain, Nova Scotia) lead to medium to high accessibilities/availabilities due to the balance between resource and persistence of the weather conditions. Some locations with high resource such as Chile or Australia resulted inaccessible during very long periods of time due to the persistence of severe conditions and then not very recommended for novel converters with uncertain failure rates.
Viscous Damping of Floating Bodies in Waves
Authors: Graham J. Michael R. , Downie Martin J.
Published: October 2015

A numerical method developed from earlier work [1, 2] of predicting damping due to eddy shedding from sharp or rounded bilges of a hull of arbitrary cross-section in beam waves is presented. The method matches an inner solution which simulates the local bilge section separated flow numerically to an outer wave potential flow solution. The latter can be any standard 3-dimensional panel or other method for the whole body which provides the local values of the matching velocity parameter at all bilge sections which shed eddies. Scaling by the matching parameter provides a physically based sectional damping coefficient for a response computation. In the case of free response of a floating body feed-back from the viscous damping to the bilge velocity parameter through the response mode amplitudes necessitates iteration which generally converges very quickly.

Computational predictions carried out in the frequency domain using this prediction method assuming linear wave theory for the outer flow are presented and compared with laboratory wave tank measurements for roll response of two floating hulls in regular and random waves. Application of the method to viscous damping of more complex geometries is also possible.
Sandwich Pipe: Reel-Lay Installation Effects
Authors: Paz Claudio Moura , Fu Guangming , Estefen Segen Farid , Lourenço Marcelo Igor , Chujutalli John Alex H.
Published: October 2015

Comprising an annular layer with adequate thermal insulation and structural resistance material enclosed by two concentric steel pipes, sandwich pipes could be an alternative for flowlines in ultra-deepwater for the pre-salt reservoirs in offshore Brazil. In this work, a numerical and experimental study was performed to investigate the collapse behavior of sandwich pipes considering the reel-lay installation method. Experimental models were manufactured using two different geometries of stainless steel pipes and strain hardening cementitious composites with PVA fiber (SHCC) in annular layer. One set of specimens was tested using a reel-lay apparatus and another set was kept intact. A hyperbaric chamber was then used to test both sets of specimens to collapse. The collapse resistance of the proposed sandwich structure was investigated, and the detrimental effect of the reeling strains to the collapse resistance was assessed. The numerical models simulated reeling and straightening loads during reel-lay installation and then the collapse under external pressure. The results were compared with experimental measurements and shown good agreement.