http://hdl.handle.net/10197/3671 2017-10-31T14:24:51Z 2017-10-31T14:24:51Z Zou, Guang Banisoleiman, Kian González, Arturo http://hdl.handle.net/10197/9002 2017-10-10T14:09:33Z 2016-11-01T00:00:00Z

Methodologies for Crack Initiation in Welded Joints Applied to Inspection Planning Zou, Guang; Banisoleiman, Kian; González, Arturo Crack initiation and propagation threatens structural integrity of welded joints and normally inspections are assigned based on crack propagation models. However, the approach based on crack propagation models may not be applicable for some high-quality welded joints, because the initial flaws in them may be so small that it may take long time for the flaws to develop into a detectable size. This raises a concern regarding the inspection planning of high-quality welded joins, as there is no generally acceptable approach for modeling the whole fatigue process that includes the crack initiation period. In order to address the issue, this paper reviews treatment methods for crack initiation period and initial crack size in crack propagation models applied to inspection planning. Generally, there are four approaches, by: 1) Neglecting the crack initiation period and fitting a probabilistic distribution for initial crack size based on statistical data; 2) Extrapolating the crack propagation stage to a very small fictitious initial crack size, so that the whole fatigue process can be modeled by crack propagation models; 3) Assuming a fixed detectable initial crack size and fitting a probabilistic distribution for crack initiation time based on specimen tests; and, 4) Modeling the crack initiation and propagation stage separately using small crack growth theories and Paris law or similar models. The conclusion is that in view of trade-off between accuracy and computation efforts, calibration of a small fictitious initial crack size to S-N curves is the most efficient approach.

2016-11-01T00:00:00Z Carey, Ciaran O'Brien, Eugene J. Malekjafarian, Abdollah Lydon, Myra Taylor, Su E. http://hdl.handle.net/10197/8782 2017-10-03T08:31:34Z 2017-02-15T00:00:00Z

Direct Field Measurement of the Dynamic Amplification in a Bridge Carey, Ciaran; O'Brien, Eugene J.; Malekjafarian, Abdollah; Lydon, Myra; Taylor, Su E. In this paper, the level of dynamics, as described by the Assessment Dynamic Ratio (ADR), is measured directly through a field test on a bridge in the United Kingdom. The bridge was instrumented using fiber optic strain sensors and piezo-polymer weigh-in-motion sensors were installed in the pavement on the approach road. Field measurements of static and static-plus-dynamic strains were taken over 45 days. The results show that, while dynamic amplification is large for many loading events, these tend not to be the critical events. ADR, the allowance that should be made for dynamics in an assessment of safety, is small.

2017-02-15T00:00:00Z Zou, Guang Banisoleiman, Kian González, Arturo http://hdl.handle.net/10197/8765 2017-09-18T12:03:58Z 2017-08-10T00:00:00Z

Uncertainty quantification and calibration of a modified fracture mechanics model for reliability-based inspection planning Zou, Guang; Banisoleiman, Kian; González, Arturo Efficient inspection and maintenance are important means to enhance fatigue reliability of engineering structures, but they can only be achieved efficiently with the aid of accurate pre-diction of fatigue crack initiation and growth until fracture. The influence of crack initiation on fatigue life has received a significant amount of attention in the literature, although its im-pact on the inspection plan is not generally addressed. Current practice in the prediction of fatigue life is the use of S-N models at the design stage and Fracture Mechanics (FM) models in service. On the one hand, S-N models are relatively easy to apply given that they directly relate fatigue stress amplitude to number of cycles of failure, however, they are difficult to extrapolate outside the test conditions employed to define the S-N curves. On the other hand, FM models like the Paris propagation law give measurable fatigue damage accumulation in terms of crack growth and have some ability to extrapolate results outside the test conditions, but they can only be a total fatigue life model if the initial crack size was known given that they do not address the crack initiation period. Furthermore, FM models generally introduce large uncertainties in parameters that are often difficult to measure such as initial crack size, crack growth rate, threshold value for stress intensity factor range, etc. This paper proposes a modified FM model that predicts the time to failure allowing for crack initiation period. The main novelty of the modified FM model is the calibration using S-N data (i.e., inclusive of crack initiation period) for an established criterion in fatigue life and reliability level. Sources of uncertainty associated to the model are quantified in probabilistic terms. The modified FM model can then be applied to reliability-based inspection planning. An illustrative example is performed on a typical detail of ship structure, where the optimum inspection plan derived from the proposed model is compared to recommendations by existing FM models. Results demonstrate to what extent is the optimum inspection plan influenced by the crack initiation period. The modified model is shown to be a reliable tool for both fatigue design and fatigue management of inspection and maintenance intervals.  12th International Conference on Structural Safety & Reliability (ICOSSAR 2017), Vienna, Austria, August, 2017

2017-08-10T00:00:00Z Mohammed, Omar González, Arturo http://hdl.handle.net/10197/8757 2017-09-07T10:10:07Z 2017-11-01T00:00:00Z

Static and dynamic moments for any plane within a straight solid slab bridge caused by the crossing of a truck Mohammed, Omar; González, Arturo A lot of research has been carried out to explain the manner in which longitudinal moments of a bridge respond to traffic. The total longitudinal bending moment is made of 'static' and 'dynamic' components, which vary with time as a result of the inertial forces of the bridge and changes in value and point of application of the forces of the vehicle. However, there is limited evidence about how bending moments at planes other than longitudinal, or twisting moments, act in response to a moving vehicle. For the first time in the literature, this paper analyses the total resultant moments ('static' + 'dynamic') for any plane orientation (from 0 to 360°) at any location of a solid slab deck due to the crossing of a vehicle. The bridge is modelled as a simply supported straight orthotropic plate and the vehicle is modelled as a three-dimensional 5-axle articulated system composed of interconnected sprung and unsprung masses. Simulations are performed for three vehicle transverse paths and three speeds. Using Wood and Armer equations, the resultant moment at any plane orientation can be obtained from equilibrium of bending and twisting moments acting on longitudinal and transverse planes. Maximum twisting moments develop in planes at 45° with longitudinal and transverse planes. Bending moments reach maximum and minimum values at longitudinal and transverse planes. Nevertheless, the moments acting on other plane orientations cannot be ignored in order to accurately assess whether the moment capacity of the bridge provides adequate safety. Therefore, the amount of slab reinforcement will be sufficient provided that the moment capacity exceeds the applied moment for any location and plane. Critical locations with highest values of sagging, hogging and twisting are identified in the bridge, and the dynamic amplification associated to the applied moments is evaluated. Bridge codes such as the Eurocode employ a unique built-in dynamic amplification factor for moment that depends only on the bridge length and the number of lanes. This paper shows how to perform an improved assessment allowing for changes in dynamic behaviour with location and plane orientation, which may prevent needless expense in bridge rehabilitation.

2017-11-01T00:00:00Z Zou, Guang Banisoleiman, Kian González, Arturo http://hdl.handle.net/10197/8749 2017-09-04T14:00:27Z 2017-05-25T00:00:00Z

Reliability-based inspection planning in view of both crack initiation and propagation Zou, Guang; Banisoleiman, Kian; González, Arturo Fatigue cracks pose threats to the integrity of welded structures and thus need to be addressed in the whole service lives of structures. In-service inspections are important means to decease the probability of failure due to uncertainties that cannot be accounted for in the design stage. To help schedule inspection actions, the decline curve of reliability index with time needs to be known. A predictive tool is normally developed based on crack propagation models neglecting the crack initiation stage, which leads to conservative predictions for fatigue life. Inspection plans built on those predictions are far from optimal, especially for welds with relatively long crack initiation life. This paper proposes to use a fracture mechanics based reliabil-ity analysis method that takes the crack initiation stage into account via the concept of Time-To-Crack-Initiation (TTCI). The optimum inspection plan for a fatigue prone ship structural component is derived by the new approach and compared to the commonly-used method that only considers crack propagation life. Two inspection planning approaches are tested to investigate the influence of incorporating crack initiation period: (i) target reliability approach and, (ii) equidistant inspection times approach. With each planning ap-proach, two inspection methods are adopted: close visual and magnetic particle inspection. The paper con-cludes with recommendations on the inspection method and planning approach to adopt while considering and without considering the crack initiation stage. 27th annual European Safety and Reliability Conference (ESREL 2017), Portoroz, Slovenia, June, 2017

2017-05-25T00:00:00Z Milana, Giulia Banisoleiman, Kian González, Arturo http://hdl.handle.net/10197/8748 2017-09-04T14:03:35Z 2017-05-25T00:00:00Z

Field characterization of location-specific dynamic amplification factors towards fatigue calculations in ship unloaders Milana, Giulia; Banisoleiman, Kian; González, Arturo This paper highlights the impact of dynamic amplification factors in remaining fatigue life assessment of ship unloaders. In practice, the widely accepted procedure for these structures is to carry out a fatigue life assessment envisages: (1) carrying out static analysis, (2) taking into account dynamics via the application of dynamic amplification factors, and (3) applying Miner's rule. This factor, provided by the standard, is applied to the structure as a whole without considering the vibration of each structural member individually. This paper characterizes the dynamic behavior of each element using location-based dynamic amplification factors estimated from measurements. This caters for a more accurate assessment of the structure, whilst maintaining the simplicity of the standard procedure. 27th annual European Safety and Reliability Conference (ESREL 2017), Portoroz, Slovenia, June, 2017

2017-05-25T00:00:00Z Gonzalez Merino, Alberto Costas de la Peña, Luis González, Arturo http://hdl.handle.net/10197/8747 2017-09-04T14:04:45Z 2017-05-25T00:00:00Z

Parametric analysis of modelling properties governing the seismic response of free-standing spent fuel racks Gonzalez Merino, Alberto; Costas de la Peña, Luis; González, Arturo Spent fuel racks are steel structures designed to store the spent fuel assemblies removed from the nuclear power reactor. In order to maximize the storage capacity of the pool, rack units are spaced by only a few centimeters setting up a matrix shape to fit in the spent fuel pool with a minimum clearance. Rack units rest in free-standing conditions submerged in water at 12 m depth. During a seismic event, racks undergo large displacements namely sliding, rocking, twisting and turning. Furthermore, the response of a unit is influenced by the others due to the so-called 'water coupling effect'. An accurate estimation of their response is essential to achieve a safe pool layout and a reliable structural design. The dynamic analysis of such a rack system deals with highly nonlinear behavior, a transient dynamic response and a fluid-structure interaction problem. A transient analysis with direct integration of the equation of motion throughout the whole earthquake duration becomes therefore unavoidable. An ad-hoc methodology based on the finite element method takes advantage of dynamic contact elements and implements the hydrodynamic mass concept. The latter has traditionally been accepted as a cost-effective approach to replace the water effect by an equivalent added mass. However, some dispersion of results still remains. This paper carries out a parametric analysis of the key modelling properties for a simple two-rack system. This technique examines the behavior of the main transient outputs as a modelling parameter is systematically varied. The modelling parameters under study are the mesh discretization, the rack-to-pool and fuel-to-cell contact stiffness, the flexural rigidity of the fuel assembly and the gaps existing between the fuel assembly and the storage cell. Its influence is highlighted on outputs as maximal and minimal relative displacements, maximal vertical force on support and CPU time. These numerical results provide a source of insight into the general behavior of the rack systems and an effective tool to propose a reliable modeling and meshing. The trade-off between outputs and computational cost and is also discussed. 27th annual European Safety and Reliability Conference (ESREL 2017), Portoroz, Slovenia, June, 2017

2017-05-25T00:00:00Z Raj Pant, Sara Goswami, Anjali Finarelli, John A. http://hdl.handle.net/10197/8554 2017-05-26T16:17:15Z 2014-09-10T00:00:00Z

Complex body size trends in the evolution of sloths (Xenarthra: Pilosa) Raj Pant, Sara; Goswami, Anjali; Finarelli, John A. Extant sloths present an evolutionary conundrum in that the two living genera are superficially similar (small-bodied, folivorous, arboreal) but diverged from one another approximately 30 million years ago and are phylogenetically separated by a radiation of medium to massive, mainly ground-dwelling, taxa.  Indeed, the species in the two living genera are among the smallest, and perhaps most unusual, of the 50+ known sloth species, and must have independently and convergently evolved small size and arboreality.  In order to accurately reconstruct sloth evolution, it is critical to incorporate their extinct diversity in analyses.  Here, we used a dataset of 57 species of living and fossil sloths to examine changes in body mass mean and variance through their evolution, employing a general time-variable model that allows for analysis of evolutionary trends in continuous characters within clades lacking fully-resolved phylogenies, such as sloths.Results:Our analyses supported eight models, all of which partition sloths into multiple subgroups, suggesting distinct modes of body size evolution among the major sloth lineages.  Model-averaged parameter values supported trended walks in most clades, with estimated rates of body mass change ranging as high as 126kg/million years for the giant ground sloth clades Megatheriidae and Nothrotheriidae.  Inclusion of living sloth species in the analyses weakened reconstructed rates for their respective groups, with estimated rates for Megalonychidae four times higher when the extant genus Choloepus species was excluded.  Conclusions:Analyses based on extant taxa alone have the potential to oversimplify or misidentify macroevolutionary patterns. This study demonstrates the impact that integration of data from the fossil record can have on reconstructions of character evolution and establishes that body size evolution in sloths was complex, but dominated by trended walks towards the enormous sizes exhibited in some recently extinct forms.

2014-09-10T00:00:00Z Feeley, Hugh B. Bruen, Michael Bullock, Craig Christie, Mike Kelly, Fiona Kelly-Quinn, Mary http://hdl.handle.net/10197/8516 2017-05-16T12:22:59Z 2017-01-01T00:00:00Z

ESManage Programme: Irish Freshwater Resources and Assessment of Ecosystem Services Provision Feeley, Hugh B.; Bruen, Michael; Bullock, Craig; Christie, Mike; Kelly, Fiona; Kelly-Quinn, Mary Freshwater is vital for all forms of life and it is a key requirement in almost all human activities. The societal importance of water has been highlighted by the United Nations, with access to clean water and sanitation regarded as a universal human right. Consequently, the sustainable management of freshwater resources has gained importance at regional, international and global scales. However, the activities of humankind affect freshwater resources extensively, in terms of both quantity and quality, through a variety of activities ranging from abstraction of water for drinking and irrigation to waste disposal. Today, worldwide freshwater ecosystems are undergreat pressure and are one of the most endangered ecosystems. Furthermore, climate change, especially in relation to precipitation patterns and flooding, will result in the traditional norms being replaced with increased variability and unpredictability, with knock-on effects for human societies and well-being.

2017-01-01T00:00:00Z Yiotis, Charilaos Evans-FitzGerald, Christiana McElwain, Jennifer C. http://hdl.handle.net/10197/8504 2017-05-11T10:26:55Z 2017-03-11T00:00:00Z

Differences in the photosynthetic plasticity of ferns and Ginkgo grown in experimentally controlled low [O2]: [CO2] atmospheres may explain their contrasting ecological fate across the Triassic-Jurassic mass extinction boundary Yiotis, Charilaos; Evans-FitzGerald, Christiana; McElwain, Jennifer C. Background and Aims: Fluctuations in [CO2] have been widely studied as a potential driver of plant evolution; however, the role of a fluctuating [O2]:[CO2] ratio is often overlooked. The present study aimed to investigate the inherent physiological plasticity of early diverging, extant species following acclimation to an atmosphere similar to that across the Triassic–Jurassic mass extinction interval (TJB, approx. 200 Mya), a time of major ecological change. Methods: Mature plants from two angiosperm (Drimys winteri and Chloranthus oldhamii), two monilophyte (Osmunda claytoniana and Cyathea australis) and one gymnosperm (Ginkgo biloba) species were grown for 2 months in replicated walk-in Conviron BDW40 chambers running at TJB treatment conditions of 16 % [O2]– 1900 ppm [CO2] and ambient conditions of 21 % [O2]–400 ppm [CO2], and their physiological plasticity was assessed using gas exchange and chlorophyll fluorescence methods. Key Results: TJB acclimation caused significant reductions in the maximum rate of carboxylation (VCmax) and the maximum electron flow supporting ribulose-1,5-bisphosphate regeneration (Jmax) in all species, yet this downregulation had little effect on their light-saturated photosynthetic rate (Asat). Ginkgo was found to photorespire heavily under ambient conditions, while growth in low [O2]:[CO2] resulted in increased heat dissipation per reaction centre (DIo/RC), severe photodamage, as revealed by the species' decreased maximum efficiency of primary photochemistry (Fv/Fm) and decreased in situ photosynthetic electron flow (Jsitu). Conclusions: It is argued that the observed photodamage reflects the inability of Ginkgo to divert excess photosynthetic electron flow to sinks other than the downregulated C3 and the diminished C2 cycles under low [O2]:[CO2]. This finding, coupled with the remarkable physiological plasticity of the ferns, provides insights into the underlying mechanism of Ginkgoales' near extinction and ferns' proliferation as atmospheric [CO2] increased to maximum levels across the TJB.

2017-03-11T00:00:00Z Cheronet, Olivia Finarelli, John A. Pinhasi, Ron http://hdl.handle.net/10197/8468 2017-05-03T11:15:03Z 2016-09-13T00:00:00Z

Morphological change in cranial shape following the transition to agriculture across western Eurasia Cheronet, Olivia; Finarelli, John A.; Pinhasi, Ron The Neolithic transition brought about fundamental social, dietary and behavioural changes in human populations, which, in turn, impacted skeletal morphology. Crania are shaped through diverse genetic, ontogenetic and environmental factors, reflecting various elements of an individual’s life. To determine the transition’s effect on cranial morphology, we investigated its potential impact on the face and vault, two elements potentially responding to different influences. Three datasets from geographically distant regions (Ukraine, Iberia, and the Levant plus Anatolia) were analysed. Craniometric measurements were used to compare the morphology of pre-transition populations with that of agricultural populations. The Neolithic transition corresponds to a statistically significant increase only in cranial breadth of the Ukrainian vaults, while facial morphology shows no consistent transformations, despite expected changes related to the modification of masticatory behaviour. The broadening of Ukrainian vaults may be attributable to dietary and/or social changes. However, the lack of change observed in the other geographical regions and the lack of consistent change in facial morphology are surprising. Although the transition from foraging to farming is a process that took place repeatedly across the globe, different characteristics of transitions seem responsible for idiosyncratic responses in cranial morphology.

2016-09-13T00:00:00Z Vartia, Salla Villanueva-Cañas, José L. Finarelli, John A. Farrell, Edward D. Hughes, Graham M. Carlsson, Jeanette E. L. Carlsson, Jens et al. http://hdl.handle.net/10197/8467 2017-05-03T11:07:30Z 2016-01-20T00:00:00Z

A novel method of microsatellite genotyping-by-sequencing using individual combinatorial barcoding Vartia, Salla; Villanueva-Cañas, José L.; Finarelli, John A.; Farrell, Edward D.; Hughes, Graham M.; Carlsson, Jeanette E. L.; Carlsson, Jens; et al. This study examines the potential of next-generation sequencing based 'genotyping-by-sequencing'(GBS) of microsatellite loci for rapid and cost-effective genotyping in large-scale population genetic studies. The recovery of individual genotypes from large sequence pools was achieved by PCR-incorporated combinatorial barcoding using universal primers. Three experimental conditions were employed to explore the possibility of using this approach with existing and novel multiplex marker panels and weighted amplicon mixture. The GBS approach was validated against microsatellite data generated by capillary electrophoresis. GBS allows access to the underlying nucleotide sequences that can reveal homoplasy, even in large datasets and facilitates cross laboratory transfer. GBS of microsatellites, using individual combinatorial barcoding, is potentially faster and cheaper than current microsatellite approaches and offers better and more data.

2016-01-20T00:00:00Z Mockler, Eva M. Deakin, Jenny Archbold, Marie A. Daly, Donal Bruen, Michael http://hdl.handle.net/10197/8444 2017-04-24T12:28:53Z 2016-01-01T00:00:00Z

Nutrient Load Apportionment to Support the Identification of Appropriate Water Framework Directive Measures Mockler, Eva M.; Deakin, Jenny; Archbold, Marie A.; Daly, Donal; Bruen, Michael A model for predicting the sources of nutrient loads (phosphorus and nitrogen) to water has been developed to support Water Framework Directive (WFD) implementation. This model integrates catchment data and pressure information to enable characterisation of Source-Pathway-Receptor relationships. The Source Load Apportionment Model (SLAM) is a flexible framework for incorporating national data and research to quantify nutrient losses from both point discharges (urban wastewater, industry and septic tank systems) and diffuse sources (pasture, arable, forestry, peatlands etc.). Hydrogeological controls have a strong impact on nutrient fluxes, particularly in agricultural catchments, and have been incorporated into the diffuse agricultural model, the Catchment Characterisation Tool (CCT). This paper describes the SLAM framework, including the CCT, along with the data inputs and assumptions. Results for the Suir catchment matched the measured loads of nitrogen and phosphorus well, and showed that pasture is the dominant source of nitrogen across all sub-catchments. The main sources of phosphorus in sub-catchments varied between diffuse agriculture, wastewater and industrial discharges. A relatively small proportion (13%) of the Suir catchment area requires a reduction in phosphorus emissions to achieve Good Status. In these areas, model results can be used in conjunction with knowledge from local authorities and investigative assessments gathered through the WFD characterisation process to identify significant pressures that contribute excessive nutrient loads. An example of assessing load reduction scenarios is presented to illustrate how modelling can support catchment scientists and managers in identifying appropriate measures. 

2016-01-01T00:00:00Z Fernandes, Daniel Sirak, Kendra Novak, Mario Finarelli, John A. Carlsson, Jeanette E. L. Ferretti, Edmondo Pinhasi, Ron Carlsson, Jens et al. http://hdl.handle.net/10197/8434 2017-04-18T15:16:29Z 2017-01-30T00:00:00Z

The Identification of a 1916 Irish Rebel: New Approach for Estimating Relatedness from Low Coverage Homozygous Genomes Fernandes, Daniel; Sirak, Kendra; Novak, Mario; Finarelli, John A.; Carlsson, Jeanette E. L.; Ferretti, Edmondo; Pinhasi, Ron; Carlsson, Jens; et al. Thomas Kent was an Irish rebel who was executed by British forces in the aftermath of the Easter Rising armed insurrection of 1916 and buried in a shallow grave on Cork prison’s grounds. In 2015, ninety-nine years after his death, a state funeral was offered to his living family to honor his role in the struggle for Irish independence. However, inaccuracies in record keeping did not allow the bodily remains that supposedly belonged to Kent to be identified with absolute certainty. Using a novel approach based on homozygous single nucleotide polymorphisms, we identified these remains to be those of Kent by comparing his genetic data to that of two known living relatives. As the DNA degradation found on Kent’s DNA, characteristic of ancient DNA, rendered traditional methods of relatedness estimation unusable, we forced all loci homozygous, in a process we refer to as 'forced homozygote approach'. The results were confirmed using simulated data for different relatedness classes. We argue that this method provides a necessary alternative for relatedness estimations, not only in forensic analysis, but also in ancient DNA studies, where reduced amounts of genetic information can limit the application of traditional methods.

2017-01-30T00:00:00Z Delaney, Declan O'Hare, G. M. P. (Greg M. P.) http://hdl.handle.net/10197/8194 2016-12-05T15:19:05Z 2016-12-01T00:00:00Z

A Framework to Implement IoT Network Performance Modelling Techniques for Network Solution Selection Delaney, Declan; O'Hare, G. M. P. (Greg M. P.) No single network solution for Internet of Things (IoT) networks can provide the required level of Quality of Service (QoS) for all applications in all environments. This leads to an increasing number of solutions created to fit particular scenarios. Given the increasing number and complexity of solutions available, it becomes difficult for an application developer to choose the solution which is best suited for an application. This article introduces a framework which autonomously chooses the best solution for the application given the current deployed environment. The framework utilises a performance model to predict the expected performance of a particular solution in a given environment. The framework can then choose an apt solution for the application from a set of available solutions. This article presents the framework with a set of models built using data collected from simulation. The modelling technique can determine with up to 85% accuracy the solution which performs the best for a particular performance metric given a set of solutions. The article highlights the fractured and disjointed practice currently in place for examining and comparing communication solutions and aims to open a discussion on harmonising testing procedures so that different solutions can be directly compared and offers a framework to achieve this within IoT networks.

2016-12-01T00:00:00Z Chen, Siyuan Laefer, Debra F. Mangina, Eleni http://hdl.handle.net/10197/8152 2017-05-01T01:00:12Z 2016-01-01T00:00:00Z

State of Technology Review of Civilian UAVs Chen, Siyuan; Laefer, Debra F.; Mangina, Eleni Background: Unmanned Aerial Vehicle (UAV) technology has exploded in recent years. Presently UAVs are beginning to be major in roads into geographical mapping, site inspection, agriculture, and search and rescue. Methods: This paper reviewed patents and papers worldwide related to both hardware and software for the construction and deployment of UAVs and is intended to provide a snapshot of currently available UAV technologies, as well as to identify recent trends and future opportunities in affiliated hardware and software. Results: Basic components related to self-designed units are explained (e.g. platform selection, autopilot control comparison and sensor selection), and current applications and research areas are discussed. Since autonomous navigation is a key technology in UAV applications, concepts about this are also explained. Conclusions: Both in the self-designed and commercial markets, UAV components are becoming modularized. By following a standard components list, it is no longer difficult to make a customised UAV. In this way, commercial products are becoming cheaper and more standardized in their performance. Current limitations of UAVs has also become more readily detectible. Extending the flight time, improving autonomous navigation abilities, and enriching the payload capacity will be the future research focus to address these limitations.

2016-01-01T00:00:00Z Mohammed, Omar González, Arturo http://hdl.handle.net/10197/8080 2016-10-18T16:05:09Z 2015-01-01T00:00:00Z

Footprint caused by a vehicle configuration on the dynamic amplification of the bridge response Mohammed, Omar; González, Arturo The passage of a vehicle over a bridge leaves a unique footprint in the form of measured strains (or displacements) across the structure. This paper proposes a new level I damage detection method for short-span bridges using footprints of Dynamic Amplification Factor (DAF) versus vehicle speed. The total response of a bridge to a moving load is time- varying, and it can be assumed to be made of two components: 'static' and 'dynamic'. Here, DAF is defined as the ratio of the maximum total response to the maximum 'static' component. For a given bridge, DAF patterns will vary with vehicle configuration. However, for a vehicle configuration (or a number of them), the mean DAF pattern measured on the bridge will remain unaltered unless the conditions of the bridge changed. The latter is the subject of investigation in this paper. In order to test the feasibility of using these patterns for monitoring purposes, damage is simulated within a bridge model as stiffness losses of 10% and 30% at mid-span. Changes in stiffness are identified by differences between DAF patterns corresponding to the healthy and damaged bridges. Results show to be more sensitive to damage than a traditional level I damage detection method based on variation of natural frequencies.

2015-01-01T00:00:00Z Zou, Guang Banisoleiman, Kian González, Arturo http://hdl.handle.net/10197/8048 2016-11-14T14:25:49Z 2016-11-08T00:00:00Z

Methodologies for Crack Initiation in Welded Joints Applied to Inspection Planning Zou, Guang; Banisoleiman, Kian; González, Arturo Over the past decades, crack propagation has been extensively studied by researchers around the word. The approach based on crack propagation models have been widely used in inspection planning. This approach has the advantage that it gives measurable fatigue damage accumulation in terms of crack propagation with time and thus crack propagation models can be updated with inspection results. However, a prerequisite for using crack propagation models in inspection planning is that parameters such as initial crack size, crack growth rate, geometry function, etc. are known.  Among those parameters, initial crack size, depending on welding quality, material and the environment, is associated with the most uncertainties because of sampling and measuring problems. Another prerequisite for using crack propagation models in inspection planning is that crack initiation period can be assumed to be negligible. Both prerequisites are challenged nowadays as manufacturing and welding techniques have been improved. Some high-quality welded joins have been proven free from detectable size of flaws and the crack initiation period can account for a large part of the whole fatigue life. This gives rise to big difficulty for inspection planning of high-quality welded joins, as there is no generally acceptable approach for modelling the whole fatigue process that includes crack initiation period. Compared to as-welded joints, reliable inspection planning is more crucial for high-quality welded joins, as they are generally designed to withstand a larger stress range. In addition, they may have shorter time for inspection as crack initiation time account for a large part of fatigue life, with a shorter crack propagation period to failure due to higher stress range. To address this problem for high-quality welded joints, a robust model accounting for the whole fatigue process needs to be developed. The core issue is how the crack initiation period can be modelled and added to the crack propagation time. To help identify this issue, this paper reviews treatment methods for crack initiation period and initial crack size in crack propagation models applied to inspection planning. Generally there are four approaches, by: 1) Neglecting the crack initiation period and fitting a probabilistic distribution for initial crack size based on statistical data, e.g. Weibull distribution or lognormal distribution; 2) Extrapolating the crack propagation stage to a very small fictitious initial crack size, so that the whole fatigue process can be modelled by crack propagation models; 3) Assuming a fixed detectable initial crack size and fitting a probabilistic distribution for crack initiation time based on specimen tests; 4) Modelling the crack initiation and propagation stage separately using small crack growth theories and Paris law or similar models. Conclusion is that in view of trade-off between accuracy and computation efforts, calibration of a small fictitious initial crack size to S-N curves is the most efficient approach. ICRSS 2016: 18th International Conference on Reliability and Structural Safety, Venice, Italy, 7-8 November 2016

2016-11-08T00:00:00Z Isfeld, Andrea C. Moradabadi, Ehsan Laefer, Debra F. Shrive, Nigel G. http://hdl.handle.net/10197/8047 2016-10-13T12:04:30Z 2016-01-01T00:00:00Z

Uncertainty Analysis of the Effect of Grout Injection on the Deformation of Multi-Wythe Stone Masonry Walls Isfeld, Andrea C.; Moradabadi, Ehsan; Laefer, Debra F.; Shrive, Nigel G. The eighteenth century Prince of Wales Fort in Manitoba Canada has experienced extensive freezethaw damage and mortar washout within the escarp walls resulting in distress and failures at multiple locations. Injection of grout could counteract this degradation of structural stability. However existing literature provides little guidance as to the improvement level that could be expected, especially with respect to out-of-plane performance. As such, the proposed treatment was modelled to include a high level of uncertainty in the system through the application of a Random Field Finite Element Micromodelling technique. A Latin Hyper cube simulation method was used in conjunction with a parametric finite element model to randomize the material properties of each stone and relevant grouting layer. The numerical results predicted that the stone-grout bond was the most critical parameter in the proposed intervention, and that in the grouted wall sections, collapse would be avoided and lateral displacements stabilized with the proposed treatment.

2016-01-01T00:00:00Z Milana, Giulia Banisoleiman, Kian Gonzalez, Arturo http://hdl.handle.net/10197/7985 2016-09-23T16:03:20Z 2016-09-29T00:00:00Z

Sources of structural failure in ship unloaders Milana, Giulia; Banisoleiman, Kian; Gonzalez, Arturo This paper reviews the most common causes of failure in ship unloaders. The structural forms employed in the design of ship unloaders and the characteristics of the loads acting on these structures are introduced first. Then, typical failures including overloading, joint failure, cable breaking, corrosion and fatigue failure amongst others, are described. Fatigue failure is discussed in further detail. When assessing a ship unloader for fatigue, it is necessary to define the fatigue demand and the fatigue strength capacity of those structural details under investigation. The latter experiences stress cycles that accumulate over time until reaching a limit that leads to cracking. Loads and stresses need to be monitored to describe those cycles, and critical locations must be checked to prevent a catastrophic failure. 26th European Safety and Reliability Conference (ESREL 2016), Glasgow, UK, 25-29 September 2016

2016-09-29T00:00:00Z Cahill, Niamh Kemp, Andrew C. Horton, Benjamin P. Parnell, Andrew C. http://hdl.handle.net/10197/7965 2016-10-07T14:34:08Z 2016-02-29T00:00:00Z

A Bayesian hierarchical model for reconstructing relative sea level: from raw data to rates of change Cahill, Niamh; Kemp, Andrew C.; Horton, Benjamin P.; Parnell, Andrew C. We present a Bayesian hierarchical model for reconstructing the continuous and dynamic evolution of relative sea-level (RSL) change with quantified uncertainty. The reconstruction is produced from biological (foraminifera) and geochemical (δ13C) sea-level indicators preserved in dated cores of salt-marsh sediment. Our model is comprised of three modules: (1) a new Bayesian transfer (B-TF) function for the calibration of biological indicators into tidal elevation, which is flexible enough to formally accommodate additional proxies; (2) an existing chronology developed using the Bchron age–depth model, and (3) an existing Errors-In-Variables integrated Gaussian process (EIV-IGP) model for estimating rates of sea-level change. Our approach is illustrated using a case study of Common Era sea-level variability from New Jersey, USA We develop a new B-TF using foraminifera, with and without the additional (δ13C) proxy and compare our results to those from a widely used weighted-averaging transfer function (WA-TF). The formal incorporation of a second proxy into the B-TF model results in smaller vertical uncertainties and improved accuracy for reconstructed RSL. The vertical uncertainty from the multi-proxy B-TF is  ∼  28 % smaller on average compared to the WA-TF. When evaluated against historic tide-gauge measurements, the multi-proxy B-TF most accurately reconstructs the RSL changes observed in the instrumental record (mean square error  =  0.003 m2). The Bayesian hierarchical model provides a single, unifying framework for reconstructing and analyzing sea-level change through time. This approach is suitable for reconstructing other paleoenvironmental variables (e.g., temperature) using biological proxies.

2016-02-29T00:00:00Z Doan, Thinh K. Haslett, John Parnell, Andrew C. http://hdl.handle.net/10197/7964 2016-09-19T14:58:28Z 2015-03-25T00:00:00Z

Joint inference of misaligned irregular time series with application to Greenland ice core data Doan, Thinh K.; Haslett, John; Parnell, Andrew C. Ice cores provide insight into the past climate over many millennia. Due to ice compaction, the raw data for any single core are irregular in time. Multiple cores have different irregularities; and when considered together, they are misaligned in time. After processing, such data are made available to researchers as regular time series: a data product. Typically, these cores are independently processed. This paper considers a fast Bayesian method for the joint processing of multiple irregular series. This is shown to be more efficient than the independent alternative. Furthermore, our explicit framework permits a reliable modelling of the impact of the multiple sources of uncertainty. The methodology is illustrated with the analysis of a pair of ice cores. Our data products, in the form of posterior marginals or joint distributions on an arbitrary temporal grid, are finite Gaussian mixtures. We can also produce process histories to study non-linear functionals of interest. More generally, the concept of joint analysis via hierarchical Gaussian process models can be widely extended, as the models used can be viewed within the larger context of continuous space–time processes.

2015-03-25T00:00:00Z Daly, Donal Deakin, Jenny Craig, Matthew Mockler, Eva M. et al. http://hdl.handle.net/10197/7910 2016-09-08T16:01:32Z 2016-04-13T00:00:00Z

Progress in Implementation of the Water Framework Directive in Ireland Daly, Donal; Deakin, Jenny; Craig, Matthew; Mockler, Eva M.; et al. Successful implementation of the Water Framework Directive is vital to water resources management in Ireland. Based on lessons learned from the 1st cycle of implementation, more effective governance arrangements have been put in place, the EPA has been given additional responsibilities and community engagement has been given a high priority. Integrated catchment management (ICM) has become the accepted philosophy and approach. ICM requires catchments to be the appropriate organising landscape unit for water management, which is undertaken at five scales: site/field; water body (almost 5,000 groundwater, river, lake, transitional and coastal); subcatchment (583); catchment (46) and river basin (one national and two international). A comprehensive characterisation process is being undertaken which allocates all WBs into At Risk, Not at Risk and Review categories, whereby At Risk WBs require actions and resources to improve the situation. Geoscientific information and understanding are critical to the characterisation process. Initial subcatchment and catchment characterisation is due for completion in early 2017. Consideration of environmental objectives and mitigation measures has commenced, and will be finalised for the River Basin Management Plan due for publication in December 2017. A new tool, the WFD Application, has been developed to enable ready access to water quality data and the outcomes of the characterisation work. The Application is being made available through the development of a new 'water hub' website called catchments.ie. International Association of Hydrogeologists (IAH) (Irish Group) Sustaining Ireland’s Water Future: The Role of Groundwater, Tullamore, Co. Offaly, Ireland, 12-13 April 2016

2016-04-13T00:00:00Z Gonzalez Merino, Alberto Costas de la Peña, Luis González, Arturo http://hdl.handle.net/10197/7909 2016-09-08T15:35:36Z 2016-08-30T00:00:00Z

Dynamic analysis of the nonlinear response of high density fuel storage racks Gonzalez Merino, Alberto; Costas de la Peña, Luis; González, Arturo High Density Spent Fuel Storage racks are steel structures designed to hold nuclear spent fuel assemblies removed from the nuclear power reactor. Weighing around 60 tons, they are 5m high free-standing structures resting on the floor of a 12m depth pool and separated by only a few centimetres. Their underwater seismic response is a troubling safety issue, especially after Fukushima nuclear disaster. However, only limited basic guidelines have been provided as regulatory design criteria to date. The racks’ design deals with a very highly nonlinear behaviour, a transient dynamic response and a fluid-structure interaction problem. Industry is currently using available computer-aided finite element analysis software to solve the design problem in a cost-effective manner but some dispersion of results still exists. Hence, the nuclear regulatory authorities are requiring an evaluation of the current uncertainty associated to the assessment of rack displacements, rocking and maximum forces on supports. This paper discusses the main difficulties faced during the seismic analysis and presents an ad-hoc analysis methodology based on the hydrodynamic mass concept which takes advantage of a simplifying thermal analogy. The methodology, implemented in ANSYS FE Mechanical is hereby described for a reduced scale 2-rack model where the coupling effect of water in the dynamic motion of immersed racks is quantified and displacements and forces are provided. Finally, methodology assumptions are discussed and lessons learnt about the behaviour trends are summarized. Civil Engineering Research in Ireland (CERI 2016), Galway, Ireland, 29-30 August 2016

2016-08-30T00:00:00Z Packham, I. Archbold, Marie A. Mockler, Eva M. Bruen, Michael et al. http://hdl.handle.net/10197/7890 2017-04-24T12:24:30Z 2016-07-14T00:00:00Z

CCT: A simple prioritisation tool for identifying critical source areas for managing waterborne pollutants Packham, I.; Archbold, Marie A.; Mockler, Eva M.; Bruen, Michael; et al. Catchment characterisation integrates an understanding of the physical characteristics, sources, pathways and pressures in a catchment, and provides a scientific basis for evaluation of mitigation measures required by the EU Water Framework Directive. In Ireland, the Catchment Characterisation Tool (CCT) has been developed to assess the potential risk posed by nitrate and phosphate from diffuse agricultural sources to surface and groundwater receptors, and to delineate critical source areas in Irish sub-catchments (typically from 10 – 200 km2 in size) as a means of facilitating the targeting of mitigation measures. The CCT for nitrate, which is presented in this paper, is a steady-state model based on annual average nitrate loadings transported from their land sources along near surface and subsurface pathways to each receptor. The GIS-based model links spatial datasets, such as land-use, soil and geological properties with transport and delivery factors derived from field and literature data. The model can distinguish between the contaminant loads transported through each of the major hydrological pathways. The CCT calculates the nitrate loading to surface waters following the source-pathway-receptor methodology, and results are displayed in pollution impact potential maps. A key issue with such export models is how they can be validated. This paper describes the validation methodology which compared a national dataset of measured nitrate concentrations in Irish water bodies with values predicted by the CCT. More detailed comparisonswith local test catchments that are more intensively monitored showed satisfactory correlation between the CCT predictions and measured concentrations. This paper thus shows both the potential of the CCT approach, the likely range of the uncertainty to be expected, and the issues that arise from its validation. 8th International Congress on Environmental Modelling and Software in Toulouse, France, 10-14 July 2016

2016-07-14T00:00:00Z Mockler, Eva M. http://hdl.handle.net/10197/7887 2016-09-07T11:51:43Z 2016-07-14T00:00:00Z

Development of a Nutrient Load Apportionment Modelling Toolbox Mockler, Eva M. Where surface waters are impacted by excess nutrients, understanding the sources of those nutrients is key to the development of effective, targeted, mitigation measures. In Ireland, nutrient emissions remains the top suspected cause of surface waters not achieving the required Good Status, as defined by the Water Framework Directive (WFD). Hence, a toolbox has been developed to predict the sources of nutrients contributing to these emissions, and to assess future pressures and the likely effectiveness of targeted mitigation scenarios. This Source Load Apportionment Model (SLAM) supports catchment managers by providing scientifically robust evidence to back-up decision-making in relation to reducing nutrient pollution. The SLAM is a source-oriented model that calculates the nitrogen & phosphorus exported from each sector (e.g. pasture, forestry, wastewater discharges) that contribute to nutrient loads in a river. The SLAM was built as a modular framework in ArcGIS ModelBuilder to encourage continuous development by a range of scientific experts without the need for programming skills. Model output ispresented as maps andtablesshowing the proportionsof nutrientemissions to water attributed to each sector in each sub-catchment. Results for the Suir catchment, in the South East of Ireland, indicate that diffuse losses of nutrients from pasture arethe dominant source of nitrogen and both wastewater discharges and losses from pasture are dominant for phosphorus. The Irish EPA has incorporated these model results into the WFD characterisation process for Irish catchments. International Environmental Modelling & Software Society (iEMSs) 8th International Congress on Environmental Modelling and Software, Toulouse, France, 10-14 July 2016

2016-07-14T00:00:00Z Prat-Guitart, Nuria Rein, Guillermo Hadden, Rory M. Belcher, Claire M. Yearsley, Jonathan M. http://hdl.handle.net/10197/7881 2017-02-14T16:49:32Z 2016-12-01T00:00:00Z

Effects of spatial heterogeneity in moisture content on the horizontal spread of peat fires Prat-Guitart, Nuria; Rein, Guillermo; Hadden, Rory M.; Belcher, Claire M.; Yearsley, Jonathan M. The gravimetric moisture content of peat is the main factor limiting the ignition and spread propagation of smouldering fires. Our aim is to use controlled laboratory experiments to better understand how the spread of smouldering fires is influenced in natural landscape conditions where the moisture content of the top peat layer is not homogeneous. In this paper, we study for the first time the spread of peat fires across a sharp spatial gradient of two moisture contents (dry/wet) in the laboratory. The experiments were undertaken using an open-top insulated box (22×18×6 cm) filled with milled peat. The peat was ignited at one side of the box initiating smouldering and horizontal spread. Measurements of the peak temperature inside the peat, fire duration and longwave thermal radiation from the burning samples revealed local changes of the smouldering behaviour in response to sharp gradients in moisture content. Both, peak temperatures and radiation in the wetter peat (after the moisture gradient) were sensitive to the drier moisture conditions (preceeding the moisture gradient). Drier peat conditions before the moisture gradient led to higher temperatures and higher radiation flux from the fire during the first 6 cm of horizontal spread into a wet peat patch. The total spread distance into a wet peat patch was affected by the moisture content gradient. We predicted that in most peat moisture gradients of relevance to natural ecosystems the fire self-extinguishes within the first 10 cm of horizontal spread into a wet peat patch. Spread distances of more than 10 cm are limited to wet peat patches below 160% moisture content (mass of water per mass of dry peat). We found that spatial gradients of moisture content have important local effects on the horizontal spread and should be considered in field and modelling studies.

2016-12-01T00:00:00Z Mockler, Eva M. O'Loughlin, Fiachra Bruen, Michael http://hdl.handle.net/10197/7875 2016-09-06T11:34:42Z 2016-05-01T00:00:00Z

Understanding hydrological flow paths in conceptual catchment models using uncertainty and sensitivity analysis Mockler, Eva M.; O'Loughlin, Fiachra; Bruen, Michael Increasing pressures on water quality due to intensification of agriculture have raised demands for environmental modeling to accurately simulate the movement of diffuse (nonpoint) nutrients in catchments. As hydrological flows drive the movement and attenuation of nutrients, individual hydrological processes in models should be adequately represented for water quality simulations to be meaningful. In particular, the relative contribution of groundwater and surface runoff to rivers is of interest, as increasing nitrate concentrations are linked to higher groundwater discharges. These requirements for hydrological modeling of groundwater contribution to rivers initiated this assessment of internal flow path partitioning in conceptual hydrological models. In this study, a variance based sensitivity analysis method was used to investigate parameter sensitivities and flow partitioning of three conceptual hydrological models simulating 31 Irish catchments. We compared two established conceptual hydrological models (NAM and SMARG) and a new model (SMART), produced especially for water quality modelling. In addition to the criteria that assess streamflow simulations, a ratio of average groundwater contribution to total streamflow was calculated for all simulations over the 16 year study period. As observations time-series of groundwater contributions to streamflow are not available at catchment scale, the groundwater ratios were evaluated against average annual indices of base flow and deep groundwater flow for each catchment. The exploration of sensitivities of internal flow path partitioning was a specific focus to assist in evaluating model performances. Results highlight that model structure has a strong impact on simulated groundwater flow paths. Sensitivity to the internal pathways in the models are not reflected in the performance criteria results. This demonstrates that simulated groundwater contribution should be constrained by independent data to ensure results within realistic bounds if such models are to be used in the broader environmental sustainability decision making context.

2016-05-01T00:00:00Z Porter, Amanda S. Evans-FitzGerald, Christiana McElwain, Jennifer C. Yiotis, Charilaos Elliott-Kingston, Caroline http://hdl.handle.net/10197/7867 2016-09-05T16:23:46Z 2015-09-22T00:00:00Z

How well do you know your growth chambers? Testing for chamber effect using plant traits Porter, Amanda S.; Evans-FitzGerald, Christiana; McElwain, Jennifer C.; Yiotis, Charilaos; Elliott-Kingston, Caroline Background: Plant growth chambers provide a controlled environment to analyse the effects of environmental parameters (light, temperature, atmospheric gas composition etc.) on plant function. However, it has been shown that a ‘chamber effect’ may exist whereby results observed are not due to an experimental treatment but to inconspicuous differences in supposedly identical chambers. In this study, Vicia faba L. 'Aquadulce Claudia' (broad bean) plants were grown in eight walk-in chambers to establish if a chamber effect existed, and if so, what plant traits are best for detecting such an effect. A range of techniques were used to measure differences between chamber plants, including chlorophyll fluorescence measurements, gas exchange analysis, biomass, reproductive yield, anatomical traits and leaf stable carbon isotopes. Results and discussion: Four of the eight chambers exhibited a chamber effect. In particular, we identified two types of chamber effect which we term 'resolvable' or 'unresolved'; a resolvable chamber effect is caused by malfunctioning components of a chamber and an unresolved chamber effect is caused by unknown factors that can only be mitigated by appropriate experimental design and sufficient replication. Not all measured plant traits were able to detect a chamber effect and no single trait was capable of detecting all chamber effects. Fresh weight and flower count detected a chamber effect in three chambers, stable carbon isotopes (δ13C) and net rate CO2 assimilation (An) identified a chamber effect in two chambers, stomatal conductance (gs) and total performance index detected an effect only in one chamber. Conclusion: (1) Chamber effects can be adequately detected by fresh weight measurements and flower counts on Vicia faba plants. These methods were the most effective in terms of detection and most efficient in terms of time. (2) δ13C, gs and An measurements help distinguish between resolvable and unresolved chamber effects. (3) Unresolved chamber effects require experimental unit replication while resolvable chamber effects require investigation, repair and retesting in advance of initiating further experiments.

2015-09-22T00:00:00Z Evans-FitzGerald, Christiana Porter, Amanda S. Yiotis, Charilaos Elliott-Kingston, Caroline McElwain, Jennifer C. http://hdl.handle.net/10197/7823 2016-08-22T16:23:59Z 2016-01-01T00:00:00Z

Co-ordination in morphological leaf traits of early diverging angiosperms is maintained following exposure to experimental palaeoatmospheric conditions of sub-ambient O2 and elevated CO2 Evans-FitzGerald, Christiana; Porter, Amanda S.; Yiotis, Charilaos; Elliott-Kingston, Caroline; McElwain, Jennifer C. In order to be successful in a given environment a plant should invest in a vein and stomatal network that ensures balance between both water supply and demand. Vein density (Dv) and stomatal density (SD) have been shown to be strongly positively correlated in response to a range of environmental variables in more recently evolved plant species, but the extent of this relationship has not been confirmed in earlier diverging plant lineages. In order to examine the effect of a changing atmosphere on the relationship between Dv and SD, five early-diverging plant species representing two different reproductive plant grades were grown for seven months in a palaeo-treatment comprising an O2:CO2 ratio that has occurred multiple times throughout plant evolutionary history. Results show a range of species-specific Dv and SD responses to the palaeo-treatment, however we show that the strong relationship between Dv and SD under modern ambient atmospheric composition is maintained following exposure to the palaeo-treatment. This suggests strong co-ordination between vein and stomatal traits even under relatively extreme environmental change. This co-ordination supports existing plant function proxies that use the distance between vein endings and stomata (Dm) to infer plant palaeo-physiology such as assimilation rate, and as a result, lends confidence to future application of palaeo-CO2 proxy models that require robust estimates of palaeo-assimilation rate as key initialisation parameters. 

2016-01-01T00:00:00Z Gonzalez Merino, Alberto Costas de la Peña, Luis González, Arturo http://hdl.handle.net/10197/7810 2016-08-22T11:11:14Z 2016-07-30T00:00:00Z

Uncertainties in seismic design of free-standing HDSFS Racks Gonzalez Merino, Alberto; Costas de la Peña, Luis; González, Arturo High Density Spent Fuel Storage (HDSFS) racks are structures designed to hold nuclear spent fuel assemblies removed from the nuclear power reactor after having been irradiated. They are used in the first step of the waste management process, during the wet storage. The underwater seismic response of HDSFS racks is a troubling safety issue. Since they are 12 m submerged free standing multi-body structures loaded with radioactive fuel, their design remains as complex as crucial [1] [2]. The design deals with a Fluid-Structure Interaction (FSI) problem, a transient dynamic response and a very highly nonlinear behaviour. Several cost-effective industrial approaches have been used in these calculations to date, but some dispersion of results still exists. Therefore, the regulatory authorities are requiring an evaluation of the uncertainties in the methodology. Equipos Nucleares, S.A. (ENSA) is a worldwide expert in racks design and construction [3] and has recently launched a research project to improve the understanding of the phenomena. The latter is funded by the European Comision1 and aimed to identify, evaluate and reduce the uncertainties involved in the calculations. In this paper, the state of the art and the current sources of uncertainty are discussed. 9th International Youth Nuclear Congress (IYNC 2016), Hangzhou, China, 24-30 July 2016

2016-07-30T00:00:00Z Elliott-Kingston, Caroline Haworth, Matthew Yearsley, Jonathan M. McElwain, Jennifer C. et al. http://hdl.handle.net/10197/7804 2016-09-01T15:51:37Z 2016-01-01T00:00:00Z

Does size matter? Atmospheric CO2 may be a stronger driver of stomatal closing rate than stomatal size in taxa that diversified under low CO2 Elliott-Kingston, Caroline; Haworth, Matthew; Yearsley, Jonathan M.; McElwain, Jennifer C.; et al. (1) One strategy for plants to optimise stomatal function is to open and close their stomata quickly in response to environmental signals.  It is generally assumed that small stomata can alter aperture faster than large stomata. (2) We tested the hypothesis that species with small stomata close faster than species with larger stomata in response to darkness by comparing rate of stomatal closure across an evolutionary range of species including ferns, cycads, conifers and angiosperms under controlled ambient conditions (380ppm CO2; 20.9% O2).  (3) The two species with fastest half-closure time and the two species with slowest half-closure time had large stomata while the remaining three species had small stomata, implying that closing rate was not correlated with stomatal size in these species. Neither was response time correlated with stomatal density, phylogeny, functional group or life strategy. (4) Our results suggest that past atmospheric CO2 concentration during time of taxa diversification may influence stomatal response time.  We show that species which last diversified under low or declining atmospheric CO2 concentration close stomata faster than species that last diversified in a high CO2 world.  Low atmospheric [CO2] during taxa diversification may have placed a selection pressure on plants to accelerate stomatal closing to maintain adequate internal CO2 and optimise water use efficiency.

2016-01-01T00:00:00Z Mockler, Eva M. O'Loughlin, Fiachra Bruen, Michael http://hdl.handle.net/10197/7798 2016-08-19T11:27:35Z 2015-11-17T00:00:00Z

Understanding Hydrological Flow Paths in Conceptual Catchment Models To Improve Water Quality Modelling Mockler, Eva M.; O'Loughlin, Fiachra; Bruen, Michael Increasing pressures on water quality due to intensification of agriculture have increased the need for environmental modelling to accurately simulate the movement of diffuse (nonpoint) nutrients in catchments. As hydrological flows drive the movement and attenuation of nutrients, individual hydrological processes in models should be adequately represented for water quality simulations to be meaningful. In particular, the relative contribution of groundwater and surface runoff to rivers is of interest, as, for example, higher nitrate concentrations in surface waters are strongly linked to catchments with proportionately larger groundwater contributions to the river. In this study, uncertainty analysis was used to investigate parameter sensitivities and flow partitioning of three conceptual hydrological models simulating 31 Irish catchments. We compared two established conceptual hydrological models (NAM and SMARG) and a new model (SMART), produced especially for water quality modelling. In addition to the criteria that assess streamflow simulations, a ratio of average groundwater contribution to total streamflow was calculated for all simulations over the 16 year study period. As measured time-series of groundwater contributions to streamflow are not available at catchment scale, the groundwater ratios were evaluated against average annual indices of base flow (from the OPW) and estimates of deep groundwater flow (from the Geological Survey of Ireland) for each catchment. The exploration of sensitivities of internal flow path partitioning was a specific focus to assist in evaluating model performances. Results highlight that model structure has a strong impact on simulated groundwater flow path contributions. Sensitivities to the internal pathways in the models are not reflected in the usual (flood forecasting) performance criteria results. This demonstrates that simulated groundwater contribution should be constrained by independent data to ensure results within realistic bounds if such models are to be used in the broader environmental sustainability decision making context. Irish National Hydrology Conference, Athlone, Co. Westmeath, Ireland, 17 November 2015

2015-11-17T00:00:00Z Milana, Giulia Banisoleiman, Kian González, Arturo http://hdl.handle.net/10197/7770 2016-07-21T16:01:39Z 2016-06-30T00:00:00Z

Fatigue Life Assessment Methods: the Case of Ship Unloaders Milana, Giulia; Banisoleiman, Kian; González, Arturo This paper reviews methodologies for fatigue analysis with emphasis on ship unloaders. Maintaining the performance of ship unloaders at a satisfactory level is essential for any port's operation in order to comply with the global demand of shipping and trading. Ship unloaders are subject to alternating operational loadings and to adverse environmental conditions, and as a result, they show a rapid rate of deterioration that makes them susceptible to failure by cumulative damage processes such as corrosion and fatigue. The purpose of this paper is to review key features of the most common methodologies for fatigue analysis and to underline the limitations and uncertainties involved. Finally, developments in reliability-based approaches are suggested for a more accurate fatigue assessment of ship unloaders. 1st International Conference on Natural Hazards & Infrastructure (ICONHIC 2016): Protection, Design and Rehabilitation, Chania, Greece, 28-30 June 2016

2016-06-30T00:00:00Z Fallah, Sogol Gavin, Kenneth Moradabadi, Ehsan http://hdl.handle.net/10197/7601 2017-06-01T01:00:10Z 2015-06-01T00:00:00Z

Estimation of spudcan penetration using a probabilistic Eulerian finite element analysis Fallah, Sogol; Gavin, Kenneth; Moradabadi, Ehsan The probabilistic approach was employed to consider the uncertainties in prediction of spudcan penetration in clay. The Latin Hypercube Sampling method was used to generate 300 sample sets of input parameters based on the laboratory and field data. Each set of input parameters was used in conducting Coupled Eulerian Lagrangian finite element analysis. The probabilistic density function of the penetration depth under the maximum applied preload was obtained. The comparison of the results to the measured data showed that the introduced method can produce reasonable prediction of spudcan penetration considering the uncertainties involved in this problem.

2015-06-01T00:00:00Z Prat-Guitart, Nuria Rein, Guillermo Hadden, Rory M. Belcher, Claire M. Yearsley, Jonathan M. http://hdl.handle.net/10197/7574 2016-04-22T13:48:21Z 2016-03-03T00:00:00Z

Propagation probability and spread rate of self-sustained smouldering fires under controlled moisture content and bulk density conditions Prat-Guitart, Nuria; Rein, Guillermo; Hadden, Rory M.; Belcher, Claire M.; Yearsley, Jonathan M. The consumption of large areas of peat during wildfires is due to self-sustained smouldering fronts that can remain active for weeks. We studied the effect of peat moisture content and bulk density on the horizontal propagation of smouldering fire in laboratory-scale experiments. We used milled peat with moisture contents between 25 and 250% (mass of water per mass of dry peat) and bulk densities between 50 and 150 kg m–3. An infrared camera monitored ignition, spread and extinction of each smouldering combustion front. Peats with a bulk density below 75 kg m–3 and a moisture content below 150% self-sustained smouldering propagation for more than 12 cm. Peat with a bulk density of 150 kg m–3 could self-sustain smouldering propagation up to a critical moisture content of 115%. A linear model estimated that increasing both moisture content and bulk density significantly reduced the median fire spread rate (which ranged between 1 and 5 cm h–1). Moisture content had a stronger effect size on the spread rate than bulk density. However, the effect of bulk density on spread rate depends upon the moisture content, with the largest effect of bulk density at low moisture contents.

2016-03-03T00:00:00Z Truong-Hong, Linh Laefer, Debra F. http://hdl.handle.net/10197/7509 2016-02-16T09:54:39Z 2015-09-25T00:00:00Z

Documentation of Bridges by Terrestrial Laser Scanner Truong-Hong, Linh; Laefer, Debra F. Bridge structures are subjected to deterioration due to excessive usage, overloading, and aging material. For the last two decades, a significant amount research has been developed for collecting data for structural health monitoring. Yet, visual investigation with an on-site inspector remains the predominant method. This is true despite the highly subjective and time consuming aspects of this approach. Alternatively, terrestrial laser scanning can acquire surface details of structures quickly and accurately and is, thus, an emerging means to overcome the shortcomings of direct visual inspection. This paper presents a procedure for data collection for bridge inspection documentation and proposes a 'cell-based method' for determination of structure deterioration (involving vertical deformation and lateral distortion), as well as surface loss due to corrosion. The Guinness Bridge built in 1880s located in Dublin council, Ireland is selected as a case study to illustrate the efficacy of the proposed method. IABSE Geneva Conference 2015, Geneva, Switzerland, 23 - 25 September 2015

2015-09-25T00:00:00Z Rezaiguia, Abdelouahab Ouelaa, N. Laefer, Debra F. http://hdl.handle.net/10197/7496 2017-10-01T01:00:22Z 2015-10-01T00:00:00Z

Dynamic amplification of a multi-span orthotropic bridge deck under vehicular movement Rezaiguia, Abdelouahab; Ouelaa, N.; Laefer, Debra F. The response of a multi-span, continuous orthotropic bridge deck during truck loading is investigated to better understand the dynamic interaction between moving vehicles and highway bridge decks. The present study is based on a recently published, semi-analytical approach for free vibration in which the modal superposition method incorporates intermodal coupling. Herein, the bridge deck is modeled as a jointless, multi-span, orthotropic plate, and the vehicle is modeled as a dynamic, multi-body system. The road surface roughness randomness is modeled as a normal, stationary, random process described by its Power Spectral Density (PSD). The coupled equations of the motion vehicle/bridge deck are solved by Newmark’s method. An iterative process in each time step is performed to find the equilibrium between the bridge deck and vehicle tires using an uncoupled algorithm previously developed by other authors. Two numerical application examples are presented: an isotropic and an orthotropic, three-span bridge deck both crossed by an AASHTO-based vehicle model. In example one, the intermodal coupling affects the dynamic deflection of bridge deck but only slightly. Example two demonstrates that the loading mode and the vehicle speed have a significant influence on the Dynamic Amplification Factor. However, the most important parameter to affect the dynamic vehicle/bridge deck interaction force is the road’s surface roughness, as has been shown for other bridge types under various load conditions.

2015-10-01T00:00:00Z Truong-Hong, Linh Laefer, Debra F. http://hdl.handle.net/10197/7495 2016-02-12T15:57:58Z 2014-08-13T00:00:00Z

Using Terrestrial Laser Scanning for Dynamic Bridge Deflection Measurement Truong-Hong, Linh; Laefer, Debra F. Heavy vehicular traffic and aggressive environmental conditions can cause unexpected bridge deterioration, thus requiring periodic inspections to identify and assess possible defects. One indicator is the amount of vertical deflection that occurs during loading. Monitoring vertical bridge deflection through traditional surveying typically requires multiple instruments and extensive time in the field, along with their affiliated costs. A terrestrial laser scanner (TLS) can generate a million data points per second with millimeter level accuracy, thus offering the possibility of changing how vertical deflections of bridge girders are checked. This paper presents a preliminary investigation into using TLS to collecting vertical bridge displacements during dynamic loading. In this work, a point-surface based method is proposed to calculate the difference in elevation of a bridge girder at unloaded and loaded conditions. The technique is applied to the Loughbrickland Bridge in Northern Ireland. IABSE Istanbul Bridge Conference, Istanbul, Turkey, 11 - 13 August 2014

2014-08-13T00:00:00Z Truong-Hong, Linh Laefer, Debra F. http://hdl.handle.net/10197/7494 2016-02-12T15:54:13Z 2014-09-05T00:00:00Z

Application of Terrestrial Laser Scanner in Bridge Inspection: Review and an Opportunity Truong-Hong, Linh; Laefer, Debra F. Heavy traffic and aggressive environmental conditions can cause unexpected bridge deterioration. Traditional condition evaluation is expensive. An alternative is Terrestrial laser scanning (TLS) which is a non-contact approach that safe, fast, and applicable to a range of weather conditions. This paper reviews applications of TLS on bridge measurement involving geometric documentation, surface defect determination, and corrosion evaluation, and crack identification. Currently, most post-processing of TLS is manual or within third party software. This paper discusses potential approaches to automatic post-processing. 37th IABSE Symposium: Engineering for Progress, Nature and People, Madrid, Spain, 3 - 5 September 2014

2014-09-05T00:00:00Z Clarke, Julie Laefer, Debra F. http://hdl.handle.net/10197/7484 2016-02-11T09:25:23Z 2014-02-01T00:00:00Z

Evaluation of risk assessment procedures for buildings adjacent to tunnelling works Clarke, Julie; Laefer, Debra F. Risk assessment procedures for underground projects form a key component of pre-construction efforts since resulting ground movements may cause damage to adjacent structures. Particularly for urban tunnelling works, surface settlements may impinge on a vast number of structures and can result in significant lawsuits unless the appropriate building protection measures are implemented. Although the understanding of tunnelling induced building damage has advanced greatly in recent decades, damage and litigation persist. Hence, this paper reconsiders the pre-construction risk assessment procedures undertaken during the generation of an Environmental Impact Statement (EIS) by formally including considerations relating to a building's historical significance, present usage, and current physical condition. In doing so, a holistic approach to risk assessment is proposed, allowing for project resources to be targeted towards buildings that are most at risk. This is demonstrated through a Class A prediction for a section of an upcoming underground railway system in which 14% of the selected study area of 220 buildings are identified to be at risk. Results are compared to those produced by the official EIS where building vulnerabilities are considered in isolation from the damage prediction assessment and just 5% of buildings are considered to be at risk. The proposed methodology offers a standardised procedure for incorporating both cultural and physical aspects of each building, thereby providing a more systematic, comprehensive procedure for pre-construction risk assessment than previously available.

2014-02-01T00:00:00Z Truong-Hong, Linh Falter, Holger Lennon, Donal Laefer, Debra F. http://hdl.handle.net/10197/7476 2016-02-10T09:43:31Z 2016-01-08T00:00:00Z

Framework for Bridge Inspection with Laser Scanning Truong-Hong, Linh; Falter, Holger; Lennon, Donal; Laefer, Debra F. For the last two decades, a significant amount research has been developed for collecting data for bridge inspection. Yet, visual investigation with an on-site inspector remains the predominant method; however is the highly subjective and time consuming. Alternatively, terrestrial laser scanner (TLS) can acquire surface details of structures quickly and accurately and is, thus, an emerging means to overcome the shortcomings of direct visual inspection. This paper presents a framework of bridge inspection using TLS data, where a strategy of processing TLS data for deformation measurement, damage detection, and reconstruction of three dimension (3D) as-built models are explored. Demonstration of the application in bridge inspection is also provided. EASEC-14 Structural Engineering and Construction, Ho Chi Minh City, Vietnam, 6 - 8 January 2016

2016-01-08T00:00:00Z Truong-Hong, Linh Laefer, Debra F. http://hdl.handle.net/10197/7475 2016-02-10T09:30:19Z 2015-10-03T00:00:00Z

Evaluation of Automatically Generated 2D Footprints from Urban LiDAR Data Truong-Hong, Linh; Laefer, Debra F. Over the last decade, several automatic approaches have been proposed to extract and reconstruct 2D building footprints and 2D road profiles from ALS data, satellite images, and/or aerial imagery. Since these methods have to date been applied to various data sets and assessed through a variety of different quality indicators and ground truths, comparing the relative effectiveness of the techniques and identifying their strengths and short-comings has not been possible in a systematic way. This open contest was designed to overcoming this shortcoming. Specifically, participants were asked to submit 2D footprints (building outlines and road profiles) derived from ALS data from a highly dense data (approximately 225 points/m2) across a 1km2 of central Dublin, Ireland. The proposed evaluation strategies were designed to measure not only the capacity of each method to detect and reconstruct 2D buildings and roads but also the quality of the reconstructed building and road models in terms of shape similarity and positional accuracy. The evaluated methods will represent those submitted as part of IQPC15. ISPRS Geospatial Week 2015, La Grande Motte, France, 28 September - 3 October 2015

2015-10-03T00:00:00Z Singh, Manmeet Laefer, Debra F. http://hdl.handle.net/10197/7467 2016-02-09T11:09:50Z 2015-01-22T00:00:00Z

Recent Trends and Remaining Limitations in Urban Microclimate Models Singh, Manmeet; Laefer, Debra F. Problems such as natural ventilation, pollutant dispersion, changes in wind environments, and urban heat islands are gaining increasing prominence in both public concern and research. In response urban microclimate modelling researchers are continually striving to develop new strategies to rapidly and inexpensively generate more accurate results. Numerical modelling is a common way to address these concerns. However, to generate realistic results requires significant investment in model creation, especially with respect to the detail to which a model is populated. This paper provides an overview about this and other recent trends within the research community by considering nearly 100 recent papers from 2010-2013. Major trends related to Comprehensive Turbulent Aerosol dynamics and Gas chemistry (CTAG) and perceptual fidelity.

2015-01-22T00:00:00Z Salam Al-Sabah, Abd Laefer, Debra F. http://hdl.handle.net/10197/7456 2016-02-08T10:48:51Z 2015-01-01T00:00:00Z

Meshfree Sequentially Linear Analysis of Concrete Salam Al-Sabah, Abd; Laefer, Debra F. A new, meshfree method employing the node-based, smoothed point interpolation method (NS-PIM) is presented as an alternative to the nonlinear finite-element approach for concrete members. The nonlinear analysis is replaced by sequentially linear analyses (SLA), and a smeared, fixed concrete cracking model was used. A notched concrete beam was employed for validation. Using a crack band width factor of 2.0 and 10-mm nodal spacing, the peak load differed by only 3.5% from experimental results. Overall results were similar to experimental ones, as well as to those published by researchers using finite-element SLA. The approach provides two major advantages over finite-element-based SLA: (1) nodal distortion insensitivity, and (2) nodal spacing insensitivity.

2015-01-01T00:00:00Z Abuwarda, Saleh Laefer, Debra F. http://hdl.handle.net/10197/7455 2016-02-08T10:41:52Z 2014-02-28T00:00:00Z

Aerial Flightpath Considerations for Documenting Urban Heritage Using Laser Scanning Abuwarda, Saleh; Laefer, Debra F. This paper provides guidance for the planning of urban heritage documentation using aerial laser scanning. The paper presents standard industrial considerations typically undertaken by commercial data providers and the additional factors that such be raised in the planning stage when urban heritage documentation is the goal. Virtual Cultural Heritage in Ireland, Dublin, Ireland, 27 - 28 February 2014

2014-02-28T00:00:00Z Truong-Hong, Linh Laefer, Debra F. http://hdl.handle.net/10197/7451 2016-02-05T13:01:18Z 2014-08-01T00:00:00Z

Octree-based, automatic building façade generation from LiDAR data Truong-Hong, Linh; Laefer, Debra F. This paper introduces a new, octree-based algorithm to assist in the automated conversion of laser scanning point cloud data into solid models appropriate for computational analysis. The focus of the work is for typical, urban, vernacular structures to assist in better damage prediction prior to tunnelling. The proposed FaçadeVoxel algorithm automatically detects boundaries of building façades and their openings. Next, it checks and automatically fills unintentional occlusions. The proposed method produced robust and efficient reconstructions of building models from various data densities. When compared to measured drawings, the reconstructed building models were in good agreement, with only 1% relative errors in overall dimensions and 3% errors in openings. In addition, the proposed algorithm was significantly faster than other automatic approaches without compromising accuracy.

2014-08-01T00:00:00Z Aljumaily, Harith Laefer, Debra F. Cuadra, Dolores http://hdl.handle.net/10197/7450 2016-02-05T12:59:22Z 2015-08-28T00:00:00Z

A Big Data Approach for 3D Building Extraction from Aerial Laser Scanning Aljumaily, Harith; Laefer, Debra F.; Cuadra, Dolores This paper proposes a Big Data approach to automatically identify and extract buildings from a digital surface model created from aerial laser scanning data. The approach consists of two steps. The first step is a MapReduce process where neighboring points in a digital surface model are mapped into cubes. The second step uses a non-MapReduce algorithm first to remove trees and other obstructions and then to extract adjacent cubes. According to this approach, all adjacent cubes belong to the same object and an object is a set of adjacent cubes that belong to one or more adjacent buildings. Finally, an evaluation study is presented for a section of Dublin, Ireland to demonstrate the applicability of the approach resulting in a 92% quality level for the extraction of 106 buildings over 1 km2 including buildings that had more than 10 adjacent components of different heights and complicated roof geometries. The proposed approach is notable not only for its Big Data context but its usage of vector data.

2015-08-28T00:00:00Z Cao, Van-Hung Chu, Xuan-Khoi Le-Khac, Nhien-An Kechadi, Tahar Laefer, Debra F. Truong-Hong, Linh http://hdl.handle.net/10197/7448 2016-02-05T12:48:16Z 2015-07-10T00:00:00Z

Toward a new approach for massive LiDAR data processing Cao, Van-Hung; Chu, Xuan-Khoi; Le-Khac, Nhien-An; Kechadi, Tahar; Laefer, Debra F.; Truong-Hong, Linh Laser scanning (also known as Light Detection And Ranging) has been widely applied in various application. As part of that, aerial laser scanning (ALS) has been used to collect topographic data points for a large area, which triggers to million points to be acquired. Furthermore, today, with integrating full wareform (FWF) technology during ALS data acquisition, all return information of laser pulse is stored. Thus, ALS data are to be massive and complexity since the FWF of each laser pulse can be stored up to 256 samples and density of ALS data is also increasing significantly. Processing LiDAR data demands heavy operations and the traditional approaches require significant hardware and running time. On the other hand, researchers have recently proposed parallel approaches for analysing LiDAR data. These approaches are normally based on parallel architecture of target systems such as multi-core processors, GPU, etc. However, there is still missing efficient approaches/tools supporting the analysis of LiDAR data due to the lack of a deep study on both library tools and algorithms used in processing this data. In this paper, we present a comparative study of software libraries and new algorithms to optimise the processing of LiDAR data. We also propose new method to improve this process with experiments on large LiDAR data. Finally, we discuss on a parallel solution of our approach where we integrate parallel computing in processing LiDAR data. 2015 2nd IEEE International Conference on Spatial Data Mining and Geographical Knowledge Services (ICSDM 2015), Fuzhou, China, 8 - 10 July 2015

2015-07-10T00:00:00Z Truong-Hong, Linh Laefer, Debra F. http://hdl.handle.net/10197/7447 2016-02-05T12:39:41Z 2015-05-15T00:00:00Z

A Semi-Automatic Member Detection for Metal Bridges Truong-Hong, Linh; Laefer, Debra F. Terrestrial laser scanners (TLSs) are prominent non-contact instruments for acquiring highly detailed geometries of bridge components in only minutes. A TLS can be a strategic instrument for data collection for bridge inspection and documentation, because it can reduce significantly required field time and auxiliary equipment. To deploy a TLS in this field, a semi-automatic method for post-processing a point cloud for documentation of a historic metal bridge is proposed. In this work, generating 3D model of existing structural members and identifying connection characteristics are mainly of interest. The Guinness Bridge built in 1880s in Dublin, Ireland is presented as a case study for the proposed semi-automatic workflow. IABSE Conference Nara: Elegance in Structures, Nara, Japan, 13 - 15 May 2015

2015-05-15T00:00:00Z