Search

Community engaged learning is a form of experiential education with a civic underpinning. Community engaged learning is embedded with the civil engineering curriculum at NUI Galway and is framed by a research orientation, commitments to civic engagement and building university-community partnerships, city-university partnerships and partnerships with other official agencies, so that community users can provide real learning problems and contexts for students and researchers and benefit from the results. This paper presents the positive experience of the authors in facilitating over 300 community engaged learning projects undertaken by undergraduate students in civil engineering at NUI Galway. The paper highlights how well the outlined approach fits with the ideas of engaged scholarship and civic professionalism. Students recognise the long-term value of engaging with community partners, understanding their future role in the community as engineers, reinforcing the idea that their work can respond directly to real needs in the community. The authors would like to acknowledge the funding received from the European Union’s Horizon 2020 research and innovation programme under the GEOFIT project (Grant agreement no. 792210) and TURNKEY RETROFIT project (Grant agreement No 839134), as well as the support of Science Foundation Ireland through the MaREI Centre (Grant No. 12/RC/2302_2). Special thanks is given to all the community partners who engaged with students, the CKI at NUI Galway for assisting with developing the initial partnerships and the ongoing support from Campus Engage within the Irish Universities Association. peer-reviewed

With the impending nearly zero energy building (NZEB) regulations for residential new builds and retrofits for the European Union (EU) housing stock and the percentage of new buildings relative to existing buildings is increasing at a rate of only 1% per year, retrofitting is recognised as the most immediate, pressing and cost effective mechanism to reduce energy consumption and carbon emissions in the building and construction sector. Currently, an Irish residential building Energy Performance Certificates (EPC) indicates the estimation of a buildings’ annual energy usage that is assessed by the Dwelling Energy Assessment Procedure (DEAP). DEAP is the standard method for assessing the energy savings that are made by a residential building through retrofitting its technical characteristics to greater energy efficiency standards. This paper presents the pre-retrofit DEAP results of a sample set of urban social houses in Ireland and compares them to the actual energy usage of the houses highlighting the limitations of DEAP in estimating the pre-retrofit energy usage of the sample set of urban social housing. As many Irish government policies promoting the uptake in residential buildings base their energy savings on DEAP, the need for a more robust assessment procedure for determining the impacts retrofitting a building to a higher energy standard is discussed in addition to the need for engineers to start understanding the behaviour and attitudes towards energy consumption of the people living inside them in order to develop a holistic retrofit design that incorporates both technical and behavioural interventions. The authors wish to acknowledge the financial support from Science Foundation Ireland (SFI) for this research (Grant No. RSF1295). non-peer-reviewed

The growing demand of deep façade retrofits in refurbishment projects across Europe, is often accompanied by low-energy targets and architectural attributes. Factors like variability in context, material, environment and composite construction types and comfort requirements, often complicate the façade retrofits. It becomes difficult to generalise the method of retrofit for each building case. A proper understanding of the diagnostics and intervention principles improves the overall cognizance of retrofits with other systems and sub-systems. Passive retrofit strategies offer great potential to reduce the energy demand of non-domestic buildings. This paper presents a review of research and passive intervention methods that can act as guiding principles for modern façade retrofits for post-war non-domestic buildings and maintain the integrity of the building to provide higher human comfort levels and improved energy performance. The authors would like to acknowledge the support of Science Foundation Ireland through the Career Development Award programme (Grant No. 13/CDA/2200). non-peer-reviewed

This paper presents a part of the ongoing research in the nZEB-Retrofit project in the National University of Ireland, Galway. This research aims to optimise residential building performance by enhancing the key performance metrics of certain performance aspects. In this paper, one of these aspects (lighting) has been discussed, algorithms developed and tested on the living room of a semi-detached dwelling in Dublin. The main objective of the paper is to formulate algorithms to: 1) calculate the power required to illuminate a space up to standard CIBSE design maintenance, 2) calculate the energy consumption and costs per year for lighting that space, and 3) determine power loss and potential energy savings from lighting. For this purpose, key performance indicators (KPIs) that would facilitate the optimisation process have been selected from several national and international standards and guides. The key findings of this paper are that (1) the difference between the provided power of the light to the required power significantly affects the energy costs, and this should be a key consideration in the selection of light source and (2) the output effectiveness of a lighting source is largely dependent on various factors like lamp lumen depreciation (LLD), luminaire dirt depreciation (LDD) and optical and thermal losses. It is inversely related to energy consumption. The authors would like to acknowledge the support of SFI through the CDA programme (Grant No. 13/CDA/2200). non-peer-reviewed

In recent decades, Structural Health Monitoring (SHM) has emerged as an increasingly important tool in Civil Engineering to understand how structures behave during construction and operation. Although SHM is not a new concept, it is only relatively recently that Civil Engineers have adopted SHM for the design, construction and management of civil engineering structures. One of the key benefits of SHM is the improved understanding of insitu structural behaviour. This paper describes the SHM strategy implemented on a recently constructed building to monitor and record the behaviour of a hybrid concrete lattice girder flat slab floor system. Hybrid concrete construction (HCC) combines insitu and precast concrete to maximise the benefits of both forms of construction. HCC offers many advantages for both the designer and contractor and produces simple, buildable and economic structures which can result in faster, safer construction and reduced costs. Sensors were embedded in both the precast and insitu components of the hybrid concrete floor system and are used to monitor various aspects of the behaviour of the floor during the manufacture, construction and operational phase of the building. The information from the real-time monitoring offers the opportunity to compare actual and predicted behaviour using structural codes, such as Eurocodes. The majority of the instrumentation is embedded within the structure so that long-term effects such as creep and shrinkage of concrete components can also be investigated. The authors would like to acknowledge the support of the European Commission Horizon 2020 project Built2Spec (637221). The support of Oran Pre-Cast Ltd. is gratefully acknowledged with respect to installation of sensors in the precast concrete elements. The second author would also like to acknowledge the support of Science Foundation Ireland through the Career Development Award programme (Grant No. 13/CDA/2200) and the National Centre for Marine and Renewable Energy Ireland (MaREI) (Grant no. 12/RC/2302). non-peer-reviewed

Due to stringent environmental regulations, embodied carbon estimates are being used increasingly to assess the environmental impact of major building and infrastructure projects, including their geotechnical components. The focus of this paper is on the ground improvement technique of soil-mixing. While it is established that improper management of excavated peat can cause it to lose the majority of its carbon to the atmosphere as CO2, the carbon response of peat mixed in situ is unknown and has prompted this study. Under accelerating conditions in the laboratory, emissions were recorded from columns of parent peat (high and low water tables) and cement-stabilised peat. While the parent peat was found to be a source of CO2 influenced by water levels and temperature, stabilised peat appears to act as a net carbon sink. This is an important finding for carbon calculations relevant to soil-mixing applications. The first author acknowledges the financial support (College Fellowship) provided by the College of Engineering and Informatics at NUI Galway. peer-reviewed

The advent of reliable real-time monitoring devices has changed the way we monitor the construction of geotechnical infrastructure. This paper presents a case study where Shaped Accel Arrays (SAA) were employed as part of the real-time monitoring regime for the construction of two retaining structures that utilised a combination of secant and sheet piles. To improve their structural rigidity, a capping beam and horizontal props were employed. The retaining structures were erected to facilitate the launching and retrieval of a Tunnel Boring Machine (TBM). The monitoring regime detected structural sway and toe movement of the sheet pile walls. Adjustment methods for these effects are discussed within this paper, along with a comparative study between manual and real-time monitoring. Adjusting for the effects of sway and toe movement can considerably change the maximum deflection from that registered by an SAA, therefore, it is important to account for these effects when employing SAAs to monitor the movement of a retaining structure. Furthermore, a cost comparison of using real-time monitoring in place of manual monitoring suggests that for a project of this nature where monitoring is required for more than 6 months, real-time monitoring becomes more cost effective. The authors would like to thank the following companies, AGL Consulting Geotechnical Engineers, BAM Civil/Wayss & Freytag Joint venture and Geotechnical Observations Ltd. The authors would especially like to thank, Shell E&P Ireland Limited for its financial support and technical assistance provided during this research. peer-reviewed

In addition to the traditional drivers of cost and timely programme delivery, embodied energy (EE) and embodied carbon (EC) have emerged as major considerations in all aspects (including geotechnical) of large construction projects. Foundation engineers are beginning to undertake comparisons of the EE/EC associated with various piling and ground improvement options as part of an overall appraisal of scheme feasibility. Where construction involves the modification or removal of peat, these calculations become more challenging as allowances should be made for the impact on the carbon stored within the peat and the gases potentially released from peat. Using a calculator developed at NUI Galway, research is underway to consider the EE/EC associated with piling, soil-mixing and excavate-and-replace—options that can facilitate road/motorway construction on peat. Several high-profile motorway projects in Ireland will provide data for the analysis. Also, with the help of scientists presently measuring Greenhouse Gas (GHG) emissions from peat, the research will investigate GHG emissions from peat under various management practices, restoration techniques, and mitigation against drainage methods, assessing their strength in terms of hydrology and carbon storage potential. This paper summarises a literature review carried out to identify specifically the ‘peat-related’ factors that will impact upon EE/EC calculations on construction of a road/motorway on peat. The first author would like to thank the College of Engineering and Informatics at NUI Galway for its support under the Postgraduate Research Scholarship Scheme. non-peer-reviewed

In recent years European cycling has undergone a renaissance with various initiatives including the establishment of EuroVelo and the proposed European trans-border cycling infrastructure. Significant advances on this infrastructure have been made with 45,000 km of bike paths completed. In Ireland, to encourage a modal shift among commuters to cycling, and help boost facilities for leisure cyclists and cycle tourism, the Irish Government has proposed the establishment of a 2,000 km National Cycle Network (NCN). The NCN will be modelled on international networks such as the Vias Verdes (Spain), Landelijk Fietsroutes (Netherlands) and D-Netz (Germany) and the Sustrans NCN (UK). It will comprise a range of cycle route types including: (i) on-road, (ii) cycle lanes, and (iii) greenways (traffic-free cycle trails). While a modal shift to cycling has clear potential to reduce carbon emissions in the transport sector the climate cost of constructing new cycling routes, particularly greenways, has not been previously considered. Carbon emissions during rural cycle lane construction, have the potential to negate the carbon savings made by the modal shift of many commuters. This paper, using a case study, describes a methodology for calculating the potential carbon emissions associated with cycle lane construction. It was found that the embodied carbon of on-road cycle routes and cycle lanes were generally not significant. On the other hand, the case study greenway was found to embody 60.4 tCO2e/km. The carbon savings of shifting a Passenger Kilometre Travelled (PKT) from driving a car to cycling were found, in Ireland, to average 134 gCO2e/PKT. Therefore, in the example presented, a shift of 102 commuters per year (224,400 PKT) are required to offset the carbon footprint of one 10 km asphalt greenway. The metric presented can (i) be used, at design stage to compare proposed routes in terms of their embodied carbon and (ii) be integrated in a wider design matrix to ensure the efficient and sustainable design of cycle networks internationally. This research was commissioned through the National Roads Authority (Ireland) Research Programme and is funded by the National Sustainable Transport Office at the Department of Transport, Tourism and Sport (Ireland) and the College of Engineering and Informatics at NUI Galway. peer-reviewed

The use of digital resources in higher education has risen significantly over the last ten years and will continue to do so for the foreseeable future. The challenge for educational instructors is in determining how to utilise digital resources effectively; the basis for this should not be their availability alone, but rather their ability to enhance the student learning experience and achieve desired learning outcomes. This paper describes the successful widespread integration of digital resources in the undergraduate teaching of civil engineering at the National University of Ireland, Galway. Various types of digital resources, including animations, videos, design software and case studies, are utilised. The recently completed Engineering building is itself a digital resource. Designed as a living laboratory, the building’s structure, energy systems and internal environment are heavily instrumented and the structural, environmental and energy datasets are used as teaching tools. The higher education teaching of Engineering differs significantly from that of other disciplines, such as the Arts or Humanities, in that engineering degrees are typically subject to a strict accreditation process by the national professional engineering body. In Ireland, this body (Engineers Ireland) prescribe six programme outcomes for Level 8 engineering degree programmes. The learning outcomes of individual course modules must therefore map onto one or more of these prescribed programme outcomes. The aim of this paper is to elucidate how digital resources have been used successfully by academic staff in the teaching of civil engineering subjects to help achieve professional accreditation criteria whilst also providing a more engaging student learning experience.

The motivation and implementation of a real-time structural health monitoring strategy to determine the structural performance of a number of educational buildings recently constructed in Ireland is discussed in this paper. In recent years, smart materials with embedded instrumentation has been installed in a number of buildings at the National University of Ireland Galway during the construction phase, which allows continuous monitoring of the behaviour of the structure. Instrumentation installed on a number of projects, described in this paper, allow many important aspects of structures to be monitored during construction, as well as in the operational phase of the building such as temperature, concrete and reinforcement strain, deflection, and response to the environment. The authors would also like to thank the National University of Ireland Galway and particularly the Department of Civil Engineering in the College of Engineering and Informatics for the help with the instrumentation in the demonstration buildings. They also wish to thank all the construction personnel and building professionals involved in the demonstrator buildings who facilitated and helped with installing the structural health monitoring systems. The authors would like to acknowledge the financial support of the European Commission through the Horizon 2020 project Built2Spec (637221). The second author would like to acknowledge the support of Science Foundation Ireland through the Career Development Award programme (Grant No. 13/CDA/2200). peer-reviewed

To combat the energy demand and global warming potential emissions of the building sector, the European Union has made mandatory the introduction of nearly zero energy buildings (nZEBs) in all its member states. Starting from the end of 2020, all new buildings or those receiving significant retrofit must show a very high energy performance standard with energy performance levels based on the cost-optimal framework methodology. Similarly, this is a requirement for all public buildings from the end of 2018. The population of Ireland is expected to increase by around one million people to almost 5.7 million people by 2040, requiring at least an additional half a million new homes. Additionally, 1.9 million housing units in Ireland are required to be retrofitted for the Irish national housing stock to be considered nZEB standard. Thus, work on approximately 2.5 million residential homes is required to achieve an Irish nZEB housing stock by 2040. Moreover, the role of people occupying buildings with regards to their energy usage behaviours, habits, perceptions and attitudes is central to ensuring buildings have a low environmental operational impact while maintaining healthy comfortable living conditions. This research adopted an interdisciplinary methodological design that combined engineering and social sciences to investigate the environmental, economic and social impacts of residential buildings in Ireland moving towards nZEB standards by examining the interrelationships between the operational energy demand practices in buildings, the people occupying the buildings and the materials and technology used in the construction/retrofit of the buildings. The environmental, economic and social impacts of semi-detached and terraced houses were examined considering (i) past and present building regulations, (ii) the materials and technology employed in the buildings, (iii) future electricity generation fuel mix, (iv) future energy pricing, (v) discounting operational energy costs, (vi) the space heating, domestic water heating and appliance energy demand practices of people occupying the buildings and (vi) people’s attitudes, perceptions and social norms regarding energy consumption and the environment. The research found that minimising the environmental and economic impact of the materials and technology used in the construction of new build nZEB residential buildings is becoming equally, if not more, important than the environmental and economic impact from people’s operation of residential buildings. Assuming 10% of the 0.5 million required new residential units are semi-detached buildings complying with passive house thermal fabric and ventilation standards to achieve nZEB energy performance standards, they will potentially save an estimated 116.3 TJ/m2, 0.8 kilotons CO2eq/m2 and €2.6 million/m2 over 60 years compared to 2011 Irish building energy performance standards. For semi-detached gas heated houses constructed between 1991 and 2002 in Ireland and retrofitted to new build nZEB energy performance standards, the operation of the building has a greater life cycle energy and life cycle GWP impact compared to the materials and technology invested from the retrofit. Despite issues with both approaches, reducing the energy consumption of households was found to be more effective by investing in materials and technology rather than attempting to get householders to change their energy demand practices. For a monitored social housing estate in Ireland which underwent an energy efficiency retrofit, the average gas and electricity energy cost savings the year following the energy efficiency retrofit were €141 and €140, respectively, despite energy savings not meeting their theoretical potential. The householders were found to play a key role in the success (or lack thereof) of the retrofitting efforts to reduce the energy consumption of the residential buildings. All in all, retrofitting Irish semi-detached gas heated houses constructed between 1991 and 2002 with the aid of government grants to new build A2 nZEB energy performance standards has the potential to achieve savings for householders ranging from €254,000/m2 to €331,000/m2, 3006 tCO2/m2 to 3554 tCO2/m2 and 46,135 GJ/m2 to 50,196 GJ/m2 over 30 years. However, for these type of environmental and economic savings for new build and existing buildings in Ireland to be realised, significant investment is needed in energy demand research in the Irish built environment to be able to fully understand how the interrelationships between building materials and technology, people occupying the buildings and operational energy demand practices in buildings drive building energy consumption and energy savings.

Cryogenic storage tanks, also known ’cryotanks’, are an important component of space launch vehicles. Cryotanks can form an integral part of the overall structure of the launch vehicle and also represent a significant proportion of the overall weight. Because of the high value of structural weight reduction in launch vehicles, many major space launcher manufacturers are researching moving from metal cryotanks to linerless composite cryotanks; that is, moving towards composite cryotanks without metallic liners. The work presented in this thesis investigates the suitability of Carbon Fibre (CF) PolyEtherEtherKeytone (PEEK) in the manufacture of linerless composite cryotanks due to its favourable specific strength, toughness, manufacturability and chemical resistance. Numerous challenges to the production of linerless composite cryotanks have been identified in the literature, including permeability, large scale manufacturing, joining, damage detection and damage tolerance. This thesis specifically focuses on the issues of permeability, joining by induction welding and thermal stress in CF-PEEK. The effects of cryogenic cycling, manufacturing method, PEEK matrix type, fibre type, cryogenic temperatures, pressure, and thickness on the permeability of CF-PEEK laminates are investigated. Mechanical testing is carried out on a hat stiffened, CF-PEEK, induction welded panel to evaluate the performance of the welded assembly and results are compared with similar testing of an adhesively bonded panel. An experimental and computational investigation into the heating of CF-PEEK is also carried out to identify the parameters that influence induction heating of CF-PEEK. Due to its importance in damage tolerance at cryogenic temperatures and permeability, an experimental investigation into thermal stress in CF-PEEK has also been carried out. The work investigates methods of reducing thermal stress given in the literature and whether a reduction in thermal stress results in reduced damage at cryogenic temperatures. The results of the permeability study provide a novel insight into the permeability and leak rate of CF-PEEK and show that the leak rate of CF-PEEK make it a suitable candidate material for use in linerless composite cryotanks. The work on induction welding addresses the lack of data relating to demonstrator scale welded assemblies in the literature, demonstrates that continuous induction welding is a suitable assembly technique for primary structures and identifies process-induced artefacts that may occur during induction welding. The work on induction heating provides a novel insight into the heating behaviour of CF-PEEK and demonstrates that finite element modelling is a valuable tool in process development of induction welding. The results of the thermal stress investigation verify that a reduction in thermal stress is possible by subjecting CF-PEEK to thermal post-processes and demonstrate, for the first time, that a reduction in thermal stress leads to a reduction in damage initiation at cryogenic temperatures. The work presented in this thesis provides valuable information relating to permeability, induction welding and thermal stress of CF-PEEK materials, which will inform the future development of CF-PEEK linerless composite cryotanks. The impact of the use of CF-PEEK in linerless composite cryotanks would be to reduce the weight and ultimately the environmental and economic cost of space travel, enabling future space exploitation and exploration.

One of the emerging technologies in construction is the development of ‘smart structures’ which have sensors which will allow more efficient, resilient and sustainable structures to be designed and constructed. This research focusses on the use of embedded sensors and testing to better understand the behaviour of hybrid concrete lattice girder flat slabs, which is classified as a Modern Method of Construction (MMC). Despite the popularity of concrete flat slabs in structures and the increasing adoption of hybrid concrete lattice girder slabs to construct flat slabs, there is a dearth of information on how they perform during construction and in use. A programme of insitu field monitoring and laboratory testing was conducted to investigate the actual behaviour of hybrid concrete lattice girder flat slabs. In the literature, there are very few case studies in relation to monitoring of concrete floors using field data. The methodology and implementation of a real-time structural health monitoring strategy for hybrid concrete lattice girder flat slabs are described. Vibrating-wire strain gauges and electrical resistance strain gauges were embedded in both the precast plank and insitu concrete topping of the floor system, which were used to monitor various aspects of the behaviour of the floor during the manufacturing, construction and operational phases. Environmental conditions were also monitored so that a holistic analysis of the factors which influence the behaviour of the concrete floor could be undertaken. The rich field data from the monitoring was used to examine early-age behaviour of the hybrid concrete slab. Predicted values for peak temperature and temperature differentials in the concrete were found to be conservative and greater than values measured in the field. The field data was also used to determine restraint factors in the insitu topping at various locations in the hybrid concrete slab and it was found that the restraint factor varied between 0.16 to 0.37 (zero indicating no restraint and unity being fully restrained). There was good correlation between predicted flexural behaviour of the hybrid concrete slab using the finite element models and the actual behaviour measured in the field. The actual degree of rotational restraint provided by supporting walls to the slab was noticeably different to that assumed and this confirms the rationale in some design codes for additional torsional reinforcement to be provided at slab edges. In addition, the load transfer mechanism through the hybrid concrete floor during the construction of a multi-storey concrete frame construction in which concrete floors are temporarily supported by floors below is analysed. It indicates that the slab behaves linearly elastic and is uncracked during the construction phase. In addition, a one-dimensional finite difference model was developed which took account of heat of hydration, heat transfer mechanisms and environmental conditions and was compared with measured concrete temperatures in the hybrid slab. Accurate predictions of thermal behaviour of concrete slabs is critical for the development of passive design strategies in buildings and the utilisation of the thermal mass properties of concrete floors. The 1-D model was shown to have good correlation with the measured concrete temperatures. The significant influence of ambient temperature and solar radiation on the thermal behaviour of the hybrid concrete floor are analysed during the construction phase using the field data. To investigate the interaction between the various components of the lattice girder plank (i.e. top chord, bottom chord and diagonals of the lattice girder; concrete; reinforcement) during the construction stage in more detail under controlled conditions, a series of experimental laboratory tests were conducted. The testing is a significant addition to the literature on experimental testing of lattice girder precast planks during construction as it analyses all the components of the precast floor. The dominant design parameters for controlling stiffness and the deflection of the plank during construction stage are the diameter of the top chord of the lattice girder and the spacing of the lattice girders. The experimental data was used to produce design tables for erection spans which take account of the multi-span nature of lattice girder planks when temporarily propped. The experimental results reported conclude that there is potential improvement of the arrangement of temporary propping possible for lattice girder planks during construction that could reduce costs, labour and congestion on site, which will improve the construction process for flat slabs.

The emerging trends for deep-retrofit of existing buildings in Europe require formulation of strategies for nearly zero-energy buildings (nZEBs) and achieving benchmarks as outlined in the Energy Performance of Buildings Directive (EPBD) recast. The fundamental process of retrofitting to an explicit high performance (both energy and comfort) necessitates the development of robust and diverse methodologies to be used during the early-stages of planning in retrofit projects. The construction sector lacks the extensive use of such methods for early decision-making that are essential to accelerate building renovation in Europe. Therefore, considering the need to upgrade existing buildings to nZEB, the thesis aims at developing decision-making support for deep-retrofits. This research presents the application of combined (i) research techniques, (ii) audit and assessment methods, (iii) building simulation, and (iv) optimisation strategies investigated on an existing building field-study that shall support the decision-making in retrofitting existing buildings to low-energy and comfortable buildings. The overall research methodology incorporated a preliminary scoping study, including literature review and stakeholder analysis, followed by a detailed field-study, building simulation and optimisation for deep-retrofit analysis and solutions. The scoping study was designed to assess the gaps in theory through literature review and practice using surveys, a workshop and focused interviews investigating experience, knowledge, expectation, and needs of retrofit industry stakeholders in Ireland. The results of this scoping study informed the overall methodology for research in this thesis. A systematic field-study was conducted on a partially-retrofitted university building (built during 1970s) in Ireland. The different building performance metrics for energy and comfort were examined for the existing building and their optimisation opportunities were identified. Furthermore, an indoor environmental quality (IEQ) assessment was carried out using standards-based procedures and practices along with detailed energy audits and occupant surveys. The metrics of thermal, visual and acoustic comfort, together with indoor air quality (IAQ), were analysed for occupant satisfaction. This formed the basis for further investigation focusing on achieving nearly zero-energy performance with improved IEQ and led to the identification of proposed retrofit measures. The further investigation involved the development of a whole-building energy simulation models using the field-study data. A novel multi-stage automated-calibration methodology was developed to calibrate the simulation model using genetic algorithm (GA). The methodology combined a rigorous uncertainty analysis of simulation input parameters using the Morris method. The model was calibrated and validated with the energy and environmental reference datasets from the field-study meeting the acceptance criteria outlined in the standards. Furthermore, the impact of several proposed retrofit measures on energy, comfort, and cost were evaluated using the calibrated model, through multi-objective optimisation (MOO) (Pareto fronts), to explore deep-retrofit solution packages. The main objectives of the MOO were primary energy consumption (PEC), discomfort hours (DH) and net present value (NPV) of life cycle-costs (LCC). An additional analysis of IAQ was also conducted, which provided added benefits that were also taken into consideration in the proposed deep-retrofit solution packages. To validate the effectiveness of these solutions, single-step and staged-retrofit approaches were examined for their feasibility in achieving cost-optimal nZEB performance. The overall work concludes with different retrofit approaches for critical assessment tied to the main research methodology that supports the decision-making for non-domestic retrofits from the energy, cost and IEQ perspective. Multi-objective optimisation ensured robust model calibration and analysis of most optimal solutions for the decision making of deep-retrofit packages based on selected objectives. Findings of this research may (i) benefit the non-domestic deep-retrofit projects (and their stakeholders) to develop a systematic approach and processes to achieve nZEBs, (ii) provide evidence that deep-retrofit of non-domestic buildings can significantly reduce their energy consumption, (iii) strengthen and align the focus of retrofit industry on improving IEQ together with energy efficiency, (iii) inform the local legislation into setting up the nZEB benchmarks for existing buildings performance and, (iv) add to the primary case study database on non-domestic buildings outlining the deep-retrofit impact. 2020-04-05

The behaviours of braced steel frame members and components are investigated in this project using finite element models that were developed to address the multi-scale mechanics of braced steel frame structures. The multi-scale mechanics are based on three assessment scale levels; that is, material (coupons), elemental (bracing steel structural members) and component (brace gusset-plate structural members) levels. Each finite element model was validated with data from physical laboratory tests. The models were then used to assess the current European code of practice in the seismic design of braced steel frames, as well as existing empirical models and numerical models, and to derive new relationships for a number of design parameters. The framework developed for finite element modelling of steel concentrically braced frame structures followed conventional guidelines for 3D non-linear modelling but included novel advanced modelling techniques such as the extended finite element method-based crack growth model development, automated generation of initial imperfections in the brace member and an innovative material modelling methodology application. Importantly, realistic detailing for gusset plates and brace members were employed in the study. The framework of modelling was developed in the commercial finite element package ABAQUS v.6.13. The performance of finite element models was assessed against various measured parameters obtained from physical laboratory tests, such as buckling compressive loads, initial yield load, tensile load, ductility capacity, energy dissipative capacity, cycles to initiation of global and local buckling, fatigue-life capacity and failure modes. It was found that the finite element models predicted these response features within engineering accuracy, for multi-scale mechanical behaviour of braced steel frame members and components, when subjected to both static monotonic and cyclic ultra-low cycle fatigue loading regimes. Thus, the finite element models proposed in this study can be used with confidence both in academic studies and by engineering professionals for analyse and design of safer and robust structures, as they were calibrated and validated using physical test data.

Ocean wave energy harvesting research and development has grown in recent years and wave energy conversion to electricity using wave energy converters (WECs) on a commercial scale is also becoming more realistic. This research is concerned with characterising wave energy resources, investigating resource scalability and assessing the impacts of wave farms. The research presents a detailed wave resource assessment methodology, development of a suite of nested local scale wave models using Simulating Waves Nearshore (SWAN) wave model, determination of scaling approaches for upscaling from benign test sites to full scale deployment sites and analysis of the effects of WEC arrays on the nearshore wave climate. A detailed methodology for wave resource assessment has been developed for identifying operational, high and extreme wave conditions. The methodology was applied at three wave energy sites on the West coast of Ireland – (i) the 1/4-scale Galway Bay Test Site (GBTS), (ii) the full-scale Atlantic Marine Energy Test Site (AMETS) and (iii) the Westwave site. Two validated nested local wave models were developed and simulated for 12-years (2004-2015) to conduct wave resource assessment. The 12-year annual mean power calculated for the sites were 68 kW/m and 57 kW/m at Berth A at Berth B, respectively, at AMETS, 3kW/m at GBTS and 50kW/m at Westwave. Three scaling approaches were analysed to identify the appropriate scale ratios to be used to upscale wave conditions at GBTS to AMETS. The distribution fittings method was found to be the most accurate method to upscale GBTS to AMETS and Westwave. The scaling result shows GBTS is not 1/4-scale proportionate to AMETS or Westwave as previously assumed. Finally, an analysis of WEC array impacts on the nearshore wave climate involved the determination of an appropriate transmission coefficient (Ct) from a computational fluid dynamic (CFD) and WEC arrays implementation using SWAN. The Ct value from the CFD model was used in SWAN to represent WEC arrays. WEC array performance and device layouts and spacing was investigated and three WEC arrays scenarios have been examined to assess their impact on the wave climate at the nearshore area of the Westwave site.

In addition to the traditional drivers of cost and timely delivery, embodied energy (EE) and embodied carbon (EC) have emerged as major considerations in all aspects of large construction projects. This is due to stricter environmental regulations introduced in Ireland and the European Union, which have resulted in geotechnical engineers beginning to compare the EC/EE associated with various piling and ground improvement options as part of an overall appraisal of scheme feasibility for road construction projects. Where construction involves the modification or removal of peat, these calculations become more challenging as allowances should be made for the impact on the carbon stored within the peat and the gases potentially released. To incorporate these allowances in the EE and EC summations in a life cycle assessment (LCA) for a construction project requires the inclusion of peat-related factors such as peat drainage, drainage systems, slope stability, restoration and clearance of vegetation/forest. As there is a dearth of methodologies to quantify EC and EE of ground improvement techniques for road construction on peat, new LCA methodologies need to be developed to more accurately quantify emissions and energy consumed in order to produce more sustainable solutions. Traditionally, excavate-and-replace is the most commonly used method in Ireland, but other techniques such as piling and dry soil-mixing can also be considered. In projects employing an excavate-and-replace solution, peat is often removed to disposal areas and the subsequent drying causes a significant release of CO2 into the atmosphere. To date, however, in dry soil-mixing the impact of stabilising peat on on-site CO2 emissions has not been considered and is, therefore, the primary focus of this thesis. A preliminary study of nine columns containing peat and peat mixed with cement was set up in a temperature control room to investigate CO2 emission rates. Gas samples were collected using the closed chamber method and analysed using a gas chromatograph. The result of the experiment showed that the stabilised peat absorbed CO2 both from the air and CO2 released by the oxidised peat due to the carbonation process. Subsequent to this substantial finding, two extensive column studies were undertaken to examine the carbonation potential of stabilised peat whose binders consisted of cement and cement and ground granulated blast slag (GGBS) combinations. As in the first experiment, the CO2 intake rate decreased with time as the depth of the carbonation front grew. Variables which significantly influenced the CO2 intake rate included time, initial CO2 concentration, cement content, GGBS content, water table and surcharge. Besides calculating CO2 intake rates, the depth of the carbonation front was analysed to produce k-rate factors, representing the rate at which the carbonation front increases. As this was the first time the carbonation front in stabilised peat was examined, several techniques were used to establish the most suitable procedure to explore this carbonation front: phenolphthalein indicator, pH of stabilised peat slurries, X-ray powder diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), loss on ignition method (LOI), and water evaporation method. From the results, the carbonation front obtained by XRD was similar to those from LOI and FTIR. In contrast, the phenolphthalein method underestimated the carbonation front, while the pH of stabilised peat slurries technique showed a carbonation front greater than the other methods. The laboratory results provided crucial information on the environmental impact of dry soil-mixing and its on-site impact. Using these results and a novel LCA methodology, an LCA to examine EE and EC was performed on a case study of a section of motorway built on peat. To ascertain the optimum solution for EE and EC, several ground improvement scenarios were studied, including excavate-and-replace, dry soil-mixing and a combination of excavate-and-replace and piling. From laboratory results, it was taken for the dry soil-mixing scenario that emissions from the stabilised peat were zero for the lifetime of the road. The LCA also investigated emissions from peat under various management practices and restoration techniques, assessing their strength in terms of hydrology and carbon storage potential. The results showed that dry soil-mixing had a minimal on-site impact and that the EC of the binder could be lowered markedly if the binder type was changed. On the other hand, even though the EC and EE of materials used in the excavate-and-replace solution were low, the on-site impact was immense due to extensive peat disturbance. In the case study which forms part of the subject of this research, a combination of excavate-and-replace and piling was found to be most favourable solution, but the preferred ground improvement technique in general was found to change according to the project and site location. In this research, novel laboratory studies were undertaken and a new LCA methodology was developed. Various techniques to understand the carbonation process in stabilised peat were utilised, with advantages and disadvantages found for all of them. The body of work has international implications as it points to dry soil-mixing having a lower environmental impact than previously thought. Additionally, it provides a platform for further studies in this area. From this research, the environmental impact of building on peat can be quantified more accurately and the understanding of stabilised peat enhanced in terms of emissions and carbonation depth and potential. 2017-03-02

There is substantial opportunity in the development of wind and tidal current turbines to help decarbonise national energy systems and to expand the economic potential of the European Union. However, well-documented cases of renewable energy device failures have highlighted the issue of reliability and the importance of durability in the structural design of blades. Furthermore, electricity generated by tidal devices is currently over twice the price of electricity generated by offshore wind turbines, due to the infancy of the technology, remote installation locations and short maintenance windows for these devices. A significant component of the total costs for both types of turbine is the high cost of rotor blade manufacturing (up to 15% of the turbine capital expenditure). Additionally, the long-term loading on tidal turbines is yet to be fully characterised, with the effects of fatigue damage an area of particular concern. There is a need to ensure the effective functioning of every component of the turbine and to minimise the associated costs. This thesis presents the application of numerical techniques and design optimisation strategies for wind and tidal turbine blades. The design studies contained in the thesis advance upon previous studies in this field by combining blade element momentum theory, damage and fatigue analysis methods and genetic algorithm design optimisation routines for composite turbine blades. The contributions made to the state of the art are relevant from both a scientific and an industrial perspective. At the core of this research is the development of an automated computational design and analysis methodology for wind and tidal turbine blades. The first iteration of the methodology included novel aspects such as: non-linear damage modelling of composite materials under static loading conditions, hydrodynamic modelling using blade element momentum theory (BEMT) and finite element (FE) sub-modelling techniques. The concept design of the blade for a 1 MW tidal turbine was performed, investigating the application of glass and carbon fibre-reinforced materials and the subsequent effects on blade stiffness and composite damage. The analytical capacity of the computational methodology for full-scale composite structures was confirmed against physical testing of a 13 m long glass fibre-epoxy wind turbine blade. Once the FE representation of the blade was validated, the methodology was combined with a genetic algorithm (GA) to optimise the mass of the blade. The automated nature of the methodology enabled the efficient variation of model parameters and a set of near-optimum blade designs were evaluated. The methodology was further developed to incorporate a multi-objective GA and an optimisation study was performed on 4.5 m long glass fibre-reinforced polypropylene blades. Experimental tests were carried out to characterise the blades and to calibrate the FE blade models. The optimisation approach was validated by testing a custom-made glass fibre blade and comparing the results to numerical models. Finally, the fatigue performance of a concept tidal turbine blade was examined. The BEMT model was enhanced and validated against published experimental results and applied to actual tidal current data to determine the fatigue loading on the blades. A post-processing code for assessing the damage to the composite material was also developed, based on constant life diagrams for representative glass fibre-reinforced materials, Miner’s rule and Rainflow counting. The fatigue design study incorporated the aspects of structural modelling and hydrodynamic modelling, together with the optimisation techniques developed throughout the thesis, to successfully design and analyse a full-scale composite blade. The automated computational design methodology allowed a variety of blade designs to be assessed before testing. Coupled with the optimisation approaches, the methodology showed significant mass reductions for wind and tidal turbine blade designs, while retaining the strength and stiffness of the composite structures. Mass savings result in lower material and labour costs, thereby reducing the levelised cost of energy for the devices. Ultimately, the developed methodology will lead to reduced manufacturing and design costs for rotor blade manufacturers and facilitate the development of more efficient and robust wind and tidal turbine devices.