dimitra-achillopoulou

Dr Dimitra Achillopoulou


Marie Curie Research Fellow
+44 (0)1483 686614
23 AA 02

Academic and research departments

Faculty of Engineering and Physical Sciences.

My publications

Publications

Superstructures such as reinforced concrete bridges, often suffer from exposure to extreme corrosive environments. The corrosion of the reinforcement leads to a decrease of their capacity and their structural performance needs to be upgraded with strengthening measures. Lately, the use of Fiber Reinforced Polymers (FRP) in retrofitting schemes has attracted a lot of attention. In this paper the interface response of adhesively bonded Carbon FRP (CFRP) fabrics applied on concrete substrates is investigated. This paper deals with the study of the integration of CFRP fabrics using different adhesive layers as the composite's matrix, first using a conventional adhesive and next using an enhanced toughened adhesive layer. Two different scenarios of substrate integrity were studied: a) healthy concrete and b) substrate with corrosion products. The bond-slip behavior of the interfaces between concrete and the laminated fabrics was investigated with a modified double shear test configuration. The use of the toughened matrix increases the shear stresses up to 61% in failure, nonetheless in significant lower ratio of strains. The corrosion reduces the maximum shear stresses of the interface up to 20% and the corresponding strains up to 23% in failure. For the scenario were the toughened matrix was used, there is a shift in the response from a pseudo-ductile to linear with a tendency to fully elastic. The crack propagation is depicted in distinct stages. The use of toughened adhesive layers with reduced stiffness shifts the mindset of creating high stiffness retrofitting solutions to achieve high mechanical performance and still ensures an efficient strengthening response.

Dimitra V. Achillopoulou, Stergios A. Mitoulis, Sotirios A. Argyroudis, Ying Wang (2020)Monitoring of transport infrastructure exposed to multiple hazards: a roadmap for building resilience, In: Science of The Total Environment746141001 Elsevier

Monitoring-enhanced resilience in transport management is emerging together with the new technologies and digital data, however have not been fully explored yet. Digital technologies have the potential to provide rapid resilience assessments in a quantifiable and engineered manner for transport infrastructure, which is exposed to multiple natural and human-induced hazards and diverse loads throughout their life-cycle. Physical damage and disruption of networks and interdependent systems may cause tremendous socioeconomic impact, affecting world economies and societies. Nowadays, transport infrastructure stakeholders have shifted the requirements in risk and resilience assessment. The expectation is that risk is estimated efficiently, almost in real-time with high accuracy, aiming at maximising the functionality and minimising losses. Nevertheless, no integrated framework exists for quantifying resilience to diverse hazards, based on structural and functionality monitoring (SHFM) data, and this is the main capability gap that this paper envisages filling. Monitoring systems have been used widely in transport infrastructure and have been studied extensively in the literature. Data can facilitate prognosis of the asset condition and the functionality of the network, informing computer-based asset and traffic models, which can assist in defining actionable performance indicators, for diagnosis and for defining risk and loss expediently and accurately. Evidence exists that SHFM is an enabler of resilience. However, strategies are absent in support of monitoring-based resilience assessment in transport infrastructure management. In response to the above challenge, this paper puts forward for the first time in the international literature, a roadmap for monitoring-based quantification of resilience for transport infrastructure, based on a comprehensive review of the current state-of-the-art. It is a holistic asset management roadmap, which identifies the interactions among the design, monitoring, risk assessment and quantification of resilience to multiple hazards. Monitoring is embraced as a vital component, providing expedient feedback for recovery measures, accelerating decision-making for adaptation of changing ecosystems and built environments, utilising emerging technologies, to continuously deliver safer and resilient transport infrastructure.

S.A. Argyroudis, D.V. Achillopoulou, V. Livina, S.A. Mitoulis (2021)Data-driven resilience assessment for transport infrastructure exposed to multiple hazards by integrating multiscale terrestrial and airborne monitoring systems, In: Proceedings of IABMAS 2020: 10th International conference on Bridge Maintenance, Safety and Management International Association for Bridge Maintenance and Safety

The exposure of critical transport infrastructure to natural hazards and climate change effects has severe consequences on world economies and societies and, thus, safety and resiliency of transport networks are of paramount importance. The currently available frameworks for quantitative risk and resiliencebased design and assessment have been mainly developed for bridges exposed to earthquakes. However, there is an absence of well-informed exposure, vulnerability, functionality and recovery models, which are the main components in the quantification of resilience. The present paper proposes an integrated framework for the data- driven resilience assessment of transport infrastructure exposed to multiple hazards by using multiscale monitoring data, such as terrestrial and airborne data, as well as open-access crowd data and environmental measurements. Monitoring and early warnings are expected to produce accurate and rapidly informed quantitative risk and resilience assessments for transport infrastructure and to enhance asset management. Therefore, this framework aims to facilitate stakeholders’ decision-making for daily and catastrophic events and to support adaptation and preparedness with preventive and/or retrofitting measures against multiple hazards.

D V Achillopoulou, S A Mitoulis, N K Stamataki (2021)Resilient Monitoring of the Structural Performance of Reinforced Concrete Bridges using Guided Waves, In: Proceedings of IABMAS 2020: 10th International conference on Bridge Maintenance, Safety and Management International Association for Bridge Maintenance and Safety

Structural Health Monitoring of the deflections of a reinforced concrete bridge deck strengthened with Fibre Reinforced Polymers (FRP) or composite materials can help towards obtaining predictions of fail-ures. Data regarding spam deflection, FRP debondings or failures and concrete crack patterns, acquired by guided waves on interfaces of concrete substrate and FRP measures are used in order to represent the damage propagation of the strengthened bridge deck over time. The failure indexes of the interfaces help towards a strategy for maintenance and asset management based on potential risk that derives from structural data. This resilient strategic monitoring of interfaces is a practical, expedient, long-distant tool to estimate the efficiency of the interfaces (Interface Efficiency Indices-InterFeis) and the risk level of the asset with no disruption of traffic or in nonapproachable areas. The monitoring of the time history of data concerning the structural integ-rity, assesses the structural performance of the bridge against critical loads, combined phenomena, extreme events, climate change or other uncertainties of design or of its life-cycle and can be integrated in bridge design guidelines towards infrastructural safety and resilience of the transportation network, saving valuable time and resources.

Annamaria Pau, Dimitra V Achillopoulou (2017)Interaction of Shear and Rayleigh-Lamb Waves with Notches and Voids in Plate Waveguides, In: Materials10(7)

This paper investigates the interaction of different shear- and Rayleigh-Lamb-guided waves in plates with a discontinuity such as a notch or an internal void. The problem was solved numerically using a finite element model and by exploiting an analytical solution obtainable for the double sharp changes of the cross-section that served as a reference. We aimed to elucidate the relation between the size and shape of the discontinuity and the reflection and transmission coefficients of the scattered field. Different sizes and profiles of the discontinuity were considered, with the shapes ranging from step changes of the height to ellipses, both symmetric and nonsymmetric. Regimes related to low and high values of the product frequency multiplied by the height of the plate were investigated. These showed how the mode conversion was related to the symmetry between the incident mode and the discontinuity, and to the actual existence of multiple propagating modes. The analysis presented was motivated by the need to set up procedures that exploit propagating waves not only to detect the presence of a notch, but also to characterize its size and shape.

DIMITRA ACHILLOPOULOU, STERGIOS MITOULIS, Nikoleta Stamataki (2021)Resilient Monitoring of the Structural Performance of Reinforced Concrete Bridges using Guided Waves

Structural Health Monitoring of the deflections of a reinforced concrete bridge deck strengthened with Fibre Reinforced Polymers (FRP) or composite materials can help towards obtaining predictions of failures. Data regarding spam deflection, FRP debondings or failures and concrete crack patterns, acquired by guided waves on interfaces of concrete substrate and FRP measures are used in order to represent the damage propagation of the strengthened bridge deck over time. The failure indexes of the interfaces help towards a strategy for maintenance and asset management based on potential risk that derives from structural data. This resilient stra-tegic monitoring of interfaces is a practical, expedient, long-distant tool to estimate the efficiency of the inter-faces (Interface Efficiency Indices-InterFeis) and the risk level of the asset with no disruption of traffic or in nonapproachable areas. The monitoring of the time history of data concerning the structural integrity, assesses the structural performance of the bridge against critical loads, combined phenomena, extreme events, climate change or other uncertainties of design or of its life-cycle and can be integrated in bridge design guidelines towards infrastructural safety and resilience of the transportation network, saving valuable time and resources.

Dimitra V Achillopoulou, Alexandra N Kiziridou, Georgios A Papachatzakis, Athanasios I Karabinis (2016)Investigation of interface response of reinforced concrete columns retrofitted with composites, In: Steel & composite structures22(6)pp. 1337-1358 Techno Press

The current study focuses on the assessment and interface response of reinforced concrete elements with composite materials (carbon fiber reinforced polymers-CFRPs, glass fiber reinforced polymers-GFRPs, textile reinforced mortars-TRM\'s, near surface mounted bars-NSMs). A description of the transfer mechanisms from concrete elements to the strengthening materials is conducted through analytical models based on failure modes: plate end interfacial debonding and intermediate flexural crack induced interfacial debonding. A database of 55 in total reinforced concrete columns (scale 1:1) is assembled containing elements rehabilitated with various techniques (29 wrapped with CFRP\'s, 5 wrapped with GFRP\'s, 4 containing NSM and 4 strengthened with TRM). The failure modes are discussed together with the performance level of each technique as well as the efficiency level in terms of ductility and bearing/ bending capacity. The analytical models\' results are in acceptable agreement with the experimental data and can predict the failure modes. Despite the heterogeneity of the elements contained in the aforementioned database the results are of high interest and point out the need to incorporate the analytical expressions in design codes in order to predict the failure mechanisms and the limit states of bearing capacities of each technique.

Dimitra V. Achillopoulou (2017)Investigation of load transfer along interfaces of jacketed square columns, In: Structural engineering and mechanics63(3)pp. 293-302 Techno Press

This study deals with a numerical investigation of load transfer along interfaces of jacketed columns using finite element models. Appropriate plasticity and constitutive models are used to simulate the response of concrete and steel bars. Experimental data were used to calibrate the simulation of mechanical characteristics. The different compressive strength of core and jacket concrete, the confinement ratio, the dowels’ diameter size and the load pattern shapes were considered. The path diagrams along the interfaces elucidate the areas around the dowel bars where due to stress concentration plastic hinges and intense discontinuities are created. The stress flow also depicts the contribution of confinement of the jacketed area to the overall resonant load capacity of the core column. The scope of the research is to identify and quantify the shear transfer along the interfaces of strengthened elements. KCI Citation Count: 0

S.A. Argyroudis, D.V. Achillopoulou, V. Livina, S.A. Mitoulis (2021)Data-driven resilience assessment for transport nfrastructure exposed to multiple hazards, In: Proceedings of the 10th International Conference on Bridge Maintenance, Safety and Management (IABMAS2020) Taylor & Francis (CRC Press)

The exposure of critical transport infrastructure to natural hazards and climate change effects has severe consequences on world economies and societies and, thus, safety and resiliency of transport networks are of paramount importance. The currently available frameworks for quantitative risk and resiliencebased design and assessment have been mainly developed for bridges exposed to earthquakes. However, there is an absence of well-informed exposure, vulnerability, functionality and recovery models, which are the main components in the quantification of resilience. The present paper proposes an integrated framework for the data- driven resilience assessment of transport infrastructure exposed to multiple hazards by using multiscale monitoring data, such as terrestrial and airborne data, as well as open-access crowd data and environmental measurements. Monitoring and early warnings are expected to produce accurate and rapidly informed quantitative risk and resilience assessments for transport infrastructure and to enhance asset management. Therefore, this framework aims to facilitate stakeholders’ decision-making for daily and catastrophic events and to support adaptation and preparedness with preventive and/or retrofitting measures against multiple hazards.