Bridge-specific fragility analysis: when is it really necessary?

In seismic assessment of bridges the research focus has recently shifted on the derivation of bridge-specific fragility curves that account for the effect of different geometry, structural system, component and soil properties, on the seismic behaviour. In this context, a new, component-based methodology for the derivation of bridge-specific fragility curves has been recently proposed by the authors, with a view to overcoming the inherent difficulties in assessing all bridges of a road network and the drawbacks of existing methodologies, which use the same group of fragility curves for bridges within the same typological class. The main objective of this paper is to critically assess the necessity of bridge-specific fragility analysis, starting from the effect of structure-specific parameters on component capacity (limit state thresholds), seismic demand, and fragility curves. The aforementioned methodology is used to derive fragility curves for all bridges within an actual road network, with a view to investigating the consistency of adopting generic fragility curves for bridges that fall within the same class and quantifying the degree of over- or under-estimation of the probability of damage when generic bridge classes are considered. Moreover, fragility curves for all representative bridges of the analysed concrete bridge classes are presented to illustrate the differentiation in bridge fragility for varying structural systems, bridge geometry, total bridge length and maximum pier height. Based on the above, the relevance of bridge-specific fragility analysis is assessed, and pertinent conclusions are drawn

Evaluation of the Behaviour of Lime and Cement Based Mortars Exposed at Elevated Temperatures

Exposure to fire and elevated temperatures is diachronically a significant decay factor, influencing the stability of structures. Cement and lime-based mortars have a different behavior when exposed at elevated temperatures, usually testified by the post-fire preservation state of historic and contemporary constructions. In this paper, the correlation of their properties is envisaged, in order to identify the key elements of their performance. To this direction, five compositions of cement and lime based mortars were manufactured and tested, after their exposure at 200oC, 400oC, 600oC, 800oC and 1000oC. The binders used concerned CEM I42.5Ν (C), hydrated lime (L) and natural pozzolan (P), while the systems applied regarded C, C:L (1:1), L, L:P (1:1) and L:P:C (1:0.8:0.2) (parts per weight). The aggregates used were natural of siliceous origin and their gradation varied from 0-4mm to 0-8mm. The B/A ratio was 1/2 by weight and the W/B ratio was adjusted in order to maintain workability around 15±1cm. The physico-mechanical properties of the specimens, were recorded before and after their exposure at the selected temperatures. From the evaluation of the results, it was concluded that the mortars’ behavior was different at the early temperature rate (up to 600oC) according to their type, whereas the results were more comparable at the extreme temperature level. Generally it was observed that although the initial strength of the lime-based mortars was low (1-4MPa), they presented a more stable and efficient performance at the elevated temperatures, rendering them probably more resistant at the first stages of fire actions. Cement- based mortars seemed to present a better performance at the highest temperatures of 800oC and 1000oC

Seismic Risk of Inter-urban Transportation Networks

AbstractThe paper presents a holistic approach for assessing and managing the seismic risk and potential loss in inter-urban highway networks in earthquake-prone areas. The vulnerability of all elements of the intercity transportation system (i.e., roads, bridges, abutments, retaining walls, and tunnels) is assessed considering the interdependency among the structural, transportational and geotechnical components of the network under different seismic scenarios. Both the direct earthquake-induced damage, as well as the indirect socio-economic loss attributed to reduced network functionality are taken into account in an explicit and transparent formulation that is then displayed in space through an ad-hoc developed GIS-based software. The methodology and the decision-making tools developed are adequately modular, for them to be utilized after appropriate adaptation by local authorities in identifying, prior to a major earthquake event, those vulnerable components of their network whose failure may have a disproportional socio-economic impact. In this way, a rational and effective emergency plan can be deployed to minimize potential human, social and financial loss after a future earthquake. The outline of a foreseen application is also presented for the case of the road network of the Region of Western Macedonia in Greece. Through this pilot application, the methodology is to be optimized in real conditions before being cast in the form of a fully parameterised seismic risk tool, to be used in other earthquake prone areas as well

ΠΡΟΣΟΜΟΙΩΣΗ ΚΑΤΑΚΟΡΥΦΩΝ ΑΝΩΣΤΙΚΩΝ ΦΛΕΒΩΝ ΑΠΟ ΓΡΑΜΜΙΚΟ ΔΙΑΧΥΤΗ

Στην παρούσα εργασία γίνεται αριθμητική προσομοίωση των μέσων ιδιοτήτων κατακορύφων τυρβωδών ανωστικών φλεβών από γραμμικό διαχύτη με ένα, δύο, τρία ή πέντε ακροφύσια από τα οποία εκβάλλει πόσιμο ύδωρ σε υδάτινο ήρεμο περιβάλλον αλμυρού ύδατος. Οι αριθμητικές προσομοιώσεις πραγματοποιήθηκαν με το λογισμικό ANSYS FLUENT CFD (version R.3). Τα αποτελέσματα που προκύπτουν από την προσομοίωση συγκρίνονται με αντίστοιχα της ολοκληρωματικής μεθόδου για κυκλικές τυρβώδεις ανωστικές φλέβες και παρουσιάζουν αρκετά καλή συμφωνία. Η μοντελοποίηση έγινε σε τρεις διαστάσεις, χρησιμοποιώντας είτε το μοντέλο τύρβης Spalart-Allmaras είτε  το k-ω. Από την σύγκριση των αποτελεσμάτων μεταξύ των μεθόδων συμπεραίνεται η ικανοποιητική ακρίβεια των παραδοχών της ολοκληρωματικής μεθόδου και η καλύτερη συμπεριφορά του Spalart-Allmaras σε ροές πλουμίων

Phytoplankton Blooms, Red Tides and Mucilaginous Aggregates in the Urban Thessaloniki Bay, Eastern Mediterranean

We investigated the plankton community composition and abundance in the urban marine environment of Thessaloniki Bay. We collected water samples weekly from March 2017 to February 2018 at the coastal front of Thessaloniki city center and monthly samples from three other inshore sites along the urban front of the bay. During the study period, conspicuous and successive phytoplankton blooms, dominated by known mucilage-producing diatoms alternated with red tide events formed by the dinoflagellates Noctiluca scintillans and Spatulodinium pseudonoctiluca, and an extensive mucilage aggregate phenomenon, which appeared in late June 2017. At least 11 known harmful algae were identified throughout the study, with the increase in the abundance of the known harmful dinoflagellate Dinophysis cf. acuminata occurring in October and November 2017. Finally, a red tide caused by the photosynthetic ciliate Mesodinium rubrum on December 2017 was conspicuous throughout the sampling sites. The above-mentioned harmful blooms and red tides were linked to high nutrient concentrations and eutrophication. This paper provides an overview of eutrophication impacts on the response of the unicellular eukaryotic plankton organisms and their impact on water quality and ecosystem service

performance over time and durability assessment of external thermal insulation systems with artificial stone cladding

The contribution describes an experimental programme on durability assessment using the accelerated ageing of an outer wall component consisting of plasterboard support, an external thermal insulation composite system (ETICS) in polystyrene and a cladding that was realised half with natural stone and the other half with cast stone. The sample was placed in front of the climatic chamber by means of a special frame, in the so-called door configuration. During the accelerated ageing, this sample was simultaneously monitored over time using temperatures probes and flowmeter tests in order to evaluate the decay of the thermal performance over time. The experimental research was conducted with the aim of assessing the decay in thermal performance of an ETICS covered with artificial stone, comparing it with a similar stratigraphy but with a natural stone cladding

Conjugation of a peptide autoantigen to gold nanoparticles for intradermally administered antigen specific immunotherapy

Antigen specific immunotherapy aims to tolerise patients to specific autoantigens that are responsible for the pathology of an autoimmune disease. Immune tolerance is generated in conditions where the immune response is suppressed and thus gold nanoparticles (AuNPs) are an attractive drug delivery platform due to their anti-inflammatory effects and their potential to facilitate temporal and spatial delivery of a peptide autoantigen in conjunction with pro-tolerogenic elements. In this study we have covalently attached an autoantigen, currently under clinical evaluation for the treatment of type 1 diabetes (PIC19-A3 peptide), to AuNPs to create nanoscale (<5 nm), negatively charged (−40 to −60 mV) AuNP-peptide complexes for immunotherapy. We also employ a clinically approved microneedle delivery system, MicronJet600, to facilitate minimally-invasive intradermal delivery of the nanoparticle constructs to target skin-resident antigen presenting cells, which are known to be apposite target cells for immunotherapy. The AuNP-peptide complexes remain physically stable upon extrusion through microneedles and when delivered into ex vivo human skin they are able to diffuse rapidly and widely throughout the dermis (their site of deposition) and, perhaps more surprisingly, the overlying epidermal layer. Intracellular uptake was extensive, with Langerhans cells proving to be the most efficient cells at internalising the AuNP-peptide complex (94% of the local population within the treated region of skin). In vitro studies showed that uptake of the AuNP-peptide complexes by dendritic cells reduced the capacity of these cells to activate naïve T cells. This indicator of biological functionality encourages further development of the AuNP-peptide formulation, which is now being evaluated in clinical trials

Hydrodynamic gene delivery in human skin using a hollow microneedle device

Microneedle devices have been proposed as a minimally invasive delivery system for the intradermal administration of nucleic acids, both plasmid DNA (pDNA) and siRNA, to treat localised disease or provide vaccination. Different microneedle types and application methods have been investigated in the laboratory, but limited and irreproducible levels of gene expression have proven to be significant challenges to pre-clinical to clinical progression. This study is the first to explore the potential of a hollow microneedle device for the delivery and subsequent expression of pDNA in human skin. The regulatory approved MicronJet600® (MicronJet hereafter) device was used to deliver reporter plasmids (pCMVβ and pEGFP-N1) into viable excised human skin. Exogenous gene expression was subsequently detected at multiple locations that were distant from the injection site but within the confines of the bleb created by the intradermal bolus. The observed levels of gene expression in the tissue are at least comparable to that achieved by the most invasive microneedle application methods e.g. lateral application of a microneedle. Gene expression was predominantly located in the epidermis, although also evident in the papillary dermis. Optical coherence tomography permitted real time visualisation of the sub-surface skin architecture and, unlike a conventional intradermal injection, MicronJet administration of a 50 μL bolus appears to create multiple superficial microdisruptions in the papillary dermis and epidermis. These were co-localised with expression of the pCMVβ reporter plasmid. We have therefore shown, for the first time, that a hollow microneedle device can facilitate efficient and reproducible gene expression of exogenous naked pDNA in human skin using volumes that are considered to be standard for intradermal administration, and postulate a hydrodynamic effect as the mechanism of gene delivery