Wind turbines and seismic hazard: a state-of-the-art review

Wind energy is a rapidly growing field of renewable energy, and as such, intensive scientific and societal interest has been already attracted. Research on wind turbine structures has been mostly focused on the structural analysis, design and/or assessment of wind turbines mainly against normal (environmental) exposures while, so far, only marginal attention has been spent on considering extreme natural hazards that threat the reliability of the lifetime-oriented wind turbine's performance. Especially, recent installations of numerous wind turbines in earthquake prone areas worldwide (e.g., China, USA, India, Southern Europe and East Asia) highlight the necessity for thorough consideration of the seismic implications on these energy harnessing systems. Along these lines, this state-of-the-art paper presents a comparative survey of the published research relevant to the seismic analysis, design and assessment of wind turbines. Based on numerical simulation, either deterministic or probabilistic approaches are reviewed, because they have been adopted to investigate the sensitivity of wind turbines' structural capacity and reliability in earthquake-induced loading. The relevance of seismic hazard for wind turbines is further enlightened by available experimental studies, being also comprehensively reported through this paper. The main contribution of the study presented herein is to identify the key factors for wind turbines' seismic performance, while important milestones for ongoing and future advancement are emphasized

Multi-hazard response analysis of a 5MW offshore wind turbine

Wind energy has already dominant role on the scene of the clean energy production. Well-promising markets, like China, India, Korea and Latin America are the fields of expansion for new wind turbines mainly installed in offshore environment, where wind, wave and earthquake loads threat the structural integrity and reliability of these energy infrastructures. Along these lines, a multi-hazard environment was considered herein and the structural performance of a 5 MW offshore wind turbine was assessed through time domain analysis. A fully integrated model of the offshore structure consisting of the blades, the nacelle, the tower and the monopile was developed with the use of an aeroelastic code considering the interaction between the elastic and inertial forces, developed in the structure, as well as the generated aerodynamic and hydrodynamic forces. Based on the analysis results, the dynamic response of the turbine's tower was found to be severely affected by the earthquake excitations. Moreover, fragility analysis based on acceleration capacity thresholds for the nacelle's equipment corroborated that the earthquake excitations may adversely affect the reliability and availability of wind turbines

Achaiki Iatriki : official publication of the medical society of western Greece and Peloponnesus

In the current issue, the editorial by Cauchi et al. argues for eco-friendly measures in endoscopy and emphasies the role of healthcare providers in reducing waste. The editorial adeptly employs the three Rs (Reduce, Reuse, Recycle) framework to tackle waste management, offering practical solutions. The editorial by Milionis et al. focuses on the reverse cascade screening for paediatric familial hypercholesterolaemia (FH), which is an upcoming tool for public health. Advantages, practices, and challenges regarding FH are thoroughly discussed. Lastly, the editorial by Fousekis et al. presents the main aspects of a chronic immune-mediated cutaneous disease, dermatitis herpetiformis (DH), which constitutes an extraintestinal manifestation of celiac disease, including its diagnosis, pathogenesis, and management. Moreover, this issue includes three review articles. The review article by Krontira et al. discusses the evolving data on the epidemiology, diagnostic approach and appropriate management of foreign body and caustic substance ingestion, based on updated guidelines published by gastroenterological and endoscopic societies. The review by Halliasos et al. provides data on the clinical presentation, diagnosis, and management of metastatic acute spinal cord compression, focusing on the importance of a multidisciplinary team approach, including spine surgeons, radiation oncologists, medical oncologists, palliative care clinicians, physiotherapists, and psychologists. Lastly, the review by Schinas et al. outlines the potential of immune modulation in the treatment of infections and the need for individualised approaches in the modern world of personalised medicine by examining some of the key strategies and immune-based therapies being developed to combat infectious diseases.peer-reviewe

Vadå, är jag redan gammal? : En kvalitativ forskningsstudie om äldre idrottslärares yrkesutövande i Stockholms läns grundskolor

Syfte och frågeställningar Syftet med denna forskningsstudie är att undersöka hur arbetssituationen för äldre idrottslärare ser ut inom skolan. Studien kommer att undersöka idrottslärarnas arbetsmiljö, hur de bedriver sin idrottsundervisning idag jämfört med tidigare samt hur undervisningen har förändrats i samband med införandet av nya läroplaner. Studien avslutas med att idrottslärarna reflekterar kring sin egen och yrkets framtid. Syftet har lett fram till följande frågeställningar: 1. Hur påverkas äldre idrottslärare av arbetsmiljön där idrottsundervisningen bedrivs? 2. Hur bedriver äldre idrottslärare sin idrottsundervisning i skolan idag jämfört med tidigare? 3. Hur har äldre idrottslärares undervisningsmetoder förändrats i samband med införandet av nya läroplaner? 4. Hur ser framtiden ut för de äldre idrottslärarna och idrottsläraryrket? Metod Forskningsstudien består av kvalitativa halvstrukturerade intervjuer. Vi tillämpade resenärsmetoden utifrån studiens explorativa syfte. Det riktade urvalet bestod av fem verksamma idrottslärare i grundskolan inom ålderskategorin 50–67 år. Efter transkriberingen av intervjuerna analyserades den insamlade informationen med analysmetoden grundad teori. Resultat Samtliga idrottslärare i vår forskningsstudie trivs med sin arbetssituation och sin arbetsmiljö. Samarbetet med skolledningen och övrig personal på skolan fungerar bra. I takt med införandet av nya läroplaner har idrottslärarnas undervisningsmetoder förändrats avseende såväl tid till förfogande för undervisning som undervisningsmetoder. Idrottslärarna berättar vidare att administrativa uppgifter tillkommit på senare år, vilket resulterat i en ökad arbetsbörda. Majoriteten av idrottslärarna i vår studie menar att variation i arbetsuppgifterna är bra för att avlasta den fysiska belastningen på kroppens rörelseapparat. Slutsats Vi har kommit fram till att idrottslärarnas arbetsuppgifter ökat samt skiftat i omfattning över tid. Pappersarbete har blivit ett allt vanligare inslag i deras arbetsuppgifter. Även idrottslärarnas förmedlingsrepertoar har förändrats, vilket innebär att deras undervisningsmetoder ser annorlunda ut idag jämfört med tidigare

Multi-criterion earthquake ground motion selection for a reliable estimate of seismic structural response

The uncertainty derived from the earthquake-induced ground motion affects severely the reliability of both design and assessment of structural seismic response. The key issue of the dissertation is to propose a novel theoretical and computational framework to select strong motions accounting for structural parameters and seismic motions characteristics. The first step was to assess the impact of Eurocode 8-based earthquake records selection procedure on the nonlinear response of a multi-storey, irregular reinforced concrete (R/C) building. The highly scattered inelastic response results highlighted the adverse implications of code-conformed records selection procedure in the reliability of structural performance prediction. Next, the upper-bound of the code-imposed range of structural periods, within which matching between the mean spectrum of the suite of motions and the target spectrum is enforced, was thoroughly examined. Particularly, the earthquake-induced lengthening of the fundamental period of five R/C buildings, designed according to modern seismic codes, was quantified. The results of this study showed that the upper-bound of the period range prescribed in Eurocode 8 for spectral matching could be reduced by 25%. Moreover, inelastic response spectra were calculated in terms of shifting the fundamental period due to the inelastic response. Simplified expressions were, also, derived that allow predicting the first-mode period elongation of various structural systems. Next, a novel, multi-criterion method for earthquake record selection procedure was proposed that accounts for both the dynamic characteristic of the structure studied and the variability among the seismic motions selected. The above improvements, which were incorporated in an integrated computational system (ISSARS), aim to compile suites of motions that are legitimate based on the prescribed code criteria and also lead to stable enough (i.e., of low variability) response results. The seismic excitation of three multi-storey R/C buildings using suites of motions that were selected and ranked according to the proposed multi-criterion method leaded to significantly lower structural response variability instead of using suites of motions selected with the conventional method. The reduced response variability induced an increase in the reliability of the predicted design values without being necessary to excite the structures modeled with numerous seismic motions.Η επιβαλλόμενη σεισμική δράση, μέσω της δυναμικής ανάλυσης χρονοϊστορίας των κατασκευών, επηρεάζει καίρια την αξιοπιστία του σχεδιασμού/αποτίμησης της σεισμικής απόκρισης των κατασκευών. Κεντρική στόχευση της διδακτορικής διατριβής αποτέλεσε η διατύπωση ενός καινοτόμου θεωρητικού και υπολογιστικού πλαισίου για την επιλογή και την αναγωγή των σεισμικών δράσεων συνεκτιμώντας χαρακτηριστικά της σεισμικής κίνησης, του εδάφους και της κατασκευής. Αρχικά, αποτιμήθηκε η επιρροή των διατάξεων του Ευρωκώδικα 8 για την επιλογή των σεισμικών κινήσεων στη μη-γραμμική απόκριση ενός πολυώροφου, μη-κανονικού κτιρίου από οπλισμένο σκυρόδεμα. Η υπολογισθείσα υψηλή διακύμανση των μεγεθών ανελαστικής απόκρισης κατέδειξε τις δυσμενείς επιπτώσεις από την εφαρμογή του κανονιστικού πλαισίου στην αξιοπιστία της ανάλυσης των κατασκευών. Ακολούθως, επανακαθορίστηκε το άνω όριο του εύρους των ιδιοπεριόδων, εντός του οποίου αποτιμάται η φασματική σύγκλιση των ομάδων από σεισμικές κινήσεις. Για το σκοπό αυτόν, διερευνήθηκε η επιμήκυνση της θεμελιώδους ιδιοπεριόδου των κατασκευών εξαιτίας της ανελαστικής τους απόκρισης, καταλήγοντας πως για τη μελέτη σύγχρονα σχεδιασμένων κτιρίων, το άνω όριο του εύρους των ιδιοπεριόδων, που προτείνει ο Ευρωκώδικας 8, μπορεί να μειωθεί κατά 25%. Επιπρόσθετα, υπολογίστηκαν μέσα ανελαστικά φάσματα απόκρισης σε όρους μεταβολής της δεσπόζουσας ιδιοπεριόδου, ενώ ταυτόχρονα προσδιορίστηκαν απλοποιημένες σχέσεις για την αξιόπιστη πρόβλεψη της ανελαστικής ιδιοπεριόδου διαφόρων δομικών συστημάτων. Στη συνέχεια, προτάθηκε μια πρωτότυπη, πολυκριτηριακή μεθοδολογία για την επιλογή σεισμικών κινήσεων, που συνεκτιμά κρίσιμα δυναμικά χαρακτηριστικά της κατασκευής καθώς και τη διακύμανση μεταξύ των σεισμικών κινήσεων. Η προτεινόμενη μεθοδολογία, που ενσωματώθηκε σε ένα ολοκληρωμένο υπολογιστικό σύστημα (ISSARS), στοχεύει στην επιλογή σεισμικών κινήσεων, που οδηγούν στον υπολογισμό μεγεθών απόκρισης με περιορισμένη διακύμανση και συνεπώς αυξημένη αξιοπιστία. Η διέγερση πολυωρόφων κτιρίων με ομάδες σεισμικών κινήσεων, που επιλέχθηκαν εφαρμόζοντας τη πολυκριτηριακή μεθοδολογία, οδήγησε σε μεγέθη σεισμικής απόκρισης με σημαντικά χαμηλότερη διακύμανση σε σχέση με αυτή, που υπολογίστηκε εξαιτίας της χρήσης των συμβατικά επιλεχθεισών ομάδων. Η μείωση στη διακύμανση της απόκρισης επέφερε σημαντική αύξηση στην αξιοπιστία των τιμών σχεδιασμού των κατασκευών, χωρίς την ταυτόχρονη απαίτηση διέγερσης των κατασκευών χρησιμοποιώντας μεγάλο αριθμό από σεισμικές κινήσεις

Vadå, är jag redan gammal? : En kvalitativ forskningsstudie om äldre idrottslärares yrkesutövande i Stockholms läns grundskolor

Syfte och frågeställningar Syftet med denna forskningsstudie är att undersöka hur arbetssituationen för äldre idrottslärare ser ut inom skolan. Studien kommer att undersöka idrottslärarnas arbetsmiljö, hur de bedriver sin idrottsundervisning idag jämfört med tidigare samt hur undervisningen har förändrats i samband med införandet av nya läroplaner. Studien avslutas med att idrottslärarna reflekterar kring sin egen och yrkets framtid. Syftet har lett fram till följande frågeställningar: 1. Hur påverkas äldre idrottslärare av arbetsmiljön där idrottsundervisningen bedrivs? 2. Hur bedriver äldre idrottslärare sin idrottsundervisning i skolan idag jämfört med tidigare? 3. Hur har äldre idrottslärares undervisningsmetoder förändrats i samband med införandet av nya läroplaner? 4. Hur ser framtiden ut för de äldre idrottslärarna och idrottsläraryrket? Metod Forskningsstudien består av kvalitativa halvstrukturerade intervjuer. Vi tillämpade resenärsmetoden utifrån studiens explorativa syfte. Det riktade urvalet bestod av fem verksamma idrottslärare i grundskolan inom ålderskategorin 50–67 år. Efter transkriberingen av intervjuerna analyserades den insamlade informationen med analysmetoden grundad teori. Resultat Samtliga idrottslärare i vår forskningsstudie trivs med sin arbetssituation och sin arbetsmiljö. Samarbetet med skolledningen och övrig personal på skolan fungerar bra. I takt med införandet av nya läroplaner har idrottslärarnas undervisningsmetoder förändrats avseende såväl tid till förfogande för undervisning som undervisningsmetoder. Idrottslärarna berättar vidare att administrativa uppgifter tillkommit på senare år, vilket resulterat i en ökad arbetsbörda. Majoriteten av idrottslärarna i vår studie menar att variation i arbetsuppgifterna är bra för att avlasta den fysiska belastningen på kroppens rörelseapparat. Slutsats Vi har kommit fram till att idrottslärarnas arbetsuppgifter ökat samt skiftat i omfattning över tid. Pappersarbete har blivit ett allt vanligare inslag i deras arbetsuppgifter. Även idrottslärarnas förmedlingsrepertoar har förändrats, vilket innebär att deras undervisningsmetoder ser annorlunda ut idag jämfört med tidigare