Towards a uniform earthquake risk model for Europe

Seismic risk has been the focus of a number of European projects in recent years, but there has never been a concerted effort amongst the research community to produce a uniform European risk model. The H2020 SERA project has a work package that is dedicated to that objective, with the aim being to produce an exposure model, a set of fragility/vulnerability functions, and socio-economic indicators in order to assess probabilistic seismic risk at a European scale. The partners of the project are working together with the wider seismic risk community through web tools, questionnaires, workshops, and meetings. All of the products of the project will be openly shared with the community on both the OpenQuake platform of the Global Earthquake Model (GEM) and the web platform of the European Facilities for Earthquake Hazard and Risk (EFEHR)

The European Seismic Risk Model 2020 (ESRM20)

This study describes the development of the various components of the European Seismic Risk Model 2020 (ESRM2020) which will be able to generate, using open-source software developed by the GEM Foundation (the Open Quake-engine), a number of Europe-wide risk metrics including average annualised human and economic losses (AAL), probable maximum losses (PML), and risk maps showing the losses for specific return periods or scenario events. The latest developments towards pan-European exposure models for residential and non-residential buildings and fragility/vulnerability models for damage, economic loss and casualty assessment will be presented. For engineered buildings within the exposure model (reinforced concrete, steel), a simulated design is undertaken using the key aspects of seismic design codes in force across Europe over the past 100 years. The designed MDOF building is then transformed to a SDOF model and nonlinear dynamic analyses are run using a large number of ground motion records, after which cloud analysis is used to develop the fragility functions. For non-engineered buildings (unreinforced masonry, confined masonry, adobe), the SDOF models have been directly developed from simplified formulae, experimental tests and previous studies. Collaboration from local experts at various stages of the model development, initiated through workshops, is an important component of the model, as well as the extensive calibration and validation

The study of the influence of the creep phenomenon on the loads that the final lining of a tunnel is designed to undertake

145 σ.Πολλές φορές κατά τη διάνοιξη και κατασκευή σηράγγων, παρατηρούνται έντονες παραμορφώσεις στην άμεση υποστήριξη ή υψηλές πιέσεις επί της τελικής επένδυσης περιμετρικά της σήραγγας. Το γεγονός αυτό συχνά οφείλεται στο χρονικά εξαρτημένο φαινόμενο του ερπυσμού, η μελέτη του οποίου τις περισσότερες φορές παραλείπεται πριν ξεκινήσει η κατασκευή. Ωστόσο, στην περίπτωση που η σήραγγα διανοίγεται σε χαμηλής ποιότητας βραχόμαζα, οι συνέπειες του φαινομένου του ερπυσμού είναι δυνατό να προκαλέσουν σοβαρά προβλήματα που μπορεί να οδηγήσουν ακόμη και σε αστοχία του έργου. Σκοπός της παρούσας διπλωματικής εργασίας είναι να μελετηθεί η επίδραση του φαινομένου του ερπυσμού στην ανάπτυξη των φορτίων που καλείται να παραλάβει η τελική επένδυση σήραγγας κυκλικής διατομής (D=10m) και βάθους διάνοιξης H=100m και η συσχέτιση των φορτίων αυτών με τις μηχανικές και ιξωδοελαστικές παραμέτρους του γεωυλικού. Αρχικά, παρουσιάζονται όλα τα θεωρητικά στοιχεία τα οποία χρησιμοποιήθηκαν για τη ολοκλήρωση της συγκεκριμένης εργασίας και στη συνέχεια, γίνεται η περιγραφή του προβλήματος που μελετήθηκε. Το πρόβλημα επιλύεται σε δύο διαστάσεις στον κώδικα πεπερασμένων στοιχείων ABAQUS, ενώ το προσομοίωμα που χρησιμοποιήθηκε στις αναλύσεις δημιουργήθηκε στο σχεδιαστικό περιβάλλον του MSC Patran. Έπειτα από εκτεταμένη έρευνα στη διεθνή βιβλιογραφία σχετικά με το φαινόμενο του ερπυσμού, πολύτιμη βοήθεια στην περαίωση της εργασίας προσέφεραν οι διδακτορικές διατριβές των Debernardi (2008) και Aristorenas (1987). Οι Debernardi (2008) και Aristorenas (1987) στο πλαίσιο των διδακτορικών τους διατριβών πραγματοποίησαν πειράματα ερπυσμού, για τη βαθμονόμηση των καταστατικών προσομοιωμάτων που πρότειναν. Στην παρούσα διπλωματική εργασία, για την προσομοίωση της ερπυστικής συμπεριφοράς της περιβάλλουσας βραχόμαζας χρησιμοποιήθηκε το καταστατικό προσομοίωμα των Singh & Mitchell (1968). Ωστόσο, επιλέχθηκε να μην ποσοτικοποιηθεί η ερπυστική συμπεριφορά μέσω των παραμέτρων που υπεισέρχονται στο συγκεκριμένο καταστατικό προσομοίωμα, καθώς δεν είναι ‘’φιλικές’’ και ευκολονόητες προς το μηχανικό. Προέκυψε λοιπόν, η ανάγκη έκφρασης τους ως προς κάποιες πιο ‘’προσιτές’’, που να παραπέμπουν σε συγκεκριμένες ομάδες βραχόμαζας. Συνεπώς, από την επεξεργασία των αποτελεσμάτων των πειραμάτων που εκτέλεσαν οι Debernardi (2008) και Aristorenas (1987) η ερπυστική συμπεριφορά ποσοτικοποιήθηκε μέσω της παραμέτρου φcr, που αποτελεί το μέτρο της ερπυστικής παραμόρφωσης που είναι δυνατό να αναπτυχθεί. Στη συνέχεια, πραγματοποιήθηκε πλήθος αριθμητικών αναλύσεων, τα αποτελέσματα των οποίων μελετήθηκαν και συγκρίθηκαν ποσοτικά και ποιοτικά. Προέκυψαν αποτελέσματα για τις αναπτυσσόμενες μετατοπίσεις και πλαστικές παραμορφώσεις περιμετρικά της σήραγγας, τις κατανομές των πιέσεων επί του εκτοξευόμενου σκυροδέματος και επί της τελικής επένδυσης και τις επιπρόσθετες πιέσεις στην τελική επένδυση λόγω της επιβολής του ερπυσμού. Σημαντικό ρόλο στις αναλύσεις έλαβαν ο συντελεστής οριζόντιων τάσεων K, ο δείκτης βραχόμαζας σc/po,m και ο ερπυστικός συντελεστής φcr. Διατηρώντας κάθε φορά κάποιες παραμέτρους σταθερές, μελετήθηκε η επίδραση των παραμέτρων που μεταβάλλονται, στο φορτίο που καλείται να αναλάβει η τελική επένδυση. Ιδιαίτερη έμφαση δόθηκε στην επίδραση της παραμέτρου φcr στην εκδήλωση του φαινομένου. Στο τελευταίο κεφάλαιο της διπλωματικής εργασίας συνοψίζεται το σύνολο των συμπερασμάτων που προέκυψαν καθ’ όλη τη διάρκεια της εκπόνησής της. Συμπερασματικά, παρατηρήθηκε πως η επιβολή του ερπυσμού προσαυξάνει τα φορτία που καλείται να παραλάβει η τελική επένδυση κατά ένα ποσοστό της τάξεως του 20-30%, ποσοστό σημαντικό ώστε το φαινόμενο να μην αγνοείται κατά το σχεδιασμό των σηράγγων.The development of intense deformation of the temporary support section and high stresses on the final lining are widely observed during the excavation and construction of tunnels, especially in the case of unfavourable geotechnical conditions. The specific problems are usually assigned to the time-dependent behaviour of the surrounding geomaterial, the study of which is often ignored before the beginning of the construction. However, in cases of tunnels excavated into poor quality rock mass, the consequences of creep can cause serious problems that may even result in failure of the structure. The present thesis intends to study the influence of the creep phenomenon on the development of the loads, which the final lining of a tunnel with circular cross section (D=10m) and excavation depth H=100m is designed to undertake, as well as the correlation of these loads with the mechanical and viscoelastic parameters of the geomaterial. Initially, the theory that was applied in the present diploma thesis is presented and the problem that was studied is described. The specific problem is solved through two-dimensional analysis using the finite element code ABAQUS 6.9.1, while the numerical model used in the analysis, was designed in the environment of MSC Patran. Valuable data to the completion of the present thesis was offered by the PhD theses of Debernardi (2008) and Aristorenas (1987), after thorough search of the international bibliography referring to the creep phenomenon. Debernardi (2008) and Aristorenas (1987) carried out creep experiments in the frame of their PhD theses, in order to calibrate the constitutive models they proposed. The constitutive model of Singh & Mitchell (1968) was used for the simulation of the creeping behaviour of the surrounding rock mass in the present thesis. However, we choose not to quantify initially the creep behaviour through the parameters entered into the specific constitutive model, because they are not friendly and easy to understand. Therefore, it was required to express the above mentioned parameters according to more characteristic results by Debernardi (2008) and Aristorenas (1987), resulted in the quantification of the creeping behaviour through the parameter φcr, which depicts the amount of the creep deformation that can potentially be developed. Subsequently, a large number of numerical analyses was carried out, the results of which were studied and compared qualitatively and quantitatively. These results refer to the developed deformations and plastic strains around the tunnel section, the stress distributions on the shotcrete and the final lining and the additional stresses on the final lining due to the imposition of creep. The impact of the horizontal stress ratio K, the geotechnical conditions index σc/p0,m and the creep coefficient φcr was the most significant, among all the parameters, in the analyses. Maintaining some parameters constant each time, the influence of the variable parameters, on the load to be undertaken by the final lining of the tunnel was studied. Particular emphasis was placed on the effect of the parameter φcr on the occurrence of the phenomenon. In the last chapter of the thesis all the conclusions obtained during its progress are summarized. Finally, it is observed that the imposition of creep increases the loads that final lining is designed to undertake at a rate of 20-30%, so the phenomenon of creep must be taken into account during the construction of tunnels.Βενετία Γ. Δεσποτάκ

Exposure model for European seismic risk assessment

Building exposure and vulnerability models for seismic risk assessment have been the focus of a number of European projects in recent years, but there has never been a concerted effort among the research community to produce a uniform European risk model. The European Commission's Horizon 2020 SERA project has a work package that is dedicated to that objective, through the development of an exposure model, an associated set of fragility/vulnerability models, and a database of socioeconomic indicators in order to calculate probabilistic integrated seismic risk at a European scale. This article provides details of the development of the first versions of the European exposure model that describe the distribution of the main residential, industrial and commercial building classes across all countries in Europe, as well as their occupants and replacement costs. The v0.1 of the European exposure model has been integrated within the Global Earthquake Model's global exposure and risk maps. Preliminary analyses using the model show that almost 35% of the residential population in Europe is exposed to a 475-year return period peak ground acceleration (PGA) hazard of at least 0.1 g, thus highlighting the importance of European seismic risk modeling and mitigation

Exposure model for European seismic risk assessment

Building exposure and vulnerability models for seismic risk assessment have been the focus of a number of European projects in recent years, but there has never been a concerted effort among the research community to produce a uniform European risk model. The European Commission's Horizon 2020 SERA project has a work package that is dedicated to that objective, through the development of an exposure model, an associated set of fragility/vulnerability models, and a database of socioeconomic indicators in order to calculate probabilistic integrated seismic risk at a European scale. This article provides details of the development of the first versions of the European exposure model that describe the distribution of the main residential, industrial and commercial building classes across all countries in Europe, as well as their occupants and replacement costs. The v0.1 of the European exposure model has been integrated within the Global Earthquake Model's global exposure and risk maps. Preliminary analyses using the model show that almost 35% of the residential population in Europe is exposed to a 475-year return period peak ground acceleration (PGA) hazard of at least 0.1 g, thus highlighting the importance of European seismic risk modeling and mitigation

Model of seismic design lateral force levels for the existing reinforced concrete European building stock

As part of the development of a European Seismic Risk Model 2020 (ESRM20), the spatial and temporal evolution of seismic design across Europe has been studied in order to better classify reinforced concrete buildings (which represent more than 30% of the approximately 145 million residential, commercial and industrial buildings in Europe) and map them to vulnerability models based on simulated seismic design. This paper summarises the model that has been developed to assign the years when different seismic design levels (low code, moderate code and high code) were introduced in a number of European countries and the associated lateral forces that were specified spatially within each country for the low and moderate codes for typical reinforced concrete mid-rise buildings. This process has led to an improved understanding of how design regulations evolved across Europe and how this has impacted the vulnerability of the European residential building stock. The model estimates that similar to 60% of the reinforced concrete buildings in Europe have been seismically designed, and of those buildings similar to 60% have been designed to low code, similar to 25% to moderate code and 15% to high code. This seismic design model aims at being a dynamic source of information that will be continuously updated with additional feedback from local experts and datasets. To this end, all of the data has been made openly available as shapefiles on a GitLab repository

Model of seismic design lateral force levels for the existing reinforced concrete European building stock

As part of the development of a European Seismic Risk Model 2020 (ESRM20), the spatial and temporal evolution of seismic design across Europe has been studied in order to better classify reinforced concrete buildings (which represent more than 30% of the approximately 145 million residential, commercial and industrial buildings in Europe) and map them to vulnerability models based on simulated seismic design. This paper summarises the model that has been developed to assign the years when different seismic design levels (low code, moderate code and high code) were introduced in a number of European countries and the associated lateral forces that were specified spatially within each country for the low and moderate codes for typical reinforced concrete mid-rise buildings. This process has led to an improved understanding of how design regulations evolved across Europe and how this has impacted the vulnerability of the European residential building stock. The model estimates that similar to 60% of the reinforced concrete buildings in Europe have been seismically designed, and of those buildings similar to 60% have been designed to low code, similar to 25% to moderate code and 15% to high code. This seismic design model aims at being a dynamic source of information that will be continuously updated with additional feedback from local experts and datasets. To this end, all of the data has been made openly available as shapefiles on a GitLab repository