Enabling development of a decision support system for increasing the resilience of transportation infrastructure based on combined use of terrestrial and airborne sensors and advanced modelling tools
The PANOPTIS Horizon 2020 project started in June 2018 comprising 14 partners from the industry and academia. It aims to improve the resilience (ability to adapt) of road infrastructures and ensure reliable network availability under unfavorable conditions, such as extreme weather, landslides, and earthquakes. It combines down-scaled climate change scenarios, structural and geotechnical simulation tools, and online data from sensors (terrestrial and airborne) to provide the operators with an integrated tool able to support effective management of their infrastructures at the planning, maintenance and operation level. The following technologies are implemented in the PANOPTIS tool:
- Reliable quantification of climatic, hydrological and atmospheric stressors
- Multi-Hazard vulnerability modules and assessment toolkit
- Development of a forecasting module to provide high-resolution tailored weather and precipitation forecasts
- Improved assessment of structural and geotechnical safety risk
- Improved multi-temporal, multi-sensor observations with robust spectral analysis, computer vision and machine-learning damage diagnostics for diverse road infrastructure systems
- Detailed and wide area transport asset mapping, integrating state-of-the-art mobile mapping and making use of UAV technology
- Design of a Holistic Resilience Assessment Platform
- Design of a Common Operational Picture including a Decision Support System, an enhanced visualization interface and an Incident Management System.
Project Funding
European Commission – Innovation and Networks Executive Agency
Horizon 2020, Mobility for Growth
H2020-MG-2017-Two-Stages
Collaborators
Airbus Defence and Space SAS
National Technical University of Athens
ACCIONA Construcción SA
Egnatia Odos AE
Future Intelligence Ltd
Universiteit Twente
French Institute of Science and Technology for Transport, Development and Networks
Finnish Meteorological Institute
Aristotle University of Thessaloniki
Sofistik Hellas AE
C4Controls Ltd
Hydrometeorological Innovative Solutions
Confederation of Organisations in Road Transport Enforcement
Time Period
Jun 2018 – May 2022
Relevant Publications
Chatzidaki A., Ntaifoti A., Bilionis D.., Gantes C., Vamvatsikos D. (2023). Fatigue damage assessment of the Egnatia Odos sign-support structures under spatially-correlated time-varying wind fields. Proceedings of the 10th Hellenic National Conference on Steel Structures, Athens, Greece. (in greek)
Abstract | A methodology is proposed for assessing the long-term wind-induced fatigue damage accumulation of steel sign-supporting structures of highways, as it applies to Egnatia Odos. These structures are usually configured as portal, L-shaped or T-shaped frames, consisting of one or two columns and a horizontal beam that supports the sign. During their lifetime, they are exposed to environmental conditions thus being susceptive to corrosion, while the critical load is the wind that subjects them to fatigue due to its dynamic nature. To this scope, the cumulative fatigue damage is computed for the critical connections of the sign-supporting structures on a site-agnostic basis for 10min loading intervals, both for corroded and for non-corroded structures. This data is combined with 10min wind time-series that are compatible with the long-term weather hazard at the location of the structures and are computed based on alternative climate change scenarios. The aim is to assess the damage accumulation due to fatigue for the critical connections of the structures during their lifetime. The proposed methodology allows assessing the long-term risk due to fatigue for an ensemble of spatially distributed sign-support structures and is incorporated into a tool that aims to help road operators rapidly assess the state of the highway assets and help them efficiently manage their inspections.
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Chatzidaki A., Gerontati A., Vamvatsikos D. (2022). Seismic damage and implied traffic delay assessment for a highway bridge of Egnatia Odos Greece. Proceedings of the 3rd European Conference on Earthquake Engineering and Seismology (3ECEES), Bucharest, Romania.
Abstract | The seismic damage and the implied traffic delays are assessed for two structurally independent twin bridges, one per travel direction, which form the G7 bridge of the Egnatia highway in Greece. They are reinforced concrete structures with a monolithic pier-to-deck connection that were built using the cantilever method of construction. To enhance the seismic assessment resolution, a component-based approach is followed that allows evaluating damage scenarios for individual critical bridge components and propagating them to assess the performance of the entire system. This necessitates linking the component damages to the actions that the road operator would take in order effect repairs, i.e., by reducing the speed limit in any of the lanes and/or closing any of them until repairs are finished. These interventions typically lead to traffic delays for the entire highway that are computed on an event basis via event-based probabilistic seismic hazard analysis by considering the component-to-asset and asset-to-system interdependencies. The aim is to develop a decision support tool for pre-event risk assessment and rapid post-event inspection of critical road infrastructure by combining hazard, vulnerability and sensor
information to predict the resulting consequences both on the asset and the system level at every step during an asset’s recovery back to full functionality.
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Bilionis D.V., Vlachakis K., Bezas M-Z., Tibolt M., Vamvatsikos D., Vayas I. (2022). Performance-based assessment of a steel lattice power-transmission tower: A case study in Germany. Proceedings of the 3rd International Conference on Natural Hazards & Infrastructure ICONHIC 2022, Athens, Greece.
Abstract | Power transmission towers are tall steel lattice structures used for supporting the conductors of a power transmission line, constituting essential parts of an entire power network. Past experience has shown that even a failure of a single tower can cause cascading effects to its adjacent towers leading to a total collapse of a whole line. Transmission towers are susceptible to severe weather conditions including low temperatures, snow and high winds. Specifically, high winds in combination with ice accumulation increase the lateral and vertical loads to levels causing damages ranging from local failures to global collapse. This effect is even more intense in case of aged towers with members weakened by corrosion effects. Herein, the focus is on a single suspension transmission tower widely used in Central Europe and designed according to the EN 50341-1:2012 and EN 50341-2-4:2016 assuming installation in Germany. The structure’s fragility in both initial and corroded state against wind and icing loads was estimated via nonlinear dynamic analyses. The climatic hazard was estimated by deriving the joint probability of wind speed and ice thickness based on meteorological data obtained for Central-East Germany. Finally, the assessment of the structure’s risk for each of the two states considered was made by combining the tower’s fragility results with the climatic hazard. Assessing the risk of a single tower is a precursor of estimating the reliability of an entire power transmission network, offering a useful decision-support tool on the need to maintain or upgrade a power line network.
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Gerontati A., Bilionis D.V., Vamvatsikos D., Tibolt M. (2022). Modular modeling and risk assessment of power transmission lines under extreme weather hazards. Proceedings of the 3rd International Conference on Natural Hazards & Infrastructure ICONHIC 2022, Athens, Greece.
Abstract | Power transmission lines are the “highways” of electricity, consisting of conductors supported on steel towers. Transmission towers are categorized as support or angle/dead-end based on their capability to resist along-line loads transmitted by the conductors. They are vulnerable to severe weather and in particular the combination of high winds and ice accretion that could lead to catastrophic failures. It is thus of great interest in the system design to arrest the propagation of a single tower failure that may trigger a series of failures of adjacent ones, considerably lengthening the duration of power outage. A modular multi-span model of a power line is proposed for the assessment of the behavior of the tower-line system and the severity evaluation of such failures. Fault tree analysis is employed to examine the failure propagation to adjacent towers under extreme weather hazard, which allows the assessment of consequences at the level of an entire system of interleaved support and angle/dead-end transmission towers. The aggregated economic losses for an operational lifetime of 60 years are investigated using the proposed model versus a simplified approach, where all towers are exclusively characterized as support ones without considering successive failures.
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Chatzidaki A., Vamvatsikos D., Auvinen M., Hellsten A., Barmpas F., Lehtonen I. (2022). A baseline approach to downscaling Euro-CORDEX data for wind hazard assessment of the Egnatia Odos highway. Proceedings of the 3rd International Conference on Natural Hazards & Infrastructure ICONHIC 2022, Athens, Greece.
Abstract | The wind hazard is assessed for the Egnatia Odos highway in Greece by considering Climate Change effects via the Euro-CORDEX future climatic projections. The aim is to derive spatially correlated region-wide wind fields for a stochastic event set of thousands of storm realizations that are suitable for risk and resilience assessment of the entire highway network. The coarse spatial and temporal resolutions of the Euro-CORDEX wind projections prohibit their use as a direct input in weather-related risk and resilience assessment of highway structures that may measure down to a few meters in size and require at most 10-min average wind speeds. To improve the temporal scale resolution, we leverage machine learning tools and continuous measurements from National weather stations to generate composite “Frankenstein” days comprising 144 jigsaw pieces of actually measured 10-min wind time-histories that are scaled and matched together to form a continuous daily record. These point-estimates, valid only at the locations of the weather stations, are expanded spatially by employing high-fidelity Computational Fluid Dynamic simulations that take into account the topographic complexity of the site to simulate turbulent wind flows, thus generating spatially correlated wind fields of 10-min average wind speeds. These allow estimating load distribution and risk on (i) an event-by-event basis and (ii) in the long-term for an ensemble of spatially-distributed highway assets that are vulnerable to wind actions, such as signpost bridges and power network pylons.
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Vamvatsikos D., Chatzidaki A. (2022). The HAPI sensor-aware framework for infrastructure risk and resilience assessment. Proceedings of the 3rd International Conference on Natural Hazards & Infrastructure ICONHIC 2022, Athens, Greece.
Abstract | The (new) 20’s have allowed us to dream big on protecting our infrastructure from natural hazards. Powerful computers, machine learning, terrestrial and airborne sensors are at our disposal to help us quantify the consequences of potential hazardous events that may come in the future, are already unfolding, or have already happened. Owing to its origins in four European projects, namely HYPERION, ARCHYTAS, PANOPTIS and INFRASTRESS, the HAPI framework has been formulated to perform pre/trans/post-event risk and resilience assessment of diverse infrastructure, comprising different layers of networked, loosely-connected or autonomous assets within a city, region or country. Building upon the well-worn basis of hazard-exposure-vulnerability that underpins practically all insurance risk estimates, HAPI enables assessment of cascading (e.g., mudflow/landslide after earthquake) and cotemporaneous (e.g., extreme precipitation, temperature, ice and wind scenario) hazards, while it offers sensor integration with near-real-time updating of predictions based on hazard/asset/consequence information input. Both “static” memoryless hazards (e.g., earthquake), as well as “dynamic” time-dependent hazards (e.g., climate projections) are incorporated in tandem with static/dynamic vulnerabilities, allowing the tracking of complex phenomena, such as climate change, and their effect on the aging/corrosion/fatigue of a diverse set of assets, including buildings, bridges, piping, powerlines, highways and cultural heritage monuments. At the very basis lies a vast database of hazard and asset realization scenarios, employing Total Probability Discrete Event Simulation to explicitly track network interdependencies and propagate uncertainty from our source information to the projected integrated-system functionality and eventual recovery.
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Hernández-Montes E., Chatzidaki A., Gill-Martin L.M., Aschheim M., Vamvatsikos D. (2022). A seismic design procedure for different performance objectives for post-tensioned walls. Journal of Earthquake Engineering, 26(1): 475-492.
Abstract | A method is presented for the design of unbonded post-tensioned concrete walls for seismic loading to satisfy multiple performance objectives. It takes advantage of the fact that the initial stiffness of the wall is nearly independent of the amount of post-tensioning reinforcement, and thus the fundamental period of the building can be considered to be a stable parameter in design of walls of a given cross section, independent of the degree of post-tensioning. The design spectra used to follow the specification provided in Eurocode 8 considering the probability of exceedance of the seismic action. A detailed example is provided.
Vamvatsikos D., Chatzidaki A. (2021). Fragility and Loss assessment via mixed probabilistic models of seismic demand. Proceedings of the 17th World Conference on Earthquake Engineering (17WCEE), Sendai, Japan
Abstract | A mixture model is presented for combining the results of different models or analysis approaches into a single probabilistic seismic demand model that is suitable for fragility assessment. A structure can be represented using different model types or even levels of resolution for the same type, while it may also be analyzed via methods of different complexity, most notably static versus dynamic nonlinear approaches. Combining the results from different sources can be beneficial as it allows updating the results of a simpler approach or combining the strengths of two different models. For example, as the static pushover analysis offers inexpensive yet low-fidelity demand assessment at any level of intensity, its results may be locally or globally updated by adding stripes of (computationally expensive) response history analysis. On the modelling side, different model types may offer accuracy advantages in complementary response regions. This is the case of distributed-plasticity fiber models that offer higher fidelity for reinforced concrete frames at low (pre-capping) deformations, while lumped-plasticity models are more reliable for larger (post-capping) deformations closer to collapse. Through the combination of the results of multiple models of differing fidelity we can potentially better capture the performance of a structure at all levels of seismic intensity. By employing a minimal 5 parameter power-law-based model we offer viable options for forming mixed probabilistic seismic demand models that can combine both different models and different analysis methods into a single output suitable for fragility and loss assessment.
Loli M., Chatzidaki A., Vamvatsikos D., Gazetas G. (2021). Seismic vulnerability of motorway bridge on active landside. Proceedings of the 17th World Conference on Earthquake Engineering (17WCEE), Sendai, Japan
Abstract | The western section of Egnatia Odos motorway in Greece runs through a challenging mountainous terrain where geohazards are exacerbated by moderate seismicity. Located a few kilometers east of the town of Metsovo, the twin girder bridges of the Panagia interchange have their central piers founded on an active landslide. Being part of a research project that aims to develop a tool for rapid inspection and assessment of the motorway, this study presents a thorough seismic vulnerability analysis of the hybrid caisson–pile group foundation system that supports the most critical piers of the interchange. This foundation system has been designated as a slope stabilizing measure, in addition to carrying the loads transmitted by the bridge superstructure. Numerical modelling with nonlinear 3D finite elements has been employed, together with site-specific hazard-consistent selection of ground motion records. A hybrid numerical approach has been developed using segregated models of varying refinement with rational approximation of interactions between the nonlinear response of soil, the movement of the slope, the kinematic distress imposed upon the foundation and the inertial loads from the vibration of the superstructure. The method estimates pile performance under large-scale, dynamic landslide action with sufficient engineering accuracy for cases where slope actions dominate the response. The softening behavior of the sliding surface is calibrated versus monitored slope displacements. The effect of groundwater recharge after heavy rainfall is incorporated in the vulnerability analysis in a simplified manner, using different scenarios for water table elevation. Focusing on the performance of the foundations, damage is described in terms of their permanent displacements and curvatures. Results indicate that a range of excitations with an exceedance
probability of 2% in 50 years are capable of inflicting substantial permanent pile damage, even complete failure, if combined with a fully saturated soil condition. The computed residual foundation displacements can serve as input for a detailed structural model simulating the performance of the superstructure for estimating the bridge vulnerability.
Vamvatsikos D., Melissianos V., Kostaridis A., Kazantzi A.K, Karaferis N., Chatzidaki A., Diagourtas D., Bakalis K. (2021). The PANOPTIS-INFRASTRESS framework for infrastructure risk assessment. Proceedings of the 8th International Conference on Civil Protection & New Technologies (SafeGreece 2021), Athens, Greece.
Chatzidaki A., Vamvatsikos D. (2021). Mixed probabilistic seismic demand models for fragility assessment. Bulletin of Earthquake Engineering, 19: 6397–6421.
Abstract | A mixture model approach is presented for combining the results of different models or analysis methods into a single probabilistic demand model for seismic assessment. In general, a structure can be represented using models of different type or different number of degrees of freedom, each offering a distinct compromise in computational load versus accuracy; it may also be analysed via methods of different complexity, most notably static versus dynamic nonlinear approaches. Employing the highest fidelity options is theoretically desirable but practically infeasible, at best limiting their use to calibrating or validating lower fidelity approaches. Instead, a large sample of low fidelity results can be selectively combined with sparse results from higher fidelity models or methods to simultaneously capitalize on the frugal nature of the former and the low bias of the latter to deliver fidelity at an acceptable cost. By employing a minimal 5 parameter power-law-based surrogate model we offer two options for forming mixed probabilistic seismic demand models that (i) can combine different models with varying degree of fidelity at different ranges of structural response, or (ii) nonlinear static and dynamic results into a single output suitable for fragility assessment.
Fasoulakis Z., Vamvatsikos D., Papadopoulos V. (2021). Buckling strength of bolted steel members from plain angle sections with multivariate stochastic imperfections. Proceedings of the 4th International Conference on Uncertainty Quantification in Computational Sciences and Engineering UNCECOMP 2021, Athens, Greece.
Abstract | Spatial uncertain quantities such as the geometric imperfections are found of paramount importance when investigating the behaviour of thin-walled structures. The present work addresses the probabilistic estimation of the buckling capacity of single-bolted members from plain angle sections with stochastic geometric imperfections. The simulation is based on detailed experimental data of imperfections measured by an inhouse built set-up. The quatro-variate non-stationary stochastic processes herein combine the spectral representation method along with the method of separation, incorporating correlations between the imperfection components. The spectral separability check is also performed through a minor investigation. A large-scale nonlinear finite-element problem is defined to estimate the stochastic buckling capacities (in the frame of Monte Carlo simulation) for a bolted angle-section column. More uncertain parameters are then included, namely material properties and lateral load (wind pressure), towards an extended range of applicability. To this end, in order to improve the computational performance, the Latin hypercube sampling method is adopted. The resulting density distributions, presented in both tabular and graphical forms, reveal the influence of each parameter (and their combinations) on the buckling load variability and can be used also for probabilistic assessment.
Kazantzi A. K., Vamvatsikos D. (2021). Practical performance-based design of friction pendulum bearings for a seismically isolated steel top story spanning two RC towers. Bulletin of Earthquake Engineering, 19: 1231-1248.
Abstract | A case study of performance-based design is presented for a seismically isolated steel structure that rests on top of two adjacent high-rise reinforced concrete towers, the latter separated by means of an expansion joint. The isolation system comprises Friction Pendulum Bearings (FPBs) that are designed to accommodate two salient characteristics of the system. First, the isolated top floor is subjected to narrow-band floor acceleration histories as the ground motion excitation is filtered by the dynamic response of the supporting towers. Second, the displacement demands imposed to the FPBs are affected by the in-phase or out-of-phase movement of the supporting structures, with the latter case potentially giving rise to higher displacement capacity requirements for the bearings. In a search for a solution beyond conventional design norms, the probability of bearing failure associated with a wide range of FPB displacement capacities was determined via an explicitly risk-consistent performance-based seismic design. Overall, the case-specific design approach is shown to be able to meet any desired performance objective, consistently determining the final compromise between safety, cost-efficiency and practicability.
Chatzidaki A., Bakalis K., Vamvatsikos D. (2020). Seismic resilience assessment for the G7 highway bridge in Greece. Proceedings of the 11th European Conference on Structural Dynamics (EURODYN 2020), Athens, Greece
Abstract | The seismic risk is assessed for two twin bridges, one per direction, forming the G7 branch of the Egnatia Odos highway in Greece. These are structurally independent horizontally-curved cantilevered-deck three-span reinforced concrete structures with a monolithic pier-to-deck connection that have been designed circa 2004 according to Greek and European standards. The aim is to develop a tool for pre-event risk assessment and rapid post-event inspection of critical road infrastructure by combining hazard, vulnerability and sensor information (where available) to predict the resulting consequences. To enhance the assessment resolution, a component-based approach is followed, allowing us to evaluate damage scenarios for individual critical components (i.e., piers and bearings) and propagate them to the system-level performance. Consequences are quantified in terms of repair losses, downtime, and traffic capacity losses, the latter identified as the number of closed lanes and the allowable speed limit for the open ones. This allows tracing back the consequences after an event to individual bridge components to help road operators establish bridge inspection prioritization protocols and manage associated incidents, facilitating the rapid assessment of the state of the bridge and optimal recovery to full functionality.
Chatzidaki A., Vamvatsikos D. (2019). Mixed probabilistic seismic demand models for fragility assessment. Proceedings of the SECED 2019 Conference, Greenwich, UK
Abstract | A mixture model is presented for combining the results of different models or analysis approaches into a single probabilistic seismic demand model that is suitable for fragility assessment. A structure can be represented using different model types or even levels of resolution for the same type, while it may also be analysed via methods of different complexity, most notably static versus dynamic nonlinear approaches. Combining the results from different models or analysis methods can be beneficial as it allows updating the results of a simpler approach or combining the strengths of two different models. For example, different model types may offer accuracy advantages in complementary response regions. This is the case of distributed-plasticity fiber models that offer higher fidelity for reinforced concrete frames at low (pre-capping) deformations, while lumped-plasticity models are more reliable for larger (postcapping) deformations closer to collapse. Through the combination of the results of both models we can potentially better capture the performance of the frame at all levels of seismic intensity. By employing a minimal 5 parameter power-law-based model we offer viable options for forming mixed probabilistic seismic demand models that can combine both different models and different analysis methods into a single output suitable for fragility assessment.
Bakalis K., Vamvatsikos D., Grant D.N., Mistry A. (2019). Downtime assessment of base-isolated liquid storage tanks. Proceedings of the SECED 2019 Conference, Greenwich, UK
Abstract | Seismic base isolation is examined as a design alternative for supporting industrial facility liquid storage tanks against earthquake loading. A 160,000m3 liquid storage tank is adopted as a case study, for which two designs are assessed, one with and one without base isolation. Using a nonlinear surrogate model and a set of ground motion records selected using the conditional spectrum approach for the average spectral acceleration intensity measure, Incremental Dynamic Analysis is employed to derive seismic fragility curves. Consequences of damage are evaluated in terms of downtime, considering the characteristics of petrochemical storage tanks, whereby any repair requires a lengthy list of actions dictated by health and safety requirements. The results reveal considerable benefits when base-isolation is employed, by drastically reducing downtime when sufficient displacement capacity is provided in the isolators.
Vamvatsikos D. (2019). Decision support for road infrastructure resilience: the panoptis perspective. Proceedings of the SECED 2019 Conference, Greenwich, UK
Abstract | The PANOPTIS consortium aims to leverage existing tools and services as well as remote sensing technologies to deliver an integrated platform that can address road infrastructure (RI) multi-hazard resilience. The scope of the project incorporates RI structural components (bridges, overpasses, interchanges, tunnels, slopes, retaining walls, pavements, and surface water drains), non-structural components (tunnel ventilation systems, traffic cameras and signposts), as well as interconnected non-RI components, such as power transmission lines and telecommunication towers. Both detailed and surrogate structural models will be developed for RI and non-RI components, quantifying and incorporating the epistemic uncertainty due to the detailed models’ reduction to surrogacy to allow a rapid high-resolution assessment of vulnerability, whereby loss, functionality and downtime become directly tied to rehabilitation/emergency action planning. The focus is on the development of a rapid-response decision-support tool that will employ measured data immediately after any seismic event to issue inspection prioritization protocols, facilitate the rapid assessment of the state of the RI, and help increase its resilience to catastrophic events.
Kazantzi A.K., Vamvatsikos D., Miranda E (2019). Damping influence on the seismic demands of non-structural components and building contents. Proceedings of the 4th Panhellenic Conference on Earthquake Engineering and Engineering Seismology, Athens, Greece (in greek)
Abstract | In most seismic code provisions, the design of nonstructural elements is based on the evaluation of the (absolute) acceleration demands at the floor levels, usually assuming a critical damping of 5% for those elements. However, the actual critical damping for the nonstructural components is well known to be an unknown parameter, that could well deviate from the abovementioned value, whereas its influence remains by large an unexplored field.
To study the effect of damping on the seismic demands of nonstructural elements 113 actual seismic records obtained from instrumented buildings in the USA were selected. The study concluded that: (a) the use of damping modification factors evaluated based on ground level excitations are not suitable for correcting the nonstructural component spectral accelerations demands and (b) the component damping effect on the imposed to the nonstructural elements floor spectral demands is highly dependent on the proximity of their natural period to that of the building. On account of the above and a detailed statistical analysis two equations are proposed for estimating the mean and coefficient of variation of the component damping modification factors.
Chatzidaki A., Lyritsakis C., Vamvatsikos D., Aschheim M., Hernández-Montes E. (2019). Seismic assessment of a 4-story RC building designed on an intensity versus a performance basis. Proceedings of the 4th Panhellenic Conference on Earthquake Engineering and Engineering Seismology, Athens, Greece
Περίληψη | Τρεις μεθοδολογίες σχεδιασμού συγκρίνονται ως προς τα αποτελέσματά τους για ένα τετραώροφο κτήριο από οπλισμένο σκυρόδεμα με περιμετρικά πλαίσια ανάληψης οριζοντίων δυνάμεων. Οι δύο είναι μεθοδολογίες σχεδιασμού βάσει επιτελεστικότητας και βασίζονται στη χρήση των Φασμάτων Συχνότητας Διαρροής για να επιτύχουν με αξιοπιστία αυξημένους στόχους επιτελεστικότητας, λαμβάνοντας πλήρως υπόψη τις αβεβαιότητες και τη σεισμική επικινδυνότητα. Η τρίτη χρησιμοποιεί το Φάσμα Σημείου Διαρροής για να επιτύχει ταχεία σύγκλιση σε μια ικανοποιητική σχεδίαση που είναι συμβατή με τις σύγχρονες κανονιστικές διατάξεις. Και στις τρεις περιπτώσεις δημιουργήθηκαν τα μη γραμμικά προσομοίωματα των κτηρίων και πραγματοποιήθηκε Ικανοτική Δυναμική Ανάλυση για την εκ των υστέρων αποτίμηση της επιτυγχανόμενης σεισμικής επιτελεστικότητας. Τα αποτελέσματα δείχνουν ότι όλες οι παραπάνω μέθοδοι ικανοποιούν τις απαιτήσεις του κανονισμού, δηλαδή στόχους επιτελεστικότητας που σχετίζονται με την Προστασία Ζωής.
Ωστόσο, μόνο οι δύο μέθοδοι σχεδιασμού βάσει επιτελεστικότητας επιτρέπουν την ακριβή επίτευξη στόχων που σχετίζονται π.χ. με την προστασία έναντι κατάρρευσης ή στόχους άλλους από την Προστασία Ζωής, που ορίζονται εκ των προτέρων από το μελετητή και πηγαίνουν πέρα από τις διατάξεις του κανονισμού.
Kazantzi A.K., Vamvatsikos D. (2019). Prescriptive approaches in performance-based design? A case-study on base isolation. Proceedings of the 13th International Conference on Applications of Statistics and Probability in Civil Engineering, ICASP13, Seoul, South Korea
Abstract | The collapse performance of code-designed base-isolated structures has recently received considerable criticism, having been found to be deficient vis-à-vis conventional buildings in several situations. As a remedy, prescriptive minima with a tenuous probabilistic justification have been recommended in the literature for the bearing deformation capacity. These are independent of structure or site characteristics, yet they are already finding use in design. We put this concept to the test by means of a case study of a seismically isolated steel structure that rests on the roof of two adjacent high-rise reinforced concrete towers. To seismically isolate the steel structure, Friction Pendulum Bearings (FPBs) are used, and their displacement capacity is determined to comply with a performance objective of 1% probability of collapse in 50 years. The case study possesses two salient features that distinguish it from pertinent past investigations. The first is that the isolated steel structure rests on top of two others and consequently it is subjected to narrow-band roof acceleration time histories, shaped by the filtering of the ground motion excitation through the supporting buildings. The second is that the two supporting towers have different modal characteristics, thus displacement demands imposed to the FPBs are mainly affected by their in-phase or out-of-phase movement. Overall, a case-specific true performance-based design is shown to achieve the desired safety while requiring 1.5 times lower displacement capacities for the bearings, when compared to prescriptive “performance-based” approaches.
Spillatura A., Vamvatsikos D., Bazzurro P., Kohrangi M. (2019). Issues in harmonization of seismic performance via risk targeted spectra. Proceedings of the 13th International Conference on Applications of Statistics and Probability in Civil Engineering, ICASP13, Seoul, South Korea
Abstract | Current seismic design code provisions are mainly based on checking structural performance at a single seismic intensity associated with a pre-defined return period. For instance, in EN1998, a ground motion with 10% probability of exceedance in 50 years is used for design. This design procedure, with the inclusion of partial safety factors, is assumed to provide sufficient safety margin against earthquakes for newly designed buildings. Nevertheless, it does not specifically determine the expected seismic risk related to any performance level or limit state. Therefore, it may result in non-uniform risk for buildings located in different sites within a region (or country), even for places with identical design intensities. Instead, ASCE 7-10 incorporates Risk Targeted design maps that suggest the application of suitable spectra adjustment factors, in order to ensure a reasonably low uniform collapse risk. Making use of simplified single degree of freedom structures defined in several configurations of period and ductility, our aim is to test the effectiveness of the adjustment factors computed under different assumptions. It is shown that, although matching is not practically possible, harmonization remains a viable target, offering insights for possible future adoption of Risk Targeted Spectra in forthcoming seismic codes.
PANOPTIS Members
