Archetypal telemetry and decision support system for the protection of monumental structures
The project proposes the development of an intelligent platform for remotely monitoring monumental structures, promptly diagnosing their potential for instability and making subsequent decisions on taking remedial actions. It is a timely proposal that is developed in cooperation with the Ministry of Culture to protect the entirety of the monumental structures in Greece, through the accurate diagnosis and the assessment of the estimated micro-climatic and atmospheric stressors. HYPERION will perform combined prioritization of rehabilitation needs, aiming to optimize the distribution of available funds. For this purpose, two discrete levels of system deployment are offered. The first requires minimal resources and involves the use of software for risk assessment under multiple environmental hazards (earthquake, wind, flood, deterioration, ageing). It employs probabilistic methods and models to estimate the risk of instability and offers some remote monitoring capabilities through local or regional measuring of the intensity of environmental actions. At the second level, a sensor network is deployed at the monument and connected to the remote monitoring platform, offering continuous up-to-date information to optimize the accuracy of instability prediction via the risk assessment software.
The platform will be validated via its pilot application to two emblematic monuments of Classical Antiquity: a) the Horologion of Andronikos Kyrrhestes (Tower of the Winds) in the Roman Forum of Athens and b) the Temple of (Athena) Aphaea in Aegina Island. The exploitation of the platform is expected to offer considerable direct and indirect benefits, both for the research and industrial partners, as well as for the Agencies of the Ministry of Culture and the Greek state.
Project Funding
EPAnEK 2014-2020 Operational Programme Competitiveness-Entrepreneurship-Innovation
ESPA 2014-2020, Greek Ministry of Education and Religious Affairs/MIA-RTDI
T1EΔK-00956
Collaborators
Engineering Firm AETMON
National Technical University of Athens
iTEAM
Engineering Firm DOMOS
Ancient Monument Restoration Agency of the Ministry of Culture
Time Period
Oct 2018 – Jan 2023
Relevant Publications
Melissianos V.E., Lachanas C.G., Lignos X.A., Vamvatsikos D., Chatzidaki A., Dasiou M-E., Manetas A. (2024). A Holistic Platform For The Seismic Risk Assessment Of Ancient Monuments. Proceedings of the 18th World Conference on Earthquake Engineering, Milan, Italy.
Abstract | The protection of cultural heritage against natural hazards and in particular earthquakes is a critical and challenging task because authorities try to tackle the steady onslaught of extreme seismic events and continuous deterioration of the structure. Countries around the Mediterranean Sea have a portfolio of monuments, some of which are in relatively poor condition and in danger of sustaining non-recoverable damage due to earthquake events. Protecting these monuments becomes more daunting within budget limitations. In this framework, a holistic platform for the seismic risk assessment of ancient monuments has been developed within the EU-Greece funded research project ARCHYTAS to serve as a decision-support tool to assist the prioritization and restoration actions before a seismic event happens or in a post-event environment, providing a rapid assessment of the monument structural status for the given event. The overall system is presented indicatively for the Aphaia Temple in Aegina island, Greece.
[paper]
Dasiou M-E., Lachanas C.G., Melissianos V.E., Vamvatsikos D. (2024). Seismic performance of the temple of Aphaia in Aegina island, Greece. Earthquake Engineering and Structural Dynamics, 53(2):573-592
Abstract | The seismic performance assessment of the ancient Temple of Aphaia in Aegina island, Greece, is presented. The Temple of Aphaia was erected around 500BC using porous limestone and is one of the most characteristic examples of Doric architecture. The assessment is performed within a performance-based framework using state-of-the-art tools of earthquake engineering. In the first part, the seismic hazard of the site was calculated using the European Seismic Hazard Model and hazard-consistent records were selected. Then, the Temple was scanned by drone and the point cloud was used to develop the numerical structural model. The Temple was analyzed using the discrete element method. Appropriate engineering demand parameters and limit state thresholds were defined. Fragility curves for the structural elements, namely, columns and architraves, of the Temple were computed via multi-stripe analysis. Finally, the seismic risk of the Temple was evaluated using long-term estimates in terms of return periods of exceeding limit states and total loss. The outcomes of the study offer valuable information to engineers, architects, and archaeologists regarding the current status of the monument in terms of identifying its most vulnerable elements and allowing the prioritization of short- and long-term restoration actions.
Lachanas C.G., Vamvatsikos D., Dimitrakopoulos E.G. (2023). Intensity measures as interfacing variables versus response proxies: The case of rigid rocking blocks. Earthquake Engineering and Structural Dynamics, 52(6):1722-1739.
Abstract |A comparative study of alternative Intensity Measures (IMs) for structures of rocking response is presented, focusing on the salient characteristics that define the selection of an optimal IM for the problem at hand. An IM may play the role of an interfacing variable, linking hazard with fragility/vulnerability for the risk assessment of structures, or it may only be employed as a proxy for predicting structural response under a given ground motion. In the first case, low conditional variability (high efficiency) and low conditional dependence on seismological parameters (high sufficiency) are needed. For response proxy usage, one may place more importance on the predictive capability of the IM within a simple regression model, favoring high correlation and low fitting errors over an extended range of response. The results showcased that (i) the peak ground acceleration and peak ground velocity, tend to be highly efficient and sufficient in specific regions of rocking response, that is, onset of rocking and overturning, respectively, but not necessarily everywhere; (ii) the average spectral acceleration shows a more consistent performance at the cost of requiring the definition of a proper period range; (iii) magnitude sufficiency is generally more difficult to achieve, compared to the distance from the rupture, and (iv) IMs that may be unsuitable for risk and vulnerability assessment, can still be highly effective as response predictors in statistical models.
Lachanas C.G., Vamvatsikos D., Dimitrakopoulos E.G. (2022). Statistical property parameterization of simple rocking block response. Earthquake Engineering and Structural Dynamics, 52(2):394-414.
Abstract | The parametric representation of rocking fragilities is statistically investigated. Initially, the potential normalization of the rocking parameters to reduce the problem’s dimensionality is tackled by undertaking comparisons both on a single-record and a sample-of-records basis. It is found that the slenderness angle can be normalized out when probabilistically considering the rocking response of simple rocking blocks with the same semi-diagonal length. Then, the robustness of the lognormal distribution for characterizing the rocking motion is investigated. Sets of pulse-like and ordinary ground motions are employed to test the lognormal fit for the full range of rocking response when the peak ground acceleration or the peak ground velocity are employed as intensity measures. In both cases, the lognormal distribution offers an adequate, but often imperfect, baseline model of the rocking fragility curves. Instead, a shifted lognormal that accounts for the absence of response below the rocking initiation intensity is an enhanced solution that can form the basis for offering simplified response model surrogates.
Kazantzi A.K., Lachanas C.G., Vamvatsikos D. (2022). Normalized response distribution expressions for ground-supported rigid rocking bodies. Proceedings of the 3rd International Conference on Natural Hazards & Infrastructure ICONHIC 2022, Athens, Greece.
Abstract | Estimating the seismic response of ground-supported rocking rigid blocks, is a topic that has attracted significant research interest in the past few decades, since it concerns, among others: (a) several modern structures or ancient monolithic columns that utilize rocking as a seismic protection mechanism and (b) numerous free-standing contents (e.g. museum artefacts) located on the ground floor or lower floors of stiff buildings. In the present research work, by means of a parametric study, utilizing two-dimensional rectangular blocks of varying sizes and ordinary earthquake records, the rocking response at increasing intensity levels was assessed through Incremental Dynamic Analyses. Following the demand evaluation and in order to allow for an easier utilization of the findings in practical applications, simplified approximate equations have been obtained via nonlinear regression analysis. The proposed equations provide an estimate of the peak rocking response distribution, expressed in terms of the normalized, to the dimensionless slenderness angle , peak rocking angle, at increasing ground motion intensity levels.
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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.
[paper]
Kazantzi A.K., Lachanas C.G., Vamvatsikos D. (2022). Seismic response distribution expressions for rocking building contents under ordinary ground motions. Bulletin of Earthquake Engineering, 20: 6659–6682.
Abstract | Analytical expressions are proposed for predicting the rocking response of rigid free-standing building contents subjected to seismic-induced floor excitations. The study considers a wide range of rigid block geometries and seismic floor acceleration histories that were recorded during actual earthquakes in instrumented Californian buildings, so as to cover, in a fully probabilistic manner, the entire spectrum of potential pure rocking responses, i.e. from the initiation of rocking up to the block overturning. Contrary to past observations on anchored building contents (prior to any failure in their anchorage system that could alter their response and mode of failure), it is shown that the response of free-standing blocks is not influenced by the predominant period of the supporting structure. The proposed set of equations can be utilised for estimating the response statistics and consequently for undertaking an analytical seismic fragility assessment on rocking building contents.
[pre-print version]
Lachanas C.G., Vamvatsikos D., Vassiliou M.F. (2022). The influence of the vertical component of ground motion on the probabilistic treatment of the rocking response of free-standing blocks. Earthquake Engineering and Structural Dynamics. 51(8): 1874-1894.
Abstract | The influence of the vertical component of ground motion is investigated for assessing the distribution of the seismic response of unanchored rigid blocks. Multiple stripes of site-hazard-consistent ground motions are employed for calculating the seismic response of rigid rocking blocks with and without the inclusion of the vertical component. The comparison of the resulting response is being made both for single records and full suites, employing a paired record versus an ensemble-statistics comparison, respectively. It is shown that on a single record basis, the vertical component may have a non-negligible but highly variable influence on the rocking response, sometimes detrimental, sometimes beneficial. Still, when considering any large ensemble of records, the effect becomes statistically insignificant, except for the very specific case of rocking uplift for stocky blocks. To this end, for cases where the appearance of uplift is associated with damage, closed-form expressions are proposed to modify the lognormal fragility function of rocking initiation given the block slenderness and the ratio of the peak vertical over the peak horizontal ground acceleration.
[pre-print version]
Lachanas C.G., Vamvatsikos D. (2022). Rocking incremental dynamic analysis. Earthquake Engineering and Structural Dynamics, 51(3):688-703.
Abstract | The seismic response assessment of rocking systems via Incremental Dynamic Analysis (IDA) is investigated, focusing on the issues that arise in the analysis and postprocessing stages. Rocking IDA curves generally differ from those of hysteretic structural systems due to (i) the frequent appearance of resurrections; (ii) their highly weaving non-monotonic behavior; and (iii) their overall high variability. Hence, including or ignoring analysis results above the first resurrection level, deriving statistics given a response level versus an intensity measure level, as well as selecting an adequate number of ground motion records and runs per record, become challenging issues with non-trivial impact on the probabilistic characterization of rocking response. This necessitates a fresh view on analysis choices and post-processing techniques, aiming to assure the accuracy and fidelity of rocking IDA results. As an example, the effect of different choices and techniques are showcased on two-dimensional rigid blocks that are assumed to represent simplified models of monolithic ancient columns of different slenderness.
Vamvatsikos, D., Fragiadakis, M., Georgopoulos, I.-O., Koumousis, V. K., Koutsoyiannis, S., Manetas, A. Melissianos, V. E., Papadopoulos, C., Papanikolopoulos, K. E., Toumpakari, E.-E. (2021). The ARCHYTAS intelligent decision-support system for the protection of monumental structures. Proceedings of the 4th International Conference on Protection of Historical Constructions (PROHITECH 2020), Athens, Greece
Abstract | The ARCHYTAS platform is based on using (i) reliable mechanical models and damage thresholds for assessing structural performance (ii) a network of sensors for updating the model parameters, (iii) detailed estimates of earthquake and flood hazard at the sites of interest and (iv) a state-of-art approach for multi-hazard risk assessment that can deliver accurate pre/trans/post-event evaluation of the risk at multiple geographically distributed cultural heritage sites. The core of the proposed system comprises a cloud-deployed computational platform, where data obtained from on-site measuring systems is processed, critical environmental actions are identified and flags are raised to provide alerts on the predicted monument structural condition. The decision-support system is fully uncertainty-aware, employing the concept of the mean annual frequency of limit-state exceedance under specified confidence levels to offer monument-specific courses of action based on the convolution of the current state of the monument (as determined by its best-estimate fragility, and updated by current or past measurements) and the predicted, recorded or evolving hazard. All-in-all, the platform can assist the relevant authorities to prioritize inspection, maintenance and rehabilitation actions be-fore or after events subject to limited available resources.
Lachanas, C. G., Melissianos, V. E., and Vamvatsikos, D. (2021). Spatial variability of ground motion hazard and preliminary regional damage assessment of ancient monuments. Proceedings of the 4th International Conference on Protection of Historical Constructions (PROHITECH 2020), Athens, Greece
Abstract | The seismic hazard is a spatial variable and its distribution depends on the site and soil conditions, the distance from the influencing faults, their geometric characteristics etc. To characterize a future seismic event, multiple correlated Intensity Measure (IM) fields are employed. In Greece and especially in the Attica region, there are numerous monuments of classical antiquity that are spread throughout the territory, e.g., the Temple of Poseidon in Sounio, the Ancient Walls of Piraeus etc., and not only in the center of the city of Athens, where the well-known Parthenon, the Temple of Olympian Zeus, etc. lie. To capture the ensemble risk of such widely distributed antiquities a regional risk assessment approach is adopted, based on the principles of the Performance-Based Earthquake Engineering. Event-Based Probabilistic Seismic Hazard Analysis (PSHA) is used as basis, where the distribution of the ΙΜ fields is evaluated for a stochastic event set, spanning thou-sands of realizations, allowing the estimation of damages over an entire region on an event-by-event basis. A basic application is offered by considering a typical single multi-drum column at each site of interest to assess its performance. Different fragility representation schemes are employed, and their consequences are compared for both the event-based and the classical approach of PSHA as a first decisive step towards the formulation of a comprehensive methodology for the assessment of seismic damages of ancient monuments within a region.
Melissianos, V. E., Lachanas, C. G., and Vamvatsikos, D. (2021). Preliminary seismic risk assessment of monolithic columns of the Aphaia Temple in Aegina. Proceedings of the 4th International Conference on Protection of Historical Constructions (PROHITECH 2020), Athens, Greece
Abstract | Studies on the seismic assessment of monumental structures of antiquity are mostly focused on the estimation of the structural behavior and do not involve the pertinent uncertainties. Towards filling this research gap, a preliminary seismic risk assessment of monolithic columns of the Aphaia Temple in Aegina island, Greece, is presented. A comprehensive application of the framework of Performance-Based Earthquake Engineering is carried out. Site-specific seismic hazard estimation is performed at first by employing Probabilistic Seismic Hazard Analysis. The rocking column is analyzed under seismic excitation by numerically solving the equation of motion in order to extract the fragility curves. Finally, the convolving of seismic hazard and structural response yields the seismic risk of the column that is used to estimate the mean annual rate of exceeding predefined limit states that are associated with damage and collapse of the column.
Melissianos V.E., Dasiou M.E., Vamvatsikos D. (2021). Seismic risk assessment of the ancient temple of Aphaia in Greece. Proceedings of the 17th World Conference on Earthquake Engineering (17WCEE), Sendai, Japan
Abstract | The protection of cultural heritage against natural hazards has attracted significant research efforts and funding during the last decades, recognizing its importance in humanity’s history and raising public awareness on this issue. In Greece, there are numerous monuments that have been exposed to environmental actions, and, consequently, many are classified as deteriorating structures. In addition, earthquakes pose a significant threat to their structural integrity and contribute to the accumulation of damage. The evaluation of the seismic performance of such heritage assets is a complex computational problem, especially as their structural elements are either not rigidly connected, or connected by weak mortar, and thus prone to rocking due to the seismic excitation.
Research on the seismic assessment of monuments is quite limited to the estimation of the structural behavior, thus excluding the incorporation of pertinent uncertainties. The aim of the study is to contribute to the seismic risk assessment of monuments. The framework of Performance-Based Earthquake Engineering is applied, comprising of four successive and interconnected steps: (1) the European seismic source model is used to estimate the seismic hazard in terms of a scalar intensity measure, (2) the structure is modeled with a discrete element approach. The rocking and/or sliding of the individual stone blocks are accurately addressed by the software since, during the calculation, it locates each contact and computes the motion of each block from the forces that are developed at the joints. Results in terms of maximum displacements are obtained from the analysis and related to damage states. (3) The limit-state and the aleatory and epistemic uncertainties are defined for the determination of discrete damage states and the associated fragility curves, and (4) the seismic risk is calculated in terms of the mean annual frequency of exceeding each limit state. The aforementioned methodology is applied to a free-standing column and a colonnade of two columns with an architrave at the ancient Temple of Aphaia, located on the Greek island of Aegina and built between 510 and 470 BC, comprising a significant example of the Archaic architecture.
Karaferis N., Vamvatsikos D. (2021). Seismic action combination rules for the design of azimuth-independent structures. Proceedings of the 8th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering COMPDYN2021, Athens, Greece
Abstract | The validity of the typical 100/30 combination rule for horizontal seismic action effects is investigated for the design of structures that are axially symmetric along the vertical direction. The 100/30 rule stipulates that one should combine 100% of the seismic action in one principal direction (as estimated by the design spectrum) with 30% of the action in the other principal direction, and vice-versa. Having been derived for azimuth-dependent structures, having e.g., a rectangular plan, it takes advantage of the fact that the two horizontal components of ground motion are only partially correlated, with peaks that in general do not happen simultaneously, to reduce the overall design loads. On the contrary, vertical liquid storage tanks, silos and chimneys are examples of azimuth-independent structures, which by virtue of their symmetry will always experience the worst-possible incidence angle of a ground motion. To quantify the effect of axisymmetry we employed a database of 150 records with three components of ground motion. The results show that an 106/106 combination rule, or more accurately a 1.12 amplification factor on the design spectrum in a single direction, rather than the 1.04 implied by the 100/30, is adequate to account for the effects of axisymmetry. Still, this value depends on the definition of the underlying design spectrum, and whether, e.g., the maximum, arbitrary or geometric mean component is employed, which should be accounted for in all calculations.
Kazantzi A.K., Lachanas C.G., Vamvatsikos D. (2021). Seismic response distribution expressions for on-ground rigid rocking blocks under ordinary ground motions. Earthquake Engineering and Structural Dynamics, 50(12):3311-3331.
Abstract | Predictive relationships are offered for the response of on-ground 2D rigid blocks undergoing rocking. Among others, this is pertinent to (1) modern or classical antiquity structures that utilize rocking as a seismic protection mechanism and (2) freestanding contents (e.g., cabinets, bookcases, and museum artifacts) located on the ground or lower floors of stiff buildings. Blocks of varying dimensions were subjected to a full range assessment of seismic response under increasing intensity levels of ordinary (no-pulse and no-long-duration) ground motions, parameterized by peak ground acceleration or velocity. Both response and intensity were normalized, allowing the fitting of general-purpose parametric expressions to determine the mean and dispersion of response for an arbitrary block of interest. These can be utilized in the same way as conventional strength-ratio/ductility/period relationships of yielding oscillators, to enable the rapid assessment or design of simple rocking systems.
ARCHYTAS Members
