State-Dependent Vulnerability Of Case-Study Reinforced Concrete Frames

This study investigates the effect of mainshock-aftershock sequences on numerical fragility and vulnerability relationships of European reinforced concrete (RC) moment-resisting frames (MRFs). A four-story, four-bay nonductile RC MRF is selected for illustrative purposes. This index building is representative of a typical vulnerability class in the Mediterranean region. The influence of the masonry infills on seismic performance is also investigated. An advanced numerical nonlinear model is developed for the case-study frame and then assessed through nonlinear dynamic analysis using both real and artificial mainshock-aftershock sequences, via a ‘sequential cloud’ approach. The obtained seismic demand estimates allow to generate fragility functions for the undamaged frame when subjected to mainshocks only. Moreover, statedependent fragility functions are derived for the mainshock-damaged frame when subsequently subjected to aftershocks. Damage-to-loss models, specifically calibrated on Italian post-earthquake data, are used to derive vulnerability functions for this case-study structure. Preliminary results from the study show that the frame experiences severe damages states and high losses for a range of ground-motion shaking intensities, with a clear damage increase due to aftershocks. An attempt to generate vector-valued mainshock-aftershock vulnerability relationships is finally presented. The proposed vulnerability surfaces can be more easily implemented into a time-dependent risk assessment framework

Mapping performance-targeted retrofitting to seismic fragility reduction

This study investigates the improvement in the seismic performance of an archetype reinforced concrete (RC) frame due to varying structural retrofit levels. Specifically, the study attempts to map the increase of the displacement-based global ratio between capacity and life-safety demand (CDRLS) to the reduction of seismic fragility. Such a reduction is characterized by the shift of the median fragility for different structure-specific damage states (DSs). The considered structure does not conform to modern seismic design requirements, and it is retrofitted using various techniques. Advanced nonlinear models are developed for the archetype frame, accounting for potential failure mechanisms, including flexural, joint, and shear failure. Three common retrofitting techniques are investigated, namely RC jacketing, steel jacketing, and fiber-reinforced polymers (FRP) wrapping of columns and joints. Each technique is specifically designed and proportioned to achieve predefined performance objectives (i.e., performance-targeted retrofitting), thus generating many retrofit alternatives. The improvement in seismic performance for the retrofitted frames is first characterized by computing the global CDRLS, which can be obtained using nonlinear pushover analysis combined with the Capacity Spectrum Method. Subsequently, cloud-based nonlinear time-history analyses are performed to derive fragility relationships for the as-built and retrofitted configurations, monitoring the variation in the median fragility for all DSs. Finally, the global CDRLS increase due to retrofitting is correlated with the corresponding shift in the median fragility. A linear trend is found, and it is used accordingly to develop simple models that engineers can implement to provide reasonable estimates for such shift once the global CDRLS is known

Calibration of Damage-to-loss Ratios for a Case-study Structure

This study illustrates a simulation-based procedure for calibrating structure-specific damage-to-loss ratios (DLRs), which link the earthquake-induced global damage states (DSs) of a structure with the resulting loss ratios (repair costs normalized by replacement costs). A non-ductile reinforced-concrete frame representative of those built in Italy before the 1970s is selected as a case study. An advanced numerical non-linear model is developed to simulate its dynamic response and failure modes, including flexure, shear, and joint mechanisms. The calibration procedure starts by defining structure-specific DSs describing the increasing structural/nonstructural damage levels and their story-drift thresholds using pushover analysis. Building-level fragility functions are subsequently developed to quantify the probabilities of exceeding each DS given any ground-shaking intensity level. Component-based seismic loss assessment is then performed following the FEMA P-58 approach, which adopts simulation to quantify such losses at multiple ground-shaking intensities. Next, each DLR is statistically characterized by fitting a beta distribution to the component-based loss results upon being conditioned on the corresponding global DS. It is finally shown that the simplified losses obtained by combining the derived DLRs with the building-level fragility functions are highly consistent with their component-based counterparts. This indicates that such DLRs can be easily utilized in seismic risk assessment, particularly for building portfolios, offering a trade-off between accuracy and computational time/effort

Assessing Environmental Impacts of Earthquake-Induced-Damage for an Italian Case-study Building

This study assesses environmental impacts due to the repair of earthquake-induced damage considering an old reinforced concrete (RC) frame representative of those built in Italy before the 1970s. Such impacts, expressed in terms of embodied carbon, represent a considerable component of buildingsﾒ life-cycle embodied carbon in seismically-prone regions. Embodied carbon is the term for greenhouse gas emissions associated with manufacturing and using a product/service. In the case of materials for building repairs, this includes extraction, manufacturing, transporting, construction, maintenance, and disposal. The seismic damage sustained by the case-study frame is first evaluated using the FEMA P-58 methodology. Specifically, the frameﾒs nonlinear response is analysed against increasing ground-shaking intensities, followed by estimating the damage incurred by its individual components via ad-hoc fragility models. Damage is then converted to embodied carbon by calibrating consequence models specifically developed for Italian structural and non-structural building components. This is accomplished by: 1) collecting environmental-impact data from Italian manufacturers of relevant construction materials and; 2) defining suitable structure-specific damage levels and the required repair work for every component. Results show that the embodied carbon induced by seismic damage throughout the case-study buildingﾒs life cycle might exceed 25% of that generated during its initial construction (pre-use phase)

Assessing the potential implementation of earthquake early warning for schools in the Patras region, Greece

Earthquake early warning (EEW) is currently deemed a credible approach to seismic resilience enhancement in modern societies, especially if part of a more holistic earthquake mitigation strategy involving other risk reduction tools such as structural upgrading/retrofit. Yet, there remains a strong need to 1) assess the feasibility of EEW in various seismotectonic contexts, considering specific target applications/end users; and 2) develop next-generation decision-support systems relying on interpretable probabilistic impact-based estimates toward more risk-informed decision-making on EEW installation/alert triggering. These challenges are addressed in this paper, which showcases a series of recent significant EEW contributions by the authors. First, we present the results of a state-of-the-art feasibility study for EEW in schools performed across the Patras region of Greece, attempting to spatially combine traditional seismologically-driven EEW decision criteria (i.e., warning time) with proxy risk-oriented measures for earthquake impact (i.e., building fragility and the number of exposed school students). These results show that, under certain conditions, EEW could be effective for the schools in the considered case-study region. We then demonstrate an advanced end-user-centred approach for improved risk-informed decision-making on triggering EEW alerts. The proposed methodology integrates earthquake-engineering-related seismic performance assessment procedures and metrics with multi-criteria decision-making (MCDM) within an end-to-end probabilistic framework. The performance-based earthquake engineering component of such a framework facilitates the computation of various damage/loss estimates (e.g., repair cost, downtime, and casualties) by combining target-structure-specific models of seismic response, fragility, and vulnerability with real-time ground-shaking estimates. Additionally, the incorporated MCDM methodology enables explicit consideration of end-user preferences (importance) towards the estimated consequences in the context of alert issuance. The developed approach is demonstrated using an archetype school building for the case-study region, for which we specifically investigate the optimal decision (i.e., “trigger” or “don't trigger” an EEW alert) across a range of ground-motion intensity measures. We find that the best action for a given level of ground shaking can vary as a function of stakeholder preferences

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Vulnerability of Case-Study Reinforced Concrete Frames to Mainshock-Aftershock Sequences

This study investigates the effect of mainshock-aftershock sequences on numerical fragility and vulnerability relationships of European reinforced concrete (RC) moment-resisting frames (MRFs). A four-storey, four-bay nonductile RC MRF is selected for illustrative purposes. This index building is representative of a typical vulnerability class in the Mediterranean region. The influence of the masonry infills on seismic performance is also investigated. An advanced numerical nonlinear model is developed for the case-study frame and then assessed through nonlinear dynamic analysis using both real and artificial mainshock-aftershock sequences, via a ‘sequential cloud’ approach. The obtained seismic demand estimates allow to generate fragility functions for the undamaged frame when subjected to mainshocks only. Moreover, statedependent fragility functions are derived for the mainshock-damaged frame when subsequently subjected to aftershocks. Damage-to-loss models, specifically calibrated on Italian postearthquake data, are used to derive vulnerability functions for this case-study structure. Preliminary results from the study show that the frame experiences severe damages and high losses for a range of ground-motion shaking intensities, with a clear damage increase due to aftershocks. An attempt to generate vector-valued mainshock-aftershock vulnerability relationships is finally presented. The proposed vulnerability surfaces can be more easily implemented into a time-dependent risk assessment framework

Effects of ground-motion sequences on fragility and vulnerability of case-study reinforced concrete frames

This study investigates the efects of ground-motion sequences on fragility and vulnerability of reinforced concrete (RC) moment-resisting frames (MRFs). Two four-storey, fourbay RC MRFs are selected as case studies. These structures, which share the same geometry, are representative of distinct vulnerability classes in the Mediterranean region and are characterized by diferent material properties, cross-section dimensions, and detailing. The frst case study is a ductile MRF designed according to Eurocode 8 (i.e., a special-code frame), while the second is a non-ductile MRF designed to sustain only gravity loads (i.e., a pre-code frame). The infuence of masonry inflls on their seismic performance is also investigated. Advanced numerical models are developed to perform cloud-based sequential nonlinear time history analyses using ground-motion sequences assembled by randomly pairing two real records via Latin hypercube sampling. Diferent structure-specifc damage states are considered to derive fragility curves for the undamaged structures, when subjected to a single ground-motion record, and state-dependent fragility curves by considering the additional damage induced by a second ground-motion record within the sequence. Damage-to-loss models are then used to derive mean vulnerability relationships. Results of the analysis show the importance of considering the efect of damage accumulation in the pre-code frames. Moreover, the presence of inflls shows an overall positive contribution to the seismic performance of both frame types. Vector-valued vulnerability relationships accounting for the damaging efect of two ground-motion records are fnally presented in the form of mean vulnerability surfaces