Life-Cycle Environmental Impacts of Seismic Retrofit Measures: a Case Study on Reinforced Concrete Jacketing in Italy

The increasing awareness of building sustainability in earthquake-prone areas constitutes a motive for investigating the influence of common seismic risk mitigation measures, such as structural retrofit, from a life-cycle environmental perspective. Accordingly, this study sheds light on the effects of reinforced concrete (RC) jacketing, a common retrofit strategy, on the life-cycle environmental impacts generated throughout the service life of a non-ductile RC frame constructed in Italy before the 1970s. Various layouts and configurations of retrofit configurations are developed to represent different design choices. The environmental impacts are expressed in terms of embodied carbon, a parameter that measures the overall greenhouse gas emissions associated with the life stages of a system (e.g., manufacturing, construction, maintenance, disposal). The lifecycle embodied carbon includes the earthquake-induced emissions evaluated by characterising the seismic damage sustained by the structure and then converting it to embodied carbon using suitable consequence models. The other life-cycle component is the embodied carbon of retrofit intervention, for which a simplified expression that relies on the retrofit layout and geometric features is derived. Results show that the life-cycle embodied carbon of the as-built structure constitutes 70% of that related to initial construction. The use of RC jacketing could reduce this percentage to as low as 43%

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

A fragility-oriented approach for seismic retrofit design

This study proposes a practical fragility-oriented approach for the seismic retrofit design of case-study structures. This approach relies on mapping the increase of the global displacement-based ratio of capacity to life-safety demand ( CDRLS) to the building-level fragility reduction. Specifically, the increase of CDRLS due to retrofitting is correlated with the corresponding shift in the fragility median values of multiple structure-specific damage states, observing that a pseudo-linear trend is appropriate under certain conditions. Accordingly, a practical approach is proposed to fit such a (structure-specific) linear trend and then use it by first specifying the desired fragility median and subsequently finding the corresponding target value of CDRLS that must be achieved through retrofit design. The validity of the proposed approach is illustrated for an archetype reinforced concrete (RC) structure not conforming to modern seismic design requirements, which has been retrofitted using various techniques, namely, fiber-reinforced polymers wrapping of columns and joints, RC jacketing, and steel jacketing

Simulation-based consequence models of seismic direct loss and repair time for archetype reinforced concrete frames

Seismic risk management of building portfolios requires a reliable evaluation of earthquake-induced losses. This is commonly performed using consequence models linking structure-specific damage states (DSs) experienced by a building to a given loss metric (or decision variable). This study demonstrates a simulation-based procedure that derives refined probabilistic consequence models considering two essential loss metrics: direct-loss and repair-time ratios (repair cost or time normalised by the corresponding reconstruction values). Nine case-study reinforced concrete frames with various heights and design-code levels are developed to represent common residential buildings in Italy and the Mediterranean region. The proposed procedure starts by defining building-level, structure-specific DSs that reflect the increasing structural and nonstructural damage for the nine frames. Their seismic response is then assessed by analysing two-dimensional nonlinear numerical models and deriving building-level fragility relationships. Next, component-based direct-loss and repair-time analysis is conducted via the FEMA P-58 methodology, which computes such metrics at multiple ground-shaking intensities using Monte Carlo sampling. The consequence models are finally characterised by fitting probabilistic distributions to the direct-loss and repair-time realisations after conditioning them on the respective global DSs sustained by each case-study frame. This procedure enables deriving enhanced consequence models that can be easily implemented in risk analysis of building portfolios to obtain quick loss estimates. This study finally sheds some light on the possibility of correlating repair time to direct loss, which might be useful in estimating indirect losses resulting from downtime, particularly in cases where repair-time data or models are unavailable

Environmental impacts of seismic damage for a case-study reinforced RC building in Italy

This study evaluates the environmental impacts resulting from the repair of earthquakeinduced damage, considering an older 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’ life-cycle embodied carbon in seismically-prone regions. Embodied carbon is a metric that measures the total greenhouse gas emissions associated with material extraction, manufacturing, transporting, construction, maintenance, and disposal. The seismic damage sustained by the case-study frame is first evaluated using the FEMA P-58 approach. Specifically, the frame’s nonlinear response is analysed against increasing groundshaking intensities, followed by estimating the damage incurred by its individual components via ad-hoc fragility models. Damage is then converted to embodied carbon by using consequence models specifically derived in this study for Italian structural/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’s life cycle might exceed 25% of that generated during its initial construction (pre-use phase)

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

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

A mixed-mode data collection approach for building inventory development: Application to school buildings in Central Sulawesi, Indonesia

Urban disaster risk management and reduction requires the development and periodic updating of regional building inventories. However, the development of such inventories can be very cost-intensive and time-consuming, making this a challenging task, particularly for low- and middle-income countries. This article discusses a mixed-mode building inventory data collection framework using a rapid and cost-effective remote survey technique that can be deployed in various geographic contexts. A key component of the proposed approach is an inter-rater reliability analysis of data collected from traditional sidewalk surveys and remote surveys for a small subset of buildings in the considered building portfolio, which is used to assess the suitability of the remote survey for the location(s) considered. The framework is demonstrated by developing a regional database of school buildings in the Central Sulawesi region of Indonesia. The database consists of 2536 school buildings from 454 elementary and high schools in the Palu, Sigi, and Donggala regions, susceptible to earthquake-induced ground shaking, tsunami, liquefaction, and landslides. The developed database can be used in pre-event/long-term risk analysis and management, post-event/near-real-time loss estimation, and regional-level decision-making on school assets and related policies. The database has been made available for public use and can be readily harmonized with similar databases for other regions