The seismic vulnerability assessment of monumental buildings is a complex task. Several uncertainties mine the reliability of evaluations. Within historical buildings, churches appear as particularly vulnerable objects, prone to instabilities and collapse when undergoing seismic loads. Global and local collapse mechanisms related to in plane and out-of-plane response of walls, respectively, are commonly observed in existing masonry buildings subjected to a seismic event. The main cause is the lack of strong connections among orthogonal walls and between walls and floors, which does not allow a global box-type behaviour of the building. This paper shows an approach to evaluate the vulnerability of churches based on a three-step analysis with increasing detail. The first step is a large-scale analysis to be applied to sets of churches, based on a simplified form comparing 28 mechanisms that can be activated by seismic events. The second step is referred to the evaluation of single churches and related, based on a kinematic approach, to the possibility to have out-of-plane mechanisms. The third step is based on the results of numerical models. It is useful to evaluate the behaviour in detail of some macroelements and to validate the obtained results in the first two steps.

Understanding seismic risk at both the national and sub-national level is essential for devising effective strategies and interventions aimed at its mitigation. The Earthquake Risk Model of Switzerland (ERM-CH23), released in early 2023, is the culmination of a multidisciplinary effort aiming to achieve for the first time a comprehensive assessment of the potential consequences of earthquakes on the Swiss building stock and population. Having been developed as a national model, ERM-CH23 relies on very high-resolution site-amplification and building exposure datasets, which distinguishes it from most regional models to date. Several loss types are evaluated, ranging from structural–nonstructural and content economic losses to human losses, such as deaths, injuries, and displaced population. In this paper, we offer a snapshot of ERM-CH23, summarize key details on the development of its components, highlight important results, and provide comparisons with other models.

This paper describes the methodology, related steps and results of a research project on the seismic vulnerability assessment for configurations of radiation shielding blocks.The project was mainly carried out in the decade 2012-2022, with the collaboration of several research institutions (i.e., LMGC, EPFL, EUCENTRE and Caltech).First, the research was oriented to calibrate discrete element software for the dynamic behaviour simulations of blocks' configurations by means of full-scale experimental tests.In a second stage, a methodology based on the Incremental Dynamic Analysis (IDA) for the seismic risk assessment was developed.The paper presents also the results of the application of such a methodology to a real case study at CERN.

Various papers have presented different methods for computations of mechanics and kinematics of discrete structural systems. However, little has been done in comparing and benchmarking the seismic response from two different discrete-system-models with experiments. This paper presents a detailed seismic performance comparison between two models-level set discrete element method (LS-DEM) and Logiciel de Mecanique Gerant le Contact (LMGC90), calibrated with shake table experiments conducted on four concrete-block configurations. Theories of both models are thoroughly explained and compared. The simulation results are benchmarked against experimental data. Finally, the principal results and significance of this benchmarking effort is discussed.

Natural disasters, such as earthquakes, have always represented a danger to human life. Seismic risk assessment consists of the evaluation of existing buildings and their expected response in case of an earthquake; the exposure model of buildings plays a key role in risk calculations. With this respect, in recent years, advanced techniques have been developed to speed up and automatize the processes of data acquisition to data interpretation, although it is worth mentioning that the visual survey is essential to train and validate Machine Learning (ML) methods. In the present study, the identification of building types is conducted by exploiting the traditional visual survey to implement a Deep Learning (DL) classification model. As a first step, city mapping schemes are obtained by classifying buildings according to the main features (i.e., construction period and height classes). Then, Random Forest (RF), a supervised learning algorithm, is applied to classify different building types by exploiting all their attributes. The RF model is trained and tested on the cities of Neuchatel and Yverdon-Les-Bains. The decent accuracy of the results encourages the application of the method to different cities, with proper adjustments in datasets, features and algorithms.

An efficient implementation of the capacity design requires high ductility combined with a low overstrength of the critical regions. Conventional timber connections do not generally offer such ideal combination, resulting in modest behaviour and relatively high overstrength factors. Inspired by the Buckling Restrained Brace a new hold-down has been developed where the timber wall directly acts as a casing. The new hold-down has been given an adaptive stiffness allowing the structure to be stiff in the wind, while becoming more flexible in the case of an earthquake. Furthermore, local crushing of the timber members is completely avoided, and the new hold-down could be replaced after an earthquake. Experimental investigations were performed on hold-down specimens. The results show ultimate displacement values v u,c of more than 30 mm in a cyclic test according to EN12512. Eleven Cross Laminated Timber shear walls, in which the new hold-down has been implemented, were tested following monotonic and static-cyclic tests procedures, with and without vertical load. A very high ductility has been achieved with almost no strength degradation, little pinching and limited overstrength.

This paper provides a simplified tool for preliminary seismic assessment of the out-of-plane behavior of non-structural walls, such as unreinforced masonry partition walls, based on non-linear time-history analyses. The studies are performed using equivalent single-degree-of-freedom systems and trilinear hysteretic models. The out-of-plane stability is investigated through statistical assessment of computed non-linear displacement demand related to spectrum-compatible ground motions. The trilinear model developed by Doherty and Griffith is used in the investigations. This hysteretic model is based on a rigid body behavior assumption and its accuracy was extensively validated using experimental results. Four sets of 12 recorded earthquakes, slightly modified to match design response spectra of different soil conditions, were used as ground motions for the non-linear time-history analyses. Non-structural walls located at the ground level as well as in the upper floors were also examined. The obtained results show that the static stability criterion provides an accurate estimate of the seismic resistance of non-structural rocking walls (i.e., vertical cantilevers with rigid body behavior). According to that criterion the ground acceleration threshold corresponds to the product of the wall aspect ratio by the acceleration of gravity (g). Compared to non-linear results, the corresponding calculated limit ground acceleration is on the safe side. Moreover, considering floor response spectra, this approach may be easily extended to non-structural walls situated in the upper storeys.

This paper describes the shaking table tests carried out at the European Centre for Training and Research in Earthquake Engineering (EUCENTRE) to investigate the seismic behaviour of four configurations of stacked concrete blocks, commonly used at the European Organisation for Nuclear Research (CERN) as a shielding barrier against different types of radiation. The blocks used for these configurations have been designed to guarantee an adequate level of protection to radiation and, at the same time, to be easily transported and managed for different installations. The block configuration specimens have been tested using the acceleration time-histories of two different earthquakes occurred in the Mediterranean region. Each configuration has been tested several times with acceleration amplitude increments until rigid kinematisms are triggered. This paper presents the test setup and inputs, the related experimental readings and the main results obtained by these tests. The two main mechanisms observed at the interfaces between the blocks during the tests were sliding and rocking. The data collected at the end of the experimental campaign constitute an important source to calibrate different discrete-system-models, in order to study the seismic response of block configurations used for radiation protection in particle physics research institutions.

This paper contains an investigation on the potential decrease of seismic vulnerability related to building replacements for the cities of Sion and Martigny in Switzerland. Those two cities were identified for the present research based on the accuracy of the corresponding available information. Seismic assessment at urban scale was recently achieved for both cities and new buildings are systematically indexed according to the construction regulation of the canton of Wallis (Valais). Sion and Martigny belong to the largest cities of the canton of Wallis and this region is characterized by the highest seismicity within Switzerland. The investigation focuses on a 4-year period between 2016 and 2019. Cases for which an existing building is demolished and replaced by a new one were identified and checked. Those cases do not represent general practice. The majority of new buildings are built on free land. Consequently, the building replacement rate is too low to lead to a significant decrease of the seismic vulnerability at urban scale. In addition to the systematic appropriate seismic design of new buildings, retrofitting of existing buildings therefore remains the adequate strategy for seismic vulnerability mitigation. In case of replacement, low-rise buildings are generally replaced by mid-rise buildings. Moreover, unreinforced masonry buildings are usually replaced by reinforced concrete shear-wall buildings. This slightly impacts the building stock distributions but the seismic vulnerability is not significantly changed, since the demolished buildings are not the most vulnerable ones. Nevertheless, few obvious isolated vulnerability decreases occurred with respect to the demolition of soft-story buildings for instance. By contrast, seismic vulnerability may also be increased in the case where a new building is built against an existing one with a different story level and without an adequate seismic separation joint.

Fling-step and forward directivity are the major consequences of near-fault ground motions as they can impose unexpected seismic demands on structures located in the vicinity of the fault. The pernicious effect of forward directivity on the seismic behavior of structures has been studied widely. However, not much research has been conducted to investigate the influence of fling-step that is related to a large co-seismic displacement. Moreover, the inconsistent results reported in the literature create a scientific challenge about the effect of fling-step on the seismic behavior of long-period structures. In this paper, the effect of fling-step is studied by comparing the displacement ductility demand in various single degree of freedom systems with different natural frequencies and strength reduction factors, subjected to long-period ground motions (generated and as-recorded) with and without fling-step. Subsequently, two 11- and 20-story reinforced concrete buildings are considered and the effect of removing the fling-step on their maximum inter-story drifts is studied. The results indicate that the ratio of the fundamental period of the structure to the fling-pulse period plays an important role and the demands imposed on those systems without fling-step may increase or decrease based on the ground motions type and structural characteristics. Also, a similar trend in the displacement ductility demand was observed in this condition.

This paper deals with the development of nonlinear static models for the calculation of capacity curves that are subsequently applied in a scenario-based assessment of school buildings. The investigated building types include unreinforced masonry buildings with rigid floors and reinforced concrete buildings with slender shear walls, both of which are typical in central Europe. The curves were established by means of simplified mechanics-based models of the structures together with the expected failure mechanisms of the structural members, from which bilinear capacity curves were calculated. These capacity curves were used to derive fragility curves for a number of predefined earthquake scenarios in Basel, Switzerland. This application revealed that with the initial capacity curves developed in this project, the damage in the earthquake scenarios was largely overestimated compared to that predicted from empirical intensity-based vulnerability models. The initial curves had been determined with models that made use of code recommendations for the assessment of existing structures together with experimental mean material characteristics. Modifications to the modelling procedure, including revised assumptions concerning the failure modes and changes to the assumed initial stiffness based on vibration measurements, led to revised curves which featured, in particular, increased ductility. With these updated and validated capacity curves, results closer to the empirical intensity-based models were obtained. While the type of modelling used herein has its limitations due to simplicity, it was still possible to account for the influence of typical characteristics (such as the detailing of RC walls) on the relative behaviour and response of the buildings, thus justifying the use of analytical capacity and fragility functions, as opposed to empirical intensity-based models, in the final risk assessment.

After a damaging earthquake, assessment of the residual seismic capacity is required for large parts of the building stock. Increased vulnerability of structures together with the threat of immediate aftershocks call for rapid and objective decision making. Structural identification has the potential to reduce parameter-value uncertainties of physics-based models through interpreting measurement data. Significant amounts of uncertainty are associated with the non-linear behaviour of structures during extreme events such as earthquakes. Therefore, a structural identification methodology that accommodates multiple sources of systematic modelling uncertainties is used. Error-domain model falsification (EDMF) enables structural identification through combining damage grades observed by visual inspection with fundamental frequencies that are derived from ambient vibrations. Parametric uncertainties of a hysteretic model are reduced with the two information sources in order to extrapolate the vulnerability of the building regarding future earthquakes. The applicability of the methodology is shown using measurements made on a mixed reinforced-concrete unreinforced-masonry building tested on a shaking table. Based on nonlinear time-history analyses involving single-degree-of-freedom models, EDMF leads to more precise, yet robust, vulnerability predictions of earthquake-damaged buildings when compared with prediction ranges that are obtained without data interpretation.

The nonlinear seismic displacement demand prediction for low-period structures, i.e., with an initial fundamental period situated in the plateau of design response spectra, is studied. In Eurocode 8, the computation of seismic displacement demands is essentially based on a simplified method called the N2 method. Alternative approaches using linear computation with increased damping ratio are common in other parts of the world. The accuracy of three methods for seismic displacement demand prediction is carefully examined for the plateau range of Type-1 soil class response spectra of Eurocode 8. The accuracy is assessed through comparing the displacement demand computed using nonlinear time-history analysis (NLTHA) with predictions using simplified methods. The N2 method, a recently proposed optimization of the N2 method, and the Lin and Miranda method are compared. Nonlinear single-degree-of-freedom systems are subjected to several sets of recorded earthquakes that are modified to match design response spectra prescribed by Eurocode 8. The shape of Eurocode 8 response spectra after the plateau is defined by a constant pseudovelocity range (1/T). However, the slope of this declining branch may be specified using precise spectral microzonation investigation. However, the N2 method has been found to be particularly inaccurate with certain microzonation response spectra that are characterized by a gently decreasing branch after the plateau. The present study investigates the impact of the slope of the decreasing branch after the plateau of response spectra on the accuracy of displacement demand predictions. The results show that the accuracy domain of the N2 method is restricted to strength reduction factor values around 3.5. Using the N2 method to predict displacement demands leads to significant overestimations for strength reduction factors smaller than 2.5 and to significant underestimations for strength reduction factors larger than 4. Fortunately, the optimized N2 method leads to accurate results for the whole range of strength reduction factors. For small values of strength reduction factors, up to 2.5, the optimized N2 method and the Lin and Miranda method both provide accurate displacement demand predictions. However, the accuracy of displacement demand prediction strongly depends on the shape of the response spectrum after the plateau. A gently decreasing branch after the plateau affects the accuracy of displacement demand predictions. A threshold value of 0.75 for the exponent of the decreasing branch (1/Tα) after the plateau is proposed. This issue should be considered for the ongoing developments of Eurocode 8.

In Europe, computation of displacement demand for seismic assessment of existing buildings is essentially based on a simplified formulation of the N2 method as prescribed by Eurocode 8 (EC8). However, a lack of accuracy of the N2 method in certain conditions has been pointed out by several studies. This paper addresses the assessment of effectiveness of the N2 method in seismic displacement demand determination in non-linear domain. The objective of this work is to investigate the accuracy of the N2 method through comparison with displacement demands computed using non-linear time-history analysis (NLTHA). Results show that the original N2 method may lead to overestimation or underestimation of displacement demand predictions. This may affect results of mechanical model-based assessment of seismic vulnerability at an urban scale. Hence, the second part of this paper addresses an improvement of the N2 method formula by empirical evaluation of NLTHA results based on EC8 ground-classes. This task is formulated as a mathematical programming problem in which coefficients are obtained by minimizing the overall discrepancy between NLTHA and modified formula results. Various settings of the mathematical programming problem have been solved using a global optimization metaheuristic. An extensive comparison between the original N2 method formulation and optimized formulae highlights benefits of the strategy.

The framework to evaluate the benefit of seismic upgrading of Galanis et al. (2018) is compared to that present in the Swiss seismic code for existing buildings since 2004, updated in 2017. To illustrate the comparison, the example building of Galanis et al. (2018) in Zurich is analyzed following the Swiss code. It is shown that the concept of Degree of Seismic Upgrade is not relevant for practical applications. More generally, the approach of Galanis et al. (2018) would be more suited to a risk-based framework (like the Swiss code) than to a performance-based framework like the one they followed. For existing buildings, we claim that it is appropriate to define the retrofitting strategy based on the absolute level of risk, whereas targeting the safety level of the design code is rarely cost-efficient.

Recent events around the globe are evidence that earthquake action is still a threat for many structures. Low replacement and retrofitting rates of urban housing mean that many buildings do not comply with seismic actions defined in present-day seismic codes and thus, important post- seismic assessment activities are still to be expected. City-scale resilience, which implies rapid recovery of building functionalities, is undermined by the slowness and qualitative nature of visual inspection (being current practice for post-seismic assessment). A methodology involving model- based interpretation of post-seismic data sources to assess residual capacity of damaged buildings is presented. Vibration measurements and visual inspection outcomes are combined to reduce the uncertainty related to residual capacity. Simplified behaviour models for recurrent building types are used to predict building behaviour during future events. A simulated scenario on a real building stock of a typical Swiss city subjected to moderate seismicity is used for illustration.

Structural identification of existing structures is a subject of increasing interest in the civil-engineering community because of its potential to use measurement data to enhance asset-management decision making. An important structural-identification application is residual-capacity assessment of earthquake-damaged structures. Known to be potentially slow and subjective, current assessment practices rely mostly on expert-conducted visual inspection. Structural-identification techniques can help overcome shortcomings of visual inspection through improving estimates of residual capacity. Physics-based models are needed to predict structural behavior under future loading (extrapolation). Especially for earthquake-engineering simulations, a large variety of prediction models and techniques exists. While engineers often prefer simplified behavior models for assessment, data-interpretation applications usually involve detailed model classes. Neither choice is appropriate for all situations. This paper contains a proposal for more rational model-class selection than typically employed in current practice. Model-class selection criteria are described and illustrated using two cases. Knowledge of the earthquake signal is identified as the main criterion to select model classes and analysis tools. Displacement-demand predictions are reduced by up to 91% using structural identification techniques and are validated for all tested model classes by observed behavior under aftershocks. Applicability of this model-class selection is most attractive for post-earthquake assessment of residual capacity (not damage detection) where there is a reduced availability of measurement data, such as when there is no continuous monitoring data. This strategy provides useful support to engineers for key decisions related to asset management and structural resilience.

After destructive earthquakes occurred in Italy between 2009 and 2016, the Italian Parliament approved in 2017 a new version of the Sisma Bonus, which includes Guidelines for the classification of the seismic risk of buildings. In Sisma Bonus, the seismic risk is evaluated through two methods: simplified or detailed. In this paper, the simplified approach is integrated into a Building Information Modelling (BIM) software, Autodesk Revit. The vulnerability assessment of existing masonry buildings is performed following the macroseismic approach (EMS-98). Various masonry-building types are assigned to vulnerability classes with a specific seismic vulnerability index. The procedure proposes to evaluate a final vulnerability index as a quantitative evaluation, instead of the qualitative one by EMS-98. Vulnerability analysis is inserted directly in Revit to create an interaction between BIM and seismic scenarios. Features that characterise each masonry type are inserted into newly created Revit Templates. Two additional modifiers account for mechanical aspects of masonry (mortar quality, transversal connections, etc.) and global building behaviour (vertical and in-plane irregularities, presence of anti-seismic devices, etc.). A flowchart developed in Dynamo automates the vulnerability index calculation using features of the BIM model.