Seismic Hazard and Risk Assessment

Understanding of lithosphere dynamics, tectonic stress localization, earthquake occurrences, and seismic hazards has significantly advanced during the last decades. Meanwhile despite the major advancements in geophysical sciences, yet we do not see a decline in earthquake disaster impacts and losses. Although earthquake disasters are mainly associated with significant vulnerability of society, comprehensive seismic hazards assessments and earthquake forecasting could contribute to preventive measures aimed to reduce impacts of earthquakes. Modelling of lithosphere dynamics and earthquake simulations coupled with a seismic hazard analysis can provide a better assessment of potential ground shaking due to earthquakes. This chapter discusses a quantitative approach for simulation of earthquakes due to lithosphere dynamics that allows for studying the influence of fault network properties and regional movements on seismic patterns. Results of earthquake simulations in several seismic-prone regions, such as the Vrancea region in the southeaster Carpathians, the Caucasian region, and the Tibet-Himalayan, are overviewed. A use of modelled seismicity in a probabilistic seismic hazard analysis is then discussed.

Earthquake mechanism and fault plane solution information is fundamental to determine the stress field and to define seismogenic and active tectonic zones. At the same time, it is a basic input to compute seismic hazard by deterministic approach. The purpose of this paper is to update the catalogue of the fault plane solutions for Romanian earthquakes for the time interval 1998–2012. The catalogue is limited geographically to the Carpathians Orogeny and extra-Carpathians area located in the south—eastern part of Romania. The catalogue comprises 259 intermediate-depth seismic events and 90 crustal seismic events, covering the study time interval. All the existing information is considered and revised. The fault plane solutions of the Vrancea earthquakes generated in a confined sinking plate in the mantle reflect the dominant geodynamic process in the study region. The typical features revealed by all the previous studies on the subcrustal seismic activity (predominant dip-slip, reverse faulting, characterizing both the weak and strong earthquakes) are reproduced as well by our investigation. As concerns the earthquake activity in the crust, a few new refined aspects are highlighted in the present work: (1) a deficit of the strike-slip component over the entire Carpathians foredeep area, (2) different stress field pattern in the Făgăraş—Câmpulung zone as compared with the Moesian Platform and Pre-Dobrogean and Bârlad Depressions, (3) a larger range for the dip angle of the nodal planes in the Vrancea subcrustal source, ~400–700 against ~700, as commonly considered.

Each of the three major earthquakes (M_w ≥ 6.9) recorded within the Vrancea seismogenic body in the years 1977, 1986 and 1990 may have been the result of long-range interactions. The latter seemed to be initiated in coincidence with a moderate (4.7 ≤ m_b ≤ 4.9) shock that systematically occurred in the 160–175 km depth-range, 3–4 years in advance of the major earthquake. In addition, each corresponding pair of moderate/major events systematically exhibited, in terms of focal mechanisms, a particular pattern: the latter complied with predictions of a numerical model that had addressed along-strike break-off experienced by a near-vertical slab, which—at the same time—was strongly coupled with its overriding plate along a steeply dipping contact extending on a significant vertical length. It was thus suggested that the Vrancea moderate events of thrust-fault type occurred in the 160–175 km depth-range could correspond to the along-strike propagation of a detachment horizon tip; while the major earthquakes subsequently occurred at shallower depths (85–135 km), were possibly caused by the shearing forces that acted, at the upper-plate/underlying-plate interface, in response to the increased downward pull experienced by the Vrancea slab as the break-off was propagating laterally.

The study region is the most important seismic region of Romania when we refer to the crustal seismicity as a source of seismic hazard. So far there have been recorded 91 seismic events that produced significant effect in buildings (Io ≥ 6 EMS), some of them resulting in severe damage and even casualties (Io ≥ 7 EMS). In this paper we modelled the seismogenic sources in the region using a new seismotectonic model constructed on new earthquakes and focal mechanisms catalogues basis. This model was elaborated starting from the relationship between geology and historical and instrumental seismicity and then it was better constrained by geophysical, neotectonic, geodetic data and particularly by active stress field features. The stress tensor parameters and the stress regime have been determined by formal inversion of the focal mechanisms solutions. Our study provides evidence of at least seven different deformation domains with different tectonic regimes as a realistic support for assessing the seismogenic potential of the geological structures. Each seismogenic source is characterized by completeness magnitude (Mcomp), maximum probable magnitude (Mmax) and magnitude—recurrence parameters. The probabilistic hazard maps produced in terms of PGA using the new seismic sources highlights the importance of their configuration on the hazard parameter values and their spatial distribution.

In the last decade, many efforts were done to predict the macroseismic intensity in case of felt Vrancea earthquakes and additionally an online environment was developed for the automatic approximation of the intensity from peoples’ feedback. Besides the extended scientific studies, the near real-time estimation of the macroseismic intensity recently became mandatory for the insurance companies to cover some of the losses and damages that earthquakes might cause to houses, belongings, and other structures. Due to the insurance companies’ requests, the macroseismic questionnaires method was doubled by the seismic intensity determination using instrumental data, as recommended in the Romanian Seismic Intensity Scale Standard (STAS 3684-71). In the present study, the procedure is shown, for the last earthquakes with M_L larger than 5.0, occurred in Vrancea zone, and felt on the extra-Carpathian area. We have selected the case study in Barlad, Vaslui county, because there have been recorded the largest accelerations (122 cm/s2) and have been reported the largest MSK intensities (VI) from Romania during the Mw 5.5 September 24, 2016 earthquake. The results obtained using the two approaches (macroseismic and instrumental data) have been compared and some differences have been found.

The Vrancea seismic region, located at the bending area of the South–Eastern Carpathians in Romania, is the most active zone of seismicity in Europe, producing earthquakes at intermediate depths (60–200 km). The major events (magnitude above 7) are generated at intermediate depth and produce specific patterns of damage over extended areas. In this study we test the macroseismic intensity attenuation laws, using the intensity data point (IDPs) for 8 intermediate depth earthquakes that occurred in Vrancea (between 1738 and 2000). The macroseismic attenuation laws used for testing were Moldovan (Metode si modele statistice in seismologie. Editura Morosan, Bucuresti, pag 236, 2007), Sorensen et al. (Soil Dyn Earthq Eng, 2010), Vacareanu et al. (Macroseismic intensity prediction earthquake for Vrancea intermediate-depth seismic source. Hazards, Nat, 2015). The main purpose of the testing is to determine the best attenuation law that will be used to estimate the expected macroseismic intensity at different sites, and to further use them in the assessment of the seismic hazard and risk of the country and to design the real time shake maps. In conclusion, we have decided that Moldovan (Metode si modele statistice in seismologie. Editura Morosan, Bucuresti, pag 236, 2007) is the best intensity attenuation law for earthquakes located around 90 km depth (the events from March 4, 1977 and May 30, 1990), Sørensen et al. (Soil Dyn Earthq Eng, 2010) law is the best for modelling the macroseismic field due to earthquakes from the lower segment, located around 130 km depth (events from November 10, 1940 and August 30, 1986). For epicentral distances larger than 300 km, Vacareanu et al. (Macroseismic intensity prediction earthquake for Vrancea intermediate-depth seismic source. Hazards, Nat, 2015) law fits best the intensity distribution.

The Vrancea seismogenic zone denotes a peculiar source of seismic hazard which represents a major concern in Europe, especially to Romania and neighbouring regions from Bulgaria, Serbia and Republic of Moldova. The strong seismic events that can occur in this area can generate the most destructive effects in Romania and may affect high-risk manmade structures such as nuclear power plants, chemical plants, large dams and pipelines located within a wide area including the Northern zone from the Republic of Bulgaria and the SW of the Moldavia Republic. A major part of the information for determining the design basis earthquakes consists of a complete set of historical earthquake data. Therefore, it is necessary that the available historical records to be collected, extending as far back in time as possible. Most of these historical records will be of descriptive nature, including such information as the number of houses damaged or destroyed, the behaviour of population etc. But from such information a measure of the intensity scale value of each earthquake in modern macroseismic intensity scale values may be determined. During the past project “Bridging the gap between seismology and earthquake engineering: from the seismicity of Romania towards a refined implementation of seismic action EN1998-1 in earthquake resistant design of buildings (BIGSEES)”, the authors developed the macroseismic intensity map of Romania by using newly compiled information about the damages experienced by 115 churches and monasteries after 10 strong earthquakes (Mw > 6.9) occurred in Vrancea zone starting with XVth century.

Rock microfracturing in the Earth’s crust preceding a seismic rupture may cause local surface deformation fields, rock dislocations, charged particle generation and motion, electrical conductivity changes, radon and other gases emission, fluid diffusion, electrokinetic, piezomagnetic and piezoelectric effects as well as climate fluctuations. Space-time anomalies of radon gas emitted in underground water, soil and near the ground air weeks to days in the epicentral areas can be associated with the strain stress changes that occurred before the occurrence of medium and strong earthquakes. This paper presents some results of continuous monitoring of radon in air near the ground with short term (ten days exposure time) solid state nuclear track detectors (SSNTD) CR-39 at seismic stations Plostina (Vrancea), and Bucharest Magurele, Romania. During 2012–2016 periods, radon concentration anomalies along with meteorological parameters were found to be statistically significant for the seismic events within the moment magnitudes Mw ≥ 5.0 and epicentral distances of 15–200 km for the Vrancea source. The frequent registered positive anomalies with constant environmental perturbation indicate the opening and closing of micro cracks within the volume of dilatancy by strain stress energy, result which is very important for short term earthquake prediction.

The goal of this paper is to present some observations about the abnormal animal behavior prior to and during some Romanian subcrustal earthquakes. The major Vrancea earthquakes of 4 March 1977 (M_W = 7.4, Imax = IX–X MSK), 30 August 1986 (M_W = 7.1, I₀ = VIII–IX MSK) and 30 May 1990 (M_W = 6.9, I₀ = VIII MSK), were preceded by extensive occurrences of anomalous animal behavior. These data were collected immediately after the earthquakes from the affected areas. Some species of animals became excited, nervous and panicked before and during the earthquakes, such as: dogs (barking, howling and running in panic), cats, birds (hens, geese, turkey hens, ducks, pigeons, parrots), cattle, pigs, mice and rats (came into the houses and have lost their fear), horses, fishes, snakes etc. These strange manifestations of the animals were observed on the entire territory of the country, especially in the extra-Carpathian area. This unusual behavior was noticed within a few seconds to days before the seismic events, but for the most of cases the time of occurrence was within two hours prior to the quakes. We hope that one day the abnormal animal behavior will be documented enough in order to be used as a reliable seismic precursor for the intermediate depth earthquakes.

Bodrum Peninsula is situated on the southwest coast of Turkey, near the Aegean Sea coast. The Peninsula extends ~42 km in the E-W direction and ~15 km in the N-S direction between the Gulfs of Güllük and Gökova. The Bodrum peninsula with a population over a million in summer season is one the touristic centers of Turkey. The region is also surrounded by numerous active seismic entities such as Ula-Ören Fault Zone, Gökova Graben, eastern part of the Volcanic Arc and Hellenic Arc-Trench System etc. These systems demonstrate high seismic hazard and pose a great threat to settlements in and around the region. Considering the high seismic risk and high population of the peninsula, a strong ground motion monitoring system, consists of five accelerometric stations, was deployed in June 2015 by Boğaziçi University, Kandilli Observatory and Earthquake Research Institute (KOERI), Earthquake Engineering Department. Three out of five stations (B1, B2 and B3) are on alluvium sediments. The rests are on Limestone (B4) and Volcanic rock (B5). Up to now the network has recorded more than 100 earthquakes. Among the dataset, 25 events with magnitudes (Ml) from 3.0 to 5.5 occurred within 200 km epicentral distances were selected for site effect calculation. Predominant frequencies and amplification values of shallow soil layers under the stations were estimated through Horizontal to Vertical Spectral Ratio and Standard Spectral Ratios. The results indicate that (1) predominant frequencies change between 2.1 and 3.5 Hz for soft soils, where it is 5.8 Hz for the reference site, (2) relative amplifications are in the range of 2.3–6.8, and (3) empirically estimated sediments thickness beneath the B1, B2 and B3 stations vary between 35.6 and 64.2 m.

The paper presents an overview of available data concerning ground types for seismic design in Romania. A short overview of a ground information database created during BIGSEES Romanian project is presented. A comparison of shear wave velocity for 19 sites in Bucharest determined by PS logging measurements and by Wald topographic slope method is discussed. The paper reiterates the conclusion of a study regarding the Eurocode soil factor S derived from the Romanian seismic motions. The need for an enlarged database of in situ determined ground condition is underlined, at least at the location of seismic stations. Based on borehole-specific data (geotechnical properties, hydrologic factors) and velocity profiles, evaluations of soil liquefaction potential and related indices were performed by using empirical equations proposed in literature. The application of GIS tools provided a spatial distribution of liquefaction susceptibility of Quaternary alluvial sediments in Bucharest.

The interest for this topic was raised by the occurrence of the destructive Vrancea earthquake of 1977.03.04, when the first strong motion record of Romania was obtained at the Building Research Institute (INCERC) Bucharest. The attempt to assess the ground motion intensity on the basis of instrumental criteria specified by the Medvedev-Sponheuer-Karnik (MSK) intensity scale failed, due to strongly divergent results obtained by means of using the peak ground acceleration (PGA) and peak ground velocity (PGV) criteria. This failure was due to the fact that the inflexible MSK criteria referred to relied on the implicit non-realistic assumption that all ground motions are characterized by an invariable velocity/acceleration corner period of 0.5 s. A flexible Spectral Intensity Assessment System (SIAS) relying on ground motion accelerographic information was developed. This makes it possible to estimate, according to needs, global intensity, frequency related intensity, intensity averaged upon a spectral band etc. Alternative basic kinematic ground motion characteristics for global intensities and for frequency related intensities were introduced. Correlation analysis performed revealed quite strong correlations between results of using alternative criteria. Characteristic parameters were calibrated and alternative calibrations are discussed. Some illustrative cases are presented. Comments and recommendations are finally presented.

The spatial correlation of ground motions is a subject extensively analysed in the literature, with many studies obtaining spatial correlation models for different datasets, using multiple ground motion prediction equations for various ground motion parameters, being a necessary tool in assessing the seismic risk of building portfolios or spatially distributed systems. A subject tackled mostly for shallow earthquakes datasets, in recent months, two studies considering a database consisting of strong ground motions generated by earthquakes originating from Vrancea intermediate-depth seismic source have been developed. The differences between the two studies consist of the approach in obtaining the correlation model, directly evaluating the correlation coefficients and using the semivariogram approach. A comparison of the two studies is made, resulting in different decay ratios for the same ground motion parameter, the main reasons being the restrains encountered in the first methodology and the subtraction of some ground motion records in the second study. An investigation regarding the influence of the dataset is performed by developing a correlation model for an adjusted dataset using the direct approach. Comparisons with other available models are performed, revealing higher correlation values and more gradual decays for the two studies discussed here, which is mainly caused by the different seismo-tectonic context of the Vrancea intermediate-depth source.

Over the past decade there have been various studies on the development of seismic design maps using the principle of “risk-targeting”. The basis of these studies is the calculation of the seismic risk by convolution of a seismic hazard curve for a given location (derived using probabilistic seismic hazard analysis) with a fragility curve for a code-designed structure (ideally derived from structural modelling). The ground-motion level that the structure is designed for is chosen so that the structure has a pre-defined probability of achieving a certain performance level (e.g. non-collapse). At present, seismic design maps developed using this approach are only widely applied in practice in the US but studies have also been conducted on a national basis for France, Romania, Canada and Indonesia, as well as for the whole of Europe using the European Seismic Hazard Model. This short article presents a review of the state of the art of this technique, highlighting efforts to constrain better some of the input parameters. In addition, we discuss the difficulties of applying this method in practice as well as possible paths forward, including an empirical method to estimate an upper bound for the acceptable collapse and yield risk.

An interaction of three major risk components (seismic hazards, vulnerability and exposure) are analysed here, and preventive measures to mitigate disasters are discussed. The importance of action-oriented research on earthquake risk reduction co-produced with multiple stakeholders, including engineers and policymakers, is analysed. This importance is evidenced by the increasing vulnerability and exposure of society to risk in many earthquake-prone regions and by the need for cross-cutting actions in policy and practice related to sustainability.

One of the most crucial issues in times of earthquake disaster is securing the functions of disaster management facilities such as city halls, hospitals and fire stations. However, in the case of past earthquake damage, there are many problems that important structures cannot be used after the earthquake. In order to solve this problem, it is necessary to predict earthquake damage beforehand and take countermeasures such as seismic retrofitting. Also, when an earthquake actually occurs, it is necessary to analyse the degree of damage of the building as soon as possible and diagnose whether it is safe or not by aftershocks. In this paper, seismic simulations are conducted on the east and the west buildings of Toyohashi City Hall using the earthquake ground motion waveform for the future Nankai Trough earthquake. As the result, it was found that the buildings have sufficient earthquake resistance. Additionally, IT strong-motion seismometers were installed in the city hall to continuously monitor vibrations. If an earthquake strikes, the vibration data obtained by the seismometers are sent to the computer through the Internet to simulate the building. Then, the results of simulation are sent to the building owner to assess whether the building is safe for aftershock. By automating this process, real-time safety assessment is possible.

This paper summarizes the UTCB results for the “National Risk Assessment—RO RISK” project. Within the RO-RISK project, coordinated by the General Inspectorate for Emergency Situations, the first nation-wide assessment of all types of natural risks was performed in 2016. The work was supported by collaboration of disaster reduction experts and earthquake risk modelling specialists from INFP and URBAN-INCERC. The seismic risk assessment was performed for the entire country, at the most detailed resolution available, which is the administrative-territorial unit. For each building typology, four limit states were considered in order to generate fragility curves. Each limit state is associated with a loss percentage, in order to generate vulnerability curves. The assessment shows that among the 10 analysed hazards, the seismic hazard produces the largest impact at country level, 75% of the population and 45% of the vital networks are exposed to moderate and high earthquake risk and Romania’s capital Bucharest, is highly exposed to earthquakes.

This paper highlights some of the results regarding the seismic risk and resilience analysis for the residential building stock of Bucharest, obtained within the framework of the COBPEE research project financed by the Romanian National Authority for Scientific Research and Innovation and which was completed in September 2017. The seismic risk metrics are also compared with those from two other recent studies with the same focus. In addition, the issue of economic feasibility of pre-earthquake strengthening of high-rise RC buildings in Bucharest is also analyzed in this study.

The March 4, 1977, Vrancea earthquake was Romania’s greatest natural disaster in the 20th century. Today, forty years later, its impact, but also post-disaster actions and policies, continue to influence seismic risk. Based on lessons learnt, an improved seismic design code was introduced in 1978 for new construction, but in July 1977 for damaged buildings all strengthening projects were abruptly stopped by a high level political order that allowed only local—often cosmetic- repairs. After 1989, many state archives have been opened, helping us deepen our understanding of how disaster management was conducted in that time. This paper reveals new findings and data on building damage and human casualties. This new evidence suggests that nearly a quarter of the lives lost in Bucharest were not in collapsed multi-story buildings, but in other, yet to be investigated, locations. Also new evidence about the unidentified victims lifts popular doubts on this issue. Lastly, the authors analyze the July 4, 1977, government decision to end the seismic reinforcement of damaged buildings and the debate at the time between specialists and government officials.

During a period of eight months, an extensive survey was conducted on the population of Bucharest as part of the CoBPEE research project, financially supported by the Romanian National Authority for Scientific Research and Innovation. The focus of the survey was to evaluate the level of awareness and preparedness of the population for a hypothetical earthquake generated by the Vrancea intermediate-depth source, the level of expected damage of residential buildings as well the level of implication of the population in the aftermath of the seismic event. In total, 1000 responses were collected. This paper describes the main findings of the survey. Results show that although more than 60% of the respondents are aware of the possibility of occurrence of a major earthquake in Romania, a very limited number is prepared to deal with such a situation. Also, most respondents would feel the safest in a building built in the period 1978–1992 rather than in a building built in the past ten years, showing a lack of confidence in the construction industry. As far as post-earthquake attitude is concerned, the vast majority of residents agree to provide humanitarian assistance in various ways, financial aid being the last preference.

The issue of seismic risk in Bucharest, a 1.7 mil people Capital, is very much ignored, considering the scale and the urgency. Seismic risk assessment needs to focus also on human losses, rather than on physical aspects like location, construction materials, etc. “How many people live in seismic risk housing?” is a question not even the municipality can give a recent evidence based answer to. The paper presents the results of ALERT—seismic risk mitigation project, started in Bucharest in February 2016. ALERT is based on an online data crowdsourcing platform regarding seismic risk housing (with particular focus on the number, needs and problems of their inhabitants). The Alert poll results, as of September 2017 indicate the severity of the problem. More than 8000 dwellers were counted in 80% of the highest seismic risk buildings (Seismic Risk Class I) and it is expected that by the end of the research the 10,000 people threshold will be long exceeded. The paper is intended to highlight insights on ownership, occupancy and management of these buildings. The conclusion argues the need for a more human centric approach of seismic risk assessment to complement the engineering and geological perspectives.

The author has developed a new method for evaluating the seismic performance of existing structures from measured accelerations based on the capacity spectrum method. This involves comparing the performance curve, which is the equivalent nonlinear behavior of a simplified single-degree-of-freedom system, and the demand curve, which is the relationship between the response acceleration and displacement spectra. Two telecommunication towers in Japan were instrumented in 2016, and their responses during several earthquakes have been recorded. This paper discusses the evaluation of damage during two earthquakes. Moreover, parameters such as the predominant period and the required performance are discussed. The proposed system evaluated both towers as being “elastic”. The damping ratios of the towers are very low, which caused the oscillations to continue for more than 5 min after the mainshock of each earthquake because of long-period components of the seismic motion.

Seismic protection of cultural heritage constructions is a priority in earthquake prone countries, due to their cultural, historical and touristic importance. The paper presents a first step toward the seismic evaluation of the “Carol I” Royal Mosque in Constanța, Romania: ambient vibration measurements and the assessment of the existing damage state induced by previous earthquakes and/or other actions (index R2 according to the Romanian code for seismic evaluation of existing buildings P100-3/2008). The mosque was built in 1910–1913 and has a masonry structure with a 26 m height reinforced concrete dome. It has an approximately 40 m height RC minaret and thus it is between the first civil constructions using reinforced concrete in Romania. The construction experienced the major earthquakes of 1940 (M _W = 7.7) and 1977 (M _W = 7.5) and several other medium size events originating from Vrancea subcrustal seismic source without significant damage. However, the long-term climatic aggression had a negative impact on the structure. Ambient vibration measurements were performed in the minaret. The results will be used for the proper calibration of the computational model for linear analysis.

Japan, which is one of the most earthquake prone countries in the world, has suffered from damaging earthquakes repeatedly and learned lessons from damages. First, history of damages to existing reinforced concrete (RC) buildings due to previous earthquakes and seismic code revision are summarized. Secondly, basic concept and procedure of Japanese seismic evaluation method were outlined and seismic capacity index, I _s , of buildings suffered Kobe Earthquake. Strong correlation between damage level and seismic capacity index, I _s , was found. After the 1995 Kobe Earthquake, the law for promotion of seismic evaluation and retrofit was enforced based on the lessons learnt from the damage and investigation. Seismic evaluation and retrofit were widely applied to existing RC buildings in all over Japan and contributed to improvement of seismic capacities of existing RC buildings designed by old seismic code. The improvement was proved by recent major earthquakes such as 2011 Tohoku Earthquake and 2016 Kumamoto Earthquake. Typical damage pattern, failure modes and tendency in each earthquake were introduced and effectiveness of seismic evaluation and retrofit was discussed.

Buckling Restrained Braces (BRBs) provide structures with large lateral deformation capacity, strength and stiffness. Throughout the years, BRBs proved to be a viable solution, based on their increasing usage as structural fuse elements. A BRB consist of a steel core introduced into a buckling restraining mechanism (BRM). The main BRB’s feature is its quasi-symmetric and stable hysteretic behaviour when cyclically loaded. In addition to normal braces, BRBs have their compressive behaviour improved by confining core’s transversal deformations, and thus restraining the core’s global buckling. Due to the fact that most BRBs are proprietary and rather manufactured than designed, design codes (P100-1/2013) require their experimental qualification. This code’s regulation represents an impediment in using the BRBs on a wider scale. To overcome these problems, a set of typical BRBs were developed with capacities corresponding to typical steel multi-storey buildings in Romania. The paper presents the pre-test numerical simulations performed. The numerical finite element model development using Abaqus 6.14 software and its calibration based on experimental data are presented in detail. The numerical study was used to develop “conventional” and “dry” solutions by analysing several different solutions. The main difference between the two is the absence of concrete in the case of “dry” solution. The cyclic performance of the BRBs was assessed in terms of compression adjustment factor and global performance.

The seismic capacity evaluation is a key-tool for practitioners in the standard post-design stage of building structures. This also serves as a major component for performing higher level analysis modules as seismic vulnerability analysis, risk analysis, loss estimation and resilience analysis. The seismic capacity of a structure is dependent of the applied load pattern as well as of nonlinear modelling of members. The paper examines the dependency of capacity curve parameters of typical low-rise regular reinforced concrete frames as a large proportion from actual building stock in Bucharest, using both nonlinear static and dynamic analysis approaches as well as discrete and distributed available plasticity models for reinforced concrete members. The sensitivity analysis of global seismic damage index based on the probabilistic approach using HAZUS methodology (2007) is then performed. A more accurate prediction of structural capacity in conjunction with integrated tools for the assessment of the damage states up to progressive collapse associated to various earthquake scenarios and time-domain analysis approach would truly lead implementing a real performance-based seismic design into practice.

The aim of this study is to identify the optimal cross sections and reinforcement area of the beams and the columns in a frame structure in order to improve their seismic response. A six-storey reinforced concrete structure, modelled using fibre finite elements to represent the nonlinear behaviour, was studied. The structure was first designed according to existing codes (the equivalent static load method) and the total quantity of material computed (concrete and reinforcement). Secondly, a genetic algorithm was used in order to determine the optimized beam and column cross section dimensions along with the longitudinal reinforcement area for both types of elements. The optimization process aims to minimize the cost of the reinforced concrete structure while at the same time improving or at least maintaining the seismic response of the structure. A set of constraints was imposed for the optimization process: the minimum reinforcement area, the ratio between the beam height and width and the maximum drift of the structure at both the ultimate and service state, according to design codes. Dynamic time history analysis is used to determine the maximum drift of the structure. The analyses are carried out for three ground motion records which represent the seismic conditions given by the Vrancea source in Bucharest.

In current codes there is no rapid method of seismic evaluation of buildings, as the three utilised methods are intensively demanding in terms of time, human resource and materials. Due to this reason, it is necessary to adopt and develop a method based on international codes, applicable to the structural systems in our country. As a starting point, the rapid assessment procedure published by the Federal Emergency Management Agency in 1988 is presented. To calibrate the method, 335 buildings were analysed; the vulnerability risk of these buildings was already known, previously certified by approved technical experts that used one of the three methodologies indicated in current seismic evaluation codes. Based on the research, an equivalent point system is created and applied to the structural systems suitable for rapid visual screening (RVS) and also to the characteristic parameters which influence the structural behaviour under seismic actions. Based on the point system applied, the building vulnerability can be determined using the rapid method of seismic evaluation. Moreover, a database is created which allows assessing which buildings require priority for a more detailed analysis through calculations.

Reinforced concrete structures exhibiting tri-dimensional effects such as torsion and nonlinear response are a main concern in the field of earthquake research. The purpose of the paper is to present an example of structural modeling of a reinforced concrete structure sensitive to torsion and how to calibrate the structural response to the results of the experimental scale test using Perform 3D software. The analyzed structure is part of the scientific research program “Seismic Design and best-estimate Methods Assessment for Reinforced Concrete Building subjected to Torsion and non-linear effects’’ (SMART 2013), financed by “Commissariat a l’Energie Atomique et aux Energies Alternatives’’ (CEA) and “Electricité de France’’ (EDF). The scope of the program SMART 2013 was to analyze, compare and validate the design and the modelling methods used in evaluating the response of reinforced concrete structures subjected to high intensity seismic loads. The structure, tested using a seismic shake table, was built on a smaller scale (1/4), and it represent a part of a building that is used to host nuclear facilities. The geometry and the dimensions of the specimen were chosen in order to highlight the torsional-effects. To assess the behavior of vibrating mass structures were used both synthetic accelerograms and some real accelerograms. Calibration elastic structure, and thus determine the stiffness and damping characteristics, was based on the elastic acceleration response spectrum. The experimental results revealed a high degree of accuracy of the model in terms of overall behavior simulation of the real structure.

The seismic performance of infill masonry walls is a topic of growing importance due to the significant number of collapses observed through the recent earthquakes. Nowadays is recognized by the scientific community the influence of these elements in the structural response of reinforced concrete structures subjected to seismic actions. The infills out-of-plane (OOP) behaviour depends on a series of variables and there is a lack of experimental data to understand and predict their expected seismic performance. There is a need of data to calibrate numerical models and to understand the effect of each variable such as type of masonry, boarder constrains, slenderness, previous in-plane damage and insufficient support width in the infills OOP capacity. The present chapter pretends to overview some considerations regarding the performance assessment of infills OOP performance such as based on experimental tests and numerical modelling results. Additionally, a brief literature and international codes recommendations review on this topic will be presented and discusses and will help to understand the importance of the infills seismic behaviour on the performance assessment of reinforced concrete structures.

Lack of adequate ductility in substandard reinforced concrete buildings is a major reason for significant amount of life and economic losses experienced during major earthquakes. Laboratory tests realized at member level (i.e. column and beam tests) show that external wrapping of potential plastic hinging regions of columns with Fiber Reinforced Polymer (FRP) sheets, can significantly enhance the ductility capacity. Thus, major seismic retrofitting documents available worldwide interpret this retrofit approach as a viable alternative and lay the rules for retrofit design with these materials. In this study, a very recent experimental activity that included the full-scale testing of a substandard building retrofitted with the above mentioned approach is briefly presented. Then, the performance prediction of the Turkish Seismic Design Code (2007) for this building is evaluated. Finally, a revision is proposed for the FRP effective rupture strain value defined by this code.

Unreinforced masonry infilled-RC frames are widely used in many developing countries. Even though the influence of the masonry walls on the behavior of structure was recognized from the experience of past earthquake disasters, but many practicing engineers still assume that the infill walls are non-structural walls due to incomplete knowledge of the behavior of such structures. In this paper, an experimental study of two ½ scale specimens with different RC frames and masonry infill walls were tested using a static cyclic loading protocol. The main parameter was the influence of changing the RC frame strength on masonry infill seismic capacity. The results showed that shear strength and deformation capacity of masonry infill greatly improved by increasing the strength of boundary frame. The investigation of strength, ductility and initial stiffness based on experimental results and comparative study with existing methods showed large variations between several methods commonly used to assess the seismic capacity of masonry infill.

The developing countries in the earthquake prone regions in the world are still suffering a lot of casualties as well as building damage. These damages might be caused by inadequate structural design by engineers and/or poor quality control of construction works. In order to contribute to disaster mitigation for existing reinforced concrete (RC) buildings in developing countries, the simplified structural evaluation method based on the philosophy of Japanese evaluation standard; JBDPA (The Japan building disaster prevention association. Standard for seismic evaluation of existing reinforced concrete buildings, 2001) vis-a-vis the international seismic code; IBC (International Code Council, Inc. International Building Code, 2000) was developed by Seki (J Earthq Sci Eng, 2015). However, this evaluation method doesn’t consider the infilled brick masonry wall inside the beam and column. The usual RC building has many infilled brick masonry walls but these are not considered in the structural seismic design. They have the benefit in the strength capacity and the disadvantage in the brittle failure mode. For the structural evaluation of existing RC buildings, the consideration of the infilled brick masonry wall is quite important to get the actual behavior during the strong earthquake. The main objective of this study is to take the infilled brick masonry wall into the structural evaluation for the existing RC building in developing countries.

Gas extraction in the Groningen region of The Netherlands has led to increasing levels of ‘induced’ seismic activity in the area over recent years. A wide ranging building assessment and strengthening programme is currently underway across the region—primarily focussing on large-scale low-rise residential developments. Delft University of Technology (TU-Delft) recently held a blind prediction test where invited participants attempted to determine the response of a full-scale structure, which is representative of a typical masonry house in the Groningen region. The test structure underwent a prescribed cyclic displacement profile. The authors participated in this blind prediction test using “ANSR”, a general purpose analysis program capable of both 2-D and 3-D static, dynamic and time domain analyses. ANSR follows a macro-modelling FEA approach where elements are modelled at a component level. This paper describes how ANSR was used to predict the behaviour of the test structure during the simulated seismic event. It also explores the selection of material properties and their influence on the theoretical performance of the structure. Lastly, the paper describes the benefits of macro-modelling as a viable and cost-effective procedure for undertaking building assessment, particularly where timeframes and accuracy of results are both critical.

Proper anchorage of beam reinforcement in beam-column joints is necessary for a stable hysteretic behavior of seismically loaded structures subjected to large lateral displacements. Anchorage requirements associated with the use of higher strength steel such as S500 generated the need to increase the anchorage lengths and concrete strengths. Formerly used concrete strength classes such as C20/25 and C25/30 are largely replaced with higher quality concrete such as C40/50 or more. In common design practice, anchorage provisions of the repealed Romanian standard STAS 10107/0-90 are still informally used. This might lead to poor anchorage details and related structural problems. This paper draws attention on the specifications of the current standards for anchorage of beam reinforcement. Practical design rules are presented as well.