Search

Traditional houses represent landmarks of local cultures all over the world. In seismically prone countries, the traditional timber frames with different types of infills have shown quite good earthquake resilience, an essential feature considering their large number, their simplicity and their reduced cost, owing to the use of local materials and workmanship. In fact, their seismic behavior fostered the interest in further scientific research, including that addressing engineering aspects. Because of their diversity in layout and detailing, noticeable even among houses in the same area, developing general methods to preserve and strengthen such buildings is still a difficult task. This paper presents an overview of the traditional building construction techniques in Romania, focusing on the structural configuration and detailing of the so-called paiantă houses. Largely used all over the country, these houses have shown that they can generally withstand earthquakes at least without collapsing and, most frequently, with minor or repairable damage. Their preservation is nowadays a major challenge, as they are being gradually either demolished and replaced, or retrofitted by using invasive techniques. Their cultural and heritage value is undeniable, and there are still many things to be learned from the past craftsmanship and re-valuated in the future. Three case studies of rural buildings located in different areas of the country were chosen among the most widespread paiantă versions, and comprehensive engineering assessments were conducted to identify their detailing and degradations. Based on the most common degradations, the conclusions drawn from this study can be used to substantiate further research aimed at selecting the most appropriate construction and strengthening techniques.

The impact of natural hazards on structures and infrastructures is a critical issue that needs to be properly addressed by both public and private entities. To better cope with seismic hazard and to mitigate the risk, long-term multi-sensor infrastructure monitoring represents a useful tool for acquiring information on their condition and vulnerability. However, the current increasing data volume collected using sensors is not suitable to be processed with classical standalone methods. Thus, automatic algorithms and decision-making frameworks should be developed to use this data, with minimum intervention from human operators. A case-study for the application of advanced methods is focused on the headquarters of the Institute for Atomic Physics, a 11-story reinforced concrete building, located near Bucharest, Romania. The instrumentation scheme consists of accelerometers installed at the basement, at an intermediate floor and at the top of the structure. The data were continuously recorded, starting with December 2013. More than 80 seismic events with moment magnitude, MW, larger than 3.8 were recorded during the monitoring period. The current study covers the long-term evolution and variation of dynamic parameters (one value per hour), based on both ambient noise sources and small and medium magnitude seismic events. The seasonal variation of these parameters will be determined, as well as their daily variation and the differences between values obtained from ambient noise and from earthquake-induced vibrations. Other atmospheric parameters (e.g. temperature, precipitation, wind speed) will be considered in future studies. The goal of the PREVENT project, in the framework of which the research is performed, is to collect multi-disciplinary data and to integrate them into a complex monitoring system. The current study achieved the first step, focusing on data from the seismic sensors and setting up the premises for a multi-sensor, multi-parameter, more reliable infrastructure monitoring system.

The aim of this article is to analyze the background, current status, and outlook of seismic monitoring products and services in Bulgaria, Moldova, Romania, and Ukraine. These countries manage seismic networks that contribute to the European Integrated Data Archive node in the framework of the Observatories and Research Facilities for European Seismology, which represents a collaborative effort in coordinating observational seismology across the European region through the collection, archiving, and dissemination of seismic waveform data, metadata, and related products. All of the aforementioned countries share a common threat: strong earthquakes occurring in the Vrancea area located in central-eastern Romania at intermediate depths (usually in the 60–180 km interval). Events such as the ones on 10 November 1940 and 4 March 1977 generated high damage in Romania, northern Bulgaria, and Moldova. In addition to Vrancea, crustal earthquakes in areas such as Shabla or Dulovo can lead to cross-border damage. Therefore, understanding the way national seismic networks are distributed, how they cooperate, and the products and services that they provide in (near) real time and their terms is of significant interest in the context of necessary hazard harmonization and joint emergency intervention and risk mitigation actions.

A case study including a detailed ground settlement analysis is made for a particular loess structure located in the city of Galati, Romania, in order to assess the interdependence of geo-environmental and anthropic settlement triggering factors in the urban system context. In the first part of the study, loess behavior and its effects on built environment are analyzed and discussed based on worldwide historic expertise and current issues. An integrative analysis of loess deposits in natural state, with reference to induced-hydraulic and stress conditions, which was performed by laboratory and in-situ investigations, is then reported. An assessment of basic geotechnical parameters, as well as small-scale modeling of loess settlements at wetting under self-weight were conducted in order to select the most representative experimental area, from the point of view of specific soil structure behavior. Field monitoring surveys were performed to obtain information for quantitative evaluation of settlement time-dependent evolution, by the simulation of excessive moisture. The processing and analysis of experimental data gathered for natural and improved ground conditions revealed that the settlement amplitude of loess deposits with high sensitivity to wetting under self-load can be significantly reduced by the selection of adequate consolidation solutions, based on realistic and undisturbed environmental conditions. The study of soil structure behavior under simultaneous settlement-triggering factors can be integrated in multi-hazard analysis as a support for efficient strategies and mitigation measures, with applicability in the urbanization process, building and foundation design and environmental protection.

The paper presents results from an experimental program implemented for three representative buildings in Bucharest metropolitan area and aimed to explore the potential of various dynamic identification methods in providing information about building state changes. The objective is to establish reference values of potential use in rapid earthquake damage detection systems. Each of the selected buildings was designed according to a different seismic code, in force at the time of its construction. The methods employed for this study were: the analysis of Fourier spectra, the analysis of the transfer function and the random decrement technique. To validate the results, the fundamental periods of vibration determined experimentally were compared with the corresponding values predicted by the empirical formulas specified in the corresponding editions of the Romanian seismic code. The results revealed consistent values for both the fundamental period and the damping ratio of the buildings. However, small variations of the two parameters were identified, depending on the time the recordings were performed, noise sources and levels and building occupancy. The results, in terms of validated data on the dynamic characteristics of Romanian building stock and of assessment of methods performance, add up to the information pool needed for the development of countrywide pre- and post-earthquake assisted decision tools.

The paper presents results from a study on monitoring the long-term variation of the dynamic characteristics of an 11-story reinforced concrete building located near Bucharest. Since the deployment, in December 2013, of a permanent monitoring system, 89 seismic events with a moment-magnitude (MW) larger than 3.8 were reported. Out of these, 80 were recorded properly by the seismic sensors and the data was used to extract the fundamental frequency and the damping ratio of the building for each event. The main method used to compute the dynamic parameters was the Random Decrement Technique. A dependency of the resulting fundamental frequencies on the maximum accelerations at the base and on top of the building was observed. Due to the structural peculiarities, the fundamental frequency of the building on the transverse direction was lower than the one on the longitudinal direction, this being reflected also by the experimental results. The maximum drop in the fundamental frequency was reported for the MW=5.5 October 28th, 2018 seismic event. By performing this type of analyses, the dynamic parameters of buildings can be tracked over long periods of time and their variation under seismic excitation can be assessed, allowing rapid detection of structural health alterations.

The post-earthquake evaluation of structural integrity is a critical point to be addressed in case of emergency situations triggered by the occurrence of seismic events. A valuable method that can provide important indices to experts performing this operation is the monitoring of structures with seismic sensors that record how the structure responds to earthquake ground motion. In the case of permanent monitoring systems, reliable information can be obtained by comparing the data recorded before, during and after the earthquake, and checking if any abnormal vibrations of the structure or dynamic parameter changes have occurred. The presented study analysed comparatively, for an 11-story reinforced concrete building, vibration data recorded before, during and after the October 28th, 2018 earthquake (MW = 5.5). Continuously recorded data was used to determine the hourly values of the fundamental frequency of the building. The short-term behaviour (72 hours) was assessed, highlighting the modal parameters variation during, before and after the earthquake. In addition, an analysis of the data recorded one and a half hours before the earthquake and one and a half hours after the earthquake provided useful information on the evolution of the building state and on how this “recovered” after the earthquake.

The National Network for the Seismic Monitoring and Protection of Building Stock is a key infrastructure of the National Institute for Research and Development in Construction, Urban Planning and Sustainable Spatial Development "URBAN-INCERC" in Romania. This infrastructure includes at present, among other research facilities, a strong-motion network of 64 permanent seismic stations, to which other temporary stations are added for various short-term vibration monitoring projects. Since its establishment in 1967, the seismic network has played an essential role in recording the earthquakes that affect Romania. Today, the seismic stations are distributed all over the country, according to its characteristic seismicity patterns. Most of them use state-of-the-art recording and communication equipment, being permanently connected online to the Data Center in Bucharest. The management of the network implies conducting a complex set of activities, centered on the recording, processing, analysis and interpretation of natural- and human-induced vibrations. All of these are seconded, in parallel, by various maintenance, reporting, logging, communication and dissemination tasks. The logistic and financial management also plays an important role. A rational and efficient administration of the seismic network cannot be acquired without a rigorous organization of data flows pertaining to the various activities performed. The paper provides insights from the organization of the network, highlighting the intercorrelation between the hierarchical levels of its functionality and the logical course of operation. A brief review of the challenges and solutions gradually developed and implemented by the members of the network team, in order to provide the required functionality, is presented.

The SM-ROM-GL database includes data obtained by the processing of records performed at ground level by the Romanian seismic networks, namely INCERC, NIEP, NCSRR and ISPH-GEOTEC, during recent seismic events with moment magnitude Mw ≥ 5 and epicenters located in Romania. All the available seismic records were re-processed using the same basic software and the same procedures and options (filtering and baseline correction), in order to obtain a consistent dataset. The database stores computed parameters of seismic motions, i.e. peak values: PGA, PGV, PGD, effective peak values: EPA, EPV, EPD, control periods, spectral values of absolute acceleration, relative velocity and relative displacement, as well as of instrumental intensity (as defined bz Sandi and Borcia in 2011). The fields in the database include: coding of seismic events, stations and records, a number of associated fields (seismic event source parameters, geographical coordinates of seismic stations), links to the corresponding ground motion records, charts of the response spectra of absolute acceleration, relative velocity, relative displacement and instrumental intensity, as well as some other representative parameters of seismic motions. The conception of the SM-ROM-GL database allows for an easy maintenance; such that elementary knowledge of Microsoft Access 2000 is sufficient for its operation.

Bilinear hysteretic models are an attractive choice in modeling the elasto-plastic behavior of various materials to alternate loads, due to their simplicity and ease of interpreting the results. However, choosing the parameters of the model without taking into account some restrictions can lead to highly unrealistic results. These restrictions are analyzed, and the allowable ranges for the model parameters are determined. The conclusions can be used for a wide range of plastic and composite materials. The significant errors that can occur in the case of the inadequate selection of model parameters are illustrated by a practical application.

During recent years, an increasing number of studies advocate the application of the capacity spectrum method based demand diagrams computed directly from inelastic response spectra, as an alternative to the basic formulation of the method, which uses elastic spectra computed for single degree-of-freedom oscillators with modified characteristics to account for inelastic behavior. When demand diagrams are based on the code-specified elastic spectrum, inelastic spectra are typically determined by dividing the elastic spectrum by strength reduction factors. The paper presents the application of the method, based on strength reduction factors computed with a unified analytical expression, deduced by the author in previous studies. The expression and is valid both for broadband and narrow band ground motions. Taking as a starting point the newly-enforced elastic design spectra in the 2013 edition of the Romanian seismic design code, the method is exemplified for the capital city, Bucharest. It is shown that, for the analyzed case, the use of the proposed strength reduction factors leads to results that are very close to those obtained by the “classical” nonlinear static procedure used in the code. This suggests a good potential for the implementation of the capacity spectrum method in the Romanian code, based on these factors.

U radu se prikazuje tehnička usporedna analiza rumunjskog propisa o ocjenjivanju potresne otpornosti, usklađenog sa zahtjevima EU, u usporedbi s odgovarajućim normama koji su na snazi u Europi i SAD-u, s namjerom da se ustanove mogućnosti daljnjeg razvoja tog propisa. Postupci uspoređivanja ilustrirani su paralelnim ocjenjivanjem seizmičke otpornosti koje je provedeno, u skladu s analiziranim propisima, na armiranobetonskoj okvirnoj konstrukciji usklađenoj s tipologijama građenja koje se koriste u Rumunjskoj., A technical benchmarking study is presented, aimed to evaluate the EU harmonized Romanian seismic assessment code in comparison with its European and U.S. homologues and to identify potential opportunities for its future improvement. The benchmarking procedures are illustrated by parallel seismic assessments, performed, according to the analyzed regulations, on a reinforced concrete frame structure relevant for the building typologies in Romania.

The rapid increase of the number newly-erected high-rise buildings in Romania during the last two decades brought up the importance of the continuous monitoring of their state. For seismic actions, a post-event modification of the dynamic characteristics of a building can provide a rapid indicator about its potential damage. The paper presents the methods, procedures and steps by which a system providing online remote access to data resulting from building vibration monitoring could be implemented and used for buildings in Romania. The system would allow rapid identification of building damage, based on the processing of recorded data. Identified issues, as well as potential bottlenecks are presented, together with the proposed solutions. The system is planned to be implemented by using the infrastructure available at NIRD URBAN-INCERC, Romania. The paper also presents a case study concerning the structural health monitoring of a multi-story reinforced concrete building, carried out by the project team.

Building design codes typically specify seismic forces based on a 5-percent damped elastic design spectrum. To consider the case of structures with damping ratios other than 5%, damping correction factors are used. While these factors are determined for elastic systems, several studies have shown that the effects of damping are different for systems with nonlinear behavior. A study concerning the influence of damping on the nonlinear seismic response of building structures is presented. To separate the influence of nonlinear behavior, spectra of the ratio between the seismic strength demands corresponding to nonlinear and linear behavior, respectively, were computed, for damping ratios ranging between 2% and 10% and various constant ductility values. A database of ground motion records from the three strongest earthquakes that affected Romania during the last four decades was used in the study. The records were grouped into two sets, according to their frequency bandwidth. The spectral values computed for each set were processed statistically and results were expressed with reference to the 5%damped spectra. It was found that, for the analyzed damping range, the influence of this parameter on the nonlinear response is weak to moderate, for both considered types of frequency content.

An analysis of seismic force levels used in building design during the distinct periods of the pre-1990 evolution of Romanian codes is presented in the initial sections of the paper. The main chang...

The paper presents the results of a study performed on a large ground motion database, containing records obtained during the three strongest earthquakes that occurred during the past four decades in the Vrancea seismogenic zone. In order to express strength demands imposed by these earthquakes, constant-ductility nonlinear acceleration spectra were computed for two sets of seismic records, selected as representative for narrow frequency band and broad frequency band ground motions, respectively. The spectra, determined for various types of bilinear hysteretic models, were normalized with respect to peak ground acceleration and mean values, as well as coefficients of variation, were computed for each analysis case. The sensitivity of spectral values to the variation of strength hardening and stiffness degradation parameters was determined, with reference to the elastic-perfectly plastic model. Conclusions were drawn, separately for the two distinct types of ground motion frequency content, on the significance of the considered hysteretic model parameters for the assessment of seismic strength demands.

Strength reduction factors are an important component of the force modification factors used in the calculation of seismic code forces, as they account for the effect of the nonlinear hysteretic behavior of the structure. They are expressed as the ratio between the elastic strength demand and the inelastic strength demand induced in a structure by the earthquake. The evaluation of strength reduction factors has applications in the substantiation of seismic force modification factors in building design codes and in the direct application of the capacity spectrum method. The paper presents a study performed on two sets of accelerograms having different spectral content types, i.e. narrow frequency band records and broad frequency band records. Based on constantductility spectra of strength reduction factors, computed with 50% and 10% probability of exceedance, a unified analytic formula is developed, to describe the variation with ductility and vibration period of these factors. By modifying the values of the coefficients of the variables, the formula can be adapted for each type of spectral content. The formula is further refined, by determining a new set of coefficients, to also account for the influence of the predominant period of the ground motion in the case of narrow frequency band records.

In a country like Romania, where about two-thirds of the territory is affected periodically by strong earthquakes, the proper design of buildings to seismic actions is an essential prerequisite for the safety of the population. Structural engineers are responsible for taking appropriate measures in the design of buildings, so that these will not collapse in future earthquakes. This is accomplished by an intricate and laborious process, for which seismic codes provide the necessary rules and procedures. With the accession of Romania to the EU, the country has adopted several European standards and regulations, which have replaced or completed the national regulatory body. At the same time, national codes were harmonized with European standards, in the framework of a countrywide programme that started in the early '90s. The current Romanian code for the design of buildings for earthquake resistance, P100-1/2013, represents an improved version of the first European harmonized seismic code, P100-1/2006. Due to their increased complexity and novelty, the application of these codes in the design of buildings represents a significant challenge for the professional community. Practically all structural engineers more than 32 years old in the country were taught seismic design according to older codes. Several initiatives were taken for their professional upgrading, in which universities and professional associations were involved. However, the impact of these initiatives is still very low. An online platform for the instruction of structural design engineers in the use of the new seismic design code, based on the Moodle platform, is presently developed by the authors, in the framework of a complex research project, involving a consortium of three institutions: a university, a research institute and an IT organization. The platform will consist of a body of knowledge, supplemented with related wiki sections. Exercises, tests and quizzes will be included, to facilitate learning. A collection of multimedia resources, with video presentations of renowned specialists will be also available to users. Feedback from the professional community and from prospective users will be collected by questionnaires available on the platform. A forum will be also configured, to allow user interaction.

In urban areas, there is a need to evaluate the dynamics and impacts of impending disasters, in order to ensure planning for resilience, emergency actions, and humanitarian support. In this respect, a Bucharest area that suffered a deep trauma in the 1980s was studied. The total or partial demolition of the old urban fabric was ordered by the authoritarian regime to build a new Civic Center. The area was declared as a protected built area in the 1990s. The inventory of the building stock was done in the framework of this project, based on data on building’s age, height, and materials. Additionally, the cultural value was studied with scoring criteria and methods, based on the six scaling stages of the Romanian Law of Monuments. The functional value, as well as the seismic damage and vulnerability, was evaluated for existing building classes. The paper presents examples of multi-hazard scenarios elaborated for this area, considering earthquakes, flooding, and terrorist attacks on public institutions. The spatial databases and online tools were used for mapping the buildings, as well as hazard impacts. According to the results of the above scenarios, shelters/security centers can be created, for earthquake evacuation, in the nearby “Mihai Eminescu” College while, for high-level flooding, the refuge and shelter area should be located in a higher place, near the Academy House or the Romanian Parliament. For other hazards, a center located either at “Mihai Eminescu” College or in Izvor Park is recommended.

This research aims at providing a sound concept and pilot application of a security centre in a study area of Bucharest that suffered a demolition in the 1980s. As this is at present a protected area, there is a need for a multi-hazard threats assessment. The cultural value was assessed with scoring criteria and methods, on six scaling stages. The functional value, as well as the seismic vulnerability was evaluated, for building classes and urban plan provisions. The hazards and scenarios were for: earthquakes, floods, extreme climatic events, technological and terrorist explosions and dangerous chemical spilling. The affected area would be large and a considerable amount of property damage and affected persons would be recorded; thus, community readiness is a must. The security centre was set on special criteria to provide sheltering and living conditions for evacuated persons, being also a community disaster preparedness locus. The authors aimed at technical and institutional management tools to create an urban security zone within or closer to the community. Under a multi-hazard threat, the location and the extent of the security centre was located in the premises of a local college, for seismic or explosion hazard, and in a park or in a public place on a close hill, for flood hazard. Besides reliable buildings, tents and containers are also considered as potential sheltering spaces.

According to the number of people lost in earthquakes during 20th century as well as in a single (March 4, 1977) earthquake during this century (1574 people, including 1424 in Bucharest), Romania can be ranked the 3rd country in Europe, after Italy and Turkey. Romania is followed by the former Yugoslavia and by the Greece (Bolt 1995, Coburn and Spence 1992). The World Bank loss estimation after the 1977 earthquake (Report No. P-2240-RO, 1978) indicates that from the total loss (2.05 Billion US $) more than 2/3 was in Bucharest, where 32 tall buildings collapsed. Half of the total loss was accumulated from buildings damage. The 1977 direct loss and indirect consequences of loss mark probably the starting point of economical decay of Romania during the next decade. They also explain the present concern of civil engineers and Romanian Government for assessment and reduction of seismic risk in Romania. The World Map of Natural Hazards prepared by the Munich Re (1998) indicates for Bucharest: “Large city with Mexico-city effect”. The map focuses the dangerous phenomenon of long (1.6 s) predominant period of soil vibration in Bucharest during strong Carpathians Vrancea earthquakes. The Bucharest and Lisbon are the only two European cities falling into Mexico-city category. International experts and organizations agreed that Bucharest is the capital city in Europe characterised by the highest seismic risk. The paper presents

With a population of over 2 million inhabitants, Bucharest is considered as one of the world’s 10 most vulnerable cities to earthquakes. Several destructive earthquakes, occurring from the Vrancea seismogenic source, have hit the city in the past. According to previous studies, the particular local near surface geology of the city seems to play an important role in the site amplification phenomena recorded during strong earthquakes. In the paper, the frequency content of ground motions recorded in Bucharest during the strong Vrancea earthquakes of the last four decades is assessed analytically, based on parameters used in literature, and results are mapped and interpreted in correlation with the information obtained by in situ measurements. Conclusions are drawn, with reference to the combined effects of seismic source and of local site conditions in the analyzed area.