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The main objective of the National Seismic Network for Constructions, operated by the National Institute for Research and Development in Constructions, Urban Planning and Spatial Territorial Development “URBAN-INCERC”, is the monitoring of situations generated by earthquakes or other dangerous sources of vibrations induced in constructions on the entire Romanian territory. The NIRD URBAN-INCERC seismic records obtained in-situ and on buildings were and are extremely important for designers, especially in 1977, 1986 and 1990. It is the largest network in Romania, consisting of some 60 digital acceleration recorders distributed in Bucharest and in the country. This network is strategic from the population safety point of view. Due to the specific seismic hazard and vulnerability, our country shall be in preparation for the impact of a possible earthquake, which cannot be predicted in time domain, but it is possible to occur anytime. To prevent and mitigate negative consequences of such an event, urgent actions are required to ensure structural safety. Given the facts, Romania is in a critical time on strategic options regarding the seismic risks.

Currently, a large number of seismic records, obtained over the years on instrumented buildings with various heights, located in urban environment, are available at global scale. The valorization of these records is important, as frequently no other information exists for the corresponding or neighboring locations. Several studies carried out recently have shown that the influence of the building can be separated, if certain characteristics of the structurefoundation- soil system are known. The paper presents the first results of an investigation concerning the usability of seismic records obtained in the past on stations located on buildings from densely urbanized areas in Romania. The reconsideration of the information provided by these stations could provide new perspectives on the spatial distribution of the ground motion parameters for the past earthquakes and, implicitly, a better understanding of the characteristics of seismic hazard in Romania. [ABSTRACT FROM AUTHOR]

The main objective of the National Seismic Network for Constructions, operated by the National Institute for Research and Development in Constructions, Urban Planning and Spatial Territorial Development "URBAN-INCERC", is the monitoring of situations generated by earthquakes or other dangerous sources of vibrations induced in constructions on the entire Romanian territory. The NIRD URBAN-INCERC seismic records obtained in-situ and on buildings were and are extremely important for designers, especially in 1977, 1986 and 1990. It is the largest network in Romania, consisting of some 60 digital acceleration recorders distributed in Bucharest and in the country. This network is strategic from the population safety point of view. Due to the specific seismic hazard and vulnerability, our country shall be in preparation for the impact of a possible earthquake, which cannot be predicted in time domain, but it is possible to occur anytime. To prevent and mitigate negative consequences of such an event, urgent actions are required to ensure structural safety. Given the facts, Romania is in a critical time on strategic options regarding the seismic risks. Presently, a urgent necessity is the seismic network function in order to get as much as possible strong-motion data for advanced research and to understand why damages in buildings occurred. The next goal is to have more parametric and spectral data for engineering design, as well as to improve the zoning maps, having more stations at reduced distances. If possible, strong-motion micro-zonation data would explain some specific shaking differences, as a future option for local arrays. The paper presents the necessity, means and requirements of achieving a holistic and integrative concept for the national seismic network of constructions, taking into account geological settings, environmental and local soil conditions on regional profiles, attenuation patterns, architectural and structural patterns, and number of seismic stations in specific seismic zones. Also, a case study of building seismic instrumentation in Bucharest according to the Romanian Seismic Design code, indicative P100-1:2013. [ABSTRACT FROM AUTHOR]

The authors contributed during a quite long period of time to the development of comprehensive and flexible system of estimating seismic intensity on the basis of instrumental (accelerographic) data on earthquake ground motion. The system makes it possible to determine for a record, according to needs, global intensities, intensities corresponding to definite frequencies, intensities averaged upon a spectral band, continuous or discrete intensity spectra. Moreover, the intensity measures developed may rely, according to choice, on different outcomes of processing of primary instrumental data. A problem to which the paper is devoted is represented by the calibration of an important parameter, namely the logarithm base adopted in view of conversing instrumental information to intensity measures. After the attempts of the past, new sources are used this time to solve the problem. Alternative solutions are examined and discussed in this view. [ABSTRACT FROM AUTHOR]

The SP VRANCEA NT Database (Strong Earthquakes with Epicenters in the Vrancea Seismogenic Zone - Records at Ground Level) contains results obtained by the processing of Vrancea ground level seismic motions recorded from the seismic networks of Romania (INCERC, INCDFP and ISPH-GEOTEC), Bulgaria and Republic of Moldova. The equations of definition and the computed values of peak ground acceleration, peak ground velocity and peak ground displacement - as well as their "effective" values, corner (control) periods, Tc (velocity / acceleration) and Td (displacement / velocity), response spectra and instrumental intensity spectra are provided. The SP VRANCEA NT Database can be accessed from the NRDI URBAN-INCERC website (www.incd.ro), by clicking the link "RNSC" or, alternatively, by directly using the web address www.incerc.ro. The link to the database is displayed on the first page ("Database of information and seismic records RNSC URBAN-INCERC"). In order to access the database, signing in (with name, e-mail, phone and, optionally, remarks) is required. The user can then download the database file (SPVRANT.zip) and the corresponding user manuals (GHIDNT.zip). [ABSTRACT FROM AUTHOR]

A recently proposed method for scaling real accelerograms to obtain sets of code-compliant records is assessed. The method, which uses combined time and amplitude scaling, corroborated with an imposed value of an instrumental, Arias-type intensity, allows the generation of sets of accelerograms for which the values of the mean response spectrum for a given period range are not less than 90% of the elastic response spectrum specified by the code. The method, which is compliant with both for the Romanian seismic code, P1 00-1/2006, and Eurocode 8, was described in previous papers. Based on dynamic analyses of single-degree-of freedom (SDOF) and of multi-degree-of-freedom (MDOF) systems, a detailed application and assessment of the method is performed, for the case of the long corner period design spectrum in Bucharest. Conclusions are drawn on the advantages of the method, as well as on its potential improvement in the future. [ABSTRACT FROM AUTHOR]

The object of the paper is represented by an attempt to contribute to an adaptation of the concept of seismic intensity to the needs of engineering activities. A first condition in this connection is to pay the attention due to the spectral contents of ground motion. A case where rough approaches have led to erroneous estimates of ground motion severity, resulting in erroneous hazard estimates is presented. The main conclusion derived is represented by the strong need to specify the spectral interval for which macroseismic data are relevant and, as a consequence, to consider (and even to define) seismic intensity derived from post- earthquake surveys as related to a certain spectral interval. A methodology proposed in order to define and determine seismic intensity on the basis of instrumental data and, moreover, to define and determine seismic intensity spectra is then presented. Some illustrative examples are given. [ABSTRACT FROM AUTHOR]

The frequency-dependent spectrum based seismic intensity, also called instrumental intensity, is calculated basically from the integration of the square values of spectral acceleration ordinates. The values of the instrumental intensity are calibrated to match the values of the EMS-98 intensity scale, providing a promising analytical indicator for estimating the destructive potential of earthquakes. Previous studies have shown that the proposed index could be used as a basis for the development of a new improved seismic intensity scale. The paper presents a set of maps describing the spatial distribution of instrumental intensity ordinates for three seismic events recorded in 1986 and 1990. These events, generated by the Vrancea source, are the strongest earthquakes in Romania for which accelerographic data was recorded at multiple stations. Intensity maps were generated for separate significant frequency bands, in order to reveal the destructiveness of the considered earthquakes for different building categories. Results were compared and correlated with previous studies on Vrancea earthquakes and with information provided by building damage reports from the considered earthquakes. [ABSTRACT FROM AUTHOR]

A combined method of scaling the recorded accelerograms (in the range of the dominant spectral amplification periods, followed by a scaling in the field of accelerations amplitude) was developed in order to obtain: accelerograms requiring the structure to be designed, a set of design accelerograms for the application of the provisions of item "3.1.3. Recorded accelerograms." of the P 100-1/2006 Romanian seismic design code; all the accelerograms thus scaled should have an instrumental Arias type intensity of the controlled values. [ABSTRACT FROM AUTHOR]

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