Use of combined scaling of real seismic records to obtain code-compliant sets of accelerograms: application for the city of Bucharest

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, P100-1/2006, 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.Comment: http://constructii.incerc2004.ro/Archive/2012-2/Constructii_2012_Vol.13_No.2_ID2012130206.pd

Une raison suffisante pour redéfinir l’intensité sismique: éviter des erreurs dans l’estimation de l’aléa sismique

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

Recorded Accelerograms as an Alternative Description of the Seismic Action in the P100-1/2006 Romanian Seismic Design Code

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 for structural design, i.e. a set of design Accelerograms for the application of the provisions of item 3.1.3. Recorded accelerograms” of the P100-1/2006 Romanian seismic design code. All the accelerograms thus scaled should have controlled values of the instrumental Arias-type intensity

Analysis of Accelerographic Records Obtained in Jassy During the 1986 and 1990 Vrancea Earthquakes

The interpretation, using methodological elements developed in INCERC, of data of instrumental nature obtained in Jassy during the 1986 and 1990 Vrancea earthquakes, is the main goal of the paper. The response spectra (for 12 azimuthally equidistant horizontal directions) of strong motion records, the global parameters which characterize an individual (horizontal) component of a record (effective peak values and corner (control) periods), and the instrumental intensity (global and averaged upon a frequency interval, based on destructiveness spectrum and on response spectrum) are the main numerical results obtained for the seismic records at hand. Finally, an evaluation of results, as well as conclusions useful for the aseismic design of buildings in Jassy, is presented

An attempt to recalibrate instrumental criteria for intensity assessment

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

Reconsideration of ground-level seismic records obtained in instrumented buildings: a preliminary study for strong Vrancea earthquakes

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 structure-foundation-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

Monitorizarea instrumentală a construcţiilor la cutremur

For the constructors, monitoring has common meanings with the usual terms surveillance, follow up, control etc. of the behavior of buildings determined by their location. The scientific literature uses “monitoring of the structural status”. The analysis of the behavior of different categories of constructions in case of an earthquake and the assessment of effects presumes, in addition to a detailed visual examination of the state of constructions and recording the observed damages, a series of experimental determinations in order to know the real resistance capacity of the damaged construction, establishing the consolidation solutions. In this context, determining the own oscillation periods of a building and comparing them with the original data represent a first method to globally appreciate the variation of the rigidity of a building after earthquake solicitation. The paper specifically presents the manner of using field observation data and instrumental data within the seismic network of INCERC when associated with advanced processing. The paper underlines the need for an extended instrumentation of buildings of national interest, such that information on the behavior of some structural categories could be available in a short time interval after the occurrence of an earthquake