The first part of this paper is an overview of various
methodologies for seismic-geotechnical hazard zonation that conform to the
recommendations of International Society for Soil Mechanics and Geotechnical
Engineering (ISSMGE, 1999). The purpose of this review is to illustrate the
variety of methodologies currently in use for preparation of seismic hazard
maps and to evaluate basic principles of zonation for different purposes and at
different scales. In the second part of the paper, input data for seismic
microzonation are discussed. Promulgated seismic regulations are a prerequisite
for delineation of seismic hazard zones. Guidelines and recommendations for
seismic microzonation should be incorporated into seismic regulations. There
are two principal approaches to earthquake loss mitigation; one relates to land
use management, and the other deals with the design and construction of
individual buildings. Both approaches must be considered as components of urban
planning and building design, and the application and use of these approaches
should be required and enforced by municipal authorities.
Keywords: seismic
hazard, seismic microzonation, landslide, liquefaction, land use management
[PDF]
The paper describes some recent applications of the
measurements of ambient vibrations (microseismic noise) in Croatia. They include
free-field measurements, as well as those done within buildings. Data obtained
in the field at the studied localities are consistent with the properties of
shallow geological structures known to exist there. In Zagreb,
Horizontal-to-Vertical Spectral Ratios (HVSR) indicate thick alluvial cover
(over 100 m) that gradually gets thinner towards the slopes of the Medvednica
Mt. A similar situation – on a smaller scale – is also encountered in Ston, where HVSR profiles reveal several tens of meters
thick sedimentary cover over the bedrock which gets exposed at the Bartolomija hill. Analyses of records from Ston and Dubrovnik suggest that soil-building resonance must
be seriously considered. Measurements in the buildings were analysed by a newly
developed software package FREDA – a suite of Matlab
routines. Based on tests on synthetic and real data it is concluded that
spectral methods are in general more robust and less dependent on parameters of
the algorithm employed, than time-domain analyses. Spectral algorithms are also
better in resolving higher modes. Applications to real buildings proved that
analyses of shaking induced by ambient vibrations in most cases lead to well
constrained, reliable, and time independent estimates of frequencies and damping
of the buildings’ vibrational modes for small excitation levels.
Keywords: ambient vibrations, microtremors, HVSR,
soil-building resonance
In 1998 and 2004, two strong earthquakes shook the NW
region of Slovenia. On the basis of a detailed inventory, the damages to
structures were classified into five damage grades, defined in accordance with
the European Macroseismic Scale (EMS). After both earthquakes, extensive
geological and geophysical investigations were carried out, including
geological mapping, the excavation of 60 pits, drilling of 20 boreholes down to
depths of 20 m, seismic measurements, geo-electrical measurements and seismic microtremor investigations. Since 1990, local seismic
effects in Slovenia have been addressed through consecutive rules covering
static calculations for the structures being built; the first of these rules
was the old Slovenian regulation (Uradni list SFRJ
31/81), and the other two were the last Eurocode 8 (EU8-94 and EU8-SIST EN
1998-1:2005) regulations.
In this report, we describe studies on how local
ground conditions increase seismic effects on structures. On the basis of
mentioned data in previous paragraph, we attempted to establish how reliably
this influence can be defined. A forecast of local seismic effects was compared
with actually established damage to structures. A statistical analysis was
conducted in 27 selected areas (settlements) with similar geological
conditions.
Through a comparison of ground-type impact assessments
performed using geological mapping and drilling, geo-physical measurements and
measurements of microtremors with actually established damage to structures, it
was found that forecasts were more reliable if they were made with proper
consideration of all relevant factors together. However, despite implementing
forecasts using this type of multidisciplinary approach, the forecasts for some
areas can be completely incorrect in terms of seismic effects. The best
forecast was found to be produced using the last EU8 (EU8-SIST EN 1998-1:2005), while the
old Slovenian (Uradni list SFRJ 31/81) and
first EU8 (EU8-94) regulations
produce less reliable results.
Keywords: earthquakes
in NW Slovenia, European Macroseismic Scale, Eurocode 8, ground types,
earthquake damage assessment, forecast of local seismic effects
[PDF]
5. Santucci de Magistris, F.: Beyond EC8: The new Italian
seismic code.
The 2002 Molise earthquake, which was defined by
seismologists as a normal event in the geodynamics of the Italian peninsula but
had an international resonance due to the collapse of a primary school,
triggered a series of research initiatives in earthquake engineering and
significant modifications to building codes in Italy. The modifications were
completed at the beginning of 2008 with the release of a new comprehensive
building code for Italy. This document was mainly inspired by Eurocode, but it
contains some changes and improvements.
In this paper, comments are made on three specific parts of the new code: definition of seismic action, analysis of liquefaction and analysis of slope stability. For the first part, seismic action is defined based on a recent careful study of the seismic hazard in Italy. For liquefaction analysis, some developments are given, keeping the same structure used in Eurocode. Finally, for slope stability, improvements are introduced to avoid overestimation of pseudostatic forces in conventional analyses.
Keywords: geotechnical
characterization, liquefaction, local seismic response, slope stability, seismic
code
[PDF]
6. Kvasnička, P., L. Matešić
and
K.
Ivandić: Geotechnical site classification and
Croatian National Annex for Eurocode 8.
One of the challenging tasks for Croatian accession to
the European Union is the completion of the National Annex to Eurocode 8 (EC
8) that calls for the development of national seismic hazard maps. These maps
need to be developed for several return periods (probabilities of exceedance) and should consider both bedrock and soil
conditions. The latter is especially challenging as it calls for site
characterization at a microzonation level, i.e., site characterization based
upon VS,30, SPT blowcounts, and undrained shear
strength, information available only in the departments of Public Works of
major cities. In this paper, the authors discuss several shortcomings
associated with the EC 8 ground type definitions and propose their revision.
The authors also present the ongoing work for preparation of the Croatian National
Annex to EC 8 and explain the rationale for the improvement of EC 8 ground type
definitions.
Keywords: site response, ground types, Eurocode 8
[PDF]
7. Matešić, L.,
P. Kvasnička and S. Mihalić: Importance of data and process management in Eurocode
7 – based design.
This paper describes how a geotechnical database may
be generated from the information system (IS) of a geotechnical consulting
company established in compliance with the ISO 9001, ISO 17025 QMS standards
and Eurocode 7. The application of these principles is illustrated using a
geotechnical consulting company Geokon of Zagreb,
Croatia as an example. An overview of Geokon’s
geotechnical data management system is presented by describing the procedures
for data input, maintenance, use, expansion and upgrade. Included in this paper
are relevant flow charts and a hierarchy of both geotechnical databases and
other databases.
Keywords: data
management, document flow, geotechnical database, ISO 9001, ISO 17025, Eurocode 7
[PDF]
8. Rainieri,
C. and G. Fabbrocino: Operational
modal analysis for the characterization of heritage structures.
Assessing and reducing the seismic risks associated
with historical structures require an appropriate knowledge of structural
behaviour and characteristics, as suggested by recent national and
international guidelines concerning cultural heritage. However, historical
structures are characterised by a high level of uncertainty, which affects material
properties and structural schemes and is related to deterioration processes or
previous interventions and structural modifications. The level of knowledge can
be increased by experimentally evaluating a structure's dynamic properties, and
the resultant data can be used to refine and update numerical models that are
representative of the real structural behaviour. Moreover, the periodic
monitoring of relevant parameters can help identify eventual deterioration
phenomena. Thus, dynamic tests, in conjunction with model updating, are
becoming reliable tools for non-destructively assessing historical structures.
In this article, a brief discussion of the basic principles of dynamic
identification under operational conditions is presented. Two tests with historical
structures are then presented, and the main results are reported. The high
performance of operational modal analysis techniques and the interesting
opportunities these techniques provide for the structural assessment of
historical structures are discussed.
Keywords: heritage structures, ambient vibration tests, operational modal analysis
[PDF]
9.
Conte, C., C. Rainieri,
M. A.
Aiello and G.
Fabbrocino: On-site assessment of masonry vaults: Dynamic tests
and numerical analysis.
This paper concerns the structural identification of
historical masonry buildings with reference to a case study, which is discussed
in detail. The building is located in Southern Italy (Lecce). It has an ancient
vaulted roof that is complex and commonly found in old masonry structures. This
study takes advantage of extensive historical and structural investigations of
the building. Preliminary activities have been conducted to obtain information
about the current state of the structure including the geometry, morphology,
structural details, material properties, prior interventions, and existing
damage. This process was supported by an historical investigation into the
conceptual background and construction methods used to build the structure.
After the historical investigation, a series of experiments, including dynamic
tests, were conducted on a number of the vaults to determine their dynamic
response characteristics under operational conditions. A numerical model was
also determined. In this paper, the primary dynamic test results and modelling
assumptions are reported. Comparisons between numerical and experimental
results are discussed.
Keywords: heritage structures, ambient vibration
tests, Operational Modal Analysis
[PDF]
10.
Mandić, R.,
G. Hadži-Niković
and S. Ćorić: Investigation of the
behavior of the cable-stayed bridge under test load.
A field load testing is an effective method
for understanding the behavior and fundamental characteristics of cable-stayed
bridges. This paper presents results of the behavior of the reconstructed cable-stayed
bridge over river Danube in Novi Sad under test load. The bridge was built
between 1976 and 1981 and in 1999 was heavily damaged by two Tomahawk missiles.
In 2003 process of the reconstruction began and at the end of 2005 Faculty of
Civil Engineering, University of Belgrade was invited to test reconstructed
bridge structure. The results of static load testing presented herein include
displacements, rotations and strains of the 351 m long main girder. Vibrations
of the bridge were obtained by impact load produced by heavy truck passing the
bridge and the time history response of vertical accelerations was recorded.
The frequency content of the signals was determined using Fourier
transformation and five flexural natural periods were extracted. The geological
structure and engineering properties of the soil are also given. A finite
element model of the bridge was made and a good agreement is achieved between
the experimental and analytical results. These results have shown that the
bridge is in the elastic state under the code-specified serviceability load,
which indicates that the bridge has adequate load-carrying capacity and can be
put safely into service.
Keywords: cable-stayed
bridge, experimental analysis, numerical analysis
[PDF]
11. Abolmasov, B.,
M. Jovanovski, P.
Ferić and
S. Mihalić: Losses due to historical earthquakes in the Balkan region:
Overview of
publicly available data.
This study analyzes catastrophic losses due to
earthquakes in the Balkan region. Analysis is based on the following data on
earthquakes, collected from the OFDA/CRED International Disaster Database (Université Catholique de Louvain,
Brussels, Belgium) for 1900 to 2010: numbers of fatalities, size of the
affected population and costs of material damages. Catastrophic losses were
caused by 62 earthquakes in countries within the region: Slovenia, Croatia,
Bosnia and Herzegovina, Montenegro, Albania, Serbia, Romania, Bulgaria,
Macedonia and Greece. The analysis shows that a significant number of people in
the Balkan region were killed (4,974) or were affected (2,033,723) by the
earthquakes and that many countries suffered significant material damages
(10,410.16 million USD) during the analyzed period. The main disadvantage of
using publicly available sources is the lack of consistent data on earthquake
damages. A brief review of the most catastrophic earthquakes recorded in
databases through the last 110 years is given, based on the data from publicly
available databases.
Keywords: Balkan region, catastrophic earthquakes, natural disasters databases
[PDF]
12. Rožić, N., I. Razumović and I. Nazifovski: Modelling of the recent crustal movements at the
territory of Croatia, Slovenia and Bosnia and Herzegovina.
The paper presents the results of determining vertical
displacements of the Earth’s crust at the territory of Croatia, Slovenia, and Bosnia
and Herzegovina on the basis of the data obtained in the process of
establishing geometric levelling networks of the highest order of accuracy.
These are the networks of the Austrian precise levelling, I. levelling of high
accuracy and II. levelling of high accuracy that was
established successively within the period of about 100 years (1874-1973). In
accordance with the hypotheses made and the selected methodology for defining
the displacements, a concrete numeric quantification of displacements has been
obtained, the size and the direction of Earth's crust displacements have been
determined and their characteristics and empirical parameters of behaviour
indicated. It is shown that bench mark displacements are of significant amount
as related to the measurement accuracy of height differences in levelling
networks and that long-wave and short-wave component of their variation can be
noticed in correlation with the positional distribution of bench marks. The
displacements have been modelled by means of so called grid models created by
the combination of the regression modelling and the minimal curvature surface
modelling. Thus, on the basis of modelled vertical displacement values the
speed of uniform vertical crustal movements has been determined. In spite of
the fact that a very simple methodology of displacement and movement
determination has been used, that is based on the absolute heights of identical
bench marks positioned in various epochs – networks, the obtained results
present an adequate starting point for the selection and application of more
sophisticated methodologies in determining and modelling of displacements in
the forthcoming research, i.e. the starting point that enables
interdisciplinary explanation of geodynamic processes leading to the changes in
the shape and geometry of the Earth’s crust at the observed area.
Keywords: recent crust movements, vertical movements,
bench marks, levelling networks, grid model
[PDF]