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8/12/2019 Presentation Athens
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ATHENS 12thof April, 2013 1
M. Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia,
Bulgaria
Bulgarian seismic design codes andcivil construction practice. Infilled RC
frames - Application and assessment of
their resistance to lateral forces
THE EUROPEAN CENTER FOR RISK PREVENTION, SOFIA, BULGARIA
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1.INTRODUCTION
Eurocode 8 and Eurocode 8 Part 3 in Bulgaria
Assessmen and retrofit programs in Bulgaria
Type of existing buildings structures.
- large panel systems
- masonry and masonry infilled structures
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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2.Bulgarian Seismic Codes and Eurocode 8 (Eurocode 8-3)
Pre 1947No Seismic Design Code
1947First Seismic Design Requirements
1957First Seismic Design CodeLow Level Seismic Design Codes
1964New Seismic Design CodeMedium Level Seismic Design Codes -
Introduction of Dynamic factors
1987Modern Bulgarian Seismic Design Code and preceding events (1977
Vrancea Earthquake and 1987 Strazhica Earthquake)
2007, 2009 and 2012 Editions
2012 - Introduction of Eurocode 8
20122014Joint Application of Codes
Post 2014Planned retirement of Bulgarian Seismic Code
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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Type of Buildings, classified by the reference Seismic Design Code at the time of design
and construction
Pre 1947 Construction
1947-1957 Construction
1957-1964 Construction
1964-1987 ConstructionMedium and high rise residential buildings. Large Panel
Systems, Lift Slab method, prestressed reinforced concrete buildings, climbing
shuttering RC system, and others. Mass construction period.
1987 Seismic Design Code
- 1990s period
- 2000-present
Comparison between the codes
Seismic Assessment of buildings designed according to Bulgarian codes
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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3.Pernik Earthquake 2012
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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3.Pernik Earthquake 2012Pernik RegionUndamaged buildings
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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3.Pernik Earthquake 2012Pernik RegionDamaged buildings
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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3.Pernik Earthquake 2012Pernik RegionDamaged buildings
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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3.Pernik Earthquake 2012Pernik RegionDamaged buildings
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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3.Pernik Earthquake 2012Sofia regionElastic Spectrum soil type C
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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3.Pernik Earthquake 2012Sofia regionDamages
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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3.Pernik Earthquake 2012Sofia regionDamages
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
A S 12th f A il 2013
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4.Assessment of masonry-infilled reinforced concrete frames and buildings
Masonry together with reinforced concrete is the most widely used material in
Bulgarian cuvil practice.
In Bulgaria masonry is used as:
Structural material
Non-structural material
Until now the effects of the infill on the behavior of the structures were usually
neglected in seismic analysis of RC/masonry buildings.
4.1Masonry-infills in Bulgarian civil construction practice
Use of masonry as primary (structural) material in combination with wood, steel etc. Use of masonry as primary (structural) material in combination with RC.
50s 60sapplication in low rise buildings with up to 4-5stories (usually 3-
4)
60spresentuse in low rise residential houses up to 2(max 3) stories high
Use of masonry as nonstructural material
60spresentapplication in low, middle and high rise buildings with RCas primary structural material (usually RC shear walls are used)
Positives of the early designs:
Usually regular buldings
Use of bricks with no openings
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
ATHENS 12th f A il 2013
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Quality control of the masonry
Conservative design
Usually low height
High safety against premature out of plane failure of the masonry
Deficiencies of the early designs:
Designed according to low-level Design codes and usually lower seismic
design acceleration
Poor detailinglack of enough transverse rebar
Use of smooth rebar steel rods.
Low-strength concrete
Unknown quality of the mortar
Possible degradation of strength due to removed internal walls.
Brittle failure is expected
Positives of later designs
Designed according to better Design codes Better detailing
Use of textured rebar steel rods (especially in the last decades)
High-strength concrete.
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
ATHENS 12th f A il 2013
8/12/2019 Presentation Athens
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Neglecting the strength of infill is often on the safe side
Better performance might be expected (especially in buildings designed
according to 1987 Seismic Design Code)
Deficiency of late designs Use of bricks with high percentage of openings
Less conservative designs
Neglecting the stiffness of infill might be dangerous
Low quality control of the masonry construction due to the understanding
that it is not important for the overall behavior of the structure.
Design and construction of irregular structures (especially after 1990) 1990s period when overall control was not strict enough
Possible premature collapse of internal masonry walls (due to lack of
connection between the frame and the masonry)
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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4.2Assessment of the behavior of in-filled RC frames
Importance
Lack of modeling techniques, prescribed in Seismic codes (either Bulgarian or
Eurocode 8)
Types of infill models: Macromodels
Bare frame
Single-strut
Double Strut
Multi-Strut
EQUIVALENT WIDTH OF THE STRUT
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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Micromodels
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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Comparison of Analysis Results
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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Nonlinear Strut Models
Importance and field of application
Data input requirements
ATHENS 12thof April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
SEISMOSTRUCT Software Package nonlinear model
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4.3 Application of infill modeling in assessment and retrofit
Linear Strut Models
ATHENS 12 of April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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4.3 Application of infill modeling in assessment and retrofit
Nonlinear Strut Models
ATHENS 12 of April, 2013
M. Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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4.3 Application of infill modeling in assessment and retrofit
Nonlinear Strut ModelsCapacity CurvesBase Shear vs. Top displacement
ATHENS 12 of April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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4.3 Application of infill modeling in assessment and retrofit
Nonlinear Strut ModelsStrengthening of existing structures
ATHENS 12 of April, 2013
M. Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
Nonlinear Micromodels
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CONCLUSIONS
1. BDS EN 1998-3:2005 Assessment and Retrofitting of Buidings is the first
complete structural code of this type in Bulgaria.
2. Contradictions between the old and the new code exist- Completely different principles
- Different definition of seismically resistant structure
3. 2012 Pernik Earthquake conclusions:
- The event in Pernik may be classified as a strong one (ref. 1987 code)
- The event in Pernik may be classified as moderate or even low
- Almost all buildings properly designed and constructed withstood the
earthquake without severe damages.
- Many of the Buildings that were constructed without proper designs and
in contradiction to good construction practices were heavily damaged.
- Some deficiencies of old local codes designs were detected.- Danger of falling non-structural elements of buildings during an
earthquake exists.
4. Masonry-infills influence the behavior of structures.
ATHENS 12 of April, 2013
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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CONCLUSIONS
5. Modeling of masonry requires a lot of information and knowledge.
6. Introduction of national application handbooks is required.
7. Many of the buildings in Bulgaria may be rated as not seismically resistant if
checked in accordance to BDS EN 1998-3:2005
8. But the last doesnt mean that they really arent.
p ,
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
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p ,
M.Eng. Velyan Petkov
The European Center for Risk Prevention, Sofia, Bulgaria
TNANK YOU FOR YOUR ATTENTION