Numeričko modeliranje interakcijekonstrukcijeitlau ... Numeričko modeliranje...
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Numeričko modeliranjeinterakcije konstrukcije i tla uzemljotresnom inženjerstvu:
DEO 1. ZEMLjOTRES
17.09.2020
dr Željko Žugić, dipl.inž.građ, naučni saradnikVlada Republike Srbije,
Kancelarija za Upravljanje Javnim Ulaganjima
PRESENTATION OUTLINE
Motivation
Seismic intensity measures
Seismic site (local soil) response
Sensitivity and probabilistic analysis
Numerical modeling issues
Conclusions
Motivation
Several ongoing first‐class importance projects in Serbia (hospitals, infrastructure…)
Transition period from SRPS to Eurocode (EN norms)
Recent strong Earthquakes in region (Croatia, Albania…)
Insurance company and society requests
EARTHQUAKE ‐ SOIL – STRUCTURE (1) Probabilistic seismic hazard analysis;(2) time histories development; (3) seismic ground response analysis; (4) soil foundation-structure interaction
EACH “LEG” IS IMPORTANT!!!
HOW WE MEASURE SEISMICITY???
Different for slope problems and liquefaction problems !!!
Different for Urbanism and planning purposes and particular site location (bridges, dams…)
Which Intensity Measure is optimal? The answer is problem-dependent!!!!
IMs general classification
Acceleration basedVelocity basedDisplacement basedHybrid
Official seismic hazard maps in Serbia
THE MOST IMPORTANT IS PROPER SELECTION OF REALISTIC SEISMIC MOTION!!!!
PhD THESIS PUBLIC DEFENSE University Ss. Cyril and Methodius in SkopjeInstitute of Earthquake Engineering and Engineering Seismology (UIM‐IZIIS) ‐ Skopje
Natural Artificial (synthetic)
Scaling in terms of
Intensity Frequency content
Spectrum matching: The amplitude scaling and/or frequency modification of a seed ground motion to match a target spectrum over a user-specified period range
Magnitude range of anticipated significant event(s)
Distance range of the site from te causative fault(s)
Site condition (site geology Vs30)
Basin effect (if basin exist)
Directivity effect
HOW TO “OBTAIN” PROPER SEISMIC TIME HISTORY RECORD ???
MODEL OF ACCURATE SEISMIC SITE (LOCAL SOIL) RESPONSE
+ BASIN AND SLOPE EFFECTS
SIMPLIFICATION IN TERMS OF SOIL CLASIFICATION
Quantifying uncertainties in soil properties
Inherent soil variability
In-situ soil properties may vary vertically and horizontally for a variety of reasons, including:
Depositional environment Degree of weathering Physical environment
Basic terms:
TrendApproximated regular distribution of properties with depth due to effective confining pressure
Scale of fluctuationDescribes the spatial fluctuation of the property of interest about the trend
IMPORTANCE OF ACCURATE SEISMIC SITE (LOCAL SOIL) RESPONSE
It is not only about cumulative (total) loss value!!!The “simplifying” can lead us to unconservative results On “local soil” level we can act!!!!
LACK OF SOIL INVESTIGATION WORKS!!!LACK OF SYSTEMATISED AND HARMONISED DATA !!!
Local soil response map in Serbia
Probabilistic computation methods
Monte Carlo simulations
Reliability methods FOSM,FORM,SORM
Event tree analysis
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In case of absence of valuable records from previous seismic activity certain assumtpions need to be made:
20 spectrum compatible records EC8, type 20 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
0
0.5
1
1.5
2
2.5
Period (s)
Resp
onse
Spe
ctra
(m/s2 )
Average difference absolute value= 7.99%
EC8- reference spectrumAverage response spectrum
0 0.5 1 1.5 20
1
2
3
4
5
Period (s)
Resp
onse
Spe
ctra
(m/s2 )
Tornado diagrams – useful tool for sensitivity analysis
Structural engineering Geotechnical engineering
METHODOLOGY FOR PROBABILISTIC PERFORMANCE BASED SEISMIC SLOPE STABILITY FOR REGIONS WITH LOW TO MODERATE SEISMICITY
Sensitivity analysis and logic trees analysis THE MOST SENSITIVE input parameter seismic record
+2
+1
mean
-1
-2
thththththththththththththththththrdndstthththththththththththththththththrdndstthththththththththththththththththrdndst
Case 1 PGA=0.064g
Umka Duboko landslide
Percentile rankRecord Displacement(cm)
Rec. No.12 0 95% 20
Rec. No.13 0 90% 19
Rec. No.20 0 18
Rec. No. 7 0 17
Rec. No.16 0,002 25% 16
Rec. No.17 0,094 15
Rec. No.2 3,3 14
Rec. No.10 4,4 13
Rec. No.5 5,9 12
Rec. No. 18 6,4 50% 11
Rec. No.19 12,0 10
Rec. No.15 20,2 9
Rec. No.6 39,4 8
Rec. No.8 39,6 7
Rec.No 4 58,8 25% 6
Rec.No 9 89,1 5
Rec. No.11 91,9 4
Rec. No.1 109,5 10% 3
Rec.No 3 129,3 5% 2
Rec. No.14 181,2 1
thththththththththththththththththrdndst
+1,6
mean
-1,6
Sensitivity analysisand 3 branches event tree analysis
5 branches event treeanalysis
Sensitivity Analysis
Probabilistic Analysis
Case study landslide “Umka‐Duboko”
Landslide displacement (cm)
APLICATION OF SEISMIC MOTION TO NUMERICAL MODEL
For dynamic structural/geotechnical analysis the “basic package” of seismic load input is inadequate without selecting proper seismic records (realistic seismic motions)
The improving the structural and soil models should be followed by improving seismic input data at local (geotechnical) and large (geological) scale
Local soil conditions have very significant role in case of low to moderate earthquakes
Conclusions