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

15

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