risk-based seismic evaluation technical note sia 2018 · civil 706 - sia 2018 risk-based evaluation...

CIVIL 706 - SIA 2018 risk-based evaluation EDCE-EPFL-ENAC-SGC 2016 -1-

EDCE: Civil and Environmental Engineering CIVIL 706 - Advanced Earthquake Engineering

Risk-based seismic evaluation Technical Note SIA 2018


Content

•  Problematic

•  Compliance factor

•  Individual risk

•  Live-saving costs

•  Commensurability

•  Reasonableness


Example : EPFL Building GC


Example : EPFL Building GC •  Parameters

seismic zone : Z1 building class : COII response spectrum : S12 microzonage de Lausanne

•  Behavior factor: steel construction, non-ductile ⇒ q = 2.0

•  Building: construction : between 1976 and 1982 global occupancy : 49 (180 students + 120 employees)


Cross-section GC-D (building A)


Plan view GC-D (building A)


Braced frames GC-D (building A)


GC-C, GC-D (buildings B and A) •  2D modeling: response spectrum method

Direction N-S, 2 CV symmetrical, direction E-W 1 CV centered Accidental eccentricity ⇒ CV cantilever with 60% of the masses


GC-C, GC-D (buildings B and A) •  2D modeling: response spectrum method

Direction E-W 1 CV centered


GC-C, GC-D (buildings B and A) •  Compliance factor min: αeff = 0.44

Critical: bolts (diagonal connections, CV N-S)

•  Other elements: Welding joint plate-diagonal (0.55) and anchorage (0.56)

•  CV E-W: αeff = 0.64 (diagonal connections)


GC-A, GC-B (buildings D and C) •  3D modeling: direction E-W

CV irregular Accidental excentricity according to SIA 261


Transversal direction mode : T = 1.43 s


Longitudinal direction mode : T = 1.29 s


Torsion mode : T = 0.89 s


GC-A, GC-B (buildings D and C) •  Compliance factor min: αeff = 0.44

Critical: bolts (diagonal connections, CV N-S)

•  CV E-W: αeff = 0.58 (diagonal connections)


Technical note SIA 2018 •  Slides prepared by

Ehrfried Kölz and

Blaise Duvernay, OFEV


Risk-based concept

–  What can happen? (scenarios)–  How likely is it? (probability)–  What are the consequences? (losses)

iii CPR ⋅= ∑ ∑ ⋅==i i

iii CPRR

–  Definition of Risk

–  Individual and collective risk (risk to people)

–  Effectiveness of risk mitigation measures–  Earthquake safety measures (upgrading)–  Cost of measures -> SKM–  Risk reduction -> ΔRM

–  Life-saving costs [CHF / per life saved]

–  Individual risk = probability to be killed in the building which is evaluated–  Collective risk = sum of the risks of all the people in the building

M M

M R SK RK Δ =


Procedure of SIA 2018

–  Force-based method–  Displacement-based method–  SIA 2018 provides tables of information for the classification of building

materials, which were used in past decades

–  Evaluation of the structure (structural analysis)

d

deff E

R=α

d

dReff w

w ,=α

–  Compliance factor α–  measure of the compliance with the current codes

resistance

action effect

displacement capacity

target displacement

force-based method

displacement-based method


Technical note SIA 2018

d

deff E

R=α–  Compliance factor from verification :

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

Erfüllungsfaktor αeff

Ris

ikof

akto

r RF

Ris

k fa

ctor

RF

Compliance factor αeff

–  Acceptability of individual risk : P(death/yr) ≤ 1/100‘000


Damages EMS 98


EMS 98 - Definition of the intensity •  Inverted - damages


EMS 98 •  Vulnerability

classes


SIA 2018 - Individual risk •  Earthquake return periods


SIA 2018 - Individual risk •  Ranges of individual risk (1/100�000/yr)

for the vulnerability classes VK


Acceptability of individual risk –  society choice / not really regulated or normalized –  1/100�000 (10-5) per year based on experience and expert judg.

Domaine de responsabilité de la collectivité

Individual responsability domain L

imite

val

ues

for

the

mor

tal

indi

vidu

al r

isk

(per

yea

r)

SIA 2018


Individual risk (in 1/100�00 per yr)

Additional risks: 400 20 cigarettes/day 300 1 wine bottle/day 150 Motorcycling 100 Delta-plane

20 Car (20-24 years old) 10 Pedestrian 10 Household work 10 10�000 km road

5 Trekking (mountain) 3 10�000 km freeway 1 Plane accidents / flight 1 10�000 km train

0.5 Building fires 0.2 Death - earthq. (CA/US)

0.1 Lightning

Cumulated:

110 25-years old 100 35-years old 300 45-years old 800 55-years old

2000 65-years old 5000 75-years old

Professional risks:

100 Forestry work 90 Forestry industry

50 Construction 15 Chemical industry 10 Mechanical industry

5 Office work


Evaluation criteria –  Commensurability and reasonableness

0.00

0.50

1.00

10 20 30 40 50 60 70 80 90 100

Restnutzungsdauer [a]

Erf

üllu

ngsf

akto

r αeff

keine Massnahmen empfohlen

Beurteilung der Verhältnismässigkeit

Massnahmen erforderlich

? min

? adm

BWK I und II

BWK I und II

BWK III

BWK III

individual risk not acceptablemeasures required if LSCM reasonable

0.25

Residual life time

no measures recommended

individual risk acceptablemeasures required if

commensurable

Com

plia

nce

fact

or α

eff

αmin

αadm


Risk criteria for evaluation

probability to be killed < 1/100�000 per year

–  The individual risk must be acceptable

–  If the individual risk is not acceptable, the structure must be upgraded, if the life-saving costs are reasonable

–  If the individual risk is acceptable, the structure must be upgraded, if the life-saving costs are commensurable

saved life / ) Euro . Mio . ( CHF . Mio RK M 5 6 10 ≤

saved life / ) Euro . Mio ( CHF . Mio RK M 65 100 ≤


Life-saving costs – type of activities

Source: Katarisk 2003

SIA 2018: commensurability

SIA 2018: resonableness


Safety costs SKM

–  Annualized intervention costs

–  All the costs for security improvement

Investment costs [francs]MSIK

MM SIKDFSK ⋅= Safety costs [francs/year]

–  Reduced if coupled with another intervention (transformation)

1)02,1()02,1(02,0

1)1()1(

−

⋅=

−+

+= n

n

n

n

iiiDF Discount factor [1/year]

Residual life time [years]n

For SIKM = 100�000.- and n = 50 years:

SKM = 0.032 . 100�000 = 3�200 .- / year


1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 compliance factor, α eff

risk

fact

or, R

F

intα

)( intαRF

effα

)( effRF α

ΔRF = 9 . 10-6 / an

Risk reduction ΔRM –  Difference of collective risk between initial situation and the

situation after interventionPBRFRFR effM ⋅−=Δ ))()(( intαα [saved lives/yr]

Mean occupancy [pers.]Example office:50 employees8.5 hours / 245 days / 746 weeks / 52

PB = 50*8.5/24*5/7*46/52 = 11

ΔRM = 9.10-6 . 11 = 1.10-4

1 ten thousandth saved lives per year


Live-saving costs RKM - calculations

–  Ratio between measure costs and the reachable risk reduction

Safety costs [francs/year]MSK

Risk reduction [human saved lives/year]MRΔ

M

MM R

SKRKΔ

= Live-saving costs [francs/human saved live]

/saved live mio. 32 saved lives per year 10 1

year / . 200 ' 3 4 � = .

� = � M RK


EPFL Building GC : SIA 2018 assessment •  Individual risk

αeff = 0.44 > 0.25 = αmin ⇒ OK, measures required if commensurable

•  Commensurability (till αint = 1.0): PB = 49 ΔRF = 4·10-6– 5.8·10-7 = 3.42·10-6

ΔRM = 49·3.42·10-6 = 1.68·10-4

RKm = 10·106 [Fr./life saved] SKm = 10·106·1.68·10-4 = 1680 [Fr./year] n = 40 years DF = 0.037 ⇒ SIKm max. = 1680/0.037 = 45'400 [Fr.]


Conclusions

•  Compliance with the requirements in the codes for new buildings is desireable but not mandatory

•  Risk-based principles for adequate evaluation of existing structures

•  Cost-benefit principles

•  Prevention of loss to life and limb highest priority

risk-based seismic evaluation technical note sia 2018 · civil 706 - sia 2018 risk-based evaluation...

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