SIMPLE/RAPID SEISMIC EVALUATION METHODS ......2018/10/02 · Seismic risk evaluation in 3 steps...

SIMPLE/RAPID SEISMIC

EVALUATION METHODS

Advanced Earthquake Engineering

CIVIL-706

Instructor:

Lorenzo DIANA, PhD

Advanced Earthquake Engineering CIVIL-706 Rapid Visual Screening

L’Office Fédérale des eaux et de la Géologie (OFEG)

Seismic evaluation through risk factors

Acknowledgment for the contribution to create the slides

2000 Seismic risk evaluation in 3 steps define priority of interventions STEP 1) Main characteristics of the building. Seismic Risk is evaluated in a simplified way using a check-list. STEP 2) analysis of buildings with high seismic risk by structural questionnaires and simplified structural analysis STEP 3) advanced seismic analysis methods based on SIA norm

FIC

HE

1 C

H-O

FEG


AZPS: damage factor

WZ: probability of collapse

RZPS = AZPS x WZ

OFEG Evaluation Sheet

FICHE 1 CH-OFEG

Risk factor

RZPS: risk factor


AZPS: personal and material damage


direct damage indirect damage

AZPS = AD x AIF = (ADS + ADP) x AIF

Indirect consequence




direct consequence



ADS: direct material damage • building value in million CHF (replacement value)

ADP: direct personal damage • mean occupancy

Number of people

Hours in day

Days in week

Weeks in year

ADP =



Examples for ADP • School building

- standard occupancy

ADP = 400 8 5 38 7

• Sports hall of the school - special occupancy

ADP = 1000 3 1 38 1.3



AIF: indirect damage Related to function class. It estimates consecutive damage due to functionality reduction.

- Production interruption, personal damage (hospital, chemical factory)

No consecutive damage (small offices, residential buildings, etc.)

Function class AIF

FK I 1

FK II 2

FK III 5

Same function as FK III but less important

Important and strategic buildings with high consecutive damage (e.g. hospital)



AZPS damage factor Example of the school:

400 8 5 38 7

20 54

WZ = WEPB x WBAU


L’Office Fédérale des eaux et de la Géologie (OFEG)

WZ: probability of collapse

• seismic zone and design year • soil class • structure

structure site



WEPB = WEP x WB WEP: seismic zone and construction year • seismic zone

-defined in the code of Swiss society of engineers and architects (SIA)

• seismic provisions -code 1970: poor until 1989: improved

• project year - design year is important, not the construction time

soil Seismic zone and year



WEPB = WEP x WB WEP: seismic zone and construction year

Seismic zone 1 2 3a 3b

design year

Before 1970 3 6 15 30

1970 – 1989 2 3 8 15

After 1989 1 1 1 1



WEPB = WEP x WB

WB: soil class of the site

• Favorable => 1 -Rigid soil classes

•Average => 2 -Neither favorable nor unfavorable

• Unfavorable => 4 - Fine or sensitive soils (clay, silt, incompact sand) - Saturated soils (water level near surface) - Unfavorable topography (slope, edge of valley) - Landslides, artificial soils



Example for WB: soil class



WBAU = 1 + WG + WA + WW + WK + WD + WF

WG: In-plane regularity and bracing

WA: In-elevation regularity and bracing

WW: Type of bracing system

WK: Building in plane shape

WD: Construction mode (ductility)

WF: Foundation

WZ = WEPB x WBAU structure site




• Favorable => 0

-Center of rigidity close to center of mass

•Unfavorable => 2 -Center of rigidity not close to center of mass

• None => 5 - No effective in-plane bracing elements



WA: Vertical regularity and bracing

• Continuous => 0 -Identical stiffness for all stories / slight differences

•Not continuous => 2 -Stiffness change (suppression of bracing or shear walls)

-Other discontinuities in force path (e.g., floors at different

levels)

• Soft Storey => 5 - storey without or with poor horizontal stiffness



WA: Vertical regularity and bracing



WA: examples of soft storey

eart

hq

uak

eret

rofi

t.o

rg




• Cores and walls => 0 High stiffness and stability e.g., elevator cores or stair cores




• Moment-resisting frames => 1 stiff systems Condition: no infill Office buildings Sport centres Factories Warehouses

Strut = puntone Tie = tirante




• Braced frames => 2 low energy dissipation potential

concentrically eccentrically




• Frames with infills => 2-4 favourable if the infill and frame are in compression; unfavourable if partially infilled




• Mix systems => 3 inhomogeneous systems: unfavourable (different bracing systems often result from renovations)

plan Structural model behavior




• Compact => 0 - uniform mode of vibration

•With Angles, long => 1 - torsion induced by the unfavorable relative position of mass and stiffness centers

- modes of vibration complex and non-uniform

- stress concentration




• Building in plane shape • Configuration of openings




• Reinforced concrete, steel, composite => 0

- Good strength (shear/compression) -High plastic deformation capacity (energy dissipation)




• Reinforced masonry => 2 - Good deformation capacity - Reasonable traction strength



• Precast => 3 - Problem with connections

MR

P E

ngi

ne

erin

g





• Wood => 3




• Masonry, unreinforced concrete

- Almost no ductile behavior - Fragile - Resists only in compression and shear

=> 3 + n or 3 + n/2

3 + n flexible slabs 3 + n/2 stiff slabs



WF: Foundation

• Continuous foundation => 0 - foundation raft

• Isolated => 1 - foundation elements not bounded (e.g., isolated footing)

- heterogeneous foundations (e.g., piles with different lengths, very heterogeneous soil)



WF: Foundation

• Continuous foundation • Isolated



Collapse probability factor

Material and human damage



Risk factor


OFEG Evaluation Sheet Example of WZ/AZPS figure

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1


OFEG Evaluation Sheet Risk reduction

• Reduction of AZPS - Change the building utilization (reducing occupancy, changing function, etc.)

• Reduction of WZ - Upgrade seismic behavior (strengthening, improving deformation capacity


Post-earthquake FICHE 1 application

Pettino – L’Aquila (AQ)

Mainly reinforced concrete buildings

Village damaged by 2009 earthquake

Ripabottoni (CB)

Mainly masonry buildings

Village damaged by 2002 earthquake


Main goals:

• Verification of FICHE 1 reliability

WZ value is compared with the damage grade and habitable safety established by AEDES form.

• Improvement of FICHE 1 – OFEG

WZ value is compared with the damage grade and habitable safety established by AEDES form.



Adjustments on markers:

WEP (seismic zone and construction year)

WB (soil class)

ADS (direct material damage)

ADP (direct personal damage)

AIF (indirect damage)

Verification of FICHE 1 reliability






Construction year

Switzerland Italy

< 1970 < 1974

1970 – 1989 1974 – 1996

> 1989 > 1996

Construction year

< 1974 30

1974 – 1996 15

> 1996 1


WB (soil class)



Switzerland (SIA 261) Italy (NTC 2008) Soil WB

Soil class A and B Soil Class A and B Favorable 1

Soil class C, D and E Soil class C, D and E Medium 2

Soil class F Soil class C, D and E where it may

occur liquefaction or landsliding Unfavorable 4

WEPB = WEP x WB






ADS (direct material damage)

For the evaluation of the direct material damage ADS, it has not been possible to refer to the insurance value of the building. The value assumed for ADP refers to the commercial value taken from www.agenziaentrate.it for the first half of 2009 (first the earthquake), converted into million Swiss francs.



WEPB = WEP x WB






ADP (direct personal damage)

For the evaluation of the direct personal damage ADP, it has been calculated the average occupancy of the buildings as assumed by NTC. For housing, the number of inhabitants has been calculated by the number of dwellings and their dimension for and occupancy of 12 hours par day.



WEPB = WEP x WB





Per la valutazione dell’indice dei danni diretti alle persone ADP, si calcolerà l’occupazione media annua riferendosi alla densità di affollamento dell’edificio secondo quanto riportato in tabella (Tabella 13). Per le abitazioni civili si valuterà il numero di occupanti dal numero di appartamenti presenti e dalla loro dimensione (ad esempio, 4 persone per un appartamento di 80 m2, con due stanze da letto), considerando un tempo di occupazione medio annuo di 12 ore al giorno.


AIF (indirect damage)



WEPB = WEP x WB





Switzerland Italy (NTC 2008) AIF

FK I: all the other

buildings

Class I: Building with random presence of people, farm buildings.

Class II: Buildings with standard crowding, not danger for the environment and without public and

social functions. Bridges, barrage and railways not considered in class III and IV.

1

FK II: buildings similar

to FK III but less

important

Class III: Buildings with significant crowding, factories danger for the environment. Roads out-of-

town not considered in class IV. Bridges and railways the interruption may cause important

emergencies. Barrages very important.

2

FK III: Hospitals, civil

protection buildings,

Police, Fireman

Class IV: Buildings with public and key functions connected to the civil protection. Factories

particularly danger for the environment. Road important for the connection between towns. Bridges

and railways very important with a key role. Barrage fundamental for aqueduct and energy

production industry.

5


Pettino – L’Aquila (AQ)

2009 earthquake

737 reinforced concrete buildings analysed



WEPB = WEP x WB







Main damages identified

Slight damages to infill mainly due to overturning of brick leafs not connected to the load bearing structures (1).

Slight vertical damages to the infill between slabs (2).

Slight damages in the connection with the structures (3).

Moderate and heavy X-cracks to the infill (4).

Verification of FICHE 1 reliability – Pettino, L’Aquila (AQ)




Moderate and heavy damage in the columns/beams joints (5).

Very heavy damages to roofs elements (6).

Very heavy damages connected to the overturning of infill (7).

Collapse of the building for soft storey (8).





Damage grades are identified by the application of AEDES form. Related to the analysis of damages to structural and non structural elements, a judgment about the safety of the building is expressed.

For this work: Buildings A, B, C, D, F are considered SAFE



A Building SAFE for occupancy

B Building TEMPORARILY NOT SAFE for occupancy that could

become SAFE with slight emergency actions

C Building PARTIALLY NOT SAFE for occupancy

D Building TEMPORARILY NOT SAFE for occupancy that needs

important actions

E Building NOT SAFE for occupancy

F Building not safe for falling external hazard





Year of construction

< 1919

‘19 – ‘45

’46 – ‘60

’61 – ’71

< 1974

’72 – ‘81

’82 – ’91 1974 – 1996

’92 – ‘01

> 2001 > 1996


WB (soil class)

Soil class is evaluated in relation with the microzone of Pettino. A local amplification factor of 2 (FA = 2) is given for all the village meaning “stable zone susceptible to local amplifications”. Though the soil of Pettino has been classed as an average soil.

WB = 2




WG (In-plane regularity and bracing)



In-plane irregularities In-plane bracing WG

None 5

Not regular mass distribution

Not regular stiffness distribution

Presence of in-plane irregularities

Unfavourable 2

Slight in-plane regularity

In-plane regularity Favourable 0


WA (Vertical regularity and bracing)



Vertical bracing WA

Vertical regularity

Vertical regularity

Medium vertical regularity Continuous 0

Not vertical regularity Not continuous 2

Soft storey

Pilotis

Absence of infill

Cantilever infill

Soft storey 5


WW (Type of bracing system)



Bracing system WW

R.C. frame with stiff infill (without big openings) 2

R.C. frame with dropped beams with not stiff infill (with widespread big openings) 4

R.C. flat plate moment frame with not stiff infill 4

R.C. frame with dropped beams on the boundary with not stiff infill and flat plate moment

frame inside 4

R.C. frame with dropped beams and R.C. core 0

R.C. Shear walls 0


WK (In-plane regularity)



In-plane regularity WK

Compact and regular plan

Medium compact and regular plan 0

Not compact or irregular plan 1


WZ Results



< 100 100 - 200 200 - 400 > 400

% buildings 22% 32% 37% 9%

0%

5%

10%

15%

20%

25%

30%

35%

40%

WZ

WZ distribution of R.C. buildings


WZ Results



< 100 100 - 200 200 - 400 > 400

% NOT SAFE 29% 32% 46% 58%

% SAFE 71% 68% 54% 42%

0%

20%

40%

60%

80%

100%

WZ

Relation safety / WZ values


WZ Results




WZ Results

• Reliability in the definition of damage scenario

• Not reliability in the definition of priorities

If WZlim = 400 - only 9% buildings for further studies or retrofitting - 87% of not safe buildings would be excluded If WZlim = 100 - 78% buildings for further studies or retrofitting - only 17% would be excluded




Ripabottoni (CB)

2002 earthquake

608 buildings analysed, mainly masonry buildings



WEPB = WEP x WB







Damages distributions

Data obtained by: • AEDES form survey (SAFE / NOT SAFE) • Direct survey (DAMAGE GRADE).

Verification of FICHE 1 reliability – Riapbottoni (CB)


67%

33%

Ripabottoni (SAFE / NOT SAFE buildings)

% SAFE

% NOT SAFE

33%

25%

14%

17%

10%

1%

Ripabottoni (damage grade)

Damage 0

Damage 1

Damage 2

Damage 3

Damage 4

Damage 5



• Not safe buildings increase with the increase of the damage grade • 14% buildings considered NOT SAFE are classed as damage 0

Verification of FICHE 1 reliability – Ripabottoni (CB)


Damage 0 Damage 1 Damage 2 Damage 3 Damage 4 Damage 5

% NOT SAFE 14% 25% 34% 56% 74% 100%

% SAFE 86% 75% 66% 44% 26% 0%

0%

20%

40%

60%

80%

100%

Relation safety and damage



• Not a clear relation between safety and height of buildings contrary to Pettino


1 storey 2 storey 3 storey > 4 storey

% NOT SAFE 32% 31% 33% 31%

% SAFE 68% 69% 67% 69%

0%

20%

40%

60%

80%

100%

Relation safety and number of storeys




• >=4 damage grade buildings decrease with the number of stories



0%

20%

40%

60%

80%

100%

1 storey 2 storey 3 storey > 4 storey

Relation damage grade and number of storeys

Damage 5

Damage 4

Damage 3

Damage 2

Damage 1

Damage 0



• Damage distribution is strictly connected to the location of the buildings (ZONE 5)



0%

20%

40%

60%

80%

100%

zone 1 zone 2 zone 3 zone 4 zone 5

Relation damage grade and zone

Damage 5

Damage 4

Damage 3

Damage 2

Damage 1

Damage 0


WB (soil class)

On site surveys showed a B soil class, class as a WB = 1. The marker does not take into account the morphology of the site that as shown by the previous tables are important for the damages distribution. E1 = zone with landslide process active E4 = zone with bad soil E5 = zone on a slope E8 = zone under a slope




< 1919

‘19 – ‘45

’46 – ‘60

’61 – ’71

< 1974

’72 – ‘81

’82 – ’91 1974 – 1996

’92 – ‘01

> 2001 > 1996


WG (in-plane regularity and bracing)

Mainly masonry building with no bracing system

WG = 5




< 1919

‘19 – ‘45

’46 – ‘60

’61 – ’71

< 1974

’72 – ‘81

’82 – ’91 1974 – 1996

’92 – ‘01

> 2001 > 1996


WA (vertical regularity and bracing)



Vertical bracing WA

Regular

- In-plane and vertical regularity

- Only vertical Continuous 0

- Only in-plane

- Not in-plane, not vertical Not continuous 2

Structural

irregularities

- Intermediate storey with bad performance bricks

- Masonry walls of upper stories with hollow bricks

- Heavy roofs

- Storey in R.C. in a masonry building

- Vertical additions in R.C.

- In-plane setbacks

- Ground floors with a lot of openings

- Masonry walls with a lot of / big openings

- Masonry walls with empty space for gas and electrical systems

- Irregularities in strengthening / strengthening only in the upper stories /not regular strengthening

Not continuous 2

Soft storey

- Ground floor with a lot of openings

- Intermediate storey with a lot of openings

- Intermediate storey with big openings

- Important out-of-plane setbacks

- Absence of spine walls

- Bad wall performances

Soft Storey 5


WW (bracing systems)

Not a clear bracing system is detectable

WW = 3




WK (in-plane regularity)



Regularity In-plane WK

- In-plane and vertical regularity

- Only in-plane Compact 0

- Only vertical regularity

- Not vertical nor in-plane regularity Re-entrant corners / long plan 1

Regolarità Forma WK

1. Planimetrica e altimetrica

3. Solo planimetrica Compatta 0

2. Solo altimetrica

4. Né planimetrica né altimetrica

Angolosa o

allungata 1


WF (foundation)

Supposed to be continuous

WF = 0

WD (ductility)

Unreinforced masonry with flexible floors

WD = 3 + n




WZ Results


<= 450 450-550 > 550

% buildings 39% 33% 28%

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

WZ

WZ distribution



WZ Results



0%

20%

40%

60%

80%

100%


WZ distribution classed by zones

> 550

450-550

<= 450


WZ Results

• Selection of WZ thresholds is based on the division of the population of buildings into three numerically comparable sets.

• There is not a clear relationship between the WZ distribution by zones and damages detected after the surveys.



0%

20%

40%

60%

80%

100%


WZ distribution classed by zones

> 550

450-550

<= 450

0%

20%

40%

60%

80%

100%

zone 1zone 2zone 3zone 4zone 5

Relation damage grade and zone

Damage 5

Damage 4

Damage 3

Damage 2

Damage 1

Damage 0


WZ Results



<= 450 450-550 > 550

% NOT SAFE 19% 44% 26%

% SAFE 81% 56% 74%

0%

20%

40%

60%

80%

100%

WZ

Relation safety / WZ values

46

193 110

126

88 45


WZ Results



0%

20%

40%

60%

80%

100%

<= 450 450-550 > 550

Relation damage / WZ

Damage 5

Damage 4

Damage 3

Damage 2

Damage 1

Damage 0


WZ Results



26%

49%

25%

0%

20%

40%

60%

80%

100%

Not safe for occupancy buildings in WZ intervals

WZ > 550

WZ = 450-550

WZ <= 450


WZ Results

• The WZ distribution is not consistent with AEDES (SAFE / NOT SAFE) survey. The FICHE 1 form is reliable in detecting the buildings with few damages but it is not reliable for the two other sets.

• The damage distribution in the three WZ sets is scattered.

• Not safe building percentage with WZ <= 450 is comparable to that with WZ > 550




NEW: AF (crowding)

• The number of stories is not considered as an important marker in FICHE 1.

• In Pettino: buildings with more stories tends to be considered as not safe for occupancy.

• In Ripabottoni: low rise buildings show important damages related to the taller ones.

• High rise buildings with low damages (grade 2 or 3) have been considered not safe for occupancy.

• Low rise buildings have been considered not safe for occupancy with higher damage grade (4 and 5).

• Tendency to assess buildings with less damages but more stories as not safe for occupancy rather than those with more damages but lass stories


Improvement of FICHE 1 reliability


NEW: AF (crowding)

AZPS = AD x AIF = (ADS + ADP x AF) x AIF



Crowding WA

Possible 1.5

Not possible 1


Changing: WEP (seismic zone and construction year)



Anno di

progetto

Zona sismica

1 2 3a 3b

< 1970 3 6 15 30

1970 - 1989 2 4 8 15

1990 - 2003 1.4 2 3 5

> 2003 1 1 1 1


Changing: WEP (seismic zone and construction year)



0

5

10

15

20

25

30

35

0 0.5 1 1.5 2

WEP

ag (m/s2)

< 1970

1970 - 1989

1990 - 2003

> 2003


Changing: WB (soil class)



Soil class Parametrs from SIA 261/2003

WB S [-] TS [sec] TC [sec] TD [sec]

A 1 0.15 0.4 2 1.0

B 1.2 0.15 0.5 2 2.5

C 1.15 0.20 0.6 2 2.1

D 1.35 0.20 0.8 2 3.6

E 1.4 0.15 0.5 2 4.0


NEW: WT (topography)

WEPB = WEP x WB x WT



Categoria Topografica WT

Level ground (slope d < 15 ° ) 1.0

Slope ( d > 15 ° ) 1.2

Ridge ( 15 ° < d < 30 ° ) 1.2

Ridge ( d > 30 ° ) 1.4


Changing: WG (In-plane bracing)



WG

In-plane bracing Rigid slabs Flexible slabs

Appropriate in both directions 0 1 (0)

Appropriate in only one direction 1 (2) 2

Not appropriate 2 3 (5)

None 5 5


Changing: WD (ductility)



Masonry WD

Good quality 2.5+n/2

Bad quality 5+n/2


Changing: WF (foundation)



Foundation WF

Continuous 0

Linear foundations not connected 0.5

Isolated 1


NEW: WS (maintenance)



Conditions WS

Good conditions 0.8

Medium consitions and slight cracks 0.9 - 1

Bad conditions and important cracks 1.2


WZ results (modified)

WB modification:

• Soil B = 2.5 for all the buildings

• Movement of the distribution towards WZ values 2.5 times bigger


<= 1125 1125 - 1375 > 1375

% NOT SAFE 19% 44% 26%

% SAFE 81% 56% 74%

0%

20%

40%

60%

80%

100%

WZ

Relation (modified WB) safety / WZ values

46

193 110

126

88 45



WT introduction:

• WT = 1.4 (zone 4 and 5)

• WT = 1.2 (zone 2)

• WT = 1 (zone 1 and 3)



0%

20%

40%

60%

80%

100%


WZ distribution (introduction WT) by zones

> 550

450-550

<= 450



WT introduction:

• WT = 1.4 (zone 4 and 5)

• WT = 1.2 (zone 2)

• WT = 1 (zone 1 and 3)

• Better relation between WZ values and safety assessment


<= 450 450-550 > 550

% NOT SAFE 8% 22% 37%

% SAFE 92% 78% 63%

0%

20%

40%

60%

80%

100%

WZ

Relation (introduction WT) safety / WZ values

8

98 72 259

20 150




5% 11%

84%

0%

20%

40%

60%

80%

100%

Not safe for occupancy buildings (introduction WT) in WZ intervals

WZ > 550

WZ = 450-550

WZ <= 450



WG modification:

• Relocation of the distribution towards smaller WZ values



<= 450 450-550 > 550

% NOT SAFE 29% 29% 47%

% SAFE 71% 71% 53%

0%

20%

40%

60%

80%

100%

WZ

Relation (modification WG) safety / WZ values

8

302 117 10

48

9



WD modification:



<= 450 450-550 > 550

% NOT SAFE 16% 34% 39%

% SAFE 84% 66% 61%

0%

20%

40%

60%

80%

100%

WZ

Relation (modification WD) safety / WZ values

30

160 189 80

98 51



WF modification:

• WF = 0.5 for all the buildings

• Movement of the buildings inside the three different classes


<= 450 450-550 > 550

% NOT SAFE 22% 32% 29%

% SAFE 78% 68% 71%

0%

20%

40%

60%

80%

100%

WZ

Relation (modification WF) safety / WZ values

20

71 214

144

100 59



WS introduction:

• Relocation of the distribution towards smaller WZ values

• Reduction in the total number of buildings belonging to WZ > 550

• Increase of the not safe to occupancy buildings percentage in WZ > 550 set


<= 450 450-550 > 550

% NOT SAFE 10% 40% 63%

% SAFE 90% 60% 37%

0%

20%

40%

60%

80%

100%

WZ

Relation (introduction WS) safety / WZ values

27

257 139

33

94

57




<= 450 450-550 > 550

% buildings 51% 22% 27%

0%

10%

20%

30%

40%

50%

60%

WZ

NEW global WZ distribution




0%

20%

40%

60%

80%

100%


NEW global WZ distribution (introduction WT) by zones

> 1375

1125 - 1375

<= 1125




<= 1125 1125 - 1375 > 1375

% NOT SAFE 7% 35% 68%

% SAFE 93% 65% 32%

0%

20%

40%

60%

80%

100%

WZ

NEW global relation safety / WZ values

21

289 88

52

47

110




41%

28%

9%

29%

26%

22%

14%

13%

17%

12%

21%

28%

4% 12%

21%

3%

0%

20%

40%

60%

80%

100%

<= 1125 1125 - 1375 > 1375

NEW global relation damage / WZ

Damage 5

Damage 4

Damage 3

Damage 2

Damage 1

Damage 0




<= 1500 1500 - 2000 > 2000

% NOT SAFE 17% 73% 80%

% SAFE 83% 27% 20%

0%

20%

40%

60%

80%

100%

WZ

NEW global relation safety / WZ values

82

395

80

30

16

4

<= 500 500 - 650 > 650

% NOT SAFE 22% 36% 80%

% SAFE 78% 64% 20%

0%

20%

40%

60%

80%

100%

WZ

OLD relation safety / WZ values

66

233

1

109

195

4

SIMPLE/RAPID SEISMIC EVALUATION METHODS ......2018/10/02 · Seismic risk evaluation in 3 steps...

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Transcript of SIMPLE/RAPID SEISMIC EVALUATION METHODS ......2018/10/02 · Seismic risk evaluation in 3 steps...