This document compares two approaches for seismic damage assessment: instrumental intensity and damage index. Instrumental intensity provides concise damage assessments that generally agree with actual recorded damage, but does not differentiate well based on structure type or seismic code. The damage index approach allows evaluation of actual or required structural overstrength given the seismic design level, though it requires specifying overstrength and ductility in the direct approach. Both provide useful information, but each approach has limitations that the other complement.

1. DAMAGE INDEX VS. INSTRUMENTAL INTENSITY:
A COMPARISON OF
TWO DIFFERENT APPROACHES
IN SEISMIC DAMAGE ASSESSMENT
Iolanda-Gabriela CRAIFALEANU
Technical University of Civil Engineering Bucharest, Romania
& National R&D Institute “URBAN-INCERC”, INCERC Bucharest Branch
i.craifaleanu@gmail.com, iolanda.craifaleanu@utcb.ro
Ioan Sorin BORCIA
National R&D Institute “URBAN-INCERC”, INCERC Bucharest Branch
isborcia@incerc2004.com, isborcia@yahoo.com

2. PPT available at:
Iolanda-Gabriela CRAIFALEANU, Ioan Sorin BORCIA
DAMAGE INDEX VS. INSTRUMENTAL INTENSITY:
A COMPARISON OF TWO DIFFERENT APPROACHES
IN SEISMIC DAMAGE ASSESSMENT
DEFINITIONS
INSTRUMENTAL INTENSITY – intensity based on destructiveness spectrum (Sandi,
1987, Sandi et al., 1998)
( )
i d (ϕ) = log7,5 ∫ w a (t , ϕ, 0,05 ) dt + 6,45
2
wa(t, ϕ, ξ) = (absolute) acceleration (m/s2) for a pendulum of nat. freq. ϕ (Hz); ξ = damping ratio
id(ϕ) is calibrated to match the values of the EMS-98 intensity scale
to assess the destructiveness on separate frequency bands, id(ϕ) was averaged
upon spectral bands, (ϕ', ϕ")
  dϕ  
i d * (ϕ' , ϕ" ) = log7,5 
1
(
ln(ϕ" , ϕ') ∫  ∫
)
w a (t, ϕ, 0,05 ) dt
2
ϕ 
 + 6,45
  
PARK-ANG DAMAGE INDEX (Park & Ang, 1985)
(
DM ⋅ µ mon = µ max + β E H Fy u y )
EH = hysteretic energy; Fy = yield strength; uy = yield deformation; β = constant depending on structural
characteristics, mon = monotonic ductility, max = max. ductility
DM = 0.2 upper limit of insignificant damage; DM = 0.5 upper limit of
repairable damage; DM= 0.5…1.0 severe, non-repairable damage;
DM > 1.0 occurrence of structural collapse
In the study, DM was computed for specified values of mon and of Cy=Fy/G
DM values were averaged on the same spectral intervals as id(ϕ)

3. PPT available at:
Iolanda-Gabriela CRAIFALEANU, Ioan Sorin BORCIA
DAMAGE INDEX VS. INSTRUMENTAL INTENSITY:
A COMPARISON OF TWO DIFFERENT APPROACHES
IN SEISMIC DAMAGE ASSESSMENT
INSTRUMENTAL INTENSITY & P-A INDEX DAMAGE MAPS
AUGUST 30, 1986 VRANCEA EARTHQUAKE (Mw = 7.1, h = 133 km)
Maps of values averaged on the T=0.35…0.5 s spectral band
Park-Ang
Instrumental
damage index
intensity Cy=0.20, µmon=6
Spectral bands Spectral bands
0.25…0.35s 0.25…0.35s
0.35…0.50s 0.35…0.50s
0.50…0.70s 0.50…0.70s
0.70…1.00s 0.70…1.00s

4. PPT available at:
Iolanda-Gabriela CRAIFALEANU, Ioan Sorin BORCIA
DAMAGE INDEX VS. INSTRUMENTAL INTENSITY:
A COMPARISON OF TWO DIFFERENT APPROACHES
IN SEISMIC DAMAGE ASSESSMENT
ANALYSIS OF DAMAGE FOR CHARACTERISTIC BUILDING TYPOLOGIES
The study was performed with Structural Structure No. of Height Code Typology
reference to the 30.08.1986 Vrancea system type stories (stories) level code
earthquake R.C. frames RC3.1 4…7 MR LC RC3.1-MR-LC
with regular MC RC3.1-MR-MC
Building typologies: blocks of flats, unreinforced
8…10 HR LC RC3.1-HR-LC
masonry
based on standard designs, infill walls MC RC3.1-HR-MC
1963 – 1986 Concrete RC2 4…7 MR LC RC2-MR-LC
shear walls MC RC2-MR-MC
1960 -1977: > 90% of the new
constructed residential buildings 8…10 HR LC RC2-HR-LC
were based on standard designs MC RC2-HR-MC
…1989 Precast RC5 4…7 MR LC RC2-MR-LC
concrete MC RC2-MR-MC
today: standard blocks of flats = tilt-up walls
8…10 HR LC RC2-HR-LC
major part of the urban housing (Precast
panels) MC RC2-HR-MC
stock in Romania
Seismic intensity according to Romanian code:
12 reinforced concrete structure City
typologies, based on RISK-UE P13-63* P13-70 P100-78
typologies (Mouroux & Brun, 2006) Bucharest 7 7 8
Barlad 8 8 8
Analysis for 3 representative cities in
Focsani 9 9 9
Romania
P13-63: first compulsory seismic code in Romania (1963)
P13-

5. PPT available at:
Iolanda-Gabriela CRAIFALEANU, Ioan Sorin BORCIA
DAMAGE INDEX VS. INSTRUMENTAL INTENSITY:
A COMPARISON OF TWO DIFFERENT APPROACHES
IN SEISMIC DAMAGE ASSESSMENT
ANALYSIS OF DAMAGE FOR CHARACTERISTIC BUILDING TYPOLOGIES
Instrumental Bucharest, Focsani,
INSTRUMENTAL INTENSITY APPROACH intensity INCERC, NS Hotel, EW
Id component component
Class EMS-98
Damage assessment based on the
Bucharest
Vulnerab.
P100-78
P100-78
Focsani
P13-63
P13-70
P13-63
P13-70
Structure Typology
averaged intensity values (rounded to type code
the nearest integer*), according to
vulnerability classes in EMS-98 R.C. frames RC3.1-MR-LC D
7.45 8.01
1F 1F - 2F 2F -
with regular RC3.1-MR-MC E 1F 1F - 2F 2F -
* this led to uniform damage values in the unreinforced RC3.1-HR-LC D 1F 1F - 2F 2F -
adjacent table masonry RC3.1-HR-MC E
7.39 8.06 1F 1F - 2F 2F -
infill walls
Buildings designed according to R.C. shear RC2-MR-LC D 6.93 8.15 1F 1F - 2F 2F -
walls RC2-MR-MC E 7.15 8.33 1F 1F - 2F 2F -
P13-63 and P13-70 codes: RC2-HR-LC D 7.46 8.39 1F 1F - 2F 2F -
a few buildings in Bucharest would RC2-HR-MC E 7.45 8.01 1F 1F - 2F 2F -
Precast R.C. RC2-MR-LC D 6.93 8.15 1F 1F - 2F 2F -
suffer grade 1 damage (1F)
1F) tilt-up walls RC2-MR-MC E 7.15 8.33 1F 1F - 2F 2F -
a few buildings in Focsani would suffer (Precast RC2-HR-LC D 7.46 8.39 1F 1F - 2F 2F -
panels)
grade 2 damage (2F) 2F) RC2-HR-MC E 7.46 8.39 1F 1F - 2F 2F -
“F” = few and “M” = many buildings, as defined by EMS-98
Buildings designed according to
P100-78 code: Pros: satisfactory agreement with
Pros: satisfactory agreement with
no damage would occur actual recorded damage
actual recorded damage
for the considered ground motions Cons: values not sufficiently
Cons: values not sufficiently
differentiated according to structure
differentiated according to structure
type
type

6. PPT available at:
Iolanda-Gabriela CRAIFALEANU, Ioan Sorin BORCIA
DAMAGE INDEX VS. INSTRUMENTAL INTENSITY:
A COMPARISON OF TWO DIFFERENT APPROACHES
IN SEISMIC DAMAGE ASSESSMENT
ANALYSIS OF DAMAGE FOR CHARACTERISTIC BUILDING TYPOLOGIES
DAMAGE INDEX APPROACH Alternative (inverse) approach:
Alternative (inverse) approach:
assessment of the overstrength
assessment of the overstrength
DM = (1/ mon)— ( max+β (EH/(Fyuy)) factors required to limit
factors required to limit
where damage at specified levels
damage at specified levels
Fy = Cy— G = (Cs— ROVS)— G ROVS = Cyy//Cs s
ROVS = C C
Cs = design base shear coefficient Applications:
(code-specified)
ROVS = structural overstrength factor Assessment of the actual
overstrength of structures during
an earthquake, by inputting DM
The assessment of DM for buildings values corresponding to
with known Cs requires also knowing observed damage
the value of ROVS Assessment of the required
As ROVS is difficult to estimate a priori overstrength associated with
alternative approach characteristic damage levels
(insignificant: DM=0.2, repairable
DM=0.4…0.5, collapse DM=1)

7. PPT available at:
Iolanda-Gabriela CRAIFALEANU, Ioan Sorin BORCIA
DAMAGE INDEX VS. INSTRUMENTAL INTENSITY:
A COMPARISON OF TWO DIFFERENT APPROACHES
IN SEISMIC DAMAGE ASSESSMENT
ANALYSIS OF DAMAGE FOR CHARACTERISTIC BUILDING TYPOLOGIES
DAMAGE INDEX APPROACH
Overstrength factors required to limit damage at specified levels
Actual damage in Bucharest on
30.08.1986:
Heavy cracking in partition Bucharest, Focsani,
Structural DM=0.2, mon = 8 DM=0.5, mon = 4
walls for some medium- and system
Typology
ROVS for buildings ROVS for buildings
high-rise reinforced concrete designed according to: designed according to:
frames designed according to P13-63 P13-70 P100-78 P13-63 P13-70 P100-78
R.C. frames RC3.1-MR-LC 3.9 4.4 2.7 4.6
P13-63 and P13-70 with regular RC3.1-MR-MC 1.6 2.7
consistent with the assumed unreinforced
RC3.1-HR-LC
masonry infill 3.3 3.8 1.4 2.4
DM values and with previous walls RC3.1-HR-MC 1.4 1.4
analyses on actual R.C. shear walls RC2-MR-LC 1.7 1.7 1.4 2.1
overstrength RC2-MR-MC 1.1 2.2
Practically no damage was RC2-HR-LC 3.4 2.6 2.3 2.7
RC2-HR-MC 1.4 2.3
recorded in shear wall
Precast R.C. RC2-MR-LC 2.2 1.8 1.8 2.2
structures suggests that they tilt-up walls RC2-MR-MC 1.2 2.6
have met the overstrength (Precast panels)
RC2-HR-LC 2.4 2.0 1.8 2.2
requirements imposed by the RC2-HR-MC 1.4 2.6
earthquake
Similar interpretation for Focsani

8. PPT available at:
Iolanda-Gabriela CRAIFALEANU, Ioan Sorin BORCIA
DAMAGE INDEX VS. INSTRUMENTAL INTENSITY:
A COMPARISON OF TWO DIFFERENT APPROACHES
IN SEISMIC DAMAGE ASSESSMENT
CONCLUSIONS
INSTRUMENTAL INTENSITY APPROACH
Pros: satisfactory agreement with actual recorded damage
Cons: does not allow sufficient differentiation of results
according to
seismic code (level of seismic design forces)
structure type
DAMAGE INDEX APPROACH
Pros: allows assessment of actual/required structural
overstrength, if seismic design level is known, in the alternate
(inverse) approach
Cons: in the direct approach, damage assessment requires
prior evaluation/specification of structural overstrength and of
monotonic ductility
The work reported in the presentation was partly sponsored by the Romanian National Authority for Scientific Research, ANCS