SEISMIC VULNERABILITY ANALYSIS OF EXISTING

BUILDINGS

Methods of vulnerability assessment

• Qualitative descriptors or variables • Physical vulnerability indices• Vulnerability (fragility) curves

Fragility Curve• It is a probabilistic tool used to estimate

the damage likely to occur during a seismic event

• Fragility Curves define the probability that the “ expected global damage of a structure exceeds a given state as a function of a parameter quantifying the severity of the seismic action’

Methods for evaluating Fragility Curves

EXPERT OPINIONProbability function is developed by the opinion of multiple experts and professionals on damage expected from ground motions. ATC-13, 1985 – Report Seismic Safety Commission of the

state of California• MMI – hazard parameter• For 40 different structural types• Opinion of 58 experts

HAZUS – Study- Earthquake loss estimation Methodology- conducted by NIS in 1997 & funded by FEMA• Seismic Intensity parameter- Spectral acceleration

- Spectral displacement

FRAGILITY CURVES USING FIELD DAMAGE DATA METHOD

Shinozuka et al. – F.C. generated for Caltrans expressway bridges in Los Angeles by collection of the damage data after Northridge EQ.• A two-parameter log-normal distribution function was

calibrated for the fragility curves.• PGA - used to represent the intensity of the ground

motion

ANALYTICAL METHODS• In this method damage data is obtained by

numerical analysis

• The structural systems or components are analyzed with different ground motion recorded at different levels of intensity

• Two common procedure for generating the seismic excitations in the fragility studies-

• Time –history analysis• Capacity spectrum method

Selection of computational model of

structure

Selection of earthquake intensity indicator

Selection of model for definition of damage

Selection of representative set of

earthquakes or definition of demand spectrum

Definition of random characterisation of

structural parametersDefinition of damage

states

Nonlinear analysis

Selection of methodology for

nonlinear analysisDefinition of criteria for

identification of damage states

Definition of probabilistic distribution of damage

Vulnerability Curves

Components of the calculation of analytical vulnerability curves ( Dumova- Jovanoska, 2004)

Time-history Analysis

Singhal and Kiremidijan (1997)- generated fragility curves for low, mid and high rise buildings.• Artificial time-histories were simulated by

ARMA (autoregressive moving average) Models

• Spectral acceleration was used for Earthquake hazard parameter

• Park and Ang damage index was used for response parameter

Capacity Spectrum Method (CSM)

• It is a simplified method that estimates the response of a structure from spectrum demand and spectral capacity curves.

Probabilistic Representation of Capacity and Demand Spectra (Mander and Basoz, 1999)

• Hazus earthquake loss estimation methodology (1999) – fragility curve of unreinforced masonry with low-code design level (URM-L) and reinforced concrete moment frames developed by CSM

• Barron and Corvera(2000) - CSM was applied to a four storey structure with shear walls

• Erberik and Elnashai (2004) – Derivation of fragility curves of flat-slab systems

HYBRID METHOD• Combines statistical data(post earthquake data) with

appropriately processed result from non-linear dynamic or static analysis.

• Kappos J. Andrea and Panagopoulos (2009) – derived capacity curves and vulnerability (fragility) curves in terms of PGA and spectral displacement for R/C building types in Greece.

•R/C building model analysed for total 16 accelerograms( half from actual greek records, other half synthetic)•Fragility assssement done using HAZUS ( FEMA-

NIBS 2003)

Hybrid fragility curves (in terms of PGA) for several R/C building classes

Proposed Work

• To qunatify the seismic vulnerability of RC frame buildings by developing analytical fragility curves

• Validate the analytical estimate with experimental data