Incremental Dynamic Analysis
Incremental Dynamic Analysis for Seismic Risk Assessment · Also known as: IDA, Intensity-based analysis, Fragility curve development
Incremental dynamic analysis (IDA) is a method that runs time-history analyses on a structure with a single ground motion record, progressively increasing the intensity until the structure reaches a specified performance level or collapses. Introduced by Vamvatsikos and Cornell in 2002, this approach efficiently generates fragility curves relating earthquake intensity to structural damage and collapse probability.
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When to use it
IDA is essential for performance-based seismic design, seismic risk quantification, and decision-making on retrofits. It is particularly valuable for critical structures (hospitals, emergency facilities, power plants), insurance and financial risk assessment, and research on structural vulnerability. IDA requires significant computational resources but is justified by the wealth of information it provides about structural capacity and risk.
Strengths & limitations
- Directly captures the full range of structural response from elastic to collapse, revealing capacity without approximation
- Efficient generation of fragility curves using a single ground motion scaled to multiple intensities
- Enables identification of failure modes and critical thresholds at different intensity levels
- Provides unbiased estimate of collapse capacity, which is critical for high-consequence structures
- Results can be directly incorporated into probabilistic risk and loss assessment frameworks
- Results are sensitive to the selected ground motion record; high variability across different recordings at the same intensity
- Computational cost is high; hundreds of analyses may be needed to achieve confidence across many ground motions
- Requires expertise in nonlinear modeling, material constitutive laws, and failure criteria to set up correctly
- Identifying the collapse point is ambiguous; stopping criteria (negative stiffness, excessive drift) must be defined a priori
- Fragility curves from single-record IDA may not be representative; multiple records and statistical analysis are necessary
Frequently asked
Why does IDA require multiple ground motion records if I already have one fragility curve?
Ground motions have different frequency content and durations. A single record produces an IDA curve specific to that motion's characteristics. Different records yield different fragility curves. Statistical analysis across 20+ ground motions is necessary to characterize the mean and variability of fragility and support probabilistic decision-making.
What is the difference between intensity measures like Sa(T) and PGA, and which should I use?
Sa(T) (spectral acceleration at the structure's period) is more efficient because it correlates better with structural response, reducing scatter. PGA is often used but is less efficient and may not capture period-dependent hazard. Use the intensity measure that best matches your structure's response characteristics.
How do I determine when to stop the IDA analysis, i.e., when has the structure collapsed?
Common stopping criteria: (1) negative stiffness (slope change in base shear-displacement), (2) inter-story drift exceeding 10% (typical global failure), or (3) computational instability (cannot converge). Define thresholds a priori based on your performance objectives and validate against experimental or forensic data.
Can I use IDA to design for resilience and rapid recovery?
Yes. IDA identifies the intensity at which damage thresholds (repair vs. demolition) are exceeded. By designing so that the structure remains repairable at the design earthquake intensity, you can plan post-earthquake recovery. Compare fragility curves across retrofit scenarios to justify investments.
Sources
- Vamvatsikos, D., & Cornell, C. A. (2002). Incremental dynamic analysis of seismic performance of structures. Earthquake Engineering & Structural Dynamics, 31(3), 491-514. DOI: 10.1002/eqe.141 ↗
- Cornell, C. A., Jalayer, F., Hamburger, R. O., & Foutch, D. A. (2002). Probabilistic basis for 2000 SAC federal emergency management agency steel moment frame guidelines. Journal of Structural Engineering, 128(4), 526-533. DOI: 10.1061/(ASCE)0733-9445(2002)128:4(526) ↗
- Luco, N., & Cornell, C. A. (2007). Structure-specific scalar intensity measures for near-source and broadband ground motions. Journal of Engineering Mechanics, 133(4), 445-456. link ↗
How to cite this page
ScholarGate. (2026, June 3). Incremental Dynamic Analysis for Seismic Risk Assessment. ScholarGate. https://scholargate.app/en/civil-engineering/incremental-dynamic-analysis
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
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