ISO/TR 18961:2025

Buildings and civil engineering works — Seismic resilience assessment and strategies — Compilation of relevant information

This document provides an index of typical existing information on the concept, assessment and strategy for seismic resilience of buildings and civil engineering works.

Bâtiments et ouvrages de génie civil — Eevaluation de la résilience sismique et stratégies — Compilation des informations pertinentes

General Information

• Status: Published
• Publication Date: 06-Jan-2025
• ICS: 91.010.01 - Construction industry in general
• ICS: 91.120.25 - Seismic and vibration protection
• Technical Committee: ISO/TC 59 - Buildings and civil engineering works
• Drafting Committee: ISO/TC 59 - Buildings and civil engineering works
• Current Stage: 6060 - International Standard published
• Start Date: 07-Jan-2025
• Completion Date: 07-Jan-2025

Standards Content (Sample)

Technical
Report
ISO/TR 18961
First edition
Buildings and civil engineering
2025-01
works — Seismic resilience
assessment and strategies —
Compilation of relevant information
Bâtiments et ouvrages de génie civil — Eevaluation de la
résilience sismique et stratégies — Compilation des informations
pertinentes
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 1
5 Concept of seismic resilience . 2
6 Assessment . . 2
6.1 General .2
6.2 Determining seismic response .4
6.2.1 Earthquake hazard . .4
6.2.2 Building performance model .5
6.2.3 Building seismic damage state .5
6.3 Assessment using resilience indicators .6
6.3.1 Earthquake-induced casualties .6
6.3.2 Earthquake-induced downtime .7
6.3.3 Earthquake-induced economic losses .7
6.3.4 Seismic resilience level .8
6.4 Seismic resilience-related datasets .8
7 Strategies . 9
7.1 General .9
7.2 Design of built assets .9
7.2.1 Structural design for newly built assets .9
7.2.2 Structural retrofitting for existing built assets.10
7.2.3 Nonstructural design for newly built assets .10
7.2.4 Nonstructural retrofitting for existing built assets .11
7.3 Design for external earthquake-induced hazards .11
Bibliography .12

iii
Foreword
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Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
[1]
With the issue of the "Sendai Framework for Disaster Risk Reduction 2015–2030" , resilience for disaster
risk reduction has become a global consensus. Seismic resilience, as a critical capacity for built assets, needs
to be prioritized. It considers the social, environmental and economic aspects based on conventional seismic
design, ensuring the desired recovery time, tolerable losses and minimal casualties while preventing
collapse.
As a typical example, the conventionally designed building shown in Figure 1 a) underwent severe damage
and lost key functions during an earthquake. By contrast, the building in Figure 1 b), which was designed for
seismic resilience, sustained minimal damage and rapidly regained full postearthquake functionality.
a) Conventionally seismic designed building
b) Seismic-resilient building
Figure 1 — Comparison between buildings designed based on conventional seismic design and
seismic-resilient design concepts
Consequently, seismic resilience has emerged as a critical global concern that necessitates prioritization.
Some countries have standards for assessing and boosting resilience; however, many still overlook its
importance because of inadequate knowledge sharing. ISO documents on the seismic resilience of buildings
and civil engineering works play a critical role in raising awareness worldwide. The development of this
document assists in gathering information on assessment frameworks, metrics and guidelines for improving
seismic resilience.
The collated information includes the following:
— concept of seismic resilience and its development history; recent earthquake disasters have underscored
the need for seismic resilience, as evidenced in a typical case;
— assessment tools for seismic resilience levels; standards, codes and documents were collected from
various entities; these tools assess earthquake-related economic impacts, recovery times and casualties
by providing assessment methods, data, information-acquisition methods and indicators;
— strategies for enhancing seismic resilience; these were collected from investigative documents focusing
on constructing newly built resilient assets and retrofitting existing assets.

v
The compiled information serves as a valuable resource for stakeholders, guiding them in strategizing
to enhance the seismic resilience of built assets, thereby minimizing earthquake-induced damage. This
document can be useful for standard setters, policymakers, users, architects, engineers, and construction
and manufacturing sectors.
vi
Technical Report ISO/TR 18961:2025(en)
Buildings and civil engineering works — Seismic resilience
assessment and strategies — Compilation of relevant
information
1 Scope
This document provides an index of typical existing information on the concept, assessment and strategy for
seismic resilience of buildings and civil engineering works.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Abbreviated terms
ASCE American Society of Civil Engineers
DS damage state
FEMA Federal Emergency Management Agency, an agency of the United States
GIS geographic information system
Ministry of Housing and Urban-Rural Development, a ministry of the People's Republic of
MOHURD
China
National Institute of Standards and Technology of the United States, Grant/Contractor Re-
NIST GCR
ports
NZSEE New Zealand Society for Earthquake Engineering
JSCE Japan Society of Civil Engineers
[17]
PACT Performance Assessment Calculation Tool provided in FEMA P-58
PGA peak ground acceleration
PGV peak ground velocity
SPUR San Francisco Bay Area Planning and Urban Research Association

5 Concept of seismic resilience
Seismic resilience includes the capacity to withstand, adapt to or promptly recover from earthquake
damage to preserve or restore the intended functionality. The concept of seismic resilience is derived from
the broader concept of resilience; and its developmental history is depicted in Figure 2.
[2-15]
Figure 2 — Development of the concept of seismic resilience
[16]
Seismic resilience was exemplified by the 2011 Christchurch earthquake. On February 22, 2011, a strong
earthquake hit Christchurch, New Zealand. Although many built assets in the struck area were constructed
according to traditional seismic design for human safety, many minimally damaged assets were beyond
economic repair and were demolished, resulting in significant economic losses and downtime. By contrast, a
hospital located north of the area and built with a focus on seismic resilience endured the earthquake with
slight damage and swiftly resumed operations.
In drawing lessons from the Christchurch earthquake, the focus is on the following two pivotal elements:
a) evaluating the current seismic resilience of built assets;
b) developing strategies to enhance their seismic resilience.
6 Assessment
6.1 General
Assessment is crucial for seismic resilience because it indicates the mechanical response of built assets
under earthquake action, derives the induced losses and identifies the resilience level of the assets. Seismic
[11,13,17]
resilience assessment involves obtaining the seismic response in step 1 and assessing the resilience
indicators in step 2 (see Figure 3). The datasets provide a foundation for this analysis. Figure 3 illustrates
this method.
Figure 3 — Method for assessing seismic resilience
Methods for assessing seismic resilience are now well-developed globally, with contributions from
[17,18] [11] [19] [13] [20] [21]
organizations, such as FEMA, Arup, ASCE, MOHURD, NZSEE, and JSCE. Some standards
provide comprehensive introductions to seismic resilience assessment methods, whereas others focus on
specific critical aspects of the assessment process. Tables 1 to 3 summarize the main steps outlined in these
standards.
Table 1 — Determining seismic response
[11] [20] [21]
FEMA Hazus ASCE/SEI 41- REDi GB/T 38591- NZSEE JSCE
[17] [18] [19] [13]
P58 5.1 17 2020
Earthquake hazard √ √ √ √ √ √
Building performance
√ √ √ √
model
Building seismic dam-
√ √ √ √
age state
Table 2 — Assessment using resilience indicators
[11] [20] [21]
FEMA Hazus ASCE/SEI 41- REDi GB/T 38591- NZSEE JSCE
[17] [18] [19] [13]
P58 5.1 17 2020
Casualties √ √ √
Downtime √ √ √ √
Economic loss √ √ √ √
Seismic resilience level √ √ √
Table 3 — Seismic resilience-related datasets
[18] [19] [11] [20] [21]
FEMA Hazus 5.1 ASCE/SEI 41-17 REDi GB/T 38591- NZSEE JSCE
[17] [13]
P58 2020
Datasets √ √ √
The following are some detailed examples of the seismic resilience assessment procedure.
EXAMPLE 1 The flowchart of the performance assessment methodology based on FEMA P58 encompasses:
a) establishing the building performance model;
b) specifying earthquake hazards;
c) analyzing building responses;
d) formulating collapse fragility;
[17]
e) evaluating performance .
[11] [17]
EXAMPLE 2 REDi adapted the PACT (FEMA P-58 ) loss assessment method to incorporate practical repair
strategies, delays caused by "impeding factors" and utility disruption times. This update enables forecasting of
the time to reoccupancy, functional recovery or full recovery. Users select the desired recovery state for downtime
analysis through calculations considering the building components impeding the selected recovery state.
[13]
EXAMPLE 3 GB/T 38591-2020 outlines a building assessment procedure that includes:
a) integrating building data;
b) building a structural model;
c) deriving engineering demand parameters from nonlinear time-history analysis;
d) assessing damage states using fragility data;
e) estimating the repair time, repair costs and casualties for a specific earthquake level;
f) assessing the seismic resilience level based on the estimated index.
[18]
EXAMPLE 4 Hazus 5.1 offers a community assessment procedure comprising:
a) selecting the study area;
b) establishing the earthquake hazard scenario;
c) incorporating local soil and geological data;
d) integrating local inventory data;
e) applying Hazus formulae;
f) calculating direct economic loss, casualties and shelter needs;
g) evaluating postearthquake fire impacts;
h) quantifying and characterizing debris.
6.2 Determining seismic response
6.2.1 Earthquake hazard
Earthquake hazards serve as inputs for analyzing seismic responses. These hazards can be characterized by
the response spectrum and ground motion history.
[17]
EXAMPLE 1 FEMA P-58 outlines performance assessment types based on ground motion intensity.
— Intensity-based assessments utilize user-defined acceleration-response spectra, such as code design spectra.
— Scenario-based assessments use spectra from specific earthquake magnitudes and distances calculated using
ground-motion prediction equations (attenuation relationships).
— Time-based assessments rely on seismic hazard curves and the corresponding spectra selected for a particular
annual exceedance probability.

[13]
EXAMPLE 2 GB/T 38591-2020 delineates a method for defining seismic ground motion, ensuring that the
parameters for the time-history analysis of seismic response, including the ground motion amount, duration,
[22]
amplitude and spectrum, align with the Chinese code for the seismic design of buildings (GB50011-2010). The peak
acceleration and velocity of the input earthquake are specified according to relevant regulations.
[18]
EXAMPLE 3 Hazus 5.1 generates ground motion estimates as GIS-based contour maps and stores them in relational
databases, providing location-specific seismic demands. The characterization of the ground motion includes spectral
responses based on the standard spectrum shape, peak ground acceleration (PGA), and peak ground velocity (PGV).
6.2.2 Building performance model
The building performance model, which considers both structural and nonstructural components and
performs nonlinear seismic response time-history analyses, is crucial for capturing the response of
buildings.
[17]
EXAMPLE 1 FEMA P-58 outlines key structural modeling and analysis considerations:
— modelling force–deformation relationships, geometric nonlinearity, gravity loads, damping, diaphragms, soil–
structure interaction, and foundation embedment, and accounting for the nonsimulated deterioration and
failure modes;
— determining the necessary number of analyses;
— assessing the floor velocity, acceleration and effective drift;
— implementing quality assurance measures;
— addressing analysis uncertainties.
[13]
EXAMPLE 2 GB/T 38591-2020 details the modeling and analysis methods:
— using a three-dimensional computational model for seismic response analysis, considering P-Δ effects, large
deformations and the impact of stairs on the dynamic response;
— ensuring that the representative value of the gravity load in the elastic–plastic analysis complies with the Chinese
code for the seismic design of buildings and the load code for building structures;
— the mechanical model for the applicable building types must satisfy the corresponding requirements and select
reasonable material constitutive relationships and damping ratios.
6.2.3 Building seismic damage state
Damage states can be delineated using fragility curves or discrete-state descriptions, with the former
offering a quantitative assessment and the latter being perceptual. Assessing the damage state of a building
involves evaluating both the structural and nonstructural components against a fragility database and
engineering criteria. Component fragility data are characterized by a probability distribution that aligns
with engineering demands. This approach covers both component- and building-level damage states, with
the latter derived from the aggregate of individual component states.
See EXAMPLEs 1 to 3 for component-level damage states and EXAMPLEs 4 and 5 for building-level damage states.
[17]
EXAMPLE 1 FEMA P-58 characterizes component damage with uncertainty. The fragility functions that follow
lognormal distributions depict the probability of damage at specific demand levels. Figure 4 illustrates the need for
distinct fragility functions for each sequential and mutually exclusive or simultaneous damage state.

NOTE DS represents the damage states, with DS1–DS4 indicating increasing severity from slight to severe
damage. The term, probability (DS state. The interstory drift ratio, expressed in radians, indicates the deformation of a component. The fragility
curves depict the probability of each damage state occurring at specific interstory drift ratios.
Figure 4 — Example family of fragility curves
[13]
EXAMPLE 2 GB/T 38591-2020 determines the likelihood of various component damage states by integrating the
engineering demand parameters with the component fragility data.
[18]
EXAMPLE 3 Hazus 5.1 defines structural and nonstructural damage states using discrete state descriptions, in
terms of one of five ranges of damage or “damage states”: “none,” “slight,” “moderate,” “extensive” and “complete”.
[13]
EXAMPLE 4 GB/T 38591-2020 determines the damage states of structural and nonstructural components based
on the member vulnerability database and engineering demand parameters. The fragility data of the components are
represented using a probability distribution that varies with the engineering demand parameters.
[23]
EXAMPLE 5 SPUR defines the damage state using discrete state descriptions, as listed in Table 4.
[23]
Table 4 — Damage state defined in SPUR
Category Buildings
A Safe and operational
B Safe and usable during repair
C Safe and usable after repair
D Safe but not repairable
E Unsa
...