RETROFITTING OF STRUCTURES − PRINCIPLES AND APPLICATIONS
Amlan K. Sengupta
Department of Civil Engineering
Indian Institute of Technology Madras
Email: amlan@iitm.ac.in
Abstract
Retrofitting reduces the vulnerability of damage of an existing structure during a future earthquake. It
aims to strengthen a structure to satisfy the requirements of the current codes for seismic design. In this
respect, seismic retrofit is beyond conventional repair or even rehabilitation. The principles of seismic
retrofit refer to the goals, objectives and steps. The steps encompass condition assessment of the
structure, evaluation for seismic forces, selection of retrofit strategies and construction. The
applications include different types of buildings, industrial structures, bridges, urban transport
structures, marine structures and earth retaining structures.
The Department of Civil Engineering, Indian Institute of Technology Madras, has developed a
Handbook on seismic retrofit of buildings under the sponsorship of the Central Public Works
Department and under the aegis of Indian Buildings Congress. The book covers the principles,
strategies for retrofit of different types of buildings, geotechnical and foundation aspects, advanced
applications, quality assurance and two case studies.
The handbook is divided in to the following seventeen chapters.
• Making Buildings Safe Against Earthquakes
• Introduction
• Introduction to Seismic Analysis and Design
• Rapid Visual Screening, Data Collection and Preliminary Evaluation
• Condition Assessment of Buildings
• Repair and Retrofit of Non-engineered Buildings
• Retrofit of Masonry Buildings
• Retrofit of Historical and Heritage Structures
• Structural Analysis for Seismic Retrofit
• Retrofit of Reinforced Concrete Buildings
• Retrofit of Steel Buildings
• Mitigation of Geotechnical Seismic Hazards
• Retrofit of Foundations
• Retrofit using Fibre Reinforced Polymer Composites
• Base Isolation and Energy Dissipation
• Quality Assurance and Control
• Retrofit Case Studies
The Handbook has been published by Narosa Publishing House. Orders can be placed at
orders@narosa.com.
The benefits of retrofitting include the reduction in the loss of lives and damage of the essential
facilities, and functional continuity of the life line structures. For an existing structure of good
condition, the cost of retrofitting tends to be smaller than the replacement cost. Thus, the retrofitting of
structures is an essential component of long term disaster mitigation.
Jammu and Kashmir Earthquake Reconstruction Programme
Uri Block, District Baramulla
Najmi Kanji and Tinni Sawhney
Aga Khan Development Network, India, New Delhi
Email: tinni.sawhney@akdn.org
Abstract
The overall objective of the AKDN Jammu and Kashmir Earthquake Reconstruction Programme was to
assist communities in the earthquake affected villages of Uri in District Baramulla. The programme,
implemented in 17 villages (55 hamlets) of the Uri Block and covering 2,458 households, aimed to
rebuild private and public infrastructure, strengthen and enhance existing livelihoods and build
community capacity for disaster preparedness. A related objective was the creation and strengthening of
civil society institutions and community groups to lead the process of reconstruction.
The reconstruction and retrofitting of public and private infrastructure was based upon introducing
seismic resistant building techniques into the area by training local masons through the construction of
demonstration houses, including traditional building practices such as Dhajji Dewari. A total of 97 local
masons were trained (23 worked full time on the AKDN programme) to help communities construct
418 seismic resistant homes. Of these, 160 were for the most vulnerable households, largely comprising
women-headed families with little income, which were identified by the communities themselves.
Support for the reconstruction of public infrastructure included the retrofitting of nine rooms in three
middle schools (Dardkot, Sultan Daki and Basigiran), provision of sanitation facilities for five village
schools, construction of a health centre in Village Gohalta and the reconstruction of the Sultan Daki
Higher Secondary School. The Uri Senior Secondary Girls’ School and adjoining Middle School in the
Uri town were also reconstructed. Retrofitting interventions, led by programme masons and engineers,
have demonstrated a cost effective method to secure buildings partially damaged during the earthquake,
and has generated considerable interest in the area.
The range of livelihood rebuilding and strengthening activities included the repair of 6 irrigation
systems, benefiting 381 farmers; revival of 28 water-run flour mills; piloting systems of rice
intensification; skill building and training to women’s groups; promoting vegetable cultivation in polyhouse; and treatment of stem-borer infestation of infected fruit trees (over 12,000 trees treated). These
experiences have generated a sense of confidence among the community and facilitated traditional
systems of working together. The constitution and intensive training of Community Emergency
Response Teams, School Disaster Response Committees, and the establishment of stock-piles of search
and rescue equipment in each hamlet have contributed to the local knowledge and capacity for disaster
preparedness.
The implementation programme has demonstrated the importance of a multi-sector approach involving
communities at the centre of decision-making.
Building Capacity in Delhi to Seismically Retrofit Existing Lifeline Buildings
J. E. Rodgers1, H. Kumar2, and L. T. Tobin1
GeoHazards International, 200 Town and Country Village, Palo Alto, CA 94301; Tel:
email: rodgers@geohaz.org
2
GeoHazards Society, 71 B floor, Vinobapuri, New Delhi-24 India-110024
email: hari@geohaz.org
1
ABSTRACT
India’s fast-growing capital city of Delhi, home to over 14 million people, faces substantial earthquake
hazards from both distant large-magnitude earthquakes in the Himalayas and smaller local events. The
Delhi metropolitan area contains an amalgam of existing buildings: old and recently constructed,
illegally built and well-designed, humble brick houses and gleaming new high-rises. Many of these
buildings are seismically vulnerable and will threaten the lives of Delhi’s inhabitants if a major
earthquake strikes.
The current earthquake codes of practice are applicable to new buildings and cannot be applied
to these existing buildings that do not have earthquake resistant features. Thus, the existing stock of
important lifeline buildings is vulnerable and need to be retrofitted to raise their level of performance in
earthquakes. This has to be taken up by the administration as a long term mitigation measure. To help
reduce Delhi’s earthquake risk, GeoHazards International (GHI) and Geohazards Society conducted a
project to build the capacity of the Delhi Public Works Department (PWD) to assess and seismically
retrofit vulnerable existing ‘lifeline’ buildings that have important post-earthquake functions.
Many buildings are considered critical or ‘lifeline’ buildings based on their role in a post disaster
scenario as hospitals, command and centres for relief operations, emergencyshelters, etc. In the 2001
Kachchh Earthquake in Gujarat, India, the main health facilities in the district of Kachchh collapsed
leaving thousands of people without access to immediately required medical attention. Improved
seismic performance of these buildings both protects the occupants of these buildings and enables them
to respond more effectively to an earthquake disaster. GHI utilized a practical learning approach in
which a peer review panel from India and the United States mentored Delhi PWD engineers as they
seismically retrofitted government buildings.
Project buildings included the main offices of the Government of the National Capital Territory
of Delhi, the police headquarters, the GTB hospital, the Ludlow Castle school that serves as a relief
distribution center, and the disaster management authority offices. The buildings had a range of
structural systems, configurations, performance goals, and functional requirements. Structural systems
included unreinforced masonry (URM) bearing wall, reinforced concrete frame with URM infill,
reinforced concrete shear wall, and a combination of concrete frame and URM bearing wall. Delhi
PWD engineers learned to apply performance-based earthquake engineering concepts, assess and design
retrofit schemes for existing buildings, address issues of disruption and user requirements, rectify falling
hazards, and apply risk reduction options other than retrofit (such as changing a building’s use or
replacing it with a new earthquake-resistant building). The Delhi earthquake Safety Initiative also had a
separate component for basic disaster awareness and for demonstrating falling hazards mitigation at the
Ludlow Castle School and the Guru Tegh Bahadur Hospital and the Government of Delhi is replicating
these efforts in numerous schools and hospitals in the state. This paper discusses the technical
challenges and lessons learned during this project, and recommends measures to improve future projects
that transfer knowledge to mitigate risks posed by existing buildings.
Concrete Jacketing with Supplemental Damping for Seismic Retrofit of a Non-Ductile Concrete
Building
Sandeep Donald Shah
Taylor Device India Ltd., Gurgaon
Email: donaldshah@yahoo.com
Abstract
It was proposed to seismically upgrade a seven story non-ductile concrete framed building of early
nineties vintage. Analysis results revealed that the structures did not have sufficient structural capacity
to resist even a moderate earthquake. To ensure a higher level of safety, reduce the risk of exorbitant
repair costs and minimize building downtime after an earthquake, it was intended that the seismic
upgrade of the structural system will target the performance standard of ‘immediate occupancy’. A dual
stage approach was used to address this complex retrofit issue. The first part consisted of providing
robust concrete moment frames in each direction using the time tested jacketing methodology. This
ensured adequate strength and stiffness to the structure. The second stage involved adding fluid viscous
dampers. The dampers provided supplementary damping thereby reducing displacements, story drifts
and also the seismic demand on the moment frames. Additional supplementary damping also protected
the building frame against excessive nonlinear deformations. The design scheme used a total of 44
dampers of various force capacities. Analysis results of the retrofitted block showed that the dampers
dissipated significant portion of the seismic energy, reduced displacements and story drifts and limited
the seismic nonlinear demand on the concrete members. This seismic upgrade methodology proved to
be technically sound, easy to execute, less disruptive to the occupants and resulted in significant savings
both in terms of time and cost.