This document discusses methods for seismic retrofitting of existing buildings using precast concrete elements. There are three main methods - increasing lateral load capacity through the installation of precast concrete frames, braces, or armature cross walls. Precast concrete frames can be installed as an outer frame or parallel unit frames attached to new or existing foundations. Precast concrete braces are assembled off-site from precast leg and central units connected by pre-stressing cables. Armature cross walls involve replacing timber walls with precast wall panels connected by pins and light grouting.
6. CONSTRUCTION
1. Evaluation of seismic capacity
2. Selecting desired retrofit method
3. Excavation of the ground for extending or
construction of foundation
4. Erection of PCaC columns
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7. 5. Setting of PCaC beams
6. Filling joints
7. Post-tensioning beam - column joints
8. Providing shear transfer
9. Integration of external frame with building
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18. NOTE
• Outer-frame method: 1999 to 2012: 493 projects
• Parallel unit-frame method: 2005 to 2012: 220
projects
• Tohoku earthquake (March 2011) of intensity 9
on moment magnitude scale - 59 buildings
survived
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19. 2.PRECAST CONCRETE BRACE
• 5 unit assemblage
• 4 legs and a central unit
• Pre-stress through external cables
• Brace fits the frame by itself
• Frictional control joints
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27. NOTE
• Proposed by Wani Ahmad & Javed Ahmad
Bhat
• 18kN: 36mm x 36mm: 8-5mmφ: 8.1kg
• Revives traditional construction methodology
• Standardization required
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28. REFERENCE
• Kiyoji Takeda, Kyoya Tanaka, Toshiaki Someya, Asao Sakuda and Yoshiteru Ohno;
“Seismic retrofit of reinforced concrete buildings in Japan using external precast,
pre-stressed concrete frames”; PCI Journal Summer 2013, Volume 58, Pages 41-61.
• Mamoru Oda, Susumu Kono and Fumio Watanabe; “Seismic retrofit of RC buildings
with pre-stressed precast CFT and FRC braces”; The 14th World Conference on
Earthquake Engineering, October 2008, Beijing, China.
• Susumu Kono and Fumio Watanabe; “Retrofitting RC structures with precast pre-
stressed concrete braces”; Proceedings of the 8th U.S. National Conference on
Earthquake Engineering, April 2006, California, USA.
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29. REFERENCE
• Toshimi Kabeyasawa (Editor); “Recent development of seismic retrofit
methods in Japan”; Japan Building Disaster Prevention Association; January
2005.
• Wani Ahmad and Javed Ahmad Bhat; “Pre-tensioned precast elements as a
replacement to wooden bracings in the armature cross-wall system: An
approach to revive forgotten heritage”; IJCIET 2012, Volume 3, Issue 2, Pages
181-187.
• http://en.wikipedia.org/wiki/Seismic_retrofit
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