MULTISTOREY REINFORCED CONCRETE BUILDINGS DESIGN
A large number of reinforced concrete multistoreyed frame buildings were heavily damaged and many of them collapsed completely in Bhuj earthquake of 2001 in the towns of Kachchh District (viz., Bhuj, Bhachao, Anjar, Gandhidham and Rapar) and other district towns including Surat and Ahmedabad. In Ahmedabad alone situated at more than 250 kilometers away from the Epicentre of the earthquake, 69 buildings collapsed killing about 700 persons. Earlier, in the earthquake at Kobe (Japan 1995) large number of multistoreyed RC frame buildings of pre 1981 code based design were severely damaged due to various deficiencies. Such behaviour is normally unexpected of RC frame buildings in MSK Intensity VIII and VII areas as happened in Kachchh earthquake of January 26, 2001. The aim of this paper is to bring out the main contributing factors which lead to poor performance during the earthquake and to make recommendations which should be taken into account in designing the multistoreyed reinforced concrete buildings so as to achieve their adequate safe behaviour under future earthquakes. The Indian Standard Code IS:1893 was suitably updated in 2002 so as to address the various design issues brought out in the earthquake behaviour of the RC Buildings. The paper highlights the main provisions of this code.
Causes of the Collapse of RC Frame Buildings and Recommendations
Ignorance of the Architects and Structural Engineers about the Contents of the relevant
earthquake resistant Building Codes :
The following BIS Standards will be mainly required for the design of RCC Buildings. Architect’s and Structural engineer’s design office should have the current copies of these standards available in their offices and all their staff should fully familiarize with the contents of these codes:-
1. IS: 456 -2000 “Code of Practice for Plain and Reinforced Concrete”
2. IS: 875 Part 1 “Unit weights of materials”.
3. IS: 875-1987Design loads ( other than earthquake ) for buildings and structures, Part2
4. IS: 875-1987Design loads ( other than earthquake ) for buildings and structures ,Part 3 Wind
5. IS: 1904-1987 “Code of Practice for Structural Safety of Buildings: Foundation”
6. IS: 1498-1970 Classification and identification of soils for general engineering purposes
7. IS: 2131-1981 Method of Standard Penetration Test for soils (First Revision)
8. IS: 1905-1987, Code of Practice for Structural Safety of Buildings: Masonry
9. IS:1893(Part-I)-2002 "Criteria for Earthquake Resistant Design of Structures (Fifth
10. IS:13920-1993, "Ductile Detailing of Reinforced Concrete Structures subjected to Seismic
Forces – Code of Practice"
11. IS: 4326-1993, "Earthquake Resistant Design and Construction of Buildings – Code of
Practice (Second Revision)"
12. IS-NBC-2005: National Building Code of India.