Earthquake resilience of Pol houses in Ahmedabad
center of gravity is lowered down. The lower portion of the building which has more mass absorbs the energy while the upper lighter portion dissipates the energy. Rigidity approach (resistance by redundancy) - heavy stone and masonry structures come under this approach. There is an increase in structural plan density by availability of shear resistance through wall cross section. Passive approach – the structures are made light with timber and plant-based paper. The construction is such that the structure is made to collapse during an earthquake. It can be rebuilt quickly without causing any casualties.
3.2.2 Background study – The background study mainly focused on the performance of specific structures during earthquakes, examples from the Indian context, reports from the Bhuj earthquake, and understanding of seismic forces. In the Indian context, Randolph Langenbach has extensively researched the seismic-resistant vernacular structures of the Himalayan belt. The studies mention the most destructive earthquake of 2005, in Kashmir valley, in which the traditional structures survived better than the R.C. buildings. The author mentions three typologies which are found in the Himalayan region •
Taq(bhatar) Construction - where horizontal timber members are embedded in the masonry. It does not have vertical reinforcement hence the masonry walls take the load and are in compression. The timber floor penetrating the walls helps the masonry not to spread out.
•
Cator and cribbage – A 1000-year-old technique with intensive timber usage compared to the timber laced masonry structure. It is a robust typology in an earthquake prone region.
•
Dhajji dewari - evolved because of economic and efficient use of materials, as a response to soft soils, complete timber frame integrated with masonry, it is a membrane structure, walls with many smaller panels have performed well during an earthquake, ground floor - taq system, upper floor dhajji dewari system.
Due to their performance in Kashmir earthquake, reconstruction work was executed using the Dhajji Dewari system. A similar case is also found in Portugal, after the Lisbon earthquake of 1755, the Gaiola technology was rediscovered. “Their resilience was proven by their survival, and so they inspired the design and mandatory use of the Gaiola -
technology that
became such a compelling part
of
Lisbon’s subsequent
rebirth.” (Langenbach R. , conservationtech.com, 2001) 29
