Semi-engineered earthquake-resistant structures: one-storey buildings made with Bhatar construction technique

After the 2005 M7.6 Kashmir earthquake (Pakistan), field observations reported that several buildings manufactured with traditional techniques well resisted to this strong seismic event. Nonetheless, these techniques have never been deeply studied from a structural engineering point of view yet. This thesis reports a full analytical study on the static and seismic behavior of simple one-storey buildings made with a typical construction technique commonly named as “Bhatar” system, used for several centuries and widely diffused in rather remote areas of the Himalayan regions like India, Nepal and Pakistan. The Bhatar system consists of load-bearing walls made of common dry-stacked rubble stone masonry held together by horizontal wooden bands disposed at several levels (spaced at intervals of about 60 cm). It is widely adopted in developing countries due to its advantages from both economical and constructive point of view with respect to the conventional constructions techniques (i.e. brick masonry and concrete structures). In the present work, analytical analyses are conducted with reference to a one-storey building modulus characterized by a 3.6 m x 3.6 m square plan covered by an heavy wooden roof with 20 cm thick earth coverage, in order to investigate its response under both gravity and seismic inertial loadings. In detail, in-plane and out-of-plane response of a single wall under horizontal actions is discussed and particular attention is focused on the connections between the timber elements, which are fundamental for the transmission of the horizontal actions and for preventing overturning and other failure mechanisms. The main aim is twofold: (i) to provide a first insight into the actual seismic response of such construction technique, as a basis for the specific design of ad-hoc laboratory tests on full-scale models, and (ii) to give some rules of thumb for a proper dimensioning and construction of this kind of structures.