Assessment of the seismic performance and sustainability of the Kath-Kuni building style in the Indian Himalaya

Abstract

Increasing disasters, due to urbanism in combination with the high probability of earthquakes in the Western Indian Himalayas, are impacting the well-being of local communities. The vernacular Kath-Kuni (also called: ‘cator-and-cribbage’ or ‘timber laced masonry’) architecture is a centuries-old building method spread over the Himalayas and the Karakoram mountain range in India, Pakistan and parts of Afghanistan and China. This building typology’s efficacy was proved by its ability to withstand significant seismic events in the region and is, hence, well-known to be an earthquake resistant building style.

To ensure that the valuable building techniques embedded in the traditional Kath-Kuni architecture do not get lost completely, the main question asked in this research is: “Which earthquake resistant features and embedded traditional knowledge of Kath-Kuni walls are essential in generating adequate seismic performance of this vernacular architecture?”

To this end, field research, out-of-plane and in-plane analysis of walls, laboratory testing to characterise the walls ductility, analysis of the building’s box-action and a sustainability study comparing Kath-Kuni with concrete buildings have been carried out.

This led to the conclusion that the horizontal spanning timber beams and the robust connection in the corners are generating box-action by transferring the lateral force from the out-of-plane loaded wall to the in-plane loaded walls. Thus, the seismic capacity of the building is not depending on the rigidity of the floor diaphragms. Secondly, the in-plane loaded walls use a behaviour factor R to take non-linear wall behaviour (ductility) into account. Research to this behaviour factor is and the time period of the building indicates that the behaviour factor and time period obtained from standard formulas are too conservative. Last, the most important earthquake resistant features that contribute to the high ductility of the in-plane loaded walls are the timber connections (kadil dowel connection and maanwi dovetail connection) which are allowing internal rotation in the layer and are acting in parallel and series with one another, the lack of vertical reinforcement which leaves the wall free to deform in vertical direction without damage and the high contribution of friction in between the stone and stone-timber in the wall.

In addition to the seismic resistance of the Kath-Kuni building style, study showed that this architecture scores well on sustainability, in terms of performance, service life and environmental impact. However, high construction costs, due to a scarcity of the main materials, has rendered building of Kath-Kuni houses economically currently unviable.

Therefore, it is recommended to investigate possibilities in modernising and re-interpreting the Kath-Kuni building style using other sustainable and affordable materials, such as bamboo, stabilized earthen blocks or lime concrete. Even though earthquake resistant construction is also feasible using concrete as main material, it is the vernacular architecture and its embedded traditional knowledge that gives character to the Himalayas, which is beneficial for tourism and livelihood. Moreover, the concrete construction is a big contributor to the total global CO2 emissions; hence using local, sustainable and durable materials should be promoted.