Role of timber structural elements in the seismic response of masonry structures in the Himalayan region

Abstract

A large share of the buildings today is still masonry buildings, both reinforced and unreinforced. Post-earthquake reconnaissance studies have shown a remarkable difference between the performance of reinforced and unreinforced masonry buildings. While the unreinforced masonry buildings tend to suffer severe damage, even collapse, resulting in loss of innumerable and invaluable life; reinforced masonry buildings have often been reported to perform remarkably well under seismic events. Sometimes, this performance has exceeded performance of engineered buildings as well.

Himalayas are a highly seismic region in South Asia with multiple major earthquakes recorded across the past two centuries. The remoteness of the region and abundant availability of local materials along with frequent earthquakes has resulted in the development of a seismic culture of earthquake-resistant, timber-reinforced masonry buildings. Though these buildings have shown superior performance under seismic actions, little scientific research has been done to understand and analyse the reason behind this superior performance.

Across the different regions of Himalayas, timber has been used in different structural configurations to increase the seismic resistance of the masonry structures. These traditional building systems remain popular in the Himalayan region for their cheap and easy availability locally. This additional graduation project is a step towards understanding the behaviour of these masonry structures, and the role of timber in preventing catastrophic failure in the former.

In this study, different building typologies in the Himalayas that use timber as a structural element are identified and described. Failure mechanisms of masonry structures are widely studied and a brief overview is presented. In-plane, out-of-plane, combined in-plane and out-of-plane and local failure mechanisms of unreinforced masonry are discussed in detail. Furthermore, a literature review of post-earthquake reconnaissance surveys is conducted to understand different mechanisms through which masonry structures fail.

A review of state-of-the-art on experimental, analytical and numerical studies conducted on resistance of some of the building typologies of Himalayan region (for example, Bhatar, Dhajji Dewari, Ikra, Kath Kuni) is done in this study to understand work done previously. Finally, an analytical analysis is conducted on single room, one-storeyed Bhatar building to investigate the response of an in-plane wall to a lateral load exerted by earthquake excitation.