Seismic Vulnerability Assessment and Retrofitting Strategies for Traditional Timber-Laced Masonry Buildings in Himalayan Regions

The Himalayan regions of Himachal Pradesh and Uttarakhand fall within Seismic Zones V and VI as per IS 1893 (Part 1): 2023, making them highly susceptible to seismic activity. Despite this, many vernacular buildings have withstood multiple earthquakes over centuries, reflecting inherent structural resilience. A detailed field survey was conducted to evaluate the seismic performance of traditional timber-laced stone masonry buildings, specifically the Kath-Kunni and Thathara typologies. The assessment revealed both resilient features, such as timber lacing and compact massing, and vulnerabilities, including flexible diaphragms, inadequate wall anchorage, and questionable foundation-to-structure connections. Out-of-plane wall failures were frequently observed and are primarily attributed to these combined weaknesses, as also confirmed through review of relevant literature. Based on these observations, relevant strengthening measures have been proposed, drawing from both field documentation and published studies. To support implementation, detailed structural sketches have been developed to illustrate retrofitting solutions compatible with traditional practices. The study contributes toward enhancing the seismic safety of heritage buildings while retaining their cultural authenticity.