Assessing Seismic Retrofitting Strategies for Historic Building Stock in Kathmandu Valley

Thesis Abstract

Urban centers in Nepal’s Kathmandu Valley house a dense concentration of historic masonry and adobe structures that underpin cultural identity and tourist economy, yet exhibit high vulnerability to seismic events due to brittle materials, irregular geometries, and heritage constraints that limit retrofitting options. This study addresses the critical gap between heritage preservation imperatives and contemporary seismic performance requirements by assessing the effectiveness and feasibility of seismic retrofitting strategies for historic building stock in the Valley. The aim is to identify retrofit approaches that maximize structural resilience while preserving architectural integrity, usability, and heritage value. Specific objectives are (i) to catalog representative typologies of historic buildings in Bhaktapur, Kathmandu, and Patan; (ii) to evaluate performance limits of current retrofitting methods through structural modelling and life-cycle cost assessment; (iii) to compare passive and hybrid retrofit strategies using performance-based criteria; (iv) to develop a decision-support framework for stakeholders that integrates structural safety, heritage conservation, and practical implementation constraints; and (v) to propose policy guidance and a prioritized retrofit roadmap for municipal authorities. The study employs a mixed-methods design anchored in performance-based engineering and heritage conservation theory. The population comprises historic buildings classified as masonry and adobe within the study municipalities. A stratified random sample of 120 buildings across three districts is selected, with 40 buildings in each district, spanning 20 representative typologies. Data collection instruments include a detailed survey checklist capturing material properties, structural configurations, and heritage constraints; non-destructive testing (NDT) data such as rebound hammer tests and ultrasonic pulse velocity on a subset of 60 buildings; 3D laser scanning and photogrammetry to generate geometric models; and stakeholder interviews with 30-40 civil engineers, conservationists, and municipal planners to capture decision-making processes and constraint considerations. Structural analysis will utilize finite element models in ETABS and OpenSees to simulate gravity-only and seismic demand scenarios, calibrated against recorded ground motion and Nepal’s seismic hazard curves. A life-cycle cost analysis framework will be applied to compare retrofit options in terms of initial, maintenance, and social costs, incorporating discount rates and potential disruption costs. Theoretical underpinnings draw on performance-based earthquake engineering (PBEE) and the principles of conservation philosophy (Charter of Kathmandu Valley) to balance risk reduction with heritage values. Data analysis integrates quantitative and qualitative techniques. Regression analysis and ANOVA will identify factors significantly influencing retrofit performance and cost-effectiveness across typologies. Scenario-based PBEE workflows will quantify Expected Loss, Reliability, and Probability of Structural Failure under moderate-to-strong ground motions. For selected case-study buildings, a hybrid retrofit model combining steel reinforced concrete frames, externally bonded fiber-reinforced polymer composites, and traditional seismic detailing will be evaluated for retrofit efficacy and compatibility with historic fabric. Thematic analysis of stakeholder interviews will extract criteria for decision-making, maintenance implications, and regulatory impediments, triangulated with the quantitative findings. The study anticipates finding that careful integration of lightweight steel frames and localized base isolation concepts, complemented by boundary element strengthening for masonry, can significantly improve seismic performance with minimal aesthetic intrusion, while long-term maintenance and monitoring requirements must be factored into life-cycle costs. The expected contribution to knowledge includes (i) a validated, heritage-sensitive retrofit framework for historic buildings in a seismically active valley, (ii) a comparative performance database of retrofit strategies across common Kathmandu typologies, and (iii) a practical decision-support tool linking structural reliability, cultural significance, and cost considerations for policymakers and practitioners. The research will advance understanding of how to harmonize modern seismic resilience with conservation ethics in rapidly urbanizing historic landscapes. The study concludes with actionable recommendations priority retrofit packages for high-risk typologies, guidelines for materials compatibility and rollback options in conservation practice, and policy instruments for funding, regulation, and monitoring that support resilient yet respectful restoration of Kathmandu Valley’s historic built environment.