Construction technology of multi-tiered temples and their rehabilitation after 2015 April Earthquake in Bhaktapur

Kathmandu Valley comprises numerous tiered temples ranging from single to multi-tiered. A 7.6 magnitude earthquake struck Nepal on 25th April 2015, with the epicenter in the Gorkha district at 80 km northwest of Kathmandu and south of the China border. The 2015 Gorkha earthquake and the following aftershocks caused damages to many temples; the damages ranging from minor to few fully collapsed state. This paper focuses on Nepal's tallest temple the Nyatapola, square-shaped in the plan, and the Bhairavnath temple, rectangular-shape in the plan-representing the tiered temples with more than three tiers of the Kathmandu Valley. The paper investigates the employed indigenous construction technology, the condition/ level of damage suffered by case studies during the 2015 earthquake; presents the ongoing rehabilitation/strengthening works introduced following the recommendations of structural, architectural, and conservation experts. The main objectives are to explore indigenous construction technology, evaluate damage scenarios in case studies, and plan rehabilitation approaches aftermath 2015 earthquake. Methodology in the research includes the literature reviews on the construction technology of multi-tiered temples, case studies on presentative cases and the rehabilitation process adopted, key findings for damages, conclude, and provide recommendations. The rehabilitation process consisted of workshops and meetings with related authorities and the formation of a technical committee as per the recommendations of the experts. The team prepares a condition assessment report based upon visual inspections, documentations through on-site measurements, photographs, records of changes, and alterations. Based on condition assessment, the reasons for the damages are analyzed and appropriate rehabilitation/strengthening methods are recommended. The key findings consist of common construction technology of locally available materials like timber, mud, bricks, and stone with reducing wall thickness, and roof towards the top. The geometrical configuration, the inconsistent relative motion of the wall and roof during the earthquake; insufficient joint keys, and lack of regular monitoring maintenance are responsible for the level of damages in the temples.