Site Specific Seismic Study For Response Evaluation Of Concrete Gravity Dam: A Case Study Of Buddhigandaki Hydroelectric Project

Abstract

Nepal plans to build a series of large hydropower projects to meet its growing electricity demand. One of the major challenge in hydroelectricity development that needs to be tackled is the threat to the project structure component posed by the possible earthquake hazard. Dam is one of the key components of any Hydropower project (HPP) and failure in this structure has major impact in the energy production of the country. This thesis study focuses on the characterization of ground motion to develop a site specific response spectrum and evaluate the seismic response of the dam for Buddhi Gandaki Hydroelectric Project (BGHEP), located at Gorkha district. Probabilistic Seismic Hazard Analysis (PSHA) was carried out to establish the seismic hazard curve for the dam site. The Peak Ground Acceleration (PGA) for DBE, OBE and MDE with return period of 475 years,145 years and 1000 years was found to be 0.48g 0.28g and 0.68g respectively. Site specific response spectra was developed from two method for OBE and MDE ground motions. Different load scenarios acting on the dam were assessed, and the formation of hydrodynamic additional water mass during seismic excitation is taken into account. In ANSYS 2020 R2, a 3D-solid element model was created, and a linear dynamic study of the modelled dam was carried out. The modal analysis of dam suggested that rigid response and the missing mass effect should be included in the examination of the response spectrum. The response of the dam was evaluated in terms of the tensile stress generated in the dam. Under the strength and serviceability design circumstances, it was discovered that the highest tensile stress developed in the dam was within the allowed tensile strength limit.