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Haritha Bendapudi  – Dual Degree Civil

Haritha Bendapudi received her MS  Dual Degree in Civil Engineering. Her research work was supervised by Prof. Pradeep Ramancharla. Here’s a summary of Haritha Bendapudi ’s thesis Damage Quantification and Prediction in Concrete Gravity Dams under Earthquake Ground Motions as explained by her: 

About 2% [1] of the dam failures are said to be due to seismic activity. Dams are extremely important lifeline structures and predicting possible damage in the face of an event is essential. Failure of dams due to earthquakes is extensively studied because while the earthquake cannot be terminated, the loss associated with the damage of the dam can be highly mitigated. The loss caused due to earthquake ground motions can be reduced by studying the damage to the dam design under various earthquake loading scenarios and iteratively modifying the design to be resistant to the highest earthquake loading possible in the area of construction. Several concrete gravity dams were severely shaken by earthquakes in the past[2]. Thus the study of response of dams against the seismic ground motions is very necessary. This work addresses the seismic analysis of concrete dams. For this purpose, the Koyna Dam has been chosen. Firstly, the performance of the Koyna dam subjected to the Koyna earthquake is evaluated through 2 numerical models : Linear dynamic analysis and Non-linear dynamic analysis. The results from the linear analysis and the non-linear analysis are compared. Another earthquake of similar intensity of the Koyna earthquake, but different parameters has been applied and the dam performance has been analysed. It has been found that the earthquake with lesser peak ground acceleration (PGA) caused greater damage to the dam as compared to the earthquake ground motion with lesser PGA. The IS Code considers the effects of peak ground acceleration predominantly and the aforementioned result proves that there is a need to study the response of the dam under other ground motions with varying ground motion characteristics of Amplitude, Frequency and Duration. To quantify the damage in Koyna dam, an incremental dynamic analysis has been conducted to study the impact of varying ground motion characteristics on the performance of the dam. Non-linear analysis is performed on the dam cross-section subjected to the ground motions. Engineering Demand Parameters are obtained from the analysis. We aim to understand the damage through 3 damage parameters and classify the damage. The damage parameters are based on the frequently used Engineering Demand Parameters (EDPs). A relation between the damage parameters and damage states is established. Further, the damage is classified using Decision Directed Acyclic Graph Support Vector Machine (DDAGSVM) to study the relation between ground motion parameters (GMPs) and the Damage Parameters for the separate classes. Finally, a shallow Artificial Neural Network is modelled to understand the correlation between GMPs and the Damage Parameters. The high correlation coefficient and low root mean squared error show that the correlation between ground motion data and system response can be predicted very precisely, proving that performance based earthquake design can be extremely efficient and economical. A sensitivity analysis has been carried out to determine the relative importance of the 3 main ground motion parameters. Further, the seismic hazard assessment of the Koyna region using ground seismotonic research by previous researchers has been conducted. The possible threat to the dam and the return periods of the earthquakes have been calibrated. Based on the ground motion data available in the Koyna region, potentially damaging earthquakes, selected based on results obtained from ANN model, have been selected and scaled to the peak ground acceleration found from the seismic hazard assessment. Taking the extent of tensile damage to increase linearly with the increase in PGA for a ground motion (Established by the analysis of Koyna dam under koyna earthquake scaled to 10 PGAs) , the damage possible between 2 scaled PGAs of a ground motion can be linearly interpolated. Based on this the demand of koyna dam in the region has been assessed probabilistically. The range of damage capable on the body of the dam, from minimum to maximum, has been obtained by subjecting the dam to only 4 ground motions (scaled to 3 PGAs) selected based on the ground motion parameter study conducted in this work. A computationally cheaper, incremental dynamic analysis has been proposed.