Numerical Study on Effect of Vertical Shaft Geometry on Seismic Responses of Morning Glory Spillways Case Study: Alborz Dam

Morning Glory Spillways are an important type of flood evacuation systems. According to the specific hydraulic and structural conditions, the evaluation of the seismic behavior of these kinds of spillways could be more precise with considering the interaction of the solid-water-foundation system. In this research, a three dimensional modeling of the morning glory spillway was conducted, considering the reservoir, foundation and overflow tunnel system interactions. The analysis was performed with finite element method using ANSYS.16 software, in order to evaluate the effects of system components interaction on dynamic responses of spillway. ​To determine the effect of shaft geometry on the responses, Tabas earthquake accelerations in three directions applied on seven models with four different values for elevation and four different values of shaft diameter. Also displacements of spillway crest and principal stresses of the node connecting knee into the tunnel were extracted. Frequency Analysis shows that, the increase of the shaft height reduces the system frequencies, but the shaft diameter is not an effective parameter on the frequency of the system. Also the increase of the vertical shaft height, led to the maximum values of the vertical displacement of spillway crest and increase of principal stresses of the knee.