No abstract

No abstract

Irregular topography induces non-uniform excitation in the supports of large structures such as dams and bridges. The present study employs the 3-dimensional boundary element method to achieve the seismic response of Pacoima Dam's valley and compares the numerical results with the real responses recorded during the 2001 Pacoima earthquake. The horizontal components recorded on the bottom of the valley are used as the input wave for the analysis. The time history of displacements and amplifications of different points are examined. The results revealed that the amplification factor enhanced from bottom to the top of the valley for the most frequencies. The displacement amplification ratio reached approximately 3 along the valley, suggesting the necessity for considering the non-uniform motions effects on huge structures.

One of the important factors in the amplification of seismic waves arriving the ground surface is site effects. Site effects, known as topographic irregularities, lead to seismic wave scattering, and this phenomenon can amplify or reduce the displacement recorded in different parts of a site. Therefore, it is necessary to investigate these effects for an accurate evaluation of the dynamic response of the structures built on these sites. One of the topics that has been given little attention is the interaction effects of topographic irregularities on each other’s dynamic responses. Using the three-dimensional boundary element method (3D-BEM) in the frequency domain, this study investigated the dynamic response of the site with canyons and hills adjacent to each other at different intervals and under SH seismic waves with different angles and dimensionless frequencies and with the hill in different geometries (semi-elliptical, triangular, semi-circular). The obtained results indicated that parts of the canyon that are adjacent to the hill underwent the greatest amplification, especially when the distance between the canyon and the hill is small. It was also found that the incident angle of the waves is one of the important parameters in the obtained displacement pattern on the site. Although the wave hit the canyon-hill site vertically, the results revealed that an asymmetric displacement pattern was experienced on the dynamic response of the site due to the phenomenon of amplification of seismic wave dispersion.

Cavitation is among the most complicated and common damages of spillway structures. This phenomenon is controlled by different parameters including the pressure, flow velocity, spillway surface material, operation time, and air flow content. The cavitation index is calculated along the spillway and compared with its critical value using the measured values of the flow's hydraulic parameters. The high cost of experimental models for determining hydraulic parameters, the time required for developing experimental models, and the ever-increasing capabilities of computational fluid mechanics (CFD) models have led to the use of numerical simulation in the flow analyses. The present study employs ANSYS FLUENT to simulate the flow on the spillway of Aydoghmush Dam (Iran), calculate flow parameters, and determine the cavitation index at the flow rates of 35, 800, 1500, and 1850 m 3 /s. The standard k-ε equations were applied to model the turbulent flow, while the volume of fluid (VOF) method was employed to determine the flow's free surface profile. The results showed acceptable consistency between the FLUENT and physical model results. It was also found that cavitation did not occur at any of the flow rates.