Majid Pasbani Khiavi
Associate Professor, Faculty of Engineering, University of Mohaghegh Ardabili, Ardabil,

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Journal : Civil Engineering Journal

Parametric Study of the Modal Behavior of Concrete Gravity Dam by Using Finite Element Method Seyed Reza Jafari; Majid Pasbani Khiavi
Civil Engineering Journal Vol 5, No 12 (2019): December
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.28991/cej-2019-03091437

Abstract

Calculating the natural frequency of dams is an essential part of its seismic behavior analysis. Therefore, it is important to calculate the natural frequency. This paper aims simulation and analysis the finite element (FE) model of the Koyna concrete gravity as a case study. For the investigation of the suitable mesh size to achievement the grid independence, the element size considered as a variable parameter and calculated its optimized value by using the Response Surface Optimization (RSO) method. In the independent grid, the Error Contour utilized for controlling mesh quality, which indicates fast variations of the energy in the adjacent elements and can recognize parts of the model that has a high error in calculating responses. The modal response of the dam with a rigid and flexible foundation with and without mass were appraised. The results indicated that modal frequencies in the condition of with and without Pre-stress were different value in all cases. Moreover, the frequency of first four modes by increasing mass and decreasing the stiffness of foundation, frequencies in the case without initial condition (without Pre-stress) has a slightly increased and in the case with initial condition (Pre-stress) had considerable decrease.
Investigation of to the Effect of Bedrock Stiffness on Seismic Behaviour of Roller Compacted Concrete Dam Mohammad Jalali; Majid Pasbani Khiavi; Mortaza Ali Ghorbani
Civil Engineering Journal Vol 3, No 8 (2017): August
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1079.769 KB) | DOI: 10.28991/cej-2017-00000117

Abstract

In this research, the effect of bedrock stiffness on seismic performance of roller compacted concrete (RCC) dam is evaluated using probabilistic analysis. Due to the geometry and behavior of RCC dams, a two-dimensional modeling was selected for system. Ansys software is used for modeling and analysis of dam-reservoir- foundation system. Newmark implicit time integration scheme is developed to solve the time-discretized equations which are an unconditionally stable method. The Watana dam, due to San Fernando earthquake has been selected as a case study. In order to propagate the parametric sensitivity to the seismic performance of the system, Monte Carlo simulation with Latin hypercube sampling (LHS) method is used as a probabilistic method and uncertainty analysis. The sensitivity of responses under seismic loading is reliably examined utilizing different values of ratio of bedrock stiffness to body concrete stiffness as random inputs. Consider to obtained results, it is revealed that the bedrock stiffness how can effect on seismic behavior of concrete gravity dams due to earthquake. Regarding the safety of dams due to compressive stresses, various ways have been assessed to investigate the induced tensile stress in the heel and the results have been investigated. Finally, appropriate range of the ratio of bedrock stiffness to concrete stiffness of dam body is presented to assess the safety design.