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Modal analysis of concrete arch dam–reservoir–foundation rock systems is a challenging task. The complexities arise mainly due to computing mode shapes encountered when solving an eigenvalue problem with asymmetric generalized mass and stiffness matrices. Moreover, the problem becomes complicated when wave propagation is occurring due to the inclusion of water compressibility and foundation rock mass. In the present study, a computational tool is especially developed for this purpose. The theoretical background is explained initially. Subsequently, dynamic analysis of the Morrow Point arch dam–reservoir–foundation rock system is carried out with different values of reservoir bottom absorption coefficient. In addition, some of the modal characteristics of such systems, including resonant frequencies and natural periods, are discussed. The main objective is to perform these analyses by modal analysis. However, the direct method of analysis is also carried out in each case as a basis for comparison from the perspectives of accuracy and efficiency. [ABSTRACT FROM AUTHOR]

Purpose: The response of an idealized triangular concrete gravity dam is studied due to horizontal and vertical ground motions for both fully reflective and absorptive reservoir bottom conditions. For each combination, in this paper different orders of Givoli-Neta (G-N) high-order truncation condition are aimed to be evaluated from accuracy point of view by comparing the results against corresponding exact solutions which relies on utilizing a two-dimensional fluid hyper-element. Design/methodology/approach: In present study, the dynamic analysis of concrete gravity dam-reservoir systems is formulated by Finite Element (FE)-(FE-TE) approach. In this technique, dam and reservoir are discretized by plane solid and fluid finite elements. Moreover, the G-N high-order condition imposed at the reservoir truncation boundary. This task is formulated by employing a truncation element at that boundary. It is emphasized that reservoir far-field is excluded from the discretized model. Findings: It was observed that trend in gaining accuracy with increase in the order of G-N condition were basically the same for both horizontal and vertical ground motions under full reflective reservoir bottom condition. Moreover, convergence rate increases for absorptive reservoir bottom condition cases in comparison with fully reflective cases. It is also noticed that in certain cases, the responses are hardly distinguishable from corresponding exact responses. This reveals that proposed FE-(FE-TE) analysis technique based on G-N condition is quite successful, and one may fully rely on that for accurate and efficient analysis of concrete gravity dam-reservoir systems. Originality/value: Dynamic analysis of concrete gravity dam-reservoir systems are formulated by a new method. The salient aspect of the technique is that it utilizes G-N high-order condition at the truncation boundary. This is achieved by developing a special truncation element which its generalized matrices are derived for Finite Element Method (FEM) programmers. The method is discussed for all types of excitation and reservoir bottom conditions. It must be emphasized that although time harmonic analysis is considered in the present study, the main part of formulation is explained in the context of time domain. Therefore, the approach can easily be extended for transient type of analysis. [ABSTRACT FROM AUTHOR]

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The introduction of computer numerical control-based manufacturing systems has highlighted the need to develop new models for determining optimal equipment replacement schedules and levels of investment. A multi-period replacement model based on a mixed integer nonlinear programming formulation has been developed. However, validation of the new model has been inconclusive because several other factors such as system setups and lot sizes need to be considered.

In seismic analysis of concrete gravity dam and reservoir systems using finite-element models, finding an appropriate and simple reservoir upstream truncation condition has been a challenging issue for researchers. The Sommerfeld condition is the classical approach most engineers use for this purpose and it is widely available in commercial finite-element software. In 2012, Wavenumber method was proposed as an alternative approach. The main goal of the present study is to modify this approach so it can handle vertical as well as horizontal ground motions. Moreover, the aim of the study is to evaluate the performance of the approach more thoroughly in comparison to the Sommerfeld truncation boundary, especially for vertical ground motions. With this aim, Pine Flat dam in the USA is used as a typical example. Several models are considered with different values of normalised reservoir length. The dynamic loading considered is the local Taft earthquake record of 1952. Furthermore, two types of reservoir base condition – full reflective and absorptive – are adopted. Overall, this allowed for a thorough examination and evaluation of the effectiveness of the wavenumber-TD approach for seismic analysis of concrete gravity dams. [ABSTRACT FROM AUTHOR]

An efficient, practical approach to the copper-catalyzed synthesis of 2,3-disubstituted quinazolin-4(3H)-one derivatives is described. The preparation involves treatment of benzyl amines with benzyl anthranilamides in the presence of Cu(OAc)2 and tetra-n-butylammonium bromide (TBAB). [ABSTRACT FROM AUTHOR]

SUMMARY There are several alternatives to evaluate seismic damage-cracking behavior of concrete arch dams, among which damage theory is the most popular. A more recent option introduced for this purpose is plastic-damage (PD) approach. In this study, a special finite element program coded in 3-D space is developed on the basis of a well-established PD model successfully applied to gravity dams in 2-D plane stress state. The model originally proposed by Lee and Fenves in 1998 relies on isotropic damaged elasticity in combination with isotropic tensile and compressive plasticity to capture inelastic behaviors of concrete in cyclic or dynamic loadings. The present implementation is based on the rate-dependent version of the model, including large crack opening/closing possibilities. Moreover, with utilizing the Hilber-Hughes-Taylor time integration scheme, an incremental-iterative solution strategy is detailed for the coupled dam-reservoir equations while the damage-dependent damping stress is included. The program is initially validated, and then, it is employed for the main analyses of the Koyna gravity dam in a 3-D modeling as well as a typical concrete arch dam. The former is a major verification for the further examination on the arch dam. The application of the PD model to an arch dam is more challenging because the governing stress condition is multiaxial, causing shear damage to become more important than uniaxial states dominated in gravity dams. In fact, the softening and strength loss in compression for the damaged regions under multiaxial cyclic loadings affect its seismic safety. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The response of a concrete arch dam is very much affected by the mechanisms of foundation rock behaviour. This type of dam is highly sensitive to displacements of its foundation owing to the low stiffness of the dam compared to the displacements of its foundation and abutments. Seepage is a load type which is distributed widely within foundation rock. Therefore, it could have important effects on displacements and stresses in the dam. In this paper, the Karun III double-curvature, 205 m high arch dam is selected as a case study. Effective stress analyses are carried out for the dam. The analysis results are compared with values recorded by instruments. Furthermore, the effects of some basic input parameters on the response of the dam are investigated. Subsequently, basic parameters are calibrated based on the initial investigation results, and the effective stress analysis is carried out for the Karun III dam by employing the modified parameters.fference in strain rate between the different tests. The deduced from the miniature vane was between 1·19 and 1·40 times that mobilised in quick-undrained TC of 38 mm diameter specimens under of 100 kPa. New methods of analysis are presented to estimate the strength contribution of the gel-like pore fluid to the mobilised , and also to determine more accurately the water content corresponding to the fall-cone liquid limit condition. The response of a concrete arch dam is very much affected by the mechanisms of foundation rock behaviour. This type of dam is highly sensitive to displacements of its foundation owing to the low stiffness of the dam compared to the displacements of its foundation and abutments. Seepage is a load type which is distributed widely within foundation rock. Therefore, it could have important effects on displacements and stresses in the dam. In this paper, the Karun III double-curvature, 205 m high arch dam is selected as a case study. Effective stress analyses are carried out for the dam. The analysis results are compared with values recorded by instruments. Furthermore, the effects of some basic input parameters on the response of the dam are investigated. Subsequently, basic parameters are calibrated based on the initial investigation results, and the effective stress analysis is carried out for the Karun III dam by employing the modified parameters. [ABSTRACT FROM AUTHOR]

SUMMARY Formulation and algorithmic treatment of a rate-dependent plastic-damage model modified to capture large tensile cracking in cyclic-loaded concrete structures are presented in detail for a three-dimensional implementation. The plastic-damage model proposed by Lee and Fenves in 1998 was founded based on isotropic damaged elasticity in combination with isotropic multi-hardening plasticity to simulate cracking and crushing of concrete under cyclic or dynamic loadings. In order that the model can capture large crack opening displacements, which are inevitable in plain concrete structures, the excessive increase in plastic strain causing unrealistic results in cyclic behaviors is prevented when the tensile plastic-damage variable controlling the evolution of tensile damage is larger than a critical value. In such a condition, the crack opening/closing mechanism becomes similar to discrete cracking. The consistent tangent operator required to accelerate convergence rate is also formulated for the large cracking state including viscoplasticity. The validation and performance of the modified algorithm implemented in a special finite element program is exemplified through several single-element tests as well as three structural applications. The last example examines the model in the seismic fracture analysis of Koyna dam as a benchmark problem and the resulting crack profile is compared with the available experiment. The numerical experimentations well demonstrate that the developed model whose modification is necessary to properly simulate the cyclic behavior of plain concrete subjected to large tensile strains is robust and reasonably accurate. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Dynamic analysis of concrete gravity dam-reservoir systems is an important topic in the study of fluid-structure interaction problems. It is well-known that the rigorous approach for solving this problem relies heavily on employing a two-dimensional semi-infinite fluid element. The hyper-element is formulated in frequency domain and its application in this field has led to many especial purpose programs which were demanding from programming point of view. In this study, a technique is proposed for dynamic analysis of dam-reservoir systems in the context of pure finite element programming which is referred to as the wavenumber approach. In this technique, the wavenumber condition is imposed on the truncation boundary or the upstream face of the near-field water domain. The method is initially described. Subsequently, the response of an idealized triangular dam-reservoir system is obtained by this approach, and the results are compared against the exact response. Based on this investigation, it is concluded that this approach can be envisaged as a great substitute for the rigorous type of analysis. [ABSTRACT FROM AUTHOR]

The accurate dynamic analysis of concrete gravity dams relies heavily on employing a two-dimensional semi-infinite fluid element. The usual method for calculating the impedance matrix of this fluid hyper-element is dependent on the solution of a complex eigen-value problem for each frequency. In the present study, a modified efficient procedure is proposed which simplifies this procedure significantly, and results in great computational time saving. Moreover, the accuracy of this technique is examined thoroughly and it is concluded that modified efficient procedure is extremely accurate under all practical conditions. It is also shown that the original efficient method proposed in a previous study can be considered as a special case of the present more general procedure. [ABSTRACT FROM AUTHOR]

The accurate dynamic analysis of structures is usually performed by a fine finite element discretization with very large number of degrees of freedom. Apart from modal analysis, one can reduce the number of final equations by assuming the deformed shape of the structure as a linear combination of independent Ritz vectors. The efficiency of this method relies heavily on the vectors selected. In this paper, a new set of Ritz vectors is proposed. It is primarily proved that these vectors are linearly independent. Subsequently, various two and three-dimensional examples are analyzed based on the proposed method. In each case, the results are compared with the ones obtained based on usual Ritz and modal analysis methods. It is finally concluded that the proposed method is very effective and efficient method for dynamic analysis of structures in frequency domain. [ABSTRACT FROM AUTHOR]

A new effective procedure is proposed for evaluating the earthquake response of concrete arch dams including dam-reservoir-foundation interaction effects. The method is developed by integration of the most recent techniques designed to save computational time in different parts of the dynamic analysis of the complete dam-reservoir-foundation system. These are employment of the modified-efficient fluid hyper-element for modeling of the far-field of the reservoir, efficient evaluation of coupled mode-shapes of the system, and other alternatives for the main core of the procedure. Also, Morrow Point dam is analyzed and execution time saving in different parts of this analysis are provided and discussed. [ABSTRACT FROM AUTHOR]