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Article
Publication date: 18 April 2017

Maryam Daei and S. Hamid Mirmohammadi

The efficiency of the finite element analysis via force method depends on the overall flexibility matrix of the structure, while this matrix is directly affected from null bases…

81

Abstract

Purpose

The efficiency of the finite element analysis via force method depends on the overall flexibility matrix of the structure, while this matrix is directly affected from null bases vectors. As the null bases for an indeterminate structure are not unique, for an optimal analysis, the selected null bases should be sparse and banded corresponding to sparse, banded and well-conditioned flexibility matrix. This paper aims to present an efficient method for the formation of optimal flexibility matrix of finite element models comprising tetrahedron elements via mathematical optimization technique.

Design/methodology/approach

For this purpose, a linear mixed integer programming model is presented for finding sparse solution of underdetermined linear system, which is correspond to sparse null vector. The charged system search algorithm is improved and used to find the best generator for formation of null bases.

Findings

The efficiency of the present method is illustrated through some examples. The proposed method leads to highly sparse, banded and accurate null basis matrices. It makes an efficient force method feasible for the analysis of finite element model comprising tetrahedron elements.

Originality/value

The force method, in which the member forces are used as unknowns, can be appealing to engineers. The main problem in the application of the force method is the formation of a self-stress matrix corresponding to a sparse flexibility matrix. In this paper, the highly sparse, banded and accurate null basis matrices gains by using mathematical optimization technique.

Details

Engineering Computations, vol. 34 no. 2
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 10 August 2015

Maryam Daei and S. Hamid Mirmohammadi

The interest in the ability to detect damage at the earliest possible stage is pervasive throughout the civil engineering over the last two decades. In general, the experimental…

195

Abstract

Purpose

The interest in the ability to detect damage at the earliest possible stage is pervasive throughout the civil engineering over the last two decades. In general, the experimental techniques for damage detection are expensive and require that the vicinity of the damage is known and readily accessible; therefore several methods intend to detect damage based on numerical model and by means of minimum experimental data about dynamic properties or response of damaged structures. The paper aims to discuss these issues.

Design/methodology/approach

In this paper, the damage detection problem is formulated as an optimization problem such as to obtain the minimum difference between the numerical and experimental variables, and then a modified ant colony optimization (ACO) algorithm is proposed for solving this optimization problem. In the proposed algorithm, the structural damage is detected by using dynamically measured flexibility matrix, since the flexibility matrix of the structure can be estimated from only the first few modes. The continuous version of ACO is employed as a probabilistic technique for solving this computational problem.

Findings

Compared to classical methods, one of the main strengths of this meta-heuristic method is the generally better robustness in achieving global optimum. The efficiency of the proposed algorithm is illustrated by numerical examples. The proposed method enables the deduction of the extent and location of structural damage, while using short computational time and resulting good accuracy.

Originality/value

Finding accurate results by means of minimum experimental data, while using short computational time is the final goal of all researches in the structural damage detection methods. In this paper, it gains by applying flexibility matrix in the definition of objective function, and also via using continuous ant colony algorithm as a powerful meta-heuristic techniques in the constrained nonlinear optimization problem.

Details

Multidiscipline Modeling in Materials and Structures, vol. 11 no. 2
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 9 April 2018

Ali Asghar Pourezzat, Mohammad Hoseini Moghadam, Maryam Sani Ejlal and Ghazaleh Taheriattar

Through an examination of macro-historical studies on the governance of Iran, the purpose of this study is to identify the most significant and important events and trends in the…

376

Abstract

Purpose

Through an examination of macro-historical studies on the governance of Iran, the purpose of this study is to identify the most significant and important events and trends in the rise and fall of Iranian governments and introduce alternative futures in a range of possible, plausible and preferable forms of future governance. To carry out a foresight study of alternative futures of Iranian governance, the authors used futures studies, based on the detection of the most critical driving forces, which are also the most important uncertainties. Futures studies as an interdisciplinary field of study help to identify the events and trends that affect political change and offer scenarios of four alternative futures for the governance of Iran: Smart and Stable Government, Authoritarian Development-oriented Government, Irrational Government and Irrational Breakable Government. The authors believe that Iran’s endeavors to promote democracy, taking the changing international trends into account, make a more trustworthy future for Iran both possible plausible.

Design/methodology/approach

Based on macro-history approach and by using “shared history”, future triangle and then scenario planning, the future of Governance in Iran has been analyzed.

Findings

Whenever the government has distanced itself from the public and has neglected the trend of international change, it has been faced with a period of collapse and annihilation. And whenever these two important factors are understood, the result is a trend of development and growth. Therefore, the most favored image of Iran’s future relies on the maintenance and promotion of public participation and on increasing attention to the sustainable realities of international relations.

Originality/value

The complexities of events and trends affecting the rise and fall of previous governments of Iran make it necessary to use an interdisciplinary approach to understand the events that have emerged or are emerging in its governance. In this study, from futures studies point of view, transformation of governance has been studied.

Details

foresight, vol. 20 no. 2
Type: Research Article
ISSN: 1463-6689

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