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Showing 11 results for Truss

Kaveh A., Shahrouzi M.,
Volume 3, Issue 3 (9-2005)
Abstract

Genetic Algorithm is known as a generalized method of stochastic search and has been successfully applied to various types of optimization problems. By GA s it is expected to improve the solution at the expense of additional computational effort. One of the key points which controls the accuracy and convergence rate of such a process is the selected method of coding/decoding of the original problem variables and the discrete feasibility space to be searched by GAS. In this paper, a direct index coding (DIC) is developed and utilized for the discrete sizing optimization of structures. The GA operators are specialized and adopted for this kind of encoded chromosomes and are compared to those of traditional GA S. The well-known lO-bar truss example from literature is treated here as a comparison benchmark, and the outstanding computational efficiency and stability of the proposed method is illustrated. The application of the proposed encoding method is not limited to truss structures and can also be directly applied to frame sizing problems.
M. Rezaiee-Pajand, M. Riyazi-Mazloomi,
Volume 5, Issue 3 (9-2007)
Abstract

In this research a new approach is proposed for elasto-plastic analysis of structures with truss elements. This method covers both perfectly plastic and hardening properties. The Proposed technique uses substituting virtual loads instead of modifying the stiffness matrix. To solve this kind of problems, complementary programming is utilized. Numerical examples demonstrate that elastoplastic analysis by this approach has very good convergence, rapidity, and accuracy.
A. R. Rahai, S. Fallah Nafari,
Volume 11, Issue 4 (12-2013)
Abstract

The seismic behavior of frame bridges is generally evaluated using nonlinear static analysis with different plasticity models hence this paper tends to focus on the effectiveness of the two most common nonlinear modeling approaches comprising of concentrated and distributed plasticity models. A three-span prestressed concrete frame bridge in Tehran, Iran, including a pair of independent parallel bridge structures was selected as the model of the study. The parallel bridges were composed of identical decks with the total length of 215 meters supported on different regular and irregular substructures with non-prismatic piers. To calibrate the analytical modeling, a large-scale experimental and analytical seismic study on a two-span reinforced concrete bridge system carried out at the University of Nevada Reno was used. The comparison of the results shows the accuracy of analytical studies. In addition, close correlation between results obtained from two nonlinear modeling methods depicts that the lumped plasticity approach can be decisively considered as the useful tool for the nonlinear modeling of non-prismatic bridge piers with hollow sections due to its simple modeling assumption and less computational time.
H. Rahami, A. Kaveh, M. Ardalan Asl, S. R. Mirghaderi,
Volume 11, Issue 4 (12-2013)
Abstract

In the process of structural analysis we often come to structures that can be analyzed with simpler methods than the standard approaches. For these structures, known as regular structures, the matrices involved are in canonical forms and their eigen-solution can be performed in a simple manner. However, by adding or removing some elements or nodes, such methods cannot be utilized. Here, an efficient method is developed for the analysis of irregular structures in the form a regular structure with additional or missing nodes or with additional or missing supports. In this method, the saving in computational time is considerable. The power of the method becomes more apparent when the analysis should be repeated very many times as it is the case in optimal design or non-linear analysis.
A. Kaveh, A. Nasrolahi,
Volume 12, Issue 1 (3-2014)
Abstract

In this paper, a new enhanced version of the Particle Swarm Optimization (PSO) is presented. An important modification is made by adding probabilistic functions into PSO, and it is named Probabilistic Particle Swarm Optimization (PPSO). Since the variation of the velocity of particles in PSO constitutes its search engine, it should provide two phases of optimization process which are: exploration and exploitation. However, this aim is unachievable due to the lack of balanced particles’ velocity formula in the PSO. The main feature presented in the study is the introduction of a probabilistic scheme for updating the velocity of each particle. The Probabilistic Particle Swarm Optimization (PPSO) formulation thus developed allows us to find the best sequence of the exploration and exploitation phases entailed by the optimization search process. The validity of the present approach is demonstrated by solving three classical sizing optimization problems of spatial truss structures.
A. Kaveh, M. Maniat,
Volume 12, Issue 2 (6-2014)
Abstract

It is well known that damaged structural members may alter the behaviour of the structures considerably. Careful observation of these changes has often been viewed as a means to identify and assess the location and severity of damages in structures. Among the responses of a structure, natural frequencies and natural modes are both relatively easy to obtain and independent from external excitation, and therefore, can be used as a measure of the structural behaviour before and after an extreme event which might have led to damage in the structure. This paper applies Charged System Search algorithm to the problem of damage detection using vibration data. The objective is to identify the location and extent of multi-damage in a structure. Both natural frequencies and mode shapes are used to form the required objective function. To moderate the effect of noise on measured data, a penalty approach is applied. Varity of numerical examples including beams, frames and trusses are examined. The results show that the present methodology can reliably identify damage scenarios using noisy measurements and incomplete data.
A. Kaveh, M.s. Massoudi ,
Volume 12, Issue 2 (6-2014)
Abstract

Formation of a suitable null basis is the main problem of finite elements analysis via force method. For an optimal analysis, the selected null basis matrices should be sparse and banded corresponding to sparse, banded and well-conditioned flexibility matrices. In this paper, an efficient method is developed for the formation of the null bases of finite element models (FEMs) consisting of tetrahedron elements, corresponding to highly sparse and banded flexibility matrices. This is achieved by associating special graphs with the FEM and selecting appropriate subgraphs and forming the self-equilibrating systems (SESs) on these subgraphs. Two examples are presented to illustrate the simplicity and effectiveness of the presented graph-algebraic method.
E. Wahyuni, Y. Tethool,
Volume 13, Issue 2 (6-2015)
Abstract

The purpose of this study is to determine the effect of vierendeel panel width and vertical truss spacing ratio in an inelastic behavior of the STF system due to earthquake loads. The STF system is applied to a six-storey building that serves as apartments [2]. The STF system is used in the building in the transverse direction (N-S direction), while in the longitudinal direction (W-E direction) the building system uses the special moment resisting frame. The structural behavior was evaluated using nonlinear pushover and time history analyses. The results showed that by increasing the ratio of vierendeel panel width and vertical truss spacing, the ductility of the structure was increased. Based on the performance evaluation, the ratio of the vierendeel panel width and vertical truss spacing on the STF buildings that provided satisfactory performance was more or equal to 1.6. The ultimate drift obtained from non-linear time history analysis was smaller than the pushover analysis. This result showed that the static nonlinear pushover analysis was quite conservative in predicting the behavior of the six-storey building in an inelastic condition.
Guray Arslan, Muzaffer Borekci, Muzaffer Balci, Melih Hacisalihoglu,
Volume 14, Issue 3 (4-2016)
Abstract

The contribution of concrete to inelastic deformation capacity and shear strength of reinforced concrete (RC) columns failing in shear has been investigated extensively by various researchers. Although RC members are designed to have shear strengths much greater than their flexural strengths to ensure flexural failure according to the current codes, shear degradation of RC columns failing in flexure has not been studied widely. The aim of this study is to investigate the shear degradation of RC columns using finite element analyses (FEA). The results of FEA are compared with the results of experimental studies selected from literature, and it is observed that the lateral load-deflection curves of analysed columns are compatible with the experimental results. Twenty-six RC columns were analysed under monotonically increasing loads to determine the concrete contribution to shear strength. The results of analyses indicate that increasing the ratio of shear to flexural strength reduces the concrete contribution to shear strength of the columns.


Jianwei Tu, Guang Que, Bo Tu, Jiayun Xu,
Volume 14, Issue 5 (7-2016)
Abstract

Ship lift is a major navigation structure lifting and lowering ships to shorten the time across the dam. The ship chamber, the key equipment, serves as the carrier for ships. Due to its gigantic body and mass, complicated coupled vibrations occur between the chamber and ship lift structure during seismic process. With the engineering background of the ship lift at the Three Gorges dam, a three-dimensional shell finite element model is established for the ship lift, and then simplified into a three-dimensional truss finite element model through dynamic equivalent principle. And the numerical model of coupled vibration analysis is formed through static condensation, calculating the coupled vibration response between the ship lift structure and the ship chamber. The result shows that no connection and rigid connection between them are both inadvisable. Consequently, three connection devices: spring, viscous liquid damper and magneto-rheological fluid damper are applied to control coupled vibrations during artificial seismic waves. The result shows that the magneto-rheological fluid damper makes better vibration damping effect if suitable semi-active control strategy is applied, in comparison with passive control devices.



Volume 15, Issue 7 (10-2017)
Abstract

This study presents methods for numerical modelling and the static computer analysis of steel decks fixed on scaffoldings. The main problem raised here is the method of creating models of a single deck and determination of the accuracy of every model for various design situations: the analysis of state stress in components of decks, the strength analysis of scaffolding where decks can be loaded by untypical the arrangement of materials and the strength analysis of full scaffoldings. The analysis of a state stress in components of a deck requires a detailed model. The analyses of scaffoldings with load by materials have to be performed with using more simple models of platforms. The static-strength analysis of full scaffoldings with many frame elements can be performed if the simplest models of decks are used. In this paper the sets of truss elements replace the stiffness of scaffolding decks.



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