• Steel and Composite Structures
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• v.22 no.3
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• pp.521-535
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• 2016

A Harmony Search (HS) and Genetic Algorithms (GA), two powerful metaheuristic search techniques, are used for minimum weight designs of different truss structures by selecting suitable profile sections from a specified list taken from American Institute of Steel Construction (AISC). A computer program is coded in MATLAB interacting with SAP2000-OAPI to obtain solution of design problems. The stress constraints according to AISC-ASD (Allowable Stress Design) and displacement constraints are considered for optimum designs. Three different truss structures such as bridge, dome and tower structures taken from literature are designed and the results are compared with the ones available in literature. The results obtained from the solutions for truss structures show that optimum designs by these techniques are very similar to the literature results and HS method usually provides more economical solutions in multi-element truss problems.

• Structural Engineering and Mechanics
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• v.63 no.5
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• pp.607-615
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• 2017

This study presents optimum design of plane steel bridges considering corrosion effect by using teaching-learning based optimization (TLBO) method. Optimum solutions of three different bridge problems are linearly carried out including and excluding corrosion effect. The member cross sections are selected from a pre-specified list of 128 W profiles taken from American Institute of Steel Construction (AISC). A computer program is coded in MATLAB to carry out optimum design interacting with SAP2000 using OAPI (Open Application Programming Interface). The stress constraints are incorporated as indicated in AISC Allowable Stress Design (ASD) specifications and also displacement constraints are applied in optimum design. The results obtained from analysis show that the corrosion effect on steel profile surfaces causes a crucial increase on the minimum steel weight of bridges. Moreover, the results show that the method proposed is applicable and robust to reach the destination even for complex problems.

• Steel and Composite Structures
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• v.14 no.5
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• pp.431-451
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• 2013

The Big Bang-Big Crunch (BB-BC) optimization algorithm is developed for optimal design of non-linear steel frames with semi-rigid beam-to-column connections. The design algorithm obtains the minimum total cost which comprises total member plus connection costs by selecting suitable sections. Displacement and stress constraints together with the geometry constraints are imposed on the frame in the optimum design procedure. In addition, non-linear analyses considering the P-${\Delta}$ effects of beam-column members are performed during the optimization process. Three design examples with various types of connections are presented and the results show the efficiency of using semi-rigid connection models in comparing to rigid connections. The obtained optimum semi-rigid frames are more economical solutions and lead to more realistic predictions of response and strength of the structure.

• Structural Engineering and Mechanics
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• v.18 no.2
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• pp.137-150
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• 2004

The optimization of active bars' placement and feedback gains of closed loop control system for random intelligent truss structures under non-stationary random excitation is presented. Firstly, the optimal mathematical model with the reliability constraints on the mean square value of structural dynamic displacement and stress response are built based on the maximization of dissipation energy due to control action. In which not only the randomness of the physics parameters of structural materials, geometric dimensions and structural damping are considered simultaneously, but also the applied force are considered as non-stationary random excitation. Then, the numerical characteristics of the stationary random responses of random intelligent structure are developed. Finally, the rationality and validity of the presented model are demonstrated by an engineering example and some useful conclusions are obtained.

• Structural Engineering and Mechanics
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• v.46 no.4
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• pp.571-594
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• 2013

Railway truss bridges are amongst the essential structures in railway transportation. Minimization of the construction and maintenance costs of these trusses can effectively reduce investments in railway industries. In case of railway bridges, due to high ratio of the live load to the dead load, the moving load has considerable influence on the bridge dynamics. In this paper, optimization of the railway truss bridges under moving load is taken into consideration. The appropriate algorithm namely Hyper-sphere algorithm is used for this multifaceted problem. Through optimization the efficiency of the method successfully raised about 5 percent, compared with similar algorithms. The proposed optimization carried out on several typical railway trusses. The influences of buckling, deformation constraints, and the optimum height of each type of truss, assessed using a simple approximation method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.3
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• pp.253-263
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• 2012

With the local Hertz deformation on the contact point, the dynamic contact between a high-speed wheel and an elastic beam having a gap is numerically analyzed by solving the whole equations of motion of the wheel and the beam subjected to the contact condition. For the stability of the time integration the velocity and acceleration constraints as well as the displacement constraint are imposed on the contact point. Especially the acceleration contact condition on the gap is formulated, and it is demonstrated that the contact force variation computed by the velocity contact constraint or by the acceleration contact constraint agrees well with that computed by the displacement contact constraint. The numerical examples show that, when the wheel passes on the gap, the solution is governed by the stiffness of the local Hertzian deformation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.04a
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• pp.103-110
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• 2004

Recently, performance based seismic design (PBSD) methods in numerous forms have been suggested and widely studied as a new concept of seismic design. The PBDSs are far from being practical due to complexity of algorithms resided in the design philosophy In this paper, optimal seismic design method based on displacement coefficient method (DCM) described in FEMA 273 is developed. As an optimizer simple genetic algorithms are used for implementations. In the optimization problem formulated in this paper, strength design criteria, stiffness design criteria, and nonlinear response criteria specified in DCM are included in design constraints. The optimal performance based design(OPBD) method is applied to seismic design of a 9-story two-dimensional steel frame structures.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.269-275
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• 2005

This article describes the development on a new style active hybrid bearing system including both merits of an aerostatic bearing system and a magnetic bearing system. The developed active hybrid bearing system has several advantages: exact rotation, robust controller against the variation of a disturbance, improvement of stiffness and a damper of the system at a high-speed operation, and constraints of the heat generated by a bias current. In order to measure a rotating error due to the change of a cutting force and the variation of a system parameter, a CCS (Cylindrical Capacity displacement Sensor) was used.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.5 s.122
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• pp.427-436
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• 2007

The catenary of a high-speed electrical train is modeled by the finite elements with the upper suspension wire, lower contact wire, and droppers, and the dynamic contact between the catenary and the pantograph is numerically analyzed by solving the whole equations of motion of the pantograph and the catenary system subjected to the contact condition. For the stability of the numerical solution, with the cubic spline interpolation of the catenary displacement, the velocity and acceleration constraints as well as the displacement constraint are imposed on the contact point. Through the various numerical examples, it is shown that the dropper positions as well as the static deflection are crucial to determine the contact and separation of the pantograph of a high-speed train.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.8
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• pp.798-803
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• 2009

This paper proposes a grating scanner which is driven by a stack-type piezoelectric element. The mechanism of the grating scanner is based on flexure hinges. Using some constraints, the compliant mechanism is designed and then verified by Finite Element Analysis. The designed compliant mechanism is manufactured by wire electro-discharge machining, and then integrated with a stack-type piezoelectric element for actuation and a capacitance displacement sensor for measuring ultra-precision displacement. Experiments demonstrates the characteristics and the performances of the grating scanner using the terms of working range, resonance frequency, bandwidth and resolution. The grating scanner is applicable to a Moire interferometry for measuring 3-dimensional microscopic surface.