• Steel and Composite Structures
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• v.7 no.6
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• pp.421-440
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• 2007

An optimal design method in cooperated with nonlinear inelastic analysis is presented. The proposed nonlinear inelastic method overcomes the difficulties due to incompatibility between the elastic global analysis and the limit state member design in the conventional LRFD method. The genetic algorithm used is a procedure based on Darwinian notions of survival of the fittest, where selection, crossover, and mutation operators are used to look for high performance ones among sections in the database. They are satisfied with the constraint functions and give the lightest weight to the structure. The objective function taken is the total weight of the steel structure and the constraint functions are load-carrying capacity, serviceability, and ductility requirement. Case studies of a planar portal frame, a space two-story frame, and a three-dimensional steel arch bridge are presented.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.473-476
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• 2011

본 논문에서는 열차와 교량의 상호작용과 주행속도에 의해 결정되어지는 진동지속시간과 차체연직가속도 증폭효과를 고려하여 철도교량의 진동사용성 허용처짐을 제시하고자 하였다. 열차가 교량을 통과할 때의 처짐 형상을 사인파로 가정하고 열차와 교량의 상호작용을 진동전달함수로 표현하여 철도교량의 진동 사용성 허용처짐을 유도하였다. 그리고 진동지속시간을 고려하기 위해 연직가속도 허용기준으로서 진동지속시간을 고려한 교량구조물의 진동사용성기준을 사용하였다. 매개변수연구를 통하여 열차 주행속도의 증가에 비례하여 차체연직가속도는 증가하지만 교량최대변위의 변화는 미미함이 확인됨으로 인하여 차체연직가속도 증가와 동반하여 연직가속도 허용기준역시 증가하는 것을 보정할 필요가 있을 것으로 판단하였다. 따라서 전개된 철도교량의 진동사용성 허용처짐식에 매개변수연구를 통하여 가정한 가속도 증폭계수를 적용하여 열차의 증속에 의한 가속도증폭효과를 고려하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.207-214
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• 2001

In Korea, the multi-dwelling residential buildings are most popular housing system that is reinforced concrete shear wall system. However, the serviceability and safety of the system have been decreased because of the errors in design or construction and inadequate maintenance. In addition the safety of the system cannot be evaluated reasonably because the system is analyzed by the deterministic approach. Therefore, this study is aimed to analyze reinforced concrete shear walls by the reliability approach considering uncertainty based on the probability theory. In this study, a reliability analysis program using MATLAB is developed by combining AFOSM and Sampling Method for the reinforced concrete shear walls within feasible design area. The reasonable reliability index β of ultimate limit states for RC shear walls are calculated automatically using this developed program with the measured data those have means and standard deviations in the field. The ultimate states are compression failure, tension failure, governing compression, and governing bending of the reinforced concrete shear walls respectively. To estimate the safety of the system using developed program can be used to predict residual life-time of the system.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.04a
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• pp.126-130
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• 1992

Recently, fatigue problem become a critical issue in the design of prestressed concrete bridges due to the increase of traffic volumes and use of high-strength materials. Most existing studies are mainly concerned with the fatigue behavior of component materials only such as concrete, reinforcing bars, and prestressing steels and few studies exist that deals with the fatigue behavior of bridge members. An improved analytic formulation for both uncracked and cracked prestressed concrete composite section with cyclic creep effect is developed to take into account the change of neutral axis with crack propagation. The procedure also enables to investigate serviceability limit states, deflection and crack width. The present study allows more realistic analysis and design of prestressed concrete composite girder bridges under fatigue loadings.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.145-152
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• 2003

An optimal design method in cooperated with nonlinear inelastic analysis method is presented. The proposed nonlinear inelastic method overcomes the difficulties due to incompatibility between the elastic global analysis and the limit state member design in the conventional LRFD method. The genetic algorithm uses a procedure based on Darwinian notions of survival of the fittest, where selection, crossover, and mutation operators are used among sections in the database to look for high performance ones. They satisfy the constraint functions and give the lightest weight to the structure. The objective function is set to the total weight of the steel structure and the constraint functions are load-carrying capacities, serviceability, and ductility requirement. Case studies of a three-dimensional frame and a three-dimensional steel arch bridge are presented.

• Steel and Composite Structures
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• v.1 no.2
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• pp.159-170
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• 2001

The Millennium Tower is situated to the north of the center of Vienna. With a height of 202 m it is the highest building in Austria. Realization was improved by new methods. The tower is a typical example of mixed building technology, combining composite frames with a concrete core. Special attention has been paid to the moment connections between the slim floors and the column tubes resulting in a drastically reduced construction time and thin slabs. The semi-continuity has been considered in the design at ultimate and serviceability limit states.

• Steel and Composite Structures
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• v.6 no.5
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• pp.435-457
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• 2006

The paper presents the cost optimization of composite floor trusses composed from a reinforced concrete slab of constant depth and steel trusses consisting of hot rolled channel sections. The optimization was performed by the nonlinear programming approach, NLP. Accordingly, a NLP optimization model for composite floor trusses was developed. An accurate objective function of the manufacturing material, power and labour costs was proposed to be defined for the optimization. Alongside the costs, the objective function also considers the fabrication times, and the electrical power and material consumption. Composite trusses were optimized according to Eurocode 4 for the conditions of both the ultimate and the serviceability limit states. A numerical example of the optimization of the composite truss system presented at the end of the paper demonstrates the applicability of the proposed approach.

• Structural Engineering and Mechanics
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• v.55 no.4
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• pp.801-813
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• 2015

Flexural stiffness of bridge spans has become even more important parameter since Eurocode 1 introduced for railway bridges the serviceability limit state of resonance. For simply supported bridge spans it relies, in general, on accurate assessment of span moment of inertia that governs span flexural stiffness. The paper presents three methods of estimation of the equivalent moment of inertia for such spans: experimental, analytical and numerical. Test loading of the twin truss bridge spans and test results are presented. Recorded displacements and the method of least squares are used to find an "experimental" moment of inertia. Then it is computed according to the analytical method that accounts for joint action of truss girders and composite deck as well as limited span shear stiffness provided by diagonal bracing. Finally a 3D model of finite element method is created to assess the moment of inertia. Discussion of results is given. The comparative analysis proves efficiency of the analytical method.

• Computers and Concrete
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• v.11 no.3
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• pp.253-270
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• 2013

The aim of the present paper is to show the application of optimization strategies for the cost of beams in reinforced concrete buildings and to propose pre-sizing parameters. In order for these goals to be met, an optimization software program was developed. The program combines the analysis of structures by the grid model, reinforced concrete sizing, and the simulated annealing optimization heuristic. Sizing is compliant with the NBR 6118 (2007) Brazilian standard, according to which flexural, shearing, torsion, and web reinforcements and serviceability limit states (deflection and crack width limitation) are checked. Besides the dimensions of the situations mentioned above, the influence the cost of each material (steel, concrete and formwork) has on the overall cost of structures was also determined.

• Steel and Composite Structures
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• v.17 no.5
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• pp.705-719
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• 2014

Composite steel-concrete box girders are frequently used in bridge construction for their economic and structural advantages. An integrated metaheuristic based optimization procedure is proposed for discrete size optimization of straight multi-span steel box girders with the objective of minimizing the self-weight of girder. The metaheuristic algorithm of choice is the Cuckoo Search (CS) algorithm. The optimum design of a box girder is characterized by geometry, serviceability and ultimate limit states specified by the American Association of State Highway and Transportation Officials (AASHTO). Size optimization of a practical design example investigates the efficiency of this optimization approach and leads to around 15% of saving in material.