• Structural Engineering and Mechanics
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• v.58 no.3
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• pp.555-576
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• 2016

In this paper an efficient approach is introduced for design and analysis of double-layer grids including both geometrical and material nonlinearities, while the results are compared with those considering material nonlinearity. Optimum design procedure based on Enhanced Colliding Bodies Optimization method (ECBO) is applied to optimal design of two commonly used configurations of double-layer grids. Two ranges of spans as small and big sizes with certain bays of equal length in two directions are considered for each type of square grids. ECBO algorithm obtains minimum weight grid through appropriate selection of tube sections available in AISC Load and Resistance Factor Design (LRFD). Strength constraints of AISC-LRFD specifications and displacement constraints are imposed on these grids.

• Steel and Composite Structures
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• v.21 no.2
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• pp.303-321
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• 2016

Tubular column members have been widely adopted in current construction due to its numerous advantages. However, the closed-section profile characteristics of tubular columns severely limit the connection possibilities. Welding type is acceptable but discouraged because of on-site issues. Blind-bolted connection is preferable because of its simplicity, economic benefit, and easy assembly. This paper presents a state-of-the-art review on bolted connections to tubular columns for bare steel tubes, including square and circular sections. Available studies on bolted connections at ambient and elevated temperatures are reviewed, but emphasis is given on the latter. Various methods of determining the connection performance through experimental, analytical, component based, and finite element approaches are examined. Future research areas are also identified.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1995.04a
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• pp.195-202
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• 1995

In this study, the optimization program is developed to provide preliminary designs of steel-box girder bridges with minimum cost. The advantages of steel-box girder deck, when comparing with other girder types, are higher torsional rigidity and better resistance against corrosion. To achieve more rational design, systematic design procedure is required, by which the design constraints on steel-box girder are satisfied and the design variables with minimum cost are obtained. In the Proposed optmum design Process, the design variables are forced to be selected from the available discrete value set. The efficiency of the developed program has been verified by companing with previous designed sections and the resulting optimum cost with discrete variables has been compared with those of continuous variables.

• Steel and Composite Structures
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• v.21 no.1
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• pp.109-122
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• 2016

Concrete creep, while significantly changing the static behaviors of concrete filled steel tube (CFST) structures, do alter the structures' dynamic behaviors as well, which is studied quite limitedly. The attempt to investigate the influence of concrete creep on the dynamic property and response of CFST arch bridges was made in this paper. The mechanism through which creep exerts its influence was analyzed first; then a predicative formula was proposed for the concrete elastic modulus after creep based on available test data; finally a numerical analysis for the effect of creep on the dynamic behaviors of a long-span half-through CFST arch bridge was conducted. It is demonstrated that the presence of concrete creep increases the elastic modulus of concrete, and further magnifies the seismic responses of the displacement and internal force in some sections of the bridge. This influence is related closely to the excitation and the structure, and should be analyzed case-by-case.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.355-358
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• 1999

In recent times, large strands have become increasingly popular in the pretensioned prestressed industry and have found wide applications in varying geometries of sections. However, use of such elements and their behavior in several situations have been questioned with respect to anchoring of these strands in concrete. In addition, the experimental results available on bond are limited and information relating to large strands is rare. This study was conducted to determine the influence of some of the inadequately examined properties on transfer length of prestressing strand. The principle variables considered were strand size, concrete strength and clear bottom cover. The experimental results indicate clearly that concrete strength at transfer and cover size influence transfer length significantly. An attempt was made to suggest prediction equation for transfer length including above parameters.

• Journal of Ocean Engineering and Technology
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• v.21 no.2 s.75
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• pp.75-80
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• 2007

The design variables for structural systems, in most practical designs, are chosen from a list of discrete values, which are commercially available sizing. This paper presents the application of Genetic Algorithms for determining the optimum design for two-dimensional structures with discrete and pseudocontinuous design variables. Genetic Algorithms are heuristic search algorithms and are effective tools for finding global solutions for discrete optimization. In this paper, Genetic Algorithms are used as the method of Elitism and penalty parameters, in order to improve fitness in the reproduction process. Examples in this paper include: 10 bar planar truss and 1 bay 8-story frame. Truss with discrete and pseudoucontinuous design variables and steel frame with W-sections are used for the design of discrete optimization.

• Journal of the Korea Concrete Institute
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• v.11 no.5
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• pp.131-137
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• 1999

The use of higher strength materials with the strength methed of design has resulted in more slender member and shallower sections. For this reason, it is necessary to satisfy the requirements of serviceability even though the structural safety is the most important limit state. This paper is only concerned with the control of deflections in the serviceability. In this study, an analytical model is presented to predict the deflections of reinforced concrete beams to given loading and environmental conditions. This model is based on the finite element approach in which a finite element is generally divided into a number of stiffening effect due to cracking, creep and shrinkage. Comparisons are made with available measured deflections reported by others to assess the capability of the layered beam model. The calculated values of instantaneous and long-term deflection show good agreement with experimental results in the range of tension stiffening parameter $\beta$ between 2.5 and 3.0.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.81-85
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• 2005

Three-dimensional steady incompressible laminar entry flows in a square duct of $90^{\circ}$ bend are numerically simulated by a new solution code(PowerCFD) using unstructured cell-centered method. Solutions are obtained with three unstructured grid types of hexahedron, prism and hybrid at a Reynolds number, based on the hydraulic diameter and bulk velocity, of 790. Interesting features of the flow are presented in detail. Detailed comparisons between the computed solutions and the available experimental data are given mainly for the velocity distributions at cross-sections in a $90^{\circ}$ bend of a square duct with fully-developed entry flows. It is found that the code is capable of producing the nature of laminar flow in curved square duct with no grid type dependency.

• Magazine of the Korean Society of Agricultural Engineers
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• v.6 no.2
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• pp.803-808
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• 1964

In this experiment, it was attempted to determine the thermal conductivities of earth block materials which are recently much available for farm building constructions in Korea as lower cost building materials. For this experiment, two kinds of earth block materials were sampled. One of them was pure earth and the other was cementstabilized earth with a ratio of earth to cement by volume, 20 to 1. Cylindrical sections of specimen surrounding a steel pipe(I.D. =1 inch) were used. A resistance neater in the pipe and thermometers for the measurement of radial temperature distribution were installed as shown in Fig. 1 and photograph 1. The heat which flows through the pipe and the sample was produced by passing a current through a resistance wire stretched along the pipe axis. The complete apparatus used in this experiment is schematically shown in Fig. 1.

• Structural Engineering and Mechanics
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• v.28 no.2
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• pp.221-238
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• 2008

Numerical solution to buckling analysis of beams and columns are obtained by the method of differential quadrature (DQ) and harmonic differential quadrature (HDQ) for various support conditions considering the variation of flexural rigidity. The solution technique is applied to find the buckling load of fully or partially embedded columns such as piles. A simple semi- inverse method of DQ or HDQ is proposed for determining the flexural rigidities at various sections of non-prismatic column ( pile) partially and fully embedded given the buckling load, buckled shape and sub-grade reaction of the soil. The obtained results are compared with the existing solutions available from other numerical methods and analytical results. In addition, this paper also uses a recently developed technique, known as the differential transformation (DT) to determine the critical buckling load of fully or partially supported heavy prismatic piles as well as fully supported non-prismatic piles. In solving the problem, governing differential equation is converted to algebraic equations using differential transformation methods (DT) which must be solved together with applied boundary conditions. The symbolic programming package, Mathematica is ideally suitable to solve such recursive equations by considering fairly large number of terms.