• Land and Housing Review
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• v.2 no.2
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• pp.183-188
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• 2011

Recently, the depth of tunnel constructed is getting deeper, which increases difficulty in construction works. Deliberate tunneling techniques are needed as the span and length of tunnels are increased. As one of the technical developments for tunnel, U-shaped and reinforced spider lattice girders are developed by optimizing the spider used in 95mm lattice girder as tunnel steel ribs. In order to evaluate the load bearing capacity of the lattice girder, the 4-point flexural tests are carried out. For the laboratory tests, straight specimens are made for the existing lattice girder and the new lattice girder. The results of the flexural tests showed that the maximum load bearing capacity of the new lattice girders was higher than the traditional one. The load-displacement behavior of the test specimens showed the elasto-plastic behavior in the existing lattice girder and the stress softening behavior in the new lattice girder. It was found that the load bearing capacities are changed depending on the location of the loading points.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.10-17
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• 2015

In this paper, to evaluate and verify safety and performance of new-concept lining board, the experiments and analyses were performed. From the flexural tests, it was noted that the failure occurred at the load of 664kN. At structural analyses based on test results, when the loadings are the unit load 100kN and failure load 664kN, the maximum displacements at the middle part of lining board were 2.58mm and 27.01mm, respectively. In addition, at the elastic range and the plastic range, their load carrying capacities were evaluated as DB-34 and DB-41, respectively. Accordingly, it can be concluded that, since the lining board developed in this study satisfy the design load and structural safety, it supplemented its disadvantages and can apply to construction site.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.183-193
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• 2008

The reliability analysis of simply-supported and continuous composite plate girder and box girder bridges under flexure was performed to provide a basic data for the development of LRFD c ode. The bridges were designed based on LRFD specification with newly proposed design live load which was developed by analyzing traffic statistics from highways and local roads. A performance function for flexural failure was expressed as a function of the flexural resistance of composite section and the design moments due to permanent load and live load. For the flexural resistance, the statistical parameters obtained by analyzing over 16,000 domestic structural steel samples were used. Several different values of bias factors for the live load moment from 1.0 to 1.2 were used. Due to the lack of available domestic measured data on the moment by permanent loads, the same statistical properties used in the calibration of ASHTO-LRFD were ap plied. The reliability indices for the composite girder bridges with various span lengths, different live load factors, and bias fact or for the live load were obtained by applying the Rackwitz-Fiessler technique.

• Computers and Concrete
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• v.17 no.1
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• pp.29-51
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• 2016

Tension-stiffening is the contribution of concrete between the cracks to carry tensile stresses after cracking in Reinforced Concrete (RC) members. In this paper, a tension-stiffening model has been proposed for computationally efficient nonlinear analysis of RC flexural members subjected to service load. The proposed model has been embedded in a typical cracked span length beam element. The element is visualized to consist of at the most five zones (cracked or uncracked). Closed form expressions for flexibility and stiffness coefficients and end displacements have been obtained for the cracked span length beam element. Further, for use in everyday design, a hybrid analytical-numerical procedure has been developed for nonlinear analysis of RC flexural members using the proposed tension-stiffening model. The procedure yields deflections as well as redistributed bending moments. The proposed model (and developed procedure) has been validated by the comparison with experimental results reported elsewhere and also by comparison with the Finite Element Method (FEM) results. The procedure would lead to drastic reduction in computational time in case of large RC structures.

• Journal of Korean Society of Steel Construction
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• v.29 no.1
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• pp.61-71
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• 2017

The flexural behavior of composite ring stiffened by GFRP and steel pipe is presented in this paper. The effective width is required to construct FEM beam element model to verify the composite flexural behavior of stiffened ring of cylindrical shell structure. The experimental results are compared with the theoretical and FEM results by commercial program ABAQUS to verify the effective width coefficient. The yield, crack and ultimate loads is calculated using theoretical strains that varies depending on yield state and compared with experiment result and FEM results by ABAQUS solid model.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.4
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• pp.201-210
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• 2000

The Rehabilitation and repair of structurally deteriorated reinforced concrete structure become more necessary as time goes by. The goal of this study is that provide the data about flexural retrofitted effect of RC beam strengthened by Steel Plate. In order to provide the data, 6 specimens were manufactured and divided with standard specimen and damaged degree A, B, C. Division of damaged A, B, C is based on deflection and degree of crack. In the determination of deflection and degree of crack, we loaded standard specimen to failure under two-point bending to find yielding load and failure load, and then we found deflections and degree of crack that correspond to 75%, 100%, 105% of the yielding load of standard specimen respectively. When we are compared with standard specimen and strengthened specimens, we founded from the experimental results that flexural capacity of structurally damaged beam strengthened by Steel Plate incremented highly, ductility was decreased, and energy absorbtion capacity was almost same.

• Journal of the Korea Concrete Institute
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• v.11 no.3
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• pp.141-152
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• 1999

Precast prestressed double-tee slab may be designed by the PCI Design Handbook. It is based on the bridge construction and is required for reorganization for the use of buildings in the domestic construction environments. Much enhanced sections are developed from the reforming process on the determined design factors in the previous experimental works on double tees. Pre-determined shape, reinforcement detail, and 5000 psi concrete strength can not be expected as the best solution for the domestic construction requirements because large amount of use on that systems are anticipated. Flexural tests are performed on four full-scale 12.5m proto-type models, "least depth double tee", which are resulted from the optimization process. Domestic superimposed live load regulation, domestic material properties which is available to product, building design requirements and economy in construction are considered as the main factors to establish. the first two sections are double tee section for 1.2 ton/$\m^2$ market live load with straight and one-point depressed strands and the second two are for 0.6 ton/$\m^2$ parking live load with those strand types. All of the specimens tested fully comply with the flexural strength requirements as specified by ACI 318-95. However, the research has shown that following improved considerations are needed for better result in practice. The locations and method of connection for the lowest bottom mild bar, connection method between precast and cast-in-place concrete, and dap-end reinforcement are need to be improved.

• Journal of the Korean Society of Safety
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• v.27 no.5
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• pp.117-125
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• 2012

In recent years, polymer concrete based on polyester resin have been widely generalized and the research of polymer concrete have been actively pursued by the technical innovations. Polymer concrete is a composite consisting of aggregates and an organic resin binder that hardens by polymerization. Polymer concrete are stronger by a factor of three or more in compression, a factor of four to six in tension and flexural and a factor of two in impact when compared with portland cement concrete. In view of the growing use of polymer concrete, it is important to study the physical characteristics of the material, emphasizing the short term properties as well as long term mechanical behavior. If polymer concrete is to be used in flexural load-bearing application such as in beam, it is imperative to understand the deformation of the material under sustained loading conditions. This study is proposed to empirical and mechanical model of polymer concrete tension creep using long-term experimental results and mathematical development. The test results showed that proposed model has been used successfully to predict creep deformations at a stress level that was 20 percent of the ultimate strength and viscoelastic behavior of recycled-PET polymer concrete is linear of stress level up to 30 percent. It is expected that the present model allows more realistic evaluation of varying stresses in polymer concrete structures with a constant loading.

• Structural Engineering and Mechanics
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• v.35 no.2
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• pp.141-173
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• 2010

In this paper a boundary element method is developed for the general flexural-torsional buckling analysis of Timoshenko beams of arbitrarily shaped cross section. The beam is subjected to a compressive centrally applied concentrated axial load together with arbitrarily axial, transverse and torsional distributed loading, while its edges are restrained by the most general linear boundary conditions. The resulting boundary value problem, described by three coupled ordinary differential equations, is solved employing a boundary integral equation approach. All basic equations are formulated with respect to the principal shear axes coordinate system, which does not coincide with the principal bending one in a nonsymmetric cross section. To account for shear deformations, the concept of shear deformation coefficients is used. Six coupled boundary value problems are formulated with respect to the transverse displacements, to the angle of twist, to the primary warping function and to two stress functions and solved using the Analog Equation Method, a BEM based method. Several beams are analysed to illustrate the method and demonstrate its efficiency and wherever possible its accuracy. The range of applicability of the thin-walled theory and the significant influence of the boundary conditions and the shear deformation effect on the buckling load are investigated through examples with great practical interest.

• Structural Engineering and Mechanics
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• v.75 no.5
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• pp.595-605
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• 2020

In this study, the flexural behaviors of full-scale prestressed concrete box girders are experimentally investigated. Four girders were fabricated using two types of concrete (compressive strengths: 50 MPa and 70 MPa) and tested under four-point bending until failure. The measured parameters included the deflection, the stress and strain in concrete and steel bars, and cracks in concrete. The measurement results were used to analyze the failure mode, load-bearing capacity, and deformability of each girder. A finite element model is established to simulate the flexural behaviors of the girders. The results show that the use of high-performance concrete and reasonable combination of prestressed tendons could improve the mechanical performance of the box girders, in terms of the crack resistance, load-carrying capacity, stress distribution, and ductility.