• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.3
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• pp.51-65
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• 2009

The seismic design concept of RC bridges is to attain the proper ductility of piers, yielding a ductile failure mechanism. Therefore, seismic design force for moment is determined by introducing a response modification factor (R), and lateral reinforcements to confine core concrete are specified in the current design code. However, these design provisions have irrationality, which results in excessive amounts of lateral reinforcements for columns in Korea, which are generally designed with large sections. To improve on these provisions, a new design method based on seismic performance has been proposed. To apply this to hollow sectional columns, however, further investigations and improvements must be performed, due to the different seismic behaviors and confinement effects. In this study, hollow sectional columns with different lap-splice of longitudinal bars and lateral reinforcements have been tested. Seismic characteristics and performance were investigated quantitatively. These research results can be used to derive a performance-based design for hollow sectional columns.

• International Journal of Concrete Structures and Materials
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• v.11 no.2
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• pp.327-341
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• 2017

Openings in slabs are usually required for many different applications such as aeriation ducts and air conditioning. Opening in concrete slabs due to cutouts significantly decrease the member stiffness. There are different techniques to strengthen slabs with opening cutouts. This study presents experimental and numerical investigations on the use of Carbon Fiber Reinforced Polymers (CFRP) as strengthening material to strengthen and restore the load carrying capacity of R.C. slabs after having cutout in the hogging moment region. The experimental program consisted of testing five (oneway spanning R.C. flat slabs) with overhang. All slabs were prismatic, rectangular in cross-section and nominally 2000 mm long, 1000 mm width, and 100 mm thickness with a clear span (distance between supports) of 1200 mm and the overhang length is 700 mm. All slabs were loaded up to 30 kN (45% of ultimate load for reference slab, before yielding of the longitudinal reinforcement), then the load was kept constant during cutting concrete and steel bars (producing cut out). After that operation, slabs were loaded till failure. An analytical study using finite element analysis (FEA) is performed using the commercial software ANSYS. The FEA has been validated and calibrated using the experimental results. The FE model was found to be in a good agreement with the experimental results. The investigated key parameters were slab aspect ratio for the opening ratios of [1:1, 2:1], CFRP layers and the laminates widths, positions for cutouts and the CFRP configurations around cutouts.

• Journal of Korean Association for Spatial Structures
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• v.16 no.2
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• pp.61-68
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• 2016

Behavior of RC(Reinforced-concrete) beam-column connections has been subjected to the earthquake loading has been determined by shear and attachment mechanism. However, since the shear and attachment are very fragile for cycle loadings. Through occurring plastic hinges at the beam, the column and the connection should remain elastic condition and the beam should dissipate the energy from the earthquake. This study was investigate on the seismic performance of 6 RC beam - column connections built with the high strength reinforcements (700MPa) based on design and detailing requirements in the ACI 318-05 Provision and KCI-07 appendix II. This is aimed to evaluate the effect of the high-strength reinforcements as used the beam-column connection members. The main comparisons were the seismic performance of the connections affect the seismic performance in terms of strength, stiffness and ductility, joint shear stress-strain. A total of 6 beam-column specimens were built with a 1/2 scale and subjected to the cyclic loadings. Main design considerations were the area of the longitudinal reinforcements of the beam and details of the beam-column joint designed based on the seismic code. Cyclic test results are given and recommendations for the usage of high strength reinforcements for the seismic design is provided.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.1-11
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• 2006

This paper presents a seismic fragility analysis method for a cable-stayed bridge with energy dissipation devices. Model uncertainties represented by random variables include input ground motions, characteristics of energy dissipation devices and the stiffness of cable-stayed bridge. Using linear regression, we established demand models for the fragility analysis from the relationship between maximum responses and the intensity of input ground motions. For capacity models, we considered the moment and shear force of the main tower, longitudinal displacement of the girder, deviation of the stay cables tension and the local buckling of the main steel tower as the limit states for cable-stayed bridge. As a numerical example, fragility analysis results for the 2nd Jindo bridge are presented. The effect of energy dissipation devices is also briefly discussed.

• Magazine of the Korea Concrete Institute
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• v.6 no.4
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• pp.153-160
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• 1994

Ten Half precast concrete slabs reinforced with welded deformed wire fabric were tested under two concentrated loads to investigate the flexural moment and ductile capacity. The test variables were the compressive strength of topping concrete, quantitative roughness, and reinforcernent ratio. The effects of each test variables were studied separately. Test results were as followings. The ultimate strength design method is applicable to predict flexural strength for Half P.C. concrete slab with welded deformed wire fabric and quantitative roughness. It is proper to consider 0.0035 strain ;is yielding stress of the welded deformed wire fabric. The ductility index of Half precast concrete slab with welded deformed wire fabric showed lower value. Therefore to enhance the ductility capacity the normal defomed bar should be used with the welded deformed wire fabric for the longitudinal reinforcement.

• Journal of the Korean GEO-environmental Society
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• v.11 no.11
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• pp.5-18
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• 2010

In this paper, a 3-dimensional stiffened plate model for soil-metal box structures is proposed. 3-dimensional stiffened plate model is enable to model corrugated steel plates of soil metal box culverts considering section modulus and section properties of longitudinal and horizontal direction from a corrugated steel plate. Loading conditions which causes maximum displacement and maximum moment according to the step construction stages(a back filling to the top of the plate, a back filling to the maximum depth of cover, and loading of live loads) was applied and the behaviors of the soil metal box culverts was analyzed. Analysis results of 3-dimensional stiffened model were compared with those of 2-dimensional model, 3-dimensional equivalent plate model and 3-dimensional corrugated plate model. As results, the behaviors of 2-dimensional model and 3 dimensional equivalent model are different from 3-dimensional corrugated plate model but the result of 3-dimensional stiffened model has good agreement with that of 3-dimensional corrugated plate model.

• Computers and Concrete
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• v.20 no.4
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• pp.391-407
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• 2017

Fiber reinforced polymer (FRP) bars have been recently used to reinforce concrete members in flexure due to their high tensile strength and especially in corrosive environments to improve the durability of concrete structures. However, FRPs have a low modulus of elasticity and a linear elastic behavior up to rupture, thus reinforced concrete (RC) components with such materials would exhibit a less ductility in comparison with steel reinforcement at the similar members. There were several studies showed the behavior of concrete beams with the hybrid combination of steel and FRP longitudinal reinforcement by adopting the experimental and numerical programs. The current study presents a numerical and analytical investigation based on the data of previous researches. Three-dimensional (3D) finite element (FE) models of beams by using ANSYS are built and investigated. In addition, this study also discusses on the design methods for hybrid FRP-steel beams in terms of ultimate moment capacity, load-deflection response, crack width, and ductility. The effects of the reinforcement ratio, concrete compressive strength, arrangement of reinforcement, and the length of FRP bars on the mechanical performance of hybrid beams are considered as a parametric study by means of FE method. The results obtained from this study are compared and verified with the experimental and numerical data of the literature. This study provides insight into the mechanical performances of hybrid FRP-steel RC beams, builds the reliable FE models which can be used to predict the structural behavior of hybrid RC beams, offers a rational design method together with an useful database to evaluate the ductility for concrete beams with the combination of FRP and steel reinforcement, and motivates the further development in the future research by applying parametric study.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.6
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• pp.219-225
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• 2011

Advanced composite structures are too difficult for such design engineers for construction and some simple but accurate enough methods are necessary. The simply supported laminated plates are analyzed by the specially orthotropic laminates theory. This method, however, may be too difficult for some practising engineers. In this paper, the result of analysis for such plate by means of the beam theory with unit width is reported. The plate aspect ratio considered is from 1 : 1 to 1 : 5. Most of the bridge and building slabs on girders have large aspect ratios. For such cases further simplification is possible by neglecting the effect of the longitudinal moment terms($M_x$) on the relevant partial differential equations of equilibrium. In this paper. the influence of the aspect ratio on the natural frequency of the specially orthotropic laminated plates is studied and it is concluded that the method used is sufficiently accurate for engineering purposes. The result of this paper can be used for simply supported laminated plates analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1523-1531
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• 2011

Multi-axle driving vehicle are favored for military use in off road operations because of their high mobility on extreme terrains and obstacles. Especially, Military Vehicle needs an ability to driving on hills of 60% angle slope. This paper presents the improvement of the ability of hill climbing for 6WD/6WS vehicle through the optimal tire force distribution method. From the driver's commands, the desired longitudinal force, the desired lateral force, and the desired yaw moment were obtained for the hill climbing of vehicle using optimal tire force distribution method. These three values were distributed to each wheel as the torque based on optimal tire force distribution method using friction circle and cost function. To verify the performance of the proposed algorithm, the simulation is executed using TruckSim software. Two vehicles, the one the proposed algorithm is implemented and the another the tire's forces are equivalently distributed, are compared. At the hill slop, the ability to driving on hills is improved by using the optimum tire force distribution method.

• Journal of the Korean Institute of Gas
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• v.12 no.2
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• pp.57-62
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• 2008

Difference of failure modes was studied by finite element analysis for elbows with local wall thinning area particularly at inner surface of intrados of the elbow. Longitudinal wall thinning length, minimum thickness were kept constant but circumferential wall thinning width was varied to get $90^{\circ}$, $180^{\circ}$ and $360^{\circ}$ thinning width. Elastic-plastic analysis were carried out under the combined loading conditions of internal pressure and in-plane bending moment closing the elbow. Von Mises stress were obtained from the outer surface central surface location in intrados, extrados and crown parts in elbow. The results showed that the plastic deformation and failure started from the crown location when the thinning width small ($90{\sim}180^{\circ}$). However, plastic collapse started from the intrados location when the thinning width is approaching $360^{\circ}C$. This should be reflected to assess structural integrity of elbows after wall thinning measurement is made.