• Magazine of the Korea Concrete Institute
• /
• v.2 no.4
• /
• pp.99-107
• /
• 1990

The transfer of forces across the interface by bond between concrete and steel is of fundamentul importance to many aspects of reinforced concrete behavior. Bond stress-slip relationships were studied using a symmetri¬cal tension test specimen. This type of test is intended to simulate conditions in the tension zone of a concrete beam between primary cracks and below the neutral axis. These relationships between local bond stress and local slip are found to be quite different at different locations along the bar. The bond behavior under cyclic lo¬ading is also studied in the present study, and the increase of bond slip and steel strains is clarified from those tests.

• Journal of the Korean Society of Industry Convergence
• /
• v.23 no.2_2
• /
• pp.361-374
• /
• 2020

Recently, small and medium-sized rahmen-type bridges have been developed as a technology that ensures the stability of structural behavior and the safety of use at the same time by using efficient and economical materials that make up the convergence section of reinforced bar, structural steel and concrete. This study is about a rahmen-type structure applied with the installation and dismantling of the strut. It improves the serviceability of the structure by forming multi-points and efficiently applies the convergence section of structural steel and concrete materials to the structural system changes to induce the displacement improvement effect additionally. By constructing mock-up models for the beam-column joint, the displacement was calculated and compared, and this was compared and analyzed by numerical analysis. The final displacement showed an improvement effect of 13.46% to 36.28% based on the vertical displacement of the existing structure without struts through the experiment of the mock-up models. As a result of analysis by numerical analysis method, the displacement improvement effect of 42.89% could be derived.

• Structural Engineering and Mechanics
• /
• v.61 no.6
• /
• pp.693-700
• /
• 2017

Concrete cover cracking due to the corrosion of steel reinforcing bars is one of the main causes of deterioration in Reinforced Concrete (RC) structures. The oxidation level of the bars causes varying levels of expansion. The rebar expansions could lead to through-thickness cracking of the concrete cover, where depending on the cracking characteristics, the service life of the structures would be affected. In this paper, the effect of geometrical and material parameters, i.e., concrete cover thickness, reinforcing bar diameter, and concrete tensile strength, on the required pressure for concrete cover cracking due to corrosion has been investigated through detailed numerical simulations. ABAQUS finite element software is employed as a modeling platform where the concrete cracking is simulated by means of eXtended Finite Element Method (XFEM). The accuracy of the numerical simulations is verified by comparing the numerical results with experimental data obtained from the literature. Using a previously proposed empirical equation and the numerical model, the time from corrosion initiation to the cover cracking is predicted and then compared to the respective experimental data. Finally, a parametric study is undertaken to determine the optimum ratio of the rebar diameter to the reinforcing bars spacing in order to avoid concrete cover delamination.

• Journal of Korean Society of Steel Construction
• /
• v.9 no.3 s.32
• /
• pp.457-465
• /
• 1997

The Shape optimization makes it possible to reduce the weight of structure and cost then member sizing optimization. A vast amount of imprecise information is existed in constraints of the optimum design. It is very difficult and sometimes confusing to describe and to deal with the several criteria which contain fuzzy degrees of relatives importance. This paper proposed weighting strategies in the multiobjective shape optimization of fuzzy structural system by ${\alpha}$-cut approach. The algorithm in this research is numerically tested for 2-bar truss structure. The result show that. the user can choose the one optimum solution in practices as obtaining the optimum solutions according to the ${\alpha}$-cut approach, weight of volume and displacement.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.48 no.1
• /
• pp.61-68
• /
• 2006

The p-version nonlinear finite element model has been developed to analyze the nonlinear behavior of simply supported RC slabs strengthened with carbon fiber reinforced plastic sheets. The shape function is adopted with integral of Legendre polynomials. The compression model of concrete is based on the Kupfer's yield criterion, hardening rule, and crushing condition. The cracking behavior is modeled by a smeared crack model. In this study, the fixed crack approach is adopted as being geometrically fixed in direction once generated. Each steel layer has a uniaxial behavior resisting only the axial force in the bar direction. Identical behavior is assumed fur tension and compression of steel according to the elastic modulus. The carbon fiber reinforced plastic sheets are considered as reinforced layers of equivalent thickness with uniaxial strength and rigidity properties in the present model. It is shown that the proposed model is able to adequately predicte the displacement and ultimate load of nonlinear simply supported RC slabs by a patch with respect to reinforcement ratio, thickness and angles of CFRP sheets.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.357-360
• /
• 2008

This study was performed to estimate the workability and the static behavior for Bi Prestressed Concrete Girder(Bicon girder) which could introduce effectively prestressed forces into concrete girders. A bicon girder is manufactured by means of introducing pure bending moment that prestress simultaneously the compressive member(steel bar) and the tensile member(steel tendon). Static test was executed for 20m railway bridge girder specimen and evaluated whether pure bending moment was introduced or not, and the behaviors after cracking, and at the ultimate load. Test results showed that a bicon girder had the enough safety in the introduction of pure moment, the serviceability, and the ultimate behavior.

• Steel and Composite Structures
• /
• v.5 no.5
• /
• pp.375-394
• /
• 2005

An experimental study was conducted to develop a new base plate anchorage system for concrete filled tubular column under an axial load and a moment. The column was connected to a concrete foundation using ordinary deformed reinforcing bars that are installed at the inside and outside of the column. In order to investigate the moment resisting capacity of the system, horizontal cyclic loads are applied until the ultimate condition is reached with the axial load held constant. To derive a design method for moment resisting capacity, the reinforced concrete section approach was investigated with the assumption of strain compatibility. The results by this approach agreeded well with those of experiments when the bearing pressure of confined concrete and tangent modulus of steel bars are assumed appropriately. Also, it was found that the column interaction curve can be used to predict the yield strength of the base plate system.

• Journal of the Korea Concrete Institute
• /
• v.11 no.3
• /
• pp.171-179
• /
• 1999

The present research investigated the interaction among loading level, corrosion rate and flexural deflection of reinforced concrete beams. 10cm$\times$15cm$\times$110cm reinforced concrete beams were prepared and subjected to different levels of flexural loading, including 0%, 45% and 75% of the ultimate load. The beams with either a pre-load or a sustained load were also exposed to a laboratory environment with ponding and wetting/drying cycling at room temperature. Half cell potential and galvanized current measurements were taken to monitor corrosion process of reinforcing steel. After corrosion initiation, external current was applied to some of the beams to accelerate corrosion propagation. The beam deflections were recorded during the entire tests. The results indicate that loading level has significant effect on corrosion rate. The beams under a sustained load had much higher corrosion rate than the pre-loaded and then unloaded beams. Significant corrosion may result in an increase in beam deflection and affect serviceability of the structure. The present research may provide an insight into structural condition evaluation and service life predictions of reinforced concrete.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.46 no.3
• /
• pp.73-81
• /
• 2004

FRP reinforcing bars(rebars) are produced through a variety of manufacturing process includes pultrusion, and filament winding and braiding etc. Each manufacturing method produces a different surface condition of FRP rebar. The surface properties of FRP rebar is an important property for mechanical bond with concrete. Current methods of providing surface deformation to FRP rebars include helical wrapping, surfaces and coating and rib molding. The problem with the helical wrapping method is that it can not provide enough surface deformation for good bond and it can be easily sheard off from the FRP rebars. Sand coating and rib molding provide surface deformation only to the outer FRP skins. Therefore, FRP rebar has about 60% of bond strength of steel rebar. The main objective was to evaluate the bond properties of FRP rebar after environmental exposure. Five types of FRP rebar includes CFRP ISO, GFRP Aslan, AFRP Technora CFRP(Korea), and GFRP(Korea) rebars performed direct bond tests. Also, FRP rebar bond specimens were subjected to exposure conditions including alkaline solution, acid solution, salt solution and deionized water etc. According to bond test results, CFRP(Korea) and CFRP(Korea) rebars were found to have better bond strength with concrete than previous FRP rebars. Also, FRP(Korea) rebar had more than about 70% in bond strength of steel rebar.

• Journal of Korean Society of Steel Construction
• /
• v.18 no.2
• /
• pp.279-288
• /
• 2006

A stud connector was used by the shear connector of a composite beam. The shear connector is an important element in heightening the composition rate of a composite beam .study was based on the experiments conducted on 15 specimens using the push-out test.In this paper, through an experiment, the shear connector of other forms was analyzed instead of the stud connector. It is hoped that this application can be used in composite beams.