• The Journal of the Korea Contents Association
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• v.15 no.8
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• pp.397-407
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• 2015

Concrete is a attractive construction material, however durability problem occur due to steel corrosion, which leads propagation to structural safety problem. The recently developed FRP (Fiber Reinforced Plastic) Hybrid Bar has an engineering merit of both structural steel and FRP. Accelerated corrosion test for RC (Reinforced Concrete) samples with normal steel and FRP Hybriud Bar are performed and their flexural capacity is evaluated. Furthermore UV(Ultrasonic Velocity) measurement is attempted for analysis of variation of UV due to corrosion condition. After corrosion test, there is no significant reduction in RC beam with FRP hybrid bar but 11.5% of reduction in the case of normal steel is evaluated with 3.3% of UV reduction. For commercial production of FRP hybrid bar, bond strength evaluation through long-term submerged corrosion is required.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.3
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• pp.31-40
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• 2002

The purpose of this study is to investigate the seismic behavior of RC bridge piers and to provide the data for developing improved seismic design criteria. The accuracy and objectivity of the assessment process may be enhanced by the use of sophisticated nonlinear finite element analysis program. A computer program, named RCAHEST(reinforced concrete analysis in higher evaluation system technology), for the analysis of reinforced concrete structures was used. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach is incorporated. n boundary plane at which each member with different thickness is connected, local discontinuity in deformation due to the abrupt change in their stiffness can be taken into account by introducing interface element. The effect of number of load reversals with the same displacement amplitude has been also taken into account to model the reinforcing steel and concrete. In the companion paper, the proposed numerical method for seismic damage evaluation of RC bridge piers is verified by comparison with the reliable experimental results.

• Geomechanics and Engineering
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• v.32 no.1
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• pp.69-84
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• 2023

This paper proposes a novel frame element on Winkler-Pasternak foundation for analysis of a non-ductile reinforced concrete (RC) member resting on foundation. These structural members represent flexural-shear critical members, which are commonly found in existing buildings designed and constructed with the old seismic design standards (inadequately detailed transverse reinforcement). As a result, these structures always experience shear failure or flexure-shear failure under seismic loading. To predict the characteristics of these non-ductile structures, efficient numerical models are required. Therefore, the novel frame element on Winkler-Pasternak foundation with inclusion of the shear-flexure interaction effect is developed in this study. The proposed model is derived within the framework of a displacement-based formulation and fiber section model under Timoshenko beam theory. Uniaxial nonlinear material constitutive models are employed to represent the characteristics of non-ductile RC frame and the underlying foundation. The shear-flexure interaction effect is expressed within the shear constitutive model based on the UCSD shear-strength model as demonstrated in this paper. From several features of the presented model, the proposed model is simple but able to capture several salient characteristics of the non-ductile RC frame resting on foundation, such as failure behavior, soil-structure interaction, and shear-flexure interaction. This confirms through two numerical simulations.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.183-192
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• 2008

Generally, application of steel pipe pile as deep foundation member needs special requirement for the connection method between steel pipe pile and concrete footing. Even though two types of connection method are suggested in the korea highway bridge code, type-B method is prevalent. In this study, vertical, lateral, and tension loading test are done for two types of type B connection to review stress concentration, formation and behavior of imaginary RC column in the footing. Welding type and hook type as the connection method are considered in this study. Test results show that welding type have the more reserve capacity than hook type and the specimens connected by the welding type behave as the imaginary RC column in the footing. However, the specimens connected by the hook type did not behave as the imaginary RC column in the footing but behave as the hinge.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.83-90
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• 2006

This paper investigates experimentally the fire resistance performance and spatting resistance of high performance reinforced concrete column member subjected to fire containing polypropylene fiber(PP fiber) and cellulose fiber(CL fiber). An increase in PP fiber and CL fiber contents, respectively resulted in a reduction of fluidity due to fiber ball effect. Air content is constant with m increase in fiber content. Compressive strength reached beyond 50 MPa. Based on fire resistance test, severe failure occurred with control concrete specimen, which caused exposure of reinforcing bar. No spall occurred with specimen containing PP fiber. This is due to the discharge of internal vapour pressure. Use of CL fiber superior to control concrete in the side of spatting resistance, localized failure at comer of specimen was observed. Corner of specimen had deeper neutralization than surface of specimen. Specimen containing PP fiber had the least damaged area due to spatting. Neutralization depth ranged between 6 and 8 mm Residual compressive strength of specimen containing PP fiber maintained 40%, which is larger than control concrete with 20% of residual strength. Specimen containing CL fiber had 25% or residual strength.

• Journal of the Korea Concrete Institute
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• v.25 no.5
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• pp.517-528
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• 2013

The modular technology has been already applied in automotive industry, plant and shipbuilding industry. Recently, the modular technology was applied in bridge construction. The modular bridge is different from the existing precast bridges in terms of standardized design that the detailed design of members is omitted by using the standard modules; the design of the modular bridge is completed by only assembling the standard modules without design in member level. The girder-type precast modular bridge has been developed as a simply supported bridge. The girder-type precast modular bridge could be applied to the multi-span bridges through the continuity method. The continuity of the girder-type precast modular bridge is achieved by using the link slab which is easy to construction and appropriate to the rapid construction. The link slabs have been used as the type of reinforced concrete structure in US from the 1950's. In 2000's, the link slab using the engineered cementitious concrete (ECC link slab) has been developed. In this study, the RC type link slab which is more reproducible and economic relative to the ECC link slab was used for the continuity of the girder-type precast modular bridges, and the construction detail of RC type link slab was modified. In addition, the modified iterative design method of RC type link slab was proposed in this study. To verify the proposed design method, the flexural tests were conducted using the RC type link slab specimens. Also, the fatigue test using the mock-up specimen was conducted with cyclic loading condition up to two million cycles.

• Earthquakes and Structures
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• v.12 no.1
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• pp.23-34
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• 2017

Composite steel plate deep beam (CDB) is proposed as a lateral resisting member, which is constructed by steel plate and reinforced concrete (RC) panel, and it is connected with building frame through high-strength bolts. To investigate the seismic performance of the CDB, tests of two 1/3 scaled specimens with different length-to-height ratio were carried out under cyclic loads. The failure modes, load-carrying capacity, hysteretic behavior, ductility and energy dissipation were obtained and analyzed. In addition, the nonlinear finite element (FE) models of the specimens were established and verified by the test results. Besides, parametric analyses were performed to study the effect of length-to-height ratio, height-to-thickness ratio, material type and arrangement of RC panel. The experimental and numerical results showed that: the CDBs lost their load-carrying capacity because of the large out-of plane deformation and yield of the tension field formed on the steel plate. By increasing the length-to-height ratio of steel plate, the load-carrying capacity, elastic stiffness, ductility and energy dissipation capacity of the specimens were significantly enhanced. The ultimate loading capacity increased with increasing the length-to-height ratio of steel plate and yield strength of steel plate; and such capacity increased with decreasing of height-to-thickness ratio of steel plate and gap. Finally, a unified formula is proposed to calculate their ultimate loading capacity, and fitting formula on such indexes are provided for designation of the CDB.

• Computers and Concrete
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• v.3 no.1
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• pp.17-28
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• 2006

Replacement of actual stress distribution in a reinforced concrete (RC) flexural member with a simpler geometrical shape, which maintains magnitude and location of the resultant compressive force, is an acceptable conceptual trick. This concept was originally perfected for normal strength concrete. In recent years, high strength concrete (HSC) has been introduced and widely used in modern construction. The stress block parameters require updating to account for special features of HSC in the design of flexural members. In future, more varieties of concrete may be developed and a corresponding design procedure of RC flexural members will be required. The usual practice is to conduct large number of experiments on various sizes of specimen and then evolve an empirical relation. This paper presents a numerical procedure through which the stress block parameters can be numerically derived for a given strain ratio variation. The material model for concrete is presented and computational procedure is described. This procedure is illustrated with several variations of strain ratio. The advantages of numerical procedure are that it costs less and it can be used with new material models for any new variety of concrete.

• Journal of the Earthquake Engineering Society of Korea
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• v.18 no.5
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• pp.241-251
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• 2014

In this study, shaking table test was carried out to evaluate the seismic behavior and performance of low-rise reinforced concrete (RC) piloti structures with and without retrofit. The specimens were designed considering the characteristics of existing building with pilotis such as natural period, distribution factor of strength and stiffness between columns and core wall on the first soft story. The test for the non-retrofit specimen showed that damage was concentrated on the stiffer member on the same floor as the core wall failed by shear fracture whereas columns experienced slight flexural cracks. Considering the failure mode of the non-retrofit specimen, the retrofit method using steel rod damper was presented for improving the seismic performance of piloti structures. The results of the test for retrofit specimen revealed that the retrofit method was effective for controlling the damage as the main RC structural members were not destroyed and most of input energy was dissipated by hysteretic behavior of the damper.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.237-240
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• 2005

As a part of the effort for improving the durability design based on a set of the deem-to-satisfy specifications, it is important and primary to quantitatively identify the environmental impact to a target reinforced concrete structure. In this work, an effort is made to quantitatively calculate the environmental affecting factor with using a fuzzy inference that it indicates the severity of environmental impact to the exposed reinforced concrete structure or member. This system is composed of input region, output region and rule base. For developing the fuzzy inference system surface chloride concentration{chloride), cyclic degree of wet and dry(CWD), relative humidity(RH) and temperature (TEMP) were selected as the input parameter to environmental affecting factor(EAF) of output parameter. The Rules in inference engine are generated from the engineering knowledge and intuition based on some international code of practises as well as various researcher's experimental data. The devised fuzzy inference system was verified comparing the inferred value with the investigation data, and proved to be validated. Thus it is anticipated that this system for quantifying EAF is certain to be considered into the starting point to develop the performance-based durability design considering the service life of structure.