• Magazine of the Korean Society of Agricultural Engineers
• /
• v.40 no.3
• /
• pp.103-112
• /
• 1998

In this study, database schema which is capable of maintaining various design-knowledge and applicable to the structural designs has been presented. Futhermore, by utilizing the database system, RECODSS (REinforced COncrete Design Support System) was developed as well. Knowledge-base that were formulated from the document is constructed by applying the concrete standard specifications of Korea from 1989. The basic drawing was prepared by $AutoCAD^TM$. As an inference in the preliminary design, the certainty function and the interpolation function were presented. The certainty function is made by assuming linear relations between each data while referencing $MYCIN^TM$ (expert systems). Nevertheless, the interpolation function was made by utilizing the linear Lagrange interpolation. For the search of the design-knowledge, fast search algorithm and full-text search algorithm were used, however, the design engine was programmed with C language. RECODSS was applied for designing a slab and a beam member. And the results were compared with the existing results. In conclusion, RECODSS was able to efficiently manage various design knowledge and to introduce stable design results.

• KIEAE Journal
• /
• v.10 no.6
• /
• pp.159-165
• /
• 2010

The composite frame system suggested in this paper consists of steel reinforced concrete beam encased with structural tee and precast concrete column. This system has advantages such as reduction of materials, CO2 emissions and waste. To commercialize the new composite frame system, it is necessary to develop connections that can effectively connect each member. Therefore, a hybrid connection that has steel type connection and reinforced concrete together is utilized to connect easily at the composite frame system. To evaluate the structural performance of the composite frame system, an experimental investigation is presented. In this study, the flexural moment capacity of the composite frame was determined using the strain compatibility approach. The strain compatibility approach can be used to predict the flexural moment capacity at each limit state. As a result, all elements of the beam to column connection are represented to fully interact between each other. The specimens show errors of -1.9% in the yield limit state and 0.9% at the maximum load limit state. Also, testing shows that beam to column connections have characteristics of semi-rigid connection as per Eurocode 3.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.9 no.5 s.45
• /
• pp.29-40
• /
• 2005

The purpose of this study is to investigate the inelastic behavior of precast segmental prestressed concrete bridge piers. 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. An unbonded tendon element based on the finite element method, that can represent the interaction between tendon and concrete of prestressed concrete member, is used. A joint element is newly developed to predict the inelastic behaviors of segmental joints. The proposed numerical method for the inelastic behavior of precast segmental prestressed concrete bridge piers is verified by comparison with reliable experimental results.

• Magazine of the Korea Concrete Institute
• /
• v.11 no.2
• /
• pp.197-208
• /
• 1999

The use of high-strength concrete which permits smaller cross sections, reduced dead loads, and longer spans has been getting more popular in tall buildings. However, there has been little research on behavior of high-strength concrete columns laterally reinforced with square ties and subjected to compressive loading. With the addition of transverse reinforcement which lead to triaxial compressive state, ductility behavior of high-strength column member shall be increased. In this study, rational quality and quantity evaluations were made to investigate the ultimate strength and strain ductility by confinement effect of tie reinforced high-strength concrete columns subject to uniaxial loads. Concrete failure theory at the triaxial compressive state and statistical results based on conventional experimental data were applied for this propose. Up to 185 columns, tested under monotonically increasing concentric loading, were evaluated in terms of strength and strain ductility. Analytical results show that confinement stress, maximum compressive strength, and increase of strain equations were developed with the consideration of concrete strength, yield strength, spacing, volumetric ratio, and configurations of tie reinforcement.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.11 no.1 s.53
• /
• pp.79-87
• /
• 2007

This paper presents an analysis procedures of Joints in precast segmental prestressed concrete bridge piers. 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. An unbended tendon element based on the finite element method, that can represent the interaction between tendon and concrete of prestressed concrete member, is used. A joint element is newly developed to predict the inelastic behaviors of segmental joints. The proposed numerical method for joints in precast segmental prestressed concrete bridge piers is verified by comparison with reliable experimental results.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2009.05a
• /
• pp.225-226
• /
• 2009

Day by day, concrete buildings and structure became high-rising and magnificently vast scheduled, as contributed from the development of improved equipments that suitable to specific construction works and high qualitied Material, the durability of the concrete was highly improved. The temporary elastic reduction occur at vertical members such as walls and columns under vertical loads. Specially, inelastic reduction such as creep and shrinkage occur long termly with elastic one in case of reinforced concrete members. Generally, creep and shrinkage depend on time and this is affected by concrete strength, concrete type, member size, steel ratio, and relative humidity. And elastic reduction rely on time, too because concrete is loaded before revelation of perfect strength in terms of construction conditions. So, tests on mechanical properties of concrete certainly need in order to apply to construction by forecasting an amount of reduction caused by the complex factors. Therefore, in this study the tests on creep, shrinkage are carried out to offer basic data for predicting an amount of long-term Properties at the concrete columns of an object structure, and results of the tests are described.

• Journal of the Korea Concrete Institute
• /
• v.26 no.5
• /
• pp.651-660
• /
• 2014

Structural members using ultra high strength concrete which usually used with steel fiber is designed with guidelines based on several investigation of SF-RPC(steel fiber reinforced reactive powder concrete). However, there are not clear design method yet. Especially, SF-RPC member should be casted with steam(90 degree delicious) and members with SF-RPC usually used with precast members. Although the most important design parameter is development method between SF-RPC and steel reinforcement(rebar), there are no clear design method in the SF-RPC member design guidelines. There are many controversial problems on safety and economy. Therefore, in order to make design more optimum safe design, in this study, we investigated bond stress between steel rebar and SF-RPC according to test. Test results were compared with previously suggested analysis method. Test was carried out with direct pull out test using variables of compressive strength of concrete, concrete cover and inclusion ratio of steel fiber. According to test results, bond stress between steel rebar and SF-RPC increased with increase of compressive strength of concrete and concrete cover. Increasing rate of bond stress were decrease with increase of compressive strength of SF-RPC and concrete cover significantly. 1% volume fraction inclusion of steel fiber increase the bond stress between steel rebar and SF-RPC with two times but 2% volume fraction cannot affect the bond stress significantly. There are no exact or empirical equations for evaluation of SF-RPC bond stress. In order to make safe bond design of SF-RPC precast members, previously suggested analysis method for bond stress by Tepfers were evaluated. This method have shown good agreement with test results, especially for steel fiber reinforced RPC.

• Computers and Concrete
• /
• v.34 no.4
• /
• pp.393-408
• /
• 2024

In recent decades the strengthening of reinforced concrete (RC) structural elements using Fiber-reinforced polymer (FRP) has received much attention. The behavior of RC elements can vary from axial compression to pure bending, depending on their loading. When the compressive behavior is dominant, the FRP jacket application is common, but when the flexural behavior is prevalent, the codes consider the FRP jacket ineffective. Codes suggest applying FRP bars or strips as Near-surface Mounted (NSM) or Externally Bonded (EB) in the tensile face to strengthen the beams under flexure. To strengthen the columns in tension-control mode, some researchers have suggested NSM FRP bars in both tension and compression faces alone or with the FRP jacket (hybrid). However, the number of tests that evaluate the pure bending of the strengthened columns as one of the pivotal points of the axial force-moment interaction curve is limited. In this paper, 11 RC elements strengthened using the NSM (in both tension and compression faces) or hybrid method were subjected to bending to assess the effect of the amount and material type of the FRP bar and jacket and the dimensions of the groove. The test results revealed that the NSM method increased the flexural capacity of the members between 10% to 50%. Furthermore, using the hybrid method increased the capacity between 51% to 91%. Finally, an analytical model was presented considering the effect of the NSM FRP bond in different circumstances, and its results were in good agreement with the experimental results.

• Journal of the Korea Concrete Institute
• /
• v.28 no.3
• /
• pp.365-373
• /
• 2016

Ultra-High-Performance Steel Fiber-Reinforced Concrete (SUPER Concrete) exhibits improved compressive and tensile strengths far superior to those of conventional concrete. These characteristics can significantly reduce the cross sectional area of the member and the anchorage strength of a headed bar is expected to be improved. In this study, the anchorage strengths of headed bars with $4d_b$ or $6d_b$ embedment length were evaluated by simulated exterior beam-column joint tests where the headed bars were used as beam bars and the joints were cast of 120 or 180 MPa SUPER Concrete. In all specimens, the actual yield strengths of the headed bars over 600 MPa were developed. Some headed bars were fractured due to the high anchorage capacity in SUPER Concrete. Therefore, the headed bar with only $4d_b$ embedment length in 120 MPa SUPER Concrete can develop a yield strength of 600 MPa which is the highest design yield strength permitted by the KCI design code. The previous model derived from tests with normal concrete and the current design code underestimate the anchorage capacity of the headed bar anchored in SUPER Concrete. Because the previous model and the current design code do not consider the effects of the high tensile strength of SUPER Concrete. From a regression analysis assuming that the anchorage strength is proportional to $(f_{ck})^{\alpha}$, the model for predicting anchorage strength of headed bars in SUPER Concrete is developed. The average and coefficient of variation of the test-to-prediction values are 1.01 and 5%, respectively.

• Journal of the Architectural Institute of Korea Structure & Construction
• /
• v.33 no.12
• /
• pp.19-27
• /
• 2017

This paper is a study to improve the fire-resistance capacity of reinforced concrete (RC) members strengthened by fiber-reinforced-polymer (FRP). The fire resistance of the RC members strengthened by FRP was evaluated through high temperature exposure test. In order to improve the fire resistance of the FRP reinforcing method, a fire-proof board was attached to the reinforced FRP surface and then the high temperature exposure test was carried out to evaluate the improvement of the fire resistance performance. It was confirmed that the resistance to high temperature of NSMR could be improved somewhat compared with that of EBR from the experiment that exposed to high temperature under the load corresponding to 40% of nominal strength. When 30 mm thick fire-resistance (FR) board is attached to the FRP surface, the surface of the reinforced FRP does not reach $65^{\circ}C$, which is the glass transition temperature (GTT) of the epoxy until the external temperature reaches $480^{\circ}C$. In particular, when a high performance fire-proof mortar was first applied prior to FR board attachment, the FRP portion did not reach the epoxy glass transition temperature until the external temperature reached $600^{\circ}C$.