• Structural Engineering and Mechanics
• /
• 제9권1호
• /
• pp.89-97
• /
• 2000

A modified constitutive model has been developed for nonlinear finite element analysis of axisymmetric reinforced concrete structures, and then implemented into an existing finite element program. By comparing with the experimental results available, the present model has been validated.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
• /
• pp.611-614
• /
• 2005

This study concerns the strength of concrete cores drilled from existing structures. The test factors are core size, drilled position of core, concrete age and concrete strength. The test results are as follows; (1) Under the filled condition of curing, concrete strength for three years are larger than that of 28 days by $15\~20\%$ (2) According to the core size effect from diameter of 75mm to 150mm , the variation of core strength are by $8\~18\%$ (3) According to the wall height of 1m, the strength of lower point of wall is than larger that of the upper point by $5\~20\%$. (4) In Accessing the core strength of concrete as a basis, the effect of core size and drilling position should be considered.

• Computers and Concrete
• /
• 제22권1호
• /
• pp.11-25
• /
• 2018

A numerical approach for the evaluation of the flexural response of Steel Fibrous Concrete (SFC) cross-sections with arbitrary geometry, with or without conventional steel longitudinal reinforcing bars is proposed. Resisting bending moment versus curvature curves are calculated using verified non-linear constitutive stress-strain relationships for the SFC under compression and tension which include post-peak and post-cracking softening parts. A new compressive stress-strain model for SFC is employed that has been derived from test data of 125 stress-strain curves and 257 strength values providing the overall compressive behaviour of various SFC mixtures. The proposed sectional analysis is verified using existing experimental data of 42 SFC beams, and it predicts the flexural capacity and the curvature ductility of SFC members reasonably well. The developed approach also provides rational and more accurate compressive and tensile stress-strain curves along with bending moment versus curvature curves with regards to the predictions of relevant existing models.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
• /
• pp.743-746
• /
• 1999

One of the main deteriorating factors that affect the service life of concrete structures is the corrosion of reinforcement. The chlorides penetrate the concrete, destroy the passive layer surrounding the steel, and help initiate the steel corrosion. A Corrosion Prediction System(CPS) has been developed to assist the engineer in analyzing the service life of existing sea-shore structures and future concrete repairs by calculate the chloride diffusion in concrete. The CPS calculates mixing design, physical properties or recent chloride profiles. The CPS can be used to evaluate changes in concrete cover, chloride loads, and environmental conditions in different structural designs.

• Steel and Composite Structures
• /
• 제47권6호
• /
• pp.729-741
• /
• 2023

As the most popular shear connection in composite structures, mature concrete has been widely investigated by considering mechanical properties of stud connectors (SCs) embedded. To further enhance the fabrication efficiency of composite structures and solve the contradiction between construction progress and structural performance, it is required to analyze the shear performance of stud connections of composite structures with different concrete ages. 18 typical vertical push-out tests were carried out on stud shear connectors at concrete ages of 7 days, 14 days, and 28 days. Also, the effects of concrete age, stud spacing and stud diameter on the shear capacity, connection stiffness and failure mode of the connectors were studied. A new relationship expression of load-slip for SCs with various concrete ages was proposed. The existing design code for the SCs shear strength was evaluated according to the experimental data, and a more practical prediction equation for the shear capacity of SCs with different concrete ages was established. A great agreement was observed between the experimental and theoretical results, which can provide a reference for engineering practices.

• 한국공간구조학회논문집
• /
• 제20권3호
• /
• pp.81-89
• /
• 2020

As the damage caused by earthquakes gradually increases, seismic retrofitting for existing public facilities has been implemented in Korea. Several types of structural analysis methods can be used to evaluate the seismic performance of structures. Among them, for nonlinear dynamic analysis, the hysteresis model must be carefully applied because it can significantly affect the behavior. In order to find a hysteresis model that predicts rational behavior, this study compared the experimental results and analysis results of the existing non-seismic reinforced concrete frames. For energy dissipation, the results were close to the experimental values in the order of Pivot, Concrete, Degrading, and Takeda models. The Concrete model underestimated the energy dissipation due to excessive pinching. In contrast, the other ones except the Pivot model showed the opposite results with relatively little pinching. In the load-displacement curves, the experimental and analysis results tended to be more similar when the column axial force was applied to columns.

• 한국공간구조학회논문집
• /
• 제4권3호
• /
• pp.85-91
• /
• 2004

최근 FRP(fibre-reinfored plastic)를 이용하여 기존 RC구조물을 보수보강하는 방법이 각광받고 있다. CFRP plate나 sheet의 형태로 외부에 부착하는 방법이 FRP보강의 주류를 이루어 왔으나, 판단부에서 발생되는 응력집중으로 부착판이 박락하여 조기 파괴되는 경우가 많은 연구를 통해서 밝혀졌다. 따라서 기존 콘크리트구조물에 홈을 형성하여 FRP막대의 형태로 외부에 매립함으로써 이러한 조기파괴의 개선하려는 공법이 개발되었다. 본 실험은 이러한 매립형공법의 보강효율을 조사하고, 각국에서 제시하고 있는 기존 휨 이론에 대한 적용여부를 검토함에 그 목적이 있다.

• 한국공간구조학회논문집
• /
• 제22권4호
• /
• pp.99-107
• /
• 2022

Existing reinforced concrete building structures constructed before 1988 have seismically-deficient reinforcing details, which can lead to the premature failure of the columns and beam-column joints. The premature failure was resulted from the inadequate bonding performance between the reinforcing bars and surrounding concrete on the main structural elements. This paper aims to quantify the bond-slip effect on the dynamic responses of reinforced concrete frame models using finite element analyses. The bond-slip behavior was modeled using an one-dimensional slide line model in LS-DYNA. The bond-slip models were varied with the bonding conditions and failure modes, and implemented to the well-validated finite element models. The dynamic responses of the frame models with the several bonding conditions were compared to the validated models reproducing the actual behavior. It verifies that the bond-slip effects significantly affected the dynamic responses of the reinforced concrete building structures.

• International Journal of Concrete Structures and Materials
• /
• 제10권1호
• /
• pp.99-112
• /
• 2016

During earthquake, reinforced concrete walls show complicated post-yield behavior varying with shear span-to-depth ratio, re-bar detail, and loading condition. In the present study, a macro-model for the nonlinear analysis of multi-story wall structures was developed. To conveniently describe the coupled flexure-compression and shear responses, a reinforced concrete wall was idealized with longitudinal and diagonal uniaxial elements. Simplified cyclic material models were used to describe the cyclic behavior of concrete and re-bars. For verification, the proposed method was applied to various existing test specimens of isolated and coupled walls. The results showed that the predictions agreed well with the test results including the load-carrying capacity, deformation capacity, and failure mode. Further the proposed model was applied to an existing wall structure tested on a shaking table. Three-dimensional nonlinear time history analyses using the proposed model were performed for the test specimen. The time history responses of the proposed method agreed with the test results including the lateral displacements and base shear.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
• /
• pp.601-604
• /
• 2006

Reinforcement corrosion is the most important durability problem of reinforced concrete structures. One of the important factors affecting the steel corrosion is carbonation. However, existing carbonation test takes several months to obtain the results. Therefore, in this study, new rapid carbonation test equipment for concrete was developed and its applicability was investigated. The testing period can be reduced by increasing $CO_2$ concentration up to 100% in the equipment. It is found from the test results that the carbonation depth of concrete specimens tested for 2 weeks was $3{\sim}5$ times greater than that of specimens tested by existing test method. In conclusion, it would be possible to get the reliable test results enough to evaluate the durability of concrete structures in a short-period.