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.

본 논문은 준등방성 적층 섬유배열된 FRP보강재로 보강된 철근콘크리트보의 휨 보강 설계에 대하여 소개하고 있다. 본 논문에서는 첫 번째로 FRP보강재의 적층설계와 그 적층부재의 물성값 해석이 수행되었다. 마지막으로 여러 개의 준등방성 적층구조로 보강된 철근콘크리트보에 대한 휨 해석이 수행되었다. 그 결과값은 직교차 적층 구조를 갖는 RC보와 비교되었다. 따라서 본 연구가 준등방성 적층구조의 FRP보강재로 보강된 노후 RC보의 휨 설계의 지침서가 될 수 있을 것이다.

본 연구에서는 섬유보강콘크리트(SFRC) 구조물의 수치해석을 위한 K&C모델의 보정기법을 소개하였다. SFRC 1축 및 3축 압축강도 실험결과를 기반으로 보정을 수행하였으며, 단일요소 해석결과를 실험결과와 비교함으로써 보정 기법의 검증을 수행하였다. 또 한, 변형률 속도의 영향을 반형하기 위해 동적증가계수(DIF)를 고려하여 SFRC 구조물의 발사체 관통해석을 수행함으로써 보정기법의 적용 가능성을 확인하였다.

Existing reinforced concrete building structures have seismic vulnerabilities due to their seismically-deficient details resulting in non-ductile behavior. The seismic vulnerabilities can be mitigated by retrofitting the buildings using a fiber-reinforced polymer column jacketing system, which can provide additional confining pressures to existing columns to improve their lateral resisting capacities. This study presents dynamic responses of a full-scale non-ductile reinforced concrete frame retrofitted using a fiber-reinforced polymer column jacketing system. A series of forced-vibration testing was performed to measure the dynamic responses (e.g. natural frequencies, story drifts and column/beam rotations). Additionally, the dynamic responses of the retrofitted frame were compared to those of the non-retrofitted frame to investigate effectiveness of the retrofit system. The experimental results demonstrate that the retrofit system installed on the first story columns contributed to reducing story drifts and column rotations. Additionally, the retrofit scheme helped mitigate damage concentration on the first story columns as compared to the non-retrofitted frame.

In this study, natural period formular is presented for a RC shear wall structure with H-, T-, and L-shaped wall sections. The natural period formular proposed by Goel and Chopra and adopted in ASCE 7-10 was modified by using the ratio of the flange and web wall area. The natural periods of structures with H-shaped wall were numerically obtained, the results indicated that the ASCE 7-10 could not consider the natural period variation according to the length of the flange wall, but the proposed formula could do. Especially, ASCE 7-10 estimated much longer periods than eigenvalue analysis, and this implies that conservative seismic design is difficult. The periods by eigenvalue analysis exist between the upper and lower bounds given by the proposed formula, and conservative design is possible by using the proposed lower bound value. In order to verity the effectiveness of the proposed method, actual residential buildings with various types of flange walls are considered. Ambient vibration tests, eigenvalue analyses, and nonlinear dynamic analyses were conducted and the periods were compared with the values by ASCE 7-10 and the proposed formula. The results showed that the proposed formula could estimate more accurately the periods than ASCE 7-10.

When reinforcing an existing reinforced concrete beam-column building with a precast concrete panel, special connection between the PC member and the RC member is required to solve the time dependent deformation of the RC member and to receive the large shear forces. The aim of this study is to obtain the shear strength of upper connection between the existing RC beam-column and infilled PC wall panels in experimentally and theoretically. Thus, the static shear loading tests were conducted on the 6 specimens with the plate connection. Shear failure was resulted from the weakest portion of interior PC panel, exterior RC, and the connection, when the PC portion which located at the center of specimen was pulled upward from the bottom. T he experimental result was compared with analytical result from ACI 318M-14 Chapter 17 for the shear strength of post-installed anchor and PCI Handbook 7th edition 6.8 Structural Steel Corbel (PCI Design Handbook 7th edition, 2010) for the strength of cast-in H-beam. The analytical and experimental results show final failure at the same location. The failure loading of experiment showed larger than average 6% to that of the analysis.

본 논문은 철근콘크리트 구조물의 지진해석에 관한 국제 벤치마크 프로젝트인 SMART-2013을 통해 3차원 비대칭 철근콘크리트 건물의 고유진동수와 재료 비선형성을 고려한 지진응답을 계산한 결과를 제시한다. 이를 위해 콘크리트와 철근의 비선형 재료모델을 구성하고 대표부피요소에 대한 국부테스트를 수행하여 비선형 모델의 성능을 평가하였다. 이러한 SMART-2013 철근콘크리트 건물의 비선형 유한요소모델에 대해 모드해석과 저강도 지진하중에 대한 선형 시간이력해석을 수행한 결과, 구조물의 고유진동수, 변위 및 가속도 시간이력이 SMART-2013 프로젝트에서 제시한 실험값들과 유사하였다. 또한 Northridge 지진에 대한 변위 및 가속도 응답의 시간이력과 최대층간상대변위의 응답스펙트럼을 계산하여 고강도 지진 하중에 대한 이 철근콘크리트 건물의 거동을 평가하였다.

Earthquake resistance design has been developed many countries like Japan, USA, Mexico, New Zealand etc., which countries have experienced many earthquakes. Nowadays, earthquake resistance design has come into worldwide use. In Korea, the seismic design regulations have been established since 1988 in order to minimize the economic losses. Recently performance based design method has been adopted as a new Earthquake resistance design method. These regulations, however, are targeted for newly constructed buildings, In Korea, there are no regulations for existing buildings that built before 1988. On the other hand, in Japan and USA, the seismic performance evaluation is coded. In Japan, the evaluation index which can measure seismic performance has been made. So, we need to prepare the regulations that evaluate the seismic performance, furthermore proper retrofitting design guideline needs to be proposed when remodeling old buildings. In this research, various seismic performance evaluation methods which are being used in Japan and USA are reviewed in order to establish seismic performance evaluation index for those existing old structures in Korea.

This paper studied the efficiency of retrofitting of reinforced concrete structure which was not designed to endure an earthquake. The earthquake in Kobe, Japan showed that there was a great possibility of having an earthquake even in big city and the damages were concentrated on mid or low story buildings which were not considered to be protected from an earthquake. This experiment used reinforced concrete structure which restrained side-by-side displacement-to test durability against an earthquake. This study deals with the structural performance of reinforced concrete frame structures strengthened with steel materials.

철근콘크리트부재가 갖는 균열의 발생, 항복 및 파괴 등의 단계별 역학적 거동의 특성을 정확히 예측하고 모사할 수 있는 해석기법의 개발을 목적으로 하였다. 이를 위해서 균열발생후의 철근과 콘크리트의 부착거동, 균열면에서의 골재의 맞물림 거동 및 철근항복후의 모델링 등에 의해서 반복하중을 받는 철근콘크리트 구조부재의 항복후 파괴거동을 예측할 수 있는 해석모델을 개발하였다. 두께가 서로 다릉 부재간의 접합부에서는 단면강성이 급변하기 때문에 기초의 바닥으로부터 철근의 인발, 접합면의 미끄러짐 및 접합면의 관입 등의 국소적인 불연속 변형이 집중하게 된다. 이와 같은 국소적인 불연속 교각구조의 변형능력에 미치는 기여도는 일반적으로 무시할 수 없는 정도이므로, 불연속 변형을 고려하기 위한 접합요소(joint element)를 도입하였다. 또한 축방향철근 및 횡방향 구속철근의 유무 및 그 양 등에 따른 구속효과를 적절히 표현할 수 있는 해석모델을 개발하였다. 각각의 해석모델들을 조합한 유한요소 해석프로그램에 의한 결과를 다른 연구자들의 결과와 비교하여 타당성을 검증하였다.

이 연구에서는 철근콘크리트 부재에서 일반콘크리트를 대신하여 고인성 섬유보강 콘크리트를 사용하였을 때의 내진성능 향상효과를 평가하고자 하였다. 일정한 크기의 축하중을 받는 상태에서 단자유도 RC기둥 부재의 비선형 Push-Over 해석 방법을 적용하여 내진성능평가를 실시하였다, 일반콘크리트를 사용한 경우와 안장변형률성능에 따라 네 가지 고인성 섬유보강 콘크리트를 적용하여 그 거동을 비교하였다. 해석결과, 고인성 섬유보강 콘크리트를 사용한 철근콘크리트 기둥부재는 인장변형률성능이 거의 없는 일반 콘크리트를 사용한 철근콘크리트 기둥부재와 비교했을 때, 항복하중은 25~37% 크게 나타났으며, 변위연성도도 6.0~8.3% 크게 나타나는 것을 확인하였다.

This study is to evaluate the seismic demand of reinforced concrete structure considering the incident angle of the ground motions. For this purpose, a three-story structure is numerically analyzed under the three ground motion records through a multi-component incremental dynamic analysis (MIDA). The MIDA, an implementation of Incremental dynamic analysis, investigates two components of seismic excitation in which all accelerations are scaled to spectral accelerations at the fundamental natural periods of the buildings. The obtained results indicate the influence of the incident angle should be considered in the assessment response of structures. Maximum inter-story drift of structure will behave in the elastic or inelastic range depending on the variable incident angle

When reinforcing an existing reinforced concrete beam-column building with a precast concrete panel, special connection between the PC member and the RC member is required to solve the time dependent deformation of the RC member and to receive the large shear forces. The aim of this study is to obtain the shear strength of upper connection between the existing RC beam-column and infilled PC wall panels in experimentally and theoretically. Thus, the static shear loading tests were conducted on the 6 specimens with the plate connection. Shear failure was resulted from the weakest portion of interior PC panel, exterior RC, and the connection, when the PC portion which located at the center of specimen was pulled upward from the bottom. The experimental result was compared with analytical result from ACI 318M-14 Chapter 17 for the shear strength of post-installed anchor and PCI Handbook 7th edition 6.8 Structural Steel Corbel (PCI Design Handbook 7th edition, 2010) for the strength of cast-in H-beam. The analytical and experimental results show final failure at the same location. The failure loading of experiment showed larger than average 6% to that of the analysis.

When reinforcing an existing reinforced concrete beam-column building with a precast concrete panel, special connection between the PC member and the RC member is required to solve the time dependent deformation of the RC member and to receive the large shear forces. The aim of this study is to obtain the shear strength of upper connection between the existing RC beam-column and infilled PC wall panels in experimentally and theoretically. Thus, the static shear loading tests were conducted on the 6 specimens with the plate connection. Shear failure was resulted from the weakest portion of interior PC panel, exterior RC, and the connection, when the PC portion which located at the center of specimen was pulled upward from the bottom. The experimental result was compared with analytical result from ACI 318M-14 Chapter 17 for the shear strength of post-installed anchor and PCI Handbook 7th edition 6.8 Structural Steel Corbel (PCI Design Handbook 7th edition, 2010) for the strength of cast-in H-beam. The analytical and experimental results show final failure at the same location. The failure loading of experiment showed larger than average 6% to that of the analysis.

Concrete behaves as a brittle material with low tensile strain capacity. By adding fibers, the cracking in concrete matrix is controlled, and the durability is improved. In this study, the microstructure and Chloride diffusion resistance of fiber reinforced concrete are compared with fiber type and fiber volume fraction. From the results, the fiber mixed in concrete must be at least 0.5% regardless fiber type, in order to ensure the chloride diffusion coefficient higher than OPC at 91days. However, the micro structure distribution is affected with fiber volume fraction and fiber type at range 10~100nm.

The purpose of this study is to evaluate the impact on flexural strength and compressive strength of the concrete, the mixing rate of the amorphous fibers.

On this study, carbonation rate and W/C ratio were estimated by collecting actual data of each carbonation depth and compression strength from inner wall, outer wall, stair hall, and balcony floor of certain remodeling apartments. Through above tests, this study can be reference data of the method of life time prediction for the apartments that subject to remodel.

산간 지형이 많은 국내 여건상 물류수송 및 교통 등을 위한 터널 구조물의 활용성은 매우 높다. 최근 현장에서는 공기단축 및 원가절감을 위하여 터널 굴착과 라이닝 콘크리트의 타설을 병행하는 공법이 진행되면서 굴착에 의한 진동 등의 영향으로 콘크리트 구조물 초기 재령에서 균열 및 내구성능 저하 문제가 발생하고 있다. 본 연구에서는 터널 라이닝용 콘크리트 배합에 있어서 보강재를 강섬유와 더불어 최근 국내에서 개발된 폴리아미드 섬유를 병행 사용한 콘크리트의 역학적 특성을 실험적으로 검토하였다. 또한 유․무기 섬유보강 터널 라이닝 콘크리트 부재의 하중-변위와 하중-변형률 관계를 모형 실험으로 평가하였다. 실험 결과, 보통 콘크리트에 강섬유와 폴리아미드 섬유 보강재를 하이브리드화하여 사용한 콘크리트 부재에서 구조 성능이 증진됨을 확인할 수 있었다.