This paper presents the effect of recycled aggregate on the structural design in replacement of natural aggregate. As an actual structure, the concrete airshaft in a subway under construction was chosen and design-criteria obtained from experiments in association with different ratios of recycled aggregate were applied. It was found from the analysis that recycled aggregate can be applied to real concrete structures considering just strength concept and also if other unknown problems such as quality, serviceability and so on be solved.

This study is to prepare prediction method of the durability establishment for the effective maintenance of reinforced concrete substation structures. For this study, we investigated research trends about the foreign practices relating durability design.

In this research, new structural design and manufacturing method of atypical irregular UHPC structural members were newly introduced. The atypical irregular UHPC member was optimized to design from the conventional rectangular section and a method of nonuniform formwork system was newly created to manufacture the irregular member. The specimens were evaluated by analysis and the newly designed member was improved in bending performance by 2.6 times compared to conventional rectangular concrete beams.

The extent damages of concrete structures due to fire occurrence are evaluated. The evaluation of fire safety is evaluated by using the inspection, non-destruction test, fracture test(concrete SEM analysis, concrete heat analysis, rebar fracture test. The criteria for determining the safety of concrete structures are presented using evaluation results.

In this study, an experimental study of Impulse Thermography was carried out on a concrete specimen with in-placed artificial defects at different depths and dimensions. Then, all the data were processed by Pulse Phase Thermography technique by performing Fast Fourier Transformation. The results were compared with the absolute contrast method.

기존의 LB-DECK는 레티스바와 현장에서 배근되는 철근과의 간섭이 시공성 등을 저하시키는 문제점이 지적되고 있었다. HB-DECK는 레티스바의 형태를 단순화하고, 방향을 주철근 방향에서 배력근 방향으로 전환하였으며 강성을 증가시키기 위해 하면에 리브를 설치하였다. 본 연구에서는 HB-DECK가 프리캐스트 콘크리트 슬래브로써 성능을 발휘할 수 있는지를 검증하고자 하였다. 이를 위해 도로교설계기준(2015)에 의한 구조검증과 HB-DECK와 현장타설 콘크리트와의 합성거동 분석을 위해 정적재하시험을 수행하였다. 범용구조해석 프로그램인 MIDAS FEA를 이용하여 3차원 유한요소해석을 수행하였으며, 해석결과와 실험결과를 비교분석하였다. 그 결과, HB-DECK는 현장타설 콘크리트와 완전한 합성거동을 하는 것으로 나타났으며, 도로교설계기준(2015)에서 요구하는 구조성능을 만족하는 것으로 나타났다.

프리캐스트 바닥판 공법은 바닥판간 이음부가 존재하며, 이음부의 연결성능에 따라 전체 교량 구조물의 성능이 좌우되므로 이음부 의 연결성능 확보가 중요한 요소이다. 본 연구에서는 고강도 강섬유보강콘크리트(High Strength Fiber Reinforced Concrete, HSFRC)가 적용된 비대칭 요철형 이음단면을 갖는 연결형식을 제안하였으며, 이음부의 단면형태, 철근 겹침이음길이 및 겹침이음 형식에 따른 구조실험을 수행 하여 제안된 연결형식의 휨 성능을 평가하였다. 실험결과, 이음부 상세에 관계없이 이음철근은 항복변형률 수준의 인장변형을 나타내었으며, 제안된 연결형식은 충분한 휨 저항성능을 확보하는 것으로 나타났다. 이러한 실험결과는, 현행 도로교설계기준의 최소 겹침이음길이에 대한 규정은 이음부 채움재로 HSFRC를 적용한 프리캐스트 바닥판 이음부에서는 보수적인 규정임을 알 수 있다. 따라서 이음부 채움재로 HSFRC 를 사용함에 의해 철근 겹침이음 상세의 단순화 및 이음부 폭의 감소가 가능하며, 제안된 연결형식은 프리캐스트 바닥판 이음부에 효과적으로 적용 가능할 것으로 판단된다.

일반적으로, 원전구조물은 다량의 철근이 사용되어 시공과정에서 여러 잠재적 문제점이 발생한다. 특히, 구조부재의 연결부위는 수많은 갈고리철근, 매입철물과 주변 철근 등에 의해 심각한 과밀현상이 발생하므로 여타 다른 부위보다 콘크리트 타설에 더 큰 어려움이 야기 된다. 원전구조물에 사용되는 일반강도(ASTM A615 Gr.60)의 대구경(43 mm & 57 mm) 표준갈고리 철근을 대신하여 고강도(ASTM A615 Gr.80)의 대구경(43 mm & 57 mm) 확대머리 철근을 사용할 수 있도록 관련 기술기준을 개정하여 철근 과밀배근 문제를 해결하는 데 본 연구의 목적이 있다. 확대머리 철근을 원전구조물에 효과적으로 사용하기 위해서는 기존의 정착성능을 그대로 유지하거나 그 이상으로 증가시키면서 사용 제한요건을 완화는 방안을 찾아야 하므로 철근직경, 철근 항복강도, 측면피복 두께와 같이 확대머리 철근의 사용을 제한하는 변수 영향을 검토할 수 있는 실험결과를 분석하여 정착성능을 평가하였다.

본 연구에서는 지하 콘크리트 구조물의 누수 균열에 사용되는 주입형 누수보수재료의 품질관리 방안으로 규격화된 국제표준 ISO TS 16774, Part 2 Test method for chemical resistance를 이용하여 현재 우리나라 누수보수현장에서 사용하고 있는 주입형 누수보수재료 2계열 (합성고무계, 시멘트계), 3종류 씩, 총 9 종류의 보수재료에 대한 지하 콘크리트 구조물이 처한 화학적 환경의 저항 안정성을 연구·검토하였다. 그 결과, 합성고무계는 RG-3를 제외하고, 산에 대한 저항력을 높일 수 있는 재료적 검토가 필요하고, 시멘트계는 수산화나트륨, 염화나트륨에 대한 저항을 높일 수 있는 재료적 검토의 필요성이 확인되었다. 이러한 결과는 콘크리트 구조물의 화학적 환경에서의 보수재료 선정 시 기본 지 표로 사용가능 할 것으로 판단된다. 또한, 추후에 연구 개발 되는 보수재료의 품질 향상에 반영할 수 있는 기준 자료의 활용을 기대할 수 있다.

The main cause of corrosion in reinforced concrete is diffusion of degradation factors such as chloride ions, carbon dioxide, and sulfate ions. To monitor the extent of the corrosion in reinforced concrete, it is necessary to recognize and track the diffusion of degradation factors. In this paper, we suggest thin-film iron sensorto measure the penetration of chloride ions. The sensor indicates results as electrical resistance and change in electrical resistance. The sensor and contact pad are connected by an anisotropic conducting film (ACF) bonding in order to reduce the influence of the contact electrical resistance. The sensor’s electrical resistance increases with corrosive behavior and external chloride ion concentration. Use of these thin-film iron sensors enables measurement and monitoring of the depth of chloride ion diffusion in concrete.

The purpose of this study is to provide basis data that can be used to establish an efficient maintenance system for the corrosion of off-shore structures by comparatively analyzing the present offshore concrete and steel structure corrosion sensors and monitoring techniques under development.

This study aims to establish design and construction procedure in the fields of the repair and rehabilitation for existing concrete structures. The codes used in this study are ISO 16311 and ACI 562-16. The ISO 16311 and ACI 562-16 focused on maintenance and repair, respectively. After, we will make to design and construction guidelines to meet the domestic situation through analysis the repair and rehabilitation parts of the codes in detail.

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

It was studied structural design of nonuniform UHPC concrete structural members. UHPC concrete has the compressive strength of 120-200MPa, the tensile strength of 8-20MPa, and the tensile strain of 1.0-5.0%. There are two types of specimens of nonuniform members improved in bending and shear performances. The specimens were evaluated by beam load test induced by bending and shear failures.

Soundless Chemical Demolition Agent (SCDA) has been spotlighted for demolition of concrete structure or rock near or in urban areas and historical places since it does not produce dust or rock fragmentations compared to explosive and gas pressure blasting methods. However, there is no guideline or design code for the demolition of existing structures using SCDA. In this study, numerical analysis using ABAQUS is conducted in order to find a minimum required pressure for the initiation of crack in concrete body with SCDA and obtained results in this study could be a basic data for design of hole spacing for the demolition of the structures using SCDAs.

The purpose of this study is to evaluate the effect of steel fiber reinforced concrete on structural performance when applied to joints. For this purpose, the development length was designed not to satisfy the concrete structure criterion. Experimental results show that the maximum strength of steel fiber reinforced concrete increases by about 12% in the direction of the settling force. Also, due to the increase of the tensile strength of the concrete, the strength of the cracks increased by 33% in the positive direction.

The purpose of this research is to consider the qualitative and quantitative performance of reinforced concrete deteriorations using active infrared thermography (IRT) technique. An experiment of five different cases of environmental conditions was conducted on a concrete slab in laboratory. A comparison of the IRT results between normal and reinforced concrete is also discussed. The results showed that the absolute contrast between defective area and non-defective area increases with the increment of ambient temperature. Besides, the values of absolute contrast above delamination obtained from normal concrete showed high than those under effect of reinforcing steel bar.

Many existing RC Buildings were built before the seismic code was established, they need seismic retrofit performance. In this study, presents the evaluations of seismic performance and displacement ductility for two type RC Frames : existing RC frame without SRF(Super Reinforcement with Flexibility) and RC frames strengthened with SRF.