• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 봄 학술발표회 논문집
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• pp.6-11
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• 1993

Due to depleting reserves and environmental pressures, the availability of "good" aggregates, , particularly in many urban areas, has decreased in recent years and from the viewpoint of energy and resources saving, it may be very advantageous to use waste concrete as construction materials. Therefore, this paper, an experimental study on the application in the construction of recycled aggregate concrete, is the experimental program and properties of fresh concrete to investigate general performance and workability of concretef concrete

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.707-716
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• 2011

It has been applied using cranes or insertion methods to install heavy structures to strengthen existing railway bridges. These methods are uneconomical because of two reasons. The first one is it is required to construct approach roads for heavy equipment and/or working yard. The second one is the electric lines shall be cutoff during construction. Both require additional construction cost and duration. In this study, new transport equipment was developed which can be applied to heavy structures up to 100 ton. Using this method, the heavy structure can be loaded into the new transport equipment at working yard and transported to the working site. This method can be applied, but not limited to railway bridge or roadbed rehabilitation. It was found that the precious construction can be achieved to install heavy structure using this method. The experimental construction to make non-ballast girder bridge composite with new pc deck slab using this method was carried out for Jewon bridge. The example bridge is in extreme condition because it locates above national road #38 within extreme transition curve and has 10 ‰ slope and skew. The experimental construction results were satisfactory both for safety and construction precision.

• Steel and Composite Structures
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• 제12권3호
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• pp.261-273
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• 2012

This study proposes and examines a circular composite bridge pier for seismic resistance. The axial and flexural strengths of the proposed bridge pier are provided by the longitudinal reinforcing bars and the concrete, while the transverse reinforcements used in the conventional reinforced concrete pier are replaced by the steel tube. The shear strength of this composite pier relies on the steel tube and the concrete. This system is similar to the steel jacketing method which strengthens the existing reinforced concrete bridge piers. However, no transverse shear reinforcing bar is used in the proposed composite bridge pier. A series of experimental studies is conducted to investigate the seismic resistant characteristics of the proposed circular composite pier. The effects of the longitudinal reinforcing bars, the shear span-to-diameter ratio, and the thickness of the steel tube on the performance of strength, ductility, and energy dissipation of the proposed pier are discussed. The experimental results show that the strength of the proposed circular composite bridge pier can be predicted accurately by the similar method used in the reinforced concrete piers with minor modification. From these experimental studies, it is found that the proposed circular composite bridge pier not only simplifies the construction work greatly but also provides excellent ductility and energy dissipation capacity under seismic lateral force.

• 한국건설순환자원학회논문집
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• 제7권2호
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• pp.78-83
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• 2012

터널현장의 숏크리트 시공에 사용되는 강섬유 보강 숏크리트는 강섬유의 강성이 크고 중량이 무거워 숏크리트 시공상 어려움이 있으며, 강섬유의 부식과 높은 반발률 등이 개선사항으로 요구되고 있다. 이에 본 연구에서는 강섬유 보강 숏크리트의 단점을 개선하기 위하여 폴리아미드섬유를 혼입한 숏크리트를 제안하고, 현장 적용성 평가를 위하여 시험시공 결과를 제시하였으며, 그 결과 다음과 같은 결론을 얻었다. 1) 폴리아미드섬유 보강 숏크리트의 역학적 성능은 국내의 터널관련 설계기준을 만족하며, 기존 강섬유 보강 숏크리트와 동등 수준의 역학적 성능을 나타내었다. 2) 폴리아미드섬유 보강 숏크리트는 강섬유 보강 숏크리트에 비해 시공시 반발률이 저감되어 시공성 뿐만 아니라 경제성, 품질, 친환경성 측면에서 우수한 숏크리트라 할 수 있다.

• Computers and Concrete
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• 제17권4호
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• pp.455-475
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• 2016

Dynamic characteristics, named as natural frequencies, damping ratios and mode shapes, affect the dynamic behavior of buildings and they vary depending on the construction stages. It is aimed to present the effects of construction stages on the dynamic characteristics of reinforced concrete (RC) buildings considering theoretical and experimental investigations. For this purpose, a three-storey RC building model with a 1/2 scale was constructed in the laboratory of Civil Engineering Department at Karadeniz Technical University. The modal testing measurements were performed by using Operational Modal Analysis (OMA) method for the bare frame, brick walled and coated cases of the building model. Randomly generated loads by impact hammer were used to vibrate the building model; the responses were measured by uni-axial seismic accelerometers as acceleration. The building's modal parameters at these construction stages were extracted from the processed signals using the Enhanced Frequency Domain Decomposition (EFDD) technique. Also, the finite element models of each case were developed and modal analyses were performed. It was observed from the experimental and theoretical investigations that the natural frequencies of the building model varied depending on the construction stages considerably.

• Earthquakes and Structures
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• 제16권1호
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• pp.97-107
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• 2019

The frame structures investigated in this paper is composed of Concrete encased columns with L-shaped steel section and steel beams. The seismic behavior of this structural system is studied through experimental and numerical studies. A 2-bay, 3-story and 1/3 scaled frame specimen is tested under constant axial loading and cyclic lateral loading applied on the column top. The load-displacement hysteretic loops, ductility, energy dissipation, stiffness and strength degradation are investigated. A typical failure mode is observed in the test, and the experimental results show that this type of framed structure exhibit a high strength with good ductility and energy dissipation capacity. Furthermore, finite element analysis software Perform-3D was conducted to simulate the behavior of the frame. The calculating results agreed with the test ones well. Further analysis is conducted to investigate the effects of parameters including concrete strength, column axial compressive force and steel ratio on the seismic performance indexes, such as the elastic stiffness, the maximum strength, the ductility coefficient, the strength and stiffness degradation, and the equivalent viscous damping ratio. It can be concluded that with the axial compression ratio increasing, the load carrying capacity and ductility decreased. The load carrying capacity and ductility increased when increasing the steel ratio. Increasing the concrete grade can improve the ultimate bearing capacity of the structure, but the ductility of structure decreases slightly.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.70-75
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• 1999

The purpose of this study is to recycle the waste concrete which is generated in large quantities as crushed stone in construction works. This study deals with the comparative analysis on the construction works and engineering properties of recycled aggregate concrete through physical experiment. The experimental variables are the kinds of aggregates, some different aggregate composition, and W/C ratio(0.40, 0.45, 0.50). It is able to find from the experimental results that the recycled aggregate concrete is good as general concrete on the construction works and engineering propperties. In addition to, the reliable regression analysis equations between compressive strength and various experimental data for recycled aggregate concrete are presented.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.1252-1252
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• 2022

Temporary work that utilizes temporary equipment (e.g., system scaffold and system pipe support) in construction work is one of the most vulnerable work from a safety perspective in South Korea. Typically, temporary equipment is reused at construction sites. The Korea Occupational Safety and Health Agency announced guidelines regarding the performance standards for reusable temporary equipment to prevent the accidental collapse of temporary facilities. Nevertheless, temporary facilities' collapse still occurs, which could be attributed to a degradation in the performance due to the reuse of temporary equipment. Therefore, this study investigated the performance of simple temporary structures assembled with new and reused equipment. To this end, an experimental module was designed based on previous research cases, and two experimental models were constructed, in which one was assembled using new equipment (Model A), and the other was built using reused equipment (Model B). To determine the performance of each model, a load test was conducted to measure the maximum load that each model could withstand. The experimental results revealed that the maximum load of Model B was 15% lower than that of Model A. This indicates that there is a meaningful performance difference between those two models. Based on this result, the authors decided to perform additional tests with more realistic models than previous ones. The new experimental module was designed to ensure compliance with the Korean design guidelines. In this presentation, the authors show details of the first tests and their results and plan for the additional test.

• 한국도로학회논문집
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• 제10권2호
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• pp.193-203
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• 2008

본 연구는 프리캐스트 콘크리트 슬래브를 이용한 급속 신설 도로 포장 공법의 국내 적용성을 분석하기 위한 기초 연구를 수행하고 시험시공을 통해 선설 프리캐스트 포장의 설계 및 시공 지침을 개발하기 위하여 수행되었다. 시험시공을 위해 가로, 세로, 깊이가 각각 실제 포장 슬래브의 1/2 크기인 슬래브를 설계하여 제작하였으며 이에 적합한 철근배근, 종방향과 횡방향의 연결부, 그라우팅 방법 등에 대하여 분석을 수행하였다. 이러한 슬래브를 이용하여 종방향과 횡방향으로 두 개씩 총 4 개의 슬래브를 연결하여 평탄성을 조절한 후 포켓 부분과 슬래브 하부의 공간을 그라우팅 함으로써 시공을 신속 용이하게 수행하였다. 시험 시공을 수행하며 프리캐스트 포장의 설계 및 시공과 관련된 세부 사항을 면밀히 분석하였으며 이에 바탕을 두어 프리캐스트 슬래브를 이용하여 급속하게 신설 도로를 건설할 때의 설계 및 시공 지침을 개발하였다.

• Advances in concrete construction
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• 제5권5호
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• pp.469-479
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• 2017

Balanced cantilever construction is extensively used in the construction of prestressed concrete (PSC) box-girder bridges. Shear-lag effect is usually considered in finished bridges, while the cumulative shear-lag effect in bridges during balanced cantilever construction is considered only rarely. In this paper, based on the balanced cantilever construction sequences of large-span PSC box-girder bridges, the difference method is employed to analyze the cumulative shear-lag effect of box girders with varying depth under the concrete segments' own weight. During cantilever construction, no negative shear-lag effect is generated, and the cumulative shear-lag effect under the balanced construction procedure is greater than the instantaneous shear-lag effect in which the full dead weight is applied to the entire cantilever. Three cross-sections of Jianjiang Bridge were chosen for the experimental observation of shear-lag effect, and the experimental results are in keeping with the theoretical results of cumulative shear-lag effect. The research indicates that only calculating the instantaneous shear-lag effect is not sufficiently safe for practical engineering purposes.