• Structural Engineering and Mechanics
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• 제65권2호
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• pp.183-190
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• 2018

The prestressed concrete (PSC) technology that was first developed by Freyssinet has significantly improved over the past century in terms of materials and structural design in order to build longer, slender, and more economic structures. The application of prestressing method in structures, which is determined by the pre-tension or post-tension processes, is also affected by the surrounding conditions such as the construction site, workforce skills, and local transportation regulations. This study proposes a prestressed concrete girder design based on a hybrid segment concept. The adopted approach combines both pre-tension and post-tension methods along a simple span bridge girder. The girder was designed using newly developed 2400 MPa PS strands and 60 MPa high-strength concrete. The new concept and high strength materials allowed longer span, lower girder depth, less materials, and slender design without affecting the lateral stability of the girder. In order to validate the applicability of the proposed hybrid prestressed segments girder, a full-scale 35 m girder was fabricated, and experimental tests were performed under various fatigue and static loading conditions. The experimental results confirmed the feasibility of the proposed long-span girder as its performance meets the railway girder standards. In addition, the comparison between the measured load-displacement curve and the simulation results indicate that simulation analysis can predict the behavior of hybrid segments girders.

• 대한토목학회논문집
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• 제32권2A호
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• pp.65-73
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• 2012

본 연구에서는 PSC 거더교의 장경간 적용을 위해 개발된 Half-Decked PSC 거더의 구조적 성능을 실험하였다. 이를 위해 힌지-롤러의 지점 조건의 단순교로 설계된 60 m 경간의 실물 크기 거더를 제작하여 4점 재하실험을 수행하였다. 거더의 중앙을 기준으로 양쪽으로 5.5 m 씩 떨어진 위치에 가력장치를 설치 후 1 kN/sec의 속도로 하중을 재하하여 총 4단계에 걸쳐 반복하중을 가하였다. 1단계부터 4단계까지 1,000 kN, 1,200 kN, 1,500 kN, 2,000 kN의 하중을 재하하고 제거하기를 반복하며 거더의 변위, 콘크리트와 철근의 변형률, 균열 등을 확인하였다. 이를 분석하여 거더의 내하력을 평가하고 하중 제거 시 나타나는 복원력 등을 살펴보았다. 1,400 kN 인근에서 초기 휨균열이 발생하여, 이 시점부터 하중 재하 시 비선형 성이 나타나며 뚜렷한 잔류변형이 계측되었다. 초기 균열이 1등교 기준의 사용하중보다 2배 이상 큰 하중에서 계측되어 충분한 내하력을 갖고 있는 것으로 나타났다. 실험 결과의 검증을 위해 수치해석을 수행하여 결과 값을 비교하였고 그 결과 실험 결과와 해석 결과의 유사한 거동을 확인하였다. 본 연구에서 개발된 거더의 정적재하실험을 통하여 그 구조적 성능을 입증하였으며, 이를 바탕으로 Half-Decked PSC 거더 형식의 60 m 경간 실교량 설계 적용 가능성을 확인하였다.

• Steel and Composite Structures
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• 제11권4호
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• pp.291-305
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• 2011

The new structure consisting of continuous compound spiral hoop reinforced concrete (CCSHRC)column and steel concrete composite (SCC) beam has both the advantages of steel structures and concrete structures. Two types of beam-to-column connections applied in this structural system are presented in this paper. The connection details are as follows: the main bars in beam concrete pass through the core zone for both types of connections. For connecting bar connection, the steel I-beam webs are connected by bolts to a steel plate passing through the joint while the top and bottom flanges of the beams are connected by four straight and two X-shaped bars. For bolted end-plate connection, the steel I-beam webs are connected by stiffened extended end-plates and eight long shank bolts passing through the core zone. In order to study the seismic behaviour and failure mechanisms of the connections, quasi-static tests were conducted on both types of full-scale connection subassemblies and core zone specimens. The load-drift hysteresis loops show a plateau for the connecting bar connection while they are excellent plump for bolted end-plate connection. The shear capacity formulas of both types of connections are presented and the values calculated by the formula agree well with the test results.

• Steel and Composite Structures
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• 제46권3호
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• pp.417-433
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• 2023

The maximum ductility and cumulative ductility of connection joints of Buckling-Restrained Braced Frames (BRBF) are critical to the structural overall performance, which should be matched with the BRB ductility. The two-story and one-span BRBF with a one-third scale was tested under cyclic quasi-static loading, and the top-flange beam splice (TFBS) rotational connections were proposed and adopted in BRBF. The deformation capacity of TFBS connections was observed during the test, and the relationship between structural global ductility and local connection ductility was studied. The rotational capacity of the beam-column connections and the stability performance of the BRBs are highly relevant to the structural overall performance. The hysteretic curves of BRBF are stable and full under large displacement demand imposed up to 2% story drift, and energy is dissipated as the large plastic deformation developed in the structural components. The BRBs acted as fuses and yielded first, and the cumulative plastic ductility (CPD) of BRBs is 972.6 of the second floor and 439.7 of the first floor, indicating the excellent energy dissipation capacity of BRBs. Structural members with good local ductility ensure the large global ductility of BRBF. The ductile capacity and hysteretic behavior of BRBF with TFBS connections were compared with those of BRBF with Reduced Beam Section (RBS) connections in terms of the experimental results.

• 대한조선학회논문집
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• 제41권6호
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• pp.24-32
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• 2004

The effects of guide vanes and tip clearances on the characteristics nf axial flow fans are investigated both computationally and experimentally. Performance test of fans carried out in full scale shows considerable effects of tip clearance between rotor tip and duct on the characteristics of fans. The tested results are compared with the computation based on the finite volume method to solve the Navier-Stoke equations with $textsc{k}$-$\varepsilon$ turbulence model. The comparison shows good agreements between experimental and computational results. In addition, the effects of shape of guide vanes are numerically studied. The results show that increased volume of separated region around the guide vane reduces the recovery of tangential component of kinetic energy in the wake, resulting in loss of efficiency

• Steel and Composite Structures
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• 제35권5호
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• pp.641-657
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• 2020

A unique lightweight string truss deployable bridge assembled by thin-walled fiber reinforced polymer (FRP) and metal profiles was designed for emergency applications. As a new structure, investigations into the static structural performance under the serviceability limit state are desired for examining the structural integrity of the developed bridge when subjected to unsymmetrical loadings characterized by combined torsion and bending. In this study, a full-scale experimental inspection was conducted on a fabricated bridge, and the combined flexural-torsional behavior was examined in terms of displacement and strains. The experimental structure showed favorable strength and rigidity performances to function as deployable bridge under unsymmetrical loading conditions and should be designed in accordance with the stiffness criterion, the same as that under symmetrical loads. In addition, a finite element model (FEM) with a simple modeling process, which considered the multi segments of the FRP members and realistic nodal stiffness of the complex unique hybrid nodal joints, was constructed and compared against experiments, demonstrating good agreement. A FEM-based numerical analysis was thereafter performed to explore the effect of the change in elastic modulus of different FRP elements on the static deformation of the bridge. The results confirmed that the change in elastic modulus of different types of FRP element members caused remarkable differences on the bending and torsional stiffness of the hybrid bridge. The global stiffness of such a unique bridge can be significantly enhanced by redesigning the critical lower string pull bars using designable FRP profiles with high elastic modulus.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1990년도 가을 학술발표회 논문집
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• pp.47-54
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• 1990

접합부에서 급격한 불연속성을 가진 프리캐스트 콘크리트(P.C) 대형판 구조는 붕괴에 이르기까지의 구조적인 거동이 일체식 콘크리트 구조와 매우 상이하다. 또한 극심한 지진과 같은 횡하중이 작용할 경우 그 최대 붕괴하중과 붕괴청상을 파악하는 것은 매우 중요한 과제이다. 본 연구에서는 2층 실물크기 P.C 시험체에 대한 정적 실험결과를 토대로 비선형 해석 전산 프로그램인 ANSR를 사용하여 P.C 구조물의 비선형 거동을 예측하고 실험에서 관찰할 수 없는 최종 붕괴시까지의 내부 응력의 분포 및 변화를 연구하였다.

• 한국지진공학회논문집
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• 제14권6호
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• pp.55-65
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• 2010

본 실험 연구의 목적은 횡방향 정적가력을 통하여 2층 R.C 전단벽식 구조의 내진성능을 평가하는 것이다. 본 연구의 실험체는 대상 건물의 개구부를 가지는 T자형 벽체 1층과 2층의 일부분을 대상으로 실물크기의 3/5 크기정도로 축소하였고, 인방보의 유 무를 실험변수로한 2개의 실험체를 제작하여 횡방향의 정적가력 실험을 수행하였다. 인방보 유무에 따른 벽체의 구조적 성능 및 거동의 차이를 비교한 결과, 인방보가 있는 실험체가 인방보가 없는 실험체보다 최대내력과 연성능력 등의 내진성능이 우수한 것으로 판단되었다.

• 대한토목학회논문집
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• 제35권4호
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• pp.747-757
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• 2015

이 연구에서는 이동식 곡선거푸집으로 제작된 현장제작 곡선 PSC 거더의 정적거동을 조사하는 것이 주요 목적이다. 다양한 곡선선형 제작이 용이한 이동식 곡선거푸집을 이용하여 현장에서 제작된 지간 30m, 곡선반경 80m인 곡선 PSC 거더에 대한 재하시험이 수행되었다. 모든 시험결과는 수치해석결과와 비교되었으며, 거더의 중앙부에 대한 변위와 변형률이 측정되었다. 실험결과에서 실물모형 시험체의 초기균열발생 하중은 사용하중보다 1.3배 증가한 하중에서 발생하였다. 또한, 연성설계기준을 만족하여 시험체는 초기균열 발생 후에 취성파괴되지 않고 연성 파괴될 것으로 판단되었다. 사용성 검토에서 균열발생 시의 처짐값이 도로교설계기준(2010)에서 제시한 활하중 재하 시의 허용처짐량을 만족하였다. 유한요소 해석결과와 시험결과는 전체적인 거동이 매우 유사하게 나타났으며, 현장제작 곡선 PSC 거더의 사용성과 안전성 측면에서는 큰 문제가 없는 것으로 판단된다.

• Structural Engineering and Mechanics
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• 제66권1호
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• pp.1-14
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• 2018

Column is usually floating on the stone base directly with or without positioning tenon in traditional Chinese timber structure. Vertical load originated by the heavy upper structure would induce large friction force and compression force between interfaces of column foot and stone base. This study focused on the mechanical behaviors of column foot joint with consideration of the influence of vertical load. Mechanism of column rocking and stress state of column foot has been explored by theoretical analysis. A nonlinear finite element model of column foot joint has been built and verified using the full-scale test. The verified model is then used to investigate the mechanical behaviors of the joint subjected to cyclic loading with different static vertical loads. Column rocking mechanism and stress distributions of column foot were studied in detail, showing good agreement with the theoretical analysis. Mechanical behaviors of column foot joint and the effects of the vertical load on the seismic behavior of column foot were studied. Result showed that compression stress, restoring moment and stiffness increased with the increase of vertical load. An appropriate vertical load originated by the heavy upper structure would produce certain restoring moment and reset the rocking columns, ensuring the stability of the whole frame.