• Earthquakes and Structures
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• 제7권4호
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• pp.463-484
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• 2014

Solid piers with a rounded rectangular cross-section are widely used in railway bridges for high-speed trains in China. Compared to highway bridge piers, these railway bridge piers have a larger crosssection and less steel reinforcement. Existing material models cannot accurately predict the seismic behavior of this kind of railway bridge piers. This is because only a few parameters, such as axial load, longitudinal and transverse reinforcement, are taken into account. To enable a better understanding of the seismic behavior of this type of bridge pier, a simultaneous influence of the various parameters, i.e. ratio of height to thickness, axial load to concrete compressive strength ratio and longitudinal to transverse reinforcements, on the failure characteristics, hysteresis, skeleton curves, and displacement ductility were investigated. In total, nine model piers were tested under cyclic loading. The hysteretic response obtained from the experiments is compared with that obtained from numerical studies using existing material models. The experimental data shows that the hysteresis curves have significantly pinched characteristics that are associated with small longitudinal reinforcement ratios. The displacement ductility reduces with an increase in ratio of axial load to concrete compressive strength and longitudinal reinforcement ratio. The experimental results are largely in agreement with the numerical results obtained using Chang-Mander concrete model.

• Geomechanics and Engineering
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• 제12권6호
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• pp.919-933
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• 2017

A series of Brazilian tests under diameter compression for disc specimens was carried out to investigate the strength and failure behavior by using acoustic emission (AE) and photography monitoring technique. On the basis of experimental results, load-displacement curves, AE counts, real-time crack evolution process, failure modes and strength property of granite specimens containing two pre-existing holes were analyzed in detail. Two typical types of load-displacement curves are identified, i.e., sudden instability (type I) and progressive failure (type II). In accordance with the two types of load-displacement curves, the AE events also have different responses. The present experiments on disc specimens containing two pre-existing holes under Brazilian test reveal four distinct failure modes, including diametrical splitting failure mode (mode I), one crack coalescence failure mode (mode II), two crack coalescences failure mode (mode III) and no crack coalescence failure mode (mode IV). Compared with intact granite specimen, the disc specimen containing two holes fails with lower strength, which is closely related to the bridge angle. The failure strength of pre-holed specimen first decreases and then increases with the bridge angle. Finally, a preliminary interpretation was proposed to explain the strength evolution law of granite specimen containing two holes based on the microscopic observation of fracture plane.

• Journal of the Korean Wood Science and Technology
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• 제51권6호
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• pp.526-541
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• 2023

Wooden structures are widely used, particularly in earthquake zones, owing to their light weight, ease of application, and resistance to the external environment. In this study, we aimed to improve the mechanical properties of laminated timber beams using novel hybrid systems [carbon-fiber-reinforced polymer (CFRP) and wire rope]. Within the scope of this study, it is expected that using wood, which is an environmentally friendly and sustainable building element, will be more economical and safe than the reinforced concrete and steel elements currently used to pass through wide openings. The structural behavior of the hybrid-reinforced laminated timber beams was determined under the loading system. The experimental findings showed that the highest increase in the values of laminated beams reinforced with steel ropes was obtained with the 2N reinforcement, with a maximum load of 38 kN and a displacement of 137 mm. Thus, a load increase of 168% and displacement increase of 275% compared with the reference sample were obtained. Compared with the reference sample, a load increase of 92% and a displacement increase of 14% were obtained. Carbon fabrics placed between the layers with fiber-reinforced polymer (FRP) prevented crack development and provided significant interlayer connections. Consequently, the fabrics placed between the laminated wooden beams with the innovative reinforcement system will not disrupt the aesthetics or reduce the effect of earthquake forces, and significant reductions can be achieved in these sections.

• 한국구조물진단유지관리공학회 논문집
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• 제21권3호
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• pp.60-68
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• 2017

교량은 사회간접시설물의 핵심이 되는 도로의 주요 시설물이므로 공용기간 동안 안정성과 사용성이 확보될 수 있도록 건설되며, 교량의 안전성 확보를 위하여 현재 상태에서 건전성을 평가하는 것은 유지관리 업무에서 중요한 과제이다. 일반적으로 교량의 내하력 평가를 위해 차량재하시험을 통하여 횡분배율을 측정함으로써 교량의 중첩거동 및 대칭거동을 확인할 수 있다. 그러나 공용중인 교량의 횡분배율을 측정하기 위하여 정적재하시험을 수행하고 있으며 교통통제의 어려움이 있다. 따라서 본 연구에서는 동적재하시험 및 상시진동시험에서 측정된 교량의 변위응답 데이터를 경험적 모드분해기법을 이용하여 정적 성분의 변위를 추출하였다. 추출된 정적 성분의 변위를 이용하여 횡분배율을 추정하였으며, 정적재하시험에서 측정된 횡분배율과 비교하였다.

• Structural Engineering and Mechanics
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• 제52권6호
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• pp.1135-1156
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• 2014

The ratcheting effect greatly challenges the design of piping components. With the assistance of the quasi-three point bending apparatus, ratcheting and the ratcheting boundary of pressurized straight Z2CND18.12N stainless steel pipe under bending loading and vertical displacement control were studied experimentally. The characteristics of progressive inelastic deformation in axial and hoop directions of the Z2CND18.12N stainless steel pipes were investigated. The experiment results show that the ratcheting strain occurs mainly in the hoop direction while there is less ratcheting strain in the axial direction. The characteristics of the bending ratcheting behavior of the pressure pipes were derived and compared under load control and displacement control, respectively. The results show that the cyclic bending loading and the internal pressure affect the ratcheting behavior of the pressurized straight pipe significantly under load control. In the meantime, the ratcheting characteristics are also highly associated with the cyclic displacement and the internal pressure under displacement control. All these factors affect not only the saturation of the ratcheting strain but the ratcheting strain rate. A series of multi-step bending ratcheting experiments were conducted under both control modes. It was found that the hardening effect of Z2CND18.12N stainless steel pipe under previous cyclic loadings no matter with high or low displacement amplitudes is significant, and the prior loading histories greatly retard the ratcheting strain and its rate under subsequent loadings. Finally, the ratcheting boundaries of the pressurized straight Z2CND18.12N stainless steel pipe were determined and compared based on KTA/ASME, RCC-MR and the experimental results.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.301-306
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• 2008

The present seismic analysis of Road-Bridge Design Standard is on a basis of load-vased analysis which lets structures have the strength over load. In this study, the capacity spectrum method, a kind of displacement based method, which is evaluated by displacement of structure, is presented as an alternative to the analysis method based on load. Seismic capacity is performed about the existing reinforced concrete pier which has already secured seismic design by capacity spectrum method. As a result, capacity spectrum method could realistically evaluate the non-elastic behavior of structures easilly and quickly and the displacement of structures for variable ground motion level. And it could efficiently apply to an evaluation of seismic capacity about the existing structures and a verification of design for capacity target of the structure. We propose the seisemic performance method by using the Finite Element Analysis Program.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 춘계학술대회 논문집
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• pp.148-151
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• 2004

Mechanical properties such as Young's modulus and hardness of thin film in coated steel are difficult to determine by nano-indentation from the conventional analysis using the load-displacement curve. Therefore, an analysis of the nano-indentation loading curve was used to determine the Young's modulus, hardness and strain hardening exponent. A new method is recently being developed for plasticity properties of materials from nano-indentation. Elastic modulus of the thin films shows relatively small influence whereas yield strength and strain hardening are found to have significant effect on measured data. The load-displacement behavior of material tested with a Berkovich indenter and nano-indentation continuous stiffness method is used to measure the modulus and hardness through thin films.

• 한국지반신소재학회논문집
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• 제15권4호
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• pp.89-96
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• 2016

인천 ${\bigcirc}{\bigcirc}$지역의 연약지반에 시공된 변단면 연약지반보강기초(Variable cross-section soft ground reinforced foundation)의 연직압축거동을 분석하였다. 변단면 연약지반보강기초는 원지반과 고화재를 혼합교반하여 형성되는 고형체의 높은 강성과 강도를 이용하여 상부구조물로부터 유발되는 연약하중을 효과적으로 저항하기 위하여 시공된다. 변단면 연약지반보강기초는 군말뚝 형식으로 시공이 되는데, 정확한 연직거동을 알기 위하여 1개소의 기초에 대한 연직재하시험을 수행하였다. 변단면 연약지반보강기초의 거동을 일반적인 깊은 기초의 거동과 비교하기 위하여 유사한 천층지반조건에 시공된 PHC 파일의 재하시험 결과와 비교하여 재하하중에 따른 침하량 및 하중전이 거동특성을 분석하였다. 연직재하시험결과를 비교분석하였다. 변단면 연약지반보강기초는 제한된 범위의 연직하중에 대하여 천층에서도 효율적으로 저항하는 것으로 분석되었다.

• 한국공작기계학회논문집
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• 제13권6호
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• pp.23-28
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• 2004

Impact behavior of polycarbonate in various defect state was investigated using an instrumented impact tester. A method of analyzing raw impact data was developed and successfully demonshsted the impact behavior in terms of load-displacement and energy-displacement curves. This technique was shown to be capable of separating defect no-defect initiated fractures as well as their propagation behaviors.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.262-267
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• 2002

Impact behavior of polycarbonate in various defect state was investigated using an instrumented impact fester. A mettled of analyzing raw impact data was developed and successfully demonstrated the impact behavior in terms of load-displacement and energy-displacement curves. This technique was shown to be capable of separating defect, no-defect initiated fractures as well as their propagation behaviors.