• 한국전산구조공학회논문집
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• 제30권1호
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• pp.55-61
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• 2017

최근 콘크리트 궤도 슬래브 하면과 교량 바닥판 사이에 저마찰 슬라이드층을 형성하는 궤도 시스템인 슬라이딩 궤도와 관련된 연구가 활발히 진행되고 있다. 본 연구에서는 슬라이딩 궤도에서 열차 주행에 따른 횡방향 하중을 저항하기 위해 설치되는 횡방향 지지 콘크리트 블록의 전단 내하력에 대한 연구를 수행하였다. 횡방향 지지 콘크리트 블록의 전단 내하력 산정을 위해 타설경계면에서의 콘크리트 마찰 및 철근의 다월 거동을 고려한 산정 기법을 개발하다. 제안된 산정 기법은 기존의 실험에서 측정된 전단 내하력을 13~23% 정도 보수적으로 예측하는 것으로 나타났다. 이는 균열면 골재 맞물림 효과를 무시한 것에 따른 것으로, 현장에서의 타설경계면 상태가 불확실한 것을 고려할 때 횡방향 지지 콘크리트 블록에 대한 안전측 설계를 위해 제안된 산정 기법이 합리적인 것으로 판단된다. 제안된 전단 내하력 산정 기법을 토대로 횡방향 지지 콘크리트 블록에 대한 설계 방안을 마련하였다.

• Computers and Concrete
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• 제20권6호
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• pp.663-670
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• 2017

The post-tensioned (PT) flat plate slab system is commonly used in practice, and this simple and fast construction method is also considered to be a very efficient method because it can provide excellent deflection and crack control performance under a service load condition and consequently can be advantageous when applying to long-span structures. However, a detailed design guideline for evaluating the lateral behavior of the PT flat plate slab system is not available in current design codes. Thus, typical design methods used for conventional reinforced concrete (RC) flat plate slab structures have inevitably been adopted in practice for the lateral load design of PT flat plate structures. In the authors' previous studies, the unified equivalent frame method (UEFM) was proposed, which considers the combined effect of gravity and lateral loads for the lateral behavior analysis of RC flat plate slab structures. The aim of this study is to extend the concept of the UEFM to the lateral analysis of PT flat plate slab structures. In addition, the stiffness reduction factors of torsional members on interior and exterior equivalent frames were newly introduced considering the effect of post-tensioning. Test results of various PT flat plate slab-column connection specimens were collected from literature, and compared to the analysis results estimated by the extended UEFM.

• 한국철도학회논문집
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• 제3권4호
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• pp.194-202
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• 2000

Fatigue behavior of shear joints between the combined reinforced concrete(RC) and the reinforced steel fiber concrete(SFRC) specimens has been experimentally investigated. Experimental parameters used are the amount of steel fiber and the type of shear joint. Six specimens have been tested under static load, and eight specimens have been subjected to the fatigue load in a range of 50 % and 5 % of the ultimate static load. The purpose of this research is to propose an empirical formula for fatigue shear behavior of the combined RC and SFRC structures on the basis of experimental result. It can be observed from experimental results that addition of steel fibers to concrete specimen increases the static ultimate load by approximately 25 %, enhances the fatigue behavior, and also reduces vertical and lateral displacements at the shear joint for a given load cycle after the occurrence of first crack.

• Tribology and Lubricants
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• 제13권4호
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• pp.18-25
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• 1997

The various deformation and fracture behaviors under light loads in soda-lime glass under sliding Vickers indentation have been studied. In soda-lime glass, deformation and fracture behaviors can be classified into four different patterns by applied load. At very light load (<0.1N), plastic deformation only occurred. At low loads (0.1~0.8N), median crack, appear. At intermediate loads (0.8~3.0N), median and lateral cracking occurred leading to a large chipping. At high loads (3.0~6.0N), a crushed zone was observed with median crack. The friction experiment finds that the increasing in the friction coefficients coincides with the onset of crushing in soda-lime glass.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.53-56
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• 2005

This paper investigates the effect of ductile deformation behavior of high performance hybrid fiber-reinforced cement composites (HPHFRCCs) on the shear behavior of coupling beams to lateral load reversals. The matrix ductility and the reinforcement layout were the main variables of the tests. Three short coupling beams with two different reinforcement arrangements and matrixes were tested. They were subjected to cyclic loading by a suitable experimental setup. All specimens were characterized by a shear span-depth ratio of 1.0. The reinforcement layouts consisted of a classical scheme and diagonal scheme without confining ties. The effects of matrix ductility on deflections, strains, crack widths, crack patterns, failure modes, and ultimate shear load of coupling beams have been examined. The combination of a ductile cementitious matrix and steel reinforcement is found to result in improved energy dissipation capacity, simplification of reinforcement details, and damage-tolerant inelastic deformation behavior. Test results showed that the HPFRCC coupling beams behaved better than normal reinforced concrete control beams. These results were produced by HPHFRCC's tensile deformation capacity, damage tolerance and tensile strength.

• Structural Engineering and Mechanics
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• 제5권6호
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• pp.743-754
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• 1997

A three-dimensional constitutive modeling for reinforced concrete is presented for finite element nonlinear analysis of reinforced concrete. The targets of interest to the authors are columns confined by lateral steel hoops, RC thin shells subjected to combined in-plane and out-of-plane actions and massive structures of three-dimensional (3D) extent in shear. The elasto-plastic and continuum fracture law is applied to pre-cracked solid concrete. For post cracking formulation, fixed multi-directional smeared crack model is adopted for RC domains of 3D geometry subjected to monotonic and reversed cyclic actions. The authors propose a new scheme of decomposing stress strain fields into sub-planes on which 2D constitutive laws can be applied. The proposed model for 3D reinforced concrete is experimentally verified in both member and structural levels under cyclic actions.

• International Journal of Concrete Structures and Materials
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• 제9권3호
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• pp.307-321
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• 2015

The primary objective of this study is to investigate the feasibility of an innovative surface-mount sensor, made of a piezoelectric disc (PZT sensor), as a consistent source for surface wave velocity and transmission measurements in concrete structures. To this end, one concrete slab with lateral dimensions of 1500 by 1500 mm and a thickness of 200 mm was prepared in the laboratory. The concrete slab had a notch-type, surface-breaking crack at its center, with depths increasing from 0 to 100 mm at stepwise intervals of 10 mm. A PZT sensor was attached to the concrete surface and used to generate incident surface waves for surface wave measurements. Two accelerometers were used to measure the surface waves. Signals generated by the PZT sensors show a broad bandwidth with a center frequency around 40 kHz, and very good signal consistency in the frequency range from 0 to 100 kHz. Furthermore, repeatability of the surface wave velocity and transmission measurements is significantly improved compared to that obtained using manual impact sources. In addition, the PZT sensors are demonstrated to be effective for monitoring an actual surface-breaking crack in a concrete beam specimen subjected to various external loadings (compressive and flexural loading with stepwise increases). The findings in this study demonstrate that the surface mount sensor has great potential as a consistent source for surface wave velocity and transmission measurements for automated health monitoring of concrete structures.

• 대한토목학회논문집
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• 제29권4A호
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• pp.299-305
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• 2009

본 연구에서는 철도교의 세로보 절취부에서의 피로균열 발생 원인을 연구하기 위하여 실제로 피로균열이 발생한 철도교를 연구대상으로 실물크기의 가로보-세로보 바닥틀 모형을 제작하고 실내실험을 수행하였다. 연구 결과 세로보 상부절취부에서의 피로균열 발생원인은 세로보의 단부에서 발생하는 부모멘트에 의한 상부절취부 복부판의 면내응력의 반복적 작용 결과이고, 하부절취부에서의 피로균열 발생 원인은 세로보 단부의 고정단에 대한 하부절취부 복부판의 상대적 면외변형에 의해 발생하는 면외응력의 반복적 작용 결과라는 결론을 얻었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.460-467
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• 1997

Compared to normal-strength concrete, high-strength concrete has the lower lateral expansion capacity caused by the higher elastic modulus and the lower internal crack characteristic. Therefore, the effect of the lateral confining action of hoops appears slowly and also in inefficient Nevertheless. it has been reported that the strength and deformation capacity of high-strength concrete is improved by well-distributed hoops. Due to that argument, this investigation has been compared and analyzed by the experimental works on the deformation capacity and the confinement mechanism of high-strength concrete shear wall of the high-rise building reinforced by rectangular steel tubes and rectangular hoops at both edges of the shear wall.

• Structural Engineering and Mechanics
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• 제78권5호
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• pp.545-556
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• 2021

The present experimental study evaluated the seismic performance of six engineered cementitious composite (ECC) columns strengthened with carbon fiber reinforced polymer (CFRP) laminates under cyclic lateral loading. The ECC columns damaged and crushed in the first stage of cyclic tests were repaired using the ECC with a certain polyvinyl alcohol (PVA) fiber and strengthened with flexural and sheer CFRP laminates and then re-assessed under the cyclic loading. The effects of some variables were examined on lateral displacement, energy absorption and dissipation, failure modes, crack patterns, load bearing capacity and plasticity, and the obtained results were compared with those of the first stage of cyclic tests. The results showed that retrofitting the ECC columns can improve their performance, plasticity and load-bearing threshold, delayed the concrete failure, changed the failure modes and increased the energy absorbed by the strengthened columns element by over 50%.