• Smart Structures and Systems
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• 제4권2호
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• pp.153-169
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• 2008

The use of pre-tensioned shape memory alloy (SMA) wires to retrofit historic masonry structures is investigated. A small wall, serving as a prototype masonry specimen, is constructed to undergo a series of shaking-table tests. It is first studied in its original state, and its dynamic characteristics (in terms of modal frequencies) are extracted from the recorded signals. The results are then compared with those obtained when an increasing number of couples of pre-stressed SMA wires are introduced in the specimen to link the bricks together. A three-dimensional finite element model of the specimen is developed and calibrated according to the modal parameters identified from each experimental test (with and without SMA wires). The calibration process is conducted by enhancing the masonry mechanical behaviour. The results and the effectiveness of the approach are presented.

• 대한기계학회논문집A
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• 제25권2호
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• pp.289-295
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• 2001

The aim of this study is to investigate the ductile fracture behaviour under pure Mode II loading using A533B pressure vessel steel. Single punch shear(SPS) test was performed to obtain the J-R curve under pure Mode II loading which was compared with that of the Model I loading. Simulation using Rousellier Ductile Damage Theory(RDDT) was carried out with 4-node quadrilateral element(L(sub)c=0.25mm). For the crack advance, the failed element removal technique was adopted with a $\beta$ criterion. Through the $\beta$ value tuning-up procedures, $\beta$(sub)crit(sup)II was determined as 1.5 in contrast with $\beta$(sub)crit(sup)I=5.5. In conclusion, it was found that the J-R curve under Mode II loading was located at lower part than that under Mode I loading obtained from the previous study and that the $\beta$ values strongly depended on the loading type. In addition, the predicted result using RDDT showed a good agreement with the SPS experimental one under pure Mode II loading.

• Steel and Composite Structures
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• 제32권6호
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• pp.743-752
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• 2019

Steel and concrete composite structures are commonly applied in multi-story buildings as they maximise the material strength through composite action. Despite the popularity of employing a trapezoidal deck slab, limited experimental data are available under elevated temperatures. The behaviour of the headed shear stud embedded in a transverse trapezoidal deck and solid slab was investigated at both ambient and fire conditions. Twelve push-out tests were conducted according to the ISO 834 standard fire utilising a customised electric furnace. A stud shearing failure was observed in the solid slab specimen, whereas the failure mode was changed from a concrete-dominated failure to the stud shearing in the transverse deck specimen with an increase in temperature. Comparisons between the experimental observations and design requirements are presented. The Eurocode design guidance on the transverse deck slab gives a highly conservative estimate for shear resistance. A new design formula was proposed to determine the capacity of the shear connection regardless of the slab type when the stud shearing occurs at high temperatures.

• 한국구조물진단유지관리공학회 논문집
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• 제21권3호
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• pp.121-129
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• 2017

본 논문에서는 국내 비내진상세 조적채움벽 RC 골조의 동적거동 및 손상모드를 파악하기 위하여 실규모 크기의 비내진상세 RC 골조와 조적채움벽 RC 골조를 대상으로 진동대 실험을 실시하여 응답 및 거동 특성을 비교 평가하였다. 진동대 실험 결과, 순수 RC 골조는 기둥상하부 휨균열 및 접합부 전단균열이 심화되어 최종 파괴되었다. 조적채움벽 RC 골조의 경우 골조의 손상은 비교적 작았으며 조적벽체의 중앙부의 슬라이딩 균열 및 대각 전단 균열 손상이 크게 발생하였다. 조적채움벽 RC 골조는 순수 RC 골조에 비하여 초기상태의 공진주기가 짧아졌으며 최종 가진시에서 최대변위응답은 약 62% 감소하였다. 본 연구에서 적용한 조적채움벽은 비내진 상세를 가지는 RC 골조의 강성을 약 1.6배, 최대 강도를 약 2.2배 증가시키는 데 기여하는 것으로 분석되었다.

• Steel and Composite Structures
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• 제32권6호
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• pp.717-729
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• 2019

A horizontal cyclic test was carried out to study the seismic performance of lightweight aggregate concrete filled steel tube (LACFST). The constitutive and hysteretic model of core lightweight aggregate concrete (LAC) was proposed for finite element simulation. The stress and strain changes of the steel tube and concrete filled inside were measured in the experiment, and the failure mode, hysteresis curve, skeleton curve, and strain curve of the test specimens were obtained. The influence of axial compression ratio, diameter-thickness ratio and material strength were analysed based on finite element model. The results show that the hysteresis curve of LACFST indicated favourable ductility, energy dissipation, and seismic performance. The LACFST failed when the concrete in the bottom first crushed and the steel tube then bulged, thus axial force imposed by prestressing was proved to be feasible. The proposed constitutive model and hysteretic model of LAC under the constraint of its steel tube was reliable. The bearing capacity and ductility of the specimen increase significantly with increasing thickness of the steel tube. The bearing capacity of the member improves while the ductility and energy dissipation performance slightly decreased with the increasing strength of the steel and concrete.

• Steel and Composite Structures
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• 제34권6호
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• pp.877-889
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• 2020

This work features the outcomes of an empirical investigation into the characteristics of steel reinforced grout (SRG) composite - concrete interfaces. The parameters varied were loading rate, densities of steel fibres and types of load displacement responses or measurements (slip and machine grips). The following observations and results were derived from standard single-lap shear tests. Interfacial debonding of SRG - concrete joints is a function of both fracture of matrix along the bond interface and slippage of fibre. A change in the loading rate results in a variation in peak load (P_max) and the correlative stress (σ_max), slip and machine grips readings at measured peak load. Further analysis of load responses revealed that the behaviour of load responses is shaped by loading rate, fibre density as well as load response measurement variable. Notably, the out-of-plane displacement at peak load increased with increments in load rates and were independent of specimen fibre densities.

• Steel and Composite Structures
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• 제33권1호
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• pp.19-36
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• 2019

Cyclic behaviour of composite (steel-concrete) plate shear walls (CPSW) with variable column flexural stiffness is experimentally and numerically investigated. The investigation included design, fabrication and testing of three pairs of one-bay one-storey CPSW specimens. The reference specimen pair was designed in way that its column flexural stiffness corresponds to the value required by the design codes, while within the other two specimen pairs column flexural stiffness was reduced by 18% and 36%, respectively. Specimens were subjected to quasi-static cyclic tests. Obtained results indicate that column flexural stiffness reduction in CPSW does not have negative impact on the overall behaviour allowing for satisfactory performance for up to 4% storey drift ratio while also enabling inelastic buckling of the infill steel plate. Additionally, in comparison to similar steel plate shear wall (SPSW) specimens, column "pull-in" deformations are less pronounced within CPSW specimens. Therefore, the results indicate that prescribed minimal column flexural stiffness value used for CPSW might be conservative, and can additionally be reduced when compared to the prescribed value for SPSWs. Furthermore, finite element (FE) pushover simulations were conducted using shell and solid elements. Such FE models can adequately simulate cyclic behaviour of CPSW and as such could be further used for numerical parametric analyses. It is necessary to mention that the implemented pushover FE models were not able to adequately reproduce column "pull-in" deformation and that further development of FE simulations is required where cyclic loading of the shear walls needs to be simulated.

• 한국방재학회 논문집
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• 제3권1호
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• pp.123-131
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• 2003

파형강관을 삽입하여 보강된 중공원형단면의 역학적 거동을 연구하기 위하여 직경 50cm, 길이 340cm의 시험체를 제작하였고, 3점 휨시험을 수행하였다. 하중재하는 파괴 또는 최대한변형이 발생할 때까지 느리게 증가시켰다. 시험하는 동안에 시험체 중앙의 휨방향 변위와 인장측과 압축측의 종방향 변위를 측정하였다. 측정데이타를 분석한 결과를 파형강관이 삽입되지 않은 등가단면에 대한 해석결과와 비교하였다. 비교결과, 중공 철근콘크리트 부재의 휨강성과 연성이 파형강관을 내부에 삽입함으로써 크게 향상시킬 수 있는 것으로 나타났다.

• Earthquakes and Structures
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• 제13권5호
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• pp.473-484
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• 2017

The objective of this paper is to report on a study of the use of unstiffened thin steel plate shear walls (SPSWs) for the seismic performance improvement of reinforced concrete frames with deficient lateral rigidity. The behaviour of reinforced concrete frames during seismic activities was rehabilitated with an alternative and occupant-friendly retrofitting scheme. The study involved tests of eight 1/3 scale, one bay, two storey test specimens under cyclic quasi-static lateral loadings. The first specimen, tested in previous test program, was a reference specimen, and in seven other specimens, steel infill plates were used to replace the conventional infill brick or the concrete panels. The identification of the load-deformation characteristics, the determination of the level of improvement in the overall strength, and the elastic post-buckling stiffness were the main issues investigated during the quasi-static test program. With the introduction of the SPSWs, it was observed that the strength, stiffness and energy absorption capacities were significantly improved. It was also observed that the experimental hysteresis curves were stable, and the composite systems showed excellent energy dissipation capacities due to the formation of a diagonal tension field action along with a diagonal compression buckling of the infill plates.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1993년도 특별강연 및 춘계학술발표 개요집
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• pp.120-124
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• 1993

The Charpy V impact test on subsize was performed on narrow laser welds of low carbon steel sheets, joined by using a continuous wave 3kW CO$_2$ laser. Under certain conditions, a bimodal fracture behaviour has been experienced in Charpy V impact test of narrow laser beam welds. Deviation of the fracture path from the fusion zone into the base metal was dominated at high test temperature. It can be seen that the deviation always occurred after ductile initiation. If the deviation occurs on a small testing specimen, the same trend would happen on the actual laser welded structure. Fracture will then propagate through the base material even if the weld metal has low toughness.