• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.193-196
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• 2006

Unlike external bonded plate or carbon fiber, the external unbonded strengthening has some advantages in speed and simplicity of installation. It is not required surface preparations and not affected by environmental conditions. A set of six laboratory tests on RC beams strengthened using the technique are reported, results compared with non-strengthened specimens. The main test parameters are the cross-sectional area of the high-tension bar and the distance of stirrups. Test result show that the beams reinforced are superior to reference specimens, especially for the strength and deformation capacity. Also, it is shown that good efficiencies can be achived in shear strength of the beam.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.673-676
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• 2006

Steel FibreReinforced Shotcrete(SFRS) is one of the main tunnel support along with the rock bolt during the excavation and after the completion of the tunnel. In the standard qualification of the SFRS defined by Korea Highway Corporation, 28 day core specimen has to meet the compressive strength of 19.6 MPa and over 90 % fibre contents. Furthermore, for the 28 days brick shaped specimen made by shooting, flexural strength should be over 4.4 MPa and flexural toughness ratio which can be calculated from flexural toughness factor has to meet more than 68% of flexural strength. In shotcrete, accelerating agent is added for the rapid strength development. Silicate and aluminate type agents are known to develop shotcrete strength rapidly, however, has such problem to degrade the middle and long term strength. Hence, using poly carboxylic super plasticizer, it was aimed to enhance the quality of the shotcrete with the lower water-cement ratio and the same level of workability. The present paper shows the part of the field test result and its analysis.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.257-260
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• 2006

Coupled shear walls consist of two or more in-plane walls inter-connected with coupling beams. In order to effectively resist seismic loads, coupling beams must be sufficiently stiff, strong and posses a stable load-deflection hysteretic response. Much of requirements to the civil and building structures have recently been changed in accordance with the social and economic progress. Ductility of high performance fiber reinforced cementitious composites(HPFRCCs), which exhibit strain hardening and multiple crackling characteristics under the uniaxial tensile stress is drastically improved. This paper provides background for design guidelines that include a design model to calculate the shear strength of pseudo strain hardening cementitious composite steel coupling beam.

• Steel and Composite Structures
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• 제19권2호
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• pp.327-348
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• 2015

A numerical procedure is presented that provides ultimate curvature and moment domains for composite rectangular and circular cross-sections of reinforced concrete columns with or without an embedded steel section subjected to combined axial loading and biaxial bending. The stress resultants for the concrete and reinforcement bars are calculated using fiber analysis and the stress resultants for the encased structural steel are evaluated using an exact integration of the stress-strain curve over the area of the steel section. A dimensionless formula is proposed that can be used for any section with similar normalized geometric and mechanical parameters. The contribution of each material to the bearing capacity of a section (resistance load and moments) is calculated separately so that the influence of each geometric or mechanical parameter on the bearing capacity can be investigated separately.

• Computers and Concrete
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• 제30권3호
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• pp.209-224
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• 2022

In this paper, the artificial neural network (ANN) is employed to predict the flexural behavior of reinforced concrete (RC) beams retrofitted with carbon fiber/epoxy composites modified by carbon nanotubes (CNTs). Multiple techniques are used to improve the accuracy of the ANN prediction, as the data represents a multivalued function. These techniques include static ANN modeling, ANN modeling with load history, and ANN modeling with double load history. The developed ANN models are used to predict the load-displacement profiles of beams retrofitted with either CFRP or CNTs modified CFRP, flexural capacity, and maximum displacement of the beams. The results demonstrate that the ANN is able to predict the flexural behavior of the retrofitted RC beams as well as the effect of each parameter including the type of the used epoxy and the presence of the CNTs.

• Structural Engineering and Mechanics
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• 제83권1호
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• pp.109-121
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• 2022

Twelve push-out test specimens were conducted with various parameters to study the static and fatigue performance of a new through-bolt shear connector transferring the shear forces of interface between prefabricated hybrid fiber reinforced concrete (HFRC) slabs and steel girders. It was found that the fibers could improve the fatigue life, capacity and initial stiffness of through-bolt shear connector. While the bolt-hole clearance reduced, the initial stiffness, capacity and slippage of through-bolt shear connector increased. After the steel-concrete interface properties were improved, the initial stiffness increased, and the capacity and slippage reduced. Base on the test results, the equation of the load-slip curve and capacity of through-bolt shear connector with prefabricated HFRC slab were obtained by the regression of test results, and the allowable range of shear force under fatigue load was recommended, which could provide the reference in the design of through-bolt shear connector with prefabricated HFRC slabs.

• Structural Engineering and Mechanics
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• 제81권4호
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• pp.513-522
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• 2022

Steel-concrete composite segments replacing the conventional reinforced concrete segments can provide the rectangular shield tunnel superiorities on bearing capacity, ductility and economy. A simplified model with high-efficiency on computation is proposed for investigating the nonlinear response of the rectangular tunnel lining composed of composite segments. The simulation model is developed by an assembly of nonlinear fiber beam elements and spring elements to express the transfer mechanism of forces through components of composite segments, and radial joints. The simulation is conducted with the considerations of material nonlinearity and geometric nonlinearity associated with the whole loading process. The validity of the model is evaluated through comparison of the proposed nonlinear simulation with results obtained from the full-scale test of the segmental tunnel lining. Furthermore, a parameter study is conducted by means of the simplified model. The results show that the stiffness of the radial joint at haunch of the ling and the thickness of inner steel plate of segments have remarkable influence on the behaviour of the lining.

• Computers and Concrete
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• 제30권2호
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• pp.113-126
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• 2022

Reinforced concrete bearing walls (RCBWs) are one of the most applicable structural systems. Therefore, vulnerability analysis and rehabilitation of the RCBW system are of great importance. In the present study, in order to the more precise investigation of the performance of this structural resistant system, pushover and nonlinear time history analyses based on several assumptions drawing upon experimental research were performed on several models with different stories. To validate the nonlinear analysis method, the analytical and experimental results are compared. Vulnerability evaluation was carried out on two seismic hazard levels and three performance levels. Eventually, the need for seismic rehabilitation with the basic safety objective (BSO) was investigated. The obtained results showed that the studied structures satisfied the BSO of the seismic rehabilitation guidelines. Consequently, according to the results of analyses and the desired performance, this structural system, despite its high structural weight and rigid connections and low flexibility, has integrated performance, and it can be a good option for earthquake-resistant constructions.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 가을 학술논문 발표대회
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• pp.65-66
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• 2022

In this study, the setting characteristics of the high range water reducing agent to minimize the retardation of UHPC were confirmed to minimize the setting time in the hardening of UHPC. As a result of the study, there was a slight change depending on the difference in the type of Superplasticizer, K > P > D = S > E in the order of condensation promotion, and E > S = D = K > P on the 28th day.

• 한국재료학회지
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• 제34권2호
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• pp.72-78
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• 2024

The lightweight and high strength characteristics of aluminum alloy materials make them have promising prospects in the field of construction engineering. This paper primarily focuses on aluminum alloy materials. Aluminum alloy was combined with concrete, wood and carbon fiber reinforced plastic (CFRP) cloth to create a composite column. The axial compression test was then conducted to understand the mechanical properties of different composite structures. It was found that the pure aluminum tube exhibited poor performance in the axial compression test, with an ultimate load of only 302.56 kN. However, the performance of the various composite columns showed varying degrees of improvement. With the increase of the load, the displacement and strain of each specimen rapidly increased, and after reaching the ultimate load, both load and strain gradually decreased. In comparison, the aluminum alloy-concrete composite column performed better than the aluminum alloy-wood composite column, while the aluminum alloy-wood-CFRP cloth composite column demonstrated superior performance. These results highlight excellent performance potential for aluminum alloy-wood-CFRP composite columns in practical applications.