• 한국공간구조학회논문집
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• 제5권2호
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• pp.65-71
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• 2005

최근 노후화된 철근콘크리트 구조물에 대한 FRP를 이용한 보강공법의 적용이 증가하고 있다. 하지만 휨 보강에 대해서는 연구로 인해 정량적인 평가로 인해 효율적인 설계가 가능하지만, 전단보강의 경우에는 파괴메카니즘을 완전히 규명하지 못하는 상태이다. 본 연구에서는 전단보강근이 있는 철근콘크리트보에 매립형 CFRP를 전단보강하여 보강효과를 파악하고자 실험을 수행한 후, 실험결과를 토대로 분석 및 고찰을 통해 정량적인 보강효과를 도출하고자 한다. 시험체 제작시 실험변수로는 전단보강근의 간격과 보강방향으로 하여 시험체를 10개 제작하여 실험을 수행하였다. 실험결과, 전단보강근 간격과 보강방향에 따라 CFRP의 보강효과는 다소 차이를 보였다.

• Computers and Concrete
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• 제7권4호
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• pp.285-301
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• 2010

In this work we first review the statistical data on large fires in urban areas, presenting a detailed list of causes of fires, the type of damage to concrete and reinforced concrete structures. We also present the modern experimental approach for studying the fire-resistance of different structural components, along with the role of numerical modeling to provide more detailed information on quantifying the temperature and heat flux fields. In the last part of this work we provide the refined models for assessment of fire-induced damage in structures built of concrete and/or reinforced-concrete. We show that the refined models of this kind are needed to provide a more thorough explanation of damage and to complete the damage assessment and post-fire evaluations.

• 터널과지하공간
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• 제19권5호
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• pp.397-406
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• 2009

최근에는 구조적 노후화 및 기능적 요건을 만족하지 못하여 해체되는 산업구조물의 수요가 증가하고 있으며, 해체과정에서 발생되는 시간적, 공간적 환경위해요소를 최소화하기 위해 발파해체공법의 적용이 증가하고 있다. 본 시공 사례는 구조적 노후화와 기능적 요건을 충족하지 못하는 대단면 철근콘크리트 특수구조물인 Crusher & Screen 구조물의 발파해체를 기술하였다. 대단면 철근콘크리트 부재에 대한 다양한 사전취약화 및 발파패턴을 적용하였으며 발파진동 및 충격진동을 감소시키기 위해 동일한 기둥 내에서의 발파시차 및 발파구역간의 발파시차를 설정하였다. 대단면 철근콘크리트 특수구조물의 해체에 발파해체공법을 적용함으로써 주변 시설물에 대한 피해없이 안전하고 효율적으로 해체가 완료되었다.

• Earthquakes and Structures
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• 제13권3호
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• pp.241-253
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• 2017

In this paper, dynamic response of the horizontal nanofiber reinforced polymer (NFRP) strengthened concrete beam subjected to seismic ground excitation is investigated. The concrete beam is modeled using hyperbolic shear deformation beam theory (HSDBT) and the mathematical formulation is applied to determine the governing equations of the structure. Distribution type and agglomeration effects of carbon nanofibers are considered by Mori-Tanaka model. Using the nonlinear strain-displacement relations, stress-strain relations and Hamilton's principle (virtual work method), the governing equations are derived. To obtain the dynamic response of the structure, harmonic differential quadrature method (HDQM) along with Newmark method is applied. The aim of this study is to investigate the effect of NFRP layer, geometrical parameters of beam, volume fraction and agglomeration of nanofibers and boundary conditions on the dynamic response of the structure. The results indicated that applied NFRP layer decreases the maximum dynamic displacement of the structure up to 91 percent. In addition, using nanofibers as reinforcement leads a 35 percent reduction in the maximum dynamic displacement of the structure.

• Steel and Composite Structures
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• 제47권2호
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• pp.147-165
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• 2023

The paper contrasts conventional seismic design with a design that incorporates buckling-restrained bracing in three-dimensional reinforced concrete buildings (BRBs). The suboptimal structures may be found using the multi-objective chimp optimization algorithm (MEN-ChOA). Given the constraints and dimensions, ChOA suffers from a slow convergence rate and tends to become stuck in local minima. Therefore, the ChOA is improved by niching and evolutionary operators to overcome the aforementioned problems. In addition, a new technique is presented to compute seismic and dead loads that include all of a structure's parts in an algorithm for three-dimensional frame design rather than only using structural elements. The performance of the constructed multi-objective model is evaluated using 12 standard multi-objective benchmarks proposed in IEEE congress on evolutionary computation. Second, MEN-ChOA is employed in constructing several reinforced concrete structures by the Mexico City building code. The variety of Pareto optimum fronts of these criteria enables a thorough performance examination of the MEN-ChOA. The results also reveal that BRB frames with comparable structural performance to conventional moment-resistant reinforced concrete framed buildings are more cost-effective when reinforced concrete building height rises. Structural performance and building cost may improve by using a nature-inspired strategy based on MEN-ChOA in structural design work.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.144-145
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• 2014

Nowadays, as to increased the workability of the press concrete and decrease the cracking, the fiber-reinforced admixture has been widely used. As the low adhesion force between the paste and fiber-reinforced admixture, it was considered as could not be used in the structure. Even more, as the loss of flowability and the exposure of the fiber, further study is needed. In this study, as the different environment and position of the building, the dosages of the fiber-reinforced admixture has also been changed. The fundamental properties and cracking of fiber-reinforced concrete have been tested.

• Advances in concrete construction
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• 제1권1호
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• pp.29-44
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• 2013

Post earthquake fire (PEF) can lead to the collapse of buildings that are partially damaged in a prior ground-motion that occurred immediately before the fire. The majority of standards and codes for the design of structures against earthquake ignore the possibility of PEF and thus buildings designed with those codes could be too weak when subjected to a fire after an earthquake. An investigation based on sequential analysis inspired by FEMA356 is performed here on the Life-Safety performance level of structures designed to the ACI 318-08 code after they are subjected to two different earthquake levels with PGA of 0.35 g and 0.25 g. This is followed by a four-hour fire analysis of the weakened structure, from which the time it takes for the weakened structure to collapse is calculated. As a benchmark, the fire analysis is also performed for undamaged structure and before occurrence of earthquake. The results show that the vulnerability of structures increases dramatically when a previously damaged structure is exposed to PEF. The results also show the damaging effects of post earthquake fire are exacerbated when initiated from second and third floor. Whilst the investigation is for a certain class of structures (regular building, intermediate reinforced structure, 3 stories), the results confirm the need for the incorporation of post earthquake fire in the process of analysis and design and provides some quantitative measures on the level of associated effects.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.139-144
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• 2001

The objective of this study is to investigate the behavior of 1/12 scale upper-wall lower-frame reinforced concrete structure subjected to earthquake excitations. For this purpose, Taft N21E earthquake accelerogram was simulated by using 4m$\times$4m shaking table. When the input acceleration is compared to that of output, it was found that simulation of shaking table is satisfactory. From the test results with peak ground acceleration(PGA) 0.22g, which corresponds to 0.11g in prototype by the similitude law, it can be observed that the model responded in elastic behavior and that large interstory drift occurred at the lower part of the structure.

• Computers and Concrete
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• 제19권3호
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• pp.333-338
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• 2017

In this paper, nonlinear vibration of embedded nanocomposite concrete is investigated based on Timoshenko beam model. The beam is reinforced by with agglomerated silicon dioxide (SiO2) nanoparticles. Mori-Tanaka model is used for considering agglomeration effects and calculating the equivalent characteristics of the structure. The surrounding foundation is simulated with Pasternak medium. Energy method and Hamilton's principal are used for deriving the motion equations. Differential quadrature method (DQM) is applied in order to obtain the frequency of structure. The effects of different parameters such as volume percent of SiO2 nanoparticles, nanoparticles agglomeration, elastic medium, boundary conditions and geometrical parameters of beam are shown on the frequency of system. Numerical results indicate that with increasing the SiO2 nanoparticles, the frequency of structure increases. In addition, considering agglomeration effects leads to decrease in frequency of system.

• Structural Engineering and Mechanics
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• 제67권3호
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• pp.311-316
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• 2018

Vibration of concrete beams reinforced by agglomerated silicon dioxide ($SiO_2$) nanoparticles is studied based on numerical methods. The structure is simulated by Euler-Bernoulli beam model and the Mori-Tanaka model is used for obtaining the effective material properties of the structure. The concrete beam is located in soil medium which is modeled by spring elements. The motion equations are derived based on energy method and Hamilton's principle. Based on exact solution, the frequency of the structure is calculated. The effects of different parameters such as volume percent of $SiO_2$ nanoparticles and agglomeration, soil medium and geometrical parameters of beam are shown on the frequency of system. The results show that with increasing the volume percent of $SiO_2$ nanoparticles, the frequency increases.