• 한국산학기술학회논문지
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• 제16권6호
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• pp.4245-4252
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• 2015

유리섬유강화폴리머(GFRP) 판을 현장타설 고강도콘크리트 구조물의 영구거푸집으로 사용하기 위한 실험을 수행하였다. 현재 생산되는 GFRP 판의 경우 표면이 매끈하여 콘크리트와 일체 거동에 다소 문제점을 갖고 있다. 따라서 본 연구에서는 GFRP 판 하부의 잔골재 부착여부, GFRP판 웨브의 천공유무 및 간격, 상부 플랜지 폭을 실험 변수로 하여 현장타설 고강도콘크리트와 GFRP를 영구거푸집으로 활용한 전단경간비가 짧은 합성보의 휨/전단파괴거동을 분석하였다. GFRP 판 웨브를 천공하지 않은 경우 잔골재 부착효과 여부를 위한 실험 결과, 잔골재를 부착한 경우 미부착의 경우 보다 약 47% 정도의 높은 극한하중 값을 보여주며, 파괴형태도 휨/전단파괴모드를 보여 주었다. 웨브의 천공유무 및 간격효과는 잔골재를 부착하지 않은 경우 천공간격이 조밀한 경우가 약 24% 정도 높은 극한하중 값을 보여주었으며, 잔골재를 부착한 경우 천공 간격이 조밀하지 않은 경우가 약 25% 정도 낮은 극한하중 값을 보여주었다. 상부플랜지 영향을 살펴보면, 폭 40mm 경우가 20mm에 비해 약 17% 정도 큰 극한하중 값을 보여주었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.857-860
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• 2006

In the present study, the method and procedure for analysis of impact damage behavior for concrete under penetration and perforation of projectile is investigated. Conservation law, equation of motion, initial and boundary conditions, and FEM formulation are introduced and derived respectively. Specially, the constitutive equation which rate-dependent damage combined with rate-dependent plasticity within the appropriate framework of theory of thermodynamics is examined. This paper aimed at the review with respect to impact damage models for concrete to develop that model. This paper is a basis research for the development of impact damage model for concrete.

• Steel and Composite Structures
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• 제36권2호
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• pp.143-161
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• 2020

In nanosized structures as the surface area to the bulk volume ratio increases the classical continuum mechanics approaches fails to investigate the mechanical behavior of such structures. In perforated nanobeam structures, more decrease in the bulk volume is obtained due to perforation process thus nonclassical continuum approaches should be employed for reliable investigation of the mechanical behavior these structures. This article introduces an analytical methodology to investigate the size dependent, surface energy, and perforation impacts on the nonclassical bending behavior of regularly squared cutout nanobeam structures for the first time. To do this, geometrical model for both bulk and surface characteristics is developed for regularly squared perforated nanobeams. Based on the proposed geometrical model, the nonclassical Gurtin-Murdoch surface elasticity model is adopted and modified to incorporate the surface energy effects in perforated nanobeams. To investigate the effect of shear deformation associated with cutout process, both Euler-Bernoulli and Timoshenko beams theories are developed. Mathematical model for perforated nanobeam structure including surface energy effects are derived in comprehensive procedure and nonclassical boundary conditions are presented. Closed forms for the nonclassical bending and rotational displacements are derived for both theories considering all classical and nonclassical kinematics and kinetics boundary conditions. Additionally, both uniformly distributed and concentrated loads are considered. The developed methodology is verified and compared with the available results and an excellent agreement is noticed. Both classical and nonclassical bending profiles for both thin and thick perforated nanobeams are investigated. Numerical results are obtained to illustrate effects of beam filling ratio, the number of hole rows through the cross section, surface material characteristics, beam slenderness ratio as well as the boundary and loading conditions on the non-classical bending behavior of perforated nanobeams in the presence of surface effects. It is found that, the surface residual stress has more significant effect on the bending deflection compared with the corresponding effect of the surface elasticity, Es. The obtained results are supportive for the design, analysis and manufacturing of perforated nanobeams.

• 한국군사과학기술학회지
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• 제16권3호
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• pp.398-404
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• 2013

The simulation of the ballistic trajectory of penetrator into the spaced multi-layer RC targets is very important to predict the hitting condition in subsequent target. Because of perturbation by lateral load of penetrator caused by asymmetric hitting position between penetrator and steel bar reinforcement, penetrator rotates and deviates from the straight path. Therefore, penetration capability of penetrator is decreased in the subsequent targets. This paper presents the result of the penetration of steel-bar-reinforced concrete target by using the explicit finite element code LS-DYNA. A series of computations is performed and compared to experimental data and the computed results are in good agreement with the experimental results over a wide range of velocities. And then we conduct the simulation according to various RC target hitting condition and impact velocities.

• Computers and Concrete
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• 제12권1호
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• pp.37-51
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• 2013

The responses of reinforced concrete slabs subject to an impact loading near the ultimate load range are explored. The analysis is carried out on a simply supported rectangular reinforced concrete slab using a nonlinear explicit dynamic procedure and considering three material models: Drucker-Prager, modified Drucker-Prager, and concrete damaged plasticity, available in the commercial finite element software, ABAQUS/Explicit. For comparison purposes, the impact force-time response, steel reinforcement failure, and concrete perforation pattern are verified against the existing experimental results. Also, the effectiveness of mesh density and damage wave propagation are studied independently. It is shown that the presently adopted finite element procedure is able to simulate and predict fairly accurate the behavior of reinforced concrete slab under impact load. More detailed investigations are however demanded for the justification of effects coming from an imperfect projectile orientation as well as the load and structural surface conditions, including the impulsive contacted state, which are inevitable in an actual impact environment.

• 한국전산구조공학회논문집
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• 제27권3호
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• pp.147-154
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• 2014

충격 및 폭발하중으로 인한 위험으로부터 구조물의 안정성을 확보하기 위한 필요성의 증대에 따라 고율변형을 받는 콘크리트의 거동은 중요한 연구주제가 되었다. 콘크리트의 고율변형 거동은 정적인 상태와는 다른 독특한 거동을 보이기 때문에 다양한 고율변형모델들이 제안되어 고율변형 상태를 수치해석하는데 사용되고 있다. 이러한 수치해석 과정에서 발생하는 문제가 요소의 크기에 따라 수치해석결과가 크게 변하는 요소의존성 문제이다. 본 논문에서는 파괴에너지이론에 기초하여 요소의존성을 최소화할 수 있는 기준식을 제안하고 HJC(Holmquist Johnson Cook)모델을 이용한 관통수치해석을 통해 기준식을 검증하였다. 그 결과 기준식을 통해 산정된 파괴변형률을 수치해석상에 적용해줌으로써 해석결과의 요소의존성이 감소하였고 해의 정확성 또한 향상되는 것을 파악할 수 있었다.

• Computers and Concrete
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• 제9권4호
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• pp.311-325
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• 2012

In this paper, we examine the behavior of the High-Rate Brittle Microplane (HRBM) concrete model based on a series of penetration experiments. These experiments were conducted with three different slab thicknesses (127, 216 and 254 mm) that provided a significant challenge for the numerical simulations. The 127 mm slab provided little resistance, the 216 mm slab provided nominal resistance and the 254 mm slab approached the perforation limit thickness of the projectile. These experiments provide a good baseline for evaluating material models since they have been shown to be extremely challenging; in fact, we have not encountered many material models that can provide quantitatively predictive results in terms of both projectile exit velocity and material damage. In a companion paper, we described the HRBM material model and its fit to various quasi-static material property data for WES-5000 concrete. In this paper, we show that, when adequately fit to these quasi-static data, the HRBM model does not have significant predictive capabilities, even though the quasi-static material fit may be exceptional. This was attributed to the rate-dependent response of the material. After various rate effects were introduced into the HRBM model, the quantitative predictive nature of the calculations dramatically increased. Unfortunately, not much rate-dependent material property data are in the literature; hence, accurate incorporation of rate effects into material models is difficult. Nonetheless, it seems that rate effects may be critical in obtaining an accurate response for concrete during projectile perforation events.

• 한국강구조학회 논문집
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• 제15권2호
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• pp.109-116
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• 2003

벽체용 박판냉간성형 Lip-C-형강의 구조적인 거동에 관한 연구의 일환으로 횡하중을 받는 스터드 벽체의 휨강도에 관한 실험적인 연구가 수행되었다. 시험체는 3개 또는 4개의 Lip-C-형강 스터드 부재의 양단을 C-형강 트랙으로 고정하여 제작되었다. 실험의 주요 변수는 스터드 복부의 천공 여부, 보강채널(bridge channel)의 간격 및 개수 그리고 보강 채널의 고정 및 스터드 플랜지의 간격 유지용 특수 클립(Clip)의 개수 등이며, 스터드의 인장측 플랜지에 부착된 합판과 석고보드의 벽에 강도에 미치는 영향이 연구되었다. 실험에 의한 휨강도는 AISI시방서(1996)에 근거한 강도와 비교하였다.

• Advances in aircraft and spacecraft science
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• 제10권3호
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• pp.257-279
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• 2023

This manuscript is dedicated to deriving the closed form solutions of free vibration of viscoelastic nanobeam embedded in an elastic medium using nonlocal differential Eringen elasticity theory that not considered before. The kinematic displacements of Euler-Bernoulli and Timoshenko theories are developed to consider the thin nanobeam structure (i.e., zero shear strain/stress) and moderated thick nanobeam (with constant shear strain/stress). To consider the internal damping viscoelastic effect of the structure, Kelvin/Voigt constitutive relation is proposed. The perforation geometry is intended by uniform symmetric squared holes arranged array with equal space. The partial differential equations of motion and boundary conditions of viscoelastic perforated nonlocal nanobeam with elastic foundation are derived by Hamilton principle. Closed form solutions of damped and natural frequencies are evaluated explicitly and verified with prestigious studies. Parametric studies are performed to signify the impact of elastic foundation parameters, viscoelastic coefficients, nanoscale, supporting boundary conditions, and perforation geometry on the dynamic behavior. The closed form solutions can be implemented in the analysis of viscoelastic NEMS/MEMS with perforations and embedded in elastic medium.

• Steel and Composite Structures
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• 제25권4호
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• pp.505-521
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• 2017

The steel plate shear wall with beam-only connected infill plate (SSW-BO) is an innovative lateral load resisting system consisting of infill plates connected to surrounding beams and separated from the main columns. In this research, the effects of perforation diameter as well as slenderness ratios of infill plates on the hysteresis behavior of SSW-BO systems were studied experimentally. Experimental testing is performed on eight one-sixth scaled one-story SSW-BO specimens with two plate thicknesses and four different circular opening ratios at the center of the panels under fully reversed cyclic quasi-static loading in compliance with the SAC test protocol. Strength, stiffness, ductility and energy absorption were evaluated based on the hysteresis loops. It is found that the systems exhibited stable hysteretic behavior during testing until significant damage in the connection of infill plates to surrounding beams at large drifts. It is also seen that pinching occurred in the hysteresis loops, since the hinge type connections were used as boundaries at four corners of surrounding frames. The strength and initial stiffness degradation of the perforated specimens containing opening ratio of 0.36 compared to the solid one is in the range of 20% to 30% and 40% to 50%, respectively.