• Structural Engineering and Mechanics
• /
• 제58권5호
• /
• pp.799-823
• /
• 2016

A finite element model for the non-linear dynamic analysis of a reinforced concrete (RC) containment shell of a nuclear power plant subjected to extreme loads such as impact and earthquake is presented in this work. The impact is modeled by using an uncoupled approach in which a load function is applied at the impact zone. The earthquake load is modeled by prescribing ground accelerations at the base of the structure. The nuclear containment is discretized spatially by using 20-node brick finite elements. The concrete in compression is modeled by using a modified $Dr{\ddot{u}}cker$-Prager elasto-plastic constitutive law where strain rate effects are considered. Cracking of concrete is modeled by using a smeared cracking approach where the tension-stiffening effect is included via a strain-softening rule. A model based on fracture mechanics, using the concept of constant fracture energy release, is used to relate the strain softening effect to the element size in order to guaranty mesh independency in the numerical prediction. The reinforcing bars are represented by incorporated membrane elements with a von Mises elasto-plastic law. Two benchmarks are used to verify the numerical implementation of the present model. Results are presented graphically in terms of displacement histories and cracking patterns. Finally, the influence of the shear transfer model used for cracked concrete as well as the effect due to a base slab incorporation in the numerical modeling are analyzed.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
• /
• pp.111-114
• /
• 2005

While the existing reinforced concrete flat plate(RC flat plate) has a lot of advantages including reduced building height, it has some weak points such as many steel bars and the brittle rupture by punching shear. Compared with the RC flat plate, the post-tensioned flat plate (PT flat plate) has not only the same merits, but it also makes longer span possible and induces slab-column connections to be failed with the ductile behavior rather than with the brittle behavior by means of post-tensioning. However, it is difficult to define the joint behavior of PT flat plate under vertical and lateral loads since there are limit experimental results. For this reason, the experimental study is undertaken to investigate the comparison of behavior of PT flat plate and RC flat plate, and how flat plate(Gravity Load Resisting System) is displaced as lateral loads, like the wind and the earthquake, are occur. The result of this experiment shows that PT flat plate is generally superior to RC flat plate in terms of controlling crack, postponing stiffness deterioration, energy dissipation, etc.

• 한국실내디자인학회논문집
• /
• 제15권6호
• /
• pp.172-177
• /
• 2006

Most of the Korean multi-dwelling houses have less than 20 years of lifespan. Because the environmental issues such as energy consumption, limited resources, and demolition waste problems became been more and more critical, we now need to focus on long lasting and adaptable buildings. Korean wall bearing apartment buildings are constructed with site cast concrete for core, exterior, and interior together with pipes varied, so when the buildings are old and life style of the users changes, it is difficult to maintain and renovate these buildings. In this study, to resolve the problems described above, two types of Korean long life multi-dwelling housing models which represent improved durability and adaptability responding user's needs and life style changes were proposed with various methods as follows: Either column and beam structure or flat slab structure was used to utilize space better. To make maintenance easier and renovation economical for both public space and each unit, plumbing pipes, ducts, and conduits were clustered at the cores and public corridors with access doors and light weight partitions with steel studs and raised floors or above-ceiling spaces were used in lieu of site cast concrete walls and floor slabs with varied pipes.

• 자원리싸이클링
• /
• 제6권1호
• /
• pp.40-46
• /
• 1997

하수처리에 있어서 오니 처분 문제는 아주 심각하다. 슬러지의 최종처분시 가장 중요한 비중을 차지하는 것은 수분제거하 할 수 있다. 슬러지 건조는 가열에 의해 고.액을 분리하여 재이용, 소각, 처분을 위한 전처리 공정이다. 본 연구의 목적은 초고주파로 하수오니를 건조후, 실험값과 이론값을 비교하기 위하여 수행하였다. 초고주파 건조는 속도가 빠르고 효율이 매우 높다. 건조시 물질전달은 1차원적이라 가정하였다. 건조속도곡선에서, 감율속도기간에서의 수분이동은 확산에 의한다. 두께 0.2cm인 시료에서 모델과 실험결과가 일치함을 알 수 있다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
• /
• pp.137-137
• /
• 2000

The surface collective modes of thin K films deposited on Al(111) have been investigated using frequency dependent photoyield measurements and momentum resolved inelastic electron scattering. Jellium based theoretical calculations have predicted a richer set of features in the thin films than for the surface of a semi-infinite solid because there are th interference between two interfaces (substrate-film and film-vacuum) and heavy damping on the substrate. The use of an optical probe and electron scattering has allowed us to draw a more complete picture of the dynamic screening in thin films. The number, dispersion, damping and optical activity of the collective modes of the thin films have been measured as a function of K film thickness. New overlayer-induced excitations are observed : At qII=0, they correspond to the antisymmetric slab mode and the multipole surface plasmon. At finite qII=0, these modes undergo a transition towards the K multipole and monopole surface plasmons. With increasing coverage, the overlayer excitations turn into the collective modes of semi-infinite K. For a consistent interpretation of photoyield and electron energy loss spectra it is crucial to account for the non-analytic dispersion of the overlayer modes at small parallel wave vectors and for the finite angular resolution of the detector. The observed dispersions confirm predictions based on the time-dependent density functional approach.

• 지질학회지
• /
• 제54권6호
• /
• pp.683-694
• /
• 2018

섭입은 지구의 물질 및 에너지 순환에서 중요한 역할을 담당할 뿐만 아니라 우리의 삶에 밀접한 지질 현상인 지진과 호화산을 발생시키므로 많은 연구가 이루어져 왔다. 그 중에서 맨틀 내부의 섭입해양판처럼 우리가 직접 관찰할 수 없는 곳에서 발생하는 지질 현상에 대한 정량적 연구에 컴퓨터 수치모델링이 널리 이용되어 왔다. 이 연구에서는 다양한 연구진들에 의해 사용되고 있는 섭입대 수치모델링의 벤치마크를 수행하였다. 섭입대 수치모델링을 위하여 유한요소법 기반 상용 소프트웨어인 콤솔 멀티피직스를 사용하였으며 계산된 결과는 과거 수행된 벤치마크 결과와 잘 일치하였다.

• Steel and Composite Structures
• /
• 제33권2호
• /
• pp.209-224
• /
• 2019

This paper describes a study of the mapping relationship between the vertical deformation of bridge structures and rail deformation of high-speed railway, taking the interlayer interactions of the bridge subgrade CRTS II ballastless slab track system (HSRBST) into account. The differential equations and natural boundary conditions of the mapping relationship between the vertical deformation of bridge structures and rail deformation were deduced according to the principle of stationary potential energy. Then an analytical model for such relationship was proposed. Both the analytical method proposed in this paper and the finite element numerical method were used to calculate the rail deformations under three typical deformations of bridge structures and the evolution of rail geometry under these circumstances was analyzed. It was shown that numerical and analytical calculation results are well agreed with each other, demonstrating the effectiveness of the analytical model proposed in this paper. The mapping coefficient between bridge structure deformation and rail deformation showed a nonlinear increase with increasing amplitude of the bridge structure deformation. The rail deformation showed an obvious "following feature"; with the increase of bridge span and fastener stiffness, the curve of rail deformation became gentler, the track irregularity wavelength became longer, and the performance of the rail at following the bridge structure deformation was stronger.

• Computers and Concrete
• /
• 제27권2호
• /
• pp.153-162
• /
• 2021

This paper aims to simulate the isotropic elastic damage theory of Liu Jun (2012) using the self-programmed UMAT subroutine in the interface of ABAQUS. Liu Jun (2012)'s method based on the mechanic theory can not be used interactively with the currently commonly used finite element software ABAQUS. The advantage of this method in the paper is that it can interact with ABAQUS and provide a constitutive program framework that can be modified according to user need. The model retains the two scalar damage variables and the corresponding two energy dissipation mechanisms and damage criteria for considering the tensile and compressive asymmetry of concrete. Taking C45 concrete as an example, the relevant damage evolution parameters of its tensile and compressive constitutive model are given. The study demonstrates that the uniaxial tensile stress calculated by the subroutine is almost the same as the Chinese Concrete Design Specification (GB50010) before the peak stress, but ends soon after the peak stress. The stress-strain curve of uniaxial compression calculated by the subroutine is in good agreement with the peak stress in Chinese Concrete Design Specification (GB50010), but there is a certain deviation in the descending stage. In addition, this paper uses the newly compiled subroutine to simulate the shear bearing capacity of the shear key in a new structural system, namely the open-web sandwich slab. The results show that the damage constitutive subroutine has certain reliability.

• Nuclear Engineering and Technology
• /
• 제53권5호
• /
• pp.1391-1402
• /
• 2021

The aim of this work is to prepare a neutron noise calculator based on the second order of average current nodal expansion method (ACNEM). Generally, nodal methods have the ability to fulfill the neutronic analysis with adequate precision using coarse meshes as large as a fuel assembly size. But, for the zeroth order of ACNEM, the accuracy of neutronic simulations may not be sufficient when coarse meshes are employed in the reactor core modeling. In this work, the capability of second order ACNEM is extended for solving the neutron diffusion equation in the frequency domain using coarse meshes. For this purpose, two problems are modeled and checked including a slab reactor and 2D BIBLIS PWR. For validating of results, a semi-analytical solution is utilized for 1D test case, and for 2D problem, the results of both forward and adjoint neutron noise calculations are exploited. Numerical results indicate that by increasing the order of method, the errors of frequency dependent coarse mesh solutions are considerably decreased in comparison to the reference. Accordingly, the accuracy of second order ACNEM can be acceptable for the neutron noise calculations by using coarse meshes in the nuclear reactor core.

• Computers and Concrete
• /
• 제29권2호
• /
• pp.69-79
• /
• 2022

For long underground box utility tunnels, post-tensioned precast concrete is often used. Between precast tunnel segments, sealed waterproof flexible joints are often specified. Fault displacement can lead to excessive deformation of the joints, which can lead to reduction in waterproofing due to diminished contact pressure between the sealant strip and the tunnel segment. This paper authenticates utilization of a finite element model for a prefabricated tunnel fault-crossing founded on ABAQUS software. In addition, material parameter selection, contact setting and boundary condition are reviewed. Analyzed under normal fault action are: the influence of fault displacement; buried depth; soil friction coefficient, and angle of crossing at the fault plane. In addition, distribution characteristics of the utility tunnel structure for vertical and longitudinal/horizontal relative displacement at segmented interface for the top and bottom slab are analyzed. It is found that the effect of increase in fault displacement on the splice joint deformation is significant, whereas the effects of changes in burial depth, pipe-soil friction coefficient and fault-crossing angle on the overall tunnel and joint deformations were not so significant.