콘크리트에 발생하는 건조수축은 콘크리트 구조체 내부에 존재하는 수분의 이동에 의해 발생하며 강도발현시점 이후부터 점진적으로 그 크기가 커진다. 콘크리트에 발생할 수 있는 건조수축의 크기는 골재나 시멘트 등의 특성에 따라 다르나 약 40-1000 의 범위에서 발생하므로 그 크기는 무시할 수 없는 수준이다. 많은 연구자들은 콘크리트의 건조수축의 약 20-25%가 재령 2주내에, 약 50-60%가 3개월 내에, 80% 이상이 재령 1년 이내에 발생하는 것으로 판단하고 있다. 다만 콘크리트 포장에서는 깊이에 따라 건조수축의 발생의 진행정도가 다르며 이로 인해 포장체 상부와 하부에서의 수축차이가 생기는 부등건조수축이 발생하므로 단순히 구조체 전체가 동등하게 수축한다고 가정할 수 없다. 본 연구는 공항 콘크리트포장을 대상으로 한 유한요소해석 모형에 실제 현장에서 약 9개월간 계측한 슬래브 깊이별 실측 온도를 적용하여 계절적 온도변화에 의한 포장체의 거동을 해석하였다. 유한요소해석 결과와 실제 현장에서 계측한 슬래브 위치별, 깊이별 변형률을 비교 분석하였으며, 온도의 영향만을 반영하여 해석을 실시한 결과와 건조수축이 발생하는 실제 슬래브의 거동사이에 차이가 발생함을 확인하였다. 상대적으로 재령 초기에 건조수축의 발생이 작은 슬래브 바닥면을 기준으로 보정계수를 추정하여 해석결과를 보정하였으며 슬래브의 재령에 따른 깊이별 건조수축의 발생 경향을 확인할 수 있었다.

The WUF-W moment connection is a pre-qualified connection that can be used for special moment frames specified in current seismic design specifications. Since the stress distribution near the connection varies according to access hole configuration, the cyclic performance of WUF-W connections is strongly affected by the access hole configurations. To evaluate the connection performance according to various access hole configurations, it is expensive to conduct experiments with many connection specimens. Instead, finite element analyses (FEA) can be performed. Throughout the FEA, stress and strain distribution in the connection can be monitored at each loading step. The purpose of this study is to construct nonlinear 3-dimensional FE models for accurately predicting the cyclic behavior of WUF-W connections. For predicting connection fracture using FEA, an appropriate response index detecting the incidence of connection rupture is proposed.

This study performs finite Element stress analysis of flange connections at noise barriers with circular steel tubes, which have a light weight. Subsequent numerical simulation results for three types of models (standard, double, and standard models strengthen by ribs) present that the applied connections for target noise barriers constructed show suitable structural performance. In this paper, the existing finite element stress analysis using the ABAQUS program is further extended to study the local stress distribution of the noise barriers with new type circular steel tubes. The numerical results for various parameters are verified by comparing different types with stresses occurred in the noise barrier from the numerical simulation.

In recent years, the number of earthquakes has increased worldwide. There has been an extreme increase on the Korea Peninsula, which is considered a safety zone for earthquakes. In particular, in the event of earthquakes, most structures on the Korea Peninsula are severely damaged, because most are not designed to withstand them. Damage to and destruction of civil structures, such as bridges, nuclear facilities, and dams, is worse than that of other structures. It is necessary to evaluate and predict the extent of damage by earthquake magnitude, as the magnitude of earthquakes is increasing as well as the frequency. A major feature of the occurrence of earthquakes is uncertainty. For this reason, it is necessary to adopt a stochastic approach, and studies using this approach are increasing. However, although there have been several studies on bridges and nuclear facilities, there have been few studies on probabilistic seismic risk evaluation for multi-functional weirs. Thus, this study presents 3D multi-functional weirs and performs a time history analysis by using LS-DYNA, a general structure analysis program. Probabilistic seismic fragility assessment is conducted by Monte Carlo simulation.

Concrete-Filled Tube (CFT) has been used as a column of building and bride pier. CFT member consists of outer steel tube and in-filled concrete. Since the concrete is under tri-axial stress state by outer steel tube, the strength and deformation capacity of the in-filled concrete increases. This is called confinement effect of CFT. To simulate this confinement effect, modified stress-strain relationship of the in-filled concrete is generally used. However this approach is not a direct method to simulate the confinement effect, and more novel simulation technic is needed for in-depth understanding of the confinement effect. In this study, direct method for simulating the confinement effect of CFT was proposed, where the modified strain-stress relationship was not used. From the results, the proposed method agrees well with the test results.

As demands for freeform structure were gradually increased, researches about various shapes of claddings have been conducted. Particularly, claddings made from concrete easily made complex shapes. Because of this advantage, many researches about manufacturing methods and light weight of concrete mainly have been conducted. For example ALC (Autoclaved Lightweight Concrete) was the most popular claddings that had a great strength without aggregate and were cured at high temperature and pressure conditions. This paper showed multi-layer reinforcement system, exactly 5 layers polymer reinforcement method, that consisted of 3D printing material with low weight and high performance mechanical properties. Finite element analysis were performed to predict the maximum deformations loaded by wind and self-weight. Joints of analysis model were simplified as the pin joint. The variable of this analysis was the material arrangement of 3 layers located at center among exterior layer. Finally, the maximum deformations of analysis results were compared with the limitations of claddings.

Climate change resulted in the growing occurrence frequency of typhoons, and the damage it caused was also increasing. In this study, the soundproofing and windproof walls installed on the domestic road were modeled by using ABAQUS, a commercial finite element analysis program. Correspondingly, steel column, aluminum frame and transparent acrylic plate were modeled. Based on the result from individual part of soundproof wall model, the number of soundproof wall parts for optimal design was determined to be five parts. The design standard of road construction barrier was applied to this optimum model to perform the safety evaluation for strong wind disaster. In the future, it will be possible to improve the guidelines for design of soundproofing walls in Korea by carrying out further experiment to increase the reliability of safety evaluation of soundproofing walls.

At modern mechanical and automotive industry, the material with light weight proceeds in order to thr environmental issue and high performance. Machine part is fastened with numbers of bolts and nuts. Generally, the metal part at mechanical structure is fastened with bolt and nut through puncturing. But it is difficult to puncture at CFRP with the property of fiber structure like the general metal. In this study, the fracture behavior is investigated by the hole and crack at the plate of the unidirectional CFRP due to ply angle. The thickness of plate is 2 mm. Two laminates with the varied ply angles are layered and eight plies are made. The hole is placed at the center of plate and the cracks with the length of 2 mm are generated on both left and right sides from the hole. The finite element program of ANSYS is carried out in order to analyze the CFRP with fiber layer. As analysis, the maximum reaction force and equivalent stress are investigated due the angle of ply. The reaction force in case of the stacking angle of 90° is shown to be greatest among all specimens.

In this study, nonlinear finite element analysis based on the Modified Compression Field Theory has been conducted to evaluate shear strength of RC walls with opening. On the analysis, reinforcement ratio within development length of rebars nearby the opening was reduced in the model in order to investigate the effect of opening on shear strength of RC shear walls. The nonlinear finite element analysis has been verified through comparison with the test result in literature. Through the verification, it was investigated that the analysis considering the development length of rebars well reflected the effect of an opening on shear strength of RC shear walls while current design provisions did not reasonably consider one.

The boundary reaction method(BRM) is a substructure time domain method, it removes global iterations between frequency and time domain analyses commonly required in the hybrid approaches, so that it operates as a two-step uncoupled method. The BRM offers a two-step method as follows: (1) the calculation of boundary reaction forces in the frequency domain on an interface of linear and nonlinear regions, (2) solving the wave radiation problem subjected to the boundary reaction forces in the time domain. In the time domain analysis, the near-field soil is modeled to simulate the wave radiation problem. This paper evaluates the performance of the BRM according to modeling extent of near-field soil for the nonlinear SSI analysis of base-isolated NPP structure. For this purpose, parametric studies are performed using equivalent linear SSI problems. The accuracy of the BRM solution is evaluated by comparing the BRM solution with that of conventional SSI seismic technique. The numerical results show that the soil condition affects the modeling range of near-field soil for the BRM analysis as well as the size of the basemat. Finally, the BRM is applied for the nonlinear SSI analysis of a base-isolated NPP structure to demonstrate the accuracy and effectiveness of the method.

OBJECTIVES : The objective of this research is to determine the integrity of pavement structures for areas where voids exist. Furthermore, we conducted the study of voided-area analysis and remaining life prediction for pavement structures using finite element method. METHODS : To determine the remaining life of the existing voided areas under asphalt concrete pavements, field and falling weight deflectometer (FWD) tests were conducted. Comparison methods were used to have better accuracy in the finite element method (FEM) analysis compared to the measured surface displacements due to the loaded trucks. In addition, the modeled FEM used in this study was compared with well-known software programs. RESULTS : The results show that a good agreement on the analyzed and measured displacements can be obtained through comparisons of the surface displacement due to loaded trucks. Furthermore, the modeled FEM program was compared with the available pavement-structure software programs, resulting in the same values of tensile strains in terms of the thickness of asphalt concrete layers. CONCLUSIONS: The study, which is related to voided-area analysis and remaining life prediction using FEM for pavement structures, was successfully conducted based on the comparison between our methods and the sinkhole grade used in Japan.

In this study, refined finite element (FE) analyses intended to evaluate the capacity of the existing water purification plant structures against seismic force are conducted with an aim to predict possibility generating tension crack and compression crushing. The FE models for three types of main plant structures were constructed to take ground condition, boundary condition, and water interaction into consideration for advanced simulation. The nonlinear dynamic analyses were performed by using ground motion data which have been used for seismic design. Both compression crushing and tention crack, which are distributed over concrete plant structures during peak ground acceleration (PGA), are investigated by analyzing failure possibility controlled with the strain limits. After observing FE analysis results, it is possible to predict tenstion cracking which can be found at some parts of the main structure.

This study mainly evaluate the aseismic performance of the existing intake tower structure, which is one of the national important infra structures, on the basis of the refined finite element (FE) analysis results. The realistic evaluation for structural damage was conducted by using the nonlinear material model that takes tension and compression strength of deteriorate concrete into consideration during FE modeling. In addition, not only tension crack but also compression crushing was analyzed by utilizing field contour functions provided in the program during nonlinear dynamic analyses when peak ground acceleration (PGA) occurred. After observing FE analysis results, it can be shown that the damage of the intake tower is the most likely to occur at the water level and the base support.

In military, empty cartridge recovery case of personal small arms is a device used to collect the empty cartridge after consumption of bullets. It has different shapes depending on the shape of small arms. However, It should be designed in a shape that wraps around the outlet for empty cartridge and it should be no restrictions to the movement of small arms. It has been used to spread military. but military is demanding design improvement due to frequent damage of empty cartridge recovery case. In this report, We improved the shape of the product in order to prevent damage to the product and verified through the FEM analysis and prototype test. According to the result of simulation, best modified modelling of this study has been reduced about 19% of the stress compared to initial modelling. In addition, modified products were confirmed durability, wearability and fixability through fire test.

In this study, TbDyFe thin films with the thickness of 1000 Å are fabricated by DC magnetron sputtering. TbDyFe thin films are prepared by DC magnetron sputtering method. The pressure of Ar gas below 1.33 kPa and DC input power of 200 W are used for the sputtering conditions. During sputtering process the substrate holder is heated up to 150 ℃. The thin films are deposited to a thickness of 1000 Å on polyimide substrate with a thickness of 2 μm. The fabricated microstructures are observed by X-ray diffraction (XRD) and the film thickness is measured. Magnetostrictions are determined from the curvature of the thin films which are measured by the optical cantilever method. The experimental results are discussed with numerical data.

최근 서울 도심 지역에 위치한 주요 포장도로에서의 동공발생 문제가 다양한 원인으로 인하여 이전 보다 더 빈번하게 나타나는 것으로 대두되고 있는 실정이다. 이 문제는 포트홀과 싱크홀 수 증가와 포장 도로에서의 다른 문제들을 야기 시킨다. 사실, 포장도로에서의 동공발생을 일으키는 주체적인 원인은 강 우, 강설과 같은 기후 변화와 밀접한 관련이 있다. 이 연구에서는, 한국형도로포장설계법에 기반하여 개 발된 KPRP(Korea Pavement Research Program : 한국형 포장설계프로그램)를 이용하여 동상방지층 의 구조적 성능을 모니터링 하고, 유한요소해석 프로그램 중 하나인 KICTPAVE 프로그램을 이용하여 KPRP프로그램의 신뢰도를 확인하고자 한다. KPRP 프로그램은 한국형 도로포장설계법에 기반을 두고 개발 된 프로그램 이다. 사실. 이전에 사용되어지던 설계 법은 AASHTO Interim Guide Method(1972) 로, 한국형포장설계프로그램의 개발 전 국내에서 가장 보편적으로 사용된 설계법이다. 이 설계법은 주어 진 조건 하에서만 포장 단면을 설계하는 법을 도출해내기 때문에 다양한 조건에서의 설계와 구조적인 개 량이 어렵다는 지적이 나오게 되었다. 이를 보완하기 위하여 국내에서의 주어진 조건에 적합하게 도로 포장의 횡단을 설계하기 위해 개발된 한국형포장설계프로그램이 나오게 되었다. 본 연구에서는, KPRP 와 KICTPAVE를 이용하여 동상방지층의 구조적 성능을 더욱 정밀하게 연구하게 된다. 한국형포장설계프로그램은 설계조건을 반영한 후, 횡단면 조건 설정, 기상조건 반영, 교통량 반영, 포장 재료 물성치 반영 및 동상방지층 설치 여부 판단과정을 거쳐 공용성을 예측하게 된다. 설계조건 반영은 한 국형포장설계프로그램에서 제공하는 기본 DB를 활용하여 횡단 설계를 하였다. 본 연구는 효과적인 공용성 분석을 위하여 세 가지 경우로 나누어서 해석을 실시하였는데, 그 조건들은 아래 표 1에 나온 것과 같다. 표 1은 동상방지층의 구조적 성능을 한국형포장설계프로그램을 이용하여 분석해낸 결과 이다. 표 1을 보면 두께와 상관없이 모든 구조적 성능이 일치하게 되는 결과를 가져와서 KICTPAVE 프로그램을 이용하여 조 건을 5가지로 나누어 유한요소해석을 실시하였다. 각 층(동상방지층-노상토, 보조기층-동상방지층, 기층 -보조기층, 표층-기층, 표층 사이의 노드와 요소)은 5cm간격으로 0cm에서 20cm 까지 다섯 가지 경우의 조건으로 나누어서 해석을 하였다. 그 결과 보조기층과 동상방지층 사이의 변형률은 동상방지층의 두께가 두꺼워질수록 증가되는 현상을 보였다. 하지만, 이와는 반대로 노상토와 동상방지층 사이에서 발 생하는 변형률은 동상방지층의 두께가 두꺼워 질 수록 감소되는 현상을 보였다.

지난해 2월말 경 용산역 근처 공사현장 인근 인도에서 도로함몰이 발생하여 보행자가 추락하여 부상을 입는 사고가 발생했다. 이를 계기로 서울시는 도로함몰의 조기예방을 위해 세계 최고수준의 기술을 보유 한 일본 업체와 협력하여 차량형 GPR(Ground Penetrating Rader : 전자파를 지표에 투과하여 지하의 빈 공간 형상 데이터를 수집하는 레이더 장치)을 이용한 도로하부 동공탐사 용역을 실시하였다. 서울시 동공탐사용역을 계기로 현장적응 시운전과 기술진의 분석훈련을 거쳐 실질적 탐사는 지난해 12 월부터 시작되었으며 약 4개월 동안 도로함몰 개연성이 높은 주요 간선도로 48km구간에서 105개의 공동 을 발견하였으며 금년 말까지는 약 200여개를 포함해 총 300여개의 공동이 발견될 것으로 예상했다. 이번 조사로 발견된 공동 중 위험도가 가장 높은 A급 공동이 약 60%로 61개가 발견되었고 그보다 낮은 등급의 B급 공동이 35개가 발견되어 5월 말까지 복구할 예정이며 도로함몰 가능성이 그나마 낮은 C급 공동 8개는 연구를 위해 일정 기간 관찰 후 복구할 예정이라고 밝혔다. 서울시 자치구별 공동 발견 현황을 살펴보면 송파구가 약 30%인 32개로 가장 많은 공동이 발견되었고 뒤이어 용산구 21개, 종로구 19개 순으로 나타났 다. 본 연구는 상용 유한요소해석 프로그램인 ABAQUS를 이용하여 공동 규모에 따른 아스팔트 포장도로 의 거동에 대한 분석을 실시하였다. 이를 위해 공동의 규모는 공동 위험도 평가 등급에 따른 A, B ,C 등급 으로 분류하였으며 공동의 발생 범위는 1.5m 이내로 설정하였다. 해석을 위한 단면 구성은 아스팔트 콘크 리트 층, 보조기층, 노상의 구조로 이루어져 있으며 접합상태를 의미하는 tie contact를 선택하고 각 층의 재료에 대한 입력물성은 일반적으로 아스팔트 콘크리트 포장구조체에 사용되는 범위를 적용하였다. 해석 모델은 연직하중만이 작용하는 Axisymmetric으로 구성하였으며 해석에 사용된 하중은 포장도로 설계시 사용되는 원형 등분포하중으로 설정하였다. 해석은 각 층의 단면, 재료물성과 하중 그리고 공동의 규모를 변화시키며 실시하였고 아스팔트 포장체의 표면 처짐, 변형률 등을 분석하였다.

This study investigates the analytical study for developing PEB(Pre-Engineered Building) connection Steel damper. The state-of the art of the steel beam-column seismic connection details were studied previously to develop proper damper for PEB connection. Finite element analysis is performed to develop the prototypes of damper under cyclic load. The study parameters of analysis are the shape, length, thickness, orientation and location of damper. As a result of finite element analysis, three prototype damper details for PEB seismic connection are derived. One is tapered plate on the lower flange of the rafter, another is C-plate on the center of panel zone and the other is brace on the beam-column connection.