기류흐름에 의한 다양한 진동현상이 구조물에 발생한다. 이중 와류에 의한 진동은 구조물의 고유진동수와 일치하는 와류의 방출진동수에서는 Lock-in 현상에 의해 큰 진동을 유발하며 구조물에 많은 영향을 미치는 것으로 알려져 있다. 그러나 대부분의 와류 현상은 등류에서 관찰되는 현상을 대상으로 이루어졌다. 본 연구에서는 대기 경계층에서 높이에 따라 풍속이 변화하는 난류에 의하여 구조물에 발생하는 와류의 영향을 풍동실험을 통하여 평가하였다. 탄성체 모형실험으로부터 계측된 가속도로부터 하중추정법을 이용 하여 와류진동을 발생시키는 1차 모드 와류하중을 추정하였으며 그 특성을 분석하였다. 추정된 와류하중의 스펙트럼을 보면 구조물 최상층 풍속의 약 88-90%에 해당하는 풍속에서 와류방출진동수가 두드러지게 나타나면서 피크를 형성하는 것으로 나타났다. 또한, 풍 속이 점차 증가할수록 와류하중의 스펙트럼의 진동수범위가 증가하는 것으로 나타났다. 이러한 난류에 의한 와류하중을 특성을 반영 하면 초고층 구조물 등에 발생하는 풍직각 방향의 진동현상을 보다 효과적으로 파악하는데 활용될 수 있을 것으로 사료된다.

Spatial Structure has suffered from a lot of damage due to the use of lightweight roofs. Among them, the damage caused by strong winds was the greatest, and the failure of the calculation of the wind load was the most frequent cause. It provides that wind tunnel test is used to calculate the wind load. However, it is often the case that the wind load is calculated based on the standard of wind load in the development design stage. Therefore based on this, the structure type and structural system and member design are often determined. Spatial structure is usually open at a certain area. The retractable roof structure should be operated with the open roof in some cases, so the wind load for the open shape should be considered, but it is not clear on the basis of the wind load standard. In this paper, the design wind pressure of a closed and retractable roof structure is calculated by KBC2016, AIJ2004, ASCE7-10, EN2005, and the applicability of wind pressure coefficient is compared with wind tunnel test.

In recent years, single layer latticed domes have attracted many designers and researchers’s attention all over the world, because single layer latticed domes as space structure are of great advantage in not only mechanical rationality but also function, fabrication, construction and economic aspect. Yamada developed the shape factor S which represents the shape of spherical latticed dome from a structural perspective as well as a geometric perspective. According to a prior study, the structural behavior and the buckling characteristics of the latticed dome were mostly noticeable when the shape factor of latticed dome was in the range of 1.5 to 5. That is, S, in the range of 1.5 to 5, are able to estimate not only overall buckling, but also member buckling and nodal buckling. In this study, we developed shape models using various size of members with the fixed rise-span ratio. One particular characteristic of the latticed dome is that it is not only light in weight but also high in strength. But the aiming at the use of light-weight materials and at the minimized section of members may result in buckling to cause an unstable state of the overall structure when the external force reaches a limitation. Especially, the structural strength is disadvantageous to the snow loads than the earthquake loads because of light-weight, and is greatly affected by the conditions of loading. This paper is to develop the structural stability according to the shapes and load conditions for single-layer latticed spherical dome with 300m span.

Porous materials such as polymeric foam are widely adopted in engineering and biomedical fields. Porous materials often exhibit complex nonlinear behaviors and are sensitive to material and environmental factors including cell size and shape, amount of porosity, and temperature, which are influenced by the type of base materials, reinforcements, method of fabrication, etc. Hence, the material characteristics of porous materials such as compressive stress-strain behavior and void volume fraction according to aforementioned factors should be precisely identified. In this study, unconfined uniaxial compressive test for two types of closed-cell structure polyurethane foam, namely, 0.16 and 0.32 g/cm3 of densities were carried out. In addition, the void volume fraction of three different domains, namely, center, surface and buckling regions under various compressive strains (10%, 30 %, 50 % and 70 %) were quantitatively observed using Micro 3D Computed Tomography(micro-CT) scanning system. Based on the experimental results, the relationship between compressive strain and void volume fraction with respect to cell size, density and boundary condition were investigated.

The coupled shear wall system with coupling beams is an efficient structural system for high-rise buildings because it can provide excellent ductility and energy dissipation to the buildings. The objective of this study is to simulate the hysteretic behavior of diagonally reinforced concrete coupling beams including pinching and cyclic deteriorations in strength and stiffness using a numerical model. For this purpose, coupling beams are modeled with an elastic beam element and plastic spring element placed at the beam ends. Parameters for the analytical model was calibrated based on the test results of 6 specimens for diagonally reinforced concrete coupling beams. The analytical model with calibrated model parameters is verified by comparing the hysteretic curves obtained from analysis and experimental tests.

This paper relates to the study of load characteristics applicable to wind turbine generators induced by earthquakes. An artificial design earthquake wave generated through the target spectrum and the envelope function of Richter Magnitude Scale (ML) 7.0 as in ASCE4-98 was created. A simulation of earthquake loads were performed according to the design load cases (DLC) 9.5~9.7 of GL guidelines. Additionally, simulation of seismic loads experienced by Wind Turbines installed in the Gyeongju region were carried out utilizing artificial earthquakes of ML 5.8 simulating the real earthquakes during the Gyeongju Earthquakes of Sept. 2016.

The planetary gearing system is compact and lightweight. The performance of planetary gearing system which uses floating intermediate rings have been found to be very good for practical systems. To apply this system for the reduction of rotation of an engine, in designing stage, the quantitative estimate of the load sharing factors is required for understanding the performance. The method widely used for this purpose is to make use of elastic deformation of components of the structure or to utilize hydrodynamic oil film. This paper shows the way how to analyze the static load sharing factors by using the coefficient ''. This method can be applied for non-linear systems such as oil film bearing. The influences of various factors on '' of oil film spring are also shown. Furthermore, It is established in this study that the use of floating intermediate ring in designing the planetary gearing system has a very high reliability.

아스팔트 포장 신설 및 절삭 덧씌우기 포장 시 아스팔트층 층간 부착은 포장수명에 중요한 요소로서, 층간 부착을 위한 택코트 불량으로 인한 포장 경계면의 접착력 부족은 밀림, 신․구포장층의 분리, 조기 피로균열, 포트홀 등 파손을 유발하며 포장수명을 감소시킨다(Donovan 등, 2000; Ozer 등 2008, 조문진, 2013). 또한 층간 비 접착은 포장 공용수명을 60% 단축시키고(Roffe and Chaignon, 2002), 접착력 10% 손실은 포장수명의 50%를 단축시킨다(King and May, 2006). 택코트의 품질관리를 위해 미연방항공청에서는 시공 온도(기온 10℃ 이상), 살포량(0.2∼0.5 ) 기준을 권고하고 있으며, 도로공사표준시방서(국토부, 2016)에서는 택코트 재료 품질기준(제조 후 60일 이내), 시공 온도(기온 5°C 이상), 살포량(0.3∼0.6 ) 등을 규정하고 있으며, 살포량은 시험시공을 통해 결정하도록 권고하고 있다. 현재 아스팔트 덧씌우기포장 시 사용하는 접착강도의 기준이 없는 실정으로 도로분야에서는 KS F 4932 교면용 도막 방수재의 접착강도 기준을 준용하여 사용하고 있는 실정이다. 그리고 택코트 재료별 살포량 0,0, 0.2, 0.4, 0.6, 0.8에 따른 인장강도 및 전단강도 분석결과(조문진, 2013), 콘크리트 포장 위 아스팔트 포장의 경우 모든 유화아스팔트 재료에서 살포량 0.4일 경우 가장 높은 전단접착강도를 나타냈으며, 인장접착강도는 0.4∼0.6에서 최대값을 보였다. 또한 아스팔트 포장 위 아스팔트 덧씌우기의 경우 인장강도는 1.0∼1.6MPa, 전단강도는 살포량 0.4에서 최대 인장 및 전단 접착강도를 나타냈다. 공항에서의 아스팔트 층의 접착력 또한 기준이 없는 실정으로, KS F 4932 교면용 도막 방수재의 접착강도 기준 준용 대신 항공기 바퀴의 수평하중을 고려한 접착강도 확보가 필요할 것이다. 항공기 움직임 후 정지시 발생하는 수평하중을 층 간 전단력으로 환산하여 이를 만족하는 전단강도를 발현하는 살포량을 공항 아스팔트 포장에서의 택코트 살포량 기준으로 삼는 것을 연구 목표로 항공기 대표 기종별 전단력을 <표 1>과 같이 환산하였다. <표 1>과 같이 항공기 수평하중에 의한 전단력을 대표기종별로 분석한 결과 0.41∼0.52MPa 분포를 보였으며, 이는 KS F 4932 교면용 도막 방수재의 접착강도의 전단접착강도 기준 0.15MPa 보다 훨씬 높은 값을 보인 것이다. 택코트 살포량에 따른 접착특성 분석(조문진, 2013)의 결과에 비추어 볼 때 항공기 수평하중에 의한 전단력을 만족할 수 있는 경우는, 콘크리트 포장 위 아스팔트 포장에서는 급경성 유화아스팔트 재료만 만족하며 0.3 이상부터 기종별 최대 전단력인 0.52Mpa를 만족하며 약 0.4에서 최대값을 나타내다. 아스팔트 포장 위 아스팔트 포장의 경우 일반 유화아스팔트에서도 0.2∼0.8 살포량 전구간에서 전단강도 0.8MPa 이상을 보이고 있고, 0.4 이상부터 최대 인장강도를 보이고 있다. 따라서 공항에서의 택코트 적정 살포량은 기상 및 현장 여건에 따라 다를 수 있으나 0.4이 적정한 것으로 판단된다. 또한 본 연구에서는 공사 현장에서의 택코트 살포량 관리를 위해 0.4 만족하는 차량형 디스트리뷰터 속도 시험을 실시하였다. 시험종이를 깔아 택코트 시공 전 후 무게 차로 포설량을 측정하였으며, 10, 20, 30km/hr 차량속도로 살포량을 측정한 결과 10km/hr에서 0.4.0∼0.42의 살포량이 측정되어 디스트리뷰터 적정속도는10km/hr로 판단된다.

현재 지하에 매설되는 암거는 현장타설 형태보다 품질확보 및 유지관리에 우수하고, 특히 시공연장이 긴 경우 공기단축에 유리한 PC(Precast) 암거형태가 주로 시공되고 있다. 이러한 PC암거가 연약지반 위에 시공되거나 성토·절토 변곡부에 시공되는 경우 등 다양한 시공환경에 따라 배수암거의 부등침하가 예상될 수 있다. 이러한 부등침하가 발생되면 구조물에 균열 및 변형이 유발될 뿐만 아니라 나아가 구조물의 붕괴까지 초래할 수 있지만 실제 PC암거 구조물의 부등침하를 고려한 실험적인 연구나 평가는 어려운 실정이다(신창순, 2008). 따라서 PC암거 부재의 설계시 토피의 변화, 지반 및 하중조건 등 실제 시공조건을 면밀히 고려한 구조검토가 필요하다. 또한 도로에 작용하는 차량 활하중과 달리 일반적으로 항공기 활하중은 메인기어 각하중에 대한 접지폭에 따라 활하중을 산정하며(이경환, 2004), 이러한 Kogler의 근사해법에 따라 계산된 항공기의 하중 재하 구조는 일반적으로 암거의 매설깊이(토피고)가 증가함에 따라 비례하는 고정하중이나 토압과는 달리 <그림 2>와 같은 분포양상을 보이게 된다. 따라서 토피변화에 따른 항공기 하중에 대한 분포 특수성을 고려하여, PC암거의 구조안전성을 확보하는 것이 더 합리적인 부재설계가 될 수 있다. 본 연구에서는 설계항공기(b747-400)에 적합한 PC암거 부재설계를 위하여 범용 유한요소해석 프로그램인 Midas 2017를 이용하여 3D 구조해석을 수행하고, 토피 변화에 따른 항공기 하중분포를 적용하여 PC암거의 응력변화를 분석하였다. 분석결과, 지중에 매설되는 암거는 기타요인(콘크리트의 건조수축, 온도하중, 지반반력계수)에 의한 응력변화보다 토피고에 따른 항공기 활하중 분포<그림2>에 따라 응력변화가 주로 발생하게 된다. 특히 토피고 0.6m∼1.6m인 구간에서 항공기 활하중이 민감하게 변화되고, 1.6m 이상인 경우부터 토피고와 거의 반비례하는 것을 볼 수 있다. 따라서 항공기 활하중이 재하되는 PC암거 시공현장에서 토피고가 0.6m에서 1.6m사이 변화되는 구간에 PC암거 단면을 시공할 경우에는 최대 토피고를 고려하여 설계하기보다는 항공기하중이 최대인 지점에서의 하중을 고려하여 단면을 설계하는 것이 적정할 것으로 판단된다.

The Kingery-Bulmash equation is the most common equation to calculate blast load. However, the Kingery-Bulmash equation is complicated. In this paper, a modified equation for surface blast load is proposed. The equation is based on Kingery-Bulmash equation. The proposed equation requires a brief calculation process, and the number of coefficients is reduced under 5. As a result, each parameter obtained by using the modified equation has less than 1% of error range comparing with the result by using Kingery-Bulmash equation. The modified equation may replace the original equation with brief process to calculate.

Recently, the trend is emerging a variety of irregular tall buildings. It is important to design the building for lateral load according to this trend. Fluid Structure Interaction(FSI) simulation can be performed to understand the vibrations of the structure against dynamic wind loads. In order to make the physical characteristics of the actual structure and the analytical model the same, we studied core inserting equivalent stiffness modeling method. As a result of this analysis, the stiffness of the structure can be set similar to that of the two axes of the structure, and turbulence can be reproduced through the acceleration tendency.

PURPOSES :The purpose of this study is to perform a reliability analysis of the proposed wind load combination which governs the design of support structures of subsidiary road facilities, and to evaluate whether the target reliability of the design is satisfied.METHODS :The statistical estimation method is applied and the design period of the support structure is used to obtain the statistical property of the wind load. In addition, the statistical properties of the strength of support structures are obtained from a literature review and simulation study. Actual support structures are designed by the proposed load combination and are used as the examples to examine if the target reliability is obtained.RESULTS :The result of the reliability analysis performed by using the statistical properties of load and resistance for the support structure in this study indicates that the proposed wind load combination satisfied the target reliability index of the design. Also, the convenience of the design is achieved by adopting the same design wind velocity given in the bridge design code by applying the wind velocity ratio defined for the design period of the support structure.CONCLUSIONS :It is presented that the design using the wind load combination proposed in this study achieved the target reliability index and the design wind load for different design periods can be conveniently defined by applying the velocity ratio proposed in this study.

To study the behavior of structures subject to blast loads it is important to calculate the loads due to the explosives accurately, especially in the case of interior explosions. It is known that numerical method based on computational fluid dynamics can estimate relatively accurate blast load due to the interior explosion including reflection effect. However, the numerical method has disadvantages that it is difficult to model the analysis and it takes much time to analyze it. Therefore, in this study, the analytical method which can include the reflection effect of the interior explosion was studied. The target structures were set as the slabs of residential buildings subject to interior explosion that could lead to massive casualties and progressive collapses. First, the numerical method is used to investigate the interior explosion effect and the maximum deflection of the slab which was assumed to be elastic, and compared with the analytical method proposed in this study. In the proposed analytical method, we determine the weighting factor of the reflection effect using the beam theory so that the explosion load calculation method becomes more accurate.

본 연구에서는 Karman이 제시한 풍방향 변동풍속 스펙트럼 및 Liang이 제시한 풍직각방향 변동풍하중 스펙트럼을 이용하여 풍방향 및 풍직각방향 풍하중을 생성하고, 생성된 풍하중을 적용하여 고정기초 및 면진기초 구조물의 동적 거동을 해석하여 풍하중이 작용하는 고정기초 구조물과 면진기초 구조물의 동적거동을 해석하여 면진기초에 의한 풍응답 증가에 대하여 비교분석하였다.

The demand for skyscrapers is increasing worldwide. Until now, various lateral resistance structures have been used for lateral displacement control of high-rise buildings. An outrigger damper system has been introduced recently to improve lateral dynamic response control performance further. However, a study of outrigger damper system is yet to be sufficiently investigated. In this study, time history analysis was performed to investigate the control performance of an outrigger damper system of high-rise building under eccentric loading. To do this, an actual scale 3-dimensional tall building model with an outrigger damper system was prepared. The control performance of the outrigger damper system was evaluated by varying stiffness and damping values. On the top floor torsional angle response to the earthquake load, was greatly affected by damping value. And the displacement response was affected greatly by the stiffness value and damping value of damper system. In conclusion, it is necessary to select the proper damping and stiffness values of the outrigger damper system.

A tensile failure criterion that can minimize the mesh-dependency of simulation results on the basis of the fracture energy concept is introduced, and conventional plasticity based damage models for concrete such as CSC model and HJC model, which are generally used for the blast analyses of concrete structures, are compared with orthotropic model in blast test to verify the proposed criterion. The numerical prediction of the time-displacement relations in mid span of the beam during blast loading are compared with experimental results. Analytical results show that the numerical error is substantially reduced and the accuracy of numerical results is improved by applying a unique failure strain value determined according to the proposed criterion.

Cylindrical steel shell sections have been applied in various engineering fields particularly in recent installations of wind turbine towers. Hence, many researchers are interested in studying cylindrical steel shell structures. However, studies on the effect of the presence or absence of openings are insufficient. Thus, the design criteria for the opening as well as the behavior of wind turbine tower are not clearly presented. Therefore, this study examines the ultimate strength and the behavior of wind tower in consideration of openings, presence of stiffeners, changes in opening width, and thickness variation of stiffeners. ABAQUS, a universal finite element analysis program, was used in to conduct this research. Finally, the results of this study can be a reference for the design and production of wind towers with openings.

In this study, load transfer tests based on KCI-PS101 were conducted to verify the performance of spiral anchorage zone reinforcement for banded post-tensioning (PT) monostrands. With results, the compressive strength of spiral reinforcement was increased by about 20% than that of specimens with two horizontal steel bars and 8% than that of U-shaped bars. Advanced spiral reinforcement for corner increases compressive strength and can resist the spalling forces or fall-out effect at the corner by shear. The ratio of maximum load to amount of steel of the spiral reinforcement is about twice than that of U-shaped reinforcement. With increase of compressive strength capacity and improvement of constructability, the spiral reinforcement is considered to have advantages of promoting the performance of PT anchorage zone compared to conventional methods.

The result of the previous work leads to the idea that the inner area of the hyperbolic shell generator should be minimized for the cooling tower with higher first natural frequency. In this study the inner area of the hyperbolic shell generator was graphically established under varying height of the throat and angle of the base lintel. From the graph, several shell geometries were selected and analysed in the aspect of the natural frequency. Three representative towers reinforced differently due to different first natural frequencies were analysed non-linearly and evaluated using a damage indicator based on the change of natural frequencies. The results demonstrated that the damage behaviour of the tower reinforced higher due to a lower first natural frequency was not necessarily advantageous than the others