This paper dealt with the applicability of GFRP materials as reinforcements for a steel box girder bridge deck. The purpose of this study is to provide detailed design procedures with a code-based text for GFRP composites for civil engineering structures. From the example design, the deck was optimized from a serviceability perspective but was quite overdesigned with regard to flexural strength and creep rupture stress, due to its relatively low longitudinal modulus but high strength. We may conclude from these results that it is advisable to check the serviceability limits before optimizing the design for strength or starting the design from the serviceability calculation.

Bridge inspection structures are the structure which is installed on the piers, abutments, and copings for the inspection and maintenance of substructure. In this study, the structural performance of the bridge inspection structures using aluminum members manufactured by extrusion process is evaluated. The bridge inspection structures can be installed regardless of the shape of concrete surface through the simple cutting process. The structural performance of bridge inspection structures is evaluated using FE analysis. Moreover, experimental studies are conducted for the estimation of the structural safety of the members for the design load.

The proposed hybrid damper installs at a coupling beam and consists of a high-damping rubber (HDR) and steel pin. The proposed hybrid damper adopted a pin-lock system acts as a viscoelastic damper under wind load (small displacement) while it behaves as a hysteretic damper under earthquake load (large displacement). In this paper, the pin-lock mechanism and structural performance of the proposed hybrid damper is evaluated through experiment. Experiments were carried out with the variables which displacement, loading frequency and steel pin quantities were used. Test results showed that the pin-lock mechanism and the performance of the hybrid damper under a large displacement were verified. Also equivalent damping ratios of HDR were increasing at a small displacement as displacement amplitudes were increasing. However HDR did not depend on frequency,

Determining of the shape in the process of design for natural draught cooling tower is very important, because the shape of hyperbolic shell is respond sensitively to dynamic behavior of the whole cooling tower against wind load. In engineering practice, the geometric parameters have been determining based on the natural frequency. This study analyses influence of the tower shell geometric parameters on the structural behavior. For three representative models were selected, they were analyzed based on evaluation of damage by means of nonlinear FE-method. As a result, a hyperbolic rotational shell with the small radius overall was the lowest damage index induced by sufficient capacity of the stress redistribution and thus a wind-insensitive structure.

This study analyze the dynamic response property of latticed domes according to natural frequency ratio of substructure. Through eigenvalue analysis, it is was confirmed that the half-open angle 30° and 45° dominate vibration mode of the vertical direction and the half-open angle 60° and 90° dominate vibration mode of the horizontal direction. Through the dynamic response analysis, it is was confirmed that the first frequency about total structure largely appears about the vertical and the horizontal direction regardless of half-open angle.

Cable network system is a flexible lightweight structure which curved cables can transmit only tensile forces. The weight of cable roof dramatically can reduce when the length becomes large. The cable network system is too flexible, most cable systems are stabilized by pretension forces. The tensile force of cable system is greatly influenced by the sag ratio and pretension forces. Determining initial sag ratio of cable roof system is essential in a design process of cable structures. Final sag ratio and pretension depends on initial installed sag and on proper handling during installation. The design shape of cable system has an affect on the sag and pretension, and must be determined using well-defined design philosophy. This paper is carried out the comparative data of the deflection and tensile forces on the geometric non-linear analysis of cable network systems according to sag ratio. The study of cable network system is provided to technical informations for the design of a large span cable roof, analytical results are compared with the results of other researchers. Structural nonlinear analysis of systems having cable elements is relatively complex than other rigid structural systems because displacements are large as a reason of flexibility, initial prestress is applied to cables in order to increase the rigidity, and then divergence of nonlinear analysis occurs rather frequently. Therefore, cable network systems do not exhibit a typical nonlinear behavior, iterative method that can handle geometric nonlinearities are necessary.

The Eradi Quake System (EQS) is a seismic isolation bearing system designed to minimize forces and displacements experienced by structures subjected to ground motion. The EQS dissipates seismic energy through friction of Poly Tetra Fluoro Ethylene (PTFE) disk pad. In general, a force-displacement relationship of EQS has post yield stiffness hardening during large inelastic displacement. In this study, seismic responses of seismically isolated nuclear power plant (NPP) subjected to design basis earthquake (DBE) and beyond design basis earthquakes (150% DBE and 167% DBE) are compared considering the post yield stiffness hardening effect of EQS. From the results, it can be observed that if the post-yield stiffness hardening effect of EQS is increased, the displacement response of EQS is reduced, and the acceleration and shear responses of containment structures of NPP is increased.

In this study, Stockbridge damper was adopted to reduce the reponses of structures under earthquakes. A finite element analysis software, SAP2000, was used to simulate the structural response and the control device under dynamic loads. A 3 story frame model and the proposed control device, Stockbridge damper, were designed under laboratory conditions. In this research, a pendulum type tuned mass damper (PTMD) was also adopted in order to compare with the Stockbridge damper. Harmonic loads were applied to verity the control performance of both control devices in each mode. In results, it has been found that the Stockbirdge damper decreases significantly the responses of the structure more than the PTMD under the harmonic loadings. The El Centro and Northridge earthquakes were also applied in order to investigate the performance by both control devices. The responses of the building demonstrate that the Stockbridge damper reduces the response of the building structure during earthquakes more effectively than the PTMD.

Soil-foundation-structure interaction (SFSI) is one of the important issues in the seismic design for evaluating the exact behavior of the system. A seismic design of a structure can be more precise and economical, provided that the effect of SFSI is properly taken into account. In this study, a series of the dynamic centrifuge tests were performed to compare the seismic response of the single degree of freedom(SDOF) structure on the various types of the foundation. The shallow and pile foundations were made up of diverse mass and different conjunctive condition, respectively. The test specimen consisted of dry sand deposit, foundation, and SDOF structure in a centrifuge box. Several types of earthquake motions were sequentially applied to the test specimen from weak to strong intensity of them, which is known as a stage test. Results from the centrifuge tests showed that the seismic responses of the SDOF structure on the shallow foundation and disconnected pile foundation decreased by the foundation rocking. On the other hand, those on the connected pile foundation gradually increased with intensity of input motion. The allowable displacement of the foundation under the strong earthquake, the shallow and the disconnected pile foundation, have an advantage in dissipating the earthquake energy for the seismic design.

Unreinforced masonry (URM) buildings are known to be highly vulnerable to seismic loadings. Although significant physical variation may exist for URM buildings that fall into a same structural category, a single set of fragility curves is typically used as a representation of the seismic vulnerability of the URM structures. This study investigates the effect of physical variation of URM structures on their seismic performance level. Variables that describe the physical variation of the structure are defined based on the inventory analysis. Seismic behavior of the structures is then monitored by changing the variables to investigate the effect of each variable. The analysis results show that among the variables considered the seismic performance of URM building depends on the variation of the width, the aspect ratio, and the number of story. The need for further research on the modeling of the connections between the walls and diaphragms and the torsional effect is also addressed.

본 연구는 목포 유달산을 중심으로 한 인근 도서에 분포하는 왕자귀나무군락의 식생구조 및 입지환경 특성을 밝히고 자 실시되었다. 목포 유달산의 왕자귀나무군락(군락Ⅰ)은 상대적으로 해발고가 높은 곳에 위치했고, 주요 수종의 수령 은 30년 정도였다. 이 군락은 지속적인 교란으로 식생발달 초기단계의 식생구조를 보였다. 바닷가 인근 평지의 모래토양 에 형성된 군락 Ⅳ는 주요 수종의 수령이 9년 정도였다. 이 군락은 비교적 최근 인위적으로 교란된 곳에 열악한 환경에 적응력이 강한 왕자귀나무가 유입되어 순림을 형성한 것으로 추측된다. 그 외 군락(Ⅱ, Ⅲ)은 왕자귀나무와 낙엽성 참나무류가 서로 경쟁하는 식생상황을 보였으며, 주요 수종의 수령은 13∼30년이었다. 상대적으로 식생구조가 발달한 왕자귀나무군락일수록 바닷가 인근에 해발고가 높은 급경사에 위치했다. 식생발달 초기단계에는 임상으로 유입되는 광합성 유효광이 많아 관목층에 왕자귀나무의 치수발생 및 생장량이 높았다. 왕자귀 나무는 바닷가 훼손지나 척박한 토양에 적응력이 강해 이러한 곳에 출현할 가능성이 높았다. 하지만, 식생구조가 발달하 여 지력이 높을수록 낙엽성 참나무류와의 경쟁에 밀려 왕자귀나무의 세력이 약해졌다.

우리나라 도서지역 산림식생의 인간 간섭 유무와 정도에 따른 생태적 보전 및 관리를 위한 기초 정보를 수집하기 위하여 남해안 유인도서(대모도)와 무인도서(구도)를 대상으로 식물사회학적 연구방법으로 산림식생을 분류하고 그 구조 및 종조성 특성(총피도, 중요치, 종다양성, 지표종, 생활형 조성 등)을 파악하였다. 산림식생 유형은 대모도에서 총 11개 식생단위(1개 군락군, 2개 군락, 개 아군락, 9개 변군락, 그리고 4개 아변군락), 구도에서 총 8개 식생단위(2개 군락군, 5개 군락, 그리고 6개 아군락)가 구분되었다. 총피도(S)와 종다양도(H′)에 있어서 구도는 교목층이, 대모도는 관목층이 다른 층위에 비하여 상대적으로 아주 높게 나타났다. 생활형 조성 체계는 대모도 N-R5-D2-e, 구도 MM-R5-D2-e로 나타났다. 과중요치(FIV) 분석결과 대모도에서는 차나무과와 소나무과, 구도는 녹나무과와 참나무과 분류군들이 상위그룹을 이루고 있었으며, 과별 종구성비에 있어서는 대모도는 국화과가 4.5%(19종류), 구도는 백합과 가 7.3%(8종류)로 가장 높게 나타나 두 도서간 인위적 교란 정도를 가늠할 수 있었다. 지표종 분석에서는 대모도는 청미래덩굴, 광나무, 사스레피나무 등 미소지상식물(N)이, 구도는 황칠나무, 구실잣밤나무, 육박나무 등 대형지상식물 (MM)이 대개 유의한 지표종(p <0.0005)으로 나타났다.

본 연구는 물푸레나무과의 한국특산식물인 버들개회나무 자생지의 입지 환경과 생태적 특성을 알아보기 위하여 수행되었다. 버들개회나무 개체군은 주로 강원도의 계곡과 강변을 따라 분포하고 해발고는 121~520m의 높이에 위치하고 있다. 식생분석결과 4개 지역의 20개 방형구내에서 조사된 관속식물은 총 320분류군이었다. 버들개회나무 개체군은 광대싸리 우점개체군, 당단풍나무 우점개체군, 족제비싸리 우점개체군, 쉬땅나무 우점개체군으로 분류되었다. 토양의 이화학적 특성을 분석한 결과 유기물함량은 1.98~2.81%, 전질소함량 0.13~0.20 mg/kg, 치환성 K+는 0.10~0.33 cmol+/kg, Ca2+는 3.44~20.53 cmol+/kg, Mg2+는 0.34~0.95 cmol+/kg, 양이온치환용량 8.08~13.68 cmol+/kg이며, 토양 pH는 6.28~7.74인 것으로 조사되었다. 버들개회나무 개체군 내에서 중요치는 물참대 86.99%, 물푸레나무 43.97%, 박쥐나무 23.01%, 버들개회나무 18.52%, 가래나무 18.40%, 버드나무 11.56%로 나타났다. DCCA를 이용한 버들개회나무 개체군의 식생과 환경요인과의 상관분석 결과 해발고도와 Mg2+가 가장 큰 영향을 미치는 것으로 나타났으며, 광대싸리와 당단풍나무 우점개체군은 pH, CEC, Mg2+가 높은 지역에 분포하였고, 당단풍나무 우점개체군의 경우 광대싸리 우점개체군보다 K+가 높은 곳에 분포하였다. 족제비싸리 우점개체군은 해발고가 높고, 유효인산과 K+, 노암율이 높은 곳에 분포하는 것으로 나타났다.

Shelter that communication equipment and on-equipment material are mounted on is transported by airplane or vehicle, it has a function such as waterproof and shielding EMI. When the shelter is transported by car or helicopter, it is shocked by vibration and crash with the ground. So, three skids are attached to bottom of the shelter to reduce the shock. To confirm the durability of the structure of shelter, parallel drop and rotating drop test were done in accordance with KDS 0000-0000. However, the damage was discovered in the shelter. So, stiffening plate was added to skid and panel of partition wall to obtain durability and changed the shape of rubber buffer. In this paper, the cause of deformation and damage in the shelter was analyzed and improved shape through the structural analysis was verified.

The characteristics of stress distribution and fatigue life have been investigated in the road mower head system using FEM(Finite Element Method). There is high stress distribution around the coupling part with non-uniform load from the irregular road surface. Maximum equivalent stress especially occurs in the fixed plate and the pillar of the head device with maximum deformation at the rotation axis frame of the mower system. Fatigue life tests were also performed with SAE bracket history, SAE transmission, and sample history conditions. SAE bracket history and SAE transmission predicted the possibility of high damage while Sample history showed a stable trend. These results will be applicable in optimal design for various systems equipped with mower head system.

선박용 디젤엔진 배기가스에 포함된 입자상물질(PM) 가운데서 블랙카본(BC)은 극지방의 해빙을 촉진시키고 온난화를 유발하는 원인물질로서 큰 주목을 받고 있다. 본 연구에서는 향후 예상되는 PM/BC 배출 규제에 선제적으로 대응하고, 저감기술 개발 및 실증을 위한 기초연구의 일환으로 한국해양대학교 실습선 한바다호를 이용하여 실제 운항 중에 주기관의 배기관 수 포인트에서 PM을 샘플링하여 HR-TEM을 통해 그 구조와 특성을 분석하였다. 또한 배기가스 분석기를 이용하여 운전조건별 배기가스 내 유해물질의 배출 경향을 확인하였다. 분석 결과 엔진에서 배출된 PM의 구조는 구형 입자들의 촘촘하지 않은 체인형 결합으로 이루어져 있으며, 과급기로부터 멀어질수록 온도 저하에 의한 응집이 더 많이 관찰되었고 BC 특유의 graphitic 구조를 잃어가면서 점점 amorphous 구조를 띠는 경향이 나타났다. 또한 배기가스 분석을 통해 엔진 회전수가 증가할수록 배기 내 PM의 농도는 감소할 것으로 예측되었다.

CFRP hardened by carbon fiber and resin has the property of high strength and low weight. Specifically, the strong feature against the external vibration environment is shown as CFRP is designed with the structure of multi-axes. So, CFRP in place of metal has been used at the various fields. CFRP specimens for mode Ⅱ are applied with the repetitive fatigue load in this study. These specimens have the fiber layer angles of 30°, 45° and 60°. The material properties of specimens are investigated with the result of fatigue fracture due to this load. As the study result, the smallest and largest reaction forces of 500 N and 540 N are shown at the layer angle of 30° and 60° respectively among these specimens. The separation of adhesive interface at 4000 fatigue cycles is happened earliest in case of the layer angle of 60°. But the separation of adhesive interface at 11000 fatigue cycles is happened latest in case of the layer angle of 45°. Through the result of fatigue property, it is thought that the basis data can be applied to evaluate the safety at CFRP structure applied with fatigue.

In this study, we conducted an interrupted cutting SM20C with lathe and uncoated carbite tool, determined the relationship between Cutting Forces(principal, radial, feed force) by correlation analysis, and predicted the optimum cutting conditions by multiple regression analysis. The result were as follow. : From the correlation analysis, the increase of cutting speed and depth of cut reduces the principal force and radial force. the increase of cutting speed, depth of cut and feed rate will increase the feed force. From multi-regression analysis, we extracted regression equation and the coefficient of determination (R2) was 0.638, 0.692, 0.536 at principal, radial and feed force . It means that the regression equation is not high accuracy. However, it is predictable that the tendency of the forces action the interrupted cutting.