The hydro-forming design process of the sub-frame side members was studied using a high strength steel of 440 MPa in tensile strength. In the part design stage of the side member, the cross section analysis and the overall process design of the part shape were done. In the detailed simulation results, the maximum thickness reduction rate due to hydro-forming was predicted to be 13% and this was predicted to be a safe level without cracking. The end curvature was reduced to increase the stiffness of the part to design more secure parts and two types of grooves were added to the cross section and compared. The thickness reduction rates of the narrow and wide were improved by 18.6% and 15.6%, respectively when the narrow and wide grooves were added.

The stiffness of a bicycle frame is a major factor of a bicycle performance related to safety, stability, and weight. In this study, the torsional and bottom bracket stiffness of a bicycle frame were experimentally investigated. The torsional and bottom bracket stiffness for 63 bicycle frames were evaluated and analyzed by measuring the displacement of frames. The torsional stiffness is related with turning performance and the bottom bracket stiffness is related with power transmission. The experimental results show that the average stiffness varies up to 20 % according to the frame materials and types. The torsional stiffness has a strong corelation with the bottom bracket stiffness even though they have different effects on a bicycle frame. It seems that the experimental results can be applied to the quality criteria of racing bicycles and also design standard of a bicycle frame.

This paper investigates the characteristics of unstable behaviour and critical buckling load by joint rigidity of framed large spatial structures which are sensitive to initial conditions. To distinguish the stable from the unstable, a singular point on equilibrium path and a critical buckling level are computed by the eigenvalues and determinants of the tangential stiffness matrix. For the case study, a two-free node example and a folded plate typed long span example with 325 nodes are adopted, and these adopted examples' nonlinear analysis and unstable characteristics are analyzed. The numerical results in the case of the two-free node example indicate that as the influence of snap-through is bigger; that of bifurcation buckling is lower than that of the joint rigidity as the influence of snap-through is lower. Besides, when the rigidity decreases, the critical buckling load ratio increases. These results are similar to those of the folded-typed long span example. When the buckling load ratio is 0.6 or less, the rigidity greatly increases.

This study investigated characteristics of buckling load and effective buckling length by member rigidity of dome-typed space frame which was sensitive to initial conditions. A critical point and a buckling load were computed by analyzing the eigenvalues and determinants of the tangential stiffness matrix. The hexagonal pyramid model and star dome were selected for the case study in order to examine the nodal buckling and member buckling in accordance with member rigidity. From the numerical results, an effective buckling length factor of adopted models was bigger than that of Euler buckling for the case of fixed boundary. These numerical models indicated that the influence of nodal buckling was greater than that of member buckling as member rigidity was higher. Besides, there was a tendency that the bifurcation appeared on the equilibrium path before limit point in the member buckling model.

In case of rectangular lattice dome which shearing rigidity is very small, it has a concern to drop Buckling strength considerably by external force. So, by means of system to increase buckling-strength, there is a method of construction that lattice of dome is one with roof material. In a case like this, shearing rigidity of roof material increases buckling-strength of the whole of structure and can be designed economically from the viewpoint of practice. In case of analysis is achieved considering roof material that adheres to lattice of dame, there is method that considers the rigidity that use effective width frame as method to evaluate rigidity of roof material. therefore, this study is aimed at deciding effective width of roof material united with rectangular lattice dome to evaluate rigidity of roof material by effective width of frame and investigating how much does rigidity of roof material united with lattice of dome increase buckling-strength of the whole of structure according to rise-ratio. Conditions of loading are vertical-type-uniform loading. Analysis method is based on FEM dealing with the geometrically nonlinear deflection problems.

This study investigated characteristics of buckling load and effective buckling length by member rigidity of dome-typed space frame which was sensitive to initial conditions. A critical point and a buckling load were computed by analyzing the eigenvalues and determinants of the tangential stiffness matrix. The hexagonal pyramid model and star dome were selected for the case study in order to examine the nodal buckling and member buckling in accordance with member rigidity.

컨테이너 무역 규모가 매년 증가함에 따라 항만 환경이 급격히 변화하고 있다. 이러한 항만의 변화에 성공적으로 대처하기 위해 차세대 항만하역시스템인 LMTT(Linear Motor-based Transfer Technology)의 연구가 진행되고 있다. LMTT용 셔틀 카의 프레임부는 내부 빔, 내부 빔, 크로스 빔으로 구성되어 있으며, 본 연구에서는 프레임을 설계하기 위하여 크로스 빔의 개수, 하중 재하 위치 및 내부 빔의 위치에 따른 외부 빔과의 거리비 등이 프레임의 강도 및 강성에 미치는 영향을 유한요소 해석을 통하여 하중이 외부 빔과 내부 빔에 동시에 작용하고 크로스 빔이 5개일 때가 최적의 조건이라는 결론을 얻을 수 있었다.