• Journal of Korean Society of Steel Construction
• /
• v.21 no.6
• /
• pp.563-574
• /
• 2009

This paper briefly describes the fundamental strategies--path-tracing, pin-pointing, and path-switching--in the computational elastic bifurcation theory of geometrically non-linear single-load-parameter conservative elastic spatial structures. The stability points in the non-linear elasticity may be classified into limit points and bifurcation points. For the limit points, the path tracing scheme that successively computes the regular equilibrium points on the equilibrium path, and the pinpointing scheme that precisely locates the singular equilibrium points were sufficient for the computational stability analysis. For the bifurcation points, however, a specific procedure for path-switching was also necessary to detect the branching paths to be traced in the post-buckling region. After the introduction, a general theory of elastic stability based on the energy concept was given. Then path tracing, an indirect method of detecting multiple bifurcation points, and path switching strategies were described. Next, some numerical examples of bifurcation analysis were carried out for a trussed stardome, and a pin-supported plane circular arch was described. Finally, concluding remarks were given.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.22 no.4
• /
• pp.307-314
• /
• 2009

The present paper briefly describes the space frame element and the fundamental strategies in computational elastic bifurcation theory of geometrically nonlinear, single load parameter conservative elastic spatial structures. A method for large deformation(rotation) analysis of space frame is based on an eulerian formulation, which takes into consideration the effects of large joint translations and rotations with finite deformation(rotation). The local member force-deformation relationships are based on the beam-column approach, and the change in member chord lengths caused by axial strain and flexural bowing are taken into account. and the derived geometric stiffness matrix is unsymmetric because of the fact that finite rotations are not commutative under addition. To detect the singular point such as bifurcation point, an iterative pin-pointing algorithm is proposed. And the path switching mode for bifurcation path is based on the non-negative eigen-value and it's corresponding eigen-vector. Some numerical examples for bifurcation analysis are carried out for a plane frame, plane circular arch and space dome structures are described.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.4A
• /
• pp.315-327
• /
• 2009

In this study, the static test of CFT truss girders for different f/L ratios was conducted to determine how the ultimate strength of the CFT truss girder was affected by different f/L ratios. A total of two CFT truss girders were constructed and tested under bending condition. The length of all specimens is 20,000 mm. The CFT truss girder is a tubular truss composed of chord members made of concrete-filled circular tubes. The main parameter analyzed in the experimental study was the f/L ratio. This factor was experimentally investigated to assess their influence on ultimate strength and stiffness. The test results show that CFT truss girder has good elastic-plastic property and ductility. The presence of the f/L ratios in CFT truss girders alters its ultimate strength because of the global stiffness of the CFT truss girders. The ultimate strength of CFT truss girders increases as the f/L ratio increases. If the f/L ratio of the CFT truss girders increases twofold, the ultimate strengths increase by 80%. The CFT truss girders showed that they retained large deformation capacity, even after reaching the ultimate strength. Results of this investigation demonstrated the potential for efficiently using a CFT truss as a bridge girder.

• The korean journal of orthodontics
• /
• v.31 no.6 s.89
• /
• pp.559-566
• /
• 2001

This study was undertaken to demonstrate the forces in the mandibular alveolar bone generated by activation of the mandibular posterior crossbite appliance in the treatment of buccal crossbite caused by lingual eruption of mandibular second molar. A three-dimensional photoelastic model was fabricated using a photoelastic material (PL-3) to simulate alveolar bone. We observed the model from the anterior to the posterior view in a circular polariscope and recorded photogtaphically before and after activation of the mandibular posterior crossbite appliance. The following results were obtained : 1. When the traction force was applied on the buccal surface of the mandibular second molar, stress was concentrated at the lingual alveolar crest and root apex area. The axis of rotation also was at the middle third of the buccal toot surface and the root apex, so that uncontrolled tipping and a buccal traction force for the mandibular second molar were developed. 2. When the traction force was applied on the lingual surface of the mandibular second molar more stress was observed as opposed to those situations in which the force application was on the buccal surface. In addition, stress intensity was increased below the loot areas and the axis of rotation of the mandibular second molar was lost. In result, controlled tipping and intrusive tooth movements were developed. 3. When the traction forte was applied on either buccal or lingual surface of the second molar, the color patterns of the anchorage unit were similar to the initial color pattern of that before the force application. So we can use the lingual arch for effective anchorage in correcting the posterior buccal crossbite. As in above mentioned results, we must avoid the rotation and uncontrolled tipping, creating occlusal interference of the malpositioned mandibular second molar when correcting posterior buccal crossbite. For this purpose, we recommend the lingual traction force on the second molar as opposed to the buccal traction.