• The Journal of Advanced Prosthodontics
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• v.9 no.2
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• pp.124-129
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• 2017

PURPOSE. This study evaluated the effect of span length on the adaptation of implant-supported cobalt chromium frameworks fabricated by three techniques. MATERIALS AND METHODS. Models with two solid abutment analogs at different inter-abutment distances were digitized using a laboratory scanner. Frameworks of two-, three-, and four-unit fixed prostheses were designed by a computer. Six dots with a diameter of 0.2 mm were preset on the surface of each framework. A total of 54 implant-supported cobalt chromium frameworks were fabricated by milling, selective laser melting (SLM), and cast techniques. The frameworks were scanned and exported as Stereolithography files. Distances between two dots in X, Y, and Z coordinates were measured in both the designed and fabricated frameworks. Marginal gaps between the framework and the abutments were also evaluated by impression replica method. RESULTS. In terms of distance measurement, significant differences were found between three- and four-unit frameworks, as well as between two- and four-unit frameworks prepared by milling technique (P<.05). Significant differences were also noted between two- and three-unit frameworks, as well as between two- and four-unit frameworks prepared by cast technique (P<.05). The milling technique presented smaller differences than the SLM technique, and the SLM technique showed smaller differences than the cast technique at any unit prostheses (P<.05). Evaluation with the impression replica method indicated significant differences among the span lengths for any fabrication method (P<.05), as well as among the fabrication methods at any unit prostheses (P<.05). CONCLUSION. The adaptation of implant-supported cobalt chromium frameworks was affected by the span length and fabrication method.

• Korean Journal of Agricultural Science
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• v.38 no.3
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• pp.505-512
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• 2011

Structural characteristics for standard models of single-span plastic greenhouse in Korea and high tunnels in North America were analyzed, and comparative analysis for greenhouse environments measuring in Korean farmhouse and Rutgers high tunnel was carried out to find structural and environmental improvements of single-span plastic greenhouses that occupy most of Korean greenhouse. Widths of high tunnels are similar to single-span plastic greenhouses but their heights are high comparatively and their side heights are fairly higher than single-span plastic greenhouses specially. Rafters, which are main frames, section sizes of high tunnels are bigger and their intervals are wider than single-span plastic greenhouses. Relative bending resistances compared with representative Korean greenhouse were analyzed by 0.92 to 1.42 in single-span plastic greenhouses, and 1.38 to 2.96 in high tunnels. Frame ratios of single-span plastic greenhouses were 6.8 to 8.6%, and those of high tunnels were 5.5 to 8.7%. We analyzed air temperatures and solar radiations measured in single-span plastic greenhouse and high tunnel on clear days in late March. There were outside temperatures in generally similar range, and judging by rise of indoor temperatures, ventilation performance of high tunnel is more excellent than single-span plastic greenhouse. Solar radiations of two areas were no big difference but light transmittance of high tunnel was a little bit higher than single-span plastic greenhouse. Single-span plastic greenhouses are disadvantageous in environmental managements such as ventilation performance and light transmittance because distance between greenhouses is too narrow and length of greenhouse is too long compared to high tunnels. To get the environmental improvement effects as well as to increase the structural resistance of single-span plastic greenhouses are achievable by widening the width of greenhouse in possible range, widening the space between rafters, and enlarging the section size of rafters. Also, we need to secure enough distance between greenhouses and to restrict the length of greenhouse by maximum 50 m in order to improve the ventilation performance and the light transmittance.

• Coupled systems mechanics
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• v.9 no.4
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• pp.311-323
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• 2020

This paper deals with the effect of the mode shapes on the dynamic response of a multi-storey frame subjected to moving train loads which are modelled as loads of constant intervals with constant velocity using the finite element method. The multi-storey frame is modelled as a number of Bernoulli-Euler beam elements. First, the first few modes of the multi-storey frame are determined. Then, the effects of force span length to beam length ratio and velocity on dynamic magnification factor (DMF) are evaluated via 3D velocity-force span length to beam length ratio-DMF graphics and its 2D projections. By using 3D and 2D graphics, the directions of critical speeds that force the structure under resonance conditions are determined. Last, the mode shapes related to these directions are determined by the time history and frequency response graphs. This study has been limited by the vibration of the frame in the vertical direction.

• Structural Engineering and Mechanics
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• v.13 no.6
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• pp.713-730
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• 2002

This paper presents a finite element approach for determining the natural frequencies for planar inclined arches of various shapes vibrating in three-dimensional space. The profile of inclined arches, represented by undeformed centriodal axis of cross-section, is defined by the equation of plane curves expressed in the rectangular coordinates which are : circular, parabolic, sine, elliptic, and catenary shapes. In free vibration state, the arch is slightly displaced from its undeformed position. The linear relationship between curvature-torsion and axial strain is expressed in terms of the displacements in three-dimensional space. The finite element discretization along the span length is used rather than the total are length. Numerical results for arches of various shapes are given and they are in good agreement with those reported in literature. The natural frequency parameters and mode shapes are reported as functions of two nondimensional parameters: the span to cord length ratio (e) and the rise to cord length ratio (f).

• Structural Engineering and Mechanics
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• v.74 no.2
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• pp.215-225
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• 2020

Thin films easily wrinkle under compressive loading due to their small bending stiffness resulting from their tiny thickness. For a thin film deposited on a functionally graded substrate with non-uniform stiffness exponentially changes along the length span in this paper, the uniaxial wrinkling problem is solved analytically in terms of hyper-Bessel functions. For infinite, semi-infinite and finite length systems the wrinkling load and wrinkling wavenumber are determined and compared with those in literature. In comparison with a homogeneous substrate-bounded film in which the wrinkling pattern is uniform along the length span, for a functionally graded substrate-film system the wrinkles accumulate around the softer location of the functionally graded substrate. Therefore, the effective length of the film influenced by the wrinkles decreases, the amplitude of the wrinkles on softer regions of the functionally graded substrate grows and the wrinkling load of the functionally graded substrates with higher softening rate decreases more. The results of the current research are expected to be useful in science and technology of thin films and wrinkling of the structures especially living tissues.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.04a
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• pp.139-146
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• 1997

The main purpose of this paper is to investigate the near-optimal parameters of continuous beam subject to a moving load. The computer-aided optimization technique is used to obtain the near-optimal parameters. The computer program is developed to obtain the natural frequency parameters and the forced vibration responses to a transit point load for the continuous beam with variable support spacing, mass and stiffness. The optimization function to describe the design efficiency is defined as a linear combination of four dimensionless span characteristics: the maximum dynamic stress; the stress difference between span segments; the rms deflection under the transit point load; and the total span mass. Studies of three span beams show that the beam with near-optimal parameters can improve design efficiency by 12 to 24 percent when compared to a reference configuration beams of the same total span length.

• Structural Engineering and Mechanics
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• v.55 no.6
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• pp.1203-1221
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• 2015

By taking a cable-stayed-suspension hybrid bridge with main span of 1400 m as example, seismic response of the bridge under the horizontal and vertical seismic excitations is investigated numerically by response spectrum analysis and time history analysis, its seismic performance is discussed and compared to the cable-stayed bridge and suspension bridge with the same main span, and considering the aspect of seismic performance, the feasibility of using cable-stayed-suspension hybrid bridge in super long-span bridges is discussed. Under the horizontal seismic action, the effects of structural design parameters including the cable sag to span ratio, the suspension to span ratio, the side span length, the subsidiary piers in side spans, the girder supporting system and the deck form etc on the seismic performance of the bridge are investigated by response spectrum analysis, and the favorable values of these design parameters are proposed.

• Journal of the Earthquake Engineering Society of Korea
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• v.18 no.4
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• pp.171-180
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• 2014

Since the execution of structural design by professional structural engineers is not mandatory for small-size buildings in Korea, structural design is conducted by architects or contractors resulting in concern about the seismic safety of the buildings. Therefore, the Korean Structural Engineers Association proposed dedicated structural design criteria in 2012. The criteria were developed based on a deterministic approach in which the structural members are designed only with information of story and span length of the buildings and without structural analyses. However, due to the short time devoted to their development, these criteria miss satisfactory basis and do not deal with structural walls popularly used in Korea. Accordingly, the Ministry of Land, Infrastructure and Transport launched a research on the 'development of structural performance enhancement technologies for small-size buildings against earthquakes and climate changes'.. As part of this research, this paper intends to establish direction for the preparation of deterministic structural design guidelines for seismic safety of domestic small-size reinforced concrete buildings. To that goal, a typical plan of these buildings is selected considering frames only and frames plus walls, and then design is conducted by changing the number of stories and span length. Next, the seismic performance is analyzed by nonlinear static pushover analysis. The results show that the structural design guidelines should be developed by classifying frames only and frames plus walls. The size and reinforcement of structural elements should be provided in the middle level of the current Korean Building Code and criteria for small buildings by considering story and span length for buildings with frames only, and determined by considering the shape and location of walls and the story and span length as well for buildings with frames plus walls. It is recommended that the design of walls should be conducted by reducing the amount of walls along with symmetrically located walls.

• Proceedings of the KSR Conference
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• 2001.10a
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• pp.293-298
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• 2001

2span continuous Prestressed concrete girder railway bridges, span length 21m, 25m, 30m, 35m, that down-up method is applied and that designed to satisfy service load in accordance with design criteria of railway bridge can be dropped in their hight compared with existing simply supported prestressed concrete girder railway bridges. Continuous bridges result in guaranteeing safety against bending behavior by loading the practical railway moving load with each velocity. But the natural frequency of span length 21m is estimated not to satisfy recommended limitation of UIC 776-1R..

• Steel and Composite Structures
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• v.11 no.3
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• pp.233-250
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• 2011

An experimental study has been carried out to reveal the shear-bond failure mechanism of composite deck slabs. Thirteen full scale simply supported composite slabs are studied experimentally, with the influence parameters like span length, slab depth, shear span length and end anchorage provided by steel headed studs. A dozen of strain gauges and LVDTs are monitored to capture the strain distribution and variation of the composite slabs. Before the onset of shear-bond slip, the longitudinal shear forces along the span are deduced and found to be proportional to the vertical shear force in terms of the shear-bond strength in the m-k method. The test results are appraised using the current design procedures. Based on the partial shear-bond connection at the ultimate state, an improved method is proposed by introducing two reduction factors to assess the moment resistance of a composite deck slab. The new method has been validated and the results predicted by the revised method agree well with the test results.