• Structural Engineering and Mechanics
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• v.84 no.3
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• pp.423-435
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• 2022

In this article, we present torsion-bending analysis of a composite FGM beam with an open section, according to the advanced and refined theory of 1D / 3D beams based on the 3D Saint-Venant's solution and taking into account the edge effects. The (initially one-dimensional) model contains a set of three-dimensional (3D) displacement modes of the cross section, reflecting its 3D mechanical behaviour. The modes are taken into account depending on the mechanical characteristics and the geometrical form of the cross-section of the composite FGM beam. The model considered is implemented on the CSB (Cross-Section and Beam Analysis) software package. It is based on the RBT/SV theory (Refined Beam Theory on Saint-Venant principle) of FGM beams. The mechanical and physical characteristics of the FGM beam continuously vary, depending on a power-law distribution, across the thickness of the beam. We compare the numerical results obtained by the three-beam theories, namely: The Classical Beam Theory of Saint-Venant (Classical Beam Theory CBT), the theory of refined beams (Refined Beam Theory RBT), and the theory of refined beams, using the higher (high) modes of distortion of the cross-section (Refined Beam Theory using distorted modes RBTd). The results obtained confirm a clear difference between those obtained by the three models at the level of the supports. Further from the support, the results of RBT and RBTd are of the same order, whereas those of CBT remains far from those of higher-order theories. The 3D stresses, strains and displacements, obtained by the present study, reflect the 3D behaviour of FGM beams well, despite the initially 1D nature of the problem. A validation example also shows a very good agreement of the proposed models with other models (classical or higher-order beam theory) and Carrera Unified Formulation 1D-beam model with Lagrange Expansion functions (CUF-LE).

• Advances in aircraft and spacecraft science
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• v.1 no.3
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• pp.253-271
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• 2014

A linearised buckling analysis of thin-walled beams is addressed in this paper. Beam theories formulated according to a unified approach are presented. The displacement unknown variables on the cross-section of the beam are approximated via Mac Laurin's polynomials. The governing differential equations and the boundary conditions are derived in terms of a fundamental nucleo that does not depend upon the expansion order. Classical beam theories such as Euler-Bernoulli's and Timoshenko's can be retrieved as particular cases. Slender and deep beams are investigated. Flexural, torsional and mixed buckling modes are considered. Results are assessed toward three-dimensional finite element solutions. The numerical investigations show that classical and lower-order theories are accurate for flexural buckling modes of slender beams only. When deep beams or torsional buckling modes are considered, higher-order theories are required.

• Steel and Composite Structures
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• v.27 no.1
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• pp.1-12
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• 2018

This paper presents a semi-analytical solution of simply supported horizontally composite curved I-beam by trigonometric series. The flexibility of the interlayer connectors between layers both in the tangential direction and in the radial direction is taken into account in the proposed formulation. The governing differential equations and the boundary conditions are established by applying the variational approach, which are solved by applying the Fourier series expansion method. The accuracy and efficiency of the proposed formulation are validated by comparing its results with both experimental results reported in the literature and FEM results.

• Journal of the Korea Concrete Institute
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• v.11 no.5
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• pp.11-20
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• 1999

This paper deals with behaviors of PSC-Beam bridges according to continuity of spans. To analyze the long-term behavior of bridges, an analytical model which can simulate the effects of creep, the shrinkage of concrete, and the cracking of concrete slabs in the negative moment regions is introduced. To consider the different material properties across the sectional depth, the layer approach in which a section is divided into imaginary concrete and steel layers is adopted. The element stiffness matrix is constructed according to the assumed displacement field formulation, and the creep and shrinkage effects of concrete are considered in accordance with the first-order algorithm based on the expansion of the creep compliance. Correlation studies between analytical and experimental results are conducted with the objective to establish the validity of the proposed model. Besides, many uncertainties related to the continuity of spans are analyzed to minimize deck cracking at interior supports.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.3
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• pp.396-406
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• 2014

Shrimp beam trawl fishery is one of the important coastal fisheries in Korea. It has a regulation to the length of beam (8m) and wing net (7m) of shrimp beam trawl that has been used in the district of Junlanam-do and Gyungsangnam-do. This regulation was made in relation to the size of shrimp beam trawler of 3-ton class at that time. Now the shrimp beam fishing vessel has a limit not greater than 5 tons in gross ton. Recently, with improvement of fishing industry and fishing vessel fishermen asked the expansion of the length of beam and wing net, therefore it is necessary to investigate the effect of lengthening the beam and wing net length. Three different beams (8m, 10m and 12m in length) and three different wing net (7m, 10m and 13m in length) were made and the experiment was conducted near Narodo of Goheng by two fishing vessels of 4.98 and 4.88 tons in gross ton between June 2011 and October 2012. When the length of wing net was increased from 7m to 10m and 13m, the relative catch ratio in total biomass was increased 25% and 79% for shrimp, (17% and 22% in total), respectively. And when the beam length was increased from 8m to 10m and 12m, the relative catch ratio was increased 35% and 84% for shrimp, (21% and 37% in total), respectively. The force exerted to the iron guide of inhauler's with the beam length of 8m was about 30% greater than that with the beam length of 10m when hauling the shrimp beam trawl net.

• Structural Engineering and Mechanics
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• v.63 no.6
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• pp.713-723
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• 2017

As a new type of ballastless track, longitudinal continuous slab track (CST) has been widely used in China. It can partly isolate the interaction between the ballastless track and the bridge and thus the rail expansion device would be unnecessary. Compared with the traditional track, CST is composed of multi layers of continuous structures and various connecting components. In order to investigate the performance of CST on a long-span bridge, the spatial finite element model considering each layer of the CST structure, connecting components, bridge, and subgrade is established and verified according to the theory of beam-rail interaction. The nonlinear resistance of materials between multilayer track structures is measured by experiments, while the temperature gradients of the bridge and CST are based on the long-term measured data. This study compares the force distribution rules of ballasted track and CST as respectively applied to a long span bridge. The effects of different damage conditions on CST structures are also discussed. The results show that the additional rail stress is small and the CST structure has a high safety factor under the measured temperature load. The rail expansion device can be cancelled when CST is adopted on the long span bridge. Beam end rotation caused by temperature gradient and vertical load will have a significant effect on the rail stress of CST. The additional flexure stress should be considered with the additional expansion stress simultaneously when the rail stress of CST requires to be checked. Both the maximum sliding friction coefficient of sliding layer and cracking condition of concrete plate should be considered to decide the arrangement of connecting components and the ultimate expansion span of the bridge when adopting CST.

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.783-792
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• 2006

This study investigates developments in a prestressing method using the thermal-expanded cover-plates that increases the load-carrying capacity of structures by installing it on upper or lower flanges in case that huge flexural stiffness according to the increase in span length or load are required of steel structure, such as rolled H-beam or built-up beam. This method applies multi-stepwise contraction forces generated by the contraction of cover plates as prestressing forces after joining the cover plate applied by multi-stepwise thermal expansion that was applied to induce prestressing to structures. To perform a theoretical investigation of the prestressing force applied to a structure due to the thermal expansion and induce a multi-stepwise prestressing method using multi-stepwise thermal distribution, this study proposes a theoretical heat transfer solution for the multi-stepwise thermal distribution of cover plates and analyzes the effect of a multi-stepwise prestressing method using the multi-stepwise thermal expansion.

• The korean journal of orthodontics
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• v.53 no.5
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• pp.289-297
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• 2023

Objective: To analyze the microimplant (MI) displacement pattern on treatment with a maxillary skeletal expander (MSE) using cone-beam computed tomography (CBCT). Methods: Thirty-nine participants (12 males and 27 females; mean age, 18.2 ± 4.2 years) were treated successfully with the MSE II appliance. Their pre- and post-expansion CBCT data were superimposed. The pre- and post-expansion anterior and posterior inter-MI angles, neck and apical inter-MI distance, plate angle, palatal bone thickness at the MI positions, and suture opening at the MI positions were measured and compared. Results: The jackscrew plate was slightly bent in both anterior and posterior areas. There was no significant difference in the extent of suture opening between the anterior and posterior MIs (P > 0.05). The posterior MI to hemiplate line was greater than that anteriorly (P < 0.05). The apical distance between the posterior MIs was greater than that anteriorly (P < 0.05). The palatal thickness at the anterior MIs was significantly greater than that posteriorly (P > 0.01). Conclusions: In the coronal plane, the angulation between the anterior MIs in relation to the jackscrew plate was greater than that between the posterior MIs owing to the differential palatal bone thickness.

• Composites Research
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• v.25 no.1
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• pp.26-30
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• 2012

This study was focused on the measurement of thermal expansion coefficients for GRP pipe through strain gage circuits. First of all, thermal expansion coefficients of aluminum beam were measured to examine the validity of the suggested method by using various types of strain gage circuits. Thermal expansion coefficients of GRP pipes along axial and hoop directions were measured to investigate the effect of the location of strain gages, number of repeated measurements, and strain gage types with different thermal expansion coefficients on the thermal strains and the repeatability of measured results. According to the results, thermal expansion coefficients of GRP pipes along hoop direction were lower than those along axial direction due to the constraint effect of reinforced glass fibers on thermal strains along hoop direction. As measurements were repeated, thermal expansion coefficients of GRP pipes were slightly increased, but the degree of increase became smaller. Finally, the same thermal expansion coefficients were obtained irrespective of different types of strain gages with different thermal expansion coefficients if thermal strains of strain gages were compensated by using reference compensation specimen.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.1
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• pp.175-182
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• 2005

A laser beam expanding technique is employed to fabricate precise nano-patterns in a nano-replication printing (nRP) process. In the nRP process, some patterns can be fabricated in the range of several microns inside on a polymerizable resin by using a volume-pixel (voxel) matrix that is transformed from a two-tone bitmap figure file. The liquid monomers are polymerized by means of a two-photon-absorption (TPA) phenomenon that is induced by a femtosecond (fs)-pulse laser. The yokels are generated consecutively to merge into adjoining yokels in the process of fabricating a pattern. The resolution of a fabricated pattern can be obtained under the diffraction limit of a laser beam by the two-photon absorbed polymerization (TPP). In this work, a beam-expanding technique has been applied to enlarge a working area and to fabricate precise patterns. Through this work, a working area is expanded by the technique as much as 2.5 times compared with a case of without a beam expanding technique, and precision of outside patterns is improved.