• Structural Engineering and Mechanics
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• v.71 no.5
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• pp.577-601
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• 2019

The paper investigates the influence of the rheological parameters which characterize the creep time, the long-term values of the mechanical properties of viscoelastic materials and a form of the creep function around the initial state of a deformation of the materials of the hollow bi-layered cylinder on the dispersion of the flexural waves propagated in this cylinder. Constitutive relations for the cylinder's materials are given through the fractional exponential operators by Rabotnov. The dispersive attenuation case is considered and numerical results related to the dispersion curves are presented and discussed for the first and second modes under the first harmonic in the circumferential direction. According to these results, it is established that the viscosity of the materials of the constituents causes a decrease in the flexural wave propagation velocity in the bi-layered cylinder under consideration. At the same time, the character of the influence of the rheological parameters, as well as other problem parameters such as the thickness-radius ratio and the elastic modulus ratio of the layers' materials on the dispersion curves, are established.

• Earthquakes and Structures
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• v.16 no.5
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• pp.589-599
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• 2019

Conventional buckling restrained braces used in concentrically braced frames are expected to yield in both tension and compression without major degradation of capacity under severe seismic ground motions. One of the weakness points of a standard buckling restrained braced frame is the low post-yield stiffness and thus large residual deformation under moderate to severe ground motions. This phenomenon can be attributed to low post-yield stiffness of core member in a BRB. This paper introduces a multi-core buckling restrained brace. The multi-core term arises from the use of more than one core component with different steel materials, including high-performance steel (HPS-70W) and stainless steel (304L) with high strain hardening properties. Nonlinear dynamic time history analyses were conducted on variety of diagonally braced frames with different heights, in order to compare the seismic performance of regular and multi-core buckling restrained braced frames. The results exhibited that the proposed multi-core buckling restrained braces reduce inter-story and especially residual drift demands in BRBFs. In addition, the results of seismic fragility analysis designated that the probability of exceedance of residual drifts in multi-core buckling restrained braced frames is significantly lower in comparison to standard BRBFs.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.552-568
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• 2020

After long-term service in deep ocean, pipelines are usually suffered from corrosions, which may greatly influence the Vortex-Induced Vibration (VIV) behavior of pipes. Thus, we investigate the VIV of defective pipelines. The geometric nonlinearity due to large deformation of pipes and nonlinearity in vortex-induced force are simulated. This nonlinear vibration system is simulated with finite element method and solved by direct integration method with incremental algorithm. Two kinds of defects, corrosion pits and volumetric flaws, and their effects of depth and range on VIV responses are investigated. A new finite element is developed to simulate corrosion pits. Defects are found to aggravate VIV displacement response only if environmental flow rate is less than resonance flow rate. As the defect depth grows, the stress responses increase, however, the increase of the defect range reduces the stress response at corroded part. The volumetric flaws affect VIV response stronger than the corrosion pits.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.6_3
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• pp.1165-1171
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• 2022

In this paper, the results of an experimental study were presented by measuring and comparing the flexural strength and deformation on the carbon fiber sheet strength reinforced concrete beam considering end anchorage effect. For this purpose, total six specimens of 100×100×600mm size were prepared and tested according to the KDS 14 20 20. The specimens were categorized in three cases as reference beams without strengthening, beams carbon fiber strengthened but not anchored and beams carbon fiber strengthened also anchored. Experimental results showed that the end anchorage contributed to increase the flexural strength about 42% greater than that of carbon fiber sheets alone, and the number and width of cracks were relatively increased. The results support a considerable effects of end anchorage for carbon fiber strengthened reinforced concrete beams in enhancing the flexural performance. Further studies are needed in durability and long term behavior of carbon fiber sheet strengthened reinforced concrete beams.

• The korean journal of orthodontics
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• v.52 no.6
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• pp.451-460
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• 2022

Moebius syndrome (MBS) is a congenital neurologic disorder that causes cranio-facial abnormalities. It involves paralysis of the VI and VII cranial nerves and causes bilateral or unilateral facial paralysis, eye movement disorder, and deformation of the upper and lower limbs. The orofacial dysfunctions include microstomia, micrognathia, hypotonic mimetic and lip muscles, dental enamel hypoplasia, tongue deformity, open bite or deep overbite, maxillary hypoplasia, high arched palate, mandibular hyperplasia or features indicating mandibular hypoplasia. This case report presents a 7-year-old male patient who was diagnosed with MBS at the age 2 years. The patient displayed typical clinical symptoms and was diagnosed with Class II malocclusion with a large overjet/overbite, tongue deformity and motion limitation, and lip closure incompetency. Treatment was initiated using a removable appliance for left scissor bite correction. After permanent tooth eruption, fixed appliance treatment was performed for correction of the arch width discrepancy and deep overbite. A self-ligation system and wide-width arch form wire were used during the treatment to expand the arch width. After 30 months of phase II treatment, the alignment of the dental arch and stable molar occlusion was achieved. Function and occlusion remained stable with a Class I canine and molar relationship, and a normal overjet/overbite was maintained after 9.4 years of retainer use. In MBS patients, it is important to achieve an accurate early diagnosis, and implement a multidisciplinary treatment approach and long-term retention and follow-up.

• Structural Engineering and Mechanics
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• v.85 no.6
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• pp.729-742
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• 2023

It is a recent attraction to the mechanical scientists to investigate state of wave propagation, buckling and vibration in the sport balls to observe the importance of different parameters on the performance of the players and the quality of game. Therefore, in the present study, we aim to investigate the wave propagation in handball game ball in term of mass of the ball and geometrical parameters wit incorporation of the viscoelastic effects of the ball material into account. In this regard, the ball is modeled using thick shell structure and classical elasticity models is utilized to obtain the equation of motion via Hamilton's principle. The displacement field of the ball model is obtained using first order shear deformation theory. The resultant equations are solved with the aid of generalized differential quadrature method. The results show that mass of the ball and viscoelastic coefficient have considerable influence on the state of wave propagation in the ball shell structure.

• Geomechanics and Engineering
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• v.31 no.5
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• pp.489-503
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• 2022

A 1257-m-long irregular deep foundation pit located in the central of Nanjing, China was constructed using the combined full-width and half-width top-down method. Based on the long-term field monitoring data, this study analyzed the evolution characteristics of the vertical movement of the columns, internal force of the struts, and axial force of the structural beam and slab. The relevance of the three mentioned above and their relationship with the excavation process, structural system, and geological conditions were also investigated. The results showed that the column uplift was within the range of 0.08% to 0.22% of the excavation depth, and the embedded depth ratio of the diaphragm wall and the bottom heave affected significantly on the column uplift. The differential settlement between the column and diaphragm wall remained unchanged after the base slab was cast. The final settlement of the diaphragm wall was twice the column uplift. The internal force of the struts did not varied monotonically but was related to numerous factors such as the excavation depth, number of struts, and environmental conditions. Additionally, the dynamic force and deformation of the columns, beams, and slabs were analyzed to investigate the inherent relationship and variation patterns of the responses of different parts of the structure.

• Geomechanics and Engineering
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• v.33 no.6
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• pp.529-542
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• 2023

Wave propagation with high transverse deflection could affect the stability of the ball in its trajectory. For low stiffness balls similar to soccer and volleyball balls, the waves are more noticeable in comparison to other balls like ping-pong ball. On the other hand, the soccer balls are under heavy impact loads from shoots and contacting different objects in the field. The maximum recorded speed of a soccer ball after kicking is the 211 km/hr and the average maximum speed is around 112 km/hr. Therefore, in such speeds the aerodynamic forces become important which are directly related to geometrical shape of the ball. In this regard, the wave propagation in soccer ball is examined in the current study using large deformation shear deformable formulations. Classical relations of stress-strain components are taken into consideration along with minimum total energy principle. The final derived relations were solved by using harmonic differential quadrature method. The results are generally presented ion term of phase velocity as function of different influencing parameters of the materials, geometry and mass of the ball.

• Steel and Composite Structures
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• v.46 no.6
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• pp.805-821
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• 2023

This study developed an evaluation system to explore the effect of the environmental temperature on the stress redistribution produced by cable stress relaxation of structural members in a steel cable-stayed bridge. The generalized Maxwell model is used to estimate stress relaxation at different temperatures. The environmental temperature is represented using the thermal coefficients and temperature loads. The fmincon optimization function is used to determine the set of stress relaxation parameters at different temperatures for all cables. The ABAQUS software is employed to investigate the stress redistribution of the steel cable-stayed bridge caused by the cable stress relaxation and the environmental temperature. All of these steps are set up as an evaluation system to save time and ensure the accuracy of the study results. The developed evaluation system is then employed to investigate the effect of environmental temperature and cable type on stress redistribution. These studies' findings show that as environmental temperatures increased up to 40 ℃, the redistribution rate increased by up to 34.9% in some girders. The results also show that the cable type with low relaxation rates should be used in high environmental temperature areas to minimize the effect of cable stress relaxation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1D
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• pp.53-60
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• 2010

The objective of this paper is to evaluate a performance-based load zoning procedure in flexible pavements. Long-term performance in flexible pavements will be evaluated using VESYS type rutting model and Miner s theory on fatigue cracking. Permanent deformation properties such as alpha and gnu, and fatigue cracking properties such as k1 and k2 in asphalt concrete were used respectively. The data from the literatures were also used in predicting performance in flexible pavements for evaluating load restrictions as well as parametric study. Finally, a performance-based load zoning procedure and a simple load limit procedure for load zoning were assessed.