• Structural Engineering and Mechanics
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• v.68 no.6
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• pp.701-711
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• 2018

Herein, the thermo-magneto-elastic wave dispersion answers of functionally graded (FG) double-nanobeam systems (DNBSs) are surveyed implementing a nonlocal strain gradient theory (NSGT). The kinematic relations are derived employing the classical beam theory. Also, scale influences are covered precisely in the framework of NSGT. Moreover, Mori-Tanaka homogenization model is introduced in order to obtain the effective material properties of FG nanobeams. Meanwhile, effects of external forces such as thermal and Lorentz forces are included in this research. Also, based upon the Hamilton's principle, the Euler-Lagrange equations are developed; afterwards, these equations are incorporated with those of NSGT to reach the nonlocal governing equations of FG-DNBSs. Furthermore, according to an analytical approach, the governing equations are solved to obtain the wave frequencies and phase velocities of FG-DNBSs. At the end, some illustrations are rendered to clarify the influences of a wide range of involved parameters.

• Progress in Superconductivity and Cryogenics
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• v.10 no.4
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• pp.9-12
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• 2008

The residual stress induced in the superconducting layer was estimated using analytical approach coupled with electro-mechanical test results and XRD measurements. The residual stress measured based on the $I_{c}/I_{c0}$-strain degradation behavior showed similar value with the measured residual stress using XRD. The calculated residual stress based on the thermal analysis showed the lowest value. This could be explained by the additional intrinsic residual stresses induced in the superconducting film during deposition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.9
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• pp.859-869
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• 2009

The sharp indenters such as Berkovich and conical indenters have a geometrical self-similarity in theory, but different materials have the same load-depth curve in case of single indentation. In this study, we analyze the load-depth curves of conical indenter with angles of indenter via finite element method. From FE analyses of dual-conical indentation test, we investigate the relationships between indentation parameters and load-deflection curves. With numerical regressions of obtained data, we finally propose indentation formulae for material properties evaluation. The proposed approach provides stress-strain curve and the values of elastic modulus, yield strength and strain-hardening exponent with an average error of less than 2%. It is also discussed that the method is valid for any elastically deforming indenters made of tungsten carbide and diamond for instance. The proposed indentation approach provides a substantial enhancement in accuracy compared with the prior methods.

• Smart Structures and Systems
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• v.17 no.6
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• pp.995-1015
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• 2016

In the design and condition assessment of bridges, it is usually necessary to take into consideration the extreme conditions which are not expected to occur within a short time period and thus require an extrapolation from observations of limited duration. Long-term structural health monitoring (SHM) provides a rich database to evaluate the extreme conditions. This paper focuses on the extrapolation of extreme traffic load effects on bridges using long-term monitoring data of structural strain. The suspension Tsing Ma Bridge (TMB), which carries both highway and railway traffic and is instrumented with a long-term SHM system, is taken as a testbed for the present study. Two popular extreme value extrapolation methods: the block maxima approach and the peaks-over-threshold approach, are employed to extrapolate the extreme stresses induced by highway traffic and railway traffic, respectively. Characteristic values of the extreme stresses with a return period of 120 years (the design life of the bridge) obtained by the two methods are compared. It is found that the extrapolated extreme stresses are robust to the extrapolation technique. It may owe to the richness and good quality of the long-term strain data acquired. These characteristic extremes are also compared with the design values and found to be much smaller than the design values, indicating conservative design values of traffic loading and a safe traffic-loading condition of the bridge. The results of this study can be used as a reference for the design and condition assessment of similar bridges carrying heavy traffic, analogous to the TMB.

• Advances in concrete construction
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• v.7 no.3
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• pp.151-166
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• 2019

This paper introduces a new efficient analytical method, based on shear deformations obtained with 2D elasticity theory approach, to perform an explicit closed-form solution for calculation the interfacial shear and normal stresses in plated RC beam. The materials of plate, necessary for the reinforcement of the beam, are in general made with fiber reinforced polymers (Carbon or Glass) or steel. The experimental tests showed that at the ends of the plate, high shear and normal stresses are developed, consequently a debonding phenomenon at this position produce a sudden failure of the soffit plate. The interfacial stresses play a significant role in understanding this premature debonding failure of such repaired structures. In order to efficiently model the calculation of the interfacial stresses we have integrated the effect of shear deformations using the equilibrium equations of the elasticity. The approach of this method includes stress-strain and strain-displacement relationships for the adhesive and adherends. The use of the stresses continuity conditions at interfaces between the adhesive and adherents, results pair of second-order and fourth-order coupled ordinary differential equations. The analytical solution for this coupled differential equations give new explicit closed-form solution including shear deformations effects. This new solution is indented for applications of all plated beam. Finally, numerical results obtained with this method are in agreement of the existing solutions and the experimental results.

• Journal of Korean Society of Steel Construction
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• v.10 no.3 s.36
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• pp.339-353
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• 1998

In this paper, the previous damage models for structures and their components under seismic repeated loading were reviewed systematically. A failure criterion for steel members under severe cyclic excitations as in strong earthquakes was described. A new approach to seismic damage assessment for steel members was proposed. This method was based on a series of the experimental and numerical investigations for steel members under very low cyclic loading. In this study, very low cyclic loading means repetitive loading, 5 to 20 loading cycles, within the large plastic range. The proposed damage assessment method was focused on the local strain history at the cross-section of the most severe concentration of deformation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.4
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• pp.703-710
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• 1994

A nonlinear FEM analysis of steel members under very-low-cycle loading has been performed in conjunction with experimental works. This analysis is an FEM tracing toward cracking of steel members under cyclic loads such as a strong earthquake. After verifying the procedure by comparing global hysteretic behaviors from the analytical and experimental results, the local stress-strain hysteresis at critical sections for large cyclic deformations was traced by the numerical analysis. Local strain history was discussed in relation to cracking. Based on the experimental and analytical results, a new approach to seismic safety assessment for steel members was proposed in this paper.

• The Plant Pathology Journal
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• v.18 no.2
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• pp.57-62
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• 2002

In vivo expression technology (IVET) has been developed to study bacterial gene expression in Salmonella typhimurium during host infection. The expression of selected genes by IVET has been elevated in vivo but not in vitro. The selected genes turned out to be important for bacterial virulence and/or pathogenicity. IVET depends on a synthetic operon with a promoterless transcriptional fusion between a selection marker gene and a reporter gene. The IVET approach has been successfully adapted in other bacterial pathogens and plant-associated bacteria using different selection markers. Pseudomonas putida suppresses citrus root rot caused by Phytophthora parasitica and enhances citrus seedling growth. The WET strategy was adapted based on a transcriptional fusion, pyrBC'-lacZ, in P. putida to study the bacterial traits important far biocontrol activities. Several genes appeared to be induced on P. parasitica hyphae and were found to be related with metabolism and regulation of gene expression. It is likely that the biocontrol strain took a metabolic advantage from the plant pathogenic fungus and then suppressed citrus root rot effectively. The result was parallel with those from the adaptation of IVET in P. fluorescens, a plant growth promoting rhizobacteria (PGPR). Interestingly, genes encoding components for type III secretion system have been identified as rhizosphere-induced genes in the PGPR strain. The type III secretion system may play a certain role during interaction with its counterpart plants. Application of IVET has been demonstrated in a wide range of bacteria. It is an important strategy to genetically understand complicated bacterial traits in the environment.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.253-260
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• 1998

An approximate method for the calculation of creep deflections of reinforced concrete beams under sustained service loads is proposed. The position of neutral axis and strain and stress distribution of fully cracked section after creep is determined from the requirements of strain compatibility and equilibruim of a section and then the long-term flexural rigidity of fully cracked section is determined based on the new neutral axis. The long-term flexural rigidity of uncracked section at the level of the reinforcenment. The approach of calculating long-term effective flexural rigidity and defections is similar to the current American Concrete Institue procedure for calculating effecitve moment of inertia and short-term deflections. The accuracy of the analysis is verified by comparison with several experimental mesurements of beam deflectons. The result is good between the theotetical values and mesured valus.

• Tunnel and Underground Space
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• v.5 no.4
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• pp.363-375
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• 1995

Critical literature review in this study revealed that there can be a significant influence of the residual stress on the engineering properties of rock. The review also showed that few number of research works on the quantification of the influence was attributed to the limitation of the two classical measurement techniques, viz, X-ray diffraction and mechanical relaxation method. In this study, a new way of approach was sought based on the assumption that residual stress up to the failure. A series of hoop tests conducted onthe samples from the limb of Carboniferous Limestone in Clevedon, England, revealed that (i) there is no preferential orientations of microcracks and minerals which have been widely believed as the main source of the strength anisotropy of rock; (ii) the anisotropy of the tensile strength of the limestone results from the influence of the residual stress; (iii) since jointing commenced within the fold, residual stored strain energy has been released preferentially in the direction perpendicular to the major joints(o$^{\circ}$ and 90$^{\circ}$); (ⅳ) during the hoop test making it much easier to create tensile fracture in these directons, viz 45$^{\circ}$ and 135$^{\circ}$)was released during the hoop test making it much easier to create tensile fracture in these directions, viz 45$^{\circ}$and 135$^{\circ}$;(v) the direction in which the stored strain energy may be presumed to be the least, required the greatest work to cause failure.