• Geotechnical Engineering
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• v.13 no.4
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• pp.177-198
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• 1997

Since decomposed granite soil shows various characteristics of shear behavior dependent on initial conditions such as weathering degree and grain breakage, it is nacessary to invert ligate stress -strain relationship and changes of shear characteristics for different initial conditions. Associated with abovefnentioned view, direct shear tests, and triaxial compression tutsts(Ef, CD) were carried out in this study for undisturbed and disturbed compacted weathered granite samples obtained from 4 construction work sites with the various weathering degree and components of parent rocks. The deformation behavior of undisturbed samples under small confining stress shows hardening to softening, which is similar to that of over nsolidated clay whereas disturbed weathered granite soils do hardeningfonstant regardless of weathering degree, which is also similar to sedimentary clay. Conventional direct shear-tests for undisturbed samples show a tendency to overestimate cohesion. It is possidle to approximate stress ratio(q/p') and volumetric increment ratio(dv/ds) in the triaxital compression tests by an equation, ($dv/d\varepsilon,=\alpha(M-\eta))$ irrespective of moisture content, weathering degree and disturbance.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.1
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• pp.77-86
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• 1997

The advanced development in many fields of engineering and science has caused much interests and demands for crashworthiness and non-linear dynamic transient analysis of structure response. Crash and impact problems have a dominant characteristic of large deformation with material plasticity for short time scales. The structural material shows strain rate-dependent behaviors in those cases. Conventional rate-independent constitutive equations used in the general purposed finite analysis programs are inadequate for dynamic finite strain problems. In this paper, a rate-dependent constitutive equation for elastic-plastic material is developed. The plastic stretch rate is modeled based on slip model with dislocation velocity and its density so that there is neither yielding condition, nor loading conditions. Non-linear hardening rule is also introduced for finite strain. Material constants of present constitutive equation are determined by experimental data of mild steel, and the constitutive equation is applied to uniaxile tension loading.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.6
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• pp.85-91
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• 2011

This study aims at evaluating feasibility of Bottom ash-mixed Foam Cement Banking(BFCB) Method on the enhancement of soft soil, which is developed to reduce self-weight of banking by applying bottom ash and foam. to cement slurry. In order to measure the behavior of soil when BFCB layer was covered to soft ground, a testing equipment for mock-up test was fabricated and phased loads were applied up to measurement of yielding and ultimate strengths as well as movement of ground particles. In addition, these measured values such as settlement and heaving were compared with ones of surface-hardening method prevailing on soil improvement. As the result through mock-up test, BFCB showed lower values of ground deformation, while wider range of deformation was observed in compare to the other method. And settlement and heaving were measured lower, which implies the method developed is very effective to applicability of soft ground.

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.405-415
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• 2011

For the safe seismic design of buildings, it is necessary to predict the plastic deformation demands of the members as well as the story drift ratio. In the present study, a simple method of estimating the beam plastic rotation was developed for special-moment-resisting steel frame structures designed with strong column-weak beam behavior. The proposed method uses elastic analysis rather than nonlinear analysis, which is difficult to use in practice. The beam plastic rotation was directly calculated based on the results of the elastic analysis, addressing the moment redistribution, the column and joint dimensions, the movement of the plastic hinge, the panel zone deformation, the gravity load, and the strain-hardening behavior. In addition, the rocking effect of the braced frame or core wall on the beam plastic rotation was addressed. For verification, the proposed method was applied to a six-story special-moment frame designed with strong column-weak beam behavior. The predicted plastic rotations of the beams were compared with those that were determined via nonlinear analysis. The beam plastic rotations that were predicted using the proposed method correlated well with those that were determined from the nonlinear pushover analysis.

• Korean Journal of Metals and Materials
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• v.48 no.6
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• pp.477-488
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• 2010

Zr-based amorphous alloy matrix composites reinforced with stainless steel (STS) and tantalum continuous fibers were fabricated without pores or defects by a liquid pressing process, and their quasi-static and dynamic deformation behaviors were investigated by using a universal testing machine and a Split Hopkinson pressure bar, respectively. The quasi-static compressive test results indicated that the fiberreinforced composites showed amaximum strength of about 1050~1300 MPa, and its strength maintained over 700 MPa until reaching astrain of 40%. Under dynamic loading, the maximum stresses of the composites were considerably higher than those under quasi-static loading because of the strain-rate hardening effect, whereas the fracture strains were considerably lower than those under quasi-static loading because of the decreased resistance to fracture. The STS-fiber-reinforced composite showed a greater compressive strength and ductility under dynamic loading than the tantalum-fiber-reinforced composite because of the excellent resistance to fracture of STS fibers.

• Geomechanics and Engineering
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• v.29 no.5
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• pp.509-522
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• 2022

Tail-grouting is an effective measure in shield engineering for filling the gap at the shield tail to reduce ground deformation. However, the gap-filling ratio affects the value of the gap parameters, leading to different surface settlements. It is impossible to adjust the fill ratio indiscriminately to study its effect, because the allowable adjustment range of the grouting quantity is limited to ensure construction site safety. In this study, taking the shield tunnel section between Chaoyanggang Station and Shilihe Station of Beijing Metro Line 17 as an example, the correlation between the tail-grouting parameter and the surface settlement is investigated and the optimal grouting quantity is evaluated. This site is suitable for conducting field tests to reduce the tail-grouting quantity of shield tunneling over a large range. In addition, the shield tunneling under different grouting parameters was simulated. Furthermore, we analyzed the evolution law of the surface settlement under different grouting parameters and obtained the difference in the settlement parameters for each construction stage. The results obtained indicate that the characteristics of the grout affect the development of the surface settlement. Therefore, reducing the setting time or increasing the initial strength of the grout could effectively suppress the development of surface subsidence. As the fill ratio decreases, the loose zone of the soil above the tunnel expands, and the soil deformation is easily transmitted to the surface. Meanwhile, owing to insufficient grout support, the lateral pressure on the tunnel segments is significantly reduced, and the segment moves considerably after being removed from the shield tail.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.221-226
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• 2005

In this paper, a dynamic model for the rotor shaft-coupling-blade system is developed. The blades are attached to a disk and driven by an electric motor shaft which is flexible in torsion. We assumed that the shaft torsional flexibility is lumped in the flexible coupling which is usually adopted in rotor systems. The Lagrangian approach with the small deformation theory for both blade-bending and shaft-torsional deformations is employed for developing the equation of the motion. The assumed modes method is used for estimating the blade transverse deflection. The numerical results highlight the effects of both structural damping of the system and the torsional stiffness of the flexible coupling to the dynamic response of the blade. The results showed strong coupling between the blade bending and shaft torsional vibrations in the form of inertial nonlinearif, stiffness hardening and softening.

• Journal of Power System Engineering
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• v.17 no.6
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• pp.122-129
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• 2013

The microstructure and deformation behavior in 22Cr-0.2N micro-duplex stainless steels with various Ni and Mn contents were compared using by OM, TEM, and XRD. The 22Cr-0.2N duplex stainless steel plates were fabricated and hot rolled, followed by annealing treatment at the temperature range of $1,000-1,100^{\circ}C$. All the samples showed the common strain hardening behaviour during the tensile test at a room temperature. The steels tested at the temperatures of $-30^{\circ}C$ or $-50^{\circ}C$ showed a distinct inflection point in the stress-strain curves, which should be resulted from the formation of strain-induced martensite(SIM) of austenite phase. This was confirmed by TEM observations. The onset strain of a inflection point in a stress-strain curve should be depended up the value of $M_d30$. With the decrease of the tensile test temperature, the inflection point appeared earlier, and the strength and fracture strain were higher. The tensile behaviour was discussed from the point of austenite stability of the micro-duplex stainless steels with the different Ni and Mn content.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.182-189
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• 2002

This paper is concerned with a collapse behavior analysis for a thin-walled structure considering farming effects. Numerical simulation is carried out with a finite element limit analysis in order to identify forming effects on collapse behavior of a thin-walled structure such as an S-rail. The formed S-rail contains fabrication histories such as residual stress, work hardening, non-uniform thickness distribution and geometric changes resulted from the forming process. The collapse behavior analysis of an S-rail with forming effects leads to different results from that without such effects. The present study deals with the collapse analysis of the S-rail fabricated with the typical forming, trimming and springback processes. Collapse properties such as the collapse load, the collapse mode and the energy absorption are calculated and investigated In order to identify forming effects. It is fully demonstrated that the design of thin-walled structures needs to consider the forming effects for a proper assessment of the load-carrying capacity and the deformation of the formed structures.

• Korean Journal of Materials Research
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• v.17 no.6
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• pp.342-346
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• 2007

Microstructure and tensile strength of the vacuum brazed stainless steel were investigated in this study. For vacuum brazing of the stainless steel 303 and 304, the BNi-2, 3, 4 and 7 were used as filler metals. Among these filler metals, the BNi-2 showed excellent wettability at $1050^{\circ}C$. Indeed, the brazed stainless steel using the BNi-2 showed the highest tensile strength (483 MPa) among all brazed specimens. This is attributed to degree of interfacial reaction between the filler metal and stainless steel. Brazed stainless steel with BNi-2, 3 filler metals showed almost elastic deformation followed by plastic yielding and strain hardening up to a peak stress. On the other hand, it is likely that the fracture of the brazed specimens with BNi-4, 7 was occurred in elastic range without plastic yielding up to a peak stress.