• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.04a
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• pp.233-240
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• 1997

Seven kinds of hysteric model were used and classified three groups considering the absorbing capacities of strain energy for each model. Four kids of each model. Four kinds of strong motion earthquake record (two of them were recorded in Japan and the others in U.S.A) are used. The yield strength of building was set in the ratio to the maximum input acceleration (Yield Strength / Maximum Acceleration = 0.5~3.0). Natural periods of structures were varied 0.1~3.0 second with an interval of 0.1 second. First group : Elastic-Plastic model, Ramberg-Osgood model Second group : Degrading Tri-liner model, Takeda model Third group : Slip model, Origin model, Max-D model Elastic-plastic response spectra were calculated for response velocities, displacement, energy input, ductility factors, accumulated ductility factors. The equivalent response values of M.D.O.F systems against S.D.O.F system were calculated to compare the relationship of two systems.

• Journal of Ocean Engineering and Technology
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• v.27 no.2
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• pp.19-26
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• 2013

Stress triaxiality is recognized as one of the most important factors for predicting the failure strain of ductile metals. This study dealt with the effect of the average stress triaxiality on the failure strain of a typical low-temperature high-strength marine structural steel, EH36. Tensile tests were carried out on flat specimens with different notches, from relatively smooth to very sharp levels. Numerical simulations of each specimen were performed by using ABAQUS. The failure initiation points in numerical simulations were identified from a comparison of the engineering stress vs. strain curves obtained from experiments with simulated ones. The failure strain curves for various dimensionless critical energy levels were established in the average stress triaxiality domain and compared with the identified failure strain points. It was observed that most of the failure initiation points were approximated with a 100% dimensionless critical energy curve. It was concluded that the failure strains were well expressed as a function of the average stress triaxiality.

• Structural Engineering and Mechanics
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• v.18 no.6
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• pp.769-790
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• 2004

The compressive behavior up to failure of short concrete members reinforced with fiber reinforced plastic (FRP) is investigated. Rectangular cross-sections are analysed by means of a simplified elastic model, able also to explain stress-concentration. The model allows one to evaluate the equivalent uniform confining pressure in ultimate conditions referred to the effective confined cross-section and to the effective stresses in FRP along the sides of section; consequently, it makes it possible to determine ultimate strain and the related bearing capacity of the confined member corresponding to FRP failure. The effect of local reinforcements constitute by single strips applied at corners before the continuous wrapping and the effect of round corners are also considered. Analytical results are compared to experimental values available in the literature.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.344-349
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• 2008

Ratcheting behavior of IN 718 was investigated at $649^{\circ}C$ under various proportional and non-proportional loading conditions with stress control. The material response was initially elastic but substantial plastic strain was developed as the material softened cyclically. Ratcheting strain was measured to near fatigue life, and is found to have three stages of development - primary, secondary (steady-state) and tertiary. The secondary stage dominates for most cases. Under the same equivalent stress amplitude and mean stress, it was revealed that circular path loading gives higher ratcheting rates and shorter lives than linear paths and that the more ratcheting occurs when the cyclic load is in the same direction as the mean stress. The ratcheting strain at failure depends not only on its rate but also on fatigue life itself, and it is not a primary life-determining factor.

• The Journal of Advanced Prosthodontics
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• v.13 no.1
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• pp.12-23
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• 2021

Purpose. The aim of the study was to compare the lingualized implant placement creating a buccal cantilever with prosthetic-driven implant placement exhibiting excessive crown-to-implant ratio. Materials and Methods. Based on patient's CT scan data, two finite element models were created. Both models were composed of the severely resorbed posterior mandible with first premolar and second molar and missing second premolar and first molar, a two-unit prosthesis supported by two implants. The differences were in implants position and crown-to-implant ratio; lingualized implants creating lingually overcontoured prosthesis (Model CP2) and prosthetic-driven implants creating an excessive crown-to-implant ratio (Model PD2). A screw preload of 466.4 N and a buccal occlusal load of 262 N were applied. The contacts between the implant components were set to a frictional contact with a friction coefficient of 0.3. The maximum von Mises stress and strain and maximum equivalent plastic strain were analyzed and compared, as well as volumes of the materials under specified stress and strain ranges. Results. The results revealed that the highest maximum von Mises stress in each model was 1091 MPa for CP2 and 1085 MPa for PD2. In the cortical bone, CP2 showed a lower peak stress and a similar peak strain. Besides, volume calculation confirmed that CP2 presented lower volumes undergoing stress and strain. The stresses in implant components were slightly lower in value in PD2. However, CP2 exhibited a noticeably higher plastic strain. CONCLUSION. Prosthetic-driven implant placement might biomechanically be more advantageous than bone quantity-based implant placement that creates a buccal cantilever.

• Structural Engineering and Mechanics
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• v.63 no.1
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• pp.23-35
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• 2017

A nonlinear static procedure considering work-energy principle and global failure mechanism to estimate base shears of reinforced concrete (RC) frame-type structures is presented. The relative energy equation comprising of elastic vibrational energy, plastic strain energy and seismic input energy is obtained. The input energy is modified with a factor depending on damping ratio and ductility, and the energy that contributes to damage is obtained. The plastic energy is decreased with a factor to consider the reduced hysteretic behavior of RC members. Given the pre-selected failure mechanism, the modified energy balance equality is written using various approximations for modification factors of input energy and plastic energy in scientific literature. External work done by the design lateral forces distributed to story levels in accordance with Turkish Seismic Design Code is calculated considering the target plastic drift. Equating the plastic energy obtained from energy balance to external work done by the equivalent inertia forces considering, a total of 16 energy-based base shears for each frame are derived considering different combinations of modification factors. Ductility related parameters of modification factors are determined from pushover analysis. Relative input energy of multi degree of freedom (MDOF) system is approximated by using the modal-energy-decomposition approach. Energy-based design base shears are compared with those obtained from nonlinear time history (NLTH) analysis using recorded accelerograms. It is found that some of the energy-based base shears are in reasonable agreement with the mean base shear obtained from NLTH analysis.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.285-299
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• 1993

The objective of the present study is to analyze material flow in the metal forming processes by using computer simulation and experiment with model material, plasticine. A UBET program is developed to analyze the bulk flow behaviour of various metal forming problems. The elemental strain-hardening effect is considered in an incremental manner and the element system is automatically regenerated at every deforming step in the program. The material flow behavior in closed-die forging process with rib-web type cavity are analyzed by UBET and elastic-plastic finite element method, and verified by experiments with plasticine. There were good agreements between simulation and experiment. The effect of corner rounding on material flow behavior is investigated in the analysis of backward extrusion with square die. Flat punch indentation process is simulated by UBET, and the results are compared with that of elastic-plastic finite element method.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.320-327
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• 2005

Liquefaction characteristics of saturated sand under various dynamic loadings such as sinusoidal, wedge, increasing wedge and real earthquake loading are investigated focusing on the excess pore water pressure build up instead of liquefaction resistance strength in this paper. There are large differences between two types of earthquake loading - impact and vibration in liquefaction characteristics. The angle of phase change line of sinusoidal loading is very close to the vibration type, whereas the cumulative deviator stress and cumulative plastic strain are larger than two types of real earthquake loadings. On the other hand, the liquefaction characteristics of increasing wedge loadings are located in the range between vibration and impact earthquake loadings. It is concluded that the sinusoidal loading overestimates the resistance of soil under real earthquake loading. Based on results obtained, the increasing wedge loading can reflect the liquefaction behavior under real earthquake loadings more efficiently than sinusoidal loading based on equivalent uniform stress concept.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.317-326
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• 2002

Recently a simple design method for rib-reinforced seismic steel moment connections has been proposed based on equivalent strut model. An experimental program was implemented to verify the proposed design method and to develop the schemes that will prevent the cracking at the rib tip, where stress concentration was evident. All the specimens designed by the proposed method were able to develop satisfactory connection plastic rotation of 0.04 radian. Slight beam flange trimming, in addition to rib reinforcement, pushed the plastic hinging and local buckling of the beam away from the rip tip and effectively reduced the cracking potential at the rib tip. The strut action of the rib and resulting reverse shear in the beam web were also experimentally identified through the strain gage readings.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.5
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• pp.474-481
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• 2007

A three-dimensional finite element model has been used to simulate the bead on plate welding of curved steel plates having curvature in the welding direction. By using traditional method such as thermal-elastic-plastic(TEP) finite element analysis. the weld-induced deformation can be accurately predicted. However, three-dimensional finite element analysis is not practical in analyzing the weld-induced deformation of large and complex structures such as ship structures in view of computing time and cost. In this study, used is the equivalent loading method based on inherent strain to illustrate the effect of the longitudinal curvature upon the weld-induced deformation of curved plates.