• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.718-725
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• 2017

A liquid storage tank is one of the most important structures in industrial complexes dealing with chemicals, and its structural damage due to an earthquake may cause a disastrous event such as the leakage of hazardous materials, fire, and explosion. It is thus essential to assess the seismic fragility of liquid storage tanks and prepare for seismic events in advance. When a liquid storage tank is oscillated by a seismic load, the hydrodynamic pressure caused by the liquid-structure interaction increases the stress and causes structural damage to the tank. Meanwhile, the seismic fragility of the structure can be estimated by considering the various sources of uncertainty and calculating the failure probabilities in a given limiting state. To accurately evaluate the seismic fragility of liquid storage tanks, a sophisticated finite element analysis is required during their reliability analysis. Therefore, in this study, FERUM-ABAQUS, a recently-developed computational platform integrated with commercial finite element and reliability analysis software packages, is introduced to perform the finite element reliability analysis and calculate the failure probability of a liquid storage tank subjected to a seismic load. FERUM-ABAUS allows for automatic data exchange between these two software packages and for the efficient seismic fragility assessment of a structure. Using this computational platform, the seismic fragility curve of a liquid storage tank is successfully obtained.

• Geotechnical Engineering
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• v.3 no.4
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• pp.7-20
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• 1987

This study was performed to investigate the effect of time-dependent creep on the deformation analysis of multi-dimensional consolidation using the finite element method for young Sedimentary clay. It was assumed that the creep in the clay had occured during consolidation. In the analysis, the Modified cam-clay theory originated from the critical state theory was used as the constitutive equation, in which a term equivalent to the creep was supplemnted. The results of the analysis were in good agreement with the observed values in the field.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.1
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• pp.65-70
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• 2014

This paper introduces a preform design method for a ring rolling process with an outer step. Underfilling is one of the general defects of the profile ring rolling process. It occurs when the deformation amount is small or step depth of the profiled region is large. To prevent underfilling, increasing the deformation amount or using a preform of size similar to that of the final product are required. Furthermore, the filling limit equation is suggested based on the shape factor and deformation ratio for preventing defects in the products. The filling limit equation has been derived through finite element analyses and production tests for four different cases. For verifying the suggested method, realsized profile rolling tests were performed, and test results were compared with the predictions of the equation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.2
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• pp.269-279
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• 1994

This paper concentrates on the finite element analysis of concrete structures considering the material nonlinearity and time-dependent structural behavior. Using the rotating crack model among the smeared cracking model, the structural behavior up to ultimate load is simulated, and concrete is assumed to be an orthotropic material. Especially to include the tension stiffening effect in bending behavior, a criterion based on the fracture mechanics concept is introduced and the numerical error according to the finite element mesh size can be minimized through the application of the proposed criterion. Besides, the governing equation for steel is systematized by embeded model to cope with the difficulty in modeling of complex geometry. Finally, to trace the structural behavior with time under cracked and/or uncracked section, an algorithm for the purpose of time-dependent analysis is formulated in plane stress-strain condition by the age-adjusted effective modulus method.

• Journal of Korean Society of Steel Construction
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• v.24 no.3
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• pp.279-287
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• 2012

A double split tee connection is used as a connection that is suitable for ordinary moment frames or special moment frames according to the combination of variables of the thickness of the T-stub flange and the gauge distance of the high-strength bolts. In order to demonstrate safe structural behavior, a double split tee connection must meet the requirements for inter-story drift angles and the moment of connection, as defined in the Korea Building Code-Structural. In order to determine whether the these requirements are met, it is necessary to predict rotational stiffness and the ultimate plastic moment of the connection. Therefore, this study primarily aimed to propose an analytical model for predicting the rotational stiffness of a double split tee connection under a static load. Toward this end, a three-dimensional, non-linear finite element analysis was carried out. Then, the applicability of the proposed model was verified after comparing the test results of this study with other studies.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.5
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• pp.411-418
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• 2008

In this work, the effect of strength mismatch on plastic limit loads is quantified for similar metal weld plates with cracks under tension load, via three-dimensional, small strain elastic-perfectly plastic finite element analyses. Relevant variables related to plate geometry and crack length are systematically varied, in addition to the weld width. An important finding is that mis-match limit loads can be uniquely quantified through strength mis-match ratio and one geometry-related parameter. Based on the proposed limit load solutions, reference stress based J-integral estimates is also investigated. When the reference stress is defined by the mis-match limit load, predicted J-integral values agree overall well with FE results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.9
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• pp.943-951
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• 2014

The tip geometries of the pyramidal and conical indenters used for micro/nano-indentation tests are not sharp. They are inevitably rounded because of their manufacturability and wear. In many indentation studies, the tip geometries of the pyramidal indenters are simply assumed to be spherical, and the theoretical solution for spherical indentation is simply applied to the geometry at a shallow indentation depth. This assumption, however, has two problems. First, the accuracy of the theoretical solution depends on the material properties and indenter shape. Second, the actual shapes of pyramidal indenter tips are not perfectly spherical. Hence, we consider the effects of these two problems on indentation tests via finite element analysis. We first show the relationship between the Poisson's ratio and load-displacement curve for spherical indentation, and suggest improved solutions. Then, using a possible geometry for a Berkovich indenter tip, we analyze the characteristics of the load-displacement curve with respect to the indentation depth.

• Journal of Korean Society of Steel Construction
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• v.27 no.5
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• pp.447-454
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• 2015

The researches on circular hollow section(CHS) connections have been conducted continuously because of development of material properties and complex local behavior of the connections. The purpose of this study is that the effects of material strength and chord wall slenderness on chord plastification and strength of CHS X-joint truss connection under compression on branch member were evaluated. To this end, finite element analyses were performed for various connections, using ANSYS Mechanical APDL program. Based on the analysis results, the design strength of the connections according to chord plastification limit state in KBC were examined. Finally, special considerations for CHS X-joint connection design were suggested.

• Journal of Korean Society of Steel Construction
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• v.13 no.5
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• pp.567-575
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• 2001

In order to consider statistical properties of probability variables used in the structural analysis the conventional approach using the safety factor based on past experience usually estimated the safety of a structure Also the real structures could only be analyzed with the error in estimation of loads material characters and the dimensions of the members. But the errors should be considered systematically in the structural analysis Safety of structure could not precisely be appraised by the traditional structural design concept Recently new aproach based on the probability concept has been applied to the assessment of structural safety using the reliability concept Thus the computer program by the Probabilitstic FEM is developed by incorporating the probabilistic concept into the conventional FEM method. This paper estimated for the reliability of a plane stress structure by Advanced First-Order Second Moment method using von Mises, Tresca and Mohr-Coulomb failure criterions. Verification of the reliability index and failure probability of attained by the Monte Carlo Simulation method with the von Mises criterion were same as PFEM, but the Monte Carlo Simulation were very time-consuming. The variance of member thickness and load could influence the reliability and failure probability most sensitively among the design variables from the results of the parameter analysis. The proper failure criterion according to characteristic of materials must be used for safe design.

• Journal of the Korean Geotechnical Society
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• v.20 no.1
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• pp.121-129
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• 2004

In this study, a slope stability chart for assessing stability of homogeneous simple soil slopes is proposed. Most existing slope stability charts are based on limit equilibrium method, which is not rigorous in mechanical standpoint. Meanwhile, limit analysis based on the principle of virtual work and the bound theorems of plasticity is suitable for evaluating the stability of geotechnical structures such as slope due to its simplicity in computation and mechanical rigor. Numerical limit analysis taking advantage of finite elements and linear programming can consider various slope conditions and, in addition, find the optimum stability solution with effeciency. In this study, a numerical limit analysis program in terms of effective stress is developed and a mechanically rigorous slope stability chart is proposed by performing stability analyses for various slope conditions. Pore pressure ratio, commonly used in stability charts, is applied to consider the effects of pore pressure for effective stress analysis. As a result of comparison between proposed stability chart and Spencer's stability chart, it was found that Spencer's chart solutions are biased to lower bound which means conservative in design.