• Magazine of the Korea Concrete Institute
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• v.7 no.5
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• pp.145-154
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• 1995

Concrete has two different failure mechanisms : compressive crushing and tensile cracking. Concrete models should use the two different failure criteria to analyze the inelastic behavior of concrete including multiaxial crushing and tensile cracking. Concrete models used in this study are based on plasticity with multiple failure criteria of compressive crushing and tensile cracking. For tensile cracking behavior, two different plasticity models are investigated. The* ,e are rotating-crack and fixed-crack plasticity models, classified according to idealization of crack 0rientat:ions. The material models simplify inelastic behavior of concrete for plane stress problenls. The material models are used for the finite element anlaysis. Analytical results are compared with several experiments of reinforced concrete member. The advantages and disadva.ntages of rotating-crack and fixed -crack plasticity models are discussed.

• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.1
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• pp.1-9
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• 2021

Most commercial buildings among existing RC buildings in Korea have a multi-story wall-frame structure where RC shear wall is commonly used as its core at stairways or elevators. The members of the existing middle and low-rise wall-frame buildings are likely arranged in ordinary details considering building occupancy, and the importance and difficulty of member design. This is because there are few limitations, considerations, and financial burdens on the code for designing members with ordinary details. Compared with the intermediate or unique details, the ductility and overstrength are insufficient. Furthermore, the behavior of the member can be shear-dominated. Since shear failure in vertical members can cause a collapse of the entire structure, nonlinear characteristics such as shear strength and stiffness deterioration should be adequately reflected in the analysis model. With this background, an 8-story RC wall-frame building was designed as a building frame system with ordinary shear walls, and the effect of reflecting the shear failure mode of columns and walls on the collapse mechanism was investigated. As a result, the shear failure mode effect on the collapse mechanism was evident in walls, not columns. Consequently, it is recommended that the shear behavior characteristics of walls are explicitly considered in the analysis of wall-frame buildings with ordinary details.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.2
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• pp.103-111
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• 2014

In this study, the probabilistic internal pressure fragility analysis was performed by using the non-linear finite element analysis method. The target structure is one of the containment buildings of typical domestic pressurized water reactors(PWRs). The 3-dimensional finite element model of the containment building was developed with considering the large equipment hatches. To consider uncertainties in the material properties and structural capacities, we performed the sensitivity analysis of the ultimate pressure capacity with respect to the variation of four important uncertain parameters. The results of the sensitivity analysis were used to the selection of the probabilistic variables and the determination of their probabilistic parameters. To reflect the present condition of the tendon pre-stressing force, the data of the pre-stressing force acquired from the in-service inspections of tendon forces were used for the determination of the median value. Two failure modes(leak, rupture) were considered and their limit states were defined to assess the internal pressure fragility of target containment building. The internal pressure fragilities for each failure mode were evaluated in terms of median internal pressure capacity, high confidence low probability of failure(HCLPF) capacity, and fragility curves with respect to the confidence levels. The HCLPF capacity was 115.9 psig for leak failure mode, and 125.0 psig for rupture failure mode.

• International Journal of Concrete Structures and Materials
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• v.18 no.1E
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• pp.35-41
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• 2006

It is expected that recent development of mechanical models will soon supersede previous empirical methods of detailing. In this study, a mechanical model is proposed to analyze the behavior of the anchorage zone of prestressed concrete members. The main characteristics of the proposed model lies in its rational consideration of material properties such as concrete strength in biaxial stress state and that of local zone reinforced by spirals. The shear friction strength of concrete surrounding a spiral is also considered. The computational results of the proposed model as well as the existing Strut-and-Tie model(STM) and nonlinear finite element analysis are compared with experimental results. The results of the comparison revealed that the proposed model showed better prediction of the failure mode as well as the failure load. Additionally, the proposed model also explained the three-dimensional failure mechanism very well, while other methods based on two-dimensional analysis could not do so well.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.190-193
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• 2001

ZnO varistors have been widely used to protect power system and electronic system against overvoltages based on their excellent nonlinearity. In order to increase their protection capability, the fracture and protection technologies of arresters have to study according to their applications, namely ImA DC voltage, leakage currents, impulse residual voltages, withstanding capability to impulse surge, and energy absorption capability. ZnO varistors which have nonlinear current-voltage characteristic name a number of failure mechanism when ZnO elements absorb surge energies. Failure mode by thermal stress and Pin hole are among the most common failure mechanism at the high current surge current. In this study, the fracture mechaism of power arresters are introduced and protection technologies are researched. In particular the effect of thermal stress by surge currents to ZnO elements and methods against arc surge energy through withstand structure design of arrester are discussed.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.531-536
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• 1994

Wrapping machines in cigarette factories are equipped with indexing drive units with roller gear cam. At present there are no simple, visual, diagnostic techniques for predicting failure in these nits at an early stage. This paper proposes that failure could be predicted by using either a modified version of kurtosis, or the Wigner distribution method. The nonlinear vibration model proposed in this paper takes into consideration the play between the m and the cam follower, and precisely simulates the actual vibration. Statistics on the variance in play, obtained from the data on time history, call then be used to evaluate the effects of tile mage oil the cam and cam follower.

• Structural Engineering and Mechanics
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• v.5 no.5
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• pp.625-634
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• 1997

Reinforced concrete (RC) interior beam-column joints with high-strength materials: concrete compressive strength of 100 MPa and the yield strength of longitudinal bars of 685 MPa, were analyzed using three-dimensional (3-D) nonlinear finite element method (FEM). Specimen OKJ3 of joint shear failure type was a plane interior joint, and Specimen 12 of beam flexural failure type was a 3-D interior joint with transverse beams. Though the analytical initial stiffness was higher than experimental one, the analytical results gave a good agreement with the test results on the maximum story shear forces, the failure mode.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.913-919
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• 2001

In this study, fiber orientation of stiffener was conducted to increase buckling load or failure load in each case with a different design value and a different objective function for stiffened laminated composite panel of I-type under compression loading. Regarding each of buckling load or failure load as objective function, optimum design was carried out. In respect of optimum design, it was investigated that optimum shape for buckling could improve fail load for postbuckling, because it was difficult to investigate the optimization of postbuckling which need long analysis times for nonlinear analysis.

• Geomechanics and Engineering
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• v.7 no.4
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• pp.335-353
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• 2014

The softening hyperelastic model based on the strain energy limitation is of clear concepts and simple forms to describe the failure of materials. In this study, a linear and a nonlinear softening hyperelastic model are proposed to characterize the deformation and the failure in granular materials by introducing a softening function into the shear part of the strain energy. A method to determine material parameters introduced in the models is suggested. Based on the proposed models the numerical examples focus on bearing capacity and strain localization of granular materials. Compared with Volokh softening hyperelasticity and classical Mohr-Coulomb plasticity, our proposed models are able to capture the typical characters of granular materials such as the strain softening and the critical state. In addition, the issue of mesh dependency of the proposed models is investigated.

• Geomechanics and Engineering
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• v.12 no.2
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• pp.313-326
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• 2017

Based on the reliability theory and limit analysis method, the roof stability of a shallow tunnel is investigated under the condition of surface settlement. Nonlinear Hoek-Brown failure criterion is adopted in the present analysis. With the consideration of surface settlement, the internal energy and external work are calculated. Equating the rate of energy dissipation to the external rate of work, the expression of support pressure is derived. With the help of variational approach, a performance function is proposed to reliability analysis. Improved response surface method is used to calculate the Hasofer-Lind reliability index and the failure probability. In order to assess the validity of the present results, Monte-Carlo simulation is performed to examine the correctness. Sensitivity analysis is used to estimate the influence of different variables on reliability index. Among random variables, the unit weight significantly affects the reliability index. It is found that the greater coefficient of variation of variables lead to the higher failure probability. On the basis of the discussions, the reliability-based design is achieved to calculate the required tunnel support pressure under different situations when the target reliability index is obtained.