• Computers and Concrete
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• v.10 no.5
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• pp.435-455
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• 2012

In the recent years, rehabilitation of structures, strengthening and increasing the ductility of them under seismic loads have become so vital that many studies has been carried out on the retrofit of steel and concrete members so far. Bridge piers are very important members concerning rehabilitation, in which the plastic hinging zone is very vulnerable. Pier is usually confined by special stirrups predicted in the design procedure; moreover, fiber-reinforced polymers (FRP) jackets are used after construction to confine the pier. FRP wrapping of the piers is one of the most effective ways of increasing moment and ductility capacity of them, which has a growing application due to its relative advantages. In many earthquake-resistant bridges, reinforced concrete columns have a major defect which could be retrofitted in different ways like using FRP. After rehabilitation, it is important to check the strengthening adequacy by dynamic nonlinear analysis and precise modeling of material properties. If the plastic hinge properties are simplified for the strengthened members, as the simplified properties which FEMA 356 proposes for non-strengthened members, static nonlinear analysis could be performed more easily. Current paper involves this matter and it is intended to determine the plastic hinge properties for static nonlinear analysis of the FRP-strengthened circular columns.

• Geomechanics and Engineering
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• v.13 no.2
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• pp.301-318
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• 2017

Based on the existing research results, a three-dimensional failure mechanism of tunnel face was constructed. The dynamic seismic effect was taken into account on the basis of quasi-static method, and the nonlinear Mohr-Coulomb failure criterion was introduced into the limit analysis by using the tangent technique. The collapse pressure along with the failure scope of tunnel face was obtained through nonlinear limit analysis. Results show that nonlinear coefficient and initial cohesion have a significant impact on the collapse pressure and failure zone. However, horizontal seismic coefficient and vertical seismic proportional coefficient merely affect the collapse pressure and the location of failure surface. And their influences on the volume and height of failure mechanism are not obvious. By virtue of reliability theory, the influences of horizontal and vertical seismic forces on supporting pressure were discussed. Meanwhile, safety factors and supporting pressures with respect to 3 different safety levels are also obtained, which may provide references to seismic design of tunnels.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.4 s.44
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• pp.1-10
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• 2005

The purpose ol this study Is to suggest a proper analysis model that can evaluate seismic stability for local rock foundation of nuclear power plant. Sliding Analysis, Pseudo-static Analysis and Dynamic Analysis methods are used for analysing NPP rock foundation with the conditions like acting directions of input earthquake, boundary conditions, width and depth of analysing model, and modeling methods of weakness fault zones. As the results of study, Pseudo-static Analysis for lateral roller and dynamic analysis for transfer boundary condition showed good results, and analysing ranges of width and depth were 5 times of structure width and over 2 times ol structure depth.

• Advances in biomechanics and applications
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• v.1 no.1
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• pp.1-14
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• 2014

In this paper, a simple and accurate finite element model coupled to quasi-brittle damage law able to describe the multiple cracks initiation and their progressive propagation is developed in order to predict the complete force-displacement curve and the fracture pattern of human proximal femur under quasi-static load. The motivation of this work was to propose a simple and practical FE model with a good compromise between complexity and accuracy of the simulation considering a limited number of model parameters that can predict proximal femur fracture more accurately and physically than the fracture criteria based models. Different damage laws for cortical and trabecular bone are proposed based on experimental results to describe the inelastic damage accumulation under the excessive load. When the damage parameter reaches its critical value inside an element of the mesh, its stiffness matrix is set to zero leading to the redistribution of the stress state in the vicinity of the fractured zone (crack initiation). Once a crack is initiated, the propagation direction is simulated by the propagation of the broken elements of the mesh. To illustrate the potential of the proposed approach, the left femur of a male (age 61) previously investigated by Keyak and Falkinstein, 2003 (Model B: male, age 61) was simulated till complete fracture under one-legged stance quasi-static load. The proposed finite element model leads to more realistic and precise results concerning the shape of the force-displacement curve (yielding and fracturing) and the profile of the fractured edge.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.779-789
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• 1998

In this paper, the thermal shock responses of collinear cracks in a layered medium are investigated based on the uncoupled, quasi-static plane thermoelasticity. The medium is modeled as a bonded structure composed of a surface layer and a semi-infinite substrate. Between these two dissimilar homogeneous constituents, a functionally graded interfacial zone exists with the nonhomogeneous features of continuously varying thermoelastic properties. Three cracks are assumed to be present in the layered medium, one in each one of the constituent materials, aligned collinearly normal to the nominal interfaces. A system of singular integral equations is solved, subjected to the forcing terms of equivalent transient thermal tractions acting on the locations of cracks via superposition. Main results presented are the transient thermal stress intensity factors to illustrate the parametric effects of various geometric and amterial combinations of the medium with the thermoelastically graded interfacial zone and the collinear cracks.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.3
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• pp.157-168
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• 1993

Pipe network of hot water heat supply system in an apartment house was analyzed. Flowrate and supply heat capacity of each household in which constant flowrate balancing valve is installed in a single zone system were calculated and the results were investigated. In the existing piping system, the non-uniformity of heat supply with floors due to the static pressure and temperature difference between supply main and return main can not be avoided and this tendency get intense with the increase of the height of building. The non-uniformity of heat supply can be prevented by the installation of balancing valve at each household, however if the performance of supply pump is not sufficient to overcome the energy loss due to the installation of balancing valve for constant flow rate or if the selection of the valve capacity is not adequate, the valves will may lose their controllability.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.233-238
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• 2000

The purpose of this study is to outline the analysis procedure for evaluating the performance of moment resisting steel frames. For this purpose, three ordinary moment resisting frames are designed in compliance to UBC 1994. The evaluation is performed by nonlinear static procedures using two analytical models. Only one analytical model using panel element can reflect the panel zone deformation explicitly. The limit values in FEMA 273 are used as guidelines of predicted demand parameters by which the performance of OMRFs may be assessed.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2002.11a
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• pp.257-262
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• 2002

The object of this study is to investigate the effect of compounded welding through the AE (Acoustic Emission) characteristics for weld HAZ (Heat Affected Zone) on static tensile test. This study was carried out a SM 490A, high tension steel using the low hydrogen type E4316 of electronic shield metal arc welding, compound wire of $CO_2$ gas arc welding and tungsten electrode of TIG welding.

• The Journal of the Convergence on Culture Technology
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• v.10 no.2
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• pp.419-427
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• 2024

This study assessed the potential impact of gas leakage resulting from accidental damage to buried urban gas pipelines during perforating operation near subway construction sites. The risk of explosions due to ignition sources such as static electricity, arising from gas infiltrating the subway construction site through storm sewers and sewage pipes, was evaluated using the ALOHA program. The results of the threat zone calculation, which input various parameters of urban gas pipelines such as length, diameter, and pressure, indicated that the flammable area within the vapor cloud extended from 1.2 to 1.4 km (red zone), the blast area ranged from 0.8 to 1.0 km (yellow zone), and the jet fire extended from 45 to 61 m (red zone). This study demonstrates that within the flammable area of the vapor cloud, a specific combination of concentration and conditions can increase flammability. The blast area may experience explosions with a pressure of 1.0 psi, sufficient to break glass windows. In the event of a jet fire, high temperatures and intense radiant heat exposure lead to rapid fire propagation in densely populated areas, posing a high risk of casualties. The findings are presented in terms of the sphere of influence and threat zone ranges.

• Earthquakes and Structures
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• v.17 no.6
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• pp.545-556
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• 2019

Bridge piers with bending failure mode are seriously damaged only in the area of plastic hinge length in earthquakes. For this situation, a modified method for the layout of longitudinal reinforcement is presented, i.e., the number of longitudinal reinforcement is increased in the area of plastic hinge length at the bottom of piers. The quasi-static test of three scaled model piers is carried out to investigate the local longitudinal reinforcement at the bottom of the pier on the seismic performance of the pier. One of the piers is modified by increased longitudinal reinforcement at the bottom of the pier and the other two are comparative piers. The results show that the pier failure with increased longitudinal bars at the bottom is mainly concentrated at the bottom of the pier, and the vulnerable position does not transfer. The hysteretic loop curve of the pier is fuller. The bearing capacity and energy dissipation capacity is obviously improved. The bond-slip displacement between steel bar and concrete decreases slightly. The finite element simulations have been carried out by using ANSYS, and the results indicate that the seismic performance of piers with only increasing the number of steel bars (less than65%) in the plastic hinge zone can be basically equivalent to that of piers that the number of steel bars in all sections is the same as that in plastic hinge zone.