• Computational Structural Engineering
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• v.8 no.1
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• pp.137-146
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• 1995

Structural stress under shock or impact load is varied with the lapse of time and the structural stress is called stress wave. Propagating longitudinal stress wave is studied in a 2-dimensional plate. A finite element program for elastic stress wave propagation is developed in order to investigate the shape of stress field at time increment. The longitudinal stress wave is generated by unit step function. According to the finite element analysis results, the longitudinal stress wave propagates to the similar direction of impact load and the front of stress wave propagates with the same speed as analytic solution and the shape of stress field is similar to that of analytic solution. The shear wave is occurred after the longitudinal stress wave and declined at an angle of 45 degrees compared with longitudinal stress wave and the speed of shear wave is about a half of the longitudinal stress wave. The intensity of shear wave is larger than that of longitudinal stress wave.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.77-84
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• 2000

In this paper, the stress analysis of the cast iron insert of spent nuclear fuel disposal canister in a deep repository at 500m underground is done for the underground pressure variation. Since the nuclear fuel disposal usually emits much heat and radiation, its careful treatment is required. And so a long term safe repository at a deep bedrock is used. Under this situation, the canister experiences some mechanical external loads such as hydrostatic pressue of underground water, swelling pressure of bentonite, sudden rock movement etc.. Hence, the canister should be designed to withstand these loads. The cast iron insert of the canister mainly supports these loads. Therefore, the stress analysis of the cast iron insert is done to determine the design variables such as the diameter versus length of canister and the number and array type of inner baskets in this paper, The linear static structural analysis is done using the finite element analysis method. And the finite element analysis code, NISA, is used for the computation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.04a
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• pp.175-182
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• 1998

The object of this study is shape finding and cutting pattern generation of membrane structures under the following assumptions : (1) material is linearly elastic (2) stress state is plane stress. Cable and membrane structures should introduce the nonlinear analysis considering geometric nonlinearity because these structures deform largely under the external loads. The analysis procedure is consisted of three steps considering geometric nonlinearity unlike any other structures. First step is the shape finding analysis to determine the initial equilibrium shape. Second step is the stress-deformation analysis to investigate the behaviors of structures under various external loads. Once a satisfactory shape has been found, a cutting pattern based on the shape finding analysis may be generated from the view point of construction. In this paper, (1) shape finding analysis formulation and an example, (2) cutting pattern determination procedure using weighted least-square minimization flattening method and some results are presented.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.266-273
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• 1998

The object of this study is shape finding and cutting pattern generation of membrane structures under the following assumptions: (1) material is linearly elastic (2) stress state is plane stress. Cable and membrane structures should introduce the nonlinear analysis considering geometric nonlinearity because these structures deform largely under the external loads. The analysis procedure is consisted of three steps considering geometric nonlinearity unlike any other structures. First step is the shape finding analysis to determine the initial equilibrium shape. Second step is the stress-deformation analysis to investigate the behaviors of structures under various external loads. Once a satisfactory shape has been found, a cutting pattern based on the shape finding analysis may be generated from the view point of construction. In this paper, after shape finding analysis, cutting pattern determination procedure using weighted least-square minimization flattening method and some results are presented.

• Steel and Composite Structures
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• v.29 no.2
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• pp.175-186
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• 2018

The plastic hinge method and the plastic zone method are extensively adopted in displacement-based elements and force-based elements respectively for second-order inelastic analysis. The former enhances the computational efficiency with relatively less accurate results while the latter precisely predicts the structural behavior but generally requires more computer time. The displacement-based elements receive criticism mainly on plasticity dominated problems not only in accuracy but also in longer computer time to redistribute the forces due to formation of plastic hinges. The multi-element-per-member model relieves this problem to some extent but will induce a new problem in modeling of member initial imperfections required in design codes for direct analysis. On the contrary, a force-based element with several integration points is sufficient for material yielding. However, use of more integration points or elements associated with fiber section reduces computational efficiency. In this paper, a new force-based element equipped with stress-resultant plasticity model with minimal computational cost is proposed for second-order inelastic analysis. This element is able to take the member initial bowing into account such that one-element-per-member model is adequate and complied with the codified requirements of direct analysis. This innovative solution is new and practical for routine design. Finally, several examples demonstrate the validity and accuracy of the proposed method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.504-512
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• 2003

Simulation programs have been developed and used as an attempt to improve the accuracy of Non-Destructive Evaluation(NDE) techniques. The applicability of these programs is very limited, however, because it is difficult to describe the delicacy of the propagation of stress waves. To investigate the applicability of the finite element analysis for stress wave-based NDE techniques numerical simulation for Impact-Echo method and SASW method is performed. The numerical studies are performed to determine the essential parameters such as contact time of impact load, mesh size and time step size. These studies show that the choice of parameter is very important for improving the accuracy and confidence of the numerical procedure and, thereby, the applicability of the numerical analysis for stress wave-based NDE techniques

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.87-94
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• 1999

The structural behavior of welded steel box columns subjected to axial compression and combined load of axial and horizontal load is described. The nonlinear stress-strain relation of the material and residual stress resulted from welds were included in the analysis. Inelastic buckling analysis of hollow rectangular sections of various width-thickness and slenderness ratios was carried out using the semi-analytical and spline finite strip method to investigate the local and global bucking stress and mode interaction. The buckling stress was compared with test results and design curves. Post-buckling behavior was traced by the finite element program(ADINA) and compared with experimental results. The comparison showed that the ultimate stress can be used for the design purpose.

• Computational Structural Engineering
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• v.10 no.1
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• pp.129-134
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• 1997

Interfacial stress singularity in a unidirectional two-dimensional laminate model consisting of an elastic fiber and a viscoelastic matrix has been investigated using the time-domain boundary element method. First, the interfacial singular stresses between the fiber and the matrix of a unidirectional laminate subjected to a uniform transverse tensile strain have been investigated near the free surface, but without any defect or any edge crack. Such a stress singularity might lead to fiber-matrix debonding or interfacial edge cracks. Then, the overall stress intensity factor for the case of a small interfacial edge crack of length a has been computed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.04a
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• pp.155-162
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• 1994

The drying shrinkage of concrete has a close relation to the water movement, Since the diffusion process of water in concrete is strongly dependent on the temperature and pore humidity, the process is highly nonlinear phenomena. It is shown that the analytical results of this study are in good agreement with experimental data in the literatures, and results calculated by BP-KX model. The internal stress caused by moisture distribution which was resulted from the diffusion process, was calculated quantitatively. The tensile stress which occurred in the drying outer zone mostly exceeded the tensile strength of concrete, and necessarily would result in crack formation.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.455-467
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• 2001

In this study, the stacking phase shift effect on the effective property and stress distribution was investigated for 8-harness satin weave textile composites under uni-axial tension. Textile configurations with varied phase shifts were modeled by unit cells and repeating boundary conditions were applied at the outer periodic surfaces. The effective property and stress were calculated by the unit cell analysis using macro-element to reduce the computational resource. It was found that stresses were dependent on the variation of tow arrangement of adjacent layers. The in-phase and the shifted configurations showed large differences in the stress distribution pattern. The stress level was very high in the resin region and the distribution of the maximum stresses was widely scattered.