• Journal of Korean Society of Steel Construction
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• v.21 no.2
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• pp.155-164
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• 2009

In this study, a computationally efficient parallel axial-flexural plastic hinge model is proposed for nonlinear dynamic progressive collapse analysis of welded steel moment frames. To this end, post-yield flexural behavior and the interaction of bending moment and axial force of the double-span beams in the column's missing event was first investigated by using material and geometric nonlinear parametric finite element analysis. A piece-wise linear parallel point hinge model that captures the moment-axial tension interaction was then proposed and applied to nonlinear dynamic progressive collapse analysis of welded steel moment frames with the use of the OpenSees Program. The accuracy as well as the efficiency of the proposed model was verified based on the inelastic dynamic finite element analysis results. The importance of including the catenary action effects for proper progressive collapse resistant analysis and design was also emphasized.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.45-52
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• 2003

A finite element procedure to estimate ultimate strength of space frames considering spread of plasticity is presented. The improved displacement field is introduced based on inclusion of second order terms of finite rotations. All the nonlinear terms due to bending and torsional moment as well as axial force are precisely considered. The concept of plastic hinge is introduced and the incremental load/displacement method is applied for the elasto-plastic analysis. The initial yield surface is defined based on the residual stress and the full plastification surface is considered under the combined action of axial force, bending and torsional moments. The elasto-plastic stiffness matrices are derived using the flow rule and the normality condition of the limit function. Finite element solutions for ultimate strength of space frames are compared with available solutions and experimental results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1990.10a
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• pp.28-33
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• 1990

This paper presents an efficient and accurate method for nonlinear analysis of frame structures by idealized structural unit method. The main idea behind the present method is to minimize the cost of the computational effort by reducing the number of unknowns. An explicit form of the tangential elastic stiffness matrix of the element is derived by using updated Lagrangian approach. An ultimate limit state of the element is judged on the basis of the formation of a plastic hinge mechanism. The elasto-plastic stiffness matrix and the post-ultimate stiffness matrix of the element are formulated by plastic node method. A comparison between the present method is very efficient and accurate because the computing time required is very small while giving the accurate solution.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.555-562
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• 2014

To perform performance-based seismic design of buildings, it is necessary clear goal for usage and stability after an earthquake. To clear this goal, it requires a review of the constituent material of the building and, in particular, a member used as an indicator of the residual strain is useful. There are more usage of prestressed concrete because of prestressing steel witch has characteristics of the origin-oriented. In this study, the goal is estimating of residual strain on the prestressed concrete beam member. The expression for angle of deformed prestressed concrete beam member was obtained from using of curvature on the critical section and the equivalent plastic hinge length based on 'equivalent plastic hinge length method'. Considering the balance of strength and deformation conditions, suitable analysis values were derived from 'split Element Method'. Through various parametric studies, various factors affecting the residual strain were decided. Based on the results of this study, it is expected many researches will be proceed in the future.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.04a
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• pp.181-188
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• 2000

This paper describes the energy absorption of a square tube under axi compression by using the finite element method. The overall deformations and lo buckling modes of tube was discussed by "plastic hinge concep Force-displacement function was plotted to show various state that depended or time. Also, mean crush load was expressed as a type of section geometry a material property using dimensional analysis. To verify the energy absorption and the effects of dimensions, The standards Wt used as related density and specific energy, mean crushing load and the resL were discussed by the relation between crush load and deformation, the relati between related density and specific energy, the relation between crush load a mean crush load, the relation between mean crush load and specific energy.ergy.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.162-169
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• 1999

Intentionally weakened girders near the beam-to-colum connection lead ductile failures at the weakened points prior to potential brittle failure at the connection points subjected to strong earthquake. Recent research investigated cyclic behavior of composite beams with a rectangular web opening and find out ductile failure of such beams due to plastic hinge formation of T-section at the four corners of the rectangular opening. But eventual failures of T-sections are resulted from local buckling of T-section having a narrow stem and a narrow bound of plastic hinge formation. This continuing research proposes double-circular opening instead of rectangular one in ofter to improve energy dissipation capacity as well as composite beam strength, Experimental test of two specimens was carried out and its results are compared with those of nonlinear finite element analyses

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.133-140
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• 1998

Material nonlinear analyses of RC(Reinforced Concrete) beams considering the tension stiffening effect and plastic hinge length have been conducted. Instead of taking the sophisticated layer approach which has some limitations in application to the large structures with many degrees of freedom. the moment-curvature relationships of RC sections previously constructed through the section analysis have been used. To reduce the numerical instability in nonlinear analysis and to remove the imprecision in calculation of ultimate resisting capacity, according to the used finite element mesh size, the tension stiffening effect and plastic hinge length have been taken into consideration. Finally, correlation studies between analytical and experimental results have been conducted with the objective to establish the validity of the proposed algorithms.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.4
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• pp.693-699
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• 2013

Environmental issues are attracting increasing interest worldwide, and accordingly, environmental regulations for vehicles are being made more stringent. As a result, the car industry is conducting studies focusing on fuel efficiency and lightweight vehicles. To manufacture lightweight vehicles, existing steel parts are replaced by composite materials and lightweight metals. In this study, the fatigue life of a new material for manufacturing lightweight car door hinges was predicted using a finite-element analysis program. The existing steel material was replaced by carbon-fiber-reinforced plastic (CFRP) and aluminum alloy 6061, and the test results were analyzed. The maximum stress decreased by approximately three times, whereas the fatigue life and safety factor increased. When only CFRP was used, its allowable stress, safety factor, and fatigue life were excellent, but the sagging of the product exceeded the allowable value, which posed a limitation in use. Therefore, it seems desirable to use an appropriate combination of steel, AA6061, and CFRP for this product.

• Structural Engineering and Mechanics
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• v.26 no.3
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• pp.263-276
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• 2007

Steel frame structures have been widely used in multi-storey and high-rise buildings and the connections in these structures are critical. In the Northridge and Kobe Earthquake, beam-column connections suffered damage due to brittle fracture. According to seismic design codes, ductility of the beam to column connection is also necessary. A study on the behavior of a beam to column connection with the aim of improving ductility as well as preventing brittle failure was carried out. In order to control the position of a plastic hinge on the beam, a connection with a hole in the beam web was developed. Five specimens with different parameters under cyclic load were assessed. The results are presented in terms of the stress distribution of the beam, hysteretic behavior, and ultimate capacity. Furthermore, the finite element method was also used to analyze the model, and the results were compared with those obtained from the experiment. It is shown from the analysis and experimental results that this type of connection is effective in terms of improving ductility for a beam to column connection in low-rise buildings.

• 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.