• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.21-32
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• 2004

In this study, a continuous optimum design model with its application program for plane steel frame structures developed. In the model, the sequential unconstrained minimization technique (SUMT) transforming the nonlinear optimization problem with multidesign variables and constraints into an unconstrained minimization problem and the refined plastic hinge analysis method as one of the most effective second-order inelastic analysis methods for steel frame structures were implemented. The total weight of a steel frame structure was taken as the objective function, and the AISC-LRFD code requirements for the local and member buckling, flexural strength, shear strength, axial strength and size of the cross-sectional shapes of members were used for the derivation of constraint equations. To verify the appropriateness of the present model, the optimum designs of serveral plane steel frame structures subject to vertical and horizontal loads were conducted.

• Journal of Korean Society of Steel Construction
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• v.21 no.5
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• pp.483-492
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• 2009

In this study, nonlinear analysis of steel plane frame was performed using the refined plastic hinge method of advanced analysis techniques. In deterioration of stiffness in plastic zone, influences by flexural bending, residual stress, geometrical non-linearity, and semi-rigid connection are considered. And also, further reduced tangent modulus was used for geometrical non-linearity, top and seat angle were chosen for semi-rigid connection. Furthermore, 3 parameter power model was used for moment-rotation behaviour of beam to column connection. The loading conditions are combined with axial and lateral force and the inverse triangle distribution of lateral and eight type of analytical models were used in analysis. The results of analyses were compared with semi-rigid and rigid connection on behaviour of numerical analysis models. And also, the behaviors of frame with changes of semi-rigidity were analyzed by using the results obtained from MIIDAS-GENw.

• Computational Structural Engineering
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• v.9 no.2
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• pp.103-113
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• 1996

This paper presents practical notional-load plastic-hinge method for a two-dimensional steel structure design. The proposed method incorporates the refined plastic-hinge concept for spread of plasticity together with a practical notional-load approach. The proposed method can assess realistically both strength and behavior of a structural system and its individual members in a direct manner. As a result, the method can be used for design without tedious separate member capacity checks, including the calculation of K-factor. The strengths predicted by the proposed method are then compared with those predicted by the exact plastic-zone analysis as well as by the conventional LRFD procedure. A good agreement is generally observed. The displacement predictions are compared with the plastic-zone solutions. Analysis and design guidelines in using the proporsed method are given in detail. Analysis and design procedures are recommended. Member sizes determined by the proposed method are compared with those determined by the LRFD method. It is concluded that the procedures are suitable for adoption in practice.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.3
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• pp.131-140
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• 2004

The main objective of the research is to develop an algorithm for the optimum design of two dimensional steel frames using refined plastic hinge analysis which considers material and geometrical nonlinearities. Using developed algorithm, an optimum design was perform without calculating an effective length factor of the column (K-factor). A multi-level discrete optimization technique with two parameters has been developed and employed in the optimum design algorithm. The optimization algorithm is applied to structural design with the objective of minimizing the weight of a structure and with constraints on load limit, frame drift, ductility. Various application example is provided to demonstrate the feasibility, validity and efficiency of the developed program.

• Journal of Korean Society of Steel Construction
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• v.12 no.3 s.46
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• pp.317-328
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• 2000

The objective of the research is to develop an algorithm for the optimum design of two-dimensional braced steel frames using an advanced analysis, which considers both material and geometric nonlinearties. Since both nonlinearties are considered in analysis process, Optimum design algorithm which does not require to calculate K-factor is presented. A multi-level discrete optimization technique with two parameters that uses the information of structural system and separate member has been developed. The structural analysis is performed by the relined plastic-hinge method which is based on zero-length plastic hinge theory. Optimization problem are formulated by AISC-LRFD code. The feasibility, validity and efficiency of the developed algorithm is demonstrated by the results of the braced steel frame.

• Structural Engineering and Mechanics
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• v.6 no.8
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• pp.871-882
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• 1998

This paper presents a new design method of truss bridges using advanced analysis. In this approach, separate member capacity checks encompassed by the specification equations are not required because the stability of separate members and the structure as a whole can be treated rigorously for the determination of the maximum strength of the structures. The method is developed and refined by modifications to the conventional elastic-plastic hinge method. Verification studies are carried out by comparing with the plastic-zone solutions. The load-deflection behavior of the truss shows a good agreement between the plastic-zone analysis. A case study is provided for a truss bridge. Member sizes determined by the proposed method are compared with those determined by the conventional method. It is concluded that the proposed method is suitable for adoption in practice.

• Journal of Korean Society of Steel Construction
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• v.13 no.5
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• pp.535-545
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• 2001

A refined method of analysis which is called the Advanced Analysis has been introduced This method is to consider the intial member imperfection residual stress and second-order effects so as to estimate the overall behavior of steel frame accurately Based on the refined plastic hinge method that is more suitable and practical in design practice. the program RPH-2DF is coded using the log model which represents the moment-rotation relationship of connection. The validity of this program is examined by frame test data. Finally to investigate the difference between behaviors of rigid and semi-rigid frame. the 10-story frame analysis results designed by MIDAS-GEN v4.2.2 are compared with the results by RPH-2DF.

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.10-22
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• 1998

In the present work the elastic-plastic FE formulations using dynamic explicit time integration schemes are used for numerical analysis of a large auto-body panel stamping processes. For analyses of more complex cases with larger and more refined meshes, the explicit method is more time effective than implicit method, and has no convergency problem and has the robust nature of contact and friction algorithms while implicit method is widely used because of excellent accuracy and reliability. The elastic-plastic scheme is more reliable and rigorous while the rigid-plastic scheme require small computation time. In finite element simulation of auto-body panel stamping processes, the roobustness and stability of computation are important requirements since the computation time and convergency become major points of consideration besides the solution accuracy due to the complexity of geometry conditions. The performnce of the dynamic explicit algorithms are investigated by comparing the simulation results of formaing of complicate shaped autobody parts, such as a fuel tank and a rear hinge, with the experimental results. It has been shown that the proposed dynamic explicit elastic-plastic finite element method enables an effective computation for complicated auto-body panel stamping processes.

• Earthquakes and Structures
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• v.15 no.4
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• pp.419-429
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• 2018

The seismic vulnerability analysis of multi-span bridges can be based on the response of the piers, provided that deck, bearings and foundations remain elastic. The lateral response of an RC bridge pier can be affected by different mechanisms (i.e., flexure, shear, lap-splice or buckling of the longitudinal reinforcement bars, second order effects). In the literature, simplified formulations are available for mechanisms different from the flexure. On the other hand, the flexural response is usually calculated with a numerically-based Moment-Curvature diagram of the base section and equivalent plastic hinge length. The goal of this paper is to propose a simplified analytical solution to obtain the Moment-Curvature relationship for hollow circular RC sections. This based on calibrated polynomials, fitted against a database comprising 720 numerical Moment-Curvature analyses. The section capacity curve is defined through the position of 6 characteristic points and they are based on four input parameters: void ratio of the hollow section, axial force ratio, longitudinal reinforcement ratio, transversal reinforcement ratio. A case study RC bridge pier is assessed with the proposed solution and the results are compared to a refined numerical FEM analysis, showing good match.

• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.327-335
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• 2011

This study has two objectives: (1) to evaluate the degradation characteristics of symmetric unbraced steel frames by using analytical approach, and (2) to suggest equation which can approximately estimate the effect of degradation during the schematic design stage. For the analytical approach, the refined plastic hinge method with an arc length algorithm was adopted. The subject of analysis was one story one-bay, multistory one-bay, and multistory three-bay unbraced steel frames. The main parameters of the analytical approach include the stiffness ratio of column to beam and the axial force ratio. The study led to the following conclusions. The normalized stiffness of degradations is affected by both stiffness ratio of column to beam and the axial load ratio; however, the major influence on degradations is the axial force ratio. The equation, which can approximately estimate the effect of degradation, was suggested together with the research results.