• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.71-78
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• 2005

In performance-based design methods, it is clear that the evaluation of the nonlinear response is required. The methods available to the design engineer today are nonlinear tim history analyses, or monotonic static nonlinear analyses, or equivalent static analyses with simulated inelastic influences. The nonlinear time analysis is the most accurate method in computing the nonlinear response of structures, but it is time-consuming and necessitate more efforts. Some codes proposed the capacity spectrum method based on the nonlinear static analysis to determine earthquake-induced demand given the structure pushover curve. This procedure is conceptually simple but iterative and time consuming with some errors. The nonlinear direct spectrum method is proposed and studied to evaluate nonlinear response of structures, without iterative computations, given by the structural linear vibration period and yield strength from the pushover analysis. The purpose of this paper is to compare the accuracy and the reliability of approximate nonlinear methods with respect to RC dual system and various earthquakes.

• Structural Engineering and Mechanics
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• v.41 no.2
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• pp.243-262
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• 2012

Nonlinear static analysis as an essential part of performance based design is now widely used especially at design offices because of its simplicity and ability to predict seismic demands on inelastic response of buildings. Since the accuracy of nonlinear static procedures (NSP) to predict seismic demands of buildings affects directly on the entire performance based design procedure, therefore lots of research has been performed on the area of evaluation of these procedures. In this paper, one of the popular NSP, FEMA356, is evaluated and compared with modal pushover analysis. The ability of these procedures to simulate seismic demands in a set of reinforced concrete (RC) buildings is explored with two level of base acceleration through a comparison with benchmark results determined from a set of nonlinear time history analyses. According to the results of this study, the modal pushover analysis procedure estimates seismic demands of buildings like inter story drifts and hinges plastic rotations more accurate than FEMA356 procedure.

• Journal of Korean Society of Steel Construction
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• v.17 no.4 s.77
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• pp.469-479
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• 2005

The nonlinear behavior of a connection has an influence on the behavior (the $P-\Delta$ effect) and the stability of a steel unbraced frame when a semi-rigid connection is applied as a beam-to-column connection. Therefore, the effects of a connection's non-linear behavior on the behavior and stability of a steel unbraced frame were investigated using second-order inelastic analysis, after which the main influence factors and their behavioral tendencies were studied. The study results showed that the nonlinear behavior of a connection directly affects the stability of a steel unbraced frame, and that the main influence factors are the rotational stiffness of the connection and the location of a semi-rigid connection.

• Computers and Concrete
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• v.14 no.6
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• pp.695-710
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• 2014

This paper presents a theoretical and computational approach to solve inelastic structures subjected to overloads. Current practice in structural design is based on elastic analysis followed by limit strength design. Whereas this approach typically results in safe strength design, it does not always guarantee satisfactory performance at the service level because the internal stiffness distribution of the structure changes from the service to the ultimate strength state. A significant variation of relative stiffnesses between the two states may result in unwanted cracking at the service level with expensive repairs, while, under certain circumstances, early failure may occur due to unexpected internal moment reversals. To address these concerns, a new inelastic model is presented here that is based on the nonlinear material response and the interaction relation between axial forces and bending moments of a beam-column element. The model is simple, reasonably accurate, and computationally efficient. It is easy to implement in standard structural analysis codes, and avoids the complexities of expensive alternative analyses based on 2D and 3D finite-element computations using solid elements.

• Steel and Composite Structures
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• v.4 no.6
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• pp.419-435
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• 2004

The safety level of a structural system designed per code specifications can not be inferred directly from the reliability of members due to the load redistribution and nonlinear inelastic structural behavior. Comparison of the system and member reliability, which is scarce in the literature, is likely to indicate any possible inconsistency of design codes in providing safe and economical designs. Such a comparative study is presented in this study for moment resisting two-dimensional steel frames designed per AISC LRFD Specifications. The member reliability is evaluated using the resistance of the beam-column element and the elastic load effects that indirectly accounts for the second-order effects. The system reliability analysis is evaluated based on the collapse load factor obtained from a second-order inelastic analysis. Comparison of the system and member reliability is presented for several steel frames. Results suggest that the failure probability of the system is about one order of magnitude lower than that of the most critically loaded structural member, and that the difference between the system and member reliability depends on the structural configuration, degree of redundancy, and dead to live load ratio. Results also suggest that the system reliability is less sensitive to initial imperfections of the structure than the member reliability. Therefore, the system aspect should be incorporated in future design codes in order to achieve more reliability consistent designs.

• Computational Structural Engineering
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• v.5 no.1
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• pp.83-89
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• 1992

A practical method of estimating inelastic deflection of reinforced concrete slab under service load is presented. Based on the elastic results of linear finite element analysis and area of reinforcement, inelastic deflection multiplier(.betha.) is evaluated and desired deflection as a measure of serviceability of the designed slab is obtained. Example for the corner supported slab shows that the results from the proposed method agree well with those from the experiment/and nonlinear finite element analysis. Application of the method to the design of irregular slab is also considered.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.1
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• pp.137-146
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• 1999

Analysis of R/C columns requires modeling of the plastic hinge region, as well as nonlinear material characteristics. This becomes a challenging task in view of the nonlinearity of both steel and concrete. Furthermore, formation and progression of plasticity in the hinge is a difficult phenomenan to simulate, especially under reversed cyclic loading and decaying strength conditions. This research provide one analytical model employed in column analysis, including the analysis procedure for establishing inelastic force-deformation relationships. The analytical results show good correlation with experimental data. The employed procedure with the adopted analytical models can be used to compute inelastic displacements of concrete columns with welded reinforcement grids. The inelastic deformability beyond the peak was similar to those indicated by columns with conventional ties. The superior performance of columns with welded grids may be attributed to the improved confinement characteristics of grids associated with increased rigidity of welded ties.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.292-299
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• 2006

The purpose of this study is to investigate the inelastic behavior of precast segmental prestressed concrete bridge columns. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. An unbonded tendon element based on the finite element method, that can represent the interaction between tendon and concrete of prestressed concrete member, is used. A joint element is newly developed to predict the inelastic behaviors of segmental joints. The proposed numerical method for the inelastic behavior of precast segmental prestressed concrete bridge columns is verified by comparison with reliable experimental results.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.931-936
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• 2003

Lap splices were located in the plastic hinge region of most bridge piers that were constructed before the adoption of the seismic design provision of Korea Highway Design Specification on 1992. Lap splicing is also permitted if hoops or spiral reinforcement are provided over the lap length in the current seismic design provision. But sudden brittle failure of lap splices may occur under inelastic cyclic loading. The purpose of this study is the analytical prediction of nonlinear hysteretic behavior and ductility capacity of reinforced concrete bridge piers with lap splices under cyclic loading. For this purpose, a nonlinear analysis program, RCAHEST(Reinforced Concrete Analysis in Higher Evaluation System Technology) is used. Lap spliced bar element is developed to predict behaviors of lap spliced bar. Maximum bar stress and slip of lap spliced bar is considered.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.37-46
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• 2007

This is the second of two companion papers that describe non-prismatic beam element for nonlinear seismic analysis of steel moment frames. Described in a companion paper is the formulation of a non-prismatic beam element to model the elastic and inelastic behavior of steel beams, which have reduced beam sections(RBS). This study describes the determination of yield surfaces, stiffness parameters, and hardening (or softening) rule parameters for RBS beam element. Analytical results of the RBS beam element show good correlation with test data and Finite Element Method(FEM) results.