• Structural Engineering and Mechanics
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• v.12 no.1
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• pp.51-69
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• 2001

Whereas the potential of static inelastic analysis methods is recognised in earthquake design and assessment, especially in contrast with elastic analysis under scaled forces, they have inherent shortcomings. In this paper, critical issues in the application of inelastic static (pushover) analysis are discussed and their effect on the obtained results appraised. Areas of possible developments that would render the method more applicable to the prediction of dynamic response are explored. New developments towards a fully adaptive pushover method accounting for spread of inelasticity, geometric nonlinearity, full multi-modal, spectral amplification and period elongation, within a framework of fibre modelling of materials, are discussed and preliminary results are given. These developments lead to static analysis results that are closer than ever to inelastic time-history analysis. It is concluded that there is great scope for improvements of this simple and powerful technique that would increase confidence in its employment as the primary tool for seismic analysis in practice.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.75-80
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• 2000

Evaluation method of seismic performance has mainly used elastic spectrum analysis. This method has simplicity of analysis but deficiency of accuracy. And evaluation method of seismic performance using inelastic dynamic analysis reflects accurately inelasticity of material but hardly reflects site effects. This study suggested evaluation scheme of seismic performance for bridge structure using capacity spectrum method applied inelastic static analysis and standard design response spectrum of Korea Standard Specification for Highway Bridge. Two results, capacity spectrum method and inelastic dynamic analysis method, are very similar. As a result, this study appropriately supply both simplicity of analysis and accuracy of result.

• Earthquakes and Structures
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• v.9 no.3
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• pp.673-698
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• 2015

This paper investigates inelastic seismic demands of the normal component of near-fault pulse-like ground motions, which differ considerably from those of far-fault ground motions and also parallel component of near-fault ones. The results are utilized to improve the nonlinear static procedure (NSP) called Displacement Coefficient Method (DCM). 96 near-fault and 20 far-fault ground motions and the responses of various single degree of freedom (SDOF) systems constitute the dataset. Nonlinear Dynamic Analysis (NDA) is utilized as the benchmark for comparison with nonlinear static analysis results. Considerable influences of different faulting mechanisms are observed on inelastic seismic demands. The demands are functions of the strength ratio and also the pulse period to structural period ratio. Simple mathematical expressions are developed to consider the effects of near-fault motion and fault type on nonlinear responses. Modifications are presented for the DCM by introducing a near-fault modification factor, $C_N$. In locations, where the fault type is known, the modifications proposed in this paper help to obtain a more precise estimate of seismic demands in structures.

• Earthquakes and Structures
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• v.22 no.6
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• pp.571-584
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• 2022

The residual displacement ratio (RDRs) response spectra have been generally used as an important means to evaluate the post-earthquake repairability, and the ratios of residual to maximum inelastic displacement are considered to be more appropriate for development of the spectra. This methodology, however, assumes that the expected residual displacement can be computed as the product of the RDRs and maximum inelastic displacement, without considering the correlation between these two variables, which inevitably introduces potential systematic error. For providing an adequately accurate estimate of residual displacement, while accounting for the collapse resistance performance prior to the repairability evaluation, a probability-based procedure to estimate the residual displacement demands using the nonlinear static analysis (NSA) is developed for single-degree-of-freedom (SDOF) systems. To this end, the energy-based equivalent damping ratio used for NSA is revised to obtain the maximum displacement coincident with the nonlinear time history analysis (NTHA) results in the mean sense. Then, the possible systematic error resulted from RDRs spectra methodology is examined based on the NTHA results of SDOF systems. Finally, the statistical relation between the residual displacement and the NSA-based maximum displacement is established. The results indicate that the energy-based equivalent damping ratio will underestimate the damping for short period ranges, and overestimate the damping for longer period ranges. The RDRs spectra methodology generally leads to the results being non-conservative, depending on post-yield stiffness. The proposed approach emphasizes that the repairability evaluation should be based on the premise of no collapse, which matches with the current performance-based seismic assessment procedure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.971-976
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• 2006

This paper presents a design technique of steel structures subjected to static and dynamic loadings using practical nonlinear inelastic analysis software. The beam-column approach using the stability functions and the plastic hinge concept enables the software to suitably predict second-order effects and inelastic behavior of beam-columns. For dynamic analysis. the incremental from of the equation of motion is solved by the use of a step-by-step numerical integration procedure in which the assumption of constant acceleration over a small time step is employed. The accuracy of the analysis program is validated using the results of ABAQUS program and experimental tests. A user-friendly graphic interface of the software is developed to facilitate the modeling process and result interpretation of the problem. A design example of large span bridge is presented to detail the direct design process using the practical advanced analysis software.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.53-60
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• 2002

It has been recognized that damage control must become a more explicit design consideration. In an effort to develop design methods based on performance it is clear that the evaluation of the inelastic response is required. The methods available to the design engineer today are nonlinear time history analyses, or monotonic static nonlinear analyses, or equivalent static analyses with simulated inelastic influences. Some codes proposed the capacity spectrum method based on the nonlinear static(pushover) analysis to determine earthquake-induced demand given the structure pushover curve. This procedure is conceptually simple but iterative and time consuming with some errors. This paper presents a nonlinear direct spectrum method to evaluate seismic Performance of structure, without iterative computations, given the structural initial elastic period and yield strength from the pushover analysis, especially for multi degree of freedom structures. The purpose of this paper is to investigate accuracy and confidence of this method from a point of view of various earthquakes and unloading stiffness degradation parameters.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.27-34
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• 2003

Capacity Spectrum Method (CSM) defined in ATC-40 or FEMA-273 is a most widely used static inelastic analysis method to evaluate the performance level of the existing structures. In CSM, however, uncertainties and errors exist when lateral forces such as earthquake and wind loads are analyzed into equivalent static loads. This paper examines the accuracy of CSM for different structural parameters, such as natural frequency, yield strength and hardening ratio, and various soil conditions by comparing the estimated values to exact solutions obtained by time history analysis. Results indicate that the accuracy of CSM, in general, is influenced mostly by hardening ratio.

• Steel and Composite Structures
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• v.8 no.1
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• pp.53-83
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• 2008

A rational and efficient seismic design methodology for irregular space steel frames using advanced methods of analysis in the framework of Eurocodes 8 and 3 is presented. This design methodology employs an advanced static or dynamic finite element method of analysis that takes into account geometrical and material non-linearities and member and frame imperfections. The inelastic static analysis (pushover) is employed with multimodal load along the height of the building combining the first few modes. The inelastic dynamic method in the time domain is employed with accelerograms taken from real earthquakes scaled so as to be compatible with the elastic design spectrum of Eurocode 8. The design procedure starts with assumed member sections, continues with the checking of the damage and ultimate limit states requirements, the serviceability requirements and ends with the adjustment of member sizes. Thus it can sufficiently capture the limit states of displacements, rotations, strength, stability and damage of the structure and its individual members so that separate member capacity checks through the interaction equations of Eurocode 3 or the usage of the conservative and crude q-factor suggested in Eurocode 8 are not required. Two numerical examples dealing with the seismic design of irregular space steel moment resisting frames are presented to illustrate the proposed method and demonstrate its advantages. The first considers a seven storey geometrically regular frame with in-plan eccentricities, while the second a six storey frame with a setback.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.3
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• pp.37-44
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• 1997

In this paper, the inelastic behavior of an asymmetric tall building is investigated. The asymmetry in rigidity caused by the structural asymmetry induces torsional as well as lateral deformation. The inelastic analysis of such an asymmetric structure is difficult to carry out with a planar model and thus requires a full three dimensional model. In this paper a 102 story unsymmetric tall building is analized by static push-over procedure and its behavior is investigated. The analysis are performed with and without floor rotation to compare the results. According to the results the static behavior of the model building, as expected, turned out to be dependent heavily an the asymmetry of the plan shapes of the building.

• Structural Engineering and Mechanics
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• v.75 no.2
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• pp.145-155
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• 2020

This paper investigates the influence of spatial varations of accidental mass eccentricities on the torsional response of inelastic multistorey reinforced concrete buildings. It complements recent studies on the elastic response of structural buildings and extends the investigation into the inelastic range, with the aim of providing guidelines for minimising the torsional response of structural buildings. Four spatial mass eccentricity configurations of common nine story buildings, along with their reversed mass eccentricities subjected to the Erzincan-1992 and Kobe-1995 ground motions were investigated, and the results are discussed in the context of the structural response of the no eccentricity models. It is demonstrated that when the initial linear response is practically translational, it is maintained into the inelastic phase of deformation as long as the strength assignment of the lateral resisting bents is based on a planar static analysis where the applied lateral loads simulate the first mode of vibration of the uncoupled structure.