• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2003년도 추계 학술발표회논문집
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• pp.205-212
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• 2003

To evaluate the seismic performance of multistory building structures use an equivalent SDOF model. This paper presents a method of converting a MDOF system into an equivalent SDOF model. The principal objective of this investigation is to evaluate appropriateness of converting method through perform nonlinear time history analysis of a multistory building structures and an equivalent SDOF model. The hysteresis rules to be used an equivalent SDOF model is obtained from the pushover analysis. The conclusion of this study is following; A method of converting a MDOF system into an equivalent SDOF model through the nonlinear time history response analysis is valid. The representative lateral displacement of a moment resisting reinforced concrete frames is close to the height of the first modal participation vector $_1$$\beta$｛$_1$u｝=1. It can be found that the hysteresis rule of an equivalent SDOF model have influence on the time history response. Therefore, it is necessary for selecting hysteresis rules to consider hysteresis characteristics of a moment resisting reinforced concrete frames.

• Steel and Composite Structures
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• 제14권6호
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• pp.621-636
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• 2013

Response modification factor is one of the seismic design parameters to consider nonlinear performance of building structures during strong earthquake, in conformity with the point that many seismic design codes led to reduce the loads. In the present paper it's tried to evaluate the response modification factors of dual moment resistant frame with buckling restrained braced (BRB). Since, the response modification factor depends on ductility and overstrength; the nonlinear static analysis, nonlinear dynamic analysis and linear dynamic analysis have been done on building models including multi-floors and different brace configurations (chevron V, invert V, diagonal and X bracing). The response modification factor for each of the BRBF dual systems has been determined separately, and the tentative value of 10.47 has been suggested for allowable stress design method. It is also included that the ductility, overstrength and response modification factors for all of the models were decreased when the height of the building was increased.

• Earthquakes and Structures
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• 제21권5호
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• pp.461-475
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• 2021

Strategic structures are a potential target of the growing terrorist attacks, so their performance under explosion hazard has been paid attention by researchers in the last years. In this regard, the aim of this study is to evaluate the blast-resistance performance of lead-rubber bearing (LRB) base isolation system based on a probabilistic framework while uncertainties related to the charge weight and standoff distance have been taken into account. A sensitivity analysis is first performed to show the effect of explosion uncertainty on the response of base-isolated buildings. The blast fragility curve is then developed for three base-isolated steel moment-resisting buildings with different heights of 4, 8 and 12 stories. The results of sensitivity analysis show that although LRB has the capability of reducing the peak response of buildings under explosion hazard, this control system may lead to increase in the peak response of buildings under some explosion scenarios. This shows the high importance of probabilistic-based assessment of isolated structures under explosion hazard. The blast fragility analysis shows effective performance of LRB in mitigating the probability of failure of buildings. Therefore, LRB can be introduced as effective control system for the protection of buildings from explosion hazard regarding uncertainty effect.

• Earthquakes and Structures
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• 제7권3호
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• pp.271-294
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• 2014

In recent years, along with the advances made in performance-based design optimization, the need for fast calculation of response parameters in dynamic analysis procedures has become an important issue. The main problem in this field is the extremely high computational demand of time-history analyses which may convert the solution algorithm to illogical ones. Two simplifying strategies have shown to be very effective in tackling this problem; first, simplified nonlinear modeling investigating minimum level of structural modeling sophistication, second, wavelet analysis of earthquake records decreasing the number of acceleration points involved in time-history loading. In this paper, we try to develop an efficient framework, using both strategies, to solve the performance-based multi-objective optimal design problem considering the initial cost and the seismic damage cost of steel moment-frame structures. The non-dominated sorting genetic algorithm (NSGA-II) is employed as the optimization algorithm to search the Pareto optimal solutions. The constraints of the optimization problem are considered in accordance with Federal Emergency Management Agency (FEMA) recommended design specifications. The results from numerical application of the proposed framework demonstrate the capabilities of the framework in solving the present multi-objective optimization problem.

• Earthquakes and Structures
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• 제17권1호
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• pp.1-15
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• 2019

In the structures with high level of ductility, the earthquake energy dissipation in structural components is an important factor that describes their seismic behavior. Since the connection details play a major role in the ductile behavior of structure, in this paper, the seismic response of 3-, 5- and 8-story steel special moment frames (SMFs) is investigated by considering the effects of panel zone modeling and the influence of forward-directivity near-field ground motions. To provide a reasonable comparison, selected records of both near and far-field are used in the nonlinear time-history analysis of models. The results of the comparison of the median maximum inter-story drift under excitation by near-field (NF) records and the far-field (FF) ground motions show that the inter-story drift demands can be obtained 3.47, 4.86 and 5.92 times in 3-, 5- and 8-story structures, respectively, undergoing near-field earthquakes.

• 한국공간구조학회논문집
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• 제11권4호
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• pp.37-47
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• 2011

재하속도에 따른 용접강관의 모멘트-곡률 거동특성에 관한 해석적 연구를 수행하였다. 3차원 열역학해석을 통하여 용접이음부의 잔류응력을 산출하였다. 그리고 동적소성모델이 적용된 탄소성 유한요소해석 프로그램을 이용하여 잔류응력을 고려한 용접강관(Welded pipe)의 동적해석을 수행하였다. 그리고 용접이음부가 없는 일반강관(Seamless pipe)에 대한 동적거동과의 비교를 통하여 해석을 수행하여 용접강관의 해석력과 해석결과는 용접강관의 모멘트가 일반강관의 모멘트에 비해 낮은 응답을 보였으나 재하속도가 증가함에 따라 모멘트 응답의 차이는 점차 감소하는 경향을 보였다.

• Steel and Composite Structures
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• 제6권3호
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• pp.203-219
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• 2006

One of the most promising ways through which a steel moment frame may attain high energy dissipating capability is to trim off a portion of the beam flanges near the column face. This type of moment connection, known as Reduced Beam Section (RBS) connection, has notable superiority in comparison with other moment connection types. As the result of the advantages of RBS moment connection, it has widely being used in practice. In spite of the good hysteretic behaviour, an RBS beam suffers from an undesirable drawback, which is local and lateral instability of the beam. The instability in the RBS beam reduces beam load-carrying capacity. This paper aims to investigate key issues influencing cyclic behaviour of RBS beams. To this end, a numerical analysis was conducted on a series of steel subassemblies with various geometric properties. The obtained results together with the existing experimental data are used to study the instability of RBS beams. A new slenderness concept is presented to control an RBS beam for combined local and lateral instability. This concept is in good agreement with the numerical and experimental results. Finally, a model is developed for the prediction of the magnitude of moment degradation owing to the instability of an RBS beam.

• Structural Engineering and Mechanics
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• 제74권2호
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• pp.201-214
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• 2020

This study aims at evaluating composite moment frame structures (CFS) using wavelet analysis of the displacement behavior of these structures. Five seismic damage mitigation systems' models of 9-story CFS are examined namely, basic (Model 1), reinforced (Model 2), buckling restrained braced (BRB) (Model 3), lead rubber bearing (LRB) (Model 4), and composite (Model 5) moment frames. A novel integration between continuous and discrete wavelet transforms is designed to estimate the wavelet power energy and variance of measurements' behaviors. The behaviors of the designed models are evaluated under influence of four seismic loads to study the dynamic performance of CFS in the frequency domain. The results show the behaviors of models 3 and 5 are lower than other models in terms of displacement and frequency performances. Model 3 has been shown lower performances in terms of energy and variance wavelets along the monitoring time; therefore, Model 3 demonstrates superior performance and low probability of failure under seismic loads. Furthermore, the wavelet variance analysis is shown a powerful tool that can be used to assess the CFS under seismic hazards.

• 복합신소재구조학회 논문집
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• 제3권3호
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• pp.9-21
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• 2012

Concrete filled steel tube (CFT) columns have been widely used in moment resisting frame structures both in seismic zones. This paper discusses the design of such members based on the advanced methods introduced in the 2005 AISC Specification and the 2005 Seismic Provisions. This study focuses particularly on design following both linear and nonlinear methods utilizing equivalent static and dynamic loads for low-rise moment frames. The paper begins with an examination of the significance of pseudo-elastic design interaction equations and the plastic ductility demand ratios due to combined axial compressive force and bending moment in CFT members. Based on advanced computational simulations for a series of five-story composite moment frames, this paper then investigates both building performance and new techniques to evaluate building damage during a strong earthquake. It is shown that 2D equivalent static analyses can provide good design approximations to the force distributions in moment frames subjected to large inelastic lateral loads. Dynamic analyses utilizing strong ground motions generally produce higher strength ratios than those from equivalent static analyses, but on more localized basis. In addition, ductility ratios obtained from the nonlinear dynamic analysis are sufficient to detect which CFT columns undergo significant deformations.

• 한국해양공학회지
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• 제6권2호
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• pp.103-112
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• 1992

The calculation method which takes into account the shear lag effects on the ultimate transverse bending moment of a SWATH(Small Waterplane Area Twin Hull) ship has been developed. In case of the ultimate bending strength analysis of conventional monohull ships and general box girder structures, the hypothesis that plane section remains plane after bending can be employed but not in the case of the structures having wide flange. For the ultimate bending strength analysis of such structures, a new method which can take into account the effect of shear lag on the ultimate bending strength has been developed by adopting more reasonable assumption that warping distortion of the section takes place inthe same way as the actual stress distribution. Finally, the proposed method has been applied to a a SWATH cross deck structure.