• 한국터널지하공간학회 논문집
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• 제20권6호
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• pp.973-987
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• 2018

대부분의 기존 내진해석은 지반과 구조물을 각각 구분하여 수행되었고, 초고층 건물과 저층 건물에 대한 동적거동 비교 연구가 부족한 실정이다. 따라서 본 연구에서는 초고층 건물과 저층 건물의 동적거동을 파악하기 위하여 유한요소해석 프로그램을 이용하여 선정된 파라미터별로 민감도 분석을 실시하였다. 연구 결과, 초고층 건물의 수평변위, 층간변위비, 휨응력은 지반조건이 연약할수록, 저층 건물보다 장주기 지진파의 영향을 더 받는것으로 나타났다. 또한 초고층과 저층 건물의 취약부는 지반조건보다는 지진파의 종류의 영향이 더 큰 것으로 나타났다. 따라서 지반조건 및 지진파 종류가 건물에 미치는 영향을 참고하면 건물의 내진설계에 도움이 될 것으로 판단된다.

• Structural Engineering and Mechanics
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• 제53권5호
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• pp.1031-1049
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• 2015

This paper highlights the role of innovative vibration control system based on two promising properties in a parallel configuration. Hybrid device consists of two main components; recentering wires of shape memory alloy (SMA) and steel pipe section as an energy dissipater element. This approach concentrates damage in the steel pipe and prevents the main structural members from yielding. By regulation of the main adjustable design parameter, an optimum performance of the device is obtained. The effectiveness of the device in passive control of structures is evaluated through nonlinear time history analyses of a five-story steel frame with and without the hybrid device. Comparing the results proves that the hybrid device has a considerable potential to mitigate the residual drift ratio, peak absolute acceleration and peak interstory drift of the structure.

• Earthquakes and Structures
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• 제3권6호
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• pp.869-887
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• 2012

Ground motion scaling techniques are actively debated in the earthquake engineering community. Considerations such as what amplitude, over what period range and to what target spectrum are amongst the questions of practical importance. In this paper, the effect of various ground motion scaling approaches are explored using three reinforced concrete prototypical building models of 8, 12 and 20 stories designed to respond nonlinearly under a design level earthquake event in the seismically active Southern California region. Twenty-one recorded earthquake motions are selected using a probabilistic seismic hazard analysis and subsequently scaled using four different strategies. These motions are subsequently compared to spectrally compatible motions. The nonlinear response of a planar frameidealized building is evaluated in terms of plasticity distribution, floor level acceleration and uncorrelated acceleration amplification ratio distributions; and interstory drift distributions. The most pronounced response variability observed in association with the scaling method is the extent of higher mode participation in the nonlinear demands.

• Structural Engineering and Mechanics
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• 제65권3호
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• pp.251-261
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• 2018

Self-centering concentrically braced frames (SCCBFs) are emerging as high performance seismically resistant braced framing system, due to the capacity of withstanding strong earthquake attacks and promptly recovering after events. To get a further insight into the seismic performance of SCCBFs, systematical evaluations are currently conducted from the perspective of modal contributions. In this paper, the modal pushover analysis (MPA) approach is utilized to obtain the realistic seismic demands by summarizing the contribution of each single vibration mode. The MPA-based results are compared with the exact results from nonlinear response history analysis. The adopted SCCBFs originate from existing buckling-restrained braced frames (BRBF), which are also analyzed for purpose of comparison. In the analysis of these comparable framing systems, interested performance indices that closely relate to the structural damage degree include the interstory drift ratio, floor acceleration, and absorbed hysteretic energy. The study shows that the MPA approach produces acceptable predictions in comparison to the exact results for SCCBFs. In addition, the high-modes effect on the seismic behavior increases with the building height, and is more evident in the SCCBFs than the BRBFs.

• Structural Engineering and Mechanics
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• 제76권6호
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• pp.781-797
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• 2020

In recent years, there is an increasing interest to optimize the fuzzy logic controller with different methods. This paper focuses on the optimization of a fuzzy logic controller applied to a seismically excited nonlinear building. In most cases, this problem is formulated based on the linear behavior of the structure, however in this paper, four sets of objective functions are considered with respect to the nonlinear responses of the structure as the peak interstory drift ratio, the peak level acceleration, the ductility factor and the maximum control force. The Improved Charged System Search is used to optimize the membership functions and the rule base of the fuzzy controller. The obtained results of the optimized and the non-optimized fuzzy controllers are compared to the uncontrolled responses of the structure. Also, the performance of the utilized method is compared with various classical and advanced optimization algorithms.

• Structural Engineering and Mechanics
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• 제46권6호
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• pp.755-773
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• 2013

One of the main requirements of the seismic design codes must be its easy application by structural engineers. The use of practically-applicable models or simplified models as single-degree-of-freedom (SDOF) systems is a good alternative to achieve this condition. In this study, deterministic and probabilistic response transformation factors are obtained to evaluate the response in terms of maximum ductility and maximum interstory drifts of multi-degree-of-freedom (MDOF) systems based on the response of equivalent SDOF systems. For this aim, five steel frames designed with the Mexican City Building Code (MCBC) as well as their corresponding equivalent SDOF systems (which represent the characteristics of the frames) are analyzed. Both structural systems are subjected to ground motions records. For the MDOF and the simplified systems, incremental dynamic analyses IDAs are developed in first place, then, structural demand hazard curves are obtained. The ratio between the IDAs curves corresponding to the MDOF systems and the curves corresponding to the simplified models are used to obtain deterministic response transformation factors. On the other hand, demand hazard curves are used to calculate probabilistic response transformation factors. It was found that both approaches give place to similar results.

• Structural Engineering and Mechanics
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• 제87권5호
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• pp.405-418
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• 2023

This study focused on the effectiveness of seismic isolation technique in case of a reinforced concrete structure with soft story defined as the stiffness irregularity between adjacent stories. In this context, a seismically isolated 3-story reinforced concrete structure was analyzed by gradually increasing the first story height (3.0, 4.5, and 6.0 m). The seismic isolation system of the structure is assumed to be composed of lead rubber bearings (LRB). In the analyses, isolators were modeled by both deteriorating (temperature-dependent analyses) and non-deteriorating (bounding analyses) hysteretic representations. The deterioration in strength of isolator is due to temperature rise in the lead core during cyclic motion. The ground motion pairs used in bi-directional nonlinear dynamic analyses were selected and scaled according to codified procedures. In the analyses, different isolation periods (Tiso) and characteristic strength to weight ratios (Q/W) were considered in order to determine the sensitivity of structural response to the isolator properties. Response quantities under consideration are floor accelerations, and interstory drift ratios. Analyses results are compared for both hysteretic representations of LRBs. Results are also used to assess the significance of the ratio between the horizontal stiffnesses of soft story and isolation system. It is revealed that seismic isolation is a viable method to reduce structural damage in structures with soft story.

• Steel and Composite Structures
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• 제49권3호
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• pp.257-270
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• 2023

In this study, the feasibility and applicability of a friction damper with a vertical installation scheme are investigated. This device is composed of a steel section and two friction hinges at both ends which dissipate seismic energy. Due to its small width and vertical installation scheme, the proposed damper can minimize the interference with architectural functions. To evaluate the performance of the proposed damper, its mechanical behavior is theoretically evaluated and the required formulas for the yield strength and elastic stiffness are derived. The theoretical formulas are verified by establishing the analytical model of the damper in the SAP2000 software and comparing their results. To further investigate the performance of the developed damper, the provided analytical model is applied to a 4-story reinforced concrete (RC) structure and its performance is evaluated before and after retrofit under the Maximum Considered Earthquake (MCE) hazard level. The seismic performance is thoroughly evaluated in terms of maximum interstory drift ratio, displacement time history, residual displacement, and energy dissipation. The results show that the proposed damper can be efficiently used to protect the structure against seismic loads.

• Steel and Composite Structures
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• 제43권2호
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• pp.139-152
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• 2022

Steel-reinforced concrete (SRC) L-shaped column is the vertical load-bearing member with high spatial adaptability. The seismic behavior of SRC L-shaped column is complex because of their irregular cross sections. In this study, the hysteretic performance of six steel truss reinforced concrete L-shaped columns specimens under the combined loading of compression, bending, shear, and torsion was tested. There were two parameters, i.e., the moment ratio of torsion to bending (γ) and the aspect ratio (column length-to-depth ratio (φ)). The failure process, torsion-displacement hysteresis curves, and bending-displacement hysteresis curves of specimens were obtained, and the failure patterns, hysteresis curves, rigidity degradation, ductility, and energy dissipation were analyzed. The experimental research indicates that the failure mode of the specimen changes from bending failure to bending-shear failure and finally bending-torsion failure with the increase of γ. The torsion-displacement hysteresis curves were pinched in the middle, formed a slip platform, and the phenomenon of "load drop" occurred after the peak load. The bending-displacement hysteresis curves were plump, which shows that the bending capacity of the specimen is better than torsion capacity. The results show that the steel truss reinforced concrete L-shaped columns have good collapse resistance, and the ultimate interstory drift ratio more than that of the Chinese Code of Seismic Design of Building (GB50011-2014), which is sufficient. The average value of displacement ductility coefficient is larger than rotation angle ductility coefficient, indicating that the specimen has a better bending deformation resistance. The specimen that has a more regular section with a small φ has better potential to bear bending moment and torsion evenly and consume more energy under a combined action.

• 한국강구조학회 논문집
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• 제23권2호
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• pp.147-158
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• 2011

본 연구의 목적은 국내 강구조 성능기반설계를 위한 접합부의 내진성능평가치를 제안하는 것에 있다. 최근 성능설계에 대한 기초연구가 국내, 외에서 증가하고 있으며, 본 연구에서는 외국의 성능설계기법을 조사, 분석하여 강구조 건축물의 성능한계분류를 제안하였다. 제안된 성능한계분류에 따라 강구조에 적합한 공학량으로서 내진성능규정치를 제시할 필요가 있다. 그 첫 번째 단계로 강구조 실대형 실험을 통한 접합부의 실험결과를 중심으로 기초자료를 조사하여 작성하였다. 모멘트 골조 접합부의 실험 데이터에서 얻은 모멘트-회전각 관계를 이용하여 항복하중 이하에 존재할 것으로 판단되는 기능한계와 손상한계는 층간변형각으로 구분하였다. 또한 항복하중과 최대하중 사이에 존재할 것으로 판단되는 복구한계와 안전한계는 소성율과 누적소성변형배율을 조사하여 구분하였다.