• Title, Summary, Keyword: modification factor

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An Improvement for Determining Response Modification Factor in Bridge Load Rating (응력보정계수 산정 방법 개선)

  • Koo, Bong-Kuen;Shin, Jae-In;Lee, Sang-Soon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.5 no.1
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    • pp.169-175
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    • 2001
  • Bridge load rating calculations provide a basis for determining the safe load capacity of bridge. Load rating requires engineering judgement in determining a rating value that is applicable to maintaining the safe use of the bridge and arriving at posting and permit decisions. Load testing is an effective means in calculating the rating value of bridge. In Korea, load carrying capacity of bridge is modified by response modification factor that is determined from comparisons of measured values and analysis results. The response modification factor may be corrupted by vehicle location error that is defined as the gap of test vehicle location between load testing and analysis. In this study, the effects of vehicle location error to structural response and response modification factor are investigated, and a new method for evaluating response modification factor is proposed. The random data analysis shows that the proposed method is less sensitive to vehicle location error than the present method.

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Evaluation of Response Modification Factore for Earthquake Resistant Design of Moment-Resisting Steel Frames (모멘트-연성 강구조물의 내진설계를 위한 반응수정계수의 평가)

  • 송종걸
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.201-208
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    • 1997
  • In most seismic codes such as the Uniform Building Code(UBC), the response modification factor(or the force reduction factor)is used to reflect the capability of a structure in dissipating energy through inelastic behavior. The response modification factor is assigned according to structural system type. Ductile systems such as special moment-resisting steel frames are assigned larger values of the response modification factor, and are consequently designed for smaller seismic design forces. Therefore, structural damage may occur during a severe earthquake. To ensure safety of the structures, the suitability of the response modification factor used in aseismic design procedures shall be evaluated. The object of this study is to develop a method for the evaluating of the response modification factor. The validity of the evaluating method has been examined for several cases of different structures and different earthquake excitations.

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Study on the Response Modification Factor for a Lightweight Steel Panel-Modular Structure Designed as a Dual Frame System (이중골조시스템으로 설계된 복강판-모듈러 구조물의 반응수정계수에 관한 연구)

  • Lee, Eo-Jin;Hong, Sung-Gul
    • Journal of the Earthquake Engineering Society of Korea
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    • v.15 no.1
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    • pp.39-48
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    • 2011
  • In this present study, a response modification factor for a lightweight steel panel-modular system which is not clarified in a current building code was proposed. As a component of the response modification factor, an over-strength factor and a ductility factor were drawn from the nonlinear static analysis curves of the systems modeled on the basis of the performance tests. The final response modification factor was then computed by modifying the previous response modification factor with a MDOF (Multi-Degree-Of-Freedom) base shear modification factor considering the MDOF dynamic behaviors. As a result of computation for the structures designed as a dual frame system, ranging from 2-story to 5-story, the value of 4 was estimated as a final response modification factor for a seismic design, considering the value of 5 as an upper limit of the number of stories.

Response modification factor of dual moment-resistant frame with buckling restrained brace (BRB)

  • Abdollahzadeh, Gholamreza;Banihashemi, Mohammadreza
    • Steel and Composite Structures
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    • v.14 no.6
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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.

Design parameter dependent force reduction, strength and response modification factors for the special steel moment-resisting frames

  • Kang, Cheol Kyu;Choi, Byong Jeong
    • Steel and Composite Structures
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    • v.11 no.4
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    • pp.273-290
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    • 2011
  • In current ductility-based earthquake-resistant design, the estimation of design forces continues to be carried out with the application of response modification factors on elastic design spectra. It is well-known that the response modification factor (R) takes into account the force reduction, strength, redundancy, and damping of structural systems. The key components of the response modification factor (R) are force reduction ($R_{\mu}$) and strength ($R_S$) factors. However, the response modification and strength factors for structural systems presented in design codes were based on professional judgment and experiences. A numerical study has been accomplished to evaluate force reduction, strength, and response modification factors for special steel moment resisting frames. A total of 72 prototype steel frames were designed based on the recommendations given in the AISC Seismic Provisions and UBC Codes. Number of stories, soil profiles, seismic zone factors, framing systems, and failure mechanisms were considered as the design parameters that influence the response. The effects of the design parameters on force reduction ($R_{\mu}$), strength ($R_S$), and response modification (R) factors were studied. Based on the analysis results, these factors for special steel moment resisting frames are evaluated.

[ $\b{S}afety\;\b{A}nd\;\b{E}fficacy$ ] of $\b{K}orean$ red ginseng Intervention (SAEKI) Trial: Rationale, Design, and Expected Findings

  • Sievenpiper John L;Buono Marco Di;Stavro P. Mark;Jenkins Alexandra L;Nam Ki Yeul;Choi Melody;Naeem Asima;Leiter Lawrence A;Sung Mi-Kyung;Vuksan Vladimir
    • Proceedings of the Ginseng society Conference
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    • pp.424-455
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    • 2002
  • Diabetes mellitus is reaching epidemic proportions worldwide. The insufficiency of medication to cope with this burden has coincided with a dramatic rise in the prevalence of use of complementary and alternative therapies, especially herbal treatments. This surge in demand presents a challenge to prove the safety and efficacy of these treatments in diabetes. Korean red ginseng (steam treated Panax ginseng C.A. Meyer) is a strong candidate to succeed. It has been shown to possess a multitude of hypoglycemic effects and improve metabolic disturbances related to diabetes in in vitro and animal models. Data in humans is also emerging to support these benefits. Whether these results can be replicated in a rigorous clinical testing program is unclear. We therefore investigated the antidiabetic effects of Korean red ginseng in a series of 2 acute and 1 longterm randomized, double-blinded, placebo-controlled clinical trials. This paper provides the rationale for this program of study, expanding on the problem of diabetes, its management, and the possible role for Korean red ginseng. It then describes the design and expected findings.

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Response modification factor of mixed structures

  • Fanaie, Nader;Shamlou, Shahab O.
    • Steel and Composite Structures
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    • v.19 no.6
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    • pp.1449-1466
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    • 2015
  • Mixed structures consist of two parts: a lower part and an upper part. The lower part is usually made of concrete while the upper part is made of steel. Analyzing these structures is complicated and code-based design of them has many associated problems. In this research, the seismic behavior of mixed structures which have reinforced concrete frames and shear walls in their lower storeys and steel frames with bracing in their upper storeys were studied. For this purpose, seventeen structures in three groups of 5, 9 and 15 storey structures with different numbers of concrete and steel storeys were designed. Static pushover analysis, linear dynamic analysis and incremental dynamic analysis (IDA) using 15 earthquake records were performed by OpenSees software. Seismic parameters such as period, response modification factor and ductility factor were then obtained for the mixed (hybrid) structures using more than 4600 nonlinear dynamic analysis and used in the regression analysis for achieving proper formula. Finally, some formulas, effective in designing such structures, are presented for the mentioned parameters. According to the results obtained from this research, the response modification factor values of mixed structures are lower compared to those of steel or concrete ones with the same heights. This fact might be due to the irregularities of stiffness, mass, etc., at different heights of the structure. It should be mentioned that for the first time, the performance and seismic response of such structures were studied against real earthquake accelerations using nonlinear dynamic analysis, andresponse modification factor was obtained by IDA.

Response modification factor of suspended zipper braced frames

  • Abdollahzadeh, Gholamreza;Abbasi, Mehdi
    • Steel and Composite Structures
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    • v.18 no.1
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    • pp.165-185
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    • 2015
  • The suspended zipper bracing system is suggested to reduce the flaws of ordinary zipper braced and concentric inverted V braced frames. In the design procedure of suspended zipper bracing systems, columns and top story truss elements are strengthened. This bracing system show different performances and characteristics compared with inverted V braced and ordinary zipper frames. As a result, a different response modification factor for suspend zipper frames is needed. In this research paper, the response modification factor of suspended zipper frames was obtained using the incremental dynamic analysis. Suspended zipper braced frames with different stories and bay lengths were selected to be representations of the design space. To analyze the frames, a number of models were constructed and calibrated using experimental data. These archetype models were subjected to 44 earthquake records of the FEMA-P695 project data set. The incremental dynamic analysis and elastic dynamic analysis were carried out to determine the yield base shear value and elastic base shear value of archetype models using the OpenSEES software. The seismic response modification factor for each frame was calculated separately and the values of 9.5 and 13.6 were recommended for ultimate limit state and allowable stress design methods, respectively.

Lateral stiffness of reinforced concrete flat plates with steps under seismic loads

  • Kim, Sanghee;Kang, Thomas H.K.;Kim, Jae-Yo;Park, Hong-Gun
    • Earthquakes and Structures
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    • v.7 no.5
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    • pp.891-906
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    • 2014
  • The purpose of this study is to propose a modification factor to reflect the lateral stiffness modification when a step is located in flat plates. Reinforced concrete slabs with steps have different structural characteristics that are demonstrated by a series of structural experiment and nonlinear analyses. The corner at the step is weak and flexible, and the associated rotational stiffness degradation at the corner of the step is identified through analyses of 6 types of models using a nonlinear finite element program. Then a systematic analysis of stiffness changes is performed using a linear finite element procedure along with rotational springs. The lateral stiffness of reinforced concrete flat plates with steps is mainly affected by the step length, location, thickness and height. Therefore, a single modification factor for each of these variables is obtained, while other variables are constrained. When multiple variables are considered, each single modification factor is multiplied by the other. Such a method is verified by a comparative analysis. Finally, a complex modification factor can be applied to the existing effective slab width.

Determination of Damping Modification Factor in RC Structures Due to Energy Absorption Efficiency (에너지 흡수효율에 의한 철근콘크리트 구조물의 감쇠비 수정계수 결정)

  • 김장훈;좌동훈
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.161-166
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    • 2002
  • The modification factor( k-factor) of equivalent damping ratio utilized in the current state-of-the-practice to account for the imperfection of reinforced concrete structures in hysteresis loop is investigated. From this, it is found that the current modification factor does not include the effect of cyclic loading, one of the important characteristic properties of earthquake loading. This could be taken into account by considering the energy absorption efficiency based on the cummulative plastic deformation. From the study, it is suggested that the current approach for the modification factor for the equivalent damping ratio should be reformed.

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