• Title, Summary, Keyword: modification factor

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Response Modification Factors for Seismic Performance Evaluation of Non-seismic School Buildings with Partial Masonry Infills (조적허리벽이 있는 비내진 학교시설의 내진성능평가를 위한 반응수정계수)

  • Kim, Beom Seok;Park, Ji-Hun
    • Journal of the Earthquake Engineering Society of Korea
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    • v.23 no.1
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    • pp.71-82
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    • 2019
  • Most school buildings consist of reinforced concrete (RC) moment frames with masonry infills. The longitudinal direction frames of those school buildings are relatively weak due to the short-column effects caused by the partial masonry infills and need to be evaluated carefully. In 'Manual for Seismic Performance Evaluation and Retrofit of School Facilities' published in 2018, response modification factor of 2.5 is applied to non-seismic RC moment frames with partial masonry infills, but sufficient verification of the factor has not been reported yet. Therefore, this study conducted seismic performance evaluation of planar RC moment frames with partial masonry infills in accordance with both linear analysis and nonlinear static analysis procedures presented in the manual. The evaluation results from the different procedures are compared in terms of assessed performance levels and number of members not meeting target performance objectives. Finally, appropriate response modification factors are proposed with respect to a shear-controlled column ratio.

Rational Evaluation of Seismic Response Modification Factor of Steel Moment Frame Based on Available Connection Rotation Capacity (접합부 회전능력에 기초한 철골모멘트골조의 반응수정계수 산정법)

  • Lee, Cheol-Ho;Kim, Geon-Woo;Song, Jin-Gyu
    • Journal of the Earthquake Engineering Society of Korea
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    • v.11 no.2
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    • pp.11-17
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    • 2007
  • In current seismic design practice, the response modification factor (R-factor) is used as a factor to reduce the elastic base shear demand to the design force level. As is well-known, the R-factor is a committee-consensus factor and, as such, highly qualitative and empirical. The relationship between the R-factor and the connection rotation capacity available in a particular structural system has remained a missing link. In this paper, a rational procedure to evaluate the R-factor is proposed. To this end, the relationship between the available connection rotation capacity and the R-factor is defined and quantified using nonlinear pushover analysis. An RRS steel frame designed according to IBC 2000 was used to illustrate and verify the proposed procedure. Nonlinear time history analysis results indicated that the R-factor definition proposed in this study is generally conservative from design perspective.

Case-based Software Project Network Generation by the Least Modification Principle (사례의 수정최소화 기법에 의한 소프트웨어 프로젝트 네트워크 생성시스템)

  • Lee, No-Bok;Lee, Jae-Kyu
    • Asia pacific journal of information systems
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    • v.13 no.1
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    • pp.103-118
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    • 2003
  • Software project planning is usually represented by a project activity network that is composed of stages of tasks to be done and precedence restrictions among them. The project network is very complex and its construction requires a vast amount of field knowledge and experience. So this study proposes a case-based reasoning approach that can generate the project network automatically based on the past cases and modification knowledge. For the case indexing, we have adopted 17 factors, each with a few alternative values. A special structure of this problem is that the modification effort can be identified by each factor independently. Thus it is manageable to identify 85 primitive modification actions(add and delete activities) and estimate its modification efforts in advance. A specific case requires a combination of primitive modifications. Based on the modification effort knowledge, we have adopted the Least Modification approach as a metric of similarity between a new project and past cases. Using the Least Modification approach and modification knowledge base, we can automatically generate the project network. To validate the performance of Least Modification approach, we have compared its performance with an ordinary minimal distance approach for 21 test cases. The experiment showed that the Least Modification approach could reduce the modification effort significantly.

Overstrength and Response Modification Factor in Low Seismicity Regions (약진지역에서의 초과강도 및 반응수정계수)

  • Lee, Dong-Guen;Cho, So-Hoon;Ko, Hyun;Kim, Tae-Jin
    • Journal of the Earthquake Engineering Society of Korea
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    • v.10 no.3
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    • pp.57-64
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    • 2006
  • Seismic design codes are mainly based on the research results for the inelastic response of structures in high seismicity regions. Since wind loads and gravity loads may govern the design in low seismicity regions in many cases, structures subjected to design seismic loads will have larger overstrength compared to those of high seismicity regions. Therefore, it is necessary to verify if the response modification factor based on high seismicity would be adequate for the design of structures in low seismicity regions. In this study, the adequacy of the response modification factor was verified based on the ductility and overstrength of building structures estimated from the result of nonlinear static analysis. Framed structures are designed for the seismic zones 1, 2A, 4 in UBC-97 representing the low, moderated and high seismicity regions and the overstrength factors and ductility demands of the example structures are investigated. When the same response modification factor was used in the design, inelastic response of structures in low seismicity regions turned out to be much smaller than that in high seismicity regions because of the larger overstrength of structures in low seismicity regions. Demands of plastic rotation in connections and ductility in members were much lower in the low seismicity regions compared to those of the high seismicity regions when the structures are designed with the same response modification factor.

A Study on the Response Modification Factor for a 5-Story Reinforced Concrete IMRF (5층 철근콘크리트 중간모멘트골조의 반응수정계수에 관한 연구)

  • Kang, Suk-Bong;Lim, Byeong-Jin
    • Journal of the Earthquake Engineering Society of Korea
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    • v.16 no.5
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    • pp.13-21
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    • 2012
  • In this study, the response modification factor for a RC IMRF is evaluated via pushover analysis, where 5-story structures were designed in accordance with KBC2009. The bending moment-curvature relationship for beams and columns was identified with a fiber model, and the bending moment-rotation relationship for beam-column joints was calculated using a simple and unified joint shear behavior model and the moment equilibrium relationship for the joint. The results of the pushover analysis showed that the strength of the structure was overestimated with negligence of the inelastic shear behavior of the beam-column joint, and that the average response modification factor for category C was 7.78 and the factor for category D was 3.64.

Seismic response modification factors for stiffness degrading soil-structure systems

  • Ganjavi, Behnoud;Bararnia, Majid;Hajirasouliha, Iman
    • Structural Engineering and Mechanics
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    • v.68 no.2
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    • pp.159-170
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    • 2018
  • This paper aims to develop response modification factors for stiffness degrading structures by incorporating soil-structure interaction effects. A comprehensive parametric study is conducted to investigate the effects of key SSI parameters, natural period of vibration, ductility demand and hysteretic behavior on the response modification factor of soil-structure systems. The nonlinear dynamic response of 6300 soil-structure systems are studied under two ensembles of accelograms including 20 recorded and 7 synthetic ground motions. It is concluded that neglecting the stiffness degradation of structures can results in up to 22% underestimation of inelastic strength demands in soil-structure systems, leading to an unexpected high level of ductility demand in the structures located on soft soil. Nonlinear regression analyses are then performed to derive a simplified expression for estimating ductility-dependent response modification factors for stiffness degrading soil-structure systems. The adequacy of the proposed expression is investigated through sensitivity analyses on nonlinear soil-structure systems under seven synthetic spectrum compatible earthquake ground motions. A good agreement is observed between the results of the predicted and the target ductility demands, demonstrating the adequacy of the expression proposed in this study to estimate the inelastic demands of SSI systems with stiffness degrading structures. It is observed that the maximum differences between the target and average target ductility demands was 15%, which is considered acceptable for practical design purposes.

Evaluation of the Response Modification Factor for RC Wall-type Structures (철근콘크리트 벽식 구조물의 반응수정계수 평가에 관한 연구)

  • 한상환;이리형;오영훈;천영수
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.433-438
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    • 1998
  • Design lateral strength calculated by current seismic design code is prescribed to be much lower than the force level required for a structure to respond elastically during design level earthquake ground motion. Present procedures for calculating seismic design forces are based on the use of elastic spectra reduced by a strength reduction factor known as "response modification factor, R". This factor accounts for the inherent ductility, overstrength, redundancy, and damping of a structural system. This study considers ductility and overstrength of the wall-type structure for investigating R factor. This means that R factor is determined from the product of "ductility-based R factor($R_$\mu$$) and overstrength factor($R_s$). $R_$\mu$$ factor is calibrated to attain the targer ductility ratio (system ductility capacity) and produced in the from of $R_$\mu$$ spectra considering the influence of target ductility, natural period, and hysteretic model. On the other hand, $R_s$ is more difficult to quantify, since it depends on both material and system-dependent uncertain parameters. In this study Rs factor was determined from the result of push-over analysis.-over analysis.

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Current Situation and Modification of Kitchen Space by Elderly-headed Household (노인단독가구의 부엌공간 실태와 개조에 관한 연구)

  • Kwon, Oh-Jung;Kim, Mi-Hee;Ha, Hae-Wha
    • Proceeding of Spring/Autumn Annual Conference of KHA
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    • pp.144-148
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    • 2006
  • Kitchen space is one of the most dangerous places for the elderly. Modification of kitchen space for improving safety and independence for older residents is very important factor for aging -in-place. The purpose of this study wes to identify the current situation and modification of kitchen space by elderly-headed household. The sample included 108 respondents over the age 65 who consisted of elderly-couple or single person household with homeownership in Seoul. The data were analyzed by descriptive statistics. Based on the findings of the study, the present incidence and recognition of future need in kitchen modification were identified. Changes in kitchen space made tended to be nonstructural or relatively inexpensive items. In conclusion, this study suggests several ideas for improving current physical problems of kitchen space to support daily living of older residents.

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A study on strength of internal gear (내접치차의 강도에 관한 연구)

  • 정태형
    • Journal of the korean Society of Automotive Engineers
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    • v.6 no.3
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    • pp.45-54
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    • 1984
  • Bending strength of an internal gear tooth is discussed as tooth form factor taking into account the actual stress magnitude. Stress analysis was carried out by the finite element method(FEM) for the calculation of tooth form factor of an internal gear. This paper also investigated the influences of number of teeth and addendum modification coefficient of the internal gear and the influences of number of teeth, addendum modification coefficient, pressure angle, radius of rounding of tooth tip, and bottom clearance coefficient of the pinion-shaped cutter on tooth form factor of internal gear. Generalizing the resultant data, a simple formula for the tooth form factor of an internal gear was derived for the calculation of tooth bending strength of an internal gear.

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Evaluation of Stress Intensity Factor after Penetration of Plate with Long Surface Crack (긴 표면균열재의 관통후 응력확대계수 평가)

  • Nam Kiwoo;Lee Jongrark
    • Journal of the Korean Institute of Gas
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    • v.4 no.1
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    • pp.33-39
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    • 2000
  • Stress intensity factor after penetration was discussed experimentally using long surface pre-cracked specimens of aluminum alloy 5083. The propagation behavior evaluation of long surface crack by equation proposed at penetration of short surface crack could be need modification to evaluate precisely because the error was high as aspect ratio is little. The modification of stress intensity factor with consideration of aspect ratio at penetration of long surface crack can be analyzed the behavior of crack penetration quantitatively.

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