• Title/Summary/Keyword: AEMM

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Aging Coefficient Formula of Reinforced Concrete Members under Axial Compression (축하중을 받는 철근콘크리트 부재의 재령계수식 제안)

  • Yoo, Jae-Wook;Yu, Eun-Jong
    • Journal of Korean Association for Spatial Structures
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    • v.13 no.4
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    • pp.67-74
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    • 2013
  • The Age-adjusted effective Modulus Method(AEMM) is one of the methods adopted for the construction stage analysis of concrete structures. The AEMM uses the aging factor to consider the effects of the varying concrete stress. In the aspects of computation time and the accuracy of the results, the AEMM is considered as one of most appropriate methods for construction stage analysis of tall building structures. Previous researches proposed appropriate values of the aging factor in the forms of graphs or using very simple equations. In this paper, an equation for estimating the aging factor as a function of rebar ratio in the section, compressive strength of concrete, notional member dimension, and age of concrete at the load application. The validity of aging factor proposed in this paper were examined by the comparison with the results of step-by step method.

Long-term Behavior of Steel-Concrete Composite Girders due to Concrete Shrinkage (콘크리트 건조수축에 의한 합성거더의 장기거동)

  • Bae, Doo Byong;Youn, Seok Goo;Ham, Sang Hee
    • Journal of Korean Society of Steel Construction
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    • v.16 no.6 s.73
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    • pp.807-818
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    • 2004
  • Experimental tests and theoretical methods of the analysis of the concrete shrinkage behaviors of steel-concrete composite girders are described herein. Steel-concrete composite test specimens were fabricated in the laboratory, and long-term behaviors such as deflections, curvatures, and strains were measured for one year. Test results were compared to the analytical results obtained by using the age-adjusted effective modulus method (AEMM). In addition, composite girders have been analyzed to investigate the effects of several parameters on the concrete shrinkage behaviors. From the long-term test results, it could be used to validate AEMM for the evaluation of the shrinkage behavior of composite girders. Because the shrinkage of the reinforced concrete slab in composite girders may lead to large tensile stresses in the concrete section, the transverse cracking of the slab could occur both in the positive and negative regions. Therefore, if the cracking of concrete would be ignored,it might lead to an overestimation of the stresses of the steel section of composite girders. Based on this research, it is proposed that the effect of transverse concrete cracking on the shrinkage behavior of steel-concrete composite bridges be considered.

Column Shortening Analysis of Composite Columns by Age-adjusted Effective Modulus Method (재령보정유효탄성계수법에 의한 합성기둥 축소량 해석)

  • Kim Han-Soo;Kim Jae-Keun;Kim Do-Kyoon
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2006.04a
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    • pp.490-495
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    • 2006
  • The analysis method proposed by PCA is widely used in calculating the column shortening of reinforced and composite columns of a tall building. However, residual creep factor which relates creep strain of reinforced concrete to creep strain of plain concrete is based on Rate of Creep Method (RCM) which has theoretical defects and is considered obsolete. In this paper, a new equation for the residual creep factor based on Age-adjusted Effective Modulus Method (AEMM) which is considered exact and better than RCM is proposed. The residual creep factor by RCM is found to be higher than one by AEMM, which means current PCA method overestimates the shortening of a reinforced concrete column. By using the residual creep factor by AEMM, more exact column shortening of a tall building can be obtainable with a simple modification to PCA method.

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Experimental study on long-term behavior of prestressed steel I-beam-concrete composite beams

  • Sung, Deokyong;Hong, Seongwon
    • Steel and Composite Structures
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    • v.42 no.5
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    • pp.671-683
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    • 2022
  • To investigate and predict the long-term time-dependent behavior, such as creep, shrinkage, and relaxation of PS strands, and prestress loss in prestressed steel-concrete composite beams, named Precom, full-scale tests were conducted and the collected data were compared with those obtained from the two proposed analytical models. The combined effective modulus method (EMM)-empirical model proposed with a flowchart considered the creep effect to determine the prestress loss. Conversely, the age-adjusted effective modulus method (AEMM) with CEB-FIP equation was developed to account for the concrete aging. The results indicated that the AEMM with CEB-FIP model predicts the long-term behavior of Precom effectively.

Comparative Study of Long-Term Deflection Estimated by KCI Code Multiplier and Age-adjusted Effective Modulus Method (설계기준과 AEMM에 의해 추정된 장기처짐량의 비교)

  • Choi, Jae-Keun;Kim, Su-Man
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.11a
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    • pp.361-364
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    • 2006
  • It is specified in KCI code that long-tenn deflection shall be determined by multiplying the immediate deflection by KCI code multiplier, unless it is obtained by a more comprehensive analysis. Therefore, in this study, the estimation method of long-term deflection by KCI code multiplier is known resonable by comparing analysis results using KCI code multiplier and AEMM.

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Structural Analysis of a Tall Building Considering Inelastic Differential Column Shortening (비탄성 부등기둥축소를 고려한 초고층 구조 해석)

  • Kim, Han-Soo;Jeomg, Se-Hun;Shin, Seung-Hak
    • Proceedings of the Korea Concrete Institute Conference
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    • 2009.05a
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    • pp.175-176
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    • 2009
  • An improved column shortening analysis method which can be used in designing the horizontal members has been proposed. If you use this analysis method which is used effective modulus method by EMM or AEMM, you will get more exactly moments on the horizontal members.

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Development of An Areal Elderly Migration Model for Demand Estimation of Rural Retirement Community (농촌지역 실버타운의 수요예측을 위한 노인인구이동 모형의 개발)

  • Jung, Nam-Su;Lee , Jeong-Jae;Kim , Han-Joong;Yoon , Seong-Su
    • Journal of The Korean Society of Agricultural Engineers
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    • v.46 no.2
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    • pp.29-37
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    • 2004
  • An areal elderly migration model (AEMM) was developed to assess the demand of rural development projects targeted towards elderly people. The AEMM was developed with adaptation of the gravity model to represent spatial interaction regarding amenities. Areal characteristics were classified for estimating the amenities from the perspective of net migration. From 1990 to 2000, data were acquired from USCB, PASDA, PAHEALTH, PADCNR, PFBC, and NCDC in 67 Pennsylvania counties for analysis and application. The results revealed that elderly migration can be explained not only by areal characteristics but also by spatial interaction considering the population, distances, and amenities of surrounding areas.

Effects of various receptor antagonists on the peripheral antinociceptive activity of aqueous extracts of Dicranopteris linearis, Melastoma malabathricum and Bauhinia purpurea leaves in mice

  • Zakaria, Zainul Amiruddin;Sodri, Nurul Husna;Hassan, Halmy;Anuar, Khairiyah;Abdullah, Fatimah Corazon
    • CELLMED
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    • v.2 no.4
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    • pp.38.1-38.6
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    • 2012
  • The present study aimed to determine the possible mechanisms of the peripheral antinociception of the aqueous extracts of Dicranopteris linearis (AEDL), Melastoma malabathricum (AEMM) and Bauhinia purpurea (AEBP) leaves in mice. Briefly, the antinociceptive profile of each extract (300, 500, and 1000 mg/kg; subcutaneous (s.c.)), was established using the abdominal constriction test. A single dose (500 mg/kg) of each extract (s.c.) was pre-challenged for 10 min with various pain receptors' antagonists or pain mediators' blockers and 30 min later subjected to the antinociceptive assay to determine the possible mechanism(s) involved. Based on the results obtained, all extracts exerted significant (p < 0.05) antinociceptive activity with dose-dependent activity observed only with the AEMM. Furthermore, the antinociception of AEDL was attenuated by naloxone, atropine, yohimbine and theophylline; AEMM was reversed by yohimbine, theophylline, thioperamide, pindolol, reserpine, and 4-chloro-DL-phenylalanine methyl ester hydrochloride; and of AEBP was inhibited by naloxone, haloperidol, yohimbine and reserpine. In conclusion, the antinociceptive activity of those extracts possibly involved the activation of several pain receptors (i.e. opioids, muscarinic, ${\alpha}_2$-adrenergic and adenosine receptors, adenosine, H3-histaminergic and $5HT_{1A}$, dopaminergic receptors).

Estimation of Stress Variations on Time Effects in Prestressed Concrete Composite Girder Bridges (PCS 합성거더교의 시간에 따른 응력 변화 추정)

  • Yoon, Ji-Hoon;Kim, Su-Man
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.11a
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    • pp.319-322
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    • 2005
  • When a concrete structure is subjected to load, its response is both immediate and time dependent. Under sustained load, the deformation of a structure gradually increases with time and eventually may be many time greater than its instantanneous value. The gradual development of strain with time is caused by creep and shrinkage. On this study, to estimate of stress variations on time effects in partially prestressed concrete composite girder bridges, computer program applied Age-adjusted Effective Modulus Method(AEMM) in used.

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The Estimation of Stress Variationdue to Creep and Shrinkage on Composite Girder Section (크리프 및 건조수축에 의한 합성거더 단면의 응력변화 추정)

  • Kim, Byung-Kyu;Kim, Su-Man
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.11a
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    • pp.357-360
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    • 2006
  • Under sustained load, the stress variation occurs due to creep and shrinkage of concrete on the sections of steel-concrete composite girders. In standard specification for highway bridge, the method of stress estimation considering time effects is based on the concept of Yassumi method. In this study, comparing the analysis results using the AEMM and Yassumii method long-term behaviors, the rationality of specified requirements is checked.

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