• 제목/요약/키워드: long-term deformation behavior

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Investigation of the Effect of Organoclay Additives on Mechanical Properties of PF resin and MPB-OSL using Creep Behavior Analysis and IB Test

  • Kim, Yong-Sik;Kadla, John F.
    • Journal of the Korean Wood Science and Technology
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    • v.39 no.5
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    • pp.381-389
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    • 2011
  • The effect of organoclays on the mechanical properties of cured phenol formaldehyde resin and oriented strand lumber made from Mountain Pine Beetle killed pine strands was analyzed. Three organoclays were used: a natural montmorillonite, hydrophobic organically modified 10 A, and hydrophilic organically modified 30 B. The oriented strand lumber samples were less creep deformation as well as improved internal bonding strength by adding organoclays in the order of 10 A 2% > MMT 2% > 30 B 2% > control. Furthermore, time-temperature superposition (TTS) analysis was proved to be able to predict the long-term creep behavior of MPB-OSL samples.

Compressibility of broken rock-fine grain soil mixture

  • Xu, Ming;Song, Erxiang;Cao, Guangxu
    • Geomechanics and Engineering
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    • v.1 no.2
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    • pp.169-178
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    • 2009
  • Due to the enormous amount of fills required, broken rock-fine grain soil mixtures have been increasingly used in the construction of high-fill foundations for airports, railways and highways in the mountain areas of western China. However, the compressibility behavior of those broken rock-fine grain soil mixtures remains unknown, which impose great uncertainties for the performance of those high-fill foundations. In this research, the mixture of broken limestone and a fine grain soil, Douposi soil, is studied. Large oedometer tests have been performed on specimens with different soil content. This research reveals the significant influence of fine grains on the compressibility of the mixture, including immediate settlement, creep, as well as wetting deformation.

Behavior of Geosynthetic Reinforced Modular Block Walls under Sustained Loading using Reduced-Scale Model Test (축소모형실험에 의한 지속하중하에서의 보강토 옹벽의 거동특성 연구)

  • Yoo, Chung-Sik;Kim, Sun-Bin;Byun, Joseph;Kim, Young-Hoon;Han, Dae-Hui
    • Journal of the Korean Geosynthetics Society
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    • v.5 no.1
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    • pp.1-7
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    • 2006
  • Despite a number of advantages of reinforced earth walls over conventional concrete retaining walls, there exit concerns over long-term residual deformation when used as part of permanent structures. In view of these concerns, time-dependant deformation characteristics of geosynthetic reinforced modular block walls under sustained loads were investigated using reduced-scale model tests. The results indicated that a sustained load can yield appreciable magnitude of residual deformation, and that the magnitude of residual deformation depends on the loading characteristic as well as reinforcement stiffness.

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Development of a Tensile Force Measurement Device of Long Duration (인장력 상시 측정장치 개발에 관한 연구)

  • Shin, Kyung Jae;Hwang, Yun Ha
    • Journal of Korean Society of Steel Construction
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    • v.15 no.4 s.65
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    • pp.435-445
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    • 2003
  • Tension member is one of the most important elements in tension structure. An economical and reliable measurement method of a member's tensile force has yet to be developed, however. Several conventional measurement methods have some disadvantages when used for long-term, on-site measurement. A new tension-force measurement device was proposed to resolve measuring problems. Its principle was to use the bending part of the device as an elastic spring. The lateral deformation of the bending part due to tensile force can be measured to monitor the tensile force. This device was inserted in the tension member like a turn-buckle. Lateral deformation may be measured in the field at any time for the purpose of maintaining structures. Finite element analysis was used to design the shape and parametric study. Six specimens were tested within the elastic range. The test result showed that the elastic behavior or the bending part was consistent with the analysis' results.

A Study on the Behavior during Constructing of Rigid Reinforced Roadbed to apply for the Slab Track (콘크리트궤도용 강성보강노반의 시공 중 거동에 관한 연구)

  • Kim, Ki-Hwan;Kim, Dae-Sang;Park, Seong-Yong;Park, Jong-Sik;Yoo, Chung-Sik
    • Proceedings of the KSR Conference
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    • 2011.05a
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    • pp.1774-1785
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    • 2011
  • In this paper, Rigid Reinforced Roadbed(RRR) which is expected to have highly applicability to railroad roadbed, was introduced and field tests results were analyzed. Full scale model with 5m height concerning a single track railroad roadbed was constructed. The model had four different sections, which was to assess the effect of geogrid length, spacing, and connection method on deformation characteristics of RRR. Laser displacement meter, earth pressure cell, piezometer, and strain gauge were installed in order to analyze the behavior of reinforced embankment during construction. Horizontal displacements caused by compaction at each section were 20~30% below the displacement limit that of general reinforced retaining wall, which showed that RRR was very stable structure. Maximum tensile strength of reinforcement was withing 10% of the long-term design strength.

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Long-Term Behavior of CFRP Strips under Sustained Loads (지속하중을 받는 탄소섬유판의 장기 거동)

  • You, Young-Chan;Choi, Ki-Sun;Kim, Keung-Hwan
    • Journal of the Korea Concrete Institute
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    • v.21 no.2
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    • pp.139-146
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    • 2009
  • Experimental study was performed to evaluate the long-term behavior of CFRP (carbon fiber reinforced polymer) strips under sustained loads including prestressing force in strengthening RC members with post-tensioned CFRP strips. Two types of CFRP strip such as unidirectional CFRP strip and hybrid CFRP strip which is composed of carbon fiber and steel plate were considered. Also two types of loading scheme were included in this study. Direct sustained loading test had been carried out to estimate the creep deformation and relaxation of CFRP strips including slip deformation at both mechanical anchorages for over 700 days. Also, flexural sustained loading test had been conducted to estimate the initial prestress losses on clamping the CFRP strips at jacking anchorages for over 90 days. From the sustained loading tests, it was observed that stress losses of unidirectional CFRP strips due to the creep deformation and relaxation of material itself and slip deformation at mechanical anchorage were ignorable. On the other hand, significant stress losses caused by the yielding of steel embedded in CFRP strips were found in case of hybrid CFRP strips due to the initial jacking force over steel yielding stress. Also, initial prestress losses during setting of CFRP strips on mechanical anchorage were about 10% of intial jacking force, which must be considered in the design.

Long-term Behavior of Precast Circular Composite Piers with Bonded Tendons (강연선으로 긴장한 강재매입형 조립식 합성교각의 장기거동)

  • Yoon, Jae-Young;Shim, Chang-Su;Chung, Young-Soo;Lim, Hyun-Sik
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.205-208
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    • 2008
  • Steel-embedded composite piers can enhance the resistance of core concrete by confinement of the steel elements and also can strengthen the stability of the embedded steel elements by concrete parts, so that the resistance of the composite members and seismic requirements can be provided without increasing section dimensions and self-weight. While modular composite piers with single segment do not need prestressing, precast segment composite piers with multiple segments need to have prestressing to prevent excessive cracking at the joints. Initial stresses and deformation by the introduced prestress are changed by long-term properties of concrete and need to be considered in the design. This paper deals with the prestress losses by the measurement of load cells, strains of reinforcements, concrete and embedded steel tubes.

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크리프와 건조수축을 고려한 철근콘크리트 기둥과 동바리의 축력 재분배 해석법

  • 김선영;이태규;김진근;이수곤
    • Journal of the Korea Concrete Institute
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    • v.13 no.6
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    • pp.629-636
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    • 2001
  • To apply the research results to the design and the construction of the high rise buildings, long-term behavior of reinforced concrete structure have been widely studied. However, shoring and reshoring at early ages have not been considered in the most of studies. The removal of forms and shores has been dealt with one construction sequence. i.e. the deformation occurred at the early age before the removal of shore has been neglected. In this paper, two-dimensional frame analysis program for long-term behavior of reinforced concrete was developed. In the developed program, construction sequence including the settlement and the removal of shores is considered to predict axial force variation due to forms ,shores, and time-dependent concrete stiffness. Analysis results show that the time-dependent axial force of shores is reduced, and the redistributed axial force of the interior column is greater than the value by elastic analysis and that of the exterior column is smaller. In order to demonstrate the validity of this program, the test frame was constructed in sequence of the placement of concrete, form removal, reshoring, shore removal, and the application of additional load. The proposed program predicts experimental results well.

Compressive Behavior of Reinforced Nylon Fiber Slag-CB (나일론 섬유 보강 Slag-CB의 압축거동 특성)

  • Younkyoung Lee;Taeyeon Kim;Jongkyu Lee;Youngsoo Joo;Bongjik Lee
    • Journal of the Korean GEO-environmental Society
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    • v.24 no.11
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    • pp.5-10
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    • 2023
  • Slag-CB is widely used in various fields that require groundwater control. It is a type of CB where a portion of the cement mixed with CB is replaced with GGBS. In general, Slag-CB has the advantage of long-term improvement in compressive strength, permeability, durability, and chemical resistance as the GGBS replacement ratio increases. However, there are problems such as decreased flexibility and resistance to deformation of the cut-off walls, as well as brittleness upon failure. To address these problems, some quality standards recommend designing Slag-CB with lower strength, which makes it challenging to apply high-strength Slag-CB with a high GGBS replacement ratio in the field.In this study, we aimed to improve the flexibility and resistance to deformation of Slag-CB to prevent brittle failure and improve the field applicability of Slag-CB. To achieve this, we evaluated the compressive behavior of nylon fiber-reinforced Slag-CB and proposed measures for enhancing the flexibility and resistance to deformation of Slag-CB.

Bending Creep Properties of Cross-Laminated Wood Panels Made with Tropical Hardwood and Domestic Temperate Wood

  • PARK, Han-Min;GONG, Do-Min;SHIN, Moon-Gi;BYEON, Hee-Seop
    • Journal of the Korean Wood Science and Technology
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    • v.48 no.5
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    • pp.608-617
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    • 2020
  • For efficient use and expansion of domestic small- and medium-diameter woods, cross-laminated wood panels composed of tropical hardwoods and domestic temperate woods were fabricated, and the bending creep behavior under long-term loading was investigated. The bending creep curve of the cross-laminated wood panels showed an exponential function graph with a sharp increase at the top right side. The wood panel composed of a teak top layer and larch core and bottom layers recorded the highest initial deformation, and that composed of a merbau top layer and tulip core and bottom layers showed the lowest initial deformation. Creep deformation of the cross-laminated wood panels showed the highest value in that composed of a teak top layer and larch core and bottom layers and showed the lowest value in that composed of a merbau top layer and tulip core and bottom layers. The obtained creep deformation is 3.1-4.3 times that of merbau, however, it is remarkably lower than that of tulip and larch. The highest relative creep was recorded by the wood panel composed of merbau top layer and larch core and bottom layers, whereas that composed of the teak top layer and tulip core and bottom layers showed the lowest relative creep.