• Title/Summary/Keyword: overlaid concrete structures

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Damage of Overlaid Concrete Structures Subjected to Humidity Changes in the Atmosphere (습도 변화에 따른 콘크리트 덧씌우기 보수체의 손상분석)

  • 윤우현
    • Journal of the Korea Concrete Institute
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    • v.14 no.5
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    • pp.766-773
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    • 2002
  • The failure phenomenon of overlaid concrete structures, such as surface crack, and peel-off failure, shear bond failure in the end contact zone, was investigated due to humidity changes. To investigate this failure phenomenon, the surface tensile stress, and the shear stress, the vertical tensile stress in the contact zone were analysed using the non-linear stress-strain relationship of material such as strain-hardening- and strain-softening diagrams. Overlay thickness and overlay material were the main variables in the analyses. It is assumed that the initial surface humidity of overlaid concrete structures was 100% r.H. With a atmospheric humidity of 55% r.H. and two load cases for drying(LCI), curing and drying(LC2), the stress states of overlaid concrete structures were calculated. The result shows that only fictitious cracks occurred in the overlay surface of CM2O, ECM25, and no shear bond failure occurred in the contact zone without CM2O. The peel-off failure was proved to be the main cause of the damage in the overlaid concrete structures. Only for overlay thickness of 1cm occurred no peel-off failure in the case of drying after a long-term public use(LC1). In the case of curing and drying during overlay work(LC2) occurred the peel-off failure within 1.5days for all the overlaid concrete structures.

Damage of Overlaid Concrete Structures Subjected In Thermally Transient Condition by Rainfall (강우에 따른 콘크리트 덧씌우기 보수체의 손상에 관한 연구)

  • 윤우현
    • Journal of the Korea Concrete Institute
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    • v.13 no.5
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    • pp.491-498
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    • 2001
  • The failure phenomenon of overlaid concrete structures, such as surface crack and peel-off failure in the contact zone, was investigated due to temperature shock(rainfall). To investigate this failure phenomenon, the surface tensile stress, and the shear stress, the vertical tensile stress in the contact zone were analysed using the non-linear stress-strain relationship of material such as strain-hardening- and strain-softening diagrams. Rainfall intensity, overlay thickness and overlay material were the main variables in the analyses. It is assumed that the initial temperature of overlaid concrete structures was heated up to 55$\^{C}$ by the solar heat. With a rain temperature 10$\^{C}$ and the rainfall intensity of nR=1/a, tR=10min, 60min, the stress states of overlaid concrete structures were calculated. The result shows that only fictitious cracks occurred in the overlay surface and no shear bond failure occurred in the contact zone. The vortical tensile stress increasing with overlay thickness was proved to be the cause of peel-off failure in the contact zone. The formulae for relationship between the vertical tensile stress and overlay thickness, material properties were derived. Using this formulae, it is possible to select proper material and overlay thickness to prevent failure in the contact zone due to temperature shock caused by rainfall.

End Stress Analysis of Overlaid Concrete Structures Subjected to Thermally Transient Condition by Rainfall (강우에 따른 콘크리트 덧씌우기 보수체의 단부 온도응력 해석)

  • 윤우헌
    • Magazine of the Korea Concrete Institute
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    • v.10 no.4
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    • pp.145-151
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    • 1998
  • The vertical tensile stress, ${\sigma}_y$, in the contact zone between the overlay (mortar layer) and substratum (base concrete) can be the main cause of the failure phenomenon of overlaid concrete structures. The development of tensile stress, ${\sigma}_y$, due to external rainy condition was analytically investigated using finite element method. Rainfall intensity $(n_R\;=\;1/a,\;t_R\;=\;10min,\;60min)$, thickness of overlay (do=1,2,4,10 cm) and overlay material (CM,ECM,EM) were the main variables in the analyses. An equation was suggested with which the development of vertical tensile stress, ${\sigma}_y$, in the rainy condition could be determined. Using this equation, it is possible to select proper material properties and overlay thicknesses to prevent failure in the contact zone due to thermally transient condition caused by rainfall.

A Evaluation on Flexural Behavior for Hollow Core Slab of Fire Resistance section for Residence Building (주거용 내화단면 중공슬래브의 휨거동 평가)

  • Boo, Yoon-Seob;Bae, Kyu-Woong;Shin, Sang-Min
    • Journal of Korean Association for Spatial Structures
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    • v.23 no.2
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    • pp.61-68
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    • 2023
  • A two-hour fire-resistance PC hollow slab for residential use was developed to secure structural and fire-resistance performance and to be applied to the general building and apartment housing markets. Compared to the existing hollow slab, in order to secure the same or better structural performance and economic feasibility by reducing the quantity, it was attempted to secure the fire resistance performance by reducing the concrete filling rate in the cross section and adjusting the thickness of the upper and lower flanges by optimizing the hollow shape in the cross section of the slab. For structural performance evaluation, experiments were performed on PC hollow slabs by varying the member thickness and the presence or absence of overlaid concrete, and all of the experimental results showed that the design strength was sufficiently exhibited and that stability during construction was possible. The developed synthetic PC hollow slab has secured fire resistance and residential performance so that it can be applied to all buildings, and it is intended to be immediately applied to the field.

Experimental Study on the Flexural Behavior Effect of RC Beam Repaired and Strengthened by Latex Modified Concrete (라텍스개질콘크리트로 보수·보강된 RC 보의 휨 거동에 관한 실험적 연구)

  • Kim, Seong-Hwan;Yun, Kyong-Ku;Kim, Yong-Gon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.5A
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    • pp.503-510
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    • 2009
  • Latex modified concrete (LMC) is a successful polymer-portland cement concretes, which have been developed and used for many years, in overlaying bridge decks and resurfacing industrial floors. The excellent bond strength to substrate, easy application and high resistance to impact, abrasion, wear, aggressive chemicals and freeze-thaw deterioration have made this material used widely. The objective of this study was to determine experimentally the load-deflection response and ultimate strength of reinforced RC beams. The cracking patterns and the mode of failure were observed. Because of excellent bond strength and repairing effects, the RC beams repaired by LMC at compression or tension zone showed over 100% recovery from damaged structures. The RC beams overlaid by LMC showed significant improvement at load carrying capacity as overlay thickness increases. However, the beams repaired of tension zone without shear stirrups almost showed no strengthen effect, and indicated an interfacial failures. The interfacial behavior was estimated by numerical method adopting the concept of shear flow.