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  • Title/Summary/Keyword: shear strength of concrete

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Fiber Type Effects on the Flexural Behavior of Steel Fiber Reinforced Concrete Beams (강섬유의 형태에 따른 SFRC보의 휨거동에 관한 연구)

  • Jeon, Chan Ki
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.12 no.4
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    • pp.95-106
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    • 1992
  • This paper presents a comparative evaluation of five different types of steel fibers used as reinforcing material in concrete beams. Two types of plain and RC beams were prepared to compare the relative flexural behavior. The fibers used were dog bone (paddled), both ends hooked. コ-type straight. crimped and wavy type with aspect ratio of 43 to 75. Fiber volume fraction of 1 to 2% were used while shear span to depth ratio (aid) and steel ratio p were fixed. Fiber reinforcement effect index Ef and effective toughness index Te were adopted to evaluate fiber reinforcing effects. The effect of fiber reinforcement on flexural strength is higher in plain beams than in RC beams. Hooked and dog bone type fibers were found to be more effective than the other type ones in enhancing the flexural strength and post-peak energy absorption capacity of concrete beams.

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Structural Performance Evaluation of Reinforced Concrete Column Reinforced with Aramid Fibers and PET Fibers (아리미드섬유와 PET섬유시트로 보강한 철근콘크리트 기둥의 구조성능평가)

  • Dong-Hwan Kim;Min-Su Jo;Jin-Hyeung Choi;Woo-Rae Cho;Kil-Hee Kim
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.27 no.1
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    • pp.78-85
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    • 2023
  • This study evaluates the performance of reinforced concrete columns using hybrid fiber sheets for structural behavior. The purpose of this method is to improve the load-bearing capacity of the reinforced structure by impregnating a hybrid fiber sheet, which is woven by arranging aramid and glass fibers uniaxially and attached to an aged concrete structure requiring reinforcement with epoxy. In particular, not only the weight reduction of the material obtained by using a fiber lighter than the steel material, but also the low-strength, high-toughness fiber element among the fibers used delays the brittle fracture of the high-strength, low-toughness fiber element. The low-strength, high-toughness fiber element among the fibers used delays the brittle fracture of the high-strength, low-toughness fiber element, resulting in weight reduction compared to steel. The study conducted structural tests on four specimens, with the hybrid reinforcement method and failure mode as main variables. Specimen size and loading conditions were chosen to be comparable with previous studies. The structural performance of the specimen was evaluated using energy dissipation capacity and ductility. Analysis shows that excellent results can be obtained with the hybrid fiber sheet reinforcement.

Study on Safety Evaluation of the Half-Depth Precast Deck with RC Rib Pannel for the Flexural Behavior (리브 형상을 갖는 반단면 프리캐스트 판넬의 휨 안전성 평가 연구)

  • Hwang, Hoon Hee
    • Journal of the Korean Society of Safety
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    • v.34 no.4
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    • pp.76-84
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    • 2019
  • The precast pannels are used as formwork in Half-depth precast deck systems. Therefore, it has many advantages, including safe and convenient construction and reduced construction period compared to cast-in-place construction method. In half-depth precast deck systems, the bonding of precast pannels to cast-in place concrete is very important. To enhance the performance of half-depth precast deck system, it is necessary to improve the composite efficiency of the interface or increase the stiffness of the precast pannel to reduce deformation or stress on the interface. In this study, a flexural test of half-depth precast deck system was performed, in which the shear connecting reinforcement was applied to increase the bonding performance at the interface, and the rib shape precast panels were applied to improve stiffness. In addition, the safety and serviceability of these systems were evaluated. Test results show that all of specimens have the required flexural strength under the ultimate strength limit design. It was also evaluated to have sufficient safety for the serviceability of deflection and crack under the serviceability limit design.

Cyclic loading test for concrete-filled hollow PC column produced using various inner molds

  • Chae-Rim Im;Sanghee Kim;Keun-Hyeok Yang;Ju-Hyun Mun;Jong Hwan Oh;Jae-Il Sim
    • Steel and Composite Structures
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    • v.46 no.6
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    • pp.793-804
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    • 2023
  • In this study, cyclic loading tests were conducted to assess the seismic performance of cast-in-place (CIP) concrete-filled hollow core precast concrete columns (HPCC) constructed using steel ducts and rubber tubes. The outer shells of HPCC, with a hollow ratio of 47%, were fabricated using steel ducts and rubber tubes, respectively. Two combinations of shear studs & long threaded bars or cross-deformed bars & V-ties were employed to ensure the structural integrity of the old concrete (outer shell) and new CIP concrete. Up to a drift ratio of 3.8%, the hysteresis loop, yielding stiffness, dissipated energy, and equivalent damping ratio of the HPCC specimens were largely comparable to those of the solid columns. Besides the similarities in cyclic load-displacement responses, the strain history of the longitudinal bars and the transverse confinement of the three specimens also exhibited similar patterns. The measured maximum moment exceeded the predicted moment according to ACI 318 by more than 1.03 times. However, the load reduction of the HPCC specimen after reaching peak strength was marginally greater than that of the solid specimen. The energy dissipation and equivalent damping ratios of the HPCC specimens were 20% and 25% lower than those of the solid specimen, respectively. Taking into account the overall results, the structural behavior of HPCC specimens fabricated using steel ducts and rubber tubes is deemed comparable to that of solid columns. Furthermore, it was confirmed that the two combinations for securing structural integrity functioned as expected, and that rubber air-tubes can be effectively used to create well-shaped hollow sections.

An Experimental Study on the Mechanical Behavior of Concrete Using Non-Sintered Cement (비소성 시멘트 콘크리트의 역학적 거동에 대한 실험 연구)

  • Yoo, Sung-Won;Min, Gyeong-Oan
    • Journal of the Korea Institute of Building Construction
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    • v.12 no.1
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    • pp.115-121
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    • 2012
  • If cement could be manufactured with industrial byproducts such as granulated blast furnace slag, phosphogypsum, and waste lime rather than clinker, there would be many advantages, including the maximization of the use of these industrial byproducts for high value-added resources, the conservation of natural resources and energy by omitting the use of clinker, the minimization of environmental pollution problems caused by CO2 discharge, and the reduction of the production cost. For this reason, in this study, mechanical behavior tests of non-sintered cement concrete were performed, and elasticity modulus and stress-strain relationship of non-sintered cement concrete were proposed. Nine test members were manufactured and tested according to reinforcement ratio and concrete compressive strength. According to the test results, there was no difference between general cement concrete and non-sintered cement concrete in terms of flexure and shear behavior.

A study on Properties of Strength and Deformation of Composite beams varying Ratio of Tensile bar to Steel (철골철근비에 따른 혼합구조보의 내력 및 변형 특성에 관한 연구)

  • Lim, Byung Ho;Park, Jung Min;Kim, Wha Jung
    • Journal of Korean Society of Steel Construction
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    • v.14 no.1
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    • pp.87-94
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    • 2002
  • In the preceding study, a series of results was presented according to factors like as attaching method of main bar, shear span to depth ratio, reinforcing method for different types of region among various factors, which could determine the properties of composite beams. Based on these results, this study was planned to investigate the structural behaviors of according to attaching method of main bar for composite beams(end-reinforced concrete(RC), center-steel concrete (SC)) varying ratio of tensile bar to steel mainly. Consequently, there were little difference according to attaching method of main bar. And as the ratio of tensile bar to steel increase, the efficiency of strength was high, but ductile capacity of beams could deteriorate. Therefore, to maximize the structural properties of composite beams, it was considered that the ratio of tensile bar to steel should be limited.

Correction Coeffecient for Tensile Adhesive Strength of the Bridge Decks Waterproofing Systems with Different Temperature Conditions (온도조건에 따른 교면방수재의 인장접착강도 보정계수에 관한 실험적 연구)

  • Lee, Byung-Duck;Yun, Byung-Sung
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.05a
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    • pp.794-797
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    • 2004
  • In this study, tensile adhesive strength(TAS) test was carreid out for evaluated the effects of temperature conditions (-20, -10, 0, 5, 10, 20, 30, 40C) on the tensile adhesive characteristics about 4 type waterproofing membranes which were commercially used in bridge decks. And, failure appeariences of waterproofing systems in each temperature after TAS test were observed the sawing surfaces of waterproofing systems for whether or not damaged of waterproofing membranes. Also, correction coefficient of TAS with temperature were calculated using 4 type waterproofing membrane. It could be shown that the higher TAS and shear adhesive strength, the lower temperature, regardless of the type of waterproofing membrane. Temperature sensibility of TAS was especially remarkable in epoxy membrane. Failure type was occurred the ductile failure in 30Cand40C. From these results, it was shown that if ambient temperature above 30C maintains for a long time, waterproofing membrane will be deformed by softening. Otherwise, waterproofing membrane in temperature below 20C shown that occurred the brittle failure. From the results of visual observation of cutting surface for specimen, the thin waterproofing membranes shown indented by hot aggregate of the asphalt mixtures. Therefore, it could be known that the specification of waterproofing membrane thickness is necessary by waterproofing membrane type. As temperature change varied with pavement depth, the interface temperature was more important than ambient temperature in TAS test. Now, TAS test results were limited only in 10Cand20C temperature, but correction coefficient of TAS by ambient temperature could be used as a solution to deal with this problem.

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Structural performance by strengthening types of wood frames using H shaped steel joints (H형강 접합부를 갖는 목조 골조의 보강형식에 따른 구조성능)

  • Kim, Soon-Chul;Moon, Youn-Joon;Yang, Il-Seung;Park, Geun-Hong
    • KIEAE Journal
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    • v.8 no.3
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    • pp.77-83
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    • 2008
  • The effective mixture of structural laminated timber and other materials is expected to extend the potentials of building structures because of the potentials to realize high performance in structural safety. The classical joint types using drift pin and bolts are occurred local failures due to the small bearing area. In result, new joints using H shaped steel were suggested in this research. The objective of this study is to evaluate elasto-plastic behaviors by strengthening types of wood frames with new joints connecting structural laminated timber with H shaped steel. A total of five specimens of about one-second scale were tested. Specimens had columns with 1,050 height and 84mm×100mm section, and a beams with 1,950mm length and 130mm×100mm section. Also, the specimens were stiffened by brace, hwang-toh brick, and autoclaved lightweight concrete. The results of the test showed that the specimen stiffened with autoclaved lightweight concrete was characterized by fairly good strength and stiffness than those of the other specimens. Initial stiffness of H-2.0D-NS specimen with 2 times inserting length of beam height showed 1.33 times than that of H-1.5D-NS specimen. However, the strength of H-2.0D-NS specimen has not improved too much than H-1.5D-NS specimen.

Discrete Optimum Design of Reinforced Concrete Beams using Genetic Algorithm (유전알고리즘을 이용한 철근콘크리트보의 이산최적설계)

  • Hong, Ki-Nam;Han, Sang-Hoon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.9 no.1
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    • pp.259-269
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    • 2005
  • This paper describes the application of genetic algorithm for the discrete optimum design of reinforced concrete continuous beams. The objective is to minimize the total cost of reinforced concrete beams including the costs of concrete, form work, main reinforcement and stirrup. The flexural and shear strength, deflection, crack, spacing of reinforcement, concrete cover, upper-lower bounds on main reinforcement, beam width-depth ratio and anchorage for main reinforcement are considered as the constraints. The width and effective depth of beam and steel area are taken as design variables, and those are selected among the discrete design space which is composed with dimensions and steel area being used from in practice. Optimum result obtained from GA is compared with other literature to verify the validity of GA. To show the applicability and efficiency of GA, it is applied to three and five span reinforced concrete beams satisfying with the Korean standard specifications.

Basic Study on Fiber Composite Panel Production for Impact·Blast Resistant (방호·방폭 보강용 복합섬유 패널 제작을 위한 기초연구)

  • Kim, Woonhak;Kang, Seokwon;Yun, Seunggyu
    • Journal of the Society of Disaster Information
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    • v.11 no.2
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    • pp.235-243
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    • 2015
  • The methods to improve the protection and explosion-proof performance of concrete structures include the backside reinforcement or concrete material property improvement and the addition of structural members or supports to increase the resistance performance, but they are inefficient in terms of economics and structural characteristics. This study is about the basic study on the fiber composite panel cover, and the nano-composite material and adhesive as the filler, to maximize the specific performance of each layer and the protection and explosion-proof performance as the composite panel component by improving the tensile strength, light weight, adhesion and fire-proof performances. The fiber composite panel cover (aramid-polyester ratios of 6:4 and 6.5:3.5) had a 2,348 MPa maximum tensile strength and a 1.8% maximum elongation. The filler that contained the nano-composite material and adhesive had a 4 MPa maximum tensile shear adhesive strength. In addition, the nano-composite filler was 30% lighter than the normal portland cement