• Journal of The Korean Society of Agricultural Engineers
• /
• v.55 no.4
• /
• pp.29-35
• /
• 2013

The objective of the current study is to evaluate the effects depending on the types of reinforcing fibers being influential in view of mechanical properties and impact resistance of hybrid fiber reinforced concrete (HFRC) for applications to precast concrete structure. Hybrid fibers applied therefor were three types such as PP/MSF (polypropylene fiber+macro synthetic fiber), PVA/MAF (polyvinyl alcohol fiber+MSF) and JUTE/MSF (natural jute fiber+MSF), where the volume fraction of PP, PVA and natural jute was applied with 0.2 %, respectively, while based on 0.05 % volume fraction of MSF. The HFRC was tested for slump, compressive strength, flexural strength and impact resistance. The test result demonstrated that mixture of such hybrid fibers improve compressive strength, flexural strength and impact resistance of concrete. Moreover, it was found that HFRCs to which hydrophilic fibers, i.e. PVA/MSF and JUTE/MSF, were mixed show more improved features that HFRC to which non-hydrophilic fiber, i.e. PP/MSF was mixed. Meanwhile, the finding that PVA/MSF HFRC exhibited better performance than JUTE/MSF HFRC was attributed from the former having higher aspect ratio than that of the latter.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.11a
• /
• pp.959-962
• /
• 2005

In the semiconductor and optical industry. a new transport system which can replace the conventional transport system is required. The Transport systems are driven by the magnetic field and conveyer belts. The magnetic field may damage semiconductor and the contact force may scratch the optical lens. The ultrasonic wave driven system can solve these problems. In this semiconductor and optical industry, the non-contact system is required for reducing the damages. The ultrasonic transportation is the solution of the problem. In this paper, the ultrasonic levitation system for levitation object are proposed. The 3D vibration profiles of the beam are measured by Laser Scanning Vibrometer for verifying the vibration characteristics of the system and the amplitudes of the beam and the levitation heights of object are measured fore evaluating the performance.

• Advances in concrete construction
• /
• v.3 no.1
• /
• pp.55-69
• /
• 2015

Tailing Material (TM) and Fly Ash (FA) are obtained as waste products from the mining and thermal industries. Studies were carried out to explore the possibility of utilizing TM as a part replacement to fine aggregate and FA as a part replacement to cement, in concrete mixes. The effect of replacing fine aggregate by TM and cement by FA on the standard sized specimen for compressive strength, split tensile strength, and flexural strengths are evaluated in this study. The concrete mix of M40 grade was adopted with water cement ratio equal to 0.40. Concrete mix with 35% TM and 65% natural sand (TM35/S65) has shown superior performance in strength as against (TM0/S100, TM30/S70, TM40/S60, TM50/S50, and TM60/S40). For this composition, studies were performed to propose the optimal replacement of Ordinary Portland Cement (OPC) by FA (Replacement levels studied were 20%, 30%, 40% and 50%). Replacement level of 20% OPC by FA, has shown about 0-5% more compressive strength as against the control mix, for both 28 day and 56 days of water curing. Interestingly results of split tensile and flexural strengths for 20% OPC replaced by FA, have shown strengths equal to that of no replacement (control mix).

• Advances in concrete construction
• /
• v.8 no.1
• /
• pp.47-54
• /
• 2019

Portland cement pervious concrete has been expected to have good water permeability, mechanical properties and abrasion resistance at the same time when Portland cement pervious concrete is applied to the actual vehicle pavement. In this study, the coarse aggregate and cement were replaced by the fine aggregate and the silica fume to improve actual road performance Portland cement pervious concrete. The Mechanical properties, the water permeability and the abrasion resistance of Portland cement pervious concrete were investigated. The results show that the compressive strength, the flexural strength and the abrasion resistance are increased when the fine aggregate and the silica fume are added to Portland cement pervious concrete separately. However, the porosity and the water permeability are decreased simultaneously. With assistance of silica fume and fine aggregate simultaneously, Portland cement pervious concrete could achieve a higher strength. The compressive strength, the flexural strength and the abrasion resistance of Portland cement pervious concrete mixed with 5% fine aggregates and 8% silica fume are increased by 93.1%, 65% and 65.2%, respectively. The porosity and the water permeability are decreased by 22.4% and 85% when Portland cement pervious concrete is mixed with 5% fine aggregate and 8% silica fume. Therefore, the replacement ratio of the fine aggregates and the silica fume should be considered comprehensively and determined on the premise of ensuring the water permeability coefficient.

• Journal of the Architectural Institute of Korea Structure & Construction
• /
• v.35 no.5
• /
• pp.153-160
• /
• 2019

The purpose of this study was to investigate the mechanical and durability characteristics of latex-modified concrete using ultra rapid hardening cement : four types of mechanical tests including compressive strength, modulus of elasticity, flexural strength and bond strength were performed; and seven types of durability tests including resistance of concrete to chloride ion penetration, freeze-thaw resistance, scaling resistance, coefficient of thermal expansion, cracking tendency, abrasion resistance and drying shrinkage were performed. Required material performance of each test was determined in accordance with the Korea specification for repair of concrete and pavement repairing materials. The test results satisfied the required material performances, and presented a good mechanical and durability characteristics. In particularly, the materials showed early development of compressive strength, flexural strength and bond strength at 3 and 4 hours after curing. SEM photos were also taken to investigate the micro structures of the materials after chloride ion penetration test.

• Coupled systems mechanics
• /
• v.10 no.2
• /
• pp.161-184
• /
• 2021

Strengthening of reinforced concrete beams with externally bonded fiber reinforced polymer plates/sheets technique has become widespread in the last two decades. Although a great deal of research has been conducted on simply supported RC beams, a few studies have been carried out on continuous beams strengthened with FRP composites. This paper presents a simple uniaxial nonlinear analytical model that is able to accurately estimate the load carrying capacity and the behaviour of damaged RC continuous beams flexural strengthened with externally bonded prestressed composite plates on both of the upper and lower fibers, taking into account the thermal load. The model is based on equilibrium and deformations compatibility requirements in and all parts of the strengthened beam, i.e., the damaged concrete beam, the FRP plate and the adhesive layer. The flexural analysis results and analytical predictions for the prestressed composite strengthened damaged RC continuous beams were compared and showed very good agreement in terms of the debonding load, yield load, and ultimate load. The use of composite materials increased the ultimate load capacity compared with the non strengthened beams. The major objective of the current model is to help engineers' model FRP strengthened RC continuous beams in a simple manner. Finally, this research is helpful for the understanding on mechanical behaviour of the interface and design of the FRP-damaged RC hybrid structures.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.34 no.6
• /
• pp.437-443
• /
• 2021

In this study, the use of a steel yielding damper is considered as an appropriate method to enhance the behavior of CBFs and a steel damper which is economical and straightforward to construct and replace after a severe earthquake is developed. The proposed damper was investigated experimentally and numerically. In addition, a parametric study was performed to evaluate the effect of the three types of damper mechanisms (shear, shear-flexural, and flexural) on the behavior of the proposed damper. The experimental results, as well as the numerical results, indicate that the shear damper exhibits better performance than the other dampers in terms of strength and stiffness.

• Earthquakes and Structures
• /
• v.20 no.4
• /
• pp.417-430
• /
• 2021

Due to functional requirements, SRC column-RC beam abnormal joints with characteristics of strong beam weak column, variable column section, unequal beam height and staggered height exist in the Steel reinforced concrete (SRC) frame-bent main building structure of thermal power plant (TPP). This paper presents the experimental results of these abnormal joints through cyclic loading tests on five specimens with scaling factor of 1/5. The staggered height and whether adding H-shaped steel in beam or not were changing parameters of specimens. The failure patterns, bearing capacity, energy dissipation and ductile performance were analyzed. In addition, the stress mechanism of the abnormal joint was discussed based on the diagonal strut model. The research results showed that the abnormal exterior joints occurred shear failure and column end hinge flexural failure; reducing beam height through adding H-shaped steel in the beam of abnormal exterior joint could improve the crack resistance and ductility; the abnormal interior joints with different staggered heights occurred column ends flexural failure; the joint with larger staggered height had the higher bearing capacity and stiffness, but lower ductility. The concrete compression strut mechanism is still applicable to the abnormal joints in TPP, but it is affected by the abnormal characteristics.

• Advances in concrete construction
• /
• v.13 no.1
• /
• pp.101-111
• /
• 2022

The rapid development of the construction industry in the world causes a rapid increase in the consumption of aggregate resources, which leads to the depletion of existing aggregate reserves. The use of recycled aggregate in the production of concrete and mortar may be a good solution to reduce the use of natural raw materials and to reduce demolition waste in the environment. In this study investigating the use of recycled aggregate in mortar production, mortar mixtures were produced by substituting 0%, 25%, 50% and 100% fine recycled aggregate (FRA) instead of natural aggregate. The effect of 20% and 40% fly ash (FA) substitutes on cement mortar performance was also investigated. Compressive and flexural strength, drying shrinkage, abrasion resistance, water absorption and capillary water absorption were investigated on the produced mortars. The increase in the use of FRA reduced the compressive and flexural strengths of mortars. While the capillarity coefficients, water absorption, rapid chloride permeability and drying shrinkage of the mortars increased with the increase in the use of FRA, the effect of the use of fly ash on the rate of increase remained lower. The increased use of FRA has improved abrasion resistance as well.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.64 no.4
• /
• pp.65-72
• /
• 2022

For sustainable development in the construction industry, blast furnace slag has been used as a substitute for cement in concrete. In contrast, ferronickel slag, which is the by-product generated during smelting to ferronickel used in the manufacturing of stainless steel and nickel alloys, has a limitation to use as a binder and an aggregate due to its expansive characteristics. Recently, stabilization technology of ferronickel slag has been improved and studies have been carried out to utilize ferronicke slag as fine aggregate in concrete. Therefore, in this study, basic mechanical properties of concrete used in ferronickel slag aggregate was evaluated. The compressive strength (24, 30, 40 MPa) and replacement rate of ferronickel slag aggregate (0, 10, 25, 50%) were considered as experimental variables. As a result of test, concrete replaced fine aggregate with 25% ferronickel slag aggregate showed superior performance in the compressive strength and flexural strength.