• Applied Chemistry for Engineering
• /
• v.25 no.2
• /
• pp.181-187
• /
• 2014

In order to use the spherical atomizing reduction steel slag (ladle furnace slag, LFS) instead of the fine aggregate of polymer concrete composites, various specimens were prepared with various replacement ratios of atomizing reduction steel slag and the addition ratios of polymer binder. Physical properties of these specimens were investigated through the absorption test, the compressive strength test, the flexural strength test, the hot water resistance test, the pore analysis and the micro-structure using scanning electron microscope. Results showed that the compressive strength and flexural strength of specimens with 7.5% of polymer binders increased with the increase of replacement ratios of atomizing reduction steel slag, but those of the specimens with 8.0% or more of polymer binders showed a maximum strength at a certain replacement ratio due to the material segregation causing the increase of fluidity. By hot water resistance tests, the compressive strength, flexural strength, average pore diameter, and bulk density decreased but the total pore volume and pore diameter increased. It was concluded that the amount of polymer binders could be reduced by maximum 23.8%, because the workability of the polymer concrete was remarkably improved by using the atomizing reduction steel slag instead of fine aggregate. However, since the use of atomizing reduction steel slag decreased the resistance of the polymer concrete to hot water, further studies are required.

• Steel and Composite Structures
• /
• v.50 no.5
• /
• pp.595-608
• /
• 2024

In this study, aluminum lathe waste was used by replacing aggregates in certain proportions in order to obtain expansive concrete using recycled materials. For this reason, five different aluminum wastes of 1%, 2%, 3%, 4% and 5% were selected and also reference without aluminum waste was produced. Based on the mechanical tests conducted, which included slump, compression, splitting tensile, and flexural tests, it was evident that the workability of the material declined dramatically once the volume ratio of aluminum exceeded 2%. As determined by the compressive strength test (CST), the CS of concrete (1% aluminum lathe wastes replaced with aggregate) was 11% reducer than that of reference concrete. It was noted that the reference concrete's CS values, which did not include aluminum waste, were greater than those of the concrete that contained 5% aluminum. When comparing for splitting tensile strength (STS), it was observed that the results of STS generally follow the parallel inclination as the CS. The reduction in these strengths when 1% aluminum is utilized is less than 10%. These ratios modified 18% when flexural strength (FS) is considered. Therefore, 1% of aluminum waste is recommended to obtain expansive concrete with recycled materials considering minimum loss of strength. Moreover, Scanning Electron Microscope (SEM) analysis was performed and the results also confirm that there was expansion in the aluminum added concrete. The presence of pores throughout the concrete leads to the formation of gaps, resulting in its expansion. Additionally, for practical applications, basic equations were developed to forecast the CS, STS, and FS of the concrete with aluminum lathe waste using the data already available in the literature and the findings of the current study. In conclusion, this study establishes that aluminum lathe wastes are suitable, readily available in significant quantities, locally sourced eco-materials, cost-effective, and might be selected for construction using concrete, striking a balance among financially and ecological considerations.

• Journal of the Korea Concrete Institute
• /
• v.15 no.2
• /
• pp.234-245
• /
• 2003

Most of the concrete bridge structures are exposed to damage due to the excessive traffic loading and the aging of the structure. The damage of concrete causes the further deterioration of the function in the concrete structure due to corrosion of the reinforced bars and decohesion between the concrete and the reinforced bar. The quick rehabilitation of the damaged concrete structures has become of great importance in the concrete structural system in order to avoid the further deterioration of the structures. Recently fiber sheets are used for strengthening the damaged concrete structures due to its many advantages such as its durability, non-corrosive nature, low weight, ease of application, cost saving, control of crack propagation, strength to thickness ratio, high tensile strength, serviceability and aesthetic. However, the lack of analytical procedures for assessing the nominal moment capacity by the fiber sheet reinforcement leads to difficulties in the effective process of decisions of the factors in the strengthening procedure. In this work, flexural strengthening effects by fiber sheets bonded on bottom face of the member are studied for the reinforced concrete T beam. In addition, auxiliary flexural strengthening effects by U-type fiber sheets bonded on bottom and side faces of the member to prevent delamination of the bottom fiber sheet are theoretically investigated. The analytical solutions are compared with experimental results of several references to verify the proposed approach. It is shown that the good agreements between the predicted results and experimental data are obtained.

• Journal of Korean Society of Steel Construction
• /
• v.29 no.3
• /
• pp.237-247
• /
• 2017

This paper investigates structural characteristics of internal vertical diaphragm and its influence on the connection strength between concrete filled tubular(CFT) column and beam. CFT columns are hybrids that combine two materials in one member. They have the benefits of steel for high tensile strength and ductility and of concrete for high compressive strength and stiffness. Analytical method of the flexural strength of vertical diaphragm to account moment transfer between panel zones is presented using yield line theory. Connection design is verified by a set of monotonic tests and numerical analysis with different diaphragm thicknesses. Plastic zones of CFT flange was found and matched closely to FEM results. Both analytical and experimental results showed good agreement that vertical diaphragm effectively alleviates the stress and transfer the force.

• International Journal of High-Rise Buildings
• /
• v.3 no.2
• /
• pp.107-120
• /
• 2014

A Reinforced concrete (RC) shear wall system with coupling beams has been known as one of the most promising structural systems for high-rise buildings. However, significantly large flexural and/or shear stress demands induced in the coupling beams require special reinforcement details to avoid their undesirable brittle failure. In order to solve this problem, one of promising candidates is frictional hysteretic energy dissipating devices (HEDDs) as an alternative to the coupling beams. The introduction of frictional HEDDs into a RC shear wall system increases energy dissipation capacity and maintains the frame action after their yielding. This paper investigates the strength demands (specifically yield strength levels) with a maximum allowable ductility of frictional HEDDs based on comparative non-linear time-history analyses of a prototype RC shear wall system with traditional RC coupling beams and frictional HEDDs. Analysis results show that the RC shear wall systems coupled by frictional HEDDs with more than 50% yield strength of the RC coupling beams present better seismic performance compared to the RC shear wall systems with traditional RC coupling beams. This is due to the increased seismic energy dissipation capacity of the frictional HEDD. Also, it is found from the analysis results that the maximum allowable ductility demand of a frictional HEDD should increase as its yield strength decreases.

• Journal of the Korean Ceramic Society
• /
• v.35 no.5
• /
• pp.421-428
• /
• 1998

The effect of silane coupling agents on the water stability of HAC/PVA based MDF cement composites which were modified with urethane and epoxy resin were studied as a function of the functional groups and addition amount of silane coupling agent. According to the composition of polymer matrix the silanes with different functional groups showed the different effectiveness. In case of the only PVA matrix the silane with vinyl functional group was more effective than other silanes. When the epoxy resin was added the silane of epoxy-methodxy group enhanced the flexural strength of dry and wet state more than other. In case of urethane-added MDF cement the silane of diamine group was effective and enhanced the water sta-bility fo MDF cement composite more and more as the addition amount of silane increased, Especially in case of warm-presed composite the effect of silane was enhanced By addition of 2wt% of silane with 야-amine group the flexural strength of urethane-added composites were enhanced by 20% more in dry state 40-70% in wet state in accord with the porosity analysis. The flexural strength of the poxy resin-added MDF cement composite was increased by addition of 1wt% and 2wt% silane of epoxy-methoxy group However the addition of 4wt% of silane decreased the flexural strength of dry and wet state by formation of closed pore in the polymer matrix.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.2A
• /
• pp.105-113
• /
• 2011

This study evaluated the effects of fibers on the mechanical properties and chemical solution resistance of porous concrete with fiber type (jute, pulp, PVA and nylon fiber) and fiber volume fraction (0.0%, 0.1%, 0.2%, 0.3%). The tests that were carried out to analysis the properties of porous concrete included compressive strength, void ratio, pH value, and chemical solution exposure with varying type and volume fraction of fiber were conducted. The type and volume fraction of fiber also affected the void ratio, compressive strength, flexural strength and chemical solution exposure. Increased volume fractions of fiber resulted in improved properties of the compressive strength, flexural strength and void ratio. However, the difference between the measured pH value and chemical resistance of porous concrete with fiber type and volume fraction was not significant.

• Journal of Korean Society of Steel Construction
• /
• v.24 no.5
• /
• pp.511-520
• /
• 2012

The double split Tee connection, a type of full strength-partially restrained connection, has adequate flexural strength according to the changes in the thickness of the T-stub flange and the gauge distance of the high-strength bolts. Moreover, the double split Tee connection is designed and constructed with seismic connections that have enough ductility capacity applicable to ordinary moment frame and special moment frame by grade of steel, size of beam and column and geometric connection shape. However, such a domestic research and a proposal of a suitable design formula about the double split Tee connection are insufficient. Thus, many experimental and analytical studies are in need for the domestic application of the double split Tee connection. Therefore, this study aimed to examine and suggest feasibility of a design formula of the double split Tee connection of FEMA.

• Structural Engineering and Mechanics
• /
• v.28 no.1
• /
• pp.39-52
• /
• 2008

Column shear failures observed during recent earthquakes and experimental data indicate that shear deformations are typically associated with the amount of transverse reinforcement, column aspect ratio, axial load, and a few other parameters. It was shown that in some columns shear displacements can be significantly large, especially after flexural yielding. In this paper, a piecewise linear model is developed to predict an envelope of the cyclic shear response including the shear displacement and corresponding strength predictions at the first shear cracking, peak strength, onset of lateral strength degradation, and loss of axial-load-carrying capacity. Part of the proposed model is developed using the analysis results from the Modified Compression Field Theory (MCFT). The results from the proposed model, which uses simplified equations, are compared with the column test data.

• Structural Engineering and Mechanics
• /
• v.8 no.6
• /
• pp.531-546
• /
• 1999

The paper presents an experimental and theoretical study on the influence of steel fibers and longitudinal tension and compression reinforcements on immediate and long-term deflections of high-strength concrete beams of 85 MPa (12,300 psi) compressive, strength. Test results of eighteen beams subjected to sustained load for 180 days show that the deflection behavior depends on the longitudinal tension and compression reinforcement ratios and fiber content; excessive amount of compression reinforcement and fibers may have an unfavorable effect on the long-term deflections. The beams having the ACI Code's minimum longitudinal tension reinforcement showed much higher time-dependent deflection to immediate deflection ratio, when compared with that of the beams having about 50 percent of the balanced tension reinforcement. The results of theoretical analysis of tested beams and those of a parametric study show that the influence of steel fibers in increasing the moment of inertia of cracked transformed sections is most pronounced in beams having small amount of longitudinal tension reinforcement.