• Journal of Korean Society of Steel Construction
• /
• v.17 no.1 s.74
• /
• pp.45-52
• /
• 2005

The object of this study was a cold-formed steel wall stud panel sheathed by gypsum boards. In the beam-analysis, the panel was treated as a simple beam with a uniform lateral loading. The deflections were calculated by considering the primary factors that reduced the stiffness of the panel. In the column-analysis, the panel was treated as a bearing wall with an axial load. By using an energy method, nominal axial strength could be evaluated by considering both flexural buckling and torsional-flexural buckling. All calculations were programmed and compared with the results of the experiment. In the beam-analysis, experimental deflections were close to theoretical deflections. In the column-analysis, the experimental values were also close to theoretical values in axial strength.

• Structural Engineering and Mechanics
• /
• v.32 no.6
• /
• pp.705-724
• /
• 2009

The two major widely used building design code documents of reinforced concrete structures are the ACI 318-05 and Eurocode for the Design of Concrete Structures EC2. Therefore, a thorough comparative analysis of the provisions of these codes is required to confirm their validity and identify discrepancies in either code. In this context, provisions of flexural computations would be particularly attractive for detailed comparison. The provisions of safety concepts, design assumptions, cross-sectional moment capacity, ductility, minimum and maximum reinforcement ratios, and load safety factors of both the ACI 318-05 and EC2 is conducted with parametric analysis. In order to conduct the comparison successfully, the parameters and procedures of EC2 were reformatted and defined in terms of those of ACI 318-05. This paper concluded that although the adopted rationale and methodology of computing the design strength is significantly different between the two codes, the overall EC2 flexural provisions are slightly more conservative with a little of practical difference than those of ACI 318-05. In addition, for the limit of maximum reinforcement ratio, EC2 assures higher sectional ductility than ACI 318-05. Overall, EC2 provisions provide a higher safety factor than those of ACI 318-05 for low values of Live/Dead load ratios. As the ratio increases the difference between the two codes decreases and becomes almost negligible for ratios higher than 4.

• Restorative Dentistry and Endodontics
• /
• v.38 no.1
• /
• pp.36-42
• /
• 2013

Objectives: This study evaluated the antibacterial effect and mechanical properties of composite resins ($L_{CR}$, $M_{CR}$, $H_{CR}$) incorporating chitosan with three different molecular weights (L, Low; M, Medium; H, High). Materials and Methods: Streptococcus (S). mutans 100 mL and each chitosan powder were inoculated in sterilized 10 mL Brain-Heart Infusion (BHI) solution, and was centrifuged for 12 hr. Absorbance of the supernatent was measured at $OD_{660}$ to estimate the antibacterial activities of chitosan. After S. mutans was inoculated in the disc shaped chitosan-containing composite resins, the disc was cleansed with BHI and diluted with serial dilution method. S. mutans was spread on Mitis-salivarius bacitracin agar. After then, colony forming unit (CFU) was measured to verify the inhibitory effect on S. mutans biofilm. To ascertain the effect on the mechanical properties of composite resin, 3-point bending and Vickers hardness tests were done after 1 and 3 wk water storage, respectively. Using 2-way analysis of variance (ANOVA) and Scheffe test, statistical analysis was done with 95% significance level. Results: All chitosan powder showed inhibition effect against S. mutans. CFU number in chitosan-containing composite resins was smaller than that of control resin without chitosan. The chitosan containing composite resins did not show any significant difference in flexural strength and Vickers hardness in comparison with the control resin. However, the composite resin, $M_{CR}$ showed a slightly decreased flexural strength and the maximum load than those of control and the other composite resins $H_{CR}$ and $L_{CR}$. Conclusions: $L_{CR}$ and $H_{CR}$ would be recommended as a feasible antibacterial restorative due to its antibacterial nature and mechanical properties.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.6
• /
• pp.204-211
• /
• 2022

In this study, Hollow Concrete Filled FRP Tube Pile(HCFFT Pile) was proposed as a model to utilize the advantages of composite piles and solve the problem of corrosion, which is a disadvantage of CFT piles, and a numerical analysis model was developed to analyze their behavior. The strain compatibility method was applied considering the damage plastic behavior of concrete, the yield plastic behavior of steel, and the elastic behavior of FRP. The flexural strength calculation equation of HCFFT piles was proposed considering the change of the FRP tube section according to the distance from the neutral axis. The flexural strength calculation equation, numerical analysis results, and experimental results were compared and analyzed to verify their adequacy. The results of this study can be used as basic data for the optimal design of various HCFFT piles using FRP.

• Steel and Composite Structures
• /
• v.38 no.6
• /
• pp.705-716
• /
• 2021

An innovative partially precast partially encased composite beam (PPECB) is put forward based on the existing research. In order to study the flexural performance of the new composite beam which has precast part and cast-in-place part, six prefabricated specimens and one cast-in-place specimen are designed with considering the influence of the production method, the steel flange thickness, the concrete strength grade and the stirrup process on the behavior of the composite beam. Through four points loading and test data collection and analysis, the behavior of partially prefabricated specimen is similar to that of cast-in-place specimen, and the casting method, the thickness of the steel flange, the concrete strength grade and the stirrup process have different influence on the crack, yield and peak load bearing capacity of the component. Finally, the calculation theory of plastic bending of partially precast partially encased concrete composite beams is given. The calculation results are in good agreement with the experimental results, which can be used for practical engineering theory guidance. This paper can provide reference value for further research and engineering application.

• Advances in concrete construction
• /
• v.11 no.2
• /
• pp.173-181
• /
• 2021

The main objective of this work is to contribute to the valorization of plastic and glass waste in the improvement of concrete properties. Waste glass after grinding was used as a partial replacement of the cement with a percentage of 15%. The plastic waste was cut and introduced as fibers with 1% by the total volume of the mixture. Mechanical and durability tests were conducted for various mixtures of concrete as compressive and flexural strengths, water absorption, ultrasonic pulse velocity, and acid attack. Also, other in-depth analyses were performed on samples of each variant such as X-ray diffraction (XRD), thermogravimetric analysis (DSC-TGA), and scanning electron microscope (SEM). The results show that the addition of glass powder or plastic fibers or a combination of both in concrete improved in the compression and flexural strengths in the long term. The highest compressive strength was obtained in the mix which combines the two wastes about 26.72% of increase compared to the control concrete. The flexural strength increased in the mixture containing the glass powder. Therefore, the mixture with two wastes exhibits better resistance to aggressive sulfuric acid attack, and incorporating glass powder improves the ultrasonic pulse velocity.

• Steel and Composite Structures
• /
• v.8 no.5
• /
• pp.423-438
• /
• 2008

This paper reports an experimental investigation of the behaviour of concrete-encased composite columns subjected to short-term axial load and biaxial bending. In the study, six square and four L-shaped cross section of both short and slender composite column specimens were constructed and tested to examine the load-deflection behaviour and to obtain load carrying capacities. The main variables in the tests were considered as eccentricity of applied axial load, concrete compressive strength, cross section, and slenderness effect. A theoretical procedure considering the nonlinear behaviour of the materials is proposed for determination of the behaviour of eccentrically loaded short and slender composite columns. Two approaches are taken into account to describe the flexural rigidity (EI) used in the analysis of slender composite columns. Observed failure mode and experimental and theoretical load-deflection behaviour of the specimens are presented in the paper. The composite column specimens and also some composite columns available in the literature have been analysed and found to be in good agreement with the test results.

• Journal of Korean Society of Steel Construction
• /
• v.16 no.1 s.68
• /
• pp.1-10
• /
• 2004

A study on the evaluation of proper spacing and required flexural rigidity of cross beams in composite two I-section steel girder bridges without a lateral and sway bracing system was performed. Specifically, a 2-lane, 40-m simple span bridge and a 3-span continuous (40+50+10m) bridge were designed, and structural analyses under dead load before and after composite, live, wind, and seismic loads were performed using spacing and flexural rigidity or cross beams as parameters. Through parametric analysis, the effect on the stresses due to the combination of loads and live load distribution was investigated. In addition. material and geometric nonlinear analyses under dead load before composite were performed to evaluate the lateral buckling strength of the steel girders and cross beam. Based on the results or such analyses, the proper spacing and flexural rigidity of cross beams at intermediate points and supports were proposed.

• Structural Engineering and Mechanics
• /
• v.78 no.3
• /
• pp.231-253
• /
• 2021

Pure bending loading conditions are not frequently occurred in practical engineering, but the flexural researches are important since it's the basis of mechanical property researches under complex loading. Hence, the objective of this paper is to investigate the flexural behavior of concrete-filled rectangular steel tube (CFRT) through combined experimental and numerical studies. Flexural tests were conducted to investigate the mechanical performance of CFRT under bending. The load vs. deflection curves during the loading process was analyzed in detail. All the specimens behaved in a very ductile manner. Besides, based on the experimental result, the composite action between the steel tube and core concrete was studies and examined. Furthermore, the feasibility and accuracy of the numerical method was verified by comparing the computed results with experimental observations. The full curves analysis on the moment vs. curvature curves was further conducted, where the development of the stress and strain redistribution in the steel tube and core concrete was clarified comprehensively. It should be noted that there existed bond slip between the core concrete and steel tube during the loading process. And then, an extensive parametric study, including the steel strength, concrete strength, steel ratio and aspect ratio, was performed. Finally, design formula to calculate the ultimate moment and flexural stiffness of CFRTs were presented. The predicted results showed satisfactory agreement with the experimental and FE results. Additionally, the difference between the experimental/FE and predicted results using the related design codes were illustrated.

• Journal of the Korea Concrete Institute
• /
• v.24 no.5
• /
• pp.585-596
• /
• 2012

In this study, the flexural characteristics of reinforced polymer concrete T-beams strengthened with GFRP, typically used for bridges and parking structures, are investigated. A method to determine the flexural failure mode of reinforced polymer concrete T-beams comprised of compression failure (CF), tension failure (TF), and fiber sheet failure (FF) for different levels of GFRP strengthening is proposed. Moreover, the present study provides a formula to calculate the design flexural strength for each failure mode. In reinforced polymer concrete T-beams strengthened with GFRP, an ideal failure mode can be achieved when the failure occurs in the following order: 1) yield of steel reinforcement, 2) failure of GFRP, and 3) compression failure of concrete. In the case of FF mode, due to GFRP failure before the polymer concrete crushing in compression region, a concept of equivalent rectangular block based on the ultimate limit state of concrete should not be used. Thus, this study suggests an idealized stress-strain curve for polymer concrete and finds parameters for stress block, ${\alpha}$ and ${\beta}$ based on the strain distribution in polymer concrete. Furthermore, the present study suggests an aspect ratio of 2.5 by examining the compressive stress distribution and design flexural strength characteristics for different aspect ratio of T-beams. This study also provides a design flexural strength formula, and validates its acceptability based on experiment and theoretical analysis.