• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.289-292
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• 2006

The purpose of this study was to evaluate a performance of latex-modified repair material applied to the substrate concrete. The experimental variables were latex-cement ratios (5, 10, 15%), polymer(0.5%, 1%) and admixtures. The flow, air content, compressive strength, flexural strength were tested. Test results showed that compressive and flexural strength decreased by adding hydroxyethyl cellulose and increasing water-binder ratio. The compressive and flexural strength were increased when addition of defoamer.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.5-6
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• 2009

In this study, with 2% of total PVA fiber volume fraction identically, flexural performances of ECC had long and short fibers were assessed. In the material tests, flexural properties of a mixture with 1.6% REC15 and 0.4% RF4000 were most superior. Quasi-static and dynamic tests with six 160${\times}$290${\times}$2300 mm specimens were carried out, and improvement of shear strength and performance of partial placing of ECC were estimated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.7
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• pp.923-929
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• 2004

A magnetostrictive sensor is a sensor measuring elastic waves. Because of its unique non-contact measurement feature, the sensor receives more attentions in recent years. These sensors have been mainly used to measure longitudinal and torsional waves in ferromagnetic waveguides, but there increases an interest in using the sensor for flexural wave measurement. Since the performance of the sensor is strongly influenced by the applied bias magnetic field distribution, the design of the bias magnetic system providing the desired magnetic field is critical. The motivation of this investigation is to design a bias magnetic system consisting of electromagnets and yokes and the specific objective is to formulate the design problem as a bias yoke topology optimization. For the formulation, we employ linear magnetic behavior and examine the optimized results for electromagnets located at various locations. After completing the design optimization, we fabricate the prototype of the proposed bias magnetic system, and test its performance through flexural wave measurements.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.833-838
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• 1998

This paper is aimed to investigate structural performance of flexural members enlarged with epoxy mortar at soffit. Main test variables are steel ratio and interface treatment method and six test beams are tested to investigate the effect of each test variables on maximum load capacity, load-deflection and moment-curvature relationship, interface behavior and failure mode. Test results show that section enlarged beams can carry almost same load of the monolithic beams with same size and the flexural stiffness and cracking moments are increased about 2.5 times and 50 to 70%of failure moment in comparison with same sized control beam, respectively. However, deflections and curvatures are decreased at the same load and interface fractures are not discovered at the ultimate load.

• Structural Engineering and Mechanics
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• v.89 no.1
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• pp.47-59
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• 2024

In this study, a new sustainable material was proposed to prepare precast tunnel lining segments (TLS), which were produced using a fiber-reinforced slag-based geopolymer composite. Slag was used as the geopolymer binder. In addition, polypropylene and carbon fibers were added to reinforce TLSs. TLSs were examined in terms of flexural performance, load-deflection response, ductility, toughness, crack characteristics, and tunnel boring machine (TBM) thrust force. Simultaneously, numerical simulation was performed using finite element analysis. The mechanical characteristics of the geopolymer composite with a fiber content of 1% were used. The results demonstrated that the flexural performance and load-deflection response of the precast TLSs were satisfactory. Furthermore, the numerical results were capable of predicting and realistically capturing the structural behavior of precast TLSs. Therefore, fiber-reinforced slag-based geopolymer composites can be applied as precast TLSs.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.5
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• pp.603-613
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• 2024

This study evaluated the mechanical properties of high-tension performance biochar concrete, focusing on the effects of varying biochar cement replacement ratios (0 %, 1 %, 2 %, 3 %, 4 %, and 5 %). Mechanical properties, including compressive strength, tensile strength, and flexural strength, were tested. The results showed a general decrease in compressive strength with increasing biochar replacement, with significant reductions at 1 % to 3 % levels. PVA fiber reinforcement improved long-term compressive strength, particularly at higher biochar levels. Tensile and flexural strength also showed initial reductions with low biochar levels but improved at higher replacement levels. PVA fibers consistently enhanced tensile and flexural strength. SEM images confirmed the integration of biochar and PVA fibers into the cement matrix, enhancing microstructural density and crack resistance.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.38-39
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• 2013

In this study, in regard to fiber reinforced mortar mixing steel fiber and 4types of organic fiber, impact test was carried out. Because to predict fracture reduction performance with flexural, tensile strength when types of fiber were different as impact reduction performance of concrete is closely related with toughness such as flexural strength, tensile strength and fracture energy etc. As a result, enhancement of toughness by fiber reinforcement controls the spall of rear. On the other hand in case of steel fiber relatively turned up high toughness in appropriate load compared with organic fiber but in same mixing rate, impact reduction performance by projectile showed low performance due to few number of an individual of mixing.

• Journal of the Korea Concrete Institute
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• v.23 no.2
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• pp.169-176
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• 2011

In this study, the flexural test for reinforced high performance fiber reinforced cementitious composites (R/HPFRCC) members has been conducted in order to investigate the flexural behavior including the effect of an ordinary tensile reinforcing bar. Through the test, it was observed that the flexural strength increased due to the stable tensile stress transfer of HPFRCC, even up to the ultimate state. In addition, no localized crack appeared until the yielding of the reinforcement. From the layered section analysis of the tested members, it was found that the analysis with the tensile model obtained from the tension stiffening test showed better agreement with the flexural test results, whereas the analysis with direct tension test results overestimated the flexural capacity. Through the experimental and analytical studies, two flexural failure modes have been defined in this paper; concrete crushing at the top compression layer or tensile failure at the bottom tensile layer of the beam section. Based on these two flexural failure modes, a simple formula that estimates the ultimate flexural strength of the member has been proposed in this paper. The proposed equations can be useful in a design and an analysis of R/HPFRCC members.

• Steel and Composite Structures
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• v.37 no.4
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• pp.431-446
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• 2020

This paper presents the flexural performance of double skin composite beams (DSCBs) at different Arctic low temperatures. 12 DSCBs were prepared and tested under two-point loading at different Arctic low temperatures of 20, -30, -50, and -70℃. The studied parameters include low-temperature level (T), steel-faceplate thickness (t), shear span ratio (λ), and spacing of headed studs (S). The experimental investigations under two-point loading tests showed that flexural failure occurred to all DSCBs, even including the specimen designed with the small λ ratio of 2.9. The ultimate strength behaviours of DSCBs were improved due to the improved mechanical properties of constructional materials and the confinement on shear connectors. The DSCB subjected to two-point loading and low temperatures exhibits a five-stage working mechanism. The stiffness and strength indexes of DSCBs increase linearly with temperature and t value increasing, while decreasing as shear span ratio boosts. In the contrast, the change of S value from 150 to 200 mm has little effect on the ultimate strength behavior of DSCB.

• Computers and Concrete
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• v.18 no.6
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• pp.1065-1082
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• 2016

The main aim of this study is to predict the compressive and flexural strengths of self-compacting mortar (SCM) containing $nano-SiO_2$, $nano-Fe_2O_3$ and nano-CuO using wavelet-based weighted least squares-support vector machines (WLS-SVM) approach which is called WWLS-SVM. The WWLS-SVM regression model is a relatively new metamodel has been successfully introduced as an excellent machine learning algorithm to engineering problems and has yielded encouraging results. In order to achieve the aim of this study, first, the WLS-SVM and WWLS-SVM models are developed based on a database. In the database, nine variables which consist of cement, sand, NS, NF, NC, superplasticizer dosage, slump flow diameter and V-funnel flow time are considered as the input parameters of the models. The compressive and flexural strengths of SCM are also chosen as the output parameters of the models. Finally, a statistical analysis is performed to demonstrate the generality performance of the models for predicting the compressive and flexural strengths. The numerical results show that both of these metamodels have good performance in the desirable accuracy and applicability. Furthermore, by adopting these predicting metamodels, the considerable cost and time-consuming laboratory tests can be eliminated.