• Structural Engineering and Mechanics
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• v.73 no.5
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• pp.529-542
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• 2020

As limited well-documented experimental data are available for assessing the attributes of different deformation components of flanged walls, few appropriate models have been established for predicting the inelastic responses of flanged walls, especially those of asymmetrical flanged walls. This study presents the experimental results for three large-scale T-shaped reinforced concrete walls and examines the variations in the flexural, shear, and sliding components of deformation with the total deformation over the entire loading process. Based on the observed deformation behavior, a simple model based on moment-curvature analysis is established to estimate flexural deformations, in which the changes in plastic hinge length are considered and the deformations due to strain penetration are modeled individually. Based on the similar gross shapes of the curvature and shear strain distributions over the wall height, a proportional relationship is established between shear displacement and flexural rotation. By integrating the deformations due to flexure, shear, and strain penetration, a new load-deformation analytical model is proposed for flexure-dominant flanged walls. The proposed model provides engineers with a simple, accurate modeling tool appropriate for routine design work that can be applied to flexural walls with arbitrary sections and is capable of determining displacements at any position over the wall height. By further simplifying the analytical model, a simple procedure for estimating the ultimate displacement capacity of flanged walls is proposed, which will be valuable for performance-based seismic designs and seismic capacity evaluations.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.45-53
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• 2019

Slump flow, compressive strength, flexural strength and drying shrinkage were measured to evaluate workability and mechanical performance of geopolymer. Experimental parameters include the addition of gypsum, blending ratio of blast furnace slag and fly ash and addition of shrinkage reducing agent. Geopolymer using blast furnace slag mixed with gypsum showed larger slump flow than blast furnace slag without gypsum. The slump flow when blending ratio of blast furnace slag and fly ash is 5:5 tended to be larger than the slump flow when blending ratio is 8:2. Geopolymer using blast furnace slag without gypsum showed higher compressive strength and flexural strength than blast furnace slag mixed with gypsum. Compressive strength and flexural strength tended to be higher when blending ratio of blast furnace slag and fly ash was 8:2 than when blending ratio was 5:5. Drying shrinkage decreased with increasing fly ash and blast furnace slag without gypsum, and it was found that shrinkage reducing agent is effective to reduce drying shrinkage of geopolymer.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.6
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• pp.363-370
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• 2021

In this paper, we presented an optimized crack and flexural strength analysis of a glass-fiber reinforced polymer (GFRP) rebar, used as reinforcements for in-site railway concrete slabs. The insulation performance of a GFRP rebar has the advantage of avoiding the loss of signal current in an audio frequency (AF) track circuit. A full-scale experiment, and three-dimensional finite element simulation results were compared to validate our approaches. Parametric numerical results revealed that the diameters and arrangements of the GFRP rebar had a significant effect on the flexural strength and crack control performances of the concrete track slabs. The results of this study could serve as a benchmark for future guidelines in designing more efficient, and economical concrete slabs using the GFRP rebar.

• Advances in concrete construction
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• v.13 no.5
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• pp.349-360
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• 2022

The rising prices of landfills and the lack of cement production are motivating researchers to be more interested in using wastes to produce concrete mixtures materials. The use of waste materials such as eggshell and matakoline waste not only reduces landfill costs and space, but also reduces the cost of cement production for the concrete mixture. However, recycling waste materials has become critical in order to effectively manage environmental sustainability. The purpose of this paper is to investigate the appropriate properties of self-compacting concrete (SCC) by incorporating waste materials such as crushed ceramics as coarse aggregate and nano egg shell (NES) and nanoclay (NC) as cement replacements. Fresh properties of SCC, such as segregation, flow time and diameter, V-funnel, H2/H1 ratio, and fresh unit weight of concrete mixtures, as well as hardened properties, such as 7, 14, and 28 days compressive strength and 28 and 90 days flexural strength, were measured for this purpose. The presence of NC in the SCC mixture enhanced the compressive strength of the concrete when 5% of NES was added or in the case without the addition of NES compared to the control mixture. The flexural strength enhanced with the incorporation of NC in the SCC increased the flexural strength of the concrete compared to the control mixture, but the incorporation of 5% of NES decreased the flexural strength compared to the mixtures with NC. These results prove the possibility of using crushed ceramics as the coarse aggregate, and NES and NC as substitutes for 5, 7, and 10% of the cement in SCC, because the properties of such SCC in hardened and fresh states are satisfactory.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.539-546
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• 2006

The reliability analysis of simply-supported composite plate girder and box girder bridges under positive flexure is performed. The bridges are designed based on the AASHTO-LRFD specification. A performance function for flexural failure is expressed as a function of such random variables as flexural resistance of composite section and design moments due to permanent load and live load. For the flexural resistance, the statistical parameters obtained by analyzing over 16,000 samples of domestic structural steel products are used. Several different values of statistical parameters with the bias factor in the range of 0.95-1.05 and the coefficient of variation in the range of 0.15-0.25 are used for the live-load moment. Due to the lack of available domestic measured data on the dead load moment, the same values of statistical properties used in the calibration of AASHTO-LRFD are applied. The reliability indices for the composite plate girder and box girder bridges with various span lengths are calculated by applying the Rackwitz-Fiessler technique.

• Steel and Composite Structures
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• v.37 no.3
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• pp.259-272
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• 2020

In this study a new hysteretic damper for seismic retrofit of soft-first story structures is proposed and its seismic retrofit effect is evaluated. The damper consists of one steel column member and two flexural fuses at both ends made of steel plates with reduced section, which can be placed right beside existing columns in order to minimize interference with passengers and automobiles in the installed bays. The relative displacement between the stories forms flexural plastic hinges at the fuses and dissipate seismic energy. The theoretical formulation and the design procedure based on plastic analysis is provided for the proposed damper, and the results are compared with a detailed finite-element (FE) model. In order to apply the damper in structural analysis, a macromodel of the damper is also developed and calibrated by the derived theoretical formulas. The results are compared with the detailed FE analysis, and the efficiency of the damper is further validated by the seismic retrofit of a case study structure and assessing its seismic performance before and after the retrofit. The results show that the proposed hysteretic damper can be used effectively in reducing damage to soft-first story structures.

• Structural Engineering and Mechanics
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• v.66 no.5
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• pp.631-636
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• 2018

This study aims to investigate the flexural behaviour of glass fibre reinforced polymer (GFRP) laminated hybrid fibre reinforced concrete (HFRC) beams. The flexural and ductility performance of GFRP laminated HFRC beams having different proportions of polyolefin and steel fibres with 1.0% of total volume fraction were investigated. The parameters of this investigation included: load and deflection at first crack, yield, and ultimate stages, ductility and crack width. A total of seven beams of $150{\times}250mm$ in cross-section were tested in the laboratory over an effective span of 2800 mm. One reinforced concrete (RC) beam without any internal or external GFRP was taken as the reference beam. Of the remaining six beams, one beam was strengthened with GFRP, one beam with 100% steel fibres was strengthened with GFRP and four beams, each with different volume proportions of polyolefin and steel fibres (20:80, 30:70, 40:60, 50:50) were strengthened with GFRP. All the above beams were tested until failure. The experimental results show that a fibre volume proportion of 40:60 (polyolefin-steel) has significantly improved the overall performance of the tested beams.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.1-7
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• 2015

As energy consumption of building and the reduction of carbon dioxide emissions have been emphasized, phase change materials(PCM) have been introduced as building materials due to its high heat storage performance. Using shape-stabilizing technique, octadecane/xGnP shape-stabilized PCM(SSPCM) can prevent leakage and improve heat storage performance. The objectives of this study are to propose mix design method of concrete mixed with SSPCM and to evaluate mechanical behaviors of the concrete mixed with SSPCM manufactured according to the proposed mix design. Based on the previously reported material test result, the existing mix design of plain concrete(Concrete standard specification, 2009) is modified to consider reduction of strength in concrete due to the addition of SSPCM. To verify the proposed mix design, specimens are fabricated according to the proposed mix design and axial strength tests and three-point loading tests are performed. Test results show that compressive strengths of the tested specimens reach the designed strength even when two different mix ratios of SSPCM are used. From three-point loading tests, flexural stresses decrease as mix ratio of SSPCM increases.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.281-284
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• 2008

Recently, interest in eco-friendly structure has been increased and many researches about hwang-toh are being actively processed. However, most researches are about material properties of hwang-toh, and researches about structural performance are insufficient. Moreover, the usability of activated hwang-toh is being identified in some ways, but its use rate is low in economic aspect in reality. Non-activated hwang-toh is expected to be advantageous in respect of economy but its material and structural performance have not been identified. Therefore, the effect of activated hwang-toh and non-activated hwang-toh on flexural capacity of hwang-toh concrete beam is analyzed in this research.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.306-311
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• 1996

This paper persents the flexural behavior of high performance concrete beams having different concrete filling conditions. Three tests were conducted on full-scale beam specimens with design concrete compressive strength of 400 kg/$\textrm{cm}^2$. Different concrete filling conditions were intentionally made such that the first beam specimen was soundly cast to obtain the perfect concrete filling condition. Second beam specimen was cast in such a way that up to the longitudinal tensile reinforcement from the top, good concrete was filled while poor concrete was poured for the bottom part to simulate the poor workamanship, workability and unsatisfactory compaction. Third beam specimens was cast in such a way that up to the neutral axis of the beam section from the top, good concrete was filled while so did for the bottom part as the second beam specimen. The test results were analyzed in terms of load-displacement response, formation of crack, crack width, crack spacing and shift of neutral axis. An evaluation of the ductile response fo three different beam specimens was made in combination with the ultimate load accoding to the three different concrete filling conditions.