• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.429-432
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• 2006

In this study a board was made with good fireproof materials of which test was conducted according to the fireproof test for KS F 2257 construction members, and the temperature in coated steel which has a possibility to explode with concrete surface was measured. It is not appropriate to use normal mortar or mortar covering mixed with P.P. fiber to take a measure to prevent the explosive splalling of high-strength concrete. To finalize an Al-Si (aluminosilicates) board-requires over 30mm in thickness at the minimum for the required fire resistance performance and explosion prevention.

• Advances in concrete construction
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• v.10 no.6
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• pp.479-488
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• 2020

The experimental and numerical works were carried out on high performance fiber reinforced concrete (HPFRC) with w/cm ratios ranging from 0.25 to 0.40, fiber volume fraction (Vf)=0-1.5% and 10% silica fume replacement. Improvements in compressive and flexural strengths obtained for HPFRC are moderate and significant, respectively, Empirical equations developed for the compressive strength and flexural strength of HPFRC as a function of fiber volume fraction. A relation between flexural strength and compressive strength of HPFRC with R=0.78 was developed. Due to the complex mix proportions and non-linear relationship between the mix proportions and properties, models with reliable predictive capabilities are not developed and also research on HPFRC was empirical. In this paper due to the inadequacy of present method, a back propagation-neural network (BP-NN) was employed to estimate the 28-day compressive strength of HPFRC mixes. BP-NN model was built to implement the highly non-linear relationship between the mix proportions and their properties. This paper describes the data sets collected, training of ANNs and comparison of the experimental results obtained for various mixtures. On statistical analyses of collected data, a multiple linear regression (MLR) model with R2=0.78 was developed for the prediction of compressive strength of HPFRC mixes, and average absolute error (AAE) obtained is 6.5%. On validation of the data sets by NNs, the error range was within 2% of the actual values. ANN model has given the significant degree of accuracy and reliability compared to the MLR model. ANN approach can be effectively used to estimate the 28-day compressive strength of fibrous concrete mixes and is practical.

• Advances in concrete construction
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• v.17 no.1
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• pp.1-12
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• 2024

Precast deck joints have problems due to the occurrence of additional processes at construction sites, the complexity of construction, and the lack of design and construction standards for precast deck joints. To solve these, this study proposes a new precast deck joint that uses an Ultra-High-Performance Fiber-reinforced Cement Composite (UHPFRCC) filling material containing steel fibers and a straight rebar joint. In addition, the structural performance of the proposed joint, based on various parameters, was compared to that of existing precast deck joints, and the proposed joint showed equivalent strength and ductility. Therefore, the proposed joint can solve construction site problems by replacing the existing ones. The influence of various variables is expected to provide basic data on the design and construction guidelines for the precast deck joints.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.499-502
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• 2005

Nowadays, the stripping work of form has generated some problems such as increasing total constructing cost result from delayed work schedule by the stripping work of form and environmental issues by wasting the debonded form. According to recent research for form work, it has studied about permanent form to solve economic and environmental problem which is commented above. In this study, high performance permanent form method was developed and tested by adopting COM and TEN specimens adopted on the Compression and Tensile section then the structural behaviour was investigated. In the test result, the specimen adopted the form showed better structural performance than control specimen in the point of ductility, failure mode and ultimate load.

• Structural Engineering and Mechanics
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• v.82 no.3
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• pp.313-323
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• 2022

Steel laminated elastomeric bearings are commonly used in bridge structures to control displacements and rotations and transfer forces from the superstructure to the substructure. Proper knowledge of design, fabrication and erection procedures is important to ensure stability and adequate structural performance during the lifetime of the bridge. Difference in elevations sometimes leads to large size gaps between the bearing and the girder which makes the grout thickness that is commonly used for leveling deviate beyond standards. This paper investigates the structural response of High Strength Fiber Reinforced Cementitious (HSFRC) thin plinths that are used to close gaps between bearing pads and precast girders. An experimental program was developed for this purpose where HSFRC plinths of different size were cast and tested under vertical loads that simulate bridge loading in service. The structural performance of the plinths was closely monitored during testing, mainly crack propagation, vertical reaction and displacement. Analytically, the HSFRC plinth was analyzed using the beam on elastic foundation theory as the supporting elastomeric bearing pads are highly compressible. Closed form solutions were derived for induced displacement and forces and comparisons were made between analytical and experimental results. Finally, recommendations were made to facilitate the practical use of HSFRC plinths in bridge construction based on its enhanced load carrying capacity in shear and flexure.

• Advances in concrete construction
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• v.13 no.2
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• pp.153-162
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• 2022

Prefabricated exterior wall panel is the main non-load-bearing component of assembly building, which affects the comprehensive performance of thermal insulation and durability of the building. It is of great significance to develop new prefabricated exterior wall panel with durable and lightweight characteristics for the development of energy-saving and assembly building. In the prefabricated sandwich insulation hanging wall panel, the selection of material for the outer layer and the arrangement of the connector of the inner and outer wall layers affect the mechanical performance and durability of the wall panels. In this paper, high performance cement-based composites (HPFRC) are used in the outer layer of the new type wall panel. FRP bars are used as the interface connector. Through experiments and analysis, the influence of the arrangement of connectors on the mechanical behaviors of thin-walled composite wall panel and the panel with window openings under two working conditions are investigated. The failure modes and the role of connectors of thin-walled composite wallboard are analyzed. The influence of the thickness of the wall layer and their combination on the strain growth of the control section, the initial crack resistance, the ultimate bearing capacity and the deformation of the wall panels are analyzed. The research work provides a technical reference for the engineering design of the light-weight thin-walled and durable composite sandwich wall panel.

• Computers and Concrete
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• v.16 no.1
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• pp.1-16
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• 2015

The proposed techniques to strengthen concrete members such as steel plates, polymers or concrete have important deficiencies in adherence and durability. The use of UHPFC plates can overtake effectively these problems. In this paper, the possibility of using UHPFC to strengthen RC beams under torsion is investigated. Four specimens of concrete beams reinforced with longitudinal bars only were tested under pure torsion. One of the beams was considered as the baseline specimen, while the others were strengthened by ultra-high-performance fiber concrete (UHPFC) on two, three, and four sides. Finite element analysis was conducted in tandem with experimental work. Results showed that UHPFC enhances the strength, ductility, and toughness of concrete beams under torsional load, and that finite element analysis is in good agreement with the experimental data.

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.705-712
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• 2009

HPFRCCs (high-performance fiber reinforced cementitious composites), which is relatively more ductile and has the characteristic of high toughness with high fiber volume fractions, can be used in structures subjected to extreme loads and exposed to durability problems. In the case of PVA (polyvinyl alcohol) fiber, it is noted by former studies that around 2% fiber volume fractions contributes to the most effective performance at HPFRCCs. In this study, flexural tests were carried out to evaluate the flexural behavior of HPFRCCs and to optimize mix proportions. Two sets of hybrid fiber reinforced high performance specimens with total fiber volume fraction of 2 % were tested: the first set prepared by addition of short and long PVA fibers at different combination of fiber volume fractions, and the second set by addition of steel. In addition, in order to assess the performances of the HPFRCCs against to high strain rates, drop weight tests were conducted. Lastly, the sprayed FRP was applied on the bottom surface of specimens to compare their impact responses with non-reinforcing specimens. The experimental results showed that the specimen prepared with 1.6% short fibers (REC 15) and 0.4% long fiber (RF4000) outperformed the other specimens under flexure, and impact loading.

• Journal of the Korean Society of Safety
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• v.29 no.6
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• pp.81-86
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• 2014

Composite materials have high specific stiffness, specific strength than existing concrete or steel materials. It has superior dynamic properties when utilizing advantages of material such as Non-corrosive, light weight, non-conducting and it has superior mold ability which can make variable shapes. Thus, in the construction, for using composite materials as construction materials, the study carried out static strength of fiber right angle direction and fatigue performance of FRP deck member. The study is going to deduct S-N curve by analyzing the results comparatively and estimate long-term durability. From now on, the study is going to provide interpretation of FRP member and basic data of design basis, furthermore providing foundation technique of composite materials' application of structural frame is the goal of this study.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.73-82
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• 2006

Nowadays, the general stripping work of form has brought some problems; increase of total constructing cost resulted from the man-dependent form work procedure and environmental issues by wasting the debonded form. In this study, to effectively reduce unnecessary cost and resolve the environmental problems caused by these kinds of reason, a permanent form method using stainless steel fiber was introduced then its material and structural characteristics were evaluated. In the case of material characteristic, the permanent form had a good ductile behavior in the result of flexural test of the permanent form panel and pull-out test of insert bolt which is installed in the permanent form and perfect bonding capacity with a field concrete. In the case of structural characteristic, compressive and tensile behavior of the permanent form was evaluated. It also showed a good structural behavior in the view of load-deflection relationship, crack patterns and additional strengthening effect.