• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.349-354
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• 2000

While a little research has been performed on flexural behavior of reinforced polymer concrete (RPC) beams with the compressive strength lower than 1000kg/$\textrm{cm}^2$, vary little exists in conjunction with the behavior of (RPC) 1,400kg/$\textrm{cm}^2$ or compressive strength. In this paper the flexural behavior of high strength polymer concrete beams with 1,400kg/$\textrm{cm}^2$ in compressive was evaluated. The unsaturated polyester resin was used to make polymer concrete as binder. The beams with stirrup singly/doubly were rested to examine the effect of tensile reinforcement ratio. As test results. steel ratio increased with the increased moment strength, decreased with ultimate deflection.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.98-99
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• 2020

This study is aim to assess mechanical properties which is highly related to structural safe and durability of 100MPa high strength concrete mixed with amorphous metallic fiber. All specimens were heated with low velocity heating rate(1℃/min.), residual compressive strength and residual flexural strength was evaluated. The specimens were cooled down to room temperature after heating. As a result, in the case of 100MPa high-strength concrete, the residual compressive strength enhancing effect of amorphous metallic fiber has showed with the mix proportion of fiber. In addition, residual flexural strength showed more regular pattern before 300℃ then residual compressive strength, but simillar decreasing behavior was shown after 300℃ like residual compressive strength. Further study about fiber pull-out behavior and fiber mechanical, chemical property change due to temperature is needed.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.437-438
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• 2010

This study was carry out to evaluate the effect of flexural behavior according to using hybrid steel fiber in UHPC. The evaluation of the flexural behavior of UHPC using hybrid fibers showed that the admixing of hybrid steel fibers at a volumic ratio of 2% increased the flexural strength by more than 27% (maximum 50%) compared to the use of steel fibers only. A ratio of 1.5% was seen to provide flexural strength exceeding the current strength of UHPC.

• Structural Engineering and Mechanics
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• v.75 no.1
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• pp.49-57
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• 2020

This paper presents a full-scale experimental test to investigate the flexural behavior of an innovative dovetail ultra-high performance concrete (UHPC) joint designed for the 5^th Nanjing Yangtze River Bridge. The test specimen had a dimension of 3600 × 1600 × 170 mm, in accordance with the real bridge. The failure mode, crack pattern and structural response were presented. The ductility and stiffness degradation of the tested specimens were explicitly discussed. Test results indicated that different from conventional reinforced concrete slabs, well-distributed cracks with small spacing were observed for UHPC joint slabs at failure. The average nominal flexural cracking strength of the test specimens was 7.7 MPa, signifying good crack resistance of the proposed dovetail UHPC joint. It is recommended that high grade reinforcement be cooperatively used to take full advantage of the superior mechanical property of UHPC. A new ductility index, expressed by dividing the ultimate deflection by flexural cracking deflection, was introduced to evaluate the post-cracking ductility capacity. Finally, a strut-and-tie (STM) model was developed to predict the ultimate strength of the proposed UHPC joint.

• Structural Engineering and Mechanics
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• v.38 no.5
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• pp.675-696
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• 2011

It is difficult to accurately predict the flexural strength of prestressed members with unbonded tendons, unlike that of prestressed members with bonded tendons, due to the unbonded behavior between concrete and tendon. While there have been many studies on this subject, the flexural strength of prestressed members with unbonded tendons is still not well understood, and different standards in various countries often result in different estimation results for identical members. Therefore, this paper aimed to observe existing approaches and to propose an improved model for the ultimate strength of prestressed members with unbonded tendons. Additionally, a large number of tests results on flexural strength of prestressed members with unbonded tendons were collected from previous studies, which entered into a database to verify the accuracy of the proposed model. The proposed model, compared to existing approaches, well estimated the flexural strength of prestressed members with unbonded tendons, adequately reflecting the effects of influencing factors such as the reinforced steel ratio, the loading patterns, and the concrete strength. The proposed model also provided a reasonably good estimation of the ultimate strength of over-reinforced members and high-strength concrete members.

• Computers and Concrete
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• v.12 no.6
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• pp.819-829
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• 2013

The objective of this study is to determine whether or not the yield line theory, an effective method widely used for slabs made of ordinary concrete, can be used also for the reinforced concrete slabs made of high-strength concrete. Flexural behavior of simply supported slabs in three different sizes were investigated under concentrated load at mid-span. Additionally, behavior of high strength reinforced concrete slabs with 50 mm and 150 mm reinforcement spacings also studied. Failure loads, deflections, experimental and theoretical failure mechanisms were evaluated. The difference between the moments based on yield line theory and experimental moments varied between 1% to 3%. Experimental and analysis results revealed that yield line analysis could conveniently be employed in the analysis of high strength reinforced concrete slabs.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.339-342
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• 2005

This paper presents flexural test results of concrete beams reinforced with GFRP and conventional steel reinforcement for comparison. The beams were tested under static loading to investigate the effects of reinforcement ratio and compressive ,strength of concrete on cracking, deflection, ultimate capacity and mode of failure, This study attempts to establish a theoretical basis for the development of simple and rational design guideline. Test results show that ultimate capacity increases as the reinforcement ratio and concrete strength increase. The ultimate capacity increased up to $8\%-25\%$ by using high strength concrete. The deflection at maximum load of GFRP reinforced beams was about three times that of steel reinforced beams. For GFRP-reinforced beams, the ACI code 440 design method resulted in conservative flexural strength -estimates.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.152-163
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• 2019

In this paper, effect of steel fiber inclusion, compressive strength of matrix, shear reinforcement and shear span to depth ratio on the flexural behavior of UHPFRC(Ultra High Performance Fiber Reinforced Concrete) were investigated with test of 10-UHPFRC beam specimens. All test specimens were subjected to the flexural static loading. It was shown that steel fiber significantly improve the shear strength of UHPFRC beams. 2% volume fraction of steel fiber change the mode of failure from shear failure to flexural failure and delayed the failure of compressive strut with comparatively short shear span to depth ratio. UHPFRC beams without steel fiber had a 45-degree crack angle and fiber reinforced one had lower crack angle. Shear reinforcement contribution on shear strength of beams can be calculated by 45-degree truss model with acceptable conservatism. Using test results, French and Korean UHPFRC design recommendations were evaluated. French recommendation have shown conservative results on flexural behavior but Korean recommendation have shown overestimation for flexural strength. Both recommendations have shown the conservatism on the flexural ductility and shear strength either.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.157-162
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• 2003

An experimental investigation was conducted to study the behavior of high-strength RC wide beam-column joints with slab subjected to reversed cyclic loads under constant axial load. Six half scale interior wide beam-column assemblies representing a portion of a frame subjected to simulated seismic loading were tested, including three specimens without slab and three specimens with slab. The primary variables were compressive strength of concrete($f_ck$=285, 460kgf/$cm^2$), the ratio of the column-to-beam flexural capacity($M_r$=$\Sigma M_c / \Sigma M_b$ ; 0.77 -2.26), extended length of the column concrete($l_d$ ; 0, 12.5, 30cm), ratio of the column-to-beam width(b/H ; 1.54, 1.67). Test results are shown that (1) the behavior of specimen using high-strength concrete satisfied for required minimum ductile capacity according to increase the compressive strength, (2) the current design code and practice for interior joints(type 2) are apply to the wide beam-high strength concrete column.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.3
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• pp.43-50
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• 2019

Effects of tensile strength and aspect ratio of steel fiber on compressive and flexural behavior of steel fiber-reinforced concrete (SFRC) with high- and normal-strength were investigated. Also, this study explores compressive behavior of SFRC with different loading rate. For this purpose, four types of steel fiber were used for SFRC with specified compressive strength of 35 and 60 MPa, respectively. Cylindrical specimens with a diameter of 150 mm and height of 300 mm were made for compression test, and prismatic specimens with a $150{\times}150mm$ cross-section and 450 mm span length were made for flexural test. Test results from compression and flexural tests indicated that the toughness of concrete significant increased with steel fibers. Especially, using steel fiber with high tensile strength and aspect ratio can be lead to performance improvement of high-strength SFRC. In this study, equations are suggested to predict compressive toughness ratio of SFRC from flexural toughness ratio.