• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.171-178
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• 2007

Twelve reinforced concrete continuous deep beams having web openings within interior shear spans were tested to failure. All beams tested had the same geometrical dimensions. The main variables investigated were the opening size and amount of inclined reinforcement around openings. An effective inclined reinforcement factor combining the influence of the opening size and amount of inclined reinforcement on the structural behavior of the beams tested is proposed. It was observed that the load distribution, diagonal crack width, and load capacity of beams tested were greatly dependent on the effective inclined reinforcement factor which ranged from 0 to 0.171 for the test specimens. The higher this factor, the smaller the diagonal crack width and its development rate. A higher load capacity also developed in beams having effective inclined reinforcement factor above 0.077 than in the corresponding solid deep beams. A numerical technique based on the upper bound analysis of the plasticity theory is proposed to evaluate the load capacity of continuous deep beams having openings within interior shear spans. Predictions obtained from the proposed formulas are in good agreement with test results.

• Journal of the Korea Concrete Institute
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• v.20 no.1
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• pp.99-107
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• 2008

This paper presents the prediction of the actual strength of shear reinforcement on the basis of the concept of effective stirrups. The prediction method incorporating the shear cracking angle was proposed with the estimation by the Modified Compression Field Theory (MCFT). To check the validity of the method, discussion of the current ACI 318-05 and comparison of 39 test results from the literature including author's retrospective test data were made. The influencing factors of compressive concrete strength and type of shear-reinforcement were also investigated. Furthermore, two full-scale beam specimens shear-reinforced with headed bars were tested to demonstrate the applicability of the proposed method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.1
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• pp.157-164
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• 2006

This paper presents the durability characteristics of commercially available CFRP rebars under various environmental conditions. Two types of GFRP rebars were tested by using an accelerated aging method. A total of 264 rebar specimens were conditioned up to 132 days in the moisture, chloride. alkaline, and freeze-thaw environmental conditions. The durability characteristics of conditioned rebars were obtained by comparing the tensile strength, horizontal shear strength, and elastic modulus between the unconditioned and conditioned GFRP rebars. The test results indicated that the mechanical properties of GFRP were significantly reduced after conditioning. Long-term degradation of GFRP rebars was also estimated using the results of a short-term durability test.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.4
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• pp.403-409
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• 2013

Shear behavior of concrete beams reinforced with steel and/or FRP bar is studied through experimental tests. Experimental parameters includes the mechanical properties of reinforcements in shear and bending, and the ratio of shear reinforcement. The validity of the modified truss analogy, that has been widely accepted as a basis for the practical shear design of concrete beams, has been examined thoroughly by analyzing experimental results. The experimental results indicate that the modified truss analogy cannot be directly adopted to the shear problem of concrete beams reinforced with FRP bar.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.2
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• pp.49-57
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• 2021

A study was conducted to secure structural performance as well as improve workability by improving the reinforcement details of special shear wall and coupling beams. Based on the specimen in which the existing diagonal bundle reinforcement and shear reinforcement were placed, the specimens replaced with thick diagonal reinforcing bars and the specimens replaced with horizontal reinforcing bars were selected as variables. As a result of the experiment, the specimen, which replaced the existing diagonal reinforcement with a thick-diameter reinforcement, showed a similar behavior to that of the basic specimen, and it was evaluated that it can be applied as an alternative to the details.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.2
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• pp.201-211
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• 2005

Due to the complex mechanism and various parameters that affect shear behavior of reinforced concrete (RC) members, models on shear tend to be complex and difficult to utilize for design of structural members, and empirical relationships formulated with limited test data often work lot members having a specific range of influencing parameters on shear. As an alternative approach tot solving this problem, artificial neural networks have been suggested by some researchers. In this paper, artificial neural networks were used to predict shear strengths of RC beams without shear reinforcement. Especially, a large database that consists of shear test results of 398 RC members without shear reinforcement was used for artificial neural network analysis. Three well known approaches for shear strength of RC members, ACI 318-02 shear provision, Zsutiy's equation, and Okamura's relationship, are also evaluated with test results in the shear database and compared with neural network approach. While ACI 318-02 provided inaccurate predictions for RC members without shear reinforcement, the empirical equations by Zsutty and Okamura provided more improved prediction of Shear strength than ACI 318-02. The artificial neural networks, however provided the best prediction of shear strengths of RC beams without shear reinforcement that was closest to test results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.2
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• pp.76-82
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• 2006

The concrete shear strength of FRP Bar reinforced concrete beam according to the variation of flexural reinforcement ratio was investigated. A number of experimental result showed that the concrete shear strength was lower than that of RC beam, but it was increased according to the increasement of reinforcement ratio. Shear strength correction factors considering the kind and reinforcement ratio of FRP Bar was proposed using the proposed formula in the literature and regression analysis of the experimental result.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.811-819
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• 2003

The corrosion of steel reinforcing bar(re-bar) has been the major cause of the reinforced concrete deterioration. FRP(Fiber-reinforced polymer) reinforcing bar has emerged as one of the most promising and affordable solutions to the corrosion problems of steel reinforcement in structural concrete. However, FRP re-bar is pone to deteriorate due to other degradation mechanisms than those for steel. The high alkalinity of concrete, for instance, is a possible degradation source. Other potentially FRP re-bar aggressive environments are sea water, acid solution and fresh water/moisture. In this study long-term durability performance of FRP re-bar were evaluated. The mechanical and durability properties of two type of CFRP-, GFRP re-bar and one type of AFRP re-bar were investigated; the FRP re-bars were subjected to alkaline solution acid solution, salt solution and deionized water. The mechanical and durability properties were investigated by performing tensile, compressive and short beam tests. Experimental results confirmed the desirable resistance of FRP re-bar to aggressive chemical environment.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.45-51
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• 2013

Short beam tests of GFRP and CFRP specimens exposed to high temperature were conducted to measure the inter-laminar shear strength. For the phase I test, the exposure time and temperature were varied to measure reduction in the strength due to the applied conditions. As a results, the critical temperature was found to $270^{\circ}C$ for the both FRP reinforcements. The high temperature, which causes 50% loss of inter-laminar shear strength, is defined as the critical temperature in this study. It should be noted that the critical temperature for the inter-laminar shear strength is mainly dependent on resin properties not on fiber type. In the phase II test, the effect of exposure time was investigated at intervals of 0.25hour for the critical temperature. All test results demonstrate that the exposure time effect is not significant compared to the maximum exposure temperature, but it is not negligible and, moreover, is significant at the critical temperature.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.313-324
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• 2010

There are many problems in application of FRP reinforcing bars as shear reinforcement, since bending of FRP bars is not a feasible process on construction site. Even though FRP bars can be manufactured in bent shape, they have lower strength at bent location. However, there are no serious problems to use FRP bars as flexural reinforcement. Plates or slabs like bridge decks, in general, do not need shear reinforcements. These types of members with FRP flexural reinforcement have lower shear strength than those with conventional steel flexural reinforcement. However, reliable process or equation for shear strength estimation of FRP reinforced concrete without shear reinforcement are not established, yet. In this study, predicted shear strength obtained from available design equations and assessment equations are compared with 211 experimental results. The results showed that among the current design codes, the Architectural Institute of Japan (AIJ) and the Institution of Structural Engineers (ISE) provided the best estimation. ACI 440.1R-06 provided conservative results with degree of dispersion similar to that of ISE. In addition, regression analysis on the collected experimental results was conducted to develop regression models. As a result, a new reliable shear strength equation was proposed.