| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 104 === The bond characteristics of reinforcing steel bars embedded in concrete matrices play a major role in the behavior of reinforced concrete structural members. Bond refers to the interaction between reinforcing steel and the surrounding concrete that allows for transfer of tensile stress from the steel into the concrete. Composite action between concrete and reinforcing bars cannot occur without bond. The relative rib area is one of important factors of reinforcing bar rib geometry affecting bond strength. ACI committee 408 suggested that value of relative rib area is at least 0.10, but no larger than 0.14, in order to ensure bond behavior of reinforced concrete.
This paper focuses on a basic issue of bond behavior between SD420W deformed rebar with different relative rib area and ordinary/high-strength concrete. It is one of the most important objectives in this study to verify the suitability of a straight development length proposal by ACI 318-14 code, and then establish a proper design model of straight development length between commercial deformed rebar in Taiwan and ordinary/high-strength concrete. In this study, twelve beam specimens were designed and the study parameters of them include bar size, relative rib area, splitting index. The concrete strength were designed as 42 MPa in ordinary-strength concrete and 80 MPa in high-strength concrete. A bond experiment with beam specimens considering combined effects of moment and shear was conducted. Test results indicated that both ordinary- and high-strength concrete neglecting the limitation of 70 MPa of concrete required by ACI 318-14, the straight development lengths based on the equation of the ACI 318-14 were enough to develop corresponding reinforcement strengths for both reinforcements of #8 and #10 whose value of relative rib area equal and large than 0.8. Nevertheless, the upper limitation of concrete strength was 85MPa. In order to ensure bond behavior required by ACI 318-14, the upper limitation of splitting index equal to 2.5 was essential for specimens with deformed rebar.
On the other hand, the study also collected bond tests from international literatures and build data bases, in order to verify accuracy of bond stress prediction models overseas and to build bond stress prediction model for beam test.
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