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ASTM D7914/D7914M-14

ASTM D7914/D7914M-14

Standard Test Method for Strength of Fiber Reinforced Polymer (FRP) Bent Bars in Bend Locations

Fecha:
2021-02-09 /Historical
Superseeded by:
Significance and Use:

5.1 This test method is intended to determine the bend strength developed at a standard twelve bar diameters of embedment and the strength reduction factors of FRP bent bars that are typically used as anchorages in concrete. From this test, a variety of data are acquired that are needed for design purposes. Material-related factors that influence the tensile response of bars and should therefore be reported include the following: constituent materials, void content, volume percent reinforcement, methods of fabrication, and fiber reinforcement architecture. Similarly, factors relevant to the measured tensile response of bars include specimen preparation, specimen conditioning, environment of testing, specimen alignment, and speed of testing. Properties, in the test direction, that may be obtained from this test method include:

5.1.1 Ultimate bend strength of the FRP bent bar and

5.1.2 Percentage of the guaranteed tensile strength of the straight portion of the bar that is retained in the bend location.

5.2 The results may be used for material specifications, research and development, and structural design and analysis.

Note 1: Two FRP bends are tested simultaneously in this test method, but in some cases only one bend may rupture. While resulting in a valid failure, notice should be taken that only one bend has been effectively measured and that the final compiled test results using this method could differ from those resulting from single FRP bend testing.

Scope:

1.1 This test method determines the quasi-static ultimate strength of fiber reinforced polymer (FRP) composite bent bars commonly used as anchorages for stirrups in reinforced, prestressed, or post-tensioned concrete structures. This test method only applies to bars with a solid cross section.

1.2 FRP bent bars are often used in reinforced concrete applications to shorten the development length of the bar or to act as a tie or a stirrup to resist shear forces. Bent bars can be produced with varying angles of bend in order to fit their intended purpose.

1.3 For this test method, the FRP bars are bent at a 90 degree angle. In general, bars have a regular pattern of surface undulations, a coating of bonded particles, or both, that promote mechanical interlock between the bar and concrete.

1.4 The strength values provided by this method are short-term, quasi-static tensile strengths that do not account for sustained static or cyclic loading. If bars are to be used under high levels of sustained or repeated loading, additional material characterization may be required.

1.5 The characteristic values obtained from this test method are intended to represent the quasi-static ultimate strength of FRP bent bars with a tail length of twelve bar diameters.

1.6 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.

1.6.1 Within the text, the inch-pound units are shown in brackets.

1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Keywords:
bent bar; bend strength; concrete reinforcement; fiber reinforced polymer (FRP); stirrup;
55,24
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