Continuous and butt-welded specimens of three types of high-yield reinforcing bars have been fatigue tested in bending, in concrete, at a frequency of 3 Hz and to endurances up to 100 x 10 to the 6 cycles. The test results have been compared with those from axial tests, in air, on the same types of bar. The performance of continuous bars tested in bending was higher than that of similar bars tested axially in air, but it is unlikely that the same relationship would exist in all structures. It is suggested, therefore, that the fatigue properties of reinforcement be assessed for design purposes by axial tests in air. It is suggested that all continuous high-yield reinforcement might be included in a single design classification and that the modified relationship be used for all sizes, provided that values of K appropriate to bar diameter were used. The performance of welded bars was reduced by the presence of a weld, but by a smaller amount than in axial tests. The Class C design curve of BS 5400 gave a better estimate of the performance of 16 mm diameter bars than Class D, to which welded reinforcement is assigned, but adoption of the higher classification is not recommended. Fractographic examination indicated that, when tested in concrete, the rib pattern on continuous bars was influential in the positioning of the crack initiation site.(A)

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