The effect of embedding in concrete on the fatigue performance of steel reinforcement bars is not evident. Some test series provided in literature demonstrate a higher fatigue resistance of embedded bars as compared to bars in air, whereas others provide a lower resistance. In addition, debate exists on the mechanisms behind the difference between tests in air and tests in concrete, if any. These mechanisms mentioned in literature are empirically based. This paper provides a numerical (finite element) study on the stress concentration factors and the stress intensity factors for the two conditions. It shows that the locations of cracks in concrete relative to the ribs on rebars and the distance between concrete cracks have little influence on the stress peaks in the rebar and hence on the fatigue performance of the rebar. Mechanical interlock or pressure of concrete against the ribs slightly contributes to the rebar stress concentrations. No significant difference should be expected in fatigue resistance between rebars in air and rebars embedded in concrete. Variations in local geometry at the root of ribs appear of more significant influence.

埋在混凝土中对钢筋的疲劳性能的影响尚不明显。与空气中的钢筋相比，文献中提供的一些测试系列证明了嵌入钢筋的抗疲劳性更高，而其他试验系列则提供了较低的抗疲劳性。此外，关于空中测试与混凝土测试（如果有）之间差异的背后机制还有争议。文献中提到的这些机制是基于经验的。本文提供了两种条件下应力集中因子和应力强度因子的数值（有限元）研究。结果表明，混凝土中裂缝相对于钢筋肋的位置以及裂缝之间的距离对钢筋的应力峰值影响很小，因此对钢筋的疲劳性能影响很小。机械互锁或混凝土对肋的压力会略微导致钢筋应力集中。空气中的钢筋与埋入混凝土中的钢筋之间的抗疲劳性不应有显着差异。肋骨根部局部几何形状的变化似乎具有更大的影响。