External post-tensioning by means of high-strength steel cables can be used to effectively increase the ultimate capacity of steel-concrete composite beams. Most of the previous fatigue studies are based on the results of push-out tests, and the external post-tensioning, as a strengthening technique, cannot be applied to these types of tests. Therefore, this paper presents fatigue tests on two steel-concrete composite specimens to evaluate the effect of externally post-tensioned tendons on the fatigue behavior of composite beams. Fatigue tests are conducted to a million cycles under a four-point bending test. A numerical model is described to predict the fatigue response of the strengthened beam by considering the fatigue damage in the concrete flange. The accuracy of the developed numerical model is validated using the existing test data. The external post-tensioning significantly decreases strains in the shear connector, concrete flange, and steel beam at all stages of loading.
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